CHAPTER 4 

ENVIRONMENTAL CONSEQUENCES 

ENVIRONMENTAL CONSEQUENCES 

TABLE OF CONTENTS 

Page 

Introduction and Effects ...................................................................................................................................................4-1 

How the Effects of the Alternatives Were Estimated......................................................................................................4-1 

Assumptions for Analysis........................................................................................................................................4-1 

Incomplete and Unavailable Information................................................................................................................4-3 

Subsequent Analysis before Projects.......................................................................................................................4-4 

Program Goals by Ecoregion...................................................................................................................................4-4 

Land Use ...........................................................................................................................................................................4-5 

Air Quality ........................................................................................................................................................................4-5 

Scoping Comments and Other Issues Evaluated in the Assessment ......................................................................4-5 

Emission Sources.....................................................................................................................................................4-6 

Methodology for Assessing Impacts to Air Quality................................................................................................4-6 

Standard Operating Procedures ...............................................................................................................................4-8 

Impacts by Alternative .............................................................................................................................................4-9 

Mitigation for Herbicide Treatment Impacts........................................................................................................ 4-13 

Soil Resources................................................................................................................................................................ 4-13 

Introduction ........................................................................................................................................................... 4-13 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................... 4-13 

Standard Operating Procedures ............................................................................................................................ 4-13 

Factors that Influence the Fate, Transport, and Persistence of Herbicides in Soil.............................................. 4-14 

Impacts by Treatment............................................................................................................................................ 4-15 

Impacts by Alternative .......................................................................................................................................... 4-21 

Mitigation for Herbicide Treatment Impacts........................................................................................................ 4-24 

Water Resources and Quality ........................................................................................................................................ 4-24 

Introduction ........................................................................................................................................................... 4-24 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................... 4-24 

Standard Operating Procedures ............................................................................................................................ 4-24 

Impacts by Treatment............................................................................................................................................ 4-25 

Impacts by Herbicide ............................................................................................................................................ 4-29 

Impacts by Alternative .......................................................................................................................................... 4-34 

Mitigation for Herbicide Treatment Impacts........................................................................................................ 4-36 

Wetland and Riparian Areas.......................................................................................................................................... 4-36 

Introduction ........................................................................................................................................................... 4-36 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................... 4-37 

Factors that Influence the Fate, Transport, and Persistence of Herbicides in Wetland and Riparian Areas...... 4-37 

Methodology for Assessing Impacts to Wetland and Riparian Areas................................................................. 4-37 

Summary of Herbicide Impacts............................................................................................................................ 4-37 

Impacts by Alternative .......................................................................................................................................... 4-41 

Mitigation for Herbicide Treatment Impacts........................................................................................................ 4-44 

Vegetation...................................................................................................................................................................... 4-44 

Introduction ........................................................................................................................................................... 4-44 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................... 4-44 

Standard Operating Procedures ............................................................................................................................ 4-44 

Impacts Assessment Methodology ....................................................................................................................... 4-45 

Impacts Common to All Treatments .................................................................................................................... 4-47 

Summary of Herbicide Impacts Evaluated in ERAs............................................................................................ 4-63 

Other Herbicides Previously Approved for Use on Public Lands....................................................................... 4-64 

Impacts by Alternative .......................................................................................................................................... 4-64 

Mitigation for Herbicide Treatment Impacts........................................................................................................ 4-71 

Special Status Plant Species.................................................................................................................................. 4-71 

Fish and Other Aquatic Organisms............................................................................................................................... 4-76 

BLM Vegetation Treatments Using Herbicides 4-i June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Introduction ........................................................................................................................................................... 4-76 

Scoping Comments and Other Issues Evaluated in the Assessment.................................................................... 4-77 

Standard Operating Procedures............................................................................................................................. 4-77 

Impacts Assessment Methodology ....................................................................................................................... 4-77 

Impacts by Treatment............................................................................................................................................ 4-80 

Impacts by Alternative .......................................................................................................................................... 4-89 

Mitigation for Herbicide Treatment Impacts........................................................................................................ 4-92 

Special Status Fish and Other Aquatic Organisms............................................................................................... 4-92 

Wildlife Resources......................................................................................................................................................... 4-96 

Introduction ........................................................................................................................................................... 4-96 

Scoping Comments and Other Issues Evaluated in the Assessment.................................................................... 4-98 

Standard Operating Procedures............................................................................................................................. 4-98 

Impacts Assessment Methodology ....................................................................................................................... 4-99 

Summary of Herbicide Impacts.......................................................................................................................... 4-101 

Impacts of Herbicide Treatments on Wildlife and Habitat by Ecoregion ......................................................... 4-109 

Impacts by Alternative ........................................................................................................................................ 4-114 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-118 

Special Status Wildlife Species........................................................................................................................... 4-118 

Livestock...................................................................................................................................................................... 4-124 

Introduction ......................................................................................................................................................... 4-124 

Scoping Comments and Other Issues Evaluated in the Assessment.................................................................. 4-124 

Standard Operating Procedures........................................................................................................................... 4-124 

Impacts Assessment Methodology ..................................................................................................................... 4-125 

Summary of Herbicide Impacts.......................................................................................................................... 4-125 

Impacts by Alternative ........................................................................................................................................ 4-133 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-136 

Wild Horses and Burros............................................................................................................................................... 4-136 

Introduction ......................................................................................................................................................... 4-136 

Scoping Comments and Other Issues Evaluated in the Assessment.................................................................. 4-137 

Standard Operating Procedures........................................................................................................................... 4-137 

Impacts Assessment Methodology ..................................................................................................................... 4-137 

Summary of Herbicide Impacts.......................................................................................................................... 4-137 

Impacts by Alternative ........................................................................................................................................ 4-143 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-146 

Paleontological and Cultural Resources...................................................................................................................... 4-146 

Scoping Comments and Other Issues Evaluated in the Assessment.................................................................. 4-147 

Standard Operating Procedures for Addressing BLM Actions on Paleontological, Cultural, and Subsistence 

Resources............................................................................................................................................................. 4-147 

Herbicide Impacts on Paleontological and Cultural Resources......................................................................... 4-148 

Herbicide Impacts on Native American Health.................................................................................................. 4-149 

Impacts by Alternative ........................................................................................................................................ 4-150 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-152 

Visual Resources.......................................................................................................................................................... 4-152 

Scoping Comments and Other Issues Evaluated in the Assessment.................................................................. 4-153 

Standard Operating Procedures........................................................................................................................... 4-153 

BLM Assessment of Visual Resource Values.................................................................................................... 4-153 

Summary of Herbicide Impacts.......................................................................................................................... 4-154 

Impacts by Alternative ........................................................................................................................................ 4-154 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-155 

Wilderness and Special Areas..................................................................................................................................... 4-155 

Scoping Comments and Other Issues Addressed in the Assessment................................................................. 4-156 

Standard Operating Procedures........................................................................................................................... 4-156 

Summary of Herbicide Impacts.......................................................................................................................... 4-156 

BLM Vegetation Treatments Using Herbicides 4-ii June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES 

Impacts by Alternative ........................................................................................................................................ 4-157 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-159 

Recreation .................................................................................................................................................................... 4-159 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................. 4-159 

Standard Operating Procedures .......................................................................................................................... 4-160 

Summary of Herbicide Impacts.......................................................................................................................... 4-160 

Impacts by Alternative ........................................................................................................................................ 4-161 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-163 

Social and Economic Values....................................................................................................................................... 4-163 

Introduction ......................................................................................................................................................... 4-163 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................. 4-164 

Standard Operating Procedures .......................................................................................................................... 4-164 

Impact Assessment Assumptions ....................................................................................................................... 4-165 

Summary of Herbicide Impacts.......................................................................................................................... 4-165 

Impacts by Alternative ........................................................................................................................................ 4-166 

Mitigation for Herbicide Treatment Impacts...................................................................................................... 4-174 

Human Health and Safety............................................................................................................................................ 4-174 

Scoping Comments and Other Issues Evaluated in the Assessment ................................................................. 4-175 

Standard Operating Procedures .......................................................................................................................... 4-175 

Human Health Risk Assessment Methodology.................................................................................................. 4-175 

Uncertainty in the Risk Assessment Process...................................................................................................... 4-181 

Impacts by Alternative ........................................................................................................................................ 4-195 

Mitigation ............................................................................................................................................................ 4-196 

Cumulative Effects Analysis....................................................................................................................................... 4-197 

Structure of the Cumulative Effects Analysis.................................................................................................... 4-197 

Resource Protection Measures Considered in the Cumulative Effects Analysis.............................................. 4-201 

Other Information Considered in Cumulative Effects Analysis........................................................................ 4-202 

Analysis of Cumulative Effects by Resources................................................................................................... 4-202 

Unavoidable Adverse Effects ............................................................................................................................. 4-243 

Relationship between the Local Short-term Uses and Maintenance and Enhancement of Long-term

Productivity ......................................................................................................................................................... 4-246 

Irreversible and Irretrievable Commitment of Resources.................................................................................. 4-251 

Energy Requirements and Conservation Potential............................................................................................. 4-253 

Natural or Depletable Resource Requirements and Conservation..................................................................... 4-253 

BLM Vegetation Treatments Using Herbicides 4-iii June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

List of Tables 

4-1 Estimated Acres Treated Annually using Herbicides for Each State under Each Treatment 

Alternative ......................................................................................................................................................... 4-7 

4-2 Annual Emissions Summary for Herbicide Treatments under Alternative A ................................................. 4-8 

4-3 Annual Emissions Summary for Herbicide Treatments under Alternative B.................................................. 4-9 

4-4 Annual Emissions Summary for Herbicide Treatments under Alternative D ............................................... 4-10 

4-5 Annual Emissions Summary for Herbicide Treatments under Alternative E................................................ 4-11 

4-6 Example NAAQS Compliance Analysis for Chemical Treatment................................................................ 4-12 

4-7 Estimated Soil Half-life and Adsorption Affinity for Active Ingredients...................................................... 4-15 

4-8 Factors Associated with Herbicide Movement to Groundwater.................................................................... 4-27 

4-9 Herbicide Physical Properties and Off-site Movement Potential................................................................... 4-28 

4-10 Anaerobic Half-life and Relative Mobility in Soil for Herbicides Analyzed in this PEIS............................ 4-39 

4-11 Risk Categories Used to Describe Typical Herbicide Effects to Vegetation According to Exposure 

Scenario and Ecological Receptor Group....................................................................................................... 4-49 

4-12 Buffer Distances to Minimize Risk to Vegetation from Off-site Drift of BLM-evaluated Herbicides ........ 4-54 

4-13 Risk Categories Used to Describe Effects of Forest Service-evaluated Herbicides According to 

Exposure Scenario and Ecological Receptor Group....................................................................................... 4-57 

4-14 Buffer Distances to Minimize Risk to Vegetation from Off-site Drift of Forest Service-evaluated 

Herbicides........................................................................................................................................................ 4-61 

4-15 Percentage of Acres Projected to be Treated Using Herbicides in Each Ecoregion for Each 

Vegetation Subclass under the No Action Alternative................................................................................... 4-67 

4-16 Percentage of Acres Projected to be Treated Using Herbicides in Each Ecoregion for Each 

Vegetation Subclass under the Preferred Alternative..................................................................................... 4-69 

4-17 Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Non Special Status Fish and 

Aquatic Invertebrates According to Exposure Scenario................................................................................. 4-81 

4-18 Risk Categories Used to Describe Forest Service-evaluated Herbicide Effects on Fish and Aquatic 

Invertebrates According to Exposure Scenario .............................................................................................. 4-87 

4-19 Buffer Distances to Minimize Risk to Non Special Status Fish and Aquatic Invertebrates from Offsite Drift of BLM-evaluated Herbicides from Broadcast and Aerial Treatments.......................................... 4-93 

4-20 Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Special Status Fish and 

Aquatic Invertebrates According to Exposure Scenario................................................................................. 4-97 

4-21 Buffer Distances to Minimize Risk to Special Status Fish and Aquatic Organisms from Off-site Drift 

of BLM Herbicides from Broadcast and Aerial Treatments.......................................................................... 4-98 

4-22 Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Non Special Status Wildlife 

According to Exposure Scenario................................................................................................................... 4-103 

4-23 Risk Categories Used to Describe Forest Service-evaluated Herbicide Effects on Wildlife According 

to Exposure Scenario..................................................................................................................................... 4-107 

4-24 Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Special Status Wildlife 

According to Exposure Scenario................................................................................................................... 4-121 

4-25 Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Livestock and Wild Horses 

and Burros According to Exposure Scenario................................................................................................ 4-127 

4-26 Risk Categories Used to Describe Forest Service-evaluated Herbicide Effects on Livestock and Wild 

Horses and Burros According to Exposure Scenario ................................................................................... 4-131 

4-27 BLM-evaluated Herbicide Risk Categories by Aggregate Risk Index for Occupational Receptors.......... 4-185 

4-28 BLM-evaluated Herbicide Risk Categories by Aggregate Risk Index for Public Receptors..................... 4-186 

4-29 Forest Service-evaluated Herbicide Risk Categories by Hazard Quotient for Occupational Receptors..... 4-187 

4-30 Forest Service-evaluated Herbicide Risk Categories by Hazard Quotient for Public Exposures............... 4-188 

4-31 Scenarios Resulting in High Risk to Occupational Receptors from Herbicides Evaluated in the 1988-

1991 BLM EISs............................................................................................................................................. 4-191 

4-32 Scenarios Resulting in High Risk to Public Receptors from Herbicides Evaluated in the 1988-1991 

BLM EISs...................................................................................................................................................... 4-192 

4-33 Herbicide Use in the Western United States for Agricultural Lands and BLM-administered Lands......... 4-200 

BLM Vegetation Treatments Using Herbicides 4-iv June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES 

CHAPTER 4 

ENVIRONMENTAL CONSEQUENCES

Introduction and Effects 

This chapter examines how vegetation treatment 

activities may affect natural, cultural, and 

socioeconomic resources on public lands. The focus of 

the analysis is on alternative proposals for treating 

public lands using herbicides. A summary of impacts 

associated with the use of other treatment methods is

included in the Vegetation Treatments on Bureau of

Land Management Lands in 17 Western States PER

(USDI BLM 2007a). 

How the Effects of the 

Alternatives Were Estimated 

Within each resource area, applicable direct and indirect 

effects are evaluated. Cumulative effects, unavoidable 

adverse effects, and resource commitments that are lost

or cannot be reversed are identified for all treatment

activities in the PEIS. These impacts are defined as 

follows: 

• Direct effects – Those effects that are caused 

by the action and occur at the same time and in 

the same general location as the action. 

• Indirect effects – Those effects that occur at a

different time or in a different location than the

action to which the effects are related. 

• Cumulative effects – Those effects that result

from the incremental impact of the action when 

it is added to other past, present, and

reasonably foreseeable future actions.

Cumulative effects can result from individually 

minor but collectively significant actions taking 

place over a period of time. For this PEIS,

potential cumulative effects include those that 

could occur on other federal and non-federal

lands. 

• Unavoidable adverse commitments – Those 

effects that could occur as a result of 

implementing any of the action alternatives.

Some of these effects would be short term, 

while others would be long term. 

• Irreversible commitments – Those 

commitments that cannot be reversed, except 

perhaps in the extreme long term. This term 

applies primarily to the effects of use of 

nonrenewable resources, such as minerals or

cultural resources, or to factors, such as soil

productivity, that are renewable only over long 

periods of time. 

• Irretrievable commitments – Those 

commitments that are lost for a period of time. 

For example, timber production is lost while

an area is mined. The production lost is

irretrievable, but the action is not irreversible. 

If the site is reclaimed, it is possible to resume

timber production. 

In addition, the PEIS considers the interaction of 

effects, as follows: 

• “Additive” – total loss of sensitive resources 

from more than one incident.

• “Countervailing” – negative effects are 

compensated for by beneficial effects. 

• “Synergistic” – total effect is greater than the

sum of the effects taken independently. 

This chapter should be read together with Chapter 2

(Alternatives), which explains the alternative proposals 

the BLM is considering for treating vegetation using

herbicides, and Chapter 3 (Affected Environment),

which describes the important resources and their 

occurrence and status on public lands. The analyses of

environmental consequences in this chapter build upon 

and relate to information presented in these earlier 

chapters to identify which resources may be impacted 

and how and where impacts might occur. 

Assumptions for Analysis 

This analysis addresses large, regional-scale trends and 

issues that require integrated management across broad

landscapes. It also addresses regional-scale trends and

changes in the social and economic needs of people. 

This analysis does not identify site-specific effects 

because site-specific information is not essential for 

BLM Vegetation Treatments Using Herbicides 4-1 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

determining broad-scale management direction. As

discussed in Chapter 1, Proposed Action and Purpose 

and Need, site-specific issues would be addressed

through NEPA compliance for resource management 

activities and other land use plans prepared at the state, 

district, or field office level. 

Vegetation treatments are proposed, designed, and 

implemented within a natural resource management

context that assumes certain conditions exist or are met.

They are implemented with consideration for the larger 

vegetation management context in which they occur. 

For example, if a target vegetation type is treated and 

removed, the BLM first considers how the area will be

revegetated or stabilized to ensure the long-term 

viability of the project area. The BLM does not leave

bare ground at treatment sites that would allow weeds 

and invasive species to increase in abundance, which

would negate the treatment effort. Treated vegetation is 

removed from the site if it poses a further risk as

hazardous fuel. 

Certain assumptions about treatments have been made 

in this PEIS. The analysis of impacts presented in 

Chapter 4 assumes that vegetation treatments would be 

developed and applied in an IPM context, and that the

tool(s) identified for the treatment would be the 

appropriate means to achieve the project objective. The

analysis assumes that post-treatment follow-up such as

re-seeding and monitoring would occur, as required

under most BLM vegetation programs including

Emergency Stabilization (ES) and Burned Area 

Rehabilitation (BAR). The analysis assumes that

maintenance of past treatments has occurred, and that

the BLM would make an investment in maintaining the

condition achieved or objectives of the project, rather 

than implementing stand-alone, one-time treatments. 

The analysis also assumes that the BLM would

determine the need for the action based on past 

monitoring, and that additional monitoring would occur 

after the project to ascertain its effectiveness in 

achieving the resource objective. 

The analysis of impacts assumes that SOPs would be

followed by the BLM under all alternatives to ensure 

that risks to human health and the environment from

herbicide treatment actions would be kept to a minimum 

(see Table 2-8). Examples of SOPs that pertain to all

resource areas include the following: 

• Prepare a spill contingency plan in advance of 

treatment. 

• Conduct a pre-treatment survey. 

• Identify the most appropriate treatment

method. If chemicals are the appropriate 

treatment, then select the chemical that is least

damaging to the environment while providing 

the desired results. 

• Review, understand, and conform to the 

“Environmental Hazards” section on the 

herbicide label. This section warns of known

pesticide risks to the environment and provides 

practical ways to avoid harm to organisms or

the environment. 

• Consider surrounding land uses before 

selecting aerial spraying as a treatment method. 

• Notify adjacent landowners prior to treatment. 

• Apply the least amount of herbicide needed to 

achieve the desired results. 

• Follow the product label for use and storage. 

• Have licensed applicators apply herbicides. 

• Use only USEPA-approved herbicides, and 

follow product label directions and “advisory” 

statements. 

• Keep a copy of Material Safety Data Sheets 

(MSDSs) at work sites. 

• Keep records of each application. 

• Avoid accidental direct spray and spill

conditions to minimize risks to resources. 

• Avoid aerial spraying during periods of adverse 

weather conditions. 

• Make helicopter applications at a target

airspeed of 40 to 50 mph, and at about 30 to 45

feet above ground. 

Additional SOPs specific to individual resources have 

been provided in the impacts analysis section for each

resource, as well as in Table 2-8. 

The analysis assumes that the BLM would comply with

federal, state, tribal, and local regulations that govern 

activities on public lands. In addition, mitigation 

measures have been identified for most resource areas 

that could apply to one or more alternatives to further 

reduce impacts associated with herbicide treatments. 

BLM Vegetation Treatments Using Herbicides 4-2 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

Incomplete and Unavailable 

Information 

According to the Council on Environmental Quality

regulations for implementing the procedural provisions 

of NEPA (40 CFR 1502.22), if the information is

essential to a reasoned choice among alternatives and 

the cost of gathering it is not excessive, it must be

included or addressed in the PEIS. 

Knowledge is, and always will be, incomplete regarding 

many aspects of terrestrial and aquatic species, 

forestland, rangelands, the economy, and society.

However, central ecological, economic, and social

relationships are well established, and a substantial 

amount of credible information about ecosystems in the 

project area is known. The alternatives were evaluated 

using the best available information. 

As noted in Chapter 1, the primary issue of controversy 

identified through scoping, and which required NEPA 

review, was the BLM’s continuing use of herbicides 

and proposed increase in herbicide use in vegetation 

treatment programs needed to implement the National

Fire Plan and related initiatives. The use of herbicides 

has been affirmed as a central issue for analysis in all

past EISs considered in this document. 

To address issues related to the use of herbicides, the

BLM prepared human health and ecological risk

assessments for 10 herbicides/formulations currentlyavailable to the BLM (bromacil, chlorsulfuron, diuron, 

sulfometuron methyl, and tebuthiuron), or proposed for 

future use (diflufenzopyr, diquat, fluridone, imazapic, 

and Overdrive

® [diflufenzopyr in a formulation with

dicamba]). The BLM also consulted risk assessments 

prepared by the Forest Service for nine other herbicides 

used by the BLM (2,4-D, clopyralid, dicamba, 

glyphosate, hexazinone, imazapyr, metsulfuron methyl, 

picloram, and triclopyr). For the remaining six 

herbicides (2,4-DP, asulam, atrazine, fosamine, 

mefluidide, and simazine), the BLM consulted earlier 

EISs prepared by the BLM, and the literature developed 

since 1991, to evaluate risks. These six herbicides 

would not be used by the BLM under the Preferred 

Alternative and Alternatives D and E, but could be used

if the No Action Alternative was selected. 

Risk assessments were developed in cooperation with

the USEPA, USFWS, and NMFS, and are considered

state-of-the-science. As such, they address many of the

risks that would be faced by humans, plants, and 

animals, including special status species, from the use of

the herbicides, and supercede risk assessments prepared

by the BLM for the previous vegetation treatment EISs. 

To assess risks to other resources from the use of

herbicides, the BLM consulted information in the risk 

assessments and supporting documentation (see 

appendixes B, C, and D and supporting Human Health

and Ecological Risk Assessment reports); state, federal, 

and local databases, Geographic Information System 

(GIS) themes, and contract reports; subject experts 

within and outside of the BLM; and the current

literature. 

A programmatic analysis over a 17-state area generally 

summarizes information that may be available at finer 

scales (e.g. at the regional and local level), but is too decentralized and dispersed to be presented effectively.

For example, although information pertaining to

monitoring land use plan management activities over 

the last 20 or more years may be available at local BLM

offices, it would take many years to summarize the

conclusions contained in this vast amount of 

information for this PEIS, and the cost would be 

exorbitant. The BLM is currently undertaking a

National Monitoring Initiative with an objective of 

bringing together a wide range of monitoring data into a

central clearinghouse. This project has only recently 

become feasible due to the advancements of GIS and

internet technology. The National Monitoring Initiative

has been funded in the last 2 fiscal years, and is 

expected to take many years to complete. 

The specific locations of all past treatment projects are

not available for discussion in this PEIS. To date, the 

BLM has not developed a central clearinghouse of GIS 

data identifying the locations of all past projects that

have occurred on public lands. These data are available 

in local field office GIS databases, maps, or project

files. Locations of future projects are also unknown, as 

they will be determined later in time and are not 

necessarily identified at this time; for this PEIS analysis, 

these locations have been estimated. Local site-specific

land use plans and activity plans will identify the 

priorities of each field office. The appropriate mix of 

treatments and their location is addressed at the 

Resource Management Planning (RMP) level. 

This PEIS identifies human health and ecological risks 

associated with USEPA-registered herbicide active

ingredients, as well as inerts and degradates for which

information is available and not constrained by 

confidential business information (CBI) restrictions. 

Preparing a risk assessment for every conceivable 

combination of herbicide, tank mix, surfactant,

BLM Vegetation Treatments Using Herbicides 4-3 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

adjuvant, and other possible mixture is not feasible, as 

the BLM cannot prepare hundreds of risk assessments, 

and the cost would be exorbitant. To the degree a toxic 

substance is known to pose a significant human or

ecological risk, the BLM has undertaken the necessary 

analysis to assess its impacts through risk assessments. 

One resource area for which information is incomplete

or unavailable is social and economic values. Although 

supply and labor costs related to vegetation treatments 

are likely to be available at the local or county level, 

they are not quantifiable over a 17-state area. The

social and economic costs of invasive and noxious

weeds are only now being understood and quantified by 

economists and vegetation scientists at local and 

regional scales. At the national scale, however,

quantification of these costs is not possible beyond 

identifying basic trends, given the variety of economic, 

social and environmental factors involved in estimating

these effects. As identified below, this PEIS assumes 

that locally available data would be consulted when

proposing and assessing impacts under NEPA for sitespecific projects at the local level. 

While additional information may add precision to

estimates or better specify relationships, new or

additional information is unlikely to significantly 

change the understanding of the relationships that form

the basis of the effects analysis presented in this chapter. 

Subsequent Analysis before Projects 

Before site-specific actions are implemented and an 

irreversible commitment of resources made, information

essential to those fine-scale decisions will be obtained 

by the local land managers. Localized data and

information will be used to supplement or refine

regional-level data and identify methods and procedures 

best suited to local conditions in order to achieve the 

objectives in this PEIS. Further analysis may be

necessary to deal with site-specific conditions and 

processes. For example, mitigation measures identified

in the following sections would be appropriate for 

protecting resources under the wide range of conditions

that must be considered at the programmatic level of 

analysis. However, by considering more site-specific 

parameters, such as soil and vegetation type and amount

of rainfall, the BLM may be able to use less restrictive

mitigation measures and still ensure adequate protection 

of the resource; the possibility that more restrictive 

measures would be necessary could also occur. This 

subsequent analysis will be used to bridge the gap 

between broad-scale direction and site-specific 

decisions. This “step-down” analysis is described in

Chapter 1 and shown in Figure 1-1. 

Program Goals by Ecoregion 

The goals of chemical vegetation treatments, by 

ecoregion where treatments are planned, are discussed

below. 

Temperate Desert Ecoregion 

Over 70% of herbicide treatments would occur on BLM 

land in the Temperate Desert Ecoregion. Most of these 

treatments would be used to meet vegetation and

integrated weed management (IWM) objectives (33% 

of treatments), reduce hazardous fuels (25%), conduct

ES and BAR activities (19%), and improve rangeland 

health (12%). Improvements of wildlife habitat and 

watershed health are objectives of lesser importance

(6% and 5% of treatments, respectively) in this 

ecoregion. 

Temperate Steppe Ecoregion 

In the Temperate Steppe Ecoregion, most herbicide 

treatments would be conducted to meet IVM and/or

IWM objectives (62% of treatments). Other important

objectives include hazardous fuels reduction (25%) and

improvement of rangeland health (11%). 

Subtropical Steppe Ecoregion 

On BLM lands in the Subtropical Steppe Ecoregion, 

herbicide treatments would be used to improve habitat 

(38% of treatments), improve rangeland health (21%), 

reduce hazardous fuels (17%), and meet IVM and/or 

IWM objectives (11%). 

Mediterranean Ecoregion 

In the Mediterranean Ecoregion, chemical treatments 

would be conducted primarily to improve forest health 

(35% of treatments), and to meet maintenance-related

(28%) and IVM and/or IWM (20%) objectives. 

Improvement of rangeland health (9%) and recreation

areas (6%) would also be important objectives. 

Marine Ecoregion 

On BLM lands in the Marine Ecoregion, the majority of 

herbicide treatments would be conducted to meet IVM

and/or IWM (69%) and maintenance-related (22%) 

objectives. Some less important treatment objectives

include maintaining ROW (3%), improving forest

BLM Vegetation Treatments Using Herbicides 4-4 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

health (3%), and improving habitat for native vegetation

(3%). 

Land Use 

As discussed in Chapter 1, several federal laws,

regulations, and policies guide BLM management 

activities on public lands. These include the FLPMA of

1976, which directs the BLM to manage public lands

“in a manner that will protect the quality of scientific, 

scenic, historic, ecological, environmental, air and 

atmospheric, water resources and archeological values” 

and to develop resource management plans consistent

with those of state and local governments to the extent 

that BLM programs also comply with federal laws and

regulations. The Taylor Grazing Act of 1934 provides 

federal protection and management of public lands by 

regulating grazing on public lands. The Oregon and

California Grant Lands Act of 1937 provides for the 

management of the revested Oregon and California and 

reconveyed Coos Bay Wagon Road grant lands for 

permanent forest production under the principle of 

sustained yield and for leasing of lands for grazing. 

Management actions on public lands are guided by

LUPs. Land use plan decisions establish goals and

objectives for resource management, the measures 

needed to achieve these goals and objectives, and 

parameters for using public lands (USDI BLM 2000g). 

As discussed in Chapter 1, land use planning occurs at 

several levels. Planning at multiple levels allows the

BLM to tailor decisions to specific needs and

circumstances. The broadest level, which this PEIS 

represents, is a national-level programmatic study. This 

level of study contains broad regional descriptions of

resources, provides a broad environmental impact

analysis, including cumulative impacts, focuses on 

general policies, and provides Bureau-wide decisions on

herbicide use and other available tools for vegetation 

management. Additionally, it provides an umbrella ESA 

Section 7 consultation for the broad range of activities 

described in the PEIS. 

At the national level, this PEIS and the PER identify 

broad management goals and evaluate resource issues 

of national interest. This PEIS assumes that vegetation 

treatments could occur on up to approximately 6 million

acres annually, that treatments would focus on areas 

with high levels of hazardous fuels and unwanted 

vegetation, that land uses would comply with the intent 

of Congress as stated in the FLPMA (43 U.S.C. 1701 et 

seq.), and that future land uses would be similar to those 

that currently occur on public lands. Based on these 

evaluations, modifications to existing land uses could

occur at lower levels, primarily the field office level, 

based on recommendations in the PEIS and PER. 

Air Quality 

Air quality is the measure of the atmospheric 

concentration of defined pollutants in a specific area. 

Air quality is affected by pollutant emission sources, as 

well as the movement of pollutants in the air via wind

and other weather patterns. Air quality standards have 

been designated in the U.S. to prevent significant 

human health and welfare impacts caused by pollutants 

in the air. The Clean Air Act, as amended in 1990,

establishes a mandate to reduce emissions of specific 

pollutants via uniform federal standards. As the agency 

responsible for implementing the Act, the USEPA 

established the NAAQS for six pollutants to protect

public health and welfare. These criteria pollutants are 

SO2, NO2, CO, O3, lead, PM10, and PM2.5. In addition, 

PSD regulations, implemented as part of the New 

Source Review program, guide permitting officials in

limiting potential air quality impacts above legally

defined baseline levels (USEPA 2004). In essence, 

established facilities with new major pollutant sources 

that were previously in attainment of the NAAQS (or 

were unclassifiable with respect to these standards) are 

still considered to have acceptable emissions levels if 

the potential cumulative impacts do not exceed these 

guideline PSD significance levels. Prevention of 

Significant Deterioration levels are used in this analysis 

as criteria to indicate whether the herbicide use

alternatives would significantly affect air quality. 

The majority of the area covered by this PEIS meets 

existing air quality standards; however, there are many

counties (or portions of counties) where air pollutants 

exceed maximum levels of one or more of the NAAQS 

(see Table 3-3). In addition, the Clean Air Act stipulates 

that the air quality of most areas should not significantly 

deteriorate. Therefore, this PEIS considers the

contribution of proposed herbicide treatment 

alternatives to levels of the abovementioned criteria 

pollutants. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

In line with scoping comments, this section assesses the

effects of herbicide treatments on air pollutants and 

consequent effects on visibility and NAAQS. Most

scoping comments were related to the impacts of smoke 

BLM Vegetation Treatments Using Herbicides 4-5 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

from prescribed burning treatments on air quality. 

Specifically, comments called for an evaluation of the

cumulative effects of smoke and an evaluation of the

human health effects of smoke, particularly on

asthmatics and in non-attainment zones (areas with

levels of one or more criteria pollutants greater than the

NAAQS). The impacts of prescribed burning on air 

quality are discussed in the PER (USDI BLM 2007b). 

Emission Sources 

The potential impacts of herbicide use on air quality 

originate primarily from ground vehicle (truck, allterrain vehicle [ATV], and boat) and aircraft (plane and 

helicopter) emissions, as well as fugitive dust (dust 

created by vehicle travel on unpaved roads) resulting 

from herbicide transport and application. In addition, 

spray drift (movement of herbicide in the air to 

unintended locations) and volatilization (the evaporation 

of liquid to gas) of applied herbicides temporarily 

results in herbicide particles in the air, which can be

inhaled and deposited on skin or plant surfaces and 

affect humans, wildlife, and non-target plants. Herbicide 

particles can be transported away from the target

location, depending on weather conditions and the 

herbicide application method. Spray drift and other offsite herbicide transport processes (e.g., wind blown

dust) are discussed briefly in this section and more 

specifically in the sections pertaining to risks to

humans, wildlife, non-target plants, and other resources. 

Methodology for Assessing Impacts to 

Air Quality 

Vehicle Use Emissions 

This analysis includes annual emissions for the 

proposed alternatives and treatments by state for the 

following compounds: CO, total suspended particles 

(TSP), PM10, PM2.5, NO2, and VOCs. Lead and SO2

emissions should not occur, or occur in trace amounts, 

as a result of herbicide treatments involving vehicles 

and aircraft. 

Exhaust emission factors were determined using vehicle 

data provided by the USDI BLM and the USEPA’s 

Compilation of Air Pollutant Emission Factors (USEPA 

1995a). Emission factors for fugitive dust from roads 

(assumed to be unpaved) were determined from trip

mileage and soil properties provided by the BLM and

the USEPA’s Compilation of Air Pollutant Emission 

Factors (USEPA 2003a). All other emissions that would

be associated with herbicide treatments would be 

negligible, and are therefore not included in the annual

emissions computations for each treatment alternative. 

The potential annual emissions that would result from

herbicide treatment within each state were based on an

estimate of the annual acreage that would be treated by

each of the five herbicide treatment methods (helicopter, 

fixed-wing plane, truck, ATV, and backpack) for each

state for each alternative action (Table 4-1). To 

calculate the annual number of events for each

treatment method by state, the estimated annual number 

of acres treated was divided by the total acreage per 

single treatment event. The annual air pollutant 

emissions from herbicide treatments for each state were

then predicted based on emissions per treatment event. 

Exhaust Emi sions from Transportation

Vehicle

s

s

t

To predict the annual vehicle emissions from each 

treatment method, the exhaust emissions for a single 

event were multiplied by the annual number of events

per state for each method. The amount of pollutant

emissions due to exhaust from transportation vehicles 

was calculated using the procedures (e.g., regarding trip 

mileage, vehicle type) described in the Annual

Emissions Inventory for BLM Vegetation Treatment

Alternatives (ENSR 2005a). 

Particula e Emissions from Unpaved Roads 

To predict the particulate emissions from travel on

unpaved roads, the emissions for a single event were 

multiplied by the annual number of events per state for 

each treatment method. The amount of pollutant

emissions due to exhaust from unpaved roads and

vehicles was calculated using the procedures described

in ENSR (2005a). 

 Total Annual Chemical Treatment Emissions 

The annual pollutant emissions from vehicle exhaust

and fugitive dust were combined for each treatment

method. The resulting annual emissions for each

method were then summed, yielding the total predicted

emission by state and alternative (Tables 4-2 to 4-5).

Because the proposed acreage to be treated by state and

alternative is subject to change, so are the estimated

annual emissions, as they are directly dependent on the

number of acres treated. The total estimated emissions 

were then compared to the PSD emission source

modeling threshold significance level. Under the PSD

BLM Vegetation Treatments Using Herbicides 4-6 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

TABLE 4-1

Estimated Acres Treated Annually using Herbicides in Each State under Each Treatment Alternative 

Treatment Alternative State A B C D E

Alaska 0 0 0 0 0 

Arizona 9,960 36,300 0 23,595 18,150 

California 5,060 5,620 0 3,935 2,810 

Colorado 7,770 20,960 0 13,625 10,480 

Idaho 57,100 258,990 0 168,345 129,480 

Montana 23,190 53,160 0 34,555 26,580 

Nebraska 0 0 0 0 0 

Nevada 24,970 206,560 0 82,625 103,270

New Mexico 96,620 88,600 0 35,440 44,295 

North Dakota 10 10 0 10 5 

Oklahoma 0 0 0 0 0 

Oregon (Total) 20,960 70,280 0 26,000 35,135 

 Eastern 8,380 28,110 0 10,400 14,055 

 Western 12,570 42,170 0 15,600 21,080 

South Dakota 1,030 1,600 0 640 800 

Texas 0 11,830 0 7,100 5,915 

Utah 21,660 20,480 0 15,360 10,240 

Washington 1,940 4,640 0 3,015 2,320 

Wyoming 35,130 152,820 0 114,615 76,400 

Total 305,400 931,850 0 528,860 465,880

program, if potential emissions for a given source and 

pollutant are less than the designated PSD level of 250

tons per year, it is assumed that these emissions are

unlikely to significantly impact air quality. This is a

conservative assumption, given that PSD levels are

designed to apply to a single facility or a group of 

facilities, whereas the total predicted pollutant

emissions presented here would be spread throughout

an entire state or region. 

CALPUFF Modeling 

The USEPA’s guideline California Puff (CALPUFF) 

“lite” air pollutant dispersion model (referenced in 

Appendix W of 40 CFR Part 51) was used to provide an 

example of potential PM (TSP, PM10, and PM2.5) 

impacts resulting from assumed herbicide application 

methods. Since most criteria pollutant emissions were 

very low, only example PM impacts were modeled. The 

total fugitive dust particulate emissions per truck

spraying event (10 acres sprayed over 8 hours) were 

used to estimate maximum daily emission rates in the

CALPUFF modeling analysis. Because vehicles 

traveling on unpaved roads emit the most PM (dust), 

and the truck spray scenario includes the most travel on

dirt roads, this scenario was conservatively used to

model the maximum potential impacts. Activities 

related to airplane and helicopter aerial spraying, ATV 

spraying, and backpack spraying would cause 

substantially fewer PM emissions than truck spraying, 

and therefore are not included in the example modeling. 

Chemical treatment example modeling was conducted 

for five representative locations: Tucson International 

Airport (Arizona), Glasgow International Airport

(Montana), Winnemucca Weather Service Office

Airport (Nevada), Medford/Jackson County Airport

(Oregon), and Lander/Hunt Field (Wyoming). 

Total PM emissions were calculated for each treatment

“event,” and then divided by the number of days per 

event in order to determine daily TSP, PM10, and PM2.5

emissions. The daily emissions were modeled using

CALPUFF “lite” based on a full year of meteorological

conditions to predict the maximum air quality impacts 

likely to occur. The maximum potential impact period

was defined as those consecutive days (excluding 

months when treatment activity is unlikely) during

which the highest short-term impacts were predicted to

occur. Once the period of maximum potential impact

was established, CALPUFF “lite” was re-run, with daily 

emissions occurring only during that period, to

determine both short-term and annual impacts 

(assuming one herbicide treatment event in each

location per year). Because only one event was modeled

per year, the results are provided as an example of the 

BLM Vegetation Treatments Using Herbicides 4-7 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-2 

Annual Emissions Summary for Herbicide Treatments under Alternative A 

Pollutant (tons per year) State CO NOX TSP PM10 PM2.5 VOCs 

Alaska 0.00 0.00 0.00 0.00 0.00 0.00

Arizona 0.93 0.11 4.02 0.85 0.12 0.07

California 0.49 0.06 2.14 0.45 0.06 0.03

Colorado 0.76 0.09 1.81 0.40 0.05 0.07

Idaho 5.34 0.64 13.30 2.91 0.37 0.38

Montana 2.17 0.26 5.05 1.13 0.14 0.15

Nebraska 0.00 0.00 0.00 0.00 0.00 0.00

Nevada 1.31 0.15 5.76 1.23 0.17 0.09

New Mexico 5.29 0.59 19.33 4.33 0.59 0.44 

North Dakota 0.00 0.00 0.00 0.00 0.00 0.00 

Oklahoma 0.00 0.00 0.00 0.00 0.00 0.00

Oregon (Total) 1.97 0.22 10.37 2.47 0.35 0.14 

 Eastern 0.81 0.10 2.55 0.56 0.07 0.06

 Western 1.15 0.13 7.82 1.91 0.27 0.08

South Dakota 0.05 0.01 0.13 0.03 0.01 0.00 

Texas 0.00 0.00 0.00 0.00 0.00 0.00

Utah 2.57 0.30 9.05 1.99 0.27 0.22

Washington 0.18 0.02 0.42 0.09 0.01 0.01

Wyoming 2.57 0.30 6.02 1.31 0.17 0.22 

Total 23.63 2.75 77.40 17.19 2.31 1.82

maximum emission concentrations resulting from a 

single annual herbicide treatment event. 

Comparison to Air Quality Standards 

The short-term air quality impacts, as predicted using 

CALPUFF “lite,” were compared to the applicable 

NAAQS as a threshold of significance (Table 4-6).

Potential direct air quality impacts for TSP, PM10, and 

PM2.5 predicted using CALPUFF “lite” were added to a 

representative rural background concentration, and then

compared to the NAAQS to determine if the example 

treatment method scenarios would be likely to exceed

any NAAQS due to a single herbicide spraying event. 

No such exceedances of the applicable threshold values

were predicted. 

Spray Drift and Volatilization 

Spray drift from various herbicide application methods 

was assessed using the model AgDRIFT® Version

2.0.05 (SDTF 2002), a product of a Cooperative 

Research and Development Agreement between the

USEPA’s Office of Research and Development and the 

Spray Drift Task Force (SDTF, a coalition of pesticide

registrants). Maximum herbicide concentrations by 

particle size were predicted at increasing distances from 

the point of application 24 hours after treatment. These 

concentrations were modeled for the five representative 

locations described above, and averaged to present the

potential effects of spray drift. Toxic risks to humans, 

wildlife, and non-target plants and other resources 

potentially affected by drift are presented in the relevant

sections of this chapter. 

Standard Operating Procedures 

The BLM has developed several management practices 

to minimize the potential adverse effects of herbicide 

use on air quality. These management practices are

based on direction provided in BLM air quality, 

chemical pest control, and weed management manuals 

(e.g., manuals 7000 and 9011) and handbooks (e.g., H9011-1; USDI BLM 1988d). Most of this guidance is 

related to the effects of spray drift or other forms of

wind transport of herbicides. For example, guidance on 

spray particle size, wind velocity and direction, height

of spray boom, herbicide formulation, and drift control

spray systems is presented with respect to effects on

spray drift and non-target species. The following SOPs 

have been developed to guide herbicide applications to 

minimize the effects on air quality: 

BLM Vegetation Treatments Using Herbicides 4-8 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

TABLE 4-3 

Annual Emissions Summary for Herbicide Treatments under Alternative B 

Pollutant (tons per year) State CO NOX TSP PM10 PM2.5 VOCs 

Alaska 0.00 0.00 0.00 0.00 0.00 0.00

Arizona 3.40 0.41 14.66 3.09 0.42 0.24

California 0.54 0.06 2.37 0.50 0.07 0.04

Colorado 2.06 0.24 4.88 1.07 0.14 0.18

Idaho 24.22 2.92 60.35 13.18 1.67 1.71

Montana 4.97 0.60 11.58 2.58 0.32 0.35

Nebraska 0.00 0.00 0.00 0.00 0.00 0.00

Nevada 10.81 1.26 47.63 10.18 1.39 0.75

New Mexico 4.85 0.54 17.73 3.97 0.54 0.40

North Dakota 0.00 0.00 0.00 0.00 0.00 0.00

Oklahoma 0.00 0.00 0.00 0.00 0.00 0.00

Oregon (Total) 5.00 0.57 28.77 6.97 0.99 0.34

Eastern 1.31 0.15 2.55 0.56 0.07 0.09

Western 3.87 0.43 26.22 6.40 0.91 0.26

South Dakota 0.08 0.01 0.20 0.05 0.01 0.01

Texas 1.07 0.13 2.46 0.55 0.07 0.08

Utah 2.42 0.28 8.56 1.88 0.25 0.21

Washington 0.43 0.05 1.01 0.23 0.03 0.03

Wyoming 2.42 0.28 5.69 1.24 0.16 0.21

Total 62.27 7.35 205.89 45.49 6.06 4.55

• Consider the effects of wind, humidity, 

temperature inversions, and heavy rainfall on 

herbicide effectiveness and risks. 

• Apply herbicides in favorable weather 

conditions to minimize drift. For example, do

not treat when winds exceed 10 mph (6 mph 

for aerial applications) or rainfall is imminent. 

• Use drift reduction agents, as appropriate, to 

reduce the drift hazard. 

• Select proper application equipment (e.g., 

spray equipment that produces 200- to 800-

micron diameter droplets [spray droplets of 100

microns and less are most prone to drift]). 

• Select proper application methods (e.g., set

maximum spray heights, use appropriate buffer 

distances between spray sites and non-target 

resources). 

The analysis of potential air quality impacts assumes 

that guidance provided in BLM manuals, handbooks, 

and SOPs would be followed during herbicide treatment

activities. 

Impacts by Alternative 

Impacts Common to All Alternatives 

The potential impacts from herbicide applications on 

local and regional air quality would be minor for each 

treatment alternative. None of the predicted annual 

emissions by pollutant, state, or herbicide treatment

alternative (A, B, D, and E) would exceed PSD annual

emission significance thresholds. Furthermore, the total

emissions from all the states, for each pollutant under

each alternative, would be less than 25% of the PSD 

threshold (250 tons per year) for a single facility. 

Comparing the total emissions produced by all the states 

to the PSD threshold is especially conservative because 

the PSD threshold is designed to apply to one facility or

a group of facilities and not entire states. For each

treatment alternative, potential emissions would be 

highest in states with the greatest number of acres

treated under each alternative. In addition, all PM 

concentrations resulting from a single example 

herbicide spraying event, as modeled using CALPUFF 

“lite,” would be substantially lower than NAAQS 

thresholds at the five representative locations, and 

predicted concentrations would be at least four orders of

magnitude smaller than assumed background

BLM Vegetation Treatments Using Herbicides 4-9 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-4 

Annual Emissions Summary for Herbicide Treatments under Alternative D 

Pollutant (tons) State CO NOX TSP PM10 PM2.5 VOCs 

Alaska 0.00 0.00 0.00 0.00 0.00 0.00

Arizona 1.75 0.14 14.45 3.05 0.42 0.10

California 0.56 0.07 2.41 0.51 0.07 0.04

Colorado 2.49 0.24 5.74 1.21 0.15 0.18

Idaho 25.63 3.63 63.68 13.86 1.76 1.95

Montana 5.15 0.61 11.88 2.63 0.33 0.36

Nebraska 0.00 0.00 0.00 0.00 0.00 0.00

Nevada 13.46 2.16 57.73 12.08 1.64 1.09

New Mexico 6.37 1.05 21.26 4.70 0.63 0.78

North Dakota 0.00 0.00 0.003 0.00 0.00 0.00

Oklahoma 0.00 0.00 0.00 0.00 0.00 0.00

Oregon (Total) 3.89 0.40 20.55 4.81 0.67 0.26

Eastern 1.39 0.15 4.26 0.93 0.12 0.09

Western 2.50 0.25 16.29 3.88 0.55 0.16

South Dakota 0.10 0.01 0.23 0.05 0.01 0.01

Texas 1.11 0.13 2.54 0.56 0.07 0.78

Utah 2.63 0.29 9.17 1.98 0.27 0.22

Washington 0.50 0.05 1.13 0.25 0.03 0.03

Wyoming 19.84 2.07 46.05 9.80 1.23 1.55

Total 83.48 108.50 256.82 55.49 7.28 7.35

concentrations (Table 4-6). Concentrations would vary 

by alternative based on the number of treatment events. 

Under the proposed alternatives, atmospheric 

concentrations of herbicides (predicted by particle size) 

resulting from spray drift from aerial, ground vehicle, 

and hand application would be temporary in nature 

(most predominant at the time and location of 

treatment) and, as predicted by modeling, would not

significantly impact air quality. Maximum average

herbicide concentrations from all five example

modeling locations, 24 hours after treatment, were

modeled at various distances from the point of 

application. Herbicide concentrations in the air tend to 

increase up to 1.5 kilometers (km) from the point of 

application (concentrations may double between 0.6 and 

1.5 km from the application site), but then decrease 

slowly at greater distances. 

Chemical volatilization is temporary in nature, and none

of the herbicides proposed for use are likely to result in 

substantial volatilization from soils. Chemical vapor 

pressure (the pressure exerted by a vapor in equilibrium

with its solid or liquid phase) largely affects the 

potential for volatilization of applied herbicides. Based

on their vapor pressures, bromacil, diflufenzopyr 

(Lyman et al. 1990; National Library of Medicine 

2002), diquat (National Library of Medicine 2003), 

diuron (Lyman et al. 1990; Mackay et al. 1997),

sulfometuron methyl (Lyman et al. 1990; National

Library of Medicine 2003), and tebuthiuron (Tomlin

1994) are not expected to volatilize from dry or wet soil 

surfaces. Vapor pressure values are not available for 

imazapic; however, imazapic does not volatilize when 

applied in the field (American Cyanamid Company 

2000 cited in Tu et al. 2001), and volatilization of

imazapic from terrestrial systems is insignificant. 

Fluridone might volatilize slowly from wet soil 

surfaces, but volatilization from dry soils would not be

expected (Lyman et al. 1990; Mackay et al. 1997;

National Library of Medicine 2002). In addition, 

dicamba may volatilize from soil surfaces, but such an 

occurrence is not considered likely unless dicamba has 

been exposed at the soil surface under hot and dry 

conditions for several weeks (USDI BLM 1988d). 

Therefore, application of the evaluated herbicides would 

not impact air quality through volatilization. 

BLM Vegetation Treatments Using Herbicides 4-10 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

TABLE 4-5 

Annual Emissions Summary for Herbicide Treatments under Alternative E 

Pollutant (tons) State CO NOX TSP PM10 PM2.5 VOCs 

Alaska 0.00 0.00 0.00 0.00 0.00 0.00

Arizona 1.70 0.20 7.33 1.54 0.21 0.12

California 0.27 0.03 1.18 0.25 0.03 0.02

Colorado 1.03 0.12 2.44 0.53 0.07 0.09

Idaho 12.12 1.46 30.17 6.59 0.84 0.86

Montana 2.49 0.30 5.79 1.29 0.16 0.18

Nebraska 0.00 0.00 0.00 0.00 0.00 0.00

Nevada 5.41 0.63 23.81 5.09 0.70 0.38

New Mexico 2.43 0.27 8.86 1.98 0.27 0.20

North Dakota 0.00 0.00 0.00 0.00 0.00 0.00

Oklahoma 0.00 0.00 0.00 0.00 0.00 0.00

Oregon (Total) 3.32 0.38 17.48 4.17 0.58 0.23

Eastern 1.39 0.16 4.36 0.97 0.13 0.10

Western 1.94 0.21 13.11 3.20 0.46 0.13

South Dakota 0.04 0.00 0.10 0.02 0.00 0.00

Texas 0.53 0.07 1.23 0.27 0.03 0.04

Utah 1.21 0.14 4.28 0.94 0.13 0.10

Washington 0.22 0.03 0.51 0.11 0.01 0.02

Wyoming 1.21 0.14 2.85 0.62 0.08 0.10

Total 31.98 3.77 106.03 23.40 3.11 2.34

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, following the current 

vegetation management program, approximately 

305,000 acres would be treated with herbicides each

year (Table 4-1). This is the lowest treatment acreage of

all alternatives, and it would correspond to emissions of

approximately 77 tpy of TSP, 24 tpy of CO, and 17 tpy

of PM10, with emissions of all other pollutants totaling 

less than 3 tpy (Table 4-2). These emissions are lower 

than those associated with each of the other alternatives.

In general, emissions would be greatest in states where 

more acres are treated (e.g., Idaho, New Mexico, Utah, 

and Wyoming).

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Under the Preferred Alternative, an estimated 932,000 

acres would be treated using herbicides annually. As 

this is the alternative with the greatest number of acres

treated, it would also result in the greatest pollutant 

emissions (206 tpy TSP, 62 tpy CO, and 45 tpy PM10; 

Table 4-3)—over 2 times the expected emissions under 

the No Action Alternative. These emissions would 

dominate in states with the greatest number of acres 

treated. Over half of the proposed herbicide treatment 

acreage under the preferred alternative would occur in 

Idaho and Nevada. Therefore, over half the predicted

annual emissions would occur in these two states. 

Alternative C – No Use of Herbicides 

Under Alternative C, herbicides would not be used for 

vegetation management. Because there would be no 

associated emissions, herbicide treatments would not 

impact air quality. However, as under all of the 

alternatives, other treatment methods (fire use and

mechanical, manual, and biological control methods) 

would emit pollutants, as discussed in the PER. 

 Alternative D – No Aerial Applications

Under Alternative D, about 529,000 acres would be 

treated annually using ground application methods 

alone. Although about 40% fewer acres would be 

treated under this alternative than under the Preferred

Alternative, Alternative D would generate the most

pollutant emissions (Table 4-4). Alternative D would 

result in approximately 257 tpy TSP, 83 tpy of CO 

emissions, and 55 tpy of PM10 emissions, which is more 

than 20% more pollutant emissions than under the

BLM Vegetation Treatments Using Herbicides 4-11 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-6 

Example NAAQS Compliance Analysis for Chemical Treatment 

Location Pollutant Averaging 

Period 

CALPUFF 

Concentration 

(μg/m3

) 

Background 

Concentration1

(μg/m3) 

Total 

Concentration 

(μg/m3

) 

NAAQS 

Standard2

(μg/m3) 

24-hour 2.79E-04 40 40 NA TSP 

Annual 7.65E-07 11 11 NA

24-hour 5.47E-04 30 30 150 PM10 Annual 1.50E-06 8 8 50

24-hour 7.21E-05 30 30 35

Tucson, 

Arizona 

PM2.5 Annual 1.97E-07 8 8 15

24-hour 1.06E-04 40 40 NA TSP Annual 2.90E-07 11 11 NA

24-hour 2.36E-04 30 30 150 PM10 Annual 6.48E-07 8 8 50

24-hour 2.82E-05 30 30 35

Glasgow, 

Montana 

PM2.5 Annual 7.74E-08 8 8 15

24-hour 1.36E-04 40 40 NA TSP Annual 3.72E-07 11 11 NA

24-hour 2.72E-04 30 30 150 PM10 Annual 7.44E-07 8 8 50

24-hour 3.60E-05 30 30 35

Winnemucca, 

Nevada 

PM2.5 Annual 9.85E-08 8 8 15

24-hour 3.75E-03 40 40 NA TSP Annual 1.04E-05 11 11 NA

24-hour 8.20E-03 30 30 150 PM10 Annual 2.28E-05 8 8 50

24-hour 1.14E-03 30 30 35

Medford, 

Oregon 

PM2.5 Annual 3.19E-06 8 8 15

24-hour 6.08E-05 40 40 NA TSP Annual 1.67E-07 11 11 NA

24-hour 1.37E-04 30 30 150 PM10 Annual 3.75E-07 8 8 50

24-hour 1.72E-05 30 30 35

Lander, 

Wyoming 

PM2.5 Annual 4.70E-08 8 8 15

1 PM10 Data from Table 6.1 of the Montana Modeling Guideline for Air Quality Permits (November 2002; Montana Department of Environmental 

Quality [2002]). TSP concentrations calculated by multiplying PM10 data by 1.33. PM10 concentrations are also conservatively used as background 

concentrations for PM2.5. 2 None of the states analyzed have ambient air quality standards for TSP.

NA = Not applicable.

Preferred Alternative. Compared to the Preferred

Alternative, there would be greater engine emissions 

from ground vehicle use (in the absence of aerial

spraying) and greater fugitive dust emissions from use

of these vehicles on dirt roads. None of the states 

analyzed have ambient air quality standards for TSP, 

and all other emissions for this alternative (and for each 

state) would be below the PSD emission significance 

threshold of 250 tpy. However, because the potential for 

spray drift is usually highest in aerial applications, drift

per acre of application would likely be lower for 

Alternative D than for alternatives A, B, and E (spray

drift is also largely dependent on weather conditions 

such as wind speed, temperature, and precipitation). See 

the Vegetation, Fish and Other Aquatic Resources, 

Wildlife Resources, and Human Health and Safety 

sections for the potential toxic effects of spray drift on

humans, non-target plants, and animals. 

BLM Vegetation Treatments Using Herbicides 4-12 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides

Under Alternative E, approximately 466,000 acres

would be treated annually using herbicides. Particulate 

emissions under Alternative E (106 tpy TSP, 32 tpy CO, 

and 23 tpy PM10; Table 4-5) would be about twice those

under the current vegetation management program (No

Action Alternative). Half of the acreage treated would

be in Idaho and Nevada, which would experience

slightly more than half (53%) of the emissions under 

Alternative E. 

Mitigation for Herbicide Treatment 

Impacts 

No mitigation measures are proposed for air quality. 

Soil Resources 

Introduction 

Soil refers to the loose material composed of weathered

rock and other minerals and partly decayed organic

matter that covers large parts of land surfaces. Soil

provides habitats for a great variety of organisms, 

functions as an essential component of terrestrial

ecosystems, and is the essential medium for plant

growth (Wild 1993). Healthy soil is fundamental to high 

functioning ecosystems, contains a diverse, thriving 

community of organisms, and. functions to protect 

downgradient ecosystems by functioning as a physical

and biological filter of chemicals in the environment. 

Noxious weeds and other invasive vegetation can

impact soil function and reduce soil biodiversity. The 

amount of moisture in the soil can be altered if 

infiltration is reduced and runoff is increased on sites 

dominated by weeds (Lacey et al. 1989). Many noxious 

and invasive weeds have relatively sparse canopies, 

which allow for greater evaporation from the exposed 

soil than dense vegetative cover. Sites infested with

weeds often have more extreme soil temperatures that

can alter soil moisture regimes. Noxious and invasive 

weeds may alter soil nutrient availability for native

species, alter soil constituents (e.g., soil fungi and 

bacteria), and slow the rate of natural plant succession 

(Olson 1999). Some weeds also produce toxins or

allelopathic compounds that can suppress the growth

and germination of other plants (Kelsye and Bedunah

1989). 

Herbicide applications inevitably result in contact with 

soils, either intentionally for systemic treatments, or

unintentionally as spills, overspray, spray drift, or

windblown dust. In addition to direct application,

transmission to soil may occur when an herbicide is 

transported through the plant from sprayed aboveground

portions to roots, where it may be released into soil.

Also, some herbicides remain active in plant tissue and 

can be released into the soil during plant decay and 

result in residual herbicide activity. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Commentors on the draft PEIS encouraged the BLM to 

focus vegetation management within the structure of 

achieving long-term ecosystem sustainability and 

maintaining biological diversity. In a general sense, soil

health is a keystone factor for maintaining ecosystem

sustainability. Concerns were voiced for evaluating 

groundwater protection, as certain soil characteristics 

play a role in attenuating the risk of groundwater 

contamination. 

There was considerable concern that the PEIS should 

address herbicide fate and transport, such as runoff, 

overspray, drift, and drift of wind-eroded soil. One 

respondent recommended measuring organochlorine 

residues in soil. Other respondents felt that disturbances 

to biological soil crusts should be eliminated, that sites 

where the crust species are locally extinct must be reinoculated, and that signs should be placed alongside 

trails to educate hikers about biological soil crusts. 

Standard Operating Procedures 

The BLM would implement several SOPs to reduce 

impacts to soil: 

• Minimize treatments in areas where herbicide 

runoff is likely, such as steep slopes when 

heavy rainfall is expected. 

• Minimize use of herbicides that have high soil 

mobility, particularly in areas where soil 

properties increase the potential for mobility. 

• Do not apply granular herbicides on slopes of 

more than 15% where there is the possibility of

runoff carrying the granules into non-target

areas. 

BLM Vegetation Treatments Using Herbicides 4-13 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Factors that Influence the Fate,

Transport, and Persistence of 

Herbicides in Soil 

The fate and transport of herbicides in soil is a function 

of their interaction with the soil environment, and is

generally considered a complex process (Bovey 2001). 

Chemical, physical, and biological soil processes 

influence herbicide availability, phytotoxicity, and fate 

and transport (Anderson 1982). Herbicides dissipate 

from soils by transport with water or wind, through

chemical or biological degradation processes, or by

immobilization through adsorption onto soil surfaces. 

Chemical Processes 

Adsorption 

Adsorption to soil surfaces is probably the most

influential factor on the fate and transport of herbicides 

in soils (Chiou and Kile 2000). Adsorption in soils is the

process whereby ions and molecules are bonded to the 

surface of soil colloids due to the electrical attraction 

between themselves and the colloidal particles. All soilapplied herbicides are adsorbed to some extent. 

Adsorption occurs onto clay particles and onto both the

solid and dissolved forms of organic matter. Adsorption

affects herbicide mobility and availability to plants and 

other organisms, which in turn influences herbicide fate. 

The organic carbon-water partitioning coefficient (Koc),

measures the affinity of a chemical to adsorb to soil 

organic carbon (a component of soil organic matter) 

relative to water (Table 4-7). For a given chemical, the 

greater the Koc value, the less soluble the chemical is in

water and the higher affinity the chemical has for soil 

organic carbon. For most chemicals, a higher affinity

for soil organic carbon (greater Koc) results in less 

mobility in soil. When herbicide active ingredients are

very water-soluble (low Koc values), the risk of leaching 

through soils and transport to surface water and

groundwater increases. 

Photochemical Decomposi ion and Chemical 

Reactions with Soil Con ti uents 

t

s t

Photodegradation and chemical reactions are common

chemical degradation pathways in the environment. 

Herbicides may degrade in the presence of sunlight, 

converting to degradation products in a relatively short

time. Chemical reactions, including hydrolysis, occur 

when chemical transformations replace or remove

portions of the herbicide active ingredient’s chemical

structure, rendering it inactive. 

Physical Processes 

Leaching 

Leaching through soils is dependent on herbicide use

patterns as well as soil texture, total organic carbon in

soil, chemical half-life, amount and time of rainfall, and

depth to water table. Fine-grained soils inhibit herbicide 

leaching because of either low vertical permeability 

through the soil or high soil surface area, both of which

enhance adsorption to the solid phase. Coarse-grained 

soils with low total organic carbon do not adsorb

herbicides as readily, and leaching is more likely. 

Volatility 

Volatilization is the process by which a substance 

passes from a solid or liquid state to a gaseous state. The 

volatilization of herbicides applied to soils is of concern

when poor weed control occurs due to loss of the 

herbicides from the soil, or when injury to non-target

species occurs due to drip of the vapors of the 

herbicides. None of the herbicides proposed for use are 

likely to result in substantial volatilization from soils. 

Herbicide movement in soil depends on herbicide 

concentration, as well as on the physical status of soil,

especially soil moisture content, organic matter content, 

and temperature. 

Generally, herbicides may be moved from the 

application area with water runoff, or be leached

through soil by rainwater infiltration and potentially

reach the groundwater. Herbicide transport in runoff is

usually greatest in areas with poorly infiltrating soils, 

flooding, and steep slopes. Poorly infiltrating soil 

includes compacted soil, soil with a non-biological

surface crust, and fine textured soil, such as clay and 

clay loam. 

Transport with Water or Wind 

Herbicide transport includes movement with water or 

wind. 

Wind can transport herbicides that have adsorbed to 

particles. The potential for wind blown transport

depends on the weather and condition of the soil. Fine 

sand or silty textured soils, low soil stability, soil

disturbance, and dryness all increase the risk for wind 

erosion of herbicide-containing particles. 

BLM Vegetation Treatments Using Herbicides 4-14 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

TABLE 4-7 

Estimated Soil Half-life and Adsorption Affinity 

for Active Ingredients 

Herbicide Soil Halflife (days) Soil Adsorption (Koc) 

2,4-D 10 20 m/g (acid/salt), 

100 mL/g (ester)

2,4-DP 10 1,000 mL/g

Asulam 7 40 mL/g

Atrazine 60 100 mL/g

Bromacil 60 32 mL/g

Chlorsulfuron 40 40 mL/g

Clopyralid 40 6 mL/g, ranges to 

60 mL/g

Dicamba, sodium salt, 

or dimethylamine salt 14 2 mL/g

Diflufenzopyr, sodium

salt 2 to 14 18 to 156 mL/g

Diquat 1,000 1,000,000 mL/g

Diuron 90 480 mL/g

Fluridone 21 1,000 mL/g

Fosamine 8 150 mL/g

Glyphosate 47 24,000 mL/g

Hexazinone 90 54 mL/g 

Imazapic 120 to 140 206 mL/g 

Imazapyr 25 to 141 1,000 mL/g 

Mefluidide 4 200 mL/g

Metsulfuron methyl 30 35 mL/g

Picloram 90 16 mg/L

Simazine 60 130 mL/g

Sulfometuron methyl 20 78 mL/g

Tebuthiuron 360 80 mL/g

Triclopyr 46 20 mL/g (salt), 

780 mL/g (ester)

Source: Vogue et al. (1994).

Biological Processes 

For best results, herbicides must remain in soils in an 

active and available form until their purpose is

accomplished. Herbicidal activity is desirable, however,

only until the herbicides have achieved their intended 

effect; longer persistence may pose a hazard to

subsequent land use (Anderson 1982). 

The length of time that an herbicide remains active in 

soils is called soil persistence or soil residual life. The

half-life is the time it takes for half of the mass of an 

herbicide to disappear. The half-life can vary widely in 

soil, with some times as short as a matter of days and

others taking years (Table 4-7). Chemical characteristics 

of the herbicide, as well as soil characteristics,

especially moisture, temperature, organic matter, and 

the type and activity of soil organisms influence 

herbicide half-lives. 

Soil microorganisms can sometimes degrade herbicide

active ingredients. Moderate temperatures, organic 

material, and adequate moisture result in biologically 

active soils with large populations of soil

microorganisms usually including capabilities for

biodegradation. In contrast, soils that are very dry or

wet, very cold or hot, or have low organic matter 

generally have less biological activity and smaller 

populations of active soil microorganisms. 

Impacts by Treatment

The following section discusses impacts to soil from 

herbicides currently used by the BLM and from

herbicides proposed for use. This assessment of impacts 

assumes that SOPs (see Table 2-8) would be followed. 

SOPs are designed to reduce potential unintended 

impacts to soil. These procedures include using the 

lowest effective application rate; testing smaller areas 

for unintended consequences prior to treating larger 

areas; evaluating soil characteristics to determine the

likelihood of herbicide transport by runoff, infiltration, 

or wind; limiting herbicide use on fine-textured and 

sandy soils, especially where soil can be transported 

onto adjacent areas potentially harming non-target

vegetation; and carefully evaluating the use of

herbicides on hot, dry, cold, wet, sodic (containing high

levels of sodium), and saline (containing high levels of

salts) soils. 

Herbicides may indirectly affect soil through plant 

removal resulting in changes in physical and biological

soil parameters. As vegetation is removed, there is less 

plant material to intercept rainfall and less to contribute 

organic material to the soil. Loss of plant material and

soil organic matter can increase the risk of soil

susceptibility to wind and water erosion. The risk for 

increased erosion would be temporary, lasting only until

vegetation was reestablished. If herbicide treatments 

lead to revegetation with native plants, soil stability may 

be improved relative to sites dominated by invasive 

plants. 

There are few studies addressing herbicide effects on 

biological soil crusts. Therefore, caution should be used 

when applying these chemicals to soils supporting

biological soil crusts (Belnap et al. 2001) or to areas 

where management goals include crust recovery. 

Youtie et al. (1999) studied the effects of two

glyphosate herbicide formulations (Roundup® and 

Accord®) on moss-dominated biological soil crusts in a

native bunchgrass community invaded by non-native 

BLM Vegetation Treatments Using Herbicides 4-15 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

grasses. Effects were measured by the change between 

pre- and post-treatment cover. The results showed that 

herbicide treatments did not have short-term impacts on

bryophyte (moss and liverwort) cover or species 

diversity. In addition, biological crust cover was 

reduced where annual grass leaf litter accumulated, and

herbicide treatment reduced litter buildup, suggesting 

that herbicide treatment slowed the loss of crust cover 

from annual grass invasion. The authors cautioned that 

removal of annual grasses requires repeated applications 

of herbicides and that long-term effects were not

known. 

Gadkari (1988 cited in Belnap et al. 2001) observed that 

a photosynthesis-inhibiting herbicide (simazine) had a

significant impact on Nostoc (an algal community

constituent) growth and nitrogen fixation. Some

herbicides appear to inhibit growth and reproduction of 

green algae when biological crust species are tested

under lab conditions (Belnap et al. 2001). Both positive 

and negative effects have been observed, depending on

the compound and the species (Metting 1990). Peterson 

et al. (1994 cited in SERA 2004e) observed significant 

inhibition in growth of three species of cyanobacteria in 

laboratory exposures using metsulfuron methyl at a 

concentration of 0.003 milligrams active ingredient per 

liter (mg a.i./L). Of the several common constituents of 

the crust community, the cyanobacteria, which

generally are embedded in the soil, may be the most

resilient. In contrast, because lichen and moss 

constituents generally lay above the soil surface, they

may be more susceptible to herbicide damage (Belnap 

2005). 

Impacts of BLM-evaluated Herbicides

Bromacil 

Bromacil can be used as a pre-emergent herbicide, and 

residual soil activity is necessary for this herbicide to be 

effective. Bromacil is persistent and highly mobile in 

soil, with a half-life of 124 to 155 days (see ENSR 

2005b). There is limited research on the toxicity of

bromacil to most soil organisms. It biodegrades in 

anaerobic soil, but biodegradation is slow in aerobic 

soil, with an estimated biodegradation half-life of 275 to 

350 days, suggesting possible toxicity to some soil

organisms. One soil bacterial isolate that can biodegrade 

bromacil has been identified (Chaudhry and Cortez 

1988). 

Chlorsulfuron 

Chlorsulfuron rapidly degrades in acidic soil by 

chemical hydrolysis, but remains relatively stable in

neutral soil (see ENSR 2005c). The products of 

chemical hydrolysis are then biodegraded in soil

(Sarmah and Sabadie 2002). Chlorsulfuron soil

biodegradation rates are negatively correlated with pH 

and positively correlated with temperature, soil moisture

content, organic matter content, and microbial biomass 

(James et al. 1999). 

Chlorsulfuron reportedly remains active in soils for 

more than 1 year after application, especially at low 

temperatures and high pH (James et al. 1999). In a 

laboratory study in sandy soil, only 4% of added 

chlorsulfuron was transformed 126 days after 

application, and high residual concentrations were

found in the lower soil profile (Andersen et al. 2001). 

Sarmah et al. (1999) observed that the rate of

chlorsulfuron degradation in alkaline subsoils was slow. 

They concluded that under conditions conducive to

leaching in alkaline systems, prolonged persistence of 

chlorsulfuron in the soil profile is possible. It is likely 

that in some soils dissipation rates could be slower than

the reported average, including arid soils with high pH 

and low organic matter. 

Chlorsulfuron appears to be only mildly toxic to 

terrestrial microorganisms, and effects are generally 

transient (SERA 2004a) even though bacteria have an 

enzyme that is functionally equivalent to the herbicide 

target enzyme in plants. Biodegradation of 

chlorsulfuron does occur in some soil systems. For 

example a bacterial strain (Pseudomonas fluorescens

strain B2) isolated from soil was able to degrade 32% of 

added chlorsulfuron within 2 weeks (Zanardini et al.

2002). Rovesti and Desco (1990 cited in SERA 2004a) 

studied two soil nematode species in soil exposed to 312 

to 10,000 ppm chlorsulfuron for 72 hours, and no effect

was observed on reproduction, viability, or movement. 

Diuron

Diuron is highly persistent and has low to moderate 

mobility in soil (see ENSR 2005f). Despite its reported 

low to moderate soil mobility, diuron is frequently 

detected in groundwater (Spurlock et al. 2000). Sorption

studies of diuron have shown that the proportion of 

organic matter in soil directly influences the amount of

adsorbed diuron. Biodegradation is the major source of 

diuron attenuation, occurring under both aerobic and 

anaerobic conditions.

BLM Vegetation Treatments Using Herbicides 4-16 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

In one study, biodegradation in soil increased with

increasing temperature and decreasing initial

concentration, while pH had little effect on the

degradation rates (ENSR 2005f). Biodegradation does 

not occur at freezing temperatures. 3,4-dichloraniline

(3,4-DCA) is one breakdown product of diuron. 3,4-

DCA is also persistent in soil and reportedly exhibits a

higher toxicity to some receptors (Tixier et al. 2002;

Skogerboe 2003; Giacomazzi and Cochet 2004). In soil, 

3,4-DCA can exceed 5.0 μg/kilograms (kg) at typical

application rates (Giacomazzi and Cochet 2004).

Waterfleas are negatively affected by fairly low 

concentrations (1.0 μg/L) of 3,4-DCA in water, but it is 

unknown if effects to crustaceans occur in soil. 

Widehem et al. (2002) identified a common soil bacteria 

capable of transforming diuron to 3,4-DCA. In addition, 

3,4-DCA was degraded by four fungal species (Tixier et

al. 2002). 

Diuron had adverse effects on bacterial community

structure and on bacterial activity at a concentration of 

25 mg/L (Giacomazzi and Cochet 2004). One study 

showed by molecular techniques that bacterial diversity 

seemed to decrease in soil treated by diuron or other 

phenylurea herbicides. 

Dicamba 

Dicamba is not adsorbed by most soils and is highly

mobile. Dicamba is moderately persistent in soil. 

Biodegradation is its primary fate, with slower rates at 

lower temperatures and in dry soil. It is likely to be 

rapidly degraded in soils with high microbial 

populations, but dissipates more slowly in hardwood

forest soils (Voos and Groffman 1997a, b). The slower 

dissipation in hardwood forest soils is probably 

attributable to adsorption of dicamba in acidic and 

highly organic soil horizons. One study reported that 

dicamba dissipated from grassland soils in Texas in 4 

weeks when applied at 0.25 lb/ac, and in 9 to 16 weeks 

when applied at 0.5 lb a.i./ac (Bovey 2001). However, 

when dicamba granules were applied at rates of 1.5 or 

1.86 lbs a.i./ac to sand in semiarid grassland, dicamba 

residues were detected up to 48 inches deep 53 weeks 

after application. The primary breakdown product of

dicamba is 3,6-dichlorosalicylic acid, which adsorbs to 

soils strongly. Very little information is available on the

toxicity of this breakdown product (USDA Forest

Service 1999). 

According to one study, dicamba caused a transient 

decrease in nitrification after incubation in sandy loam

soil at an application rate of 10 mg/kg, but this decrease 

was not substantial and was not observed after 3 weeks 

of incubation (Tu 1994). In the same study, dicamba did

not affect ammonia formation or sulfur oxidation.

Martens and Bremner (1993) showed that dicamba did

not affect urea hydrolysis or nitrification in four soil

types at an application rate of 1 mg/kg. Dicamba did

decrease urea hydrolysis by 6% in one of the four soil

types, and inhibited nitrification in two of the soils at 7

and 14 days, but not at 21 days, after application at a

rate of 50 mg a.i./kg soil. After herbicide applications

for 24 years, there were no detectable residues of

dicamba in soil at two long-term tillage sites or one 

long-term manured site, probably due to biodegradation 

and mobility (Miller et al. 1995). 

Diflufenzopyr 

Biodegradation, photodegradation, and hydrolysis are 

the primary mechanisms that remove diflufenzopyr 

from soil. Koc values range from 18 to 156 ml/g. Soil

biodegradation and photodegradation half-lives are 14

days or less (USEPA 1999c). Diflufenzopyr appears to

be soluble enough that transport in surface runoff is

possible, especially in neutral to alkaline soils (see

ENSR 2005d). 

Diquat 

Diquat readily adsorbs to soil surfaces, effectively 

immobilizing the chemical. The amount of diquat 

adsorbed depends on the type and amount of clay 

particles present, with soils high in clay adsorbing larger 

amounts than sandy soils. Sodic and saline soils adsorb

reduced amounts (Kookana and Aylmore 1993). Diquat 

is resistant to anaerobic and aerobic biodegradation, 

possibly in part because it adsorbs so well to soil

particles. There is some evidence that the more loosely 

bound fraction of diquat may be subject to slow 

biodegradation (Howard 1991). The half-life of diquat 

is 3 years or longer (see ENSR 2005e). 

Fluridone 

Fluridone applications target unwanted aquatic 

vegetation, especially submerged vegetation. Fluridone 

adsorption to soil increases with clay content, organic 

matter content, cation exchange capacity, surface area,

and decreasing pH (Weber et al. 1986 and Reinert 1989 

cited in ENSR 2005g). The half-life of fluridone ranges 

from 44 to 365 days when it is applied on sandy loam, 

sandy clay loam, and peaty loam soils (10 oC and 18o to

24 oC; Howard 1991). Longer half-lives tend to be 

associated with dry soils (Malik and Drennan 1990 cited 

in ENSR 2005g). Fluridone can volatilize slowly from

BLM Vegetation Treatments Using Herbicides 4-17 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

wet soil surfaces, but volatilization from dry soils would

not be expected (ENSR 2005g). 

The toxicity of fluridone to earthworms has been 

measured. No mortality was seen in direct exposures up 

to 103 mg/L (103 ppm; Eli Lilly and Company 2003); 

this concentration is approximately 1,000 times greater 

than the expected soil concentration in a typical use 

application. 

Imazapic

Imazapic is moderately persistent in soils and has not

been found to move laterally with surface water. 

Imazapic has a half-life of 120 days in soil due to

photolysis and a half life of 31 to 233 days in soil due to

microbial degradation (American Cyanamid Company 

2000 cited in Tu et al. 2001). Most imazapic is lost 

through biodegradation. Sorption to soil increases with 

decreasing pH and increasing organic matter and clay

content. Little is known concerning the effects of

imazapic on soil organisms or processes (see ENSR

2005h). 

In the risk assessment for imazapic (SERA 2004c), 

Groundwater Loading Effects of Agricultural

Management Systems (GLEAMS) modeling estimated

the proportion of applied imazapic lost by runoff for 

clay, loam, and sand at rainfall rates ranging from 5 to

250 inches per year. Runoff would be negligible in

relatively arid environments, as well as areas with sandy 

or loam soils. In clay soils, which have the highest 

runoff potential, off-site loss could reach up to 3.5% of 

the applied amount in regions with very high rainfall

rates. The model showed that as rainfall rate increases, 

maximum soil concentrations are reduced because of 

imazapic losses from soil through percolation or runoff. 

Modeling also showed that longer-term concentrations 

in soil vary substantially with rainfall rates, ranging

from about 1 to 2 mg a.i./kg soil in very arid soils to

about 0.01 mg a.i./kg soil in regions with high rainfall. 

Sulfometuron Methyl 

Sulfometuron methyl is hydrolyzed in acidic soil, but is 

stable in neutral soil. Hydrolysis and biodegradation 

appear to be important degradation pathways in soil

(Sarmah and Sabadie 2002). The degradation rate for 

sulfometuron methyl was found to increase with

increasing soil temperature and moisture content, and 

the half-life ranged from 2 to 5 weeks. Sulfometuron 

methyl moves readily through conductive, coarsetextured soils such as sand and sandy loams (ENSR 

2005j).

Effects of sulfometuron methyl to soil organisms are not 

well studied. A study on the response of

ectomycorrhizal symbiotic formation to sulfometuron

methyl applications showed that the herbicide did not

result in a reduction of the symbiont on tree seedlings 

(Busse et al. 2004). 

Tebuthiuron 

In soil, tebuthiuron is resistant to abiotic degradation 

and biodegradation. Its field half-life ranges from 2

weeks to over 33 months (see ENSR 2005k). It has a 

low adsorption affinity to soil, with some adsorption

occurring as organic matter and clay content increase. It

is mobile in soil and has been detected in groundwater 

(USEPA 1994a). 

The amount of tebuthiuron recovered from application 

sites in northcentral Arizona declined from 55% of that 

applied after 1 year to 5% after 8 years, but then 

increased during the remaining 3 years of the study. The

increase may have been due to release of the soiladsorbed fraction. No metabolites were found, 

suggesting little or no degradation in soil (National

Library of Medicine 2002). Montgomery (1997) 

reported that 38% of tebuthiuron applied to rangeland at

a rate of 0.84 kg/ha tebuthiuron remained after 21

months. 

In an evaluation of brush control and reseeding in a post

oak forest using tebuthiuron applied at a rate of 2.2

kg/hectare (ha), Gay et al. (1997) determined that total

soil nitrogen was unchanged after treatment regardless 

of the reseeding method, possibly indicating few 

changes to nitrogen cycling from treatment methods. 

After a tebuthiuron application at the rate of 1.01 kg/ha 

in pellet form to sagebrush semi-desert in Utah, soft

brome had both reduced persistent mycorrhizal root

infection and reduced mycorrhizal spore density in its 

rhizosphere (Allen and West 1993). The herbicide did 

not appear to affect germination of mycorrhizal spores 

collected 6 months after herbicide application. Mostafa 

and Helling (2003) isolated three tebuthiuron-degrading

bacteria from soil. Shelton et al. (1996) demonstrated

that a Streptomyces strain degraded tebuthiuron in vitro. 

Impacts of Forest Service-evaluated Herbicides

2,4-D 

It is generally accepted that 2,4-D is rapidly inactivated 

in moist soil (Bovey 2001). However, its fate is largely 

dependent on pH (Aly and Faust 1964 cited in Tu et al.

2001). In alkaline soil, 2,4-D is rapidly converted to a

BLM Vegetation Treatments Using Herbicides 4-18 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

form that is susceptible to photodegradation and

biodegradation, and that does not readily adsorb to soil

particles. In acidic soil, 2,4-D resists degradation 

(Johnson et al. 1995 cited in Tu et al. 2001). 

The half-life of 2,4-D averages 10 days in moist soils,

but can be longer in cold or dry soils, or where the 

microbial community is not present to facilitate

degradation (Tu et al. 2001). Warm and moist soil 

conditions that enhance microbial populations facilitate

2,4-D degradation (Foster and McKercher 1973 cited in

Tu et al. 2001). In addition, 2,4-D has been shown to 

dissipate more rapidly in soils previously treated with 

2,4-D, presumably because of an increase in 2,4-D 

degrading bacteria after the first application (Oh and

Tuovinen 1991, Smith and Aubin 1994, and Shaw and

Burns 1998 cited in Tu et al. 2001). 

Studies have generally shown that at typical application

rates, no effect from 2,4-D can be detected on soil

macroorganisms (Eijsackers and Van Der Drift 1976). 

Furthermore, most studies of the effects of 2,4-D on

microorganisms concluded that the quantity of 2,4-D

reaching the soil from typical applications would 

probably not have a serious negative effect on most soil

microorganisms (Bovey 2001). 

Clopyralid 

Clopyralid is unstable in soil, and its field dissipation 

half-life ranges from 10 to 161 days (SERA 2004b). 

Clopyralid does not appear to bind tightly to soil and 

will leach under favorable conditions; however, the

potential for leaching or runoff is attenuated by the

apparently rapid biodegradation of clopyralid in soil. 

Clopyralid can be persistent in plants, and can result in 

soil activity when plants containing clopyralid die and 

biodegrade, releasing clopyralid to the soil where it can

again be taken up by plants. 

Hassan et al. (1994 cited in SERA 2004b) summarized

the effects of clopyralid on potential biocontrol agents. 

Exposures to clopyralid resulted in less than 30% 

mortality to 14 out of 17 insects and predatory mites in

contact bioassays. Higher mortality rates (25% to 50%) 

were observed with clopyralid exposures to three 

insects: a beetle species, a pirate bug, and a green 

lacewing. A laboratory study on spiders reported an

acute (96-hour) lethality of less than 10% following a

direct application of clopyralid (as Lontrel EC, an

emulsifiable concentrate of clopyralid) at the 

recommended application rate (Pekar 2002). 

At concentrations of 1 or 10 mg a.i./kg soil, clopyralid

had no effect on nitrification, nitrogen fixation, or

degradation of carbonaceous material (Hassan et al.

1994 cited in SERA 2004b). Applications of Lontrel EC 

at 0.26 lb/ac had no substantial effect on spore 

germination in a fungal bioherbicide for round-leaved 

mallow (Grant et al. 1990 cited in SERA 2004b). 

Glyphosate 

Glyphosate is a polar compound that is inactivated by 

soil adsorption. Adsorption is controlled by soil pH to a

large degree (Gimsing et al. 2004). Glyphosate is watersoluble, but it has a high affinity to bind to soil particles 

(SERA 2003a). Adsorption of glyphosate increases with

increasing clay content and cation exchange capacity, 

and decreasing soil pH and phosphorous content

(Sprankle et al. 1975, Hance 1976, Nomura and Hilton 

1977, and Rueppel et al. 1977 cited in Tu et al. 2001). 

Glyphosate is biodegraded by soil organisms, and many

species of soil microorganisms can use glyphosate as a

carbon source (SERA 2003a). Glyphosate exposure 

results in the inhibition of respiration and nucleic acid 

synthesis in plants and in microorganisms. There is little

information, however, to suggest that glyphosate is 

harmful to soil microorganisms under field conditions;

some studies suggest glyphosate may benefit some soil

microorganisms. 

In a study of the direct and indirect effects of long-term

glyphosate applications in ponderosa pine plantations in 

California, Busse et al. (2004) determined that both

direct and indirect soil microbial characteristics in the 

top 4 inches of soil were generally unchanged after 9 to 

13 years of continuous vegetation control by

glyphosate. Single or repeated applications of 

glyphosate at the recommended field concentration had

little effect on microbial communities. 

Hexazinone 

Hexazinone has a relatively low affinity for soil

particles and dissolves in soil water. Biodegradation is 

an importation fate, and the half-life in soil averages 

about 90 days, although hexazinone has been reported

in the soil at low concentrations for up to 3 years after 

application. Soil organic matter content does not affect

adsorption. 

One field study designed to detect effects on non-target 

species suggests that hexazinone may have an effect on

the behavior of soil mites. At an application rate of 0.9 

lb/ac, soil mites tended to migrate deeper into the soil

BLM Vegetation Treatments Using Herbicides 4-19 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

than mites from untreated plots. However, it is not

known whether this behavior is related to toxicity, 

avoidance, or some other unidentified factor (Badejo

and Adejuyigbe 1994). When testing pure strains of 

ectomycorrhizal fungi in a laboratory assessment, Diaz 

et al. (2003) determined that hexazinone had little or no

adverse effect on fungi, and even stimulated the growth 

of one strain. 

Hexazinone did not adversely affect the nitrogen cycle 

or soil respiration in acidic plant soils when applied at

the recommended application rate (Vienneau et al. 

2004). Busse et al. (2004) found that hexazinone did not

alter soil respiration and the capability of mycorrhizal

fungi to infect conifer seedling roots, even at

concentrations detrimental to seedling growth. 

I r

s

mazapy

Imazapyr is water soluble, potentially mobile, and has a 

long half-life (SERA 2004d). Imazapyr does not readily 

bind to mineral soils, but is likely to bind relatively 

strongly to organic soil. In a study of the fate of 

imazapyr applied to a railroad ROW, most imazapyr 

was found in the upper 12 inches of the soil and 

exhibited a half-life in the range of 67 to 144 days

(Borjesson et al. 2004). 

Imazapyr may persist in soil for a prolonged period in 

relatively arid regions, and does not bind tightly to

alkaline soils with low organic matter. Thus, the

potential for longer-term effects on soil organisms and

downgradient systems exists (SERA 2004d). Imazapyr 

can “leak” from treated plants into the soil, where it

remains active and can be taken up by non-target plants 

(Tu et al. 2001). 

Effects on soil microorganisms appear to be highly

species specific, with variations in sensitivity among

species of up to a factor of 100 (SERA 2004d).

Imazapyr can affect some sensitive microorganisms and

potentially shift soil microbial community composition 

toward imazapyr tolerant species. Imazapyr can inhibit 

rates of cellulose decomposition and carboxymethyl

cellulase activity in peat soil with 59% organic carbon

(Ismail and Wong 1994 cited in SERA 2004d).

Met ulfuron Methyl 

The principal modes of degradation of metsulfuron 

methyl are hydrolysis and microbial degradation, with

the latter being the only major pathway in alkaline soils 

(Sarmah et al. 1998). Degradation rates are affected by

soil temperature, moisture content, and soil pH. Halflives in acidic or neutral soils vary from 5 to 190 days

(Sarmah and Sabadie 2002, SERA 2004e). In acidic 

soils, adsorption of metsulfuron methyl is influenced by

soil temperature, clay content, and organic matter 

content. In alkaline soils, adsorption is very low and

leaching potential is high. This is likely to result in

increased persistence in alkaline subsoils that often lack 

organic matter and biological activity (Sarmah et al. 

1998). 

An application of metsulfuron methyl at a rate of 5 mg

a.i./kg soil decreased levels of amylase, urease, and

protease activity in loamy sand and clay loam soil

(Ismail et al. 1998). At surface application rates of 0.04

to 0.067 lb/ac, decreases in soil bacteria were apparent

for 3 days but reversed completely after 9 days. 

Biodegradation of metsulfuron methyl increased as soil

moisture increased from 20% to 80% of field capacity, 

and half-life increased when temperature was raised

from 20° to 30°C (Ismail and Azlizan 2002). Peterson et

al. (1994 cited in SERA 2004e) observed significant 

inhibition in growth of three species of cyanobacteria

using metsulfuron methyl at a concentration of 0.003

mg a.i./L. 

Picloram 

Photolysis and biodegradation are primary mechanisms 

of dissipation of picloram (USDA Forest Service 

2000a). Picloram adsorbs to clay particles and organic 

matter, but if the soil contains little clay or organic

matter, picloram is easily moved by water. Picloram has 

been reported to remain active in soil at levels toxic to 

plants for more than 1 year at typical application rates 

(SERA 2003b). The half-life of picloram in soil is 

reported to vary from 1 month under favorable

environmental conditions to more than 4 years in arid

regions (USDA Forest Service 2000a). Picloram can be 

persistent in plants. When plant parts containing

picloram degrade, they may release it into the soil,

where it can then be taken up by other plants. 

The persistence of picloram in soil is dependant on soil 

moisture and temperature. Picloram dissipates most

slowly when soils are alkaline, fine textured, and low in 

organic matter. Picloram degrades more rapidly under 

anaerobic than aerobic conditions and at lower 

application rates (USDA Forest Service 2000a). 

Higher soil concentrations of picloram result in longer 

persistence of the compound. With high application

rates, picloram may inhibit microbial activity 

(Krzyszowska et al. 1994). There does not appear to be 

a defined threshold for picloram toxicity to soil

BLM Vegetation Treatments Using Herbicides 4-20 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

microorganisms (SERA 2003b). Concentrations of 

picloram in the soil as low as 0.025 mg a.i./kg soil

appear to result in an increase in the persistence of 

picloram, which may be attributable to negative effects 

on microbial populations. 

Triclopyr 

There are two formulations of triclopyr―a triethyamine 

salt (TEA) and a butoxyethyl ester (BEE). Both

formulations degrade to triclopyr acid in soil. 

Degradation occurs primarily through microbial 

metabolism, but photolysis and hydrolysis can be

important. The average half-life of triclopyr acid in soil 

is 30 days (Tu et al. 2001). Triclopyr can be persistent

in plants. When plants containing triclopyr die and 

biodegrade, they may release triclopyr to the soil, where

it can then be taken up by other plants. 

Microbial metabolism accounts for a significant 

percentage of triclopyr degradation in soils (SERA 

2003c). In general, warm moist soils with a high organic 

content will support the highest rates of herbicide

metabolism (Newton et al. 1990 cited in Tu et al. 2001).

Johnson et al. (1995) found that microbial degradation

of triclopyr was significantly higher in moist versus dry 

soils, and at 30oC versus 15oC. They also found that 

sunlight plays a role in the rate of microbial metabolism 

of triclopyr, as microbial metabolism slowed when soil

was deprived of light. 

Triclopyr inhibited growth of four types of 

ectomycorrhizal fungi associated with conifer roots at

concentrations of 1,000 ppm and higher (Estok et al. 

1989). Some evidence of inhibition of fungal growth 

was detected in bioassays with as little as 100 ppm

triclopyr. Typical usage in forest plantations, however, 

results in triclopyr residues of only 4 to 18 ppm on the 

forest floor. 

Impacts of Other Herbicides Currently Available for 

Use 

Asulam, atrazine, fosamine, mefluidide, simazine and

2,4-DP (also known as dichlorprop) have been 

previously approved for use on public lands in many

western states (see Table 2-2), and risk assessments for 

these herbicides were provided in earlier BLM 

vegetation treatment EISs. The use of these herbicides 

by the BLM has been quite limited, with only fosamine

used in the last 7 years. Table 2-3 provides information 

on areas where use of these herbicides is appropriate. 

Atrazine, simazine, and 2,4-DP are persistent in soil, do

not adsorb well, and are generally considered mobile. 

Persistence in soil is extended under dry and/or cold

conditions. Asulam does not adsorb well; however, it is

readily biodegraded and its metabolites will adsorb to 

the soil (Vogue et al. 1994; Information Ventures, Inc. 

1995a, b, c; Mahler et al. 1998). 

Mefluidide is not strongly adsorbed to the soil and has a

half-life from 1 to 2 weeks. It does not cause adverse 

effects in soil microorganisms (Information Ventures, 

Inc. 1995d). Because fosamine is rapidly metabolized 

by soil microbes, it does not persist in soils; reported

half-lives range from 1 to 6 weeks (Han 1979 cited in

Tu et al. 2001). 

Impacts by Alternative 

The BLM proposes use of herbicides to treat vegetation

to improve ecosystem function and health, including 

soil health. However, herbicide treatments can also

affect soil fertility and function, and can kill or harm 

soil organisms. The benefits and risks to soil under each 

alternative are discussed in the following sections. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue current vegetation treatment programs in 14

western states and would treat an estimated 305,000

acres per year using both ground-based and aerial 

methods. Public lands in Alaska, Texas, and Nebraska 

are not included under this alternative. 

Under this alternative, the BLM would be able to use 

the 20 herbicides previously approved in earlier EISs. 

However, based on the recent pattern of BLM herbicide 

use, it is likely that approximately three quarters of the

area treated would involve the use of only four 

herbicides: 2,4-D, glyphosate, picloram, and tebuthiuron

(Table 2-5). It is also likely that asulam, 2,4-DP, 

atrazine, mefluidide, and simazine would not be used at

all because they have not been used in the last 7 years,

and fosamine would likely be used on less than 50 acres 

annually. 

Of the herbicides most often used by the BLM,

chlorsulfuron, picloram, and tebuthiuron are persistent

in soil for a year or more, while glyphosate and 2,4-D 

are relatively non-persistent in soil. None of these 

herbicides appears to result in severe adverse impacts to

soil. Of these, glyphosate has been shown to have little 

or no impact on biological crust cover after 1 year, 

BLM Vegetation Treatments Using Herbicides 4-21 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

while impacts from the other commonly-used herbicides 

are less well known. 2,4-D, glyphosate, picloram, 

tebuthiuron, and other herbicides used by the BLM

could benefit soil by removing invasive species and

other unwanted vegetation and allowing restoration of

native vegetation. 

Fewer acres would be treated under this alternative than

under the other alternatives. Negative effects to soils 

associated with invasive species could be greater

because fewer acres with invasive species would be

treated. Generally, invasive plants can increase the 

potential for wind or water erosion by altering fire 

frequency or producing chemicals that directly affect

soil quality or organisms. These negative effects include

increased sediment deposition and erosion, and 

alterations in soil nutrient cycling (Bossard et al. 2000). 

For example, millions of acres of grassland in the Great

Basin have been taken over by downy brome. A study 

that compared soil organisms in native grasslands after 

invasion by soft brome found that the soft brome caused

negative changes in most levels of the soil food web

(Belnap and Phillips 2001). Soft brome invasion also 

appears to change soil physical characteristics and alter 

the cycling of carbon and nitrogen (Norton et al. 2004). 

In areas with saltcedar invasions, salt accumulates in the 

soil as salt-accumulated leaves decompose. Scotch

broom and gorse can increase the nitrogen content in

soil, potentially giving an advantage to non-native 

species that thrive in a nitrogen-rich soil (Bossard et al. 

2000). Studies in Montana have shown that

sedimentation and erosion rates were 50% to 200% 

greater on sampling plots dominated by spotted 

knapweed than on plots dominated by native 

bunchgrasses (Lacey et al. 1989). In a few instances, 

invasive plants can positively affect soil through 

enrichment of certain nutrients and by providing erosion 

control. 

Under this alternative, the BLM would not be able to 

use herbicides to eliminate unwanted vegetation on

BLM lands in Texas (11,833 acres), Nebraska (6,354 

acres) and Alaska (85.5 million acres). Invasive species

are common on Texas and Nebraska public lands. In

Alaska, there are only small, scattered outbreaks of 

invasive species, and the focus of invasive species 

treatments is to control these outbreaks before they

become much larger. There is concern in Alaska

regarding the use of herbicides in sensitive 

environments, including on tundra and in boreal forests, 

but herbicide use may be appropriate where impacts to

soil and other resources would be negligible, and where

other treatment methods may not provide adequate

vegetation control (Hebert 2001). 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Under the Preferred Alternative, the BLM would be 

able to use four new herbicides in addition to 14 

previously-approved herbicides to treat approximately

932,000 acres annually across 17 western states. 

As discussed under the No Action Alternative, the use 

of herbicides would have both beneficial and adverse 

effects to soil. The area treated under this alternative 

would be approximately 3 times greater than under the 

No Action Alternative. Thus, effects would be

approximately 3 times greater. By treating a larger area

than under the No Action Alternative, the BLM would 

have a greater likelihood of reducing the number of

acres covered by weeds and other invasive vegetation

and restoring ecosystem function, to the benefit of soil 

resources. 

Based on BLM patterns of use, 2,4-D, glyphosate, 

picloram, and tebuthiuron would comprise about 70%

of the currently-used herbicides that would be used

under this alternative. The risks and benefits of using

these herbicides are discussed under the No Action 

Alternative. Approximately 10% of all treatment acres 

would be treated with the new herbicides, and of these, 

most would be treated using imazapic. Imazapic would 

be used to control downy brome, hoary cress, perennial

pepperweed, and several other invasive species that are 

known to alter soil characteristics, alter wildfire 

intensity and frequency, and increase soil erosion.

Potential effects to soil and soil organisms from the new 

herbicides appear to be minor. 

In addition to using the four new herbicides, the BLM 

would be able to use herbicides in Alaska, Nebraska, 

and Texas. Although little to no herbicide usage is 

planned for Alaska under this alternative, being able to

use herbicides in Nebraska and Texas would allow for a 

more comprehensive weed management program that

should reduce the negative effects of invasive species 

on soil in those states. 

If new herbicides are developed in the future that

provide control of unwanted vegetation superior to that 

of currently-used or proposed herbicides and with fewer 

risks to soil and other resources, the BLM would be able 

to use these herbicides to the benefit of soil resources 

BLM Vegetation Treatments Using Herbicides 4-22 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

upon completion of appropriate risk assessments and

associated NEPA analysis. 

Alternative C – No Use of Herbicides 

Under Alternative C, no herbicides would be used in the

BLM vegetation management program in 17 western

states. Some areas would not be treated by any method, 

while other areas would be treated by mechanical, 

manual, biological, or fire methods. 

Without the use of herbicides, it is likely that invasive 

plants would continue to rapidly spread, resulting in 

dramatic and potentially irreversible effects on soil 

quality through changes in organic matter content, 

diversity and abundance of soil organisms, and nutrient

and water availability. As discussed above, weeds and

other undesirable vegetation can outcompete native 

vegetation and lead to widespread incidence of fire and

other conditions that can result in increased rates of soil

erosion and loss of soil productivity. Other treatment

methods, including use of fire, machinery, and livestock

can remove vegetation, but also disturb soil, leading to

soil erosion and loss of soil quality (see PER). In many

situations, herbicides are the only, or the most effective

method for controlling invasive vegetation. For 

example, mechanical and manual methods are not

appropriate for large-scale treatments (hundreds to 

thousands of acres), and for treatments in remote areas 

that would require construction of roads and other soil

disturbing activities to allow access by mechanical

equipment. The effects of non-herbicide treatments on 

soil are discussed in the PER.

Alternative D – No Aerial Applications 

Under Alternative D, the BLM would be able to use 14

previously-approved and four newly-approved 

herbicides in 17 states, but would not be able to apply 

herbicides from aircraft. Relative to other alternatives, 

there would be a reduced risk of inadvertent 

applications from off-site drift. Subsequently, there

could be less risk to non-target soils. 

Ground-based treatments could be used to in place of 

aerial treatments in some locations. However, in other 

areas ground-based treatments would be ineffective or 

too costly to implement, including remote areas, areas 

with difficult terrain, and large expanses of woodland 

and forest. Other locations where ground-based

treatments would be ineffective include areas with

extensive coverage of invasive species (such as downy 

brome in the Great Basin). Ground-based herbicide 

applications in these areas might not be comprehensive 

enough to adequately control invasive species, and 

reinvasion would require additional treatments in the 

same area, requiring more herbicide to be used (USDI 

BLM 1991a). 

Non-herbicide methods of vegetation control may be 

substituted in areas unsuitable for ground-based

herbicide treatment. For example, where there is

sufficient fuel to carry a fire, prescribed fire could be 

used to control large areas of invasive vegetation.

Currently, vegetation management best practices use 

herbicide applications following fire to avoid reinvasion 

and promote native vegetation. In many areas, this

would be impractical without the option of aerial

application. Also, mechanical and/or biological

treatments could be used instead, but the amount of area 

that could be treated by these methods would be 

substantially less, and these treatments would disturb 

more soil than aerial herbicide treatments (see PER). 

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides 

Under this alternative, the BLM would not be able to 

use ALS-inhibiting herbicides. This group of herbicides 

has been shown to damage off-site native and crop

species, and several weed species can develop 

resistance to these herbicides, making them less 

effective. Under this alternative, four currentlyapproved herbicides (metsulfuron methyl, sulfometuron 

methyl, chlorsulfuron, and imazapyr) and one proposed

herbicide (imazapic) would not be used. The number of

acres treated under this alternative would be

approximately one-half the acreage that would be 

treated under the Preferred Alternative. In addition,

aerial herbicide treatments and herbicide treatments in

wetland, riparian, wilderness, and cultural resource 

areas would be discouraged, while more passive 

treatment methods would be promoted. 

The impacts associated with reducing the area treated

are discussed under Alternative C, and impacts 

associated with restrictions on aerial application are 

discussed under Alternative D. Impacts to soils 

associated with the use of herbicides in wetland and

riparian areas are discussed in the Wetland and Riparian 

section of this chapter. Use of herbicides in areas with

cultural resources is discussed in the Cultural Resources 

section. 

This alternative would limit activities that are known to 

impact soils and lead to invasive species establishment,

such as OHV use, minerals extraction, forestry, and 

livestock grazing. However, OHV use and livestock 

BLM Vegetation Treatments Using Herbicides 4-23 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

grazing could only be restricted to levels consistent with 

adopted BLM LUPs. Restrictions on grazing and OHV 

use would benefit soils, but in areas with extensive

infestations of weeds and other invasive vegetation, the 

full benefits of restricting grazing, OHV use, and other 

ground-disturbing activities might not be fully realized 

until invasive species were controlled and sites were

restored with native vegetation. 

An extensive knowledge of ALS-inhibiting chemical

behavior in soil appears to be lacking, including toxicity

of residues, remnants of degradation products, presence 

and release of bound residues, and potential for 

groundwater pollution (Sarmah and Sabadie 2002). At

this time, ALS-inhibiting herbicides have not been

found to be more or less toxic to soil organisms or to

demonstrate other soil effects that are notably different 

from those associated with the other herbicides. 

Under this alternative, the BLM would not be able to 

use imazapic, which is proposed for extensive control of

downy brome. This could reduce the number of acres of

downy brome treated in the Great Basin and elsewhere, 

and could increase adverse effects to soil in comparison

to the No Action Alternative.

Mitigation for Herbicide Treatment 

Impacts 

No mitigation measures are proposed for soil resources. 

Water Resources and Quality 

Introduction 

The proposed herbicide treatments have the potential to

affect water resources on or near public lands by 

altering water flows, surface water and groundwater 

quantity and quality, and rates of groundwater recharge. 

Surface water provides an important source of drinking 

water, provides habitat for fish and wildlife, and is used

for recreation. Groundwater, and especially potable 

groundwater, provides drinking water for more than

97% of the rural population without access to public 

water supplies, and provides 30% to 40% of the water 

used for agriculture (Alley et al. 1999). 

Studies have shown some groundwater supplies to be 

contaminated with herbicides and other contaminants

(total dissolved solids, metals, etc). Generally, shallow 

groundwater aquifers are at greater risk for 

contamination than deeper sources. Water quality data 

for the surface water and groundwater resources of the 

western states are available from several data sources,

as discussed in Chapter 3 under Water Resources and 

Quality. These sources were used to develop a general

assessment of water quality in the hydrologic regions of 

the western states, including Alaska, where the BLM

has substantial land management responsibility. Data

from the USEPA’s Index of Watershed Indicators 

characterizes the condition and vulnerability of each of

the 2,262 subbasins in the U.S. (Map 3-6). Information 

on general groundwater quality (based on concentration 

of TDS) was compiled from the USEPA’s National 

Water Quality Inventory (USEPA 2000a; Map 3-7). 

Based on these assessments, watershed and

groundwater water quality is poor to moderate over 

many areas in the West, primarily in areas associated 

with agricultural activities. Thus, actions that further 

deteriorate water quality or watershed health need to be

carefully evaluated before being implemented on public

lands. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

During scoping, commentors encouraged the BLM to 

evaluate the effects of herbicides on watersheds and

watershed sustainability; water supply (yield); and

infiltration, runoff, and other hydrologic processes; and

to address protection of surface water and groundwater 

quality and quantity, including conservation and 

pollution. A number of commentors pointed out the

potential impacts associated with herbicide runoff, 

overspray, and drift. Commentors suggested that the

effects of herbicide metabolites in water should be

addressed. Specific concerns regarding the impacts of 

herbicides on water quality degradation and the 

accumulation of herbicides in surface water and

groundwater were raised. Commentors also expressed 

concern about the effects of invasive species (saltcedar 

in particular) on water quality and quantity, and on 

riparian habitats. 

Standard Operating Procedures 

The following discussion addresses potential impacts 

from herbicides currently available for use by the BLM 

and from herbicides proposed for use. This assessment

of impacts assumes that SOPs (Table 2-8) designed to

reduce potential unintended impacts to water are used. 

The following SOPs are recommended to reduce 

potential unintended impacts to water quality and 

quantity from the application of herbicides: 

BLM Vegetation Treatments Using Herbicides 4-24 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

• Consider climate, soil type, slope, and 

vegetation type when developing herbicide 

treatment programs. 

• Note depths to groundwater and identify areas 

of shallow groundwater and areas of surface 

water and groundwater interaction. 

• Review hydrogeologic maps of proposed

treatment areas or conduct site reconnaissance 

to identify areas of shallow groundwater. 

• Select herbicide products to minimize impacts

to water. This is especially important for 

application scenarios that involve risk from

active ingredients in a particular herbicide, as 

predicted by risk assessments. 

• Use local historical weather data to choose the 

month of treatment. Based on the phenology of

the target species, schedule treatments based on 

the condition of the water body and existing

water quality conditions. 

• Plan to treat between weather fronts (calms)

and at the appropriate time of day to avoid high

winds that increase water movements, and to 

avoid potential stormwater runoff and water 

turbidity. 

• When possible, plan to treat shallow areas,

which are easier to control. 

• Conduct mixing and loading operations in an 

area where an accidental spill would not 

contaminate an aquatic body. 

• Do not rinse spray tanks in or near water 

bodies. 

• Do not broadcast pellets where there is danger 

of contaminating water supplies. 

• Minimize treating areas with high risk for 

groundwater contamination. 

• Maintain buffers between treatment areas and 

water bodies. Buffer widths should be 

developed based on herbicide- and site-specific 

criteria to minimize impacts to water bodies. 

• Minimize the potential effects to surface water 

quality and quantity by stabilizing terrestrial 

areas as quickly as possible following 

treatment. 

Impacts by Treatment 

Aquatic Vegetation Control Using Herbicides 

Water Quality 

The BLM currently uses four herbicides in riparian and

aquatic habitats―2,4-D, glyphosate, imazapyr, and

triclopyr―and is proposing to use diquat and fluridone 

in these areas as well. The remaining herbicides 

available to the BLM, or proposed for use, are 

registered for use on terrestrial sites. 

Herbicides applied to streams, ponds, and lakes for 

aquatic vegetation control could impact surface water 

quality if applied at concentrations that exceed label 

requirements. Based on the HHRA (see the Human

Health and Safety section in this chapter and Appendix

B), there would be low risk to drinking water in areas 

treated with diquat, fluridone, glyphosate, or imazapyr, 

even if these herbicides were accidentally spilled in 

streams, ponds, or lakes used by humans. However, risk

to drinking water associated with 2,4-D or triclopyr 

applications would be moderate to high. 

Aquatic plant control can cause a high rate of plant

decomposition and may cause rapid oxygen loss from

water that can seriously degrade water quality. The

magnitude of this effect depends on water temperature, 

lake or pond stratification, and the amount and rate of

plant decomposition. The effects can persist from a few 

weeks to an entire growing season, but are generally not 

permanent. 

The proliferation of invasive and unwanted aquatic

vegetation in surface waters can affect water quality, 

resulting in water quality degradation. Blooms of weedy 

vegetation can result in reduced drinking water quality, 

potentially limit recreation opportunities, and lead to

depletion of oxygen in water, which can degrade fish

and wildlife habitat. Infestations can block channels or 

culverts, causing flooding. Use of aquatic herbicides to

remove weedy and invasive aquatic vegetation could

reverse such infestations and greatly improve water

quality and enhance fish and wildlife habitat and 

recreational opportunities. 

Water quality degradation could result from removal of

riparian vegetation and reduction in shade. With the loss 

of shade, the resulting increase in surface-water

temperature fluctuations could drive water temperature 

beyond tolerable limits for temperature sensitive fish

and other aquatic species. 

BLM Vegetation Treatments Using Herbicides 4-25 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Water Quantity 

Applications of herbicides to aquatic systems would not 

directly modify water quantity. However, indirect

impacts to water quantity could occur if treatments 

involving the removal of unwanted aquatic vegetation 

were to reduce plant uptake of water, thereby increasing

the amount of available water. 

Terrestrial Vegetation Control Using Herbicides

Water Quality 

The four primary means of off-site movement of 

herbicides are runoff, drift, misapplication/spills, and

leaching. Surface water could be affected by any of

these means, while groundwater potentially would be 

affected only by leaching. Site conditions and 

application technique are other factors that can 

influence the effects of an herbicide on water quality. 

Runoff and Leaching. There are three physical

properties that, when combined with climate, geology,

and topography, determine the runoff and leaching

potential of an herbicide: 1) persistence, which is the 

time a chemical stays active; 2) soil adsorption, which is 

the tendency of a chemical to bind to soil particles; and

3) solubility, which is the tendency of a chemical to

dissolve in water (BPA 2000). 

Herbicides must be relatively persistent in order to have 

either leach or runoff potential (non-persistent

herbicides do not stay active long enough to create a 

risk). If an herbicide has a high soil adsorption, it is 

more likely to run off with soil movement. Soils high in 

organic content or clay tend to be the most adsorptive, 

while sandy soils low in organic content are typically

the least adsorptive (USDI BLM 1991a). If an herbicide

has low soil adsorption, it is likely to leach down

through the soil. If an herbicide is highly soluble in 

water, it is likely to leach; with low solubility, it is likely 

to run off. Tables 4-8 and 4-9 list the factors associated

with herbicide movement to groundwater, and physical

properties and off-site movement potential (leaching 

and runoff) for each currently available and proposed 

herbicide. 

Even if an herbicide has runoff or leaching potential, the

likelihood of it reaching a water body also depends on 

site characteristics. For example, if a persistent 

herbicide with a high potential for leaching to 

groundwater was used at a site with low annual

precipitation, and the depth to groundwater was over 

100 feet, the overall potential for that herbicide to reach

groundwater before degrading would be quite low. 

Conversely, the same herbicide, applied at a site with 

high annual rainfall, coarse underlying soils, and 

groundwater depths less than 100 feet would have a 

higher relative potential of reaching groundwater. 

Herbicides that are highly water soluble, relatively 

persistent, and not readily adsorbed by soil particles 

have the greatest potential for movement into the 

groundwater. Sandy soils low in organic content are the 

most susceptible to groundwater contamination (USDI 

BLM 1991a). 

Drift. Herbicide drift can degrade surface water quality.

Herbicides can reach water through drift, the airborne

movement of herbicides beyond the treatment area. 

Three factors contribute to drift: 1) application

technique; 2) weather conditions; and 3) applicator 

error. Aerial and broadcast applications are most likely 

to reach water through drift, because the herbicide is 

sprayed from a helicopter/plane or through a boom and

must settle through the air to reach the treatment area. 

Spot and localized applications are less likely to result

in drift because these applications are targeted to 

specific plants, and less herbicide is applied. Wind 

speed and air temperature, and their effect on herbicide

evaporation, affect the potential for drift. During

application when winds are over 5 mph and

temperatures are warm, the potential for drift is greater 

(BPA 2000). Peak concentrations from aerial spraying 

of fine droplets with 50- to 70-foot buffer zones 

commonly range from 0.130 to 0.148 ppm (USDA 

1988). Well-vegetated buffers can intercept herbicides 

and reduce the potential for herbicides to reach surface

water. The BLM typically uses nozzles that produce 

large droplets, and requires 100-foot or wider buffers, to

minimize the risk of herbicides drifting into surface

waters (USDI BLM 1991a). Still, buffer widths up to

1,500 feet may be required for some herbicides to 

protect sensitive aquatic species from exposure to aerial

drift (Appendix C). 

The potential for spray drift to impact perennial and

intermittent streams would be low because minimum 

10-foot (ground-hand application), 25-foot (groundvehicle), or 100-foot (aerial) buffers would be provided 

between treatment areas and water bodies (Note: The 

BLM would use information in the ERAs to develop 

more precise buffer distances based on soil,

precipitation, vegetation, and treatment characteristics;

see Appendix C). Herbicides applied near water bodies 

would have to move through the buffers, and would

likely be mixed and diluted. The potential for spray drift

to impact ephemeral streams would be 

BLM Vegetation Treatments Using Herbicides 4-26 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

TABLE 4-8 

Factors Associated with Herbicide Movement to Groundwater 

Category Properties Increasing Likelihood of Groundwater Detection 

Herbicide properties Greater mobility (lower adsorption) 

Greater pesticide persistence (lower reactivity)

Agricultural management practices

Higher pesticide use 

Increasing proximity to pesticide application areas 

Reductions in depth or frequency of tillage

Well characteristics

Decreasing well depth 

Dug or driven (versus drilled) wells 

Poorer integrity of surficial or annular well seals

Hydrogeologic and edaphic factors

Unconsolidated aquifer materials (versus bedrock) 

Decreasing depth of upper surface of aquifer 

Decreasing thickness or absence of confining layers 

Higher hydraulic conductivity 

Higher soil permeability 

Increased recharge (from precipitation or irrigation)

Younger groundwater age

Source: Barbash et al. (1999). 

greatest because there are no proposed buffers for 

these streams. Herbicides applied near ephemeral

streams are often liberated during storm surges (USDI 

BLM 1991a; Appendix C). 

Misapplications and Spills. Herbicides registered for 

use in terrestrial habitats may affect surface water and

groundwater as a result of unintentional spills or 

movement of herbicides from the upland sites into 

aquatic systems. Pollution results from herbicide

concentrations that are elevated enough to impair

water quality and the beneficial use of that water 

(USDI BLM 1991a). The potential for upland 

herbicide applications to reach water is affected by the 

herbicide’s physical properties, the application method

and rate, and site conditions (BPA 2000). 

Most experts agree that misapplications and spills are 

the leading cause of impacts on non-target resources. 

Misapplications and spills are caused by failure to

follow label instructions and restrictions, and by 

applicator carelessness. The impacts of spills depend 

on the persistence and mobility of the spill, as well as 

how quickly and thoroughly the spill is cleaned up. 

Site Conditions. Site conditions that determine the 

potential for an herbicide to intercept water include 

proximity of the treatment area to water and buffer 

width. The type of water body determines the 

potential for contamination, should an herbicide reach 

the water body. Small, still water bodies, such as

ponds and small wetlands, are the most likely to be 

affected; these water bodies move small volumes of

water and have a limited ability to disperse or dilute

contaminants. By contrast, large fast-moving rivers 

would be least likely to be affected because the 

volume and turbulence of the water would help dilute

the herbicide quickly (BPA 2000). 

Rainfall is another factor affecting the potential for 

herbicides to contaminate water bodies after 

treatment. Herbicides, particularly granular

formulations, are likely to be washed from treatment

areas toward water bodies. 

The vegetation, ground cover, or soil type between a 

treatment area and a water body can influence whether 

herbicides will reach water. Thick vegetation might 

block drift or absorb an herbicide moving through

water or ground before it reaches a water body. In

comparison, where little to no vegetation is present,

the herbicide would encounter less resistance when

washing toward the water body. 

Additional effects to water quality that could occur 

from herbicide treatments include increased nutrient 

loads to surface water and groundwater. Soluble 

nutrients can enter surface water or groundwater. 

Nutrients adsorbed to particles may be moved to water 

bodies by wind and water erosion. Nutrient

enrichment of aquatic systems can lead to algal 

blooms and eutrophication (mineral and organic 

nutrient loading and subsequent proliferation of plant 

BLM Vegetation Treatments Using Herbicides 4-27 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-9 

Herbicide Physical Properties and Off-site Movement Potential 

Physical Properties Off-site Movement Potential 

Herbicide Persistence Solubility (mg/l) Adsorption 

(Koc) 

Groundwater 

Leaching 

Surface Water 

Runoff 

Aquatic Use Herbicides 

2,4-D Moderate 3.39 x 104 19-109 Moderate Low

2,4-DP Low 50 1,000 Low Moderate

Diquat High 700,000 690 Low High

Fluridone Low 10 1,000 Low High

Glyphosate Moderate 900,000 24,000 Low High

Imazapyr Moderate >11,000 100 High Low

Triclopyr TEA 

Triclopyr BEE

Moderate

Moderate

2,100,000 

23 

20 

780 

High 

Low 

Low 

High 

Terrestrial Use Herbicides 

Asulam Low 7 55,000 Moderate Low

Atrazine Moderate 33 100 High Moderate

Bromacil Moderate 700 32 High Moderate

Chlorsulfuron Moderate 7,000 400 High Low

Clopyralid Moderate 300,000 6 High Low

Dicamba Moderate 400,000 3 High Low

Diflufenzopyr Low 5,850 18-156 High Moderate

Diuron Moderate 42 480 Moderate High

Fosamine ammonium Low Completely soluble 79 Low Low 

Hexazinone High 33,000 40 High Moderate

Imazapic High 2,200 206 Low Low

Mefluidide Low 180 200 Low Moderate

Metsulfuron methyl Moderate 9,500 35 High Moderate

Picloram Moderate 200,000 16 High Low

Simazine Moderate 6 130 High Moderate

Sulfometuron methyl Low 70 78 Moderate Moderate

Tebuthiuron High 2,500 80 High Low

Sources: USDI BLM (1991a), Vogue et al. (1994), Mahler et al. (1998), and BPA (2000). 

life), resulting in decreased dissolved oxygen contents. 

The extent and duration of effects would be dependent 

on the geographic location, and on the extent of

vegetation removal, as well as on revegetation 

management practices. The removal of large amounts of

vegetation along streams could lead to higher water 

temperatures, to the detriment of fish and other aquatic 

organisms. 

In contrast to the negative effects to water that could

result from herbicide treatments, herbicide use can 

benefit water quality if vegetation removal reduces the 

risk of fire and post-fire sedimentation. Treatment of

upland areas could reduce hazardous fuels and

contribute to long-term benefits to surface water quality 

by reducing the risk of high-intensity wildfires. In

addition, the use of herbicides to control invasive 

species in terrestrial and aquatic systems could provide

long-term benefits to water quality with the return of

more stable soils, attenuated nutrient cycling, and a

return to normal fire cycles. 

Application Technique. Application technique can also

have an impact on leaching and runoff potential.

Applications over large areas (broadcast and aerial

techniques) are more likely to result in deposition of 

herbicides in soils than spot or localized treatments, thus 

increasing the potential for runoff and leaching. 

From a watershed perspective, the concentration and 

amount of the herbicide applied can influence the risk of 

water contamination. The ratio of treated to untreated 

surface area in any given watershed is usually

sufficiently low to permit rapid dilution. This ratio is

BLM Vegetation Treatments Using Herbicides 4-28 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

much lower than that for the concentrated areas or 

blocks of land typically targeted by the BLM for 

rangeland and forestry treatments. For example, aerial

application of herbicides along a 100-foot wide ROW 

would result in about 2% to 3% of a 640-acre area 

(section) being treated. By contrast, treatment areas of 

10% to 25% per section can occur in forestry practice, 

and areas greater than 75% per section are common in

rangeland applications. Risk of direct application to

streams along ROW would increase if the linear flight

path of the applicator crossed several streams. No single 

factor can be used to anticipate the effect of herbicides 

on stream systems. By following label instructions and 

restrictions, and establishing buffers, applicators can

reduce the potential for herbicides to reach water 

bodies. 

Water Quantity 

The use of herbicides to remove vegetation could affect

water quantity by altering both the magnitude of base 

flows and the frequency and magnitude of peak flows. 

For some treatment areas, the removal of vegetation,

especially in large quantities, could improve 

groundwater recharge by limiting the amount of water

lost through sublimation or plant evapotranspiration. In

this case, base flows, which are dependent on the

quantity of groundwater discharge, would increase. 

These changes could be very minor or short-lived if the 

vegetation did not evapotranspirate or sublimate large 

proportions of precipitation, or if areas were revegetated 

quickly (Satterlund and Adams 1992). 

Under some circumstances, vegetation removal could

result in the reduction of groundwater discharge and 

base flow as a function of reduced infiltration rates. 

Reduced infiltration rates result in more surface runoff 

reaching streams and lakes immediately after a rain

event, thus increasing the velocity, frequency, and 

magnitude of peak stream flows. These changes in 

water quantity could alter the physical characteristics of 

stream channels and affect the speed of water 

movement. Any changes would last until the site was 

revegetated. 

Impacts by Herbicide 

Aquatic Vegetation Control 

2,4-D 

The salt formulation of 2,4-D is registered for use in

aquatic systems. 2,4-D is a known groundwater 

contaminant; the USEPA has set a maximum 

concentration of 0.07 mg/L as a permissible level for 

this herbicide in potable water. 

Concentrations of up to 61 mg/L 2,4-D have been 

reported immediately following direct application to

water. Based on label directions, treated water should 

not be used for irrigation if the water could be

consumed by humans. Concentrations as low as 0.22 

mg/L can damage sensitive plants (Que Hee and 

Sutherland 1981 cited in Tu et al. 2001). 

There are conflicting conclusions regarding

biodegradation of 2,4-D in aquatic systems (Que Hee 

and Sutherland 1981 and Wang et al. 1994 cited in Tu et 

al. 2001). Biodegradation can take place in bottom

sediments if the appropriate microbial population is 

present and the pH level is sufficiently high, but it is not 

likely to occur in the water column. Under acidic 

conditions, when microbial activity is inhibited 

(Sandmann et al. 1988 cited in Tu et al. 2001), 

biodegradation may not occur. Differences in reported 

half-lives of 2,4-D may arise from differences in the

microbial populations in treatment areas and the

influence of plants on soil biological and chemical

properties (Boucard et al. 2005). 

2,4-D changes form and function with changes in pH

(Que Hee and Sutherland 1981 cited in Tu et al. 2001). 

In alkaline waters, 2,4-D takes a negatively-charged

form that is water-soluble and remains in the water 

column. In water of a lower pH, 2,4-D remains in a

neutral molecular form, increasing its potential for 

adsorption to organic particles in water and increasing 

its persistence. 2,4-D is predicted to adsorb to 

suspended particles in muddy waters with a fine silt

load (Que Hee and Sutherland 1981 cited in Tu et al. 

2001), but little adsorption has been observed in the 

field (Halter 1980 cited in Tu et al. 2001). 

In terrestrial applications, most formulations of 2,4-D 

do not bind tightly with soils, and therefore have a 

moderate potential to leach into the soil column and to

move off site in surface or subsurface water flows 

(Johnson et al. 1995 cited in Tu et al. 2001). In a study 

on groundwater expressed as spring flow, 2,4-D was 

detected in 7% of the samples (Wood and Anthony 

1997). 

Diquat 

Diquat would be applied to remove emergent, floating, 

or submerged aquatic vegetation. In aquatic systems, 

diquat (ionic) adsorbs to sediment, suspended solids, 

and aquatic vegetation, and becomes immobilized

BLM Vegetation Treatments Using Herbicides 4-29 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

(Simsiman and Chesters 1976). Thus, diquat is

ineffective in turbid waters. Loss of diquat from aquatic

systems, both through photolysis and biodegradation, is 

possible, but only when the herbicide is not adsorbed to

solid surfaces. When adsorbed, the herbicide is 

protected from biodegradation and photolysis (Howard 

1991). Aquatic half-lives of 1 to 2 days have been

reported for diquat, as a result of sorption onto

particulates and sediments (National Library of

Medicine 2002). Diquat is a known groundwater 

contaminant, and the USEPA has set a maximum 

concentration level of 20 μg/L for potable water. It has a 

moderate potential to leach into the groundwater and a 

high potential to be transported in surface water runoff. 

Fluridone 

Fluridone would be applied to ponds, lakes, canals, and

reservoirs, but has limited use in flowing water because

it works through contact maintained over several weeks. 

Water quality is not degraded when fluridone is used at 

a concentration of less than 20 ppb, and it is generally 

considered safe to use in areas where swimming or

fishing occur (Washington Department of Ecology 

2002). Whole-lake treatments using fluridone are 

possible because the herbicide does not cause a rapid 

plant kill, which could result in oxygen-depleted water 

and reduced water quality. 

Photodegradation in aquatic systems is an important

loss pathway for fluridone (British Crop Protection 

Council and The Royal Society of Chemistry 1994). 

Fluridone is stable to hydrolysis, volatilizes slowly from 

water, and adsorbs to suspended solids and sediments 

(USEPA 1986; Lyman et al. 1990; Tomlin 1994; 

Mackay et al. 1997; ENSR 2005g). Desorption from 

sediments followed by photolysis is reported to be a loss 

pathway (ENSR 2005g). Biodegradation can also

remove fluridone from aquatic systems. Aquatic 

dissipation half-lives from 4 days to 9 months 

(anaerobic sediments) have been reported. Fluridone has 

low potential to leach to groundwater and is not known 

to contaminate groundwater. It does have high potential

to be transported in stormwater runoff. 

Glyphosate 

Glyphosate, which is registered for aquatic use, would

be applied to wetland and emergent aquatic vegetation.

Glyphosate dissipates rapidly from surface water 

through adsorption to organic substances and inorganic 

clays and by biodegradation (Folmar et al. 1979; Feng

et al. 1990; Zaranyika and Nydandoro 1993; Paveglio

1996 cited in Tu et al. 2001). It does not photodegrade, 

and in water has an estimated half-life of 12 days to 10

weeks. It is generally considered immobile because of 

its adsorption characteristics; however, it is a known

groundwater contaminant. The USEPA has set a 

maximum concentration limit of 0.7 mg/L as a 

permissible level for glyphosate in potable water. 

Strong adsorption to particles slows microbial

degradation, allowing glyphosate to persist in aquatic 

environments. Glyphosate can be inactivated by

adsorption if mixed with muddy water (Tu et al. 2001). 

Residues adsorbed to suspended particles are

precipitated into bottom sediments where they can 

persist until biodegraded or be released into water 

(Goldsborough and Brown 1993 and Extension 

Toxicology Network 1996a cited in Tu et al. 2001). 

Glyphosate is unlikely to enter waters through surface 

runoff or subsurface flow because it binds strongly to

soils, except when the soil itself is washed away by

runoff; even then, it remains bound to soil particles and 

generally unavailable (Rueppel et al. 1977 and Malik et

al. 1989 cited in Tu et al. 2001). More recent studies 

found solution-phase glyphosate in 36% of 154 stream

samples, while its degradation product, 

aminomethylphosphonic acid, was detected in 69% of 

the samples. The highest measured concentration of 

glyphosate was 8.7 μg/L, well below the USEPA’s 

maximum concentration limit of 700 μg/L. 

Glyphosate may stimulate algal growth at low 

concentration; Austin et al. (1991) have suggested that 

this could contribute to eutrophication of waterways. An

increase in periphyton concentrations in artificial

streams has been reported by Austin et al. (1991), and 

Wong (2000) reported an increase in chlorophyll-a 

synthesis by a green microalgae (Scenedesmus 

quadricauda) at a concentration of 0.02 mg/L (cited in 

SERA 2003a). 

Imazapyr

Imazapyr is registered for use in aquatic systems,

including brackish and coastal waters, to control 

emergent, floating, and/or riparian and wetland plants. 

Imazapyr is water soluble and potentially mobile

(SERA 2004d). Imazapyr is rapidly degraded by 

sunlight in aquatic solutions, with a half-life of

approximately 2 days that decreases with increasing pH 

(Mallipudi et al. 1991 and Mangels 1991 cited in Tu et 

al. 2001). Imazapyr does not appear to degrade in

anaerobic systems, such as wetland soil or lake or pond 

sentiments, and will bind strongly to peat (American

Cyanamid 1986 cited in Tu et al. 2001).

BLM Vegetation Treatments Using Herbicides 4-30 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

In their literature review of imazapyr, Tu et al. (2001) 

found no reports of imazapyr contamination in water 

despite its potential for mobility. It is not known to be a

groundwater contaminant. Battaglin et al. (2000) stated

that little is known about its occurrence, fate, or

transport in surface water or groundwater. In one study, 

imazapyr (from terrestrial applications) was detected in

4% of the 133 samples taken from streams, but was not 

detected in reservoirs or groundwater. 

Triclopyr 

The two formulations of triclopyr, a triethyamine salt

and a BEE, behave very differently in water. Both

formulations are used to control woody riparian

vegetation. However, only the triethylamine salt

formulation of triclopyr (known as Garlon 3A®

, now 

marketed as Renovate 3®), is registered for use for 

selective control of submersed aquatic plants. Both 

formulations readily degrade to the acid form, which is

the active form in plants. 

The triethyamine salt formulation of triclopyr is soluble

in water and photodegrades in several hours with 

adequate sunlight. Field studies have shown that 

triclopyr (salt formulation) and its metabolites dissipate

from water, with half-lives ranging from 0.5 to 10 days

and sediment dissipation half-lives ranging from 3 to 13 

days (Petty et al. 2003). Johnson et al. (1995) found

triclopyr acid in water had a half-life due to photolysis 

of 1 to 12 hours (cited in Tu et al. 2001). The rate of

degradation in water is generally dependent on water 

temperature, pH, and sediment content. 

No adverse effects on water quality were observed

following triclopyr triethyamine salt applications in two 

studies of whole-pond applications in closed systems 

(no water exchange; Petty et al. 2001). Results of these 

studies were comparable with those of triclopyr 

dissipation studies conducted in reservoirs, lakes, and 

river systems, and indicated that the degradation and 

dissipation of triclopyr and its metabolites are similar in

representative systems throughout the U.S. (Petty et al. 

2001). 

The BEE formulation (terrestrial use only, not 

registered for aquatic application) is not water-soluble 

and can partition into organic materials and be 

transported to sediments, where it is persistent. 

Alternatively, bound ester forms can degrade through 

hydrolysis or photolysis to triclopyr acid (Smith 1976 

cited in Tu et al. 2001), which will diffuse into the water 

column and continue to degrade (Tu et al. 2001). The

fate and effects of triclopyr BEE were investigated in a 

first-order forest stream (Thompson et al. 1995). 

Measurements of triclopyr in stream samples indicated 

that the ester form was rapidly converted to the acid,

and that partition to organic materials occurred as 

chemical pulses moved downstream.

Assessment of Impacts of Herbicides Used for

Terrestrial Vegetation Control 

Bromacil 

Bromacil is mobile in soil and can reach groundwater 

and surface water. It can be persistent in most aquatic

environments because it is stable to hydrolysis, and 

photodegradation occurs rapidly only under alkaline 

conditions (ENSR 2005b). Bromacil is a known

groundwater contaminant, and the USEPA standard for 

drinking water is 90 μg/L. The environmental hazards 

section of current product labels includes a groundwater 

advisory warning users not to apply bromacil in areas 

with permeable soils in order to protect water quality. 

Biodegradation is a major loss mechanism in aerobic

and anaerobic aquatic systems. Bromacil is not expected

to partition to suspended particles or sediments in

aquatic systems, but will remain dissolved in the water 

column and has a high potential to leach into the

groundwater. 

Chlorsulfuron 

Chlorsulfuron is persistent and mobile in some soils. In

aquatic environments, the environmental fate of

chlorsulfuron is related to pH and temperature.

Hydrolysis rates are fastest in acidic waters and slower 

in more alkaline systems (Sarmah and Sabadie 2002).

As hydrolysis rates drop, biodegradation becomes the 

mechanism affecting the breakdown of chlorsulfuron.

Photodegradation is not an important loss mechanism in

natural systems, although photodegradation has been 

observed under laboratory conditions. Aquatic 

dissipation half-lives from 24 days to more than 365

days have been reported (ENSR 2005c), with a shorter 

time reported for flooded soil (47 to 86 days) than 

anaerobic aquatic systems (109 to 263 days; SERA 

2004a). Chlorsulfuron is not known to be a groundwater 

contaminant, but has a high potential to leach into the 

groundwater. Chlorsulfuron has low potential to be 

transported in surface water; in a large study of surface

water, chlorsulfuron was detected in only 1% of the 133

samples taken from Midwest streams (Battaglin et al. 

2000). 

BLM Vegetation Treatments Using Herbicides 4-31 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Clopyralid 

Clopyralid does not appear to bind tightly to soil and 

will leach under favorable conditions (SERA 2004b). 

However, leaching and subsequent contamination of 

groundwater appear to be minimal, which is consistent

with a short-term monitoring study of clopyralid in

surface water after an aerial application (Rice et al. 

1997a cited in SERA 2004b). Clopyralid is not known 

to be a common groundwater contaminant, and no

major off-site movement has been documented.

Clopyralid does not bind with suspended particles in 

water; biodegradation in aquatic sediments is the main

pathway for dissipation. The average half-life of

clopyralid in water has been measured at 9 and 22 days

(Dow AgroSciences 1998). 

Dicamba 

Because dicamba is mobile in soil, terrestrial application 

of this herbicide can result in groundwater and surface 

water contamination under conditions that favor such

activities. Biodegradation is the major mechanism for 

dicamba degradation in water. Although 

photodegradation occurs, it is not the major loss 

process. Hydrolysis and sediment adsorption are not

significant loss mechanisms (Howard 1991). Dicamba 

is a known groundwater contaminant, and has a high 

potential to leach into groundwater. The USEPA has set

health advisory concentration levels for dicamba (e.g. 

300 μg/L for 1-day exposures), but has not set

maximum concentration limits for potable water. 

Dicamba is registered for use on ditch banks, but should 

not be applied directly to water. 

Following herbicide applications for 1 to 24 years, there

were no detectable residues of dicamba in groundwater 

at two long-term tillage sites and one long-term 

manured site in Alberta (Miller et al. 1995). However, a 

regional study of pesticides in shallow groundwater in

Delaware, Maryland, and Virginia detected dicamba in

groundwater at low concentrations, generally less than 3

μg/L (Koterba et al. 1993). 

Diflufenzopyr 

Diflufenzopyr appears to be soluble, with transportation

from surface runoff following application, particularly

when diflufenzopyr is applied on soils with neutral to 

alkaline pH. However, based upon proposed uses, fate

characteristics, and model predictions, the USEPA does 

not include diflufenzopyr among constituents that occur 

in significant quantities in drinking water (USEPA 

1999c). Diflufenzopyr is not a known groundwater 

contaminant. 

Biodegradation, photolysis, and hydrolysis are 

important mechanisms in removing diflufenzopyr from 

aquatic systems. Its half-life is less than 1 month, with

hydrolysis and photolysis rates higher in acidic 

environments. The aquatic dissipation half-life for 

diflufenzopyr is 25 to 26 days in aerobic and 20 days in

anaerobic conditions. Diflufenzopyr’s expected half-life

in small ponds is estimated at 24 days. These factors 

suggest that diflufenzopyr would be removed from an

aquatic environment relatively rapidly if contamination

occurred (USEPA 1999c). 

Diuron

Diuron is a known surface water and groundwater 

contaminant. The USGS National Ambient Water 

Quality Assessment Program analyzed pesticide 

occurrence and concentrations for major aquifers and

shallow groundwater in agricultural areas and found

diuron in 71% of 2,608 samples. The maximum 

concentration of diuron was 0.34 ppb. The USEPA 

recently (February 2005) placed diuron on the drinking

water contaminant candidate list. Diuron is currently 

labeled for use on ditch banks, but should not be applied 

directly to water. 

In aquatic systems, biodegradation and

photodegradation appear to be the primary loss

mechanisms for diuron. An aquatic biodegradation halflife of 33 days has been reported for aerobic systems. 

Aquatic dissipation half-lives have been reported

ranging from 3 to 10 days in anaerobic pond sediment

to 177 days in a drainage ditch. Diuron is stable to

hydrolysis and is unlikely to volatilize from aquatic 

systems (USEPA 2001a). Diuron is expected to adsorb

to suspended solids and sediments (National Library of

Medicine 2002). 

The principal product of biodegradation is 3,4-

dichloraniline (3,4-DCA), which also persists and 

exhibits higher toxicity than diuron (Tixier et al. 2002;

Giacomazzi and Cochet 2004). In areas where diuron is

used for crop production, monitoring has shown high

concentrations of 3,4-DCA in small streams. 3,4-DCA 

was detected year-round in surface water (333

detections, 13 non-detections), with a range from 0.05 

ppb (detection limit) to 26 ppb; the majority of the 

sample detections were less than 1 ppb (USEPA 2001a). 

At a poorly drained field site along an intermittent

stream in Oregon, diuron and its transformation product, 

DCPMU (3-(3,4-dichlorophenyl)-1-methyl-urea), were 

BLM Vegetation Treatments Using Herbicides 4-32 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

detected in the stream at a maximum concentration of 

28 μg/L, and were detected in shallow groundwater 

immediately adjacent to a tributary stream at 2 to 13

μg/L. Movement through soil transported the herbicide

and its metabolite to the stream, while surface runoff 

removed less than 1% of the applied herbicide (Field et

al. 2003). 

Hexazinone 

Hexazinone and its degradates persist, are highly

mobile, and are readily washed into surface waters.

Hexazinone has been identified as a groundwater 

contaminant in Hawaii, Minnesota, Georgia, Arkansas,

Florida, Maine, and North Carolina. The USEPA Office

of Water has issued a lifetime health advisory, which

sets a maximum concentration level of 0.21 mg/L for 

hexazinone in drinking water. In addition, the USEPA 

requires a groundwater advisory on all product labels 

stating that hexazinone must not be used on permeable 

soils. In areas where irrigation water is contaminated 

with hexazinone or where groundwater discharges to 

surface water, hexazinone residues in water could pose 

a threat to plants. Hexazinone is labeled for use on ditch

banks, but should not be applied directly to water. 

In surface water, hexazinone resists photodegradation 

(Neary et al. 1983 cited in Tu et al. 1991). Hexazinone 

does not bind strongly to particulates or sediments. The 

main method of degradation is by microorganisms in

soils. The average half-life of hexazinone in soils and

water is 90 days (Tu et al. 2001). Hexazinone has been 

detected in streams near terrestrial application sites up

to 30 days after treatment, and reported in runoff up to 6 

months post-treatment in a forestry dissipation study

(Neary and Michael 1996; Michael et al. 1999). Mayack

et al. (1982) and Neary et al. (1984, 1993 cited in Tu et 

al. 2001) concluded that hexazinone was diluted in the 

mainstream flow to very low concentrations in forested

watersheds. 

I

s

f

mazapic

In aquatic systems, imazapic rapidly photodegrades, 

with a half-life of 1 to 2 days (Tu et al. 2001). Since 

aerobic biodegradation occurs in soils, aerobic 

biodegradation is likely important in aquatic systems. 

Aquatic dissipation half-lives have been reported from

30 days (water column) to 6.7 years in anaerobic

sediments (SERA 2004c). Little is known about the 

occurrence, fate, or transport of imazapic in surface

water or groundwater (Battaglin et al. 2000). However, 

according to the herbicide label for Plateau

®, in which 

Imazapic is the active ingredient, it is believed to be a

groundwater contaminant (BASF 2004). 

Met ulfuron Methyl 

Metsulfuron methyl is stable to hydrolysis at neutral and 

alkaline pHs and has a half-life of 3 weeks in acidic 

systems (Extension Toxicology Network 1996b). The 

persistence of metsulfuron methyl (initial concentration 

10 μg/L) was investigated using in situ enclosures in a

woodland/boreal forest lake, and the half-life was 

estimated at approximately 29 days (Thompson et al.

1992). Adsorption to sediments and suspended solids is 

not expected to be an important fate (USDA 1995). 

Little is known about the occurrence, fate, or transport

of metsulfuron methyl in surface water or groundwater

(Battaglin et al. 2000). Metsulfuron methyl is not 

known to be a groundwater contaminant, although it has 

a high potential to leach into the groundwater. 

Picloram 

Picloram can move off site through surface or

subsurface runoff, and has been detected in the

groundwater of 11 states (Howard 1991 cited in

EXTOXNET 1996c). The USEPA’s maximum 

concentration level for picloram in potable water is 0.5

mg/L. Picloram does not bind strongly with soil 

particles and is not degraded rapidly in the environment

(Tu et al. 2001). Concentrations in runoff have been 

reported to be great enough to damage crops, and could

cause damage to certain submerged aquatic plants 

(Forsyth et al. 1997 cited in Tu et al. 2001). Therefore,

picloram should not be applied near waters used for 

irrigation or adjacent to areas with aquatic species of 

concern. 

Picloram may degrade through photolysis, especially in

non-turbid and moving water. Woodburn et al. (1989) 

found that the half-life of picloram in water was 2 to 3

days (cited in Tu et al. 2001). Maximum picloram

runoff generally occurs following the first significant

rainfall, after which runoff concentrations drop to levels 

that persist up to 2 years post-application (Scifres et al. 

1971; Johnsen 1980; Mayeux et al. 1984; and Michael 

et al. 1989 cited in Tu et al. 2001). 

Sul ometuron Methyl 

Sulfometuron methyl degrades quickly by hydrolysis in

acidic water, but is stable in neutral water. 

Biodegradation and photolysis are major loss pathways

in aquatic systems, where hydrolysis rates generally are 

slow. Aquatic dissipation half-lives are estimated at 1 to

BLM Vegetation Treatments Using Herbicides 4-33 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

3 days to 2 months in aerobic systems, and several

months in anaerobic sediments (Extension Toxicology

Network 1996d). Little is known about its occurrence, 

fate, or transport in surface water or groundwater in the

U.S. (Battaglin et al. 2000). Sulfometuron methyl is not 

known to be a groundwater contaminant. In one surface 

water study, sulfometuron was detected in 2% of 133

samples taken from streams.

Tebuthiuron 

Tebuthiuron persists in the environment, perhaps 

because of its low sorption affinity to soil. Tebuthiuron 

can be used on ditch banks, but should not be applied

directly to water. In one study of 71 streams,

tebuthiuron was detected in 16% of 134 stream samples 

taken, with concentrations up to 0.076 μg/l, but was not 

detected in groundwater (Battaglin et al. 2001). In 

water, tebuthiuron is resistant to hydrolysis and

photolysis, although some photodegradation has been

reported at a pH of 9 (National Library of Medicine 

2002). Tebuthiuron is expected to slowly biodegrade in

aquatic systems. Aquatic dissipation half-lives are 

estimated to be longer than 1 month under aerobic 

conditions, and longer than 12 months under anaerobic 

conditions (USEPA 1994a). 

Other Herbicides Previously Approved for Use on

BLM Lands 

Asulam, atrazine, fosamine, mefluidide, simazine, and

2,4-DP (also known as dichlorprop) are currently 

approved for use on public lands. However, the 

historical use of these herbicides by the BLM has been 

quite limited, with only fosamine used in the last 7

years. 2,4-DP is registered to control aquatic weeds in 

ditches and for upland purposes, is mobile in soils, and 

has been detected in surface water and groundwater 

(National Library of Medicine 2002). Both atrazine and 

simazine persist in rainwater, groundwater, and surface 

water. Mefluidide and fosamine are not commonly 

known to contaminate groundwater or surface water. 

Fosamine adsorbs to soil and biodegrades, making it 

less likely to be mobilized. However, upon reaching

water it is generally stable until it partitions into 

sediments (Tu et al. 2001). 

Impacts by Alternative 

The BLM would focus treatment efforts on watersheds

that provide opportunities for watershed improvement

and protection (USDI BLM 2000a). In addition, the 

BLM would strive to increase the number of properly 

functioning wetland/riparian areas and uplands to 

benefit water quality. 

Much of this work would be directed at hazardous fuels 

and weed reduction to improve watershed function and

water quality and reduce the risk of catastrophic fires.

When fire clears the vegetation, the soils that were

anchored by root systems become vulnerable to wind 

and water erosion. When soils are carried into lakes and 

streams, water quality diminishes as a function of 

increased sedimentation and turbidity (USDI BLM

2000d). Work would also be directed at controlling 

invasive vegetation, such as pinyon and juniper that

have overtaken many native shrub and grassland 

communities. These trees diminish water that native

species are reliant upon and can cause increased soil 

erosion (USDI BLM 1999). 

Watersheds dominated by annual grasses such as downy 

brome offer far less protection from wildland fire and

erosion than those dominated by native grasses. The 

reduced cover provided by annuals allows more rainfall

to strike the soil surface, loosening soil particles and

forming a seal over the pores at the soil surface. As the

pores seal, infiltration decreases, which leads to 

increased runoff and loss of soil moisture. Eventually, 

soils are transported to streams and other aquatic bodies,

increasing sedimentation and reducing water quality. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would treat

an estimated 305,000 acres per year using the current

vegetation treatment programs in 14 western states. This

alternative is a continuation of the current vegetation 

management program using both ground-based and 

aerial treatment methods. Public lands in Alaska, 

Nebraska, and Texas have not been part of the herbicide 

program historically, and would not be included under 

this alternative. 

Impacts to surface water and groundwater quality and

quantity would be similar to impacts from the ongoing 

program. Under the No Action Alternative, it is unlikely 

that 2,4-DP, asulam, atrazine, mefluidide, and simazine 

would be used, and fosamine might only be used on a

limited basis (<100 acres annually). Of these herbicides, 

atrazine, simazine, and 2,4-DP are known groundwater 

contaminants. 

Based on historic use, 2,4-D, glyphosate, picloram, and

tebuthiuron would constitute approximately 70% of

herbicide use. All of these herbicides are known 

BLM Vegetation Treatments Using Herbicides 4-34 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

groundwater contaminants, although only glyphosate 

has high surface water runoff potential. In addition, of 

the other herbicides proposed for use, diquat, diuron, 

bromacil, dicamba and hexazinone are also known to be 

groundwater contaminants. For most terrestrial 

applications, herbicide concentrations are diluted as 

they move from the treated site to downgradient

locations (Michael 2000). Out of 236 studies of

pesticide contamination of surface waters in drainage 

basins throughout the U.S., none reported pesticide 

concentrations exceeding USEPA safe levels for human

health, except where chemicals were applied directly to 

or spilled into the stream channel (Larson et al. 1997). 

Under the No Action Alternative, Overdrive®, diquat, 

fluridone, and imazapic would not be available for use. 

Both diquat and fluridone are considered effective 

against the invasive plant Eurasian watermilfoil, as well

as other problematic aquatic plants (Washington 

Department of Ecology 2002, Skogerboe 2003). 

Triclopyr would be the only herbicide under this 

alternative available to treat submersed vegetation. 

Prohibiting the use of two proposed herbicides available 

for treatment of aquatic plants would potentially allow 

for continued negative effects on water quality 

associated with some forms of weeds and invasive 

aquatic vegetation, potentially resulting in degraded fish

and wildlife habitat and limited recreation opportunities. 

Fewer acres would be treated under this alternative than

under the other alternatives. Therefore, impacts on

water quality and quantity from herbicides would be

more limited. However, continued impacts to water 

quality and quantity from invasive plant species over 

the untreated areas could potentially occur.

Alternative B – Expand Herbicide Use and Allow 

For Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Under the Preferred Alternative, an estimated 932,000 

acres per year would be treated across 17 western states.

Out of all the alternatives, this is the largest acreage 

proposed for treatment. Therefore, benefits and risks to

surface water and groundwater would be greater than 

under the other alternatives. It is estimated that several

thousand acres of public lands are being newly infested

by noxious invasive weeds each day. The result is

damage to watersheds and subsequent deterioration in

water quality and quantity. Until more acres are treated, 

it will be impossible for the BLM to bring the spread of

invasive plants down to a reasonable level by locating 

and treating new infestations, and reducing the size of

existing infestations. 

Under the Preferred Alternative, herbicide use in

Alaska, Nebraska, and Texas would be allowed, 

although little or no herbicide treatment is planned for 

Alaska. Use in Nebraska and Texas would allow for a 

more comprehensive weed management program that

would help reduce the negative effects of invasive 

species in those two states. 

This alternative would prohibit the use of 2,4-DP, 

asulam, atrazine, fosamine, mefluidide, and simazine, 

but would allow four new herbicides (Overdrive®, 

diquat, fluridone, and imazapic) to be used, in addition 

to approved herbicides. Approximately 10% of 

treatment acres would be treated using these new

herbicides. Diquat and fluridone could be directly

applied in aquatic systems to control unwanted 

submersed aquatic vegetation. Approval of diquat and

fluridone would provide new capabilities for controlling

invasive aquatic plants and could provide benefits to

water quality if invasive aquatic plants were eliminated. 

Fluridone, in particular, has been effective at controlling 

Eurasian watermilfoil without resulting in impacts to

drinking water quality or recreation (Washington

Department of Ecology 2002). 

Both dicamba and diquat are known groundwater 

contaminants. However, increased protection of 

groundwater could be possible if imazapic (not known

to contaminate groundwater) was used for treating

terrestrial species in place of one of these known 

groundwater contaminants. Diflufenzopyr is not known

to contaminate groundwater, but has a high potential to 

leach to groundwater. Except for fluridone, which has a

high potential for surface water runoff, the proposed 

herbicides have low potential to flow to aquatic bodies

in stormwater runoff. 

Alternative C – No Use of Herbicides 

No herbicides would be used in the BLM vegetation

management program under Alternative C. Some areas 

would not be treated, while other areas would be treated

by mechanical, manual, or biological methods, or fire. 

Without treatment, land degradation would accelerate, 

leading to poorer water quality. As discussed in the 

PER, other treatments also impact water quality and

quantity, with fire and mechanical treatments having the

greatest effects. However, the risks of impacts to surface

water and groundwater quality would be low under this

alternative. 

The only alternatives to herbicide treatment of

submersed vegetation are mechanical or manual 

removal; water drawdown on controlled reservoirs, 

BLM Vegetation Treatments Using Herbicides 4-35 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

lakes, and ponds; and flooding with salt or brackish

water. These treatments generally are not as effective as

chemical treatments at controlling many invasive 

aquatic plants (Aquatic Ecosystem Restoration 

Foundation 2004, USDI BLM 2007a). Without 

effective treatment, some invasive aquatic plants would 

go largely uncontrolled, potentially resulting in

degraded water quality and reduced quantity. 

Alternative D – No Aerial Applications 

Under Alternative D, herbicide treatment with four 

newly-approved herbicides and the previously-approved 

herbicides would be allowed in 17 states. These 

herbicides would be applied by ground application 

methods. The estimated area treated would be 

approximately 529,000 acres per year. Ground-based

herbicide treatments could be used to replace aerial

treatments in some locations, and non-herbicide 

treatment methods could be substituted in some areas 

unsuitable for ground-based herbicide treatment. 

Aerial application has the advantage of treating large 

areas or areas of difficult terrain. However aerial

application is more likely to result in misapplications or 

drift, and thus negatively impact water quantity and 

quality. The extent of the impact would depend on the

weather, the size and location of the treatment area, the

use of buffers, and the kind and concentration of 

herbicide used. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides

Under Alternative E, the BLM would not be able to use

ALS-inhibiting herbicides (chlorsulfuron, imazapyr, 

imazapic, metsulfuron methyl, and sulfometuron

methyl). Approximately 466,000 acres would be treated 

under this alternative. Aerial and broadcast treatments 

and treatments in wetland, riparian, wilderness, and

cultural resource areas would be discouraged, while

more passive treatment methods would be promoted. Of 

the six herbicides registered for aquatic use, imazapyr is 

ALS-inhibiting and would not be allowed. Of the four 

newly proposed herbicides, imazapic is ALS-inhibiting

and would not be allowed. 

Impacts associated with size of treatment area are 

discussed under Alternative C; impacts associated with

aerial applications are discussed under Alternative D. 

Because of the smaller treatment acreage, the negative 

effects of weedy and invasive species on water quality 

and quantity could be greater than under the other 

alternatives. The risks to water quality and quantity 

from use of herbicides would be lower than under the 

Preferred Alternative. Fewer treatments in wetland and 

riparian areas could correspond to greater impacts to

surface water quality if wetland areas containing 

substantial infestations of invasive species were to

remain untreated. 

Currently, little is known about the occurrence, fate, or 

transport of ALS-inhibiting herbicides in surface water 

or groundwater in the U.S. (Battaglin et al. 2000, 2001). 

An extensive study of Midwestern streams, reservoirs, 

and groundwater in 1998 found relatively low 

concentrations of sulfonylurea and imidazolinone 

herbicides in 83% of 133 samples from streams, in 6 of

8 reservoir samples, and 5 of 25 groundwater samples. 

These results indicate that some ALS-inhibiting

herbicides are mobile and may reach surface water and 

groundwater. Therefore, contamination of water 

resources by ALS-inhibiting herbicides would

potentially be less than under the other alternatives. 

Mitigation for Herbicide Treatment 

Impacts 

The following mitigation measure should be considered 

to reduce, minimize, or mitigate impacts to water 

resources from the use of herbicides: 

• Establish appropriate (herbicide specific) 

buffer zones to downstream water bodies, 

habitats, and species/populations of interest

(see Appendix C, Table C-16). 

Wetland and Riparian Areas 

Introduction 

The BLM manages over 23 million acres classified as

riparian or wetland. Wetland and riparian areas in the 

western U.S. and Alaska are influenced by human 

activity, natural disturbance, and local physical and

biological conditions. Invasive plant species degrade 

wetland and riparian area function and present a 

challenge to vegetation management. An estimated

59,000 acres of wetland habitat and 16,500 stream miles 

on BLM lands lack characteristics necessary for “high” 

functioning wetland and riparian habitats (USDI BLM

2006d). Invasive plant species are one cause of 

degradation of wetland function. 

The proposed herbicide treatments could cause longterm alterations to vegetation, hydrology, or soils to the

extent that a specific area no longer functions properly 

BLM Vegetation Treatments Using Herbicides 4-36 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

or is fragmented, the biodiversity of high quality areas is

reduced, or special status wildlife or plants are harmed

or displaced. Treatments would be beneficial, as they 

contribute to removal or control of invasive species and

replacement with native species. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

During scoping, concerns pertaining to treatment of 

wetland and riparian areas included protection of unique 

areas and areas of high biological importance;

management of invasive species (e.g., saltcedar) that

provide habitat for species that use aquatic and riparian

areas; and the need to maintain species diversity and 

sensitive areas like vernal pools. One proposed 

treatment alternative included a suggestion to defer 

treatments in wetland and riparian areas where longterm control of invasive species is unlikely. 

Factors that Influence the Fate,

Transport, and Persistence of 

Herbicides in Wetland and Riparian 

Areas 

If applied directly to wetlands and riparian areas, 

herbicides dissipate by transport through water or wind, 

through chemical or biological degradation, or through

adsorption and immobilization in soils. When herbicides 

are applied to well-drained areas, adjacent wetlands and

riparian areas can play a critical role in filtering 

herbicides from runoff, through physical trapping and 

through chemical and biological processes. These affect

herbicide availability, phytotoxicity, and fate and 

transport (Anderson 1982). 

Saturated wetland soils have chemical and biological

characteristics that are different from well-drained 

upland soils, including oxidation-reduction status, pH, 

and high organic content. For example, oxygen 

depletion of saturated soils facilitates oxidationreduction, reductive chemical processes, and anaerobic 

microbial processes. Soil pH can be closer to neutral in

wetland soils than in well-drained soils, or wetland soils 

may be more acidic than well-drained areas if peat is 

present. The characteristics of wetland soils affect their 

capacity to adsorb, transport, and transform herbicides.

The extent of the effects on herbicide fate is dependent

on the duration of saturation, soil temperature, the kind

and amount of organic matter, and the nature and

content of reactive chemicals present in the soil. For 

example, some chemical processes that degrade 

herbicides only occur to measurable degrees when soils 

are anaerobic or lack free oxygen. 

The rate of breakdown in anaerobic systems can be 

estimated by the measured anaerobic half-life (Table 4-

10). Generally, anaerobic degradation processes are 

much slower than the degradation processes in welldrained soils where oxygen is present. 

Methodology for Assessing Impacts to 

Wetland and Riparian Areas 

The BLM reviewed the literature and findings from 

ERAs to assess the impacts to aquatic plant species 

from the use of herbicides (ENSR 2005b-k, SERA 

2005a). The ERA methods and results for aquatic and

terrestrial vegetation are summarized in the Vegetation 

section of this chapter. Methods used by the BLM are 

presented in detail in the Vegetation Treatments 

Programmatic EIS Ecological Risk Assessment

Protocol (ENSR 2004) and in Appendix C; methods 

used by the Forest Service are available at

http://www.fs.fed.us/r6/invasiveplant-eis/. 

Herbicide use poses potential risks to aquatic and 

riparian plant species. However, appropriate 

implementation of SOPs should minimize these risks 

(see Table 2-8). These SOPs include the following: 

• Survey for special status aquatic and riparian

plant species before treating an area. 

• Use drift reduction agents to reduce the risk of 

drift hazard. 

• Use a selective herbicide and a wick or 

backpack sprayer. 

• Use an appropriate herbicide-free buffer zone 

for herbicides not labeled for aquatic use. This 

information is discussed in the ERA guidance

provided in the Vegetation section of this 

chapter. 

Summary of Herbicide Impacts 

Impacts from Herbicides Applied to Wetlands and 

Riparian Areas 

Use of herbicides to control aquatic and riparian

vegetation can improve habitat quality for fish and

wildlife, improve hydrologic function, and reduce soil

erosion. Non-native species, such as purple loosestrife, 

form extensive monotypic stands that displace native 

vegetation used by wetland animal species for food and 

BLM Vegetation Treatments Using Herbicides 4-37 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

cover (Bossard et al. 2000). Purple loosestrife can also

alter the hydrology and soil conditions of wetland

pastures and impact recreational activities. Water-thyme

is an aquatic species that forms large mats that fill the 

water column and can severely restrict water flow,

leading to a decrease in habitat for fish and wildlife and

water quality. Eurasian milfoil is an aquatic species that 

has spread widely over the western U.S. and has been 

found to alter the physical and chemical characteristics 

of lakes and streams. Much of the BLM’s vegetation 

control effort in wetland and riparian areas would focus 

on these species. 

Most aquatic herbicides are non-selective and could

cause adverse impacts to non-target wetland and 

riparian species diversity, competitive interactions, 

species dominance, and vegetation distribution (Kleijn

and Snoeijing 1997). Herbicide applications could 

reduce plant cover, leading to increased sedimentation, 

increased nutrient loading, alterations in native 

vegetation, and changes to temperature and hydrologic 

conditions. 

An increase in soil erosion and surface water runoff 

could result from vegetation reduction, which could

lead to streambank erosion and sedimentation in 

wetlands and riparian areas (Ott 2000). The amount and

likelihood of streambank erosion and sedimentation

would be directly proportional to the size of the 

treatment area (i.e., larger treatment areas would lead to

increased risk of streambank erosion and

sedimentation). Additionally, sedimentation could result

in a reduction in the acres of wetland and riparian

habitat. 

The following six chemicals are approved for use in

aquatic systems by the USEPA, including wetlands and 

riparian areas. Two of these chemicals (diquat and 

fluridone) are newly proposed for use on public lands. 

2,4-D 

2,4-D salt formulations are approved for use in riparian 

and aquatic systems. The principal hazard of 2,4-D 

exposure to non-target plants is from unintended direct 

deposition or spray drift (SERA 1998). 2,4-D salt

formulations can be used in spot treatments and applied 

according to the labeled rate without substantially 

affecting native aquatic vegetation and without 

significantly changing species diversity (USDA Forest

Service 2005, Washington Department of Ecology 

2004). 2,4-D has been shown to be effective for treating

Eurasian watermilfoil. 2,4-D ester formulations are

toxic to fish and aquatic invertebrates and should not be

used near aquatic systems. Kuhlmann et al. (1995) 

found no biodegradation of 2,4-D under anaerobic 

(sulfate reducing) conditions in a laboratory experiment

of sediments and groundwater. In aerobic riparian soils 

that have a high content of organic material, an active 

microbial community, high pH values, and high

temperatures, toxic effects are limited because of rapid

degradation of 2,4-D. 2,4-D may inhibit shoot and/or 

root growth of macrophytes in aquatic systems (Roshon

et al. 1999). 

Diquat 

Diquat, a contact herbicide approved for floating, 

submerged, and aquatic vegetation, would be used in

ponds, lakes, canals, and reservoirs. Diquat persists in

the environment, but is quickly adsorbed to soils and 

sediments, immobilizing it and rendering it unlikely to

contaminate leachate or runoff. Target wetland species 

that could be controlled by diquat include Eurasian 

watermilfoil, water-thyme, water hyacinth, and giant

salvinia. Diquat kills on contact, but it does not kill 

plant roots, and therefore it is often used for singleseason control of submerged aquatic plants and not for 

plant eradication (Washington Department of Ecology 

2004). 

As a non-selective aquatic herbicide, diquat should not 

be applied in wetlands where there is the potential for 

killing or harming aquatic plants of concern. Large

areas should not be treated with diquat in a single

application without some procedure to remove treated

vegetation, as studies have shown that rapid rates of 

plant decomposition following treatment may

deoxygenate water, potentially resulting in negative 

effects to fish and other aquatic organisms. 

Fluridone 

Fluridone is a slow-acting, broad-spectrum aquatic 

herbicide that can be used at low concentrations on both 

submerged and emergent aquatic plants. Fluridone 

photodegrades, volatilizes slowly from water, and 

adsorbs to suspended solids and sediments (National

Library of Medicine 2002). 

Fluridone would be used to treat ponds, lakes, canals,

and reservoirs, but not flowing waters where contact

time cannot be maintained. It is a non-selective

herbicide at higher application rates, but is most

frequently applied at lower application rates, where it 

selectively affects submerged aquatic plants while only 

minimally affecting emergent vegetation. Where the 

entire water body is infested with a non-invasive 

BLM Vegetation Treatments Using Herbicides 4-38 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

species, such as Eurasian watermilfoil, a whole water 

body treatment of fluridone can be used. Fluridone is

not suitable for spot treatments (sites less than 5 acres 

within a larger water body), as it is difficult to maintain

enough contact time between the plant and the fluridone 

to kill the plant (Washington Department of Ecology 

2004). 

Glyphosate 

Glyphosate is approved for fresh and brackish water, 

including estuaries, and wetland and emergent aquatic 

vegetation. Glyphosate may be used in riparian and

aquatic habitats along shorelines for species such as 

purple loosestrife, reed canarygrass, giant reed, and 

cattail, and for floating aquatic species such as waterlily.

Disking, with a follow-up application of glyphosate the 

following year, has been used effectively in Washington

State to control reed canarygrass (Paveglio and Kilbride

2000) Glyphosate is also used to control grasses, 

herbaceous plants, and some broadleaf trees and shrubs 

in riparian areas. Glyphosate dissipates rapidly from 

surface water by adsorption and biodegradation and 

may move into surface water with eroded soil particles. 

Freshwater aquatic macrophytes and algae are reported 

to be sensitive to glyphosate at concentrations as low as

20 mg/l; however, stimulation in growth of some green 

algae has also been reported at low concentrations (0.02 

mg/l; SERA 2003a). 

Imazapyr

Imazapyr is approved for use in wetlands and riparian 

areas, including brackish and coastal waters. It is used

to control emergent and floating plants. Imazapyr has 

been shown to be effective in the management of 

saltcedar, which has invaded many riparian zones 

throughout the western U.S.. Imazapyr is used to treat

emergent wetland plants such as cordgrass, reed

canarygrass, and phragmites, and floating plants such as 

waterlily. Imazapyr use may result in effects to nontarget aquatic vegetation, and high concentrations of

imazapyr in surface water may adversely affect some

aquatic macrophytes (SERA 2004d). 

Residual soil contamination with imazapyr could be 

prolonged in some areas, possibly resulting in

substantial inhibition of plant growth (SERA 2004d). 

Imazapyr is not likely to degrade in anaerobic soils or 

sediments, and has been shown to strongly bind to peat

(American Cyanamid 1986, SERA 2004d). 

TABLE 4-10

Anaerobic Half-life in Soil for Herbicides Analyzed

in this PEIS 

Herbicide Anaerobic Soil Half-life 

(days) 

2,4-D 333

2,4-DP > 200

Asulam > 14

Atrazine 15-77

Bromacil 144 to 198 

Chlorsulfuron 109 to 263 

Clopyralid > 1,000

Dicamba Not determined

Diflufenzopyr 20

Diquat > 1,000

Diuron 5 to 100 

Fluridone 4 to 270 

Fosamine ammonium 4 

Glyphosate 12 to 70 

Hexazinone Stable

Imazapic > 1,000

Imazapyr > 500

Mefluidide No information found 

Metsulfuron methyl 338 

Overdrive® 88 

Picloram > 500

Simazine 71

Sulfometuron methyl 60 

Tebuthiuron Not determined

Triclopyr < 1

Sources: Krueger et al. 1991; USEPA 1992, 1994a, b, 1995c, 

1996, 1999a, 2001b, 2003d ; Krzyszowska et al. 1994; Tomlin 

1994; Kuhlmann et al. 1995; SERA 1997, 2003a, 2003b, 2004c, 

2004d, 2004e; Harrison et al. 1998; Strek 1998a, b; Suzuki et al. 

2001. 

Triclopyr 

Triclopyr controls a variety of weed species and can be 

effective as a spot treatment for Eurasian watermilfoil

because it is relatively selective for this species at low 

application rates. In addition, it is effective in riparian 

areas as a treatment for purple loosestrife, as it does not

damage native grasses and sedges (Washington

Department of Ecology 2004). 

Commercial formulations of triclopyr may contain the 

triethylamine salt (TEA) or the BEE formulations, both 

of which degrade to an acid form. Both formulations are 

used to selectively treat unwanted riparian woody 

vegetation; however, only the TEA formulation is 

approved for selective control of submersed aquatic 

vegetation (SERA 2003c). Triclopyr BEE is projected 

BLM Vegetation Treatments Using Herbicides 4-39 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

to be somewhat more hazardous when used where 

runoff to open water may occur. 

Impacts from Herbicides Applied to Uplands 

Non-target wetland and riparian areas could be exposed

to herbicides through a variety of routes, including

accidental spills or direct spray, local spray drift from 

adjacent target areas, surface water runoff, and soil

erosion (Karthikeyan et al. 2003). Risks to wetland and 

riparian non-target species would depend on a number 

of factors, including the amount, selectivity, and

persistence of the herbicide used; the application 

method used; the timing of the application; and the plant

species present. Risks to wetlands and riparian areas 

from surface runoff would be influenced by

precipitation rates, soil types, and proximity to the 

application area. Some herbicides (e.g., sulfometuron

methyl) that adsorb onto soil particles could be carried

off site, increasing their risk of affecting vegetation in 

wetlands and riparian areas. 

Unintentional applications can have severe negative 

impacts on wetland and riparian systems. In particular, 

accidental spills near wetland and riparian areas could 

be particularly damaging to wetland and riparian

vegetation. Spray drift can also degrade water quality in 

wetland and riparian areas and could damage non-target

vegetation. 

Bromacil 

Bromacil is not selective, and accidental exposure could 

injure riparian shade trees and other desirable non-target 

wetland and riparian vegetation. Bromacil is mobile and

has the ability to persist in wetland environments. 

Chlorsulfuron 

Chlorsulfuron is effective at low concentrations and is 

prone to leaching. Hydrolysis rates are the fastest in

acidic waters and are slower as the pH rises (Sarmah

and Sabadie 2002). When hydrolysis rates drop, 

biodegradation becomes the primary loss mechanism.

Strek (1998a, b) studied the dissipation of chlorsulfuron

in an anaerobic sediment/water system; biodegradation 

progressed much more slowly than in aerobic soil 

systems, with a half-life greater than 365 days. 

Clopyralid 

Clopyralid typically leaches and is generally rapidly 

degraded in soil, except in arid soils with low microbial

populations where it remains stable and could

potentially reach wetlands and riparian areas. Clopyralid

is relatively non-toxic to aquatic plants. Overall, effects 

to non-target wetland and riparian vegetation from 

normal application of clopyralid are likely to be limited

to sensitive plant species in or very near the treatment

area, and could be avoided by maintaining an adequate

buffer between the treatment area and wetland and 

riparian areas (SERA 2004b). Clopyralid is not likely to

affect aquatic plants via off-site drift or surface runoff 

pathways; however, the higher concentrations 

associated with accidental spills could result in

temporary growth inhibition of aquatic plants. 

Dicamba 

Direct spray and accidental spill scenarios of dicamba

pose a moderate to high risk to both terrestrial and

aquatic plants. In water, biodegradation is the major 

mechanism for dicamba degradation. Dicamba is

mobile in soils and is therefore likely to reach surface

water and groundwater. A study on the fate of dicamba 

in a riparian wetland showed that dicamba was 

demethylated to 3,6-dichlorosalicylic acid under both

aerobic and anaerobic conditions. The rates of dicamba

degradation were generally more rapid in the surface

than in the subsurface soil microcosms. The study 

indicated that some riparian wetland soils possess 

limited potential to degrade dicamba (Pavel et al. 1999). 

Diflufenzopyr 

Diflufenzopyr is an active ingredient in the herbicide

formulation Overdrive®, along with dicamba. 

Diflufenzopyr is not approved for the treatment of 

aquatic plants, but poses a low risk to riparian species 

and aquatic plants via off-site drift. 

Diuron

Under accidental direct spray and spill scenarios for 

diuron, there is generally a high risk to aquatic plants.

Off-site drift typically poses low to moderate risk to

aquatic plants, provided the ERA-recommended 900-

foot buffer is used (ENSR 2005f). 

Hexazinone 

Aquatic plants are at moderate to high risk from acute 

and chronic exposure to hexazinone at both the typical 

and maximum application rates. Aquatic algal species 

are also sensitive to hexazinone exposure. Furthermore, 

it is likely that aquatic macrophytes are sensitive, based

on the effects of hexazinone on algae and terrestrial

plants (SERA 1997). 

BLM Vegetation Treatments Using Herbicides 4-40 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

I

s

mazapic

The risk to aquatic plants from accidental spills of 

imazapic is moderate to high at the maximum 

application rate and low to moderate at the typical 

application rate (there is no acute risk to aquatic plants

in standing water at the typical application rate). 

Aquatic plants are generally not at risk from off-site

drift of imazapic, except when applied aerially at the

maximum application rate with a buffer of 100 feet or

less. Imazapic rapidly degrades through

photodegradation in aquatic systems (SERA 2004c). 

Met ulfuron Methyl 

Aquatic macrophytes face low risk from acute exposure 

to metsulfuron methyl at upper exposure limits (SERA 

2004e). Metsulfuron methyl is stable to hydrolysis at

neutral and alkaline pHs. Larsen and Aamand (2001) 

evaluated biodegradation of metsulfuron methyl (25

μg/L) under anaerobic and aerobic conditions in sandy 

sediments; the herbicide did not biodegrade under any 

of these conditions. 

Picloram 

The toxicity of picloram to aquatic plants varies 

substantially among different species. There is low risk 

to sensitive aquatic macrophytes from acute exposure to

picloram at the maximum application rate. Because 

picloram does not bind strongly to soil particles and is 

not rapidly degraded in the environment, it has a high

potential for being transported to wetland and riparian

areas. 

Sulfometuron Methyl 

Aquatic plants are at high risk from accidental direct

spray and spill of sulfometuron methyl, but are unlikely 

to be at risk from off-site drift, provided a minimum

900-foot buffer is maintained, as recommended in the

ERA for this herbicide (ENSR 2005j). Aquatic plants in 

standing water are typically at low to moderate risk for 

adverse effects from surface runoff scenarios. 

Sulfometuron methyl should not be applied during high 

winds, as drift could cause extensive damage to

vegetation at a substantial distance from the application 

site. 

Tebuthiuron 

Aquatic plants are at high risk for adverse effects under 

tebuthiuron spill scenarios, and potentially at high risk

for adverse effects from direct spray scenarios. Aquatic 

plants are not at risk for adverse effects under scenarios 

involving off-site drift of tebuthiuron; however, surface 

runoff typically poses a risk to submerged aquatic plants 

for herbicide treatments at the maximum application 

rate, and at the typical application rate in sandy soils. 

Tebuthiuron is resistant to hydrolysis and photolysis in

aquatic systems; however, some photodegradation has 

been reported at alkaline conditions (pH=9), and 

tebuthiuron is expected to biodegrade slowly in aquatic 

systems. 

Impacts of Other Herbicides Currently Available for 

Use 

Asulam, atrazine, fosamine, mefluidide, simazine and

2,4-DP (also known as dichlorprop) are currently 

approved for use on public lands in many western states 

(see Table 2-2). These herbicides have not been used, or

have only been used infrequently (fosamine), during the 

past 7 years. They are not registered for use in riparian 

or aquatic areas. Atrazine, simazine, and 2,4-DP are 

persistent and considered mobile in well-drained soils, 

and could reach wetlands and riparian areas. Persistence

is extended under dry and/or cold conditions. 

Mefluidide is not strongly adsorbed to soil but has a 

half-life of 1 to 2 weeks. Fosamine is rapidly 

metabolized by soil microbes and does not persist (Han

1979 cited in Tu et al. 2001). 

Impacts by Alternative 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation treatment programs in

14 western states, and would be able to use 20

herbicides that were previously approved under earlier 

RODs. Herbicide use under the No Action Alternative 

would impact target and non-target vegetation over an 

estimated 305,000 acres annually, including

approximately 2,300 acres of riparian and aquatic

habitat. Herbicides used to control aquatic and riparian 

vegetation under this alternative could include 2,4-D, 

glyphosate, and imazapyr, which are registered for

aquatic uses; and dicamba, tebuthiuron, and triclopyr in

riparian areas where contact with water can be avoided. 

The nature of impacts would be similar to those that 

have occurred in the past 10 years. Negative impacts to

wetland and riparian vegetation would be lower than

under the other herbicide treatment alternatives (B, D, 

and E) because far fewer acres would be treated. In

addition, adverse impacts to wetland and riparian 

BLM Vegetation Treatments Using Herbicides 4-41 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

vegetation in areas receiving treatments could be greater

than at present if newer, more effective herbicides could 

not be used. 

Of the 20 herbicides previously approved, it is unlikely

that 2,4-DP, asulam, atrazine, fosamine, mefluidide, or 

simazine would be used. It is likely that 2,4-D and

glyphosate (aquatic uses), and picloram and tebuthiuron

(upland uses), would be used most frequently under this

alternative. Glyphosate and 2,4-D have been 

demonstrated to provide benefits through the control of 

invasive riparian and wetland plant species. 

Diflufenzopyr+dicamba (as Overdrive®), diquat, 

fluridone, and imazapic would not be available for use

under this alternative. Risks to wetland and riparian 

areas from use of these herbicides are similar to or

lower than risks associated with currently-approved

herbicides. Use of other herbicides in place of these four 

herbicides could pose a greater risk to wetland and 

riparian plants under accidental spill and drift scenarios 

than under alternatives B, D, and E. In addition, 

fluridone is specifically indicated for aquatic use, 

whereas none of the other currently-approved herbicides 

are strictly aquatic herbicides. Under the other herbicide 

treatment alternatives, aquatic vegetation would be 

treated with diquat and fluridone, both of which are 

effective in the control of Eurasian watermilfoil, waterthyme, water hyacinth, and giant salvinia. The other 

herbicides registered for aquatic use—glyphosate and

triclopyr—are not as effective in controlling these

species. 

Under the No Action Alternative, the BLM would not 

be able to use new chemicals that may become available

in the future and that may be more effective and safer to

use in wetland and riparian areas than herbicides 

currently available to the BLM. Public lands in Alaska, 

Nebraska, and Texas have not been part of the herbicide 

program historically, and would not be included under 

this alternative. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Under Alternative B, the Preferred Alternative, 

herbicide treatments would occur on approximately

932,000 acres annually across 17 western states, of

which about 10,000 acres would consist of aquatic and

riparian habitat. The BLM would only be allowed to use

14 currently-approved herbicides (six fewer than under 

the No Action Alternative), but would be able to use the

four new herbicides evaluated in this PEIS. In addition, 

the BLM would be able to treat vegetation using

herbicides in Alaska, Nebraska, and Texas. Although it

is anticipated that few or no herbicide treatments would 

occur in Alaska, the BLM would retain the option to use 

herbicides in Alaska should the need arise and the 

benefits of using herbicides outweigh the risks of other 

treatment methods. 

This alternative could result in the most extensive 

impacts to wetlands and riparian areas (both negative 

and positive) because it proposes the greatest total

treatment acreage (more than four times the acreage 

proposed under the No Action Alternative). 

The BLM’s ability to use four new chemicals (fluridone 

and diquat for aquatic applications, and imazapic and 

Overdrive® for terrestrial applications), would provide 

new capabilities for controlling problematic invasive 

species and would potentially result in benefits to

wetland and riparian areas if invasive species were 

controlled or eliminated. Fluridone, in particular, has 

been effective at controlling Eurasian watermilfoil

(Washington Department of Ecology 2002). Based on 

recent use patterns, 2,4-D, glyphosate, picloram, and 

tebuthiuron would continue to comprise the majority of 

herbicide use under this alternative. The benefits and 

risks of these herbicides are discussed under the No

Action Alternative. 

Overdrive® and imazapic would primarily be used on 

rangelands, but their use could still provide greater 

benefits to riparian and wetland areas, relative to the No 

Action Alternative. Overdrive

® would be used to treat

thistles and knapweeds, while imazapic could be used to 

control downy brome. These invasive plant species 

degrade riparian habitats and can lead to shortened fire 

cycles, followed by soil erosion and sedimentation. 

The ability to use herbicides as they become registered

with the USEPA would allow BLM managers more 

options in choosing herbicides to match treatment goals 

and application conditions, and options to use 

herbicides that pose less risk to wetlands and riparian 

areas than currently-used or proposed herbicides. 

The BLM does not propose to use herbicides in Alaska 

(where the majority of the wetland and riparian areas on

BLM lands are found). However, the BLM would retain 

the option to use herbicides in Alaska should the need 

arise and the benefits of using herbicides outweigh the 

risks of other treatment methods. 

BLM Vegetation Treatments Using Herbicides 4-42 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

Alternative C – No Use of Herbicides 

Herbicides would not be used to manage vegetation 

under Alternative C. Primary effects to riparian and

wetland vegetation would stem from other vegetation 

treatment methods including fire, manual, mechanical, 

and biological control (see PER; USDI BLM 2007a). 

The possible ecosystem benefits of not using herbicides 

would be the elimination of risks to non-target biota 

associated with accidental spills, drift, and persistence

of herbicides. 

Without herbicide treatments, it is likely than some

invasive plants would continue to spread rapidly,

resulting in dramatic and potentially irreversible effects 

on wetland and riparian areas. As discussed previously, 

invasive species outcompete native vegetation and lead 

to widespread incidence of fire and other conditions that 

can result in loss of ecosystem function in wetlands and 

riparian areas. 

Positive ecosystem benefits as a result of vegetation 

management could be reduced under this alternative, as 

there are certain invasive species for which herbicide 

use is the only effective method of treatment or the only

practical method, based on cost, time, accessibility, or 

public concerns. For example, rough terrain that cannot 

be accessed for ground-based treatments could 

potentially be treated using herbicides applied by 

aircraft. Other treatment methods, such as mechanical, 

fire, and biological, can result in soil disturbance and

sedimentation of aquatic bodies, and may not 

adequately treat the pest plant. 

In addition, it is often difficult to eradicate some species 

(such as aquatic species and those that resprout from 

rhizomes) by means other than herbicide application.

These species include Eurasian watermilfoil and waterthyme, which form dense mats of aquatic vegetation

that crowd out native plants and degrade fish habitat 

(Bossard et al. 2000). Chemical treatments (including

the use of 2,4-D, diquat, and fluridone) are more 

effective at controlling these species than other 

treatments, such as mechanical harvesters that tend to 

fragment and spread the weed. 

Alternative D – No Aerial Applications 

Alternative D is similar to the Preferred Alternative in 

that it would allow for use of the same herbicides in the

same areas, and would have similar benefits associated

with increased availability of new and future herbicides. 

However, this alternative would not allow the use of 

aerial application methods, thereby reducing the total

treatment acreage to 530,000 acres. However, there

would be little difference between the alternatives as far 

as treatments in wetlands and riparian areas and 

associated impacts. Nearly all (98%) of the acreage

proposed for treatment in wetland and riparian habitats 

under the Preferred Alternative would be treated using

ground-based methods, and therefore could also be 

treated under Alternative D. However, the potential for 

impacts to wetlands and riparian areas from off-site drift

from upland treatment areas would be substantially less 

under Alternative D than under the Preferred

Alternative. Drift is a major route of unintended damage

to non-target vegetation, with aerial application being 

the primary cause of off-site drift. 

Under this alternative, invasive plant populations in 

remote wetland and riparian areas would likely continue 

to spread. Ground-based herbicide treatments could be 

used in some locations, but likely would not be used in

areas that are too remote, have difficult terrain, or cover 

large expanses. Areas with coverage of invasive species 

may not be comprehensively treated using ground-based 

methods, and subsequent reinvasion could require 

frequent re-treatment in the same area. Non-herbicide

vegetation control may be substituted in areas 

unsuitable for ground-based herbicide treatment. For 

example, prescribed fire can be used to control some

unwanted vegetation types. However, many invasive 

riparian and wetland plant species are able to resprout

after fire. Biological treatments have been shown to be 

effective in some riparian and wetland areas for some

species; however, the number of invasive species with 

known biological control agents and the effectiveness of 

these agents are limited. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides

Approximately 466,000 acres would be treated under 

Alternative E, which is slightly less than the acreage

that would be treated under Alternative D, and less than

half of the acreage that would be treated under the 

Preferred Alternative. Under this alternative, ALSinhibiting herbicides would not be allowed, including

imazapic, imazapyr, chlorsulfuron, metsulfuron methyl,

and sulfometuron methyl. Of these, only imazapyr is 

registered for use in wetland and riparian areas. ALSinhibiting herbicides are potent and have the benefit of 

very low application rates; however, their potency leads 

to residual herbicidal activity. This group of herbicides 

has been shown to damage off-site native and crop

species, and several weed species can develop 

resistance to these herbicides, making them less 

effective. 

BLM Vegetation Treatments Using Herbicides 4-43 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Under this alternative, herbicide treatments would be 

discouraged, broadcast spraying would be prohibited, 

and passive treatment methods would be promoted in

wetland and riparian areas. Imazapyr has been shown to 

be effective against saltcedar, a particularly pernicious

riparian area invader that has few effective treatments.

The inability to use imazapyr to control species such as

saltcedar could potentially correspond to greater adverse 

effects to wetland and riparian areas form these invasive 

species than under the other alternatives, in which 

imazapyr use is allowed. 

Alternative E proposes management that may benefit

wetland and riparian areas, such as limiting the effects 

of minerals extraction, forestry practices, livestock

grazing and OHV use. However, these restrictions 

would be applied only to the extent that they are 

consistent with adopted BLM LUPs. 

Mitigation for Herbicide Treatment 

Impacts 

See mitigation measures for Water Resources and

Quality and Vegetation sections. 

Vegetation 

Introduction 

The present-day composition and distribution of plant

communities in the western U.S. are influenced by

many factors, including physical factors (e.g., climate, 

drought, wind, geology, topography, elevation, latitude, 

slope, exposure) and natural disturbance and humanmanagement patterns (e.g., insects, disease, fire, 

cultivation, domestic livestock grazing, wildlife

browsing; Gruell 1983). In addition, exotic plant species 

have caused a decline in extent of some native plant 

communities in each of the western states. The rapid

expansion of invasive plant species across public lands

continues to be a primary cause of ecosystem

degradation, and control of these species is one of the 

greatest challenges in ecosystem management. The

recent increase in wildfires has been influenced by 

changes in vegetation on public lands over the past 100

years, which have resulted in increases in hazardous 

flammable fuels. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

The largest number of comments submitted was related 

to vegetation. Numerous scoping comments were 

centered around a desire for the BLM to focus on longterm ecosystem sustainability and biological diversity. 

Numerous comments suggested that the PEIS address 

all invasive plants, not just weeds. One respondent 

proposed focusing on minimizing the spread of existing 

weed infestations, while others wanted to ensure that 

weed control measures do not result in more ecological 

disturbances than the weeds themselves. A large

number of comments recommended evaluating the

impact of herbicides on other plant and animal species 

within the areas considered for treatment. Several

comments called for the PEIS to address the impacts of 

new-generation, high-potency pesticides on non-target

plants. There was some concern about weeds becoming

herbicide resistant, and about how the BLM would

prevent the death of beneficial native plants from 

herbicides. To improve sage-grouse habitat, one

respondent recommended that instead of burning

sagebrush, the BLM should treat strips of vegetation 

with herbicides, allow cattle to break the vegetation 

down, and then plant the area with grass. 

Standard Operating Procedures 

There are risks to non-target plants associated with 

herbicide use. However, these risks can be minimized

by following certain SOPs, which can be implemented 

at the local level according to specific conditions. The

following general procedures are designed by the BLM

to reduce potential unintended impacts to vegetation

from herbicide treatments: 

• Conduct pre-treatment surveys for sensitive 

habitat and special status species within or

adjacent to proposed treatment areas. 

• Consider site characteristics, environmental 

conditions, and application equipment in order 

to minimize damage to non-target vegetation. 

• Use drift reduction agents, as appropriate, to 

reduce the drift hazard to non-target species. 

• Turn off aerially applied treatments at the

completion of spray runs and during turns to 

start another spray run. 

• Refer to the herbicide label when planning 

revegetation to ensure that subsequent

BLM Vegetation Treatments Using Herbicides 4-44 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

vegetation will not be injured following 

application of the herbicide. 

• Clean OHVs to remove seeds. 

• Use native or sterile species for revegetation 

and restoration projects. 

• Use weed-free feed for horses and pack 

animals. 

• Use weed-free straw and mulch for

revegetation and other activities. 

These procedures would help minimize impacts to

plants and ecosystems on public lands to the extent 

practical. As a result, long-term benefits to native plant

communities from the control of invasive species would

likely outweigh any short-term negative impacts to

native plants associated with herbicide use. 

Impacts Assessment Methodology 

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM and Forest Service, and 

from earlier BLM vegetation treatment EISs, to assess 

the impacts to target and non-target vegetation from the 

use of herbicides (ENSR 2005b-k; SERA 2005a). The 

methods presented here are a brief overview of the ERA 

process to determine the risks to non-target species 

associated with herbicide use. The ERA methods are 

presented in detail in Appendix C. In addition, the BLM 

reviewed information provided by local field offices in 

2002 for development of this PEIS. This information

included the location, treatment method, application

method, vegetation class, and size of the treatment (in

acres) for treatments proposed during the next 10 to 15

years. 

BLM Methodology 

Problem Formulation 

Both terrestrial and aquatic non-target plants, including 

surrogates for special status species, were evaluated to 

determine assessment endpoints and associated

measures of effect. The essential biological

requirements (i.e., survival, growth, and reproduction) 

of each of these groups of organisms are the attributes to 

be protected from herbicide exposure. Assessment

endpoints, for the most part, reflect direct effects of an 

herbicide on these organisms, but indirect effects were 

also considered. 

Measures of effect are measurable changes in an 

attribute of an assessment endpoint (or its surrogate, as 

discussed below) in response to a stressor to which it is 

exposed (USEPA 1998a). For the screening-level ERA, 

the measures of effect associated with the assessment

endpoints generally consisted of acute and chronic 

toxicity data (from pesticide registration documents and

from the available scientific literature) for the most

appropriate surrogate species. Assessment endpoints for 

non-target vegetation include acute mortality and

adverse direct effects on growth, reproduction, or other

ecologically important sublethal processes. 

Exposure Characterization

In order to assess the potential ecological impacts of 

these herbicide uses, the following exposure scenarios 

were considered that address herbicide exposure and 

acute and chronic (short- and long-term) impacts that

may occur under a variety of conditions: 

• Direct spray of the receptor or water body;

• Off-site drift of spray to terrestrial areas and 

water bodies; 

• Surface runoff from the application area to offsite soils or water bodies; 

• Wind erosion resulting in deposition of 

contaminated dust; and 

• Accidental spills to water bodies. 

The AgDRIFT®

 computer model was used to estimate 

off-site herbicide transport due to spray drift. The

GLEAMS computer model was used to estimate off-site

transport of herbicide in surface runoff and root zone 

groundwater transport. The CALPUFF computer model

was used to predict the transport and deposition of 

herbicides sorbed (i.e., reversibly or temporarily 

attached) to wind-blown dust. Each model simulation

was conservatively approached with the intent of 

predicting the maximum potential herbicide 

concentration that could result from the given exposure 

scenario. 

Effects Characterization

In the majority of cases, toxicological data do not exist 

for the specific plant receptors of concern.

Consequently, toxicological data for surrogate species, 

obtained from a literature review, were evaluated and 

used to establish quantitative benchmarks (i.e., toxicity 

reference values [TRVs]) for the ecological receptors of

concern. Data from scientific studies were used to 

compile statistical endpoints into a matrix for each

chemical and receptor. Data were further subdivided 

BLM Vegetation Treatments Using Herbicides 4-45 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

into acute adverse effect levels, chronic adverse effect

levels, and no observed adverse effect levels 

(NOAELs). For each chemical, receptor, and route of

exposure, the lowest reported acute statistical endpoint 

was selected as the acute TRV. Chronic TRVs, based on

longer exposure periods and associated endpoints such 

as growth and reproduction, were developed, when 

possible, to provide supplementary data to the risk

assessment. Before the chronic NOAEL TRV was 

determined, a chronic lowest observed adverse effect 

level (LOAEL) was identified, which was the lowest

herbicide level that was found to cause significant

adverse effects in a chronic study. Once a LOAEL was 

selected, the chronic NOAEL TRV was established as 

the highest NOAEL value that was less than both the 

LOAEL and the acute TRV. Once developed, TRVs 

were compared with predicted environmental 

concentrations of the herbicide to determine the

likelihood of adverse effects to ecological receptors. 

Risk Characterization

In order to address potential risks to plant receptors, risk

quotients (RQs) were calculated by dividing the

estimated exposure concentration (EEC) for each of the 

previously described scenarios by the appropriate

herbicide-specific TRV. To facilitate the translation of 

RQs into readily applicable estimates of risk, the

calculated RQs were compared to Levels of Concern

(LOCs) used by the USEPA in screening the potential 

risk of herbicides. Distinct USEPA LOCs are currently

defined for the following risk presumption categories: 

• Acute high risk – The potential for acute risk is 

high; 

• Acute restricted use – The potential for acute

risk is high, but may be mitigated; 

• Acute endangered species – Special status 

species may be adversely affected; and 

• Chronic risk – The potential for chronic risk is 

high. 

The ecological risk implications of various exposure 

estimates can be readily determined by noting which 

RQs exceed the corresponding LOCs. 

The risks of tank mixes on plant receptors were

determined using the assumption that the products in 

tank mixes act in an additive manner. The predicted 

RQs for two active ingredients were summed for each

individual exposure scenario to see if additional RQs 

exceeded the corresponding LOCs. However, there is

some uncertainty in this evaluation because herbicides 

in tank mixes may not interact in an additive manner;

this may overestimate risk if the interaction is 

antagonistic, or it may underestimate risk if the 

interaction is synergistic. In addition, other products 

may also be included in tank mixes and may contribute 

to the potential risk. 

Uncertainty Analysis

For any ERA, a thorough description of uncertainties is 

a key component of risk determination that serves to

identify possible weaknesses in the analysis and to 

elucidate what impact such weaknesses might have on 

the final risk conclusions. In this analysis, listed

uncertainties were followed by a logical discussion of 

what bias, if any, the uncertainty may introduce into the

risk conclusions. This bias was represented in 

qualitative terms that best describe whether the 

uncertainty might: 1) underestimate risk, 2) 

overestimate risk, 3) be neutral with regard to the risk 

estimates, or 4) be unable to be determined without 

additional study. 

Forest Service Methodology 

The Forest Service risk assessment methodology was 

similar to that used by the BLM (see SERA 2001a for a 

complete description of the methodology). The steps 

involved in the Forest Service risk assessments include 

hazard identification, exposure assessment, dose

response assessment, and risk characterization. 

Hazard identification involved the review of existing

data with a focus on the dose-response and doseseverity relationships to determine the effect levels (e.g., 

NOAEL, LOAEL) and assessment endpoints (e.g., 

acute toxicity, subchronic or chronic systemic toxic 

effects, reproductive and teratogenic effects) that are 

most relevant for the herbicide risk assessments. 

In the exposure assessment phase, the Forest Service 

developed four general and accidental/incidental

exposure scenarios (i.e., direct spray, spray drift, runoff, 

and wind erosion) for groups of non-target vegetation

according to the application method and the chemical

and toxicological properties of the given herbicide. The 

Forest Service scenario of contaminated irrigation 

water—a direct application scenario—was not

evaluated by the BLM because their vegetation 

treatment program does not typically involve irrigation 

of vegetation. 

BLM Vegetation Treatments Using Herbicides 4-46 June 2007 

Final Programmatic EIS 
 ENVIRONMENTAL CONSEQUENCES

Dose response assessment described the degree or

severity of risk as a function of dose. A dose was 

derived—usually from a series of experimental doses—

that was associated with a negligible, or at least a

defined, level of risk. These dose levels are generally 

referred to as reference values, or more specifically as

“reference doses” (RfDs). To derive the reference value, 

the experimental threshold was divided by uncertainty 

factors used to account for discrepancies between

experimental exposure conditions and the conditions of

the receptor might experience during Forest Service 

exposure. Often, reference values are standard across 

government agencies. 

The risk characterization process then compared the 

exposure assessment to the dose response assessment to 

determine an LOC for a specific exposure scenario. 

Hazard Quotients (HQs) were developed through this 

process. Hazard Quotients are analogous to the RQs 

developed in the BLM risk assessments—they are 

calculated as the projected level of exposure (i.e., EEC) 

divided by an index of an acceptable level of exposure

or otherwise defined level of exposure (e.g., a NOAEL 

divided by an uncertainty factor). In addition, the

herbicides were all compared based on their selectivity, 

potency, persistence in the environment, and ability to 

move off site. 

As with the BLM risk assessments, information on 

effects to native species was incomplete (the USEPA 

conducts studies predominantly on agricultural crops, 

rather than native species), so impacts were extrapolated 

from the risk assessment or herbicide labels. Using

herbicide labels to identify close relatives of native or

desirable species does help to reduce uncertainty. 

However, Boutin et al. (2004) concluded that it was 

likely that the suite of species currently used in most

risk assessments were not representative of the habitats 

found adjacent to agricultural treatment areas, and

might cause an unacceptable bias and underestimated 

risk. 

Impacts Common to All Treatments 

The effectiveness of herbicide treatments in managing

target plants and the extent of disturbance to native

plant communities varies by the extent and method of 

treatment (e.g., aerial vs. ground) and chemical used

(e.g., selective vs. non-selective), as well as by local

plant types and physical features (e.g., soil type, slope) 

and weather conditions (e.g., wind speed) at the time of 

application. Treatments would likely affect plant species 

composition of an area and might affect plant species 

diversity. Species composition and species diversity are

equally important contributors to ecosystem function 

(USDA Forest Service 2005). Because certain

herbicides may target certain types of plants (e.g., 

broadleaf species), an herbicide treatment program for a

given ecosystem and area should include multiple types 

of herbicides. For example, if picloram or clopyralid are 

the only herbicides used in a highly invaded area, 

weedy annual grasses, such as medusahead, downy 

brome, and barbed goatgrass may begin to dominate. 

The following sections detail the possible effects of 

herbicide treatments on both target and non-target

plants. 

Non-target Plants 

Herbicides could come into contact with and impact 

non-target plants through drift, runoff, wind transport, 

or accidental spills and direct spraying. Potential

impacts include mortality, reduced productivity, and

abnormal growth. Risk to off-site plants from spray drift

is greater under scenarios with smaller buffer zones and

application from greater heights (i.e., aerial application 

or ground application with a high boom). Risk to offsite plants from surface runoff is influenced by 

precipitation rate, soil type, and application area. Plant

receptors would be at risk under most accidental 

exposure scenarios (i.e., direct spray or spill). Persistent

herbicides (e.g., bromacil) adsorbed to soil particles

could also be carried off-site by wind or water, affecting

plants in other areas. Risk assessments predicted no risk

to plant receptors from wind transport of herbicide 

particles under all of the evaluated scenarios. (However,

an incident of extensive damage to crop species has 

been reported as a result of drift of sulfometuron methyl

over a large area [see ENSR 2005j]). Application rate is 

a major factor in determining risk, with higher 

application associated with greater risk to plants under 

various exposure scenarios. 

Target Plants 

Herbicides offer an effective and often resourceefficient means of treating and managing unwanted 

vegetation. Mechanical and manual methods are often 

more time and labor intensive than herbicide 

application, and cause soil disturbance, which can 

provide the appropriate conditions for invasive weeds to

resprout from roots and rhizomes or grow from dormant

seeds. In addition, herbicide use may be seen as less 

dangerous than treatment with prescribed fire in dry 

areas that have high fire risk. The use of herbicides 

would benefit plant communities with weed infestations

by decreasing the growth, seed production, and

BLM Vegetation Treatments Using Herbicides 4-47 June 2007 

Final Programmatic EIS
ENVI

BLM 

Final Pr

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-48 June 2007 

ogrammatic EIS 

competitiveness of target plants, thereby releasing 

native species from competitive pressures (e.g., water, 

nutrient, and space availability) and aiding in the 

reestablishment of native species. The degree of benefit 

to native communities would depend on the toxicity of 

the herbicide to the target species and its effects on nontarget species, as well as the success of the treatments 

over both the short and long term. 

Use of preemergence and postemergence soil residual 

herbicides is common in ROWs, near oil and gas and 

other facilities, and along roads where vegetation must 

be eliminated for safety, to reduce fire hazards, and for 

aesthetic purposes. Other treatment methods, such as 

manual methods and use of fire, are often not as 

effective at eliminating vegetation and may not be as 

safe to use as herbicides. 

Some treatments are very successful at removing weeds 

over the short term, but are not successful at promoting 

the establishment of native species in their place. In 

such cases, seeding of native plant species would be 

beneficial. Weeds may resprout or reseed quickly, 

outcompeting native species, and in some cases 

increasing in vigor as a result of treatments. The success 

of treatments would depend on numerous factors, and 

could require the use of a combination of methods to 

combat undesirable species. In addition, repeated use of 

a particular herbicide on a particular site could cause 

target weeds to develop a certain level of resistance to 

that herbicide over time, reducing the effectiveness of 

long-term treatments. 

Invasive plant treatment effectiveness monitoring would 

be conducted at treated sites and would range from site 

re-visits to compare the targeted population size against 

pre-treatment inventory data, to comparing pretreatment and post-treatment photo points, to more 

elaborate transect work depending on the species and 

site specific variables. The goals of such monitoring 

would be to: 1) identify what changes in distribution, 

amount, and proportion of invasive plant infestations 

have resulted due to treatments; 2) determine if 

infestation size been reduced at the project level or at a 

larger scale such as a watershed; and 3) determine 

which treatment methods, separate or in combination, 

are most successful for a given species (USDA Forest 

Service 2005). 

In addition to herbicide treatments, the BLM would use 

other forms of vegetation treatment on public lands. A 

PER has been developed to accompany this PEIS that 

discusses these treatment methods, along with their 

likely impacts to natural resources over the next 10 

years. In many cases, the treatments would return all or 

a portion of the treated area to an early successional 

stage, killing off disturbance-intolerant species (e.g., 

sagebrush) and freeing up resources such as light and 

nutrients for early successional species (e.g., annual 

grasses and forbs). In areas where fire suppression has 

historically occurred, vegetation treatments would be 

expected to benefit native plant communities by 

mimicking a natural disturbance component that has 

been missing from these communities, altering them 

over time. In areas that have been highly degraded, 

merely restoring disturbance to the ecosystem may in 

some cases adversely affect native plant communities 

by encouraging the spread of weeds or the persistence 

of an altered vegetation structure and species 

composition. These effects would vary depending on 

the treatment used, the type of vegetation on the 

treatment site, the amount of degradation on the site, 

and numerous other factors. 

Impacts of BLM-Evaluated Herbicides 

Bromacil 

Bromacil is a non-selective, “broad-spectrum,” systemic 

herbicide, which is most effective against annual and 

perennial weeds, brush, woody plants, and vines. 

Bromacil kills target plants by blocking electron 

transport and the transfer of light energy, thereby 

disrupting photosynthesis. Because of its non-selective 

nature, bromacil may be highly effective in areas where 

a variety of invasive species dominate and where very 

few non-target plants exist. Bromacil is best used in 

areas where bare ground is desired (e.g., around fences 

and structures); it has high residual activity, so it would 

be effective for an extended period of time. 

Because of its non-selective qualities, bromacil poses a 

high risk to non-target species in the immediate vicinity 

of the treatment area. The risk assessment for bromacil 

shows that it poses a high risk to non-target terrestrial 

and aquatic plants in accidental direct spray and spill 

scenarios (Table 4-11). Off-site drift of bromacil 

generally poses a moderate risk to non-target terrestrial 

plants, with somewhat lower risk as buffer zones get 

larger and application heights get smaller, and with high 

risk to special status terrestrial plants under scenarios 

involving the maximum application rate at lower buffer 

distances and higher application heights. Most off-site 

drift scenarios pose low or no risk to aquatic plants. At 

buffer distances of 900 feet, aquatic plants are not at risk 

from off-site drift of bromacil. Bromacil does not pose a 

risk to typical non-target terrestrial plants under surface 

runoff scenarios, but does pose a low risk to special 
TABLE 4-11

Risk Categories Used to Describe Typical Herbicide Effects to Vegetation According to Exposure Scenario and Ecologi

BROM1 CHLOR1 DICAMBA DIFLU1 DIQUAT DIURON FLUR1 IMAZ1 OVER1 

Application Scenario 

Typ2 Max2 Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max 

Direct Spray

H3 H H H H H M H H H M H L M M H 

Terrestrial plants [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] NE NE [1:1] [1:1] [1:1] [1:1Special status H H H H H H H H H H H H L M H H terrestrial plants [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] [1:1] NE NE [1:1] [1:1] [1:1] [1:1

H H M M L L L L H H H H 0 0 L L M M 

Aquatic plants pond [1:2] [2:2] [1:2] [2:2] [1:2] [1:2] [1:2] [2:2] [2:2] [2:2] [2:2] [2:2] [2:2] [2:2] [1:2] [2:2] [1:2] [1:2

H H M M L L L L H H H H 0 0 L M M H 

Aquatic plants stream [2:2] [2:2] [2:2] [2:2] [1:2] [1:2] [1:2] [1:2] [2:2] [2:2] [2:2] [2:2] [2:2] [2:2] [2:2] [2:2] [1:2] [1:2Accidental Spill to a Pond 

H H M L H H L H M 

Aquatic plants pond NE [1:1] NE [1:2] NE [1:1] NE [1:1] NE [2:2] NE [1:1] NE [2:2] NE [2:2] NE [1:1Off-Site Drift 

M M M M M M 0 0 L M 0 L 0 0 0 0 

Terrestrial plants [3:6] [3:6] [5:12] [8:12] [4:6] [3:6] [4:6] [4:6] [7:12] [7:12] [5:6] [4:6] NE NE [18:18] [13:18] [5:6] [4:6Special status M H M M H H L L M M M H 0 0 L L terrestrial plants [3:6] [3:6] [7:12] [7:12] [2:6] [3:6] [3:6] [4:6] [7:12] [7:12] [3:6] [3:6] NE NE [17:18] [13:18] [3:6] [4:6

0 L 0 0 0 0 0 0 L M 0 0 0 0 

Aquatic plants pond [9:12] [7:12] [24:24] [24:24] [9:12] [8:12] [12:12] [12:12] NE NE [8:12] [6:12] NE NE [36:36] [34:36] [12:12] [12:1

0 L 0 0 0 L 0 L L M 0 0 0 0 

Aquatic plants stream [8:12] [6:12] [24:24] [22:24] [8:12] [6:12] [8:12] [6:12] NE NE [6:12] [6:12] NE NE [36:36] [33:36] [8:12] [6:12Surface Runoff

0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Terrestrial plants [42:42] [42:42] [42:42] [42:42] [42:42] [42:42] [42:42] [42:42] NE NE [42:42] [42:42] NE NE [42:42] [42:42] [42:42] [42:4Special status 0 0 0 0 0 0 0 0 0 0 0 0 0 0 terrestrial plants [39:42] [38:42] [42:42] [42:42] [42:42] [42:42] [34:42] [33:42] NE NE [38:42] [34:42] NE NE [42:42] [42:42] [34:42] [33:4

M H 0 0 0 0 0 0 M H 0 0 0 0 

Aquatic plants pond [70:84] [45:84] [64:84] [53:84] [78:84] [45:84] [84:84] [84:84] NE NE [50:84] [64:84] NE NE [80:84] [62:84] [70:84] [67:8

0 L 0 0 0 0 0 0 L L 0 0 0 0 

Aquatic plants stream [45:84] [55:84] [80:84] [77:84] [84:84] [83:84] [84:84] [84:84] NE NE [35:84] [39:84] NE NE [84:84] [83:84] [84:84] [84:8

BLMVegetationTreatments Using Herbicides 4-49 June 2007 

FinalProgrammaticEIS
June 2007 

FinalProgrammaticEISogrammaticEIS

TABLE 4-11 (Cont.) 

Risk Categori Categories Used to Describe Ty scribe Typical Herbici pical Herbicide Effects to Vegetation Accor Vegetation According to Ex ing to Exposure Scenario a Scenario and Ecologi

nd Ecologi

BROM1 CHLOR1 DICAMBA DIFLU1 DIQUAT DIURON FLUR1 IMAZ1 OVERBROM1 CHLOR1 DIFLU1 FLUR1 IMAZ1 OVER

Application Scenario 

Typ2 Max2 Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ M

Wind Erosion 

0 0 0 0 0 0 0 0 0 0 0 0 0 

Terrestrial plants [9:9] [9:9] [9:9] [9:9] [9:9] [9:9] [9:9] [9:9] NE NE [9:9] [9:9] NE NE [9:9] [9:9] [9:9] [9Special status 0 0 0 0 0 0 0 0 0 0 0 0 0 terrestrial plants [9:9] [9:9] [9:9] [9:9] [9:9] [9:9] [9:9] [9:9] NE NE [9:9] [9:9] NE NE [9:9] [9:9] [9:9] [9Aquatic plants pond NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NAquatic plants stream NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE NE N

1 BROM = Bromacil; CHLOR = Chlorsulfuron; DIFLU = Diflufenzopyr; FLUR = Fluridone; IMAZ = Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; and 2 Typ = Typical application rate; and Max = Maximum application rate.3 Risk categories: = 0 = No risk (majority of RQs < most conservative LOC for non special status species); L = Low risk (majority of RQs 1-10x most conservative LOC fo

Moderate risk (majority of RQs 10-100x most conservative LOC for non special status species); H = High risk (majority of RQs >100 most conservative LOC for non speevaluated. The Risk Category is based on the risk level of the majority of risk quotients observed in any of the scenarios for a given exposure group and receptor type. T

tables in Chapter 4 of the ERAs (ENSR 2005b-k) to determine the specific scenarios that result in the displayed level of risk for a given receptor group. The number in brack

in the indicated risk category: number of scenarios evaluated.

BLMVegetationTreatments Using Herbicides 4-50
ENVIRONMENTAL CONSEQUENCES

status terrestrial plants when applied in watersheds with

clay soils and precipitation levels greater than 100

inches per year (in/yr). Aquatic plants are at risk from 

surface runoff of bromacil; under most surface runoff 

scenarios there would be a moderate risk to aquatic

plants in ponds associated with applications at the

typical application rate, and moderate to high risk 

associated with applications at the maximum 

application rate (higher risk with increased precipitation 

and sand or clay soils). Aquatic plants in streams are at

no to low risk under most surface runoff scenarios, with

moderate risk when bromacil is applied at the maximum 

application rate and in sand soils or in loam soils with

greater application areas (100 and 1,000 acres) and

increased precipitation (200 to 250 in/yr). For

applications of bromacil at the typical application rate, 

chronic risk to aquatic plants in the stream from surface

runoff of bromacil would be much less than acute risk 

(chronic risk would be low in larger application areas 

and in watersheds with sand soils and more than 100 

in/yr precipitation). Because bromacil is a non-selective 

herbicide and poses a significant risk to non-target 

plants, it would be most appropriately used in areas 

exclusively composed of invasive species at substantial

distances (greater than 900 feet) from non-target 

populations (Table 4-12). 

Chlorsulfuron 

Chlorsulfuron is a selective herbicide used on perennial

broadleaf weeds and grasses. Chlorsulfuron inhibits the

synthesis of ALS, which is the catalyst for the

production of amino acids that are required for protein

synthesis and cell growth. Chlorsulfuron is effective 

both pre- and post-emergence, inhibiting seed

germination and killing established plants. 

Chlorsulfuron is highly active, with only small

concentrations required to kill target plants. Due to its 

activity, chlorsulfuron is highly effective in managing

aggressive invasive species such as hoary cress, 

perennial pepperweed, and selected biennial thistles 

(bull, musk, and Scotch), and yellow starthistle. 

Accidental direct spray or spill of chlorsulfuron poses a 

moderate to high risk to terrestrial plants and aquatic

plants in streams (Table 4-11). Accidents mostly pose a 

moderate risk to aquatic plants in ponds (but high 

chronic risk at the maximum application rate). Off-site

drift of chlorsulfuron presents low to moderate risk to

typical non-target terrestrial plant species and higher 

risk to special status terrestrial plant species. Risk

associated with off-site drift would be high for aerial 

applications and ground applications with high booms

and small buffer distances. In more than half of the 

modeled scenarios, no risk to aquatic plants from offsite drift of chlorsulfuron was predicted. Risk to aquatic 

plants was never predicted when chlorsulfuron was 

applied either aerially or on the ground with 900-foot

buffers (Table 4-12). However, there would be a low 

risk to aquatic plants with smaller buffer distances. 

Terrestrial plants are not at risk from surface runoff of

chlorsulfuron; however, aquatic plants are at low risk at

higher precipitation levels and in watersheds with loam 

soils, particularly at the maximum application rate 

(aquatic plants in streams are not at chronic risk under 

any scenario). Because of its activity, chlorsulfuron

should be applied at the lowest possible dose and with

buffer distances of at least 900 feet from non-target

plant populations, particularly if the non-target plants

are perennial and broadleaved or grasses. This herbicide 

may be best used at low rates and spot applications on 

highly aggressive species and in areas where target 

plants are the dominant species. 

Dicamba 

Overdrive® is a formulation of dicamba and

diflufenzopyr. An analysis of risks to vegetation for 

dicamba was conducted during preparation of the

Overdrive® ERA. 

Risk assessments predicted high risk to non-target 

terrestrial plants and low to moderate risk to aquatic

plants under accidental direct spray and spill scenarios 

(Table 4-11). Off-site drift of dicamba poses moderate 

to high risk to terrestrial plants with buffers of less than 

1,000 feet for typical species, and buffers of less than

1,050 feet for special status species. 

Aquatic plants in streams are at low risk under scenarios 

involving off-site drift of dicamba when it is applied at

the maximum rate. Surface runoff does not pose a risk 

to special status terrestrial plants. Dicamba could be

effective in suppression or control of weeds when 

applied at least 1,000 feet from non-target plant

populations of interest or 1,050 feet from special status 

plant species (Table 4-12). 

Diflufenzopyr 

Diflufenzopyr, an active ingredient in the herbicide

formulation Overdrive® (along with dicamba), is a 

selective, systematic herbicide active ingredient used for 

the management of annual broadleaf weeds postemergence, and the management and/or suppression of 

many perennial broadleaf weeds and annual grasses. 

Accidental direct spray and spill scenarios pose a 

moderate to high risk to non-target terrestrial plants and

BLM Vegetation Treatments Using Herbicides 4-51 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

a low chronic risk to aquatic plants (Table 4-11). Offsite drift of diflufenzopyr poses low risk to terrestrial

plants with buffers of less than 100 feet for typical

species and less than 900 feet for special status species. 

Aquatic plants are not at risk under off-site drift or

surface runoff scenarios. However, surface runoff poses

low to moderate risk to special status terrestrial plants in

watersheds with clay and loam soils and 25 in/yr of

precipitation or more. Diflufenzopyr could be effective 

in suppression or management of several broadleaf

weeds in native perennial grasslands when applied at

least 100 feet from non-target plant populations of 

interest or 900 feet from special status plant species 

(Table 4-12). Its use should be avoided in areas 

containing special status plants that have clay and/or 

loam soil types and moderate to high levels of 

precipitation. 

Diquat 

Diquat is a non-selective, contact herbicide for weed

management in non-cropland and aquatic areas. The 

BLM proposes to use diquat only in aquatic areas. 

Diquat is a cell membrane disrupter that is activated by 

exposure to sunlight to form oxygen compounds that

damage cell membranes. As a non-selective aquatic 

herbicide, diquat is best used to control aggressive 

invasive plant species in water bodies where few native 

plant species exist. Appropriate target species include 

Eurasian watermilfoil, water-thyme, water hyacinth, and

giant salvinia. Diquat does kill plant parts on contact,

but it does not kill the roots of the plant, and therefore is 

often used for single-season control of submersed

aquatic plants (Washington Department of Ecology 

2004). 

Accidental spray and spill of diquat poses moderate to 

high risk to terrestrial plants at the typical application 

rate and high risk at the maximum application rate 

(Table 4-11). Accidental sprays or spills of diquat pose 

a high risk to aquatic plants. Off-site drift of diquat to 

terrestrial areas poses a low risk to terrestrial plants,

which is associated with aerial applications and ground

applications at short buffer distances. Non special status 

terrestrial plants are not at risk if diquat is applied 

aerially or from the ground with buffers greater than 

1,200 feet (Table 4-12). As a non-selective aquatic

herbicide, diquat should not be applied in water bodies 

where there are aquatic plants of concern. Riparian

species within 900 feet of the water body should also be 

considered, as they may be at risk from off-site drift of

diquat; this risk would be lessened if diquat were 

applied via a ground application method. Diquat should

not be used if special status riparian plants are present. 

Diuron

Diuron is a non-selective, broad-spectrum herbicide,

effective both pre- and post-emergence. Diuron disrupts 

photosynthesis by blocking electron transport and the 

transfer of light energy, thereby resulting in plant death. 

Because of its non-selective nature, diuron may be

highly effective in areas where a variety of invasive 

species dominate and where very few non-target plants 

exist. Diuron is best used in areas where bare ground is 

desired (e.g., around fences and structures). 

Risk assessments generally predicted high risk to 

terrestrial and aquatic plants under accidental direct 

spray and spill scenarios (risk to typical terrestrial plant

species is moderate at the typical application rate; Table

4-11). Off-site drift of diuron presents a risk to special 

status terrestrial plants under all modeled scenarios,

with higher risk at the maximum application rate and at 

shorter buffer distances. Typical terrestrial plant species 

are also at risk under scenarios of off-site drift when 

diuron is applied at the maximum application rate and

with buffer distances less than 900 feet, and when

applied at the typical application rate with a high boom

and a buffer less than 100 feet. Off-site drift of diuron 

poses low to moderate risk to aquatic plants under most

application scenarios. In some cases application with a 

900-foot buffer does not pose a risk to aquatic plants,

depending on the application rate, the application

height, and the type of water body (Table 4-12). In a 

few cases (clay soils with more than 50 in/yr 

precipitation and loam soils with 250 in/yr), surface 

runoff of diuron poses a low risk to special status 

terrestrial plants. Surface runoff poses a moderate to

high risk to aquatic plants in ponds under the majority

of scenarios. Aquatic plants in the stream are at low risk

from surface runoff under most scenarios. Diuron is 

most safely applied with spot applications at the typical

application rate, especially in the vicinity of water 

bodies with aquatic plants of interest or near special 

status plants. 

Fluridone 

Fluridone is a slow-acting, broad-spectrum, systemic

aquatic herbicide that can be used selectively at low 

concentrations. Fluridone kills target plants by causing

the breakdown of chlorophyll, thereby preventing plants 

from synthesizing food. Because of this mode of action, 

fluridone must remain in contact with the target aquatic

species for an extended period of time, depending on

the species, for effective control. Fluridone is one of 

two new herbicides proposed for use by the BLM that

can effectively target harmful and invasive underwater 

BLM Vegetation Treatments Using Herbicides 4-52 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

aquatic plants; in particular, it would be used to manage 

water-thyme and Eurasian watermilfoil. Often these

aquatic invasives are great disrupters of aquatic 

ecosystem function. Fluridone may be most effectively

used when smaller water bodies are heavily or 

completely infested with these invasive plants—i.e., in

situations where complete eradication is possible in 

order to prevent the spread of remaining plants. 

However, at low concentrations, some native aquatic

plants, especially pondweeds, may escape harm

(Washington Department of Ecology 2004). 

Risk to terrestrial plants from fluridone application

could not be evaluated because of a lack of toxicity

testing. Aquatic plants are at low risk under scenarios

involving an accidental spill of fluridone mixed for the 

maximum application rate (Table 4-11). Because the

risks associated with off-site drift of fluridone to 

terrestrial plants are unknown, care should be taken in 

the application of fluridone, even though it appears to be 

safe to non-target aquatic plants if used as registered. 

Off-site deposition rates of fluridone suggest that small

percentages (0-24%) of the chemical would drift off 

site, potentially affecting terrestrial plants. Drift would 

be lowest (0-2%) when fluridone is applied on the water 

surface with buffer distances of 100 feet or more. The 

low toxicity of fluridone to aquatic plants suggests that 

it may not be effective against certain aquatic species. 

Rates and application methods must be adjusted 

according to target species identity to achieve 

management goals, while maintaining care to minimize 

off-site drift, particularly if non-target plants of interest

are within 100 feet of the application site (Table 4-12). 

Imazapic

Imazapic, an ALS-inhibitor, is a selective, systemic

herbicide used on annual and perennial broadleaf weeds 

and grasses. Like other ALS-inhibitors, imazapic is 

quite active, with only small concentrations required to

kill target plants. Due to its activity, imazapic may be

highly effective, particularly in spot applications, at 

controlling aggressive invasive species that have not 

responded to other herbicides or treatment methods. 

Several short-term studies have shown that preemergent/fall application of imazapic can be effective in

controlling invasive species (e.g., leafy spurge) while 

improving the establishment of native grassland plants 

(Beran et al. 1999; Markle and Lym 2001; Masters et al. 

2001; Kirby et al. 2003). However, despite its 

selectivity, studies have found that some plants that are 

supposedly tolerant to imazapic are likely to be injured

if they are directly sprayed by the herbicide at the

typical application rate (many native bunchgrasses 

remain tolerant [SERA 2001b]). Imazapic is proposed

for BLM use in fuels reduction because of its 

effectiveness against downy brome, and in forested

rangeland management because of its effectiveness 

against hoary cress and perennial pepperweed. 

Accidental direct spray and spill scenarios pose a low 

risk to terrestrial plants for applications at the typical 

application rate, and a moderate risk for applications at

the maximum application rate (Table 4-11). Aquatic 

plants are at moderate to high risk for adverse effects 

from accidents for applications at the maximum 

application rate, and low to moderate risk for 

applications at the typical application rate. There is no

acute risk to aquatic plants in a water body under typical

application rate scenarios (ENSR 2005h). When 

imazapic is applied aerially with buffers of 300 feet or 

less, off-site drift presents low risk to terrestrial plants. 

Aquatic plants are generally not at risk from off-site

drift of imazapic, except when applied aerially at the

maximum application rate with a buffer of 100 feet or

less (Table 4-12). Surface runoff of imazapic presents a 

low risk to aquatic plants in ponds for applications at the 

maximum application rate in areas with sandy soils and

precipitation greater than 25 in/yr. Overall, application 

of imazapic at the typical application rate, with buffers 

greater than 300 feet during aerial application, should 

not pose a risk to non-target plants. 

Overdrive®

Overdrive® is an herbicide formulation containing the

active ingredients dicamba and diflufenzopyr. It is a 

selective, systematic herbicide for the management of 

broadleaved weeds pre- or post-emergence. 

Diflufenzopyr inhibits the transport of auxin (a hormone 

that regulates plant growth and development), and

dicamba functions as a synthetic auxin. When used

together, these chemicals disrupt plant hormone balance 

and protein synthesis (Retzinger and Mallory-Smith

1997). Because Overdrive

® targets dicotyledons 

(broadleaved plants), it can be used in native grasslands,

particularly if invasive broadleaves are more of a

problem than invasive annual grasses. This herbicide

provides a good option for vegetation and wildlife 

habitat management in forested rangeland settings. It

can be used to control several broadleaf species,

including burningbush, pigweed, Russian thistle, 

biennial thistles (bull, musk, and Scotch), knapweeds 

(diffuse, Russian, and spotted), and field bindweed. 

Risk assessments predicted moderate to high risk to 

terrestrial and aquatic plants under direct spray and 

accidental spill scenarios (Table 4-11). Off-site drift of

Overdrive® poses a low risk to special status terrestrial

BLM Vegetation Treatments Using Herbicides 4-53 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES 

TABLE 4-12

Buffer Distances to Minimize Risk to Vegetation from Off-site Drift of BLM-evaluated Herbicides 

Application 

Scenario BROM1 CHLR1 DICM1 DIFLU1 DIQT1 DIUR1 FLUR1 IMAZ1 OVER1 SULF1 TEBU1

Buffer Distance (feet) from Non-target Aquatic Plants 

Typical Application Rate 

Aerial NA 0 NA NA NE NA NE 0 NA 1,300 NE

Low Boom2 100 0 0 100 NE 900 NE 0 100 900 0

High Boom2 900 0 0 900 NE 1,000 NE 0 900 900 0

Maximum Application Rate 

Aerial NA 300 NA NA NE NA NE 300 NA 1,500 NE

Low Boom2 900 0 0 900 NE 1,000 NE 0 900 900 0

High Boom2 900 0 0 900 NE 1,000 NE 0 900 900 0

Buffer Distance (feet) from Non-target Terrestrial Plants 

Typical Application Rate 

Aerial NA 1,350 NA NA 1,200 NA NE 0 NA 0 NE

Low Boom2 950 900 1,000 100 100 0 NE 0 0 0 0

High Boom2 950 900 1,000 100 900 100 NE 0 100 0 0

Maximum Application Rate 

Aerial NA 1,350 NA NA 1,200 NA NE 900 NA 0 NE

Low Boom2 1,000 1,000 1,050 100 900 200 NE 0 100 0 50

High Boom2 1,000 1,000 1,050 100 900 500 NE 0 100 0 50

Buffer Distance (feet) from Threatened, Endangered, and Sensitive Plants 

Typical Application Rate 

Aerial NA 1,400 NA NA 1,200 NA NE 0 NA 1,500 NE

Low Boom2 1,200 1,000 1,050 100 900 1,000 NE 0 100 1,100 0

High Boom2 1,200 1,000 1,050 900 900 1,000 NE 0 900 1,000 50

Maximum Application Rate 

Aerial NA 1,400 NA NA 1,200 NA NE 900 NA 1,500 NE

Low Boom2 1,200 1,050 1,050 900 1,000 1,000 NE 0 900 1,100 100

High Boom2 1,200 1,000 1,050 900 1,000 1,000 NE 0 900 1,000 500

1 BROM = Bromacil; CHLR = Chlorsulfuron; DICM = Dicamba; DIFLU = Diflufenzopyr; DIQT = Diquat; DIUR = Diuron; FLUR = Fluridone;

IMAZ = Imazapic; OVER = Overdrive®; SULF = Sulfometuron methyl; and TEBU = Tebuthiuron. 2 High boom is 50 inches above ground and low boom is 20 inches above ground.

NE = Not evaluated and NA = not applicable.

Buffer distances are the smallest modeled distance at which no risk was predicted. In some cases, buffer distances were extrapolated if the largest

distance modeled still resulted in risk, or interpolated if greater precision was required. 

plants at distances greater than 100 feet (Table 4-12).

Surface runoff generally does not pose a risk to nontarget plants, except to special status terrestrial species

under scenarios in which Overdrive® is applied in 

watersheds with silt and clay soils and precipitation 

greater than 25 in/yr, and to aquatic species in

watersheds with silt, clay, and sand soils and 

precipitation greater than 25 in/yr or in all soil types 

with precipitation greater than 200 in/yr (at the 

maximum application rate). It appears that Overdrive®

can be safely applied in areas that do not contain special 

status plants and where non-target plants of interest are 

not broadleaved (i.e., they are monocotyledons such as 

grasses and lilies).

Sulfometuron Methyl 

Sulfometuron methyl, an ALS-inhibitor, is a broadspectrum, pre- and post-emergent herbicide used to

target broadleaf weeds and annual and perennial grass 

species. Like chlorsulfuron and imazapic, sulfometuron

methyl is highly active, but is less selective than 

chlorsulfuron. Therefore, sulfometuron methyl should

not be used in situations where selectivity is required, 

but could be useful in areas with multiple highly

aggressive invasive species that have not responded to 

other herbicides or treatment methods. Sulfometuron 

methyl is effective in the management of downy brome, 

hoary cress, and perennial pepperweed. As with other 

highly active herbicides, care should be taken to apply

BLM Vegetation Treatments Using Herbicides 4-54 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

sulfometuron methyl using methods and under 

conditions that limit the potential for spread off site. 

For applications of sulfometuron methyl at the 

maximum application rate, accidental direct spray and

spill scenarios pose a high risk to aquatic species and

special status terrestrial plant species and a low risk to 

typical plant species (Table 4-11). Off-site drift of 

sulfometuron methyl presents a high risk to special 

status terrestrial plants, but no risk to typical plants 

species under modeled scenarios. This prediction 

contradicts past reported incidents of damage to crops 

resulting from off-site drift covering large distances 

from the site of application. In addition, other risk 

evaluations have reported potential damage to nontarget plants even when applied at distances of greater 

than 900 feet (Table 4-12). Aquatic plants are at low 

risk under off-site drift scenarios, with some higher 

levels of risk at shorter buffer distances. Aquatic plants 

are not at risk under off-site drift scenarios if a 

minimum 900-foot buffer distance is used. Surface 

runoff of sulfometuron methyl poses a low to moderate 

risk to special status terrestrial plants, if applied in 

watersheds with clay or silt soils or loam soils and 100

in/yr precipitation or greater. Aquatic plants in ponds 

are at low to moderate risk under most surface runoff 

scenarios. Aquatic plants in streams are at low to 

moderate risk in watersheds with sand soils or greater

than 50 in/yr of precipitation. Sulfometuron methyl

should not be applied in the vicinity of special status

plant species. In addition, this active ingredient should

be applied with buffers greater than 900 feet from

aquatic areas and non-target terrestrial plants of interest. 

Furthermore, it has been shown that application in areas 

with dry soils that have been recently disturbed, and 

therefore are more susceptible to off-site drift, can be 

problematic. However, application in watersheds with 

high probability for surface runoff (sandy soils, high

precipitation) could also pose an additional risk to 

aquatic plants. 

Tebuthiuron 

Tebuthiuron is a relatively non-selective herbicide 

absorbed by plant roots through the soil for use against

broadleaved and woody weeds and grasses. Tebuthiuron 

disrupts photosynthesis by blocking electron transport

and the transfer of light energy. Because of its nonselectivity, tebuthiuron should be used in areas 

dominated by invasive species, particularly woody 

invasives, such as in rangelands or ROWs invaded by 

shrubs, trees, and other undesirable species. The 

strength of this herbicide is its use as a habitat modifier 

in the BLM sagebrush management program. At low

rates of application, tebuthiuron is used to thin 

sagebrush, creating a more favorable habitat for 

sagebrush-dependent species. 

Accidental direct spray and spill scenarios pose a high

risk to terrestrial plants for applications of tebuthiuron at 

the maximum application rate, and a moderate risk for 

applications at the typical application rate (Table 4-11). 

Aquatic plants are at high risk under spill scenarios,

aquatic plants in ponds are at low to moderate risk

under direct spray scenarios, and aquatic plants in

streams are at moderate to high risk under direct spray 

scenarios. Off-site drift from applications at a distance

of less than 900 feet poses a low risk to terrestrial plants 

under several exposure scenarios, mostly for 

applications at the maximum application rate and at

distances of less than 100 feet (Table 4-12). Aquatic 

plants are not at risk under off-site drift scenarios;

however, surface runoff poses a risk to aquatic plants in 

ponds under most scenarios when tebuthiuron is applied 

at the maximum application rate, and under select

scenarios when applied at the typical application rate 

(e.g., most sand soils). Aquatic plants in streams are at

risk under a few surface runoff scenarios involving the

maximum application rate (e.g., sand soils with 

precipitation 50 in/yr and greater, and large application 

areas). Threatened, endangered, and sensitive terrestrial

plants in watersheds with clay and silt soils and

precipitation of 50 in/yr and greater are also at risk

under surface runoff scenarios. Most risk to vegetation

from registered use of tebuthiuron can be avoided by

applying at the typical application rate, using buffers of 

more than 100 feet, and avoiding application near 

special status species. 

Impacts of Forest Service-evaluated Herbicides

The following information for eight herbicides proposed

for use by the BLM is taken from ERAs prepared by the 

Forest Service to support assessment of the 

environmental consequences of using these herbicides 

in Forest Service vegetation management programs. 

Because the Forest Service completed these ERAs prior 

to the completion of this PEIS, the BLM has used these 

ERAs to assess the potential ecological impacts of 

vegetation treatments with these herbicides in future

management activities. The BLM previously evaluated 

and approved these eight herbicides in earlier EISs. As 

part of their risk assessments, the Forest Service

developed worksheets, which allowed the BLM to 

assess risks of the herbicides using BLM maximum 

application rates and LOCs (rather than the Forest

Service rates and LOCs), so that the risk assessment

process for the Forest Service-evaluated herbicides

BLM Vegetation Treatments Using Herbicides 4-55 June 2007 

Final Programmatic EIS
ENVI

BLM 

Final Pr

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-56 June 2007 

ogrammatic EIS 

parallels the BLM process as much as possible. 

However, risk scenarios modeled for terrestrial plants 

may be different than those modeled in BLM ERAs, 

depending on the specificity of available toxicity data. 

The assessment of impacts below is presented using the 

Forest Service upper estimates of HQs to maximize the 

conservatism of the assessment. In addition, it should be 

noted that HQs developed by the Forest Service (as well 

as the BLM) are already conservative for many reasons 

(e.g., use of most sensitive values for exposure and 

dose/response assessments). 

2,4-D 

2,4-D is a plant growth regulator that acts as a synthetic 

auxin hormone. 2,4-D alters the metabolism and growth 

characteristics of plants, often causing a proliferation of 

abnormal growth that interferes with the transport of 

nutrients throughout the plant. Broad-leaved plants are 

more susceptible to the effects of 2,4-D than narrowleaved plants, such as grasses. Plant community 

diversity studies have shown that 2,4-D can be 

effectively used in invasive species management 

without significantly affecting species diversity (USDA 

Forest Service 2005). This herbicide has limited 

residual activity and limited effectiveness on perennial 

species, but it does have some effectiveness in 

managing biennial thistles (bull, musk, Scotch) in 

forested rangeland situations, possibly for the 

enhancement of wildlife species. 2,4-D may also be 

used in riparian and aquatic areas. It is effective on 

broadleaved plants, such as Eurasian watermilfoil, and 

may be used in spot treatments at the labeled rate 

without substantially affecting native aquatic plants 

(Washington Department of Ecology 2004). 

The principal hazard to non-target plants is unintended 

direct deposition or spray drift of 2,4-D (SERA 1998). 

Non-target plants that are accidentally sprayed at 

normal application rates are likely to be damaged (Table 

4-13). Although off-site drift exposure scenarios were 

not directly modeled, ERAs predicted that drift of 2,4-D 

following low-flight agricultural application would 

result in deposition of the herbicide at 5% of the 

application rate 100 feet downwind from the application 

site. Thus, at the maximum BLM application rate for 

terrestrial scenarios (1.9 lbs a.i./ac), the deposition at 

100 feet would be 0.1 lbs a.i./ac, decidedly less than the 

lowest rate expected to affect sensitive plants (0.5 lbs 

a.i./ac). If 2,4-D were to drift off site during aquatic 

applications at the maximum application rate (8 lbs 

a../ac), the deposition at 100 feet would be 0.4 lbs 

a.i./ac. This is slightly below the minimum application 

rate used by the Forest Service, suggesting that at a 

buffer distance of 100 feet, damage to less sensitive 

plants (e.g., grasses) is unlikely. The effects on sensitive 

plants (e.g., broadleaves) at this distance are less certain. 

At a buffer distance of 200 feet, herbicide deposition is 

predicted to be 2% of the application rate, resulting in 

deposition of 0.16 lbs a.i./ac, a concentration that is 

unlikely to affect non-target plants, when applied at the 

maximum application rate. Therefore, damage to offsite plants from terrestrial applications of 2,4-D at the 

maximum application rate plants is unlikely if buffer 

distances are at least 100 feet. For aquatic applications, 

a buffer of at least 200 feet should protect off-site plants 

from damage during applications at the aquatic 

maximum application rate. 

The toxicity of 2,4-D to aquatic plants is low at the 

typical application rate, but moderate at the maximum 

application rate. Risks are greater in cases of direct 

application to water bodies or accidental direct spills. 

One study suggested that 2,4-D application to water 

bodies may result in adverse effects on aquatic 

macrophytes, although the concentrations that inhibited 

shoot and/or root growth by 25% and 50% were below 

the expected environmental concentrations from typical 

use (Roshon et al. 1999). 

Clopyralid 

Clopyralid is a selective herbicide most effectively used 

post-emergence for the control of broadleaf weeds. 

Clopyralid is a plant growth regulator that is rapidly 

absorbed across leaf surfaces, and acts as a synthetic 

auxin hormone, causing a proliferation of abnormal 

growth that interferes with the transport of nutrients, 

which can then result in substantial damage to the plant, 

or death. The modeled BLM application rates were 0.35 

pounds acid equivalent per acre (lb a.e./ac; typical) and 

1 lb a.e./ac (maximum). Clopyralid would be considered 

for use in forested rangeland areas for the management 

of several weedy species, including diffuse and spotted 

knapweed, yellow starthistle, and bull, Canada, Scotch, 

and musk thistles. 

As expected, direct spray of clopyralid poses a high risk 

to sensitive plant species; direct spray also poses a low 

risk to tolerant plant species for applications at the 

maximum application rate (Table 4-13). Off-site drift of 

clopyralid from low-boom ground applications and 

aerial applications may cause damage to sensitive plant 

species at distances of about 500 feet from the 

application site, when applied at the typical application 

rate (SERA 1999), and at distances of greater than 900 

feet when applied at the maximum application rate
June 2007 

Final Programmatic EIS ogrammatic EIS TABLE 4-13 Ris

k Categori Categories Used to De ed to Describe 

Effects of Forest Ser Forest Ser

vice-evaluate ice-evaluated Her

bicides According to Exposure Scenario and Ecol

Exposure Scenario and Ecol

2,4-D

Clopyralid Glyphosate Hexazino

ne 1 Imazapyr Metsulfuron 

Glyphosate1 

Typ

Max Ty

p

Max Ty

p

Max Ty

p

Max Ty

p

Max Ty

p

Max T

Terrestrial PlantsDirect spray, sensitive plants NE3 N

E

H

H

M

H

N

E

N

E

H

H

H

H

H

Direct spray, tolerant plants NE NE 0 L

L

M

N

E

N

E

M

M

L

M

Off-site drift, low boom, sensitive 

L

M 0 L

L

L

L

M

L

M

M

plants 

N

E

N

E [4:6] [3:6] [5:6] [3:6] [3:6] [4:6] [4:6] [3:6] [4:6] [4:6] [3

Off-site drift, low boom, tolerant 0 0 0 0 0 0 0 0 0 0 plants 

N

E

N

E [6:6] [6:6] [6:6] [6:6] [6:6] [4:6] [6:6] [5:6] [6:6] [6:6] [6

M

H

L

M

M

H

M

H

Off-site drift, aerial, sensitive plants NE NE [2:6] [2:6] [3:6] [2:6] N

E

N

E [2:6] [2:6] [2:6] [2:6] [3

0 0 0 0 0 0 0 0 

Off-site drift, aerial, tolerant plants NE NE [6:6] [6:6] [6:6] [5:6] N

E

N

E [4:6] [3:6] [5:6] [4:6] [6

0 0 0 0 0 0 0 0 

Surface runoff, sensitive plants NE NE [23:30] [22:30] [30:30] [30:30] N

E

N

E [18:30] [18:30] [21:30] [18:30] [21

0 0 0 0 0 0 0 0 

Surface runoff, tolerant plants NE NE [30:30] [28:30] [30:30] [30:30] N

E

N

E [30:30] [30:30] [25:30] [22:30] [30

Aquatic Pla

nts

Accidental spill, sensitive macrophytes

N

E

N

E

H

H

M

M

N

E

N

E

H

H

H

H 

Accidental spill, sensitive algae NE NE

L

L

N

E

N

E

N

E

N

E

M

H

M

H

M

Accidental spill, tolerant algae NE NE 0 0 N

E

N

E

N

E

N

E 0 0 L

M 

Acute exposure, sensitivemacrophytes

L

M 0 0 0 0 H

H

L

L

L

L 

Acute exposure, sensitive algae 

N

E

N

E 0 0 N

E

N

E

N

E

N

E 0 0 0 0 

Acute exposure, tolerant algae NE NE 0 0 N

E

N

E

N

E

N

E 0 0 0 0 

Chronic exposure, sensitivemacrophytes 0 0 0 0 0 0 M

H 0 0 0 0 

Chronic exposure, sensitive algae NE NE 0 0 N

E

N

E

N

E

N

E 0 0 0 0 

Chronic exposure, tolerant algae NE NE 0 0 N

E

N

E

N

E

N

E 0 0 0 0 

1 Risk categories for the 

more toxic formulations are presented here. 2 Typ = Typical application rate; and Max = Maximum application rate. 3 0 = No risk (

HQ < LOC); L = Low risk (HQ = 1 to 10 x LOC); M = Moderate Risk (

HQ = 10 to 100 x L

OC); H = High risk (HQ > 100 LOC); an

categories are based on upper estimates of hazard quotients and the BLM L

OC of 1.0. The reader should consult the text of this section of the in

assessments to evaluate risks at central esti

mates of hazard quotients. If more than one scenario is involved in an exposure pathway (i.e., off-site drift 

number of scenarios with the given risk category (out of the total number of evaluated scenarios) is displayed in parentheses. The reported risk category 

RQs for each exposure pathway. As a result, risk may be higher than the reported risk category for some scenarios within each category. The reader ssection of the Forest Service risk assessment worksheets (SE

RA 2005b) to determine the specific scenarios that result in the displayed level of risk for a 

BLM Vegetation Treatments Using Herbicides 4-57
ENVIRONMENTAL CONSEQUENCES

(Table 4-14). Hazard quotients are greater for aerial

applications (moderate to high risk at smaller buffer 

distance and higher application rates) than low-boom 

ground applications (low to moderate risk). Tolerant

species are not at risk under off-site drift scenarios. In

addition, the Forest Service risk assessment states that

damage to non-target species via off-site drift could

probably be minimized or avoided during the 

application process (SERA 1999). For instance, welldirected ground applications (e.g., spot applications) 

conducted under conditions that do not favor off-site

drift would probably have no impact on off-site plant 

species. 

Clopyralid tends to leach into the soil column with rain,

where it is rapidly degraded, except in arid soils with

low microbial populations. It is not readily absorbed by 

roots, suggesting that surface runoff is unlikely to affect

off-site vegetation. However, sensitive plant species 

face low to moderate risk under scenarios involving 

surface runoff of clopyralid applied at the maximum 

application rate in clay soils, which allow minimal

infiltration, at most precipitation levels (i.e., greater

than 10 in/yr). Wind erosion of treated soil in arid

climates could cause damages to non-target vegetation 

within 200 to 900 feet of the application site. 

Clopyralid is relatively non-toxic to aquatic plants. It is 

not likely to affect aquatic plants via off-site drift or 

surface runoff pathways. However, accidental spills 

may result in temporary growth inhibition of aquatic 

plants; spills would present a high risk to aquatic

macrophytes and a low risk to sensitive algae species. 

Overall, effects to non-target vegetation from normal

application of clopyralid are likely to be limited to

sensitive plant species in or very near the treatment area. 

Glyphosate 

Glyphosate is a non-selective systemic herbicide that 

can damage all groups or families of non-target plants to 

varying degrees. Glyphosate inhibits the production of 

aromatic amino acids and certain phenolic compounds. 

This leads to a variety of toxic effects in plants, 

including the inhibition of photosynthesis, respiration, 

and nucleic acid synthesis, thereby resulting in cellular 

disruption, decreased growth, and death at sufficiently 

high levels of exposure. Because of its non-selective

nature, glyphosate may be highly effective in spot 

applications or in areas where a variety of invasive

species dominate and where very few non-target plants 

exist. Glyphosate is best used in areas where bare 

ground is desired (e.g., around fences and structures);

however, it has low residual activity, so it would not be

effective for an extended period of time. Glyphosate 

may also be used in riparian and aquatic habitats on 

shoreline and floating-leaved species such as purple 

loosestrife, giant reed, cattails, and water lilies. 

Exposure via direct spray would pose a moderate to

high risk to sensitive plant species and low to moderate

risk to tolerant plant species (Table 4-13). In addition, 

one field study suggests that drift from glyphosate could

affect long-term sustainability of populations of lichens 

and bryophytes (Newmaster et al. 1999). Unintended

drift, particularly following aerial application, is one of 

the more plausible exposure scenarios for non-target

terrestrial plants (SERA 2003a). The estimates for offsite drift encompass plausible exposures attributable to 

wind erosion. For relatively tolerant species, there is no

indication that glyphosate is likely to result in damage at 

distances as close as 50 feet from the application site 

(Table 4-14). Low to moderate risk to sensitive species 

is predicted for ground broadcast and aerial applications 

at the maximum application rate, at off-site distances of

100 feet or less. Drift from ground broadcast

applications at the typical application rate would pose a 

low risk to sensitive species within 25 feet, and drift

from aerial application at the typical application rate 

would pose a low risk to sensitive species within 300 

feet. It should be noted, however, that all of these drift

estimates are based on low-boom ground or aerial

broadcast sprays. If glyphosate was directly applied

using a backpack sprayer, little if any damage due to 

drift would be anticipated. 

Plant species are not likely to be affected by runoff of 

glyphosate under any conditions; because glyphosate

absorbs strongly to soil, plant roots do not readily 

absorb it. A field study conducted using glyphosate 

found no effect to plant diversity in an 11-year 

examination of site-preparation using herbicides, though

structural composition and perennial species presence

were altered. These changes may have ecological 

implications if species lost (e.g., native huckleberry or 

cherry) were heavily fed upon by wildlife or were used

in traditional gathering (Miller et al. 1999). 

There is little indication from the risk assessment that

adverse effects to aquatic plants are plausible for typical

applications of glyphosate (SERA 2003a). A single 

study suggests that glyphosate application may result in 

adverse effects on aquatic macrophytes (Roshon et al. 

1999). In addition, the risk assessment indicates that 

accidental spills pose a moderate risk to aquatic

macrophytes. 

BLM Vegetation Treatments Using Herbicides 4-58 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Hexazinone 

Hexazinone is an “s-triazine” herbicide that inhibits 

photosynthesis and the synthesis of RNA, proteins, and

lipids. Although some foliar absorption may occur, the 

major route of exposure involves hexazinone moving 

from the soil surface to the root system of plants, where,

in most species, it is readily absorbed and translocated 

throughout the plant. The differential toxicity of 

hexazinone to plants is based on variations in the ability

of different plants to absorb, degrade, and eliminate the 

herbicide. The BLM modeled application rates of 1 lb 

a.i./ac (typical rate) and 8 lbs a.i./ac (maximum rate).

Hexazinone is effective against woody species (e.g., 

juniper, mesquite, cottonwood), and therefore is not

used in forested rangeland areas. It may be used for 

fuels reduction. 

As with other herbicides, hexazinone may affect nontarget plants through accidental direct spray and off-site

drift scenarios (SERA 1997). During aerial applications 

at the typical application rate and at distances of 100 

feet or less from the application site, some damage to

sensitive non-target vegetation is plausible due to drift 

of liquid formulations (low risk). At maximum 

application rates, sensitive species may be at low to 

moderate risk under scenarios involving drift following

aerial applications at distances of 500 feet or less (no

risk is predicted at 900 feet from the application site; 

Tables 4-13 and 4-14). There would be a low risk to 

tolerant species under scenarios involving aerial drift at

maximum application rates at distances of 50 feet or 

less (no risk is predicted at 100 feet). Ground

applications of granular formulations or spot treatments 

with liquid applications of hexazinone should be 

associated with minimal drift; however, there are no

studies available in the literature to support this 

speculation. In addition, soil contamination and

consequent transport of hexazinone to off-site nontarget vegetation may occur. Based on the limited doseresponse data available for plants, the levels of exposure 

detected are likely to be toxic to non-target as well as 

target vegetation. The magnitude of any observed

effects will be determined predominantly by local 

conditions, particularly soil type and rainfall. In porous 

and/or sandy soils with low levels of organic matter and 

under conditions of high rainfall, adverse effects to offsite vegetation are most plausible. 

Aquatic plants are at moderate to high risk under acute 

and chronic exposure scenarios involving both the 

typical and maximum application rates. Aquatic algal 

species are also sensitive to hexazinone exposure. 

Furthermore, it is likely that aquatic macrophytes are 

sensitive based on the effects of hexazinone on algae

and terrestrial plants (SERA 1997; Roshon et al. 1999). 

Imazapyr

Imazapyr is an ALS-inhibiting herbicide used in the 

control of a variety of grasses, broadleaf weeds, vines, 

and brush species. Although post-emergence application 

is more effective than pre-emergence application,

toxicity can be induced either through foliar or root

absorption. Due to its activity, imazapyr may be highly

effective in controlling aggressive invasive species that

have not responded to other herbicides or treatment

methods. The strength of this herbicide is in the

management of saltcedar in riparian zones. In addition,

imazapyr can be used to treat emergent plants such as 

spartina, reed canarygrass, and phragmites, and floatingleaved plants such as water lilies. BLM application rates 

modeled were 0.45 lb a.i./ac (typical rate) and 1.5 lbs 

a.i./ac (maximum rate). 

Imazapyr is an effective herbicide, and even “tolerant”

plants that are directly sprayed with imazapyr at normal

application rates are likely to be damaged (SERA 

2004d). The risk assessment predicted a high risk to

sensitive plant species and a moderate risk to tolerant

species under direct broadcast spray scenarios (Table 4-

13). Off-site drift of imazapyr could cause damage to 

sensitive plant species at distances of less than 900 feet

from the application site after both ground broadcast 

(low boom) or aerial applications at the typical

application rate, and possibly at distances greater than

900 feet after applications at the maximum application 

rate (low to moderate risk for ground applications and 

low to high risk for aerial applications at both 

application rates; 900 feet was the maximum distance 

modeled), depending on site-specific conditions, such as 

wind speed and foliar interception (Table 4-14).

Tolerant species are not likely to be affected by off-site

drift of imazapyr, except under drift scenarios following

1) low boom ground application at the maximum 

application rate at distances of 25 feet or less, or 2)

aerial application at the maximum application rate at

distances of 100 feet or less. In addition, wind erosion

of soil contaminated with imazapyr could lead to 

adverse effects to sensitive plants, particularly in

relatively arid environments and where local soil 

surface and topographic conditions favor wind erosion. 

However, the risk assessment estimated daily soil losses 

from erosion to be 0.001% to 0.l% of the application

rate, similar to loss predicted from off-site drift at 

distances greater than 500 feet from the application site 

(SERA 2004d). 

BLM Vegetation Treatments Using Herbicides 4-59 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

When applied to areas in which runoff is favored (e.g., 

clay soils over a wide range of rainfall rates or loam

soils at annual rainfall rates of 100 in/yr or more), 

damage from runoff appears to be more likely than

damage from drift. For applications at the typical

application rate, the risk assessment predicted low risk

to plants at sites with clay soils and 15 to 20 in/yr 

precipitation, and with loam soils and more than 100

in/yr precipitation; moderate risk to plants at sites with

clay soils and 25 to 150 in/yr precipitation; and high risk

to plants at sites with clay soils and more than 200 in/yr 

precipitation. For applications at the maximum 

application rate, the risk assessment predicted moderate 

risk to plants on sites with clay soils and 15 to 25 in/yr 

precipitation, and to plants on sites with loam soils and 

more than 100 in/yr precipitation; and high risk to plants 

on sites with clay soils and more than 50 in/yr

precipitation. Residual soil contamination with 

imazapyr could be prolonged in some areas, possibly 

resulting in substantial growth inhibition (Rahman et al. 

1993 cited in SERA 2004d). In relatively arid areas in

which microbial degradation may be the predominant

factor in the decline of imazapyr residuals in soil,

residual toxicity to sensitive plant species could last for 

several months to several years (estimated at 10 months 

to 5.5 years [SERA 2004d]). 

Effects to aquatic plants are also plausible. Peak 

concentrations of imazapyr in surface water could be 

associated with adverse effects to some aquatic 

macrophytes (low risk at both application rates). Longer 

term concentrations of imazapyr, however, are 

substantially below the level of concern (LOC; SERA

2004d). 

Unicellular algae do not appear to be at risk from 

routine imazapyr application (Roshon et al. 1999, 

SERA 2004d). Accidental spills of imazapyr pose a

high risk to aquatic macrophytes and a moderate to high

risk to sensitive algae species. 

Metsulfuron Methyl 

Metsulfuron methyl is a selective ALS-inhibiting 

herbicide used pre- and post-emergence in the control of 

many annual and perennial weeds and woody plants. 

Due to its potency, metsulfuron methyl may be highly

effective in controlling aggressive invasive species that

have not responded to other herbicides or treatment

methods. Metsulfuron methyl can be used in forested 

areas for the management of wildlife habitat and for the 

control of invasive plant species such as hoary cress, 

perennial pepperweed, biennial thistles (bull, musk, and

Scotch), and yellow starthistle. The BLM application 

rates modeled were 0.03 lb a.i./ac (typical rate) and 0.15

lb a.i./ac (maximum rate). 

For terrestrial plants, the dominant factor in determining 

the risk characterization is the potency of metsulfuron

methyl relative to the application rate (SERA 2004e). 

The typical application rate is over 800 times greater 

than the no observable effects concentration (NOEC) in

the vegetative vigor (direct spray) assay of the most

sensitive non-target species and approximately 8 times 

greater than the NOEC for the most tolerant species in

the same assay. Exposure via direct spray poses a high

risk to sensitive species and a low to moderate risk to

tolerant species (Table 4-13). Damage to sensitive nontarget species could be expected in ground broadcast

applications at distances of about 900 feet from the 

application site at the typical application rate in areas in 

which off-site drift is not reduced by foliar interception 

(Table 4-14; SERA 2004e). Risks to sensitive nontarget terrestrial plants from off-site drift are slightly

higher for aerial applications (low to high risk) than for 

low-boom ground applications (low to moderate risk). 

In addition, tolerant plants face low risk from aerial

applications with buffers of 25 feet at the typical

application rate and 50 feet at the maximum application 

rate. Directed foliar applications (i.e., via backpack 

sprayer) may reduce the risk of off-site drift by an 

unquantifiable amount (SERA 2004e). 

Runoff of metsulfuron methyl could be substantial 

under favorable conditions. In watersheds with clay 

soils and 15 to 250 in/yr of precipitation, sensitive 

terrestrial plants face mostly high risk from exposure via

runoff; tolerant plants face low risks at the typical 

application rate with 50 to 250 in/yr precipitation, and

low to moderate risks at the maximum application rate 

with 15 to 250 in/yr precipitation. Plants in watersheds 

with loam soils face lower risks of damage via runoff of 

metsulfuron methyl, with risks only predicted for 

sensitive plants for applications at the typical rate at

sites with 100 in/yr precipitation, or for applications at 

the maximum application rate at sites with 100 to 250 

in/yr precipitation. 

In very arid regions, in which runoff might not be 

substantial, wind erosion could result in damage to offsite plant species, depending on local conditions. Daily 

soil losses as a result of wind erosion range from 

0.001% to 0.1% of the application rate—similar to offsite losses associated with drift at a distance of 500 feet

or more from the application site (SERA 2004e). 

The potential for damage to aquatic plants appears to be 

substantially less than the potential for damage to

BLM Vegetation Treatments Using Herbicides 4-60 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

TABLE 4-14

Buffer Distances to Minimize Risk to Vegetation from Off-site Drift of Forest Service-evaluated Herbicides

Application 

Scenario 2,4-D Clopyralid Glyphosate Hexazinone Imazapyr Metsulfuron

Methyl Picloram Triclopyr

Buffer Distance (feet) from Sensitive Plants 

Typical Application Rate 

Aerial NE 900 300 300 900 900 >900 500

Low Boom NE 900 50 NE 900 900 >900 300 

Maximum Application Rate 

Aerial NE 1,000 300 900 >900 >900 >900 >900

Low Boom NE 1,000 300 NE >900 >900 >900 >900 

Buffer Distance (feet) from Tolerant Terrestrial Plants 

Typical Application Rate 

Aerial NE 0 25 NE 100 50 25 NE

Low Boom NE 0 25 0 25 25 25 NE 

Maximum Application Rate 

Aerial NE 25 50 NE 300 100 50 NE

Low Boom NE 25 25 100 50 25 25 NE 

NE = Not evaluated. 

Buffer distances are the smallest modeled distance at which no risk was predicted. In some cases, buffer distances were extrapolated if the largest 

distance modeled still resulted in risk, or interpolated if greater precision was required. 

terrestrial plants, except under accidental spill scenarios. 

The HQs for routine acute and chronic exposure of

aquatic algae are all substantially below the LOC; i.e., 

there is no risk predicted (SERA 2004e). Aquatic 

macrophytes face low risk from acute exposure to

metsulfuron methyl at upper exposure limits. Accidental

spills would pose a high risk to aquatic macrophytes, 

moderate to high risk to sensitive algae species, and low 

to moderate risk to tolerant algae species. 

Picloram 

Picloram is a pyridine herbicide that acts as a plant 

growth regulator. It mimics naturally occurring plant

auxins or hormones in a manner that leads to

uncontrolled and abnormal growth that can in turn lead

to gross signs of toxicity or death (SERA 2003b). 

Picloram is more toxic to broadleaf and woody plants 

than grains or grasses (Extension Toxicology Network

1996c, SERA 2003b). Picloram is reportedly a good

choice for vegetation management in habitat 

modification situations because it can manage 

undesirable broadleaf species, including woody species, 

without injury to desirable grasses. It may be

particularly effective in maintaining species diversity in

grasslands invaded by spotted knapweed, where its

persistence in soils allows it to help initially suppress

spotted knapweed seedlings (Rice et al. 1997a); 

repeated application may be required to successfully

control knapweed due to its long-term seed viability 

(USDA Forest Service 2005). The resistance potential

of non-target plants to picloram has not been generally

documented; however, it is known that yellow 

starthistle has developed resistance to picloram, with

resistant plants being more tolerant by factors ranging 

from 3- to 35-fold compared to non-resistant plants 

(Fuerst et al. 1996 cited in SERA 2003b). The BLM 

application rates modeled were 0.35 lbs a.e./ac (typical

rate) and 1.0 lbs a.e./ac (maximum rate). 

Picloram can be considered highly selective to broadleaf 

plants, but may be toxic to many different plant species 

if directly sprayed at the typical application rate (SERA 

2003b). The risk assessment showed that direct spray of

picloram at the typical and maximum application rates 

poses a high risk to sensitive plant species and a low to 

moderate risk to tolerant plant species (Table 4-13).

Off-site drift of picloram associated with ground and 

aerial applications may cause damage to sensitive plant

species at distances of nearly 1,000 feet from the 

application site (risk is low to moderate for low-boom 

ground applications and low to high for aerial 

applications), depending on wind speed and foliar 

interception (Table 4-14; SERA 2003b). Tolerant plant

species would probably not be impacted by the drift of 

picloram (low risk is predicted only at the maximum 

application rate and a distance of 25 feet or less) and

might experience relatively little damage unless they

were directly sprayed. 

BLM Vegetation Treatments Using Herbicides 4-61 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Runoff may present a significant risk to sensitive nontarget terrestrial plant species under conditions in which

runoff is favored (mostly high risk is predicted in

watersheds with clay soil over a very wide range of 

rainfall amounts). Low risk is also predicted for 

sensitive plants in watersheds with loam soils and 100-

150 in/yr precipitation, and for tolerant species in

watersheds with clay soils and 150 to 250 in/yr 

precipitation, when picloram is applied at the maximum 

application rate. 

Daily soil losses due to wind erosion, expressed as a 

portion of application rate, could be in the range of 

0.00001 to 0.001. This is substantially less than off-site

losses associated with runoff from clay but similar to 

off-site losses associated with drift in the range of about 

200 feet to 900 feet. As with the drift scenarios, wind

erosion could lead to adverse effects in sensitive plant

species. Wind erosion of soil contaminated with

picloram is most plausible in relatively arid 

environments and where local soil surface and 

topographic conditions favor this type of event. 

Furthermore, there is high potential for picloram to

leach into groundwater in most soils (USDA Forest

Service 2005). In addition, because picloram persists in 

soil, non-target plant roots can take up picloram, which 

could impact revegetation efforts. 

The toxicity of picloram to aquatic plants varies 

substantially among different species; however, the only 

risks predicted by ERAs for routine exposures are a low 

risk to sensitive aquatic macrophytes from acute 

exposure to picloram at the maximum application rate, 

and a moderate risk to sensitive algae species from an

accidental spill of picloram. 

Triclopyr 

Triclopyr is a selective, systemic herbicide used on

broadleaf and woody species. Triclopyr mimics auxin, a 

plant growth hormone, thus disrupting the normal 

growth and viability of plants. Commercial formulations 

include two triclopyr derivatives, triclopyr acid and

triclopyr BEE, which were evaluated separately in the 

Forest Service risk assessment (including separate 

worksheet calculations). Triclopyr could be used to

manage woody riparian and aquatic species of interest, 

including saltcedar and willow. Triclopyr can be

effective as a spot treatment for Eurasian watermilfoil

because it is relatively selective for this species at low 

application rates. In addition, it is effective in riparian 

areas as a treatment for purple loosestrife because it 

does not damage native grasses and sedges (Washington 

Department of Ecology 2004). The BLM application

rates modeled in the worksheets were 1.0 lbs a.e./ac 

(typical rate) and 10.0 lbs a.e./ac (maximum rate). 

Because of the relatively low toxicity of triclopyr acid 

(terrestrial plant NOEC=0.333 lb/ac) compared to

triclopyr BEE (terrestrial plant NOEC = 0.003 lb/ac), 

the risk characterization for the former is much less

severe than the latter (SERA 2003c). Direct spray of

both formulations poses a high risk to plants (Table 4-

13). The potential impact of off-site drift associated

with broadcast applications varies substantially with the 

application rate. At the typical application rate, 

potentially damaging exposure could occur within about

300 feet of the application site. At the maximum 

application rate, damaging drift could occur at distances 

of greater than 900 feet from the application site (Table 

4-14; SERA 2003c). 

At the typical application rate, potentially damaging

runoff from triclopyr acid would be anticipated only

under relatively high rainfall conditions in watersheds 

with clay soils (low risk was predicted for sensitive and

tolerant species with rainfall of 200 in/yr or greater). 

While a lesser amount of triclopyr BEE will run off, low 

to moderate risk to plants is predicted for applications of 

this more toxic formulation, starting at relatively modest

rainfall rates (i.e., 15 to 25 inches per year) in all

modeled soil types (i.e., clay, loam, sand). At the

maximum application rate, damage due to runoff after 

the application of triclopyr acid would be expected at

annual rainfall rates as low as 25 inches per year in clay, 

loam, and sand soils (mostly low risk). For triclopyr 

BEE, low to high risk is predicted for applications in all

but the most arid areas. 

Both formulations of triclopyr have been found to

decrease the relative long-term abundance and diversity 

of lichens and bryophytes; normal application rates in 

aerial spraying were found to reduce abundance by 

75%, with colonists and drought tolerant species being 

less susceptible than later-successional mesophytic 

forest species (Newmaster et al. 1999). Triclopyr was

also found to inhibit growth of four types of 

ectomychorrhizal fungi associated with conifer roots at

concentrations of 1,000 parts per million (Estok et al. 

1989 cited in SERA 2003c). 

Aquatic stream plants are at low risk from routine acute 

exposure to triclopyr acid at the maximum application

rate. For longer-term exposures, there is no predicted

risk to aquatic plants associated with triclopyr TEA 

applications, even at the maximum application rate.

Triclopyr BEE is much more toxic to aquatic plants than 

triclopyr TEA under laboratory conditions; however, the

BLM Vegetation Treatments Using Herbicides 4-62 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

levels of exposure under field conditions would be less, 

even under acute scenarios because of the rapid 

hydrolysis of triclopyr BEE to triclopyr acid, as well as 

the lesser runoff of triclopyr BEE resulting from low 

water solubility and high affinity for soils (SERA 

2003d). Nonetheless, triclopyr BEE is projected to be 

somewhat more hazardous when used where runoff to 

open water may occur. Acute exposure poses a low risk

to aquatic stream plants under scenarios involving 

applications at the typical rate, and a moderate risk

under scenarios involving applications at the maximum 

rate. Accidental spill of triclopyr acid poses a low to

moderate risk to aquatic macrophytes and algae, 

whereas accidental spill of triclopyr BEE poses a high 

risk to aquatic macrophytes and algae. 

Impacts of Tank Mixes 

Risk assessment analysis of tank mixes indicates that

risks to plants vary by tank mix. Tank mixes of 

bromacil and sulfometuron methyl, and of imazapic and

diflufenzopyr, pose a greater risk to aquatic plants and 

special status terrestrial plants than bromacil, imazapic, 

or diflufenzopyr alone (risks to aquatic plants are not

greater versus imazapic applied alone). In some cases,

plant species may be particularly sensitive to these tank 

mixes. In addition, application of a tank mix of 

chlorsulfuron and diuron poses a greater risk to all plant 

receptors than application of chlorsulfuron alone (but 

not application of diuron alone). Risks to most receptors 

are also greater for a tank mix of sulfometuron methyl

and bromacil, versus sulfometuron methyl alone. 

There is some uncertainty in this evaluation because

herbicides in tank mixes may not interact in an additive

manner; the evaluation may overestimate risk if the 

interaction is antagonistic, or it may underestimate risk

if the interaction is synergistic. In addition, other 

products may also be included in tank mixes that

contribute to the potential risk. Based on the results of 

ERAs, precautions (e.g., increased buffers, decreased

application rates) should be taken when applying tank 

mixes to reduce the increased risks to plants associated

with these applications. 

Summary of Herbicide Impacts 

Evaluated in ERAs

The effects of herbicides on target plants depend on

their mode of action. Contact herbicides (e.g., diquat) 

only kill the plant parts that they touch, while 

translocated herbicides (e.g., dicamba) are transported 

throughout the plant. Herbicides that provide long-term

weed management (e.g., bromacil) affect plants when

they are present in the soil, with the degree of damage 

and non-selectivity often increasing with herbicide 

concentration (Holecheck et al. 1995). Selective

herbicides only affect certain plant species, whereas 

non-selective herbicides affect all or most plant species. 

The non-selective herbicides evaluated in this PEIS 

include bromacil, diquat, diuron, fluridone (except at 

low concentrations), glyphosate, sulfometuron methyl, 

and tebuthiuron. The other herbicides (2,4-D, 

chlorsulfuron, clopyralid, diflufenzopyr, hexazinone,

imazapic, imazapyr, metsulfuron methyl, Overdrive®, 

picloram, and triclopyr) exhibit some selective qualities 

and would be most effective when used to target certain 

plant species. Because of their selective nature, they

may be able to be used in areas where non-target

vegetation exists in communities with target vegetation.

In addition, diquat and fluridone would be used

exclusively for the management of aquatic plants; 2,4-

D, glyphosate, imazapyr, and triclopyr could be used for 

aquatic as well as terrestrial vegetation management. 

The herbicides that create the most short-term risk to

non-target plant species, given that application scenarios 

follow SOPs, are those that are applied in a manner that

increases the likelihood for off-site transport (e.g., drift, 

surface runoff). The risk characterization process of the

ERA indicated that risk to typical and special status 

terrestrial plants is moderate under scenarios involving 

off-site drift of bromacil and chlorsulfuron and risk to

special status terrestrial plants is moderate to high under

scenarios involving off-site drift of diquat, diuron, and

sulfometuron methyl. Diuron poses a moderate risk to

aquatic plants under scenarios involving off-site drift

associated with applications at the maximum 

application rate. None of the herbicides pose risk to 

non-target plants under wind erosion scenarios. 

Impacts to non-target plants would be lessened for 

herbicides that selectively target the desired species 

type. However, some changes in species composition 

could occur in these communities despite lessened 

impacts to non-target species as a result of altered

competitive relationships. The lasting effects of 

treatments using non-selective herbicides would depend

on the species present in the seedbank to reestablish at

the site. In many cases, reseeding or replanting 

treatments would be necessary after an application of a 

non-selective herbicide to ensure the presence of native

species on the site following treatment. 

The ALS-inhibiting herbicides evaluated in this PEIS

are chlorsulfuron, imazapic, imazapyr, metsulfuron

methyl, and sulfometuron methyl. These herbicides are 

BLM Vegetation Treatments Using Herbicides 4-63 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

applied at low application rates, with only small

concentrations necessary to damage plants. The ERAs 

predicted some risks to non-target plants associated with

those herbicides; however, the risks were similar to the 

risks associated with the other evaluated herbicides. 

Nevertheless, because of the potency of these

herbicides, they may be most appropriate for use when

the target plant is the dominant cover species, or when 

there is a particularly aggressive invasive species that

has not successfully controlled by other methods 

(USDA Forest Service 2005). 

Other Herbicides Previously Approved

for Use on Public Lands 

Asulam, atrazine, fosamine, mefluidide, simazine, and

2,4-DP (also known as dichlorprop) are currently 

approved for use on public lands. However, the 

historical use of these herbicides by the BLM has been 

quite limited, with only fosamine used in the last 7 years 

(on less than 50 acres annually). Asulam is used in postemergent control of broadleaf weeds, perennial grasses, 

and nonflowering plants in forestry and rangeland areas 

and ROW (Information Ventures, Inc. 1995a). Atrazine 

provides selective weed control in conifer reforestation,

and on ROW, and energy, mineral, cultural, and 

recreation sites. It is toxic to many plants and should not

be used under windy conditions near desirable trees, 

shrubs, or plants (Information Ventures, Inc. 1995b). 

Fosamine is used to control brush and herbaceous 

plants. No acute effects to aquatic plants are expected 

from normal use of fosamine, but movement of 

fosamine from the treatment site due to drift or runoff 

can adversely affect non-target and non-target species 

(USEPA 1995d). Mefluidide is registered for forestry, 

rangeland, and ROW. Contact with non-target species 

may injure or kill susceptible plants (Information

Ventures, Inc. 1995c). Simazine is a selective herbicide 

that is used to control broadleaf and grass weeds in 

forestry, rangeland, and ROW uses. It is toxic to many

plants (Information Ventures, Inc. 1995d). 2,4-DP is

registered to control aquatic weeds in ditches and for a 

variety of upland uses. It is a broadleaf herbicide 

(Pesticide Management Educator Program 2001). 

Impacts by Alternative 

The overall goal of treating vegetation would be to

restore natural fire regimes and to reduce or eliminate 

populations of undesirable vegetation. Treatments

aimed at achieving these goals should result in a more

desirable successional stage in forest and rangeland 

habitats, increase plant species diversity, and create a 

more stratified age structure for wildlife.

Species diversity and vegetative structural components 

would be enhanced under most treatments, although 

some treatments could be designed to reduce the size or 

density of stands of trees or shrubs. Herbicides would 

provide better control of resprouting vegetation than 

other treatment methods, particularly when applied 

before burning. Herbicides would be used on rangelands 

dominated by annual grasses, such as downy brome and

medusahead, followed by revegetation with perennial

grasses and forbs. Herbicides would also be used to 

suppress or thin shrubs in favor of herbaceous 

vegetation. In some areas, herbicide treatments might

reduce the cover of perennial grasses and forbs over the 

short term, but perennial grass and forbs communities 

should improve over the long term as shrub stands are 

thinned to allow more light and nutrients to reach the 

understory and competition for annual grasses and forbs 

is reduced. 

The following sections detail the expected effects of

each of the five alternatives on target and non-target

plant communities, and provide comparisons of effects 

among alternatives. These effects may vary depending

on the acreage treated using different application 

methods and different herbicides, as well as the size of 

treatment events. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue current vegetation treatment programs in 14

western states, and would treat an estimated 305,000

acres per year using both ground-based and aerial 

methods. Public lands in Alaska, Nebraska, and Texas 

would not be eligible for herbicide treatments under this 

alternative. 

Under this alternative, the BLM would be able to use 

the 20 herbicides previously approved in earlier EIS 

RODs. However, based on the recent pattern of BLM 

herbicide use, it is likely that approximately 75% of the

area treated would involve the use of only four 

herbicides: 2,4-D, glyphosate, picloram, and tebuthiuron

(see Table 2-5). 

As the No Action Alternative would be a continuation

of current vegetation treatment practices, impacts to 

vegetation would be similar in nature to those that have

occurred in the past. As a result, invasive species would

likely continue their rapid expansion across western

BLM Vegetation Treatments Using Herbicides 4-64 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

landscapes. Negative impacts to vegetation (i.e., harm to

non-target plants) could be lower than under the other 

herbicide-use alternatives based on the number of acres 

treated. However, long-term benefits to plant 

communities (i.e., eradication of unwanted vegetation 

and resulting improvements in ecosystems) would be 

much less under this alternative than the other 

alternatives. Invasive plant populations would likely 

continue to expand at the current rate or more quickly, 

increasing damage to native plant communities and

inhibiting ecosystem functions. 

Because the new herbicides proposed for use by the

BLM (diquat, fluridone, imazapic, and Overdrive®) 

would not be used under this alternative, risks to 

vegetation would be different than under the other 

alternatives. The risks to terrestrial plants associated

with exposure to these four herbicides (especially

imazapic) under accidental direct spray, spill, and offsite drift scenarios are lower than those associated with

exposure to bromacil and chlorsulfuron, and similar to 

or lower than the risks associated with exposure to the

other pre-approved herbicides. Imazapic has been

reported to successfully control the spread of aggressive 

invasives, including downy brome, Russian knapweed, 

and perennial pepperweed, and has had positive effects 

on native prairie restoration (Whitson 2001, Shinn and

Thill 2002). In addition, risks to aquatic plants 

associated with use of the new herbicides are similar to

or lower than those associated with use of the preapproved herbicides (e.g., bromacil, diuron), under all

application scenarios. Since the BLM would not use the 

new herbicides under the No Action Alternative, risks to

terrestrial plants from accidents and off-site drift during 

each application event could be greater than under the

other herbicide-use alternatives in situations where less

harmful new herbicides would otherwise be appropriate. 

However, risks to special status terrestrial plants from 

surface runoff would be greatest with the use of 

diflufenzopyr, suggesting that per treatment risks to

these species under surface runoff scenarios might be 

less under this alternative than under the other 

herbicide-use alternatives. 

Over half the treatments occurring under the No Action

Alternative would be in the Temperate Desert

Ecoregion, with a third of the treatments targeted to

improve sagebrush and other evergreen shrublands, and

a third targeted at annual and perennial invasive grasses 

and forbs (Table 4-15). The focus of most treatments in

this ecoregion is to improve habitat for sage-grouse and

other wildlife that use sagebrush communities by

improving the structural diversity and species 

composition of sagebrush and rabbitbrush stands, 

removing invasive species, and promoting production of 

perennial grasses and forbs desired by sage-grouse and 

other wildlife (Paige and Ritter 1999). Picloram may be 

active in the soil for an extended period of time after 

application and is potentially more damaging to

perennial grasses than 2,4-D. Application of picloram to

control rabbitbrush and forbs in this ecoregion should

decrease production of some desirable shrubs, forbs, 

and grasses, although grass production should recover 

as picloram dissipates (USDI BLM 1991a). 

Glyphosate could be used to spot treat unwanted annual

grasses and forbs. It is effective on downy brome, but is 

non-selective and can harm desirable plant species if not

used carefully. Tebuthiuron is a broad-spectrum 

herbicide that has a long period of activity in the soil

and is effective at thinning sagebrush. However, 

tebuthiuron may damage grasses and other desirable 

plants. Application of tebuthiuron at high rates has been

shown to decrease perennial grasses and allow annual

grasses, as well as rabbitbrush, to increase.

Forty percent of herbicide treatments would occur in the 

Subtropical Steppe, Temperate Steppe, and Subtropical

Desert ecoregions. Within these regions, over half the 

treatments would be targeted at evergreen shrublands. 

As in the Temperate Desert Ecoregion, treatments 

would focus on management of sagebrush/rabbitbrush

and control of annual and perennial invasive forbs and 

grasses. 

Over three-quarters of the treatments in the Subtropical

Steppe Ecoregion would be focused on sagebrush and

other evergreen shrublands, while 12% of the treatments 

in this ecoregion would focus on pinyon, juniper and 

other evergreen woodland species. Picloram and

tebuthiuron are the main herbicides used to treat 

pinyon-juniper woodlands. Both picloram and

tebuthiuron may persist in the soil for several years and

may injure understory grasses, shrubs, and forbs. 

Treating individual trees with these herbicides is often a

more effective means of controlling trees and less 

injurious to understory species than broadcast 

applications. Using picloram on some sites can also 

result in dominance by annual grasses, such as downy 

brome or medusahead, if these species become resistant

to picloram (USDI BLM 1991a). 

Over three-quarters of the treatments in the Temperate

Steppe Ecoregion would be focused on annual and 

perennial grasses and forbs, including downy brome, 

knapweeds, and thistles. Control of broadleaf plants 

using selective herbicides, such as 2,4-D, usually 

BLM Vegetation Treatments Using Herbicides 4-65 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

increases grass production. 2,4-D is also effective in

controlling weedy forbs, such as bull, musk, and Scotch

thistle. 2,4-D can be tank mixed with other herbicides, 

such as glyphosate, dicamba, picloram, and triclopyr to 

enhance the activity of these herbicides. Applications of 

selective herbicides, such as 2,4-D, are expected to 

increase grasses and decrease broadleaf species.

Applications of picloram may damage sensitive grasses 

as well as broadleaf plants, and can substantially alter 

the composition of grassland communities (USDI BLM

1991a). 

Under this alternative, over 70% of acres would be 

treated in the Temperate Desert Ecoregion, a much

greater proportion than would be treated under the No

Action or other alternatives (Table 4-16). Fifteen

percent of treatments would occur in the Temperate 

Steppe Ecoregion. As under the No Action Alternative, 

treatments in the Temperate Desert Ecoregion would be 

targeted primarily toward sagebrush, rabbitbrush, and

other evergreen shrubland species, and annual grass and

perennial forb weeds, while those in the Temperate

Steppe Ecoregion would focus on control of invasive 

annual and perennial grasses and forbs. 

Herbicides such as picloram and tebuthiuron are used to

control woody species such as mesquite, creosotebush, 

and snakeweed in Subtropical Desert habitats. These 

herbicides usually decrease woody plant growth and

increase growth of grasses, although it may take several 

years before grass and forb production increases in 

response to reduced competition from shrubs. Picloram 

is effective in controlling snakeweed, while tebuthiuron 

is effective in controlling creosotebush and tarbrush. 

However, tebuthiuron can be injurious to many grasses 

and forbs, and may promote the development of annual

forbs, including Russian thistle. Dicamba has been used 

to control undesirable herbaceous and woody species 

and has minimal impact on grasses if applied at normal

application rates (0.5 to 1 lb a.i./acre; USDI BLM

1991a). 

This alternative would result in the most extensive 

impacts to vegetation (both negative and positive) 

because it proposes the most acres for treatment (3

times the acreage proposed under the No Action

Alternative). The use of the four new herbicides and the 

ability to use future herbicides that become registered

with the USEPA would allow BLM managers more 

options in choosing herbicides to best match treatment 

goals and application conditions, and might therefore 

reduce overall risk to vegetation and increase positive

ecosystem benefits from treatment. In addition, the

ability to use future registered herbicides would allow 

the BLM to employ the most technologically-advanced

herbicides, which would likely reduce risk to non-target 

plants and increase management benefits. This 

alternative would also reduce risks and negative impacts 

associated with other vegetation management methods 

(e.g., risk of escaped prescribed fires; see the PER).

Furthermore, it is useful to have a range of herbicides 

and herbicide types available for use to combat diverse 

weed problems, and to minimize the chance that

invasive species will become resistant to herbicides that 

are sprayed in the same location for several years. Weed 

resistance to herbicides can be minimized by using

multiple herbicides with different sites of action in the

same application, alternating herbicides with different 

sites of action each year, or alternating herbicide use

with other effective forms of treatment (e.g., prescribed

fire, mechanical removal). 

Under this alternative, the BLM would be able to 

continue to use 2,4-DP, asulam, atrazine, fosamine, 

mefluidide, and simazine, although it is unlikely that 

these herbicides would be used. In recent years, the

BLM has used other herbicides in their place that are 

more effective or have fewer environmental and/or 

human health risks. Bromacil, dicamba, and glyphosate 

have been substituted for asulam; bromacil, diuron, 

sulfometuron methyl, and tebuthiuron have replaced 

atrazine; triclopyr has replaced fosamine; sulfometuron

methyl has replaced mefluidide (and imazapic would 

also replace mefluidide); diuron and hexazinone have 

replaced simazine; and 2,4-D, dicamba, imazapyr, and 

triclopyr have replaced 2,4-DP. 

Based on BLM patterns of use, 2,4-D, glyphosate, 

picloram, and tebuthiuron would comprise about 70%

of the herbicides that would be used under this

alternative (see Table 2-5). The risks and benefits of 

using these herbicides are discussed under the No

Action Alternative. Approximately 10% of all treatment

acres would be treated with the new herbicides, and of 

these, over three-fourths of these acres would be treated 

using imazapic. Imazapic could be used in all areas 

except riparian and wetland areas. Imazapic would be

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Alternative B, the Preferred Alternative, would result in 

the treatment of approximately 932,000 acres across the 

17 western BLM states. In addition to the 14 currentlyapproved herbicides, the BLM would be able to use the 

four others evaluated in this PEIS. 

BLM Vegetation Treatments Using Herbicides 4-66 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

TABLE 4-15 

Percentage of Acres Projected to be Treated Using Herbicides in Each Ecoregion for 

Each Vegetation Subclass under the No Action Alternative 

Ecoregion 

Vegetation Subclass1

Tundra Subarctic Marine Mediterranea

n

Subtropical Desert Subtropical Steppe Temperate Desert Temperate Steppe 

Evergreen forest 0 0 86 74 0 <1 3 1

Deciduous forest 0 0 0 0 0 0 3 0

Mixed evergreen/deciduous forest 0 0 0 0 0 0 0 0

Evergreen woodland 0 0 0 1 3 12 5 2

Deciduous woodland 0 0 0 <1 7 4 0 0

Mixed evergreen/deciduous 

woodland 0 0 0 0 0 0 0 0

Evergreen shrubland 0 0 0 6 88 77 30 6

Deciduous shrubland 0 0 0 0 0 3 <1 0

Evergreen dwarf-shrubland 0 0 0 0 0 0 0 0

Deciduous dwarf-shrubland 0 0 0 0 0 0 0 0

Perennial graminoid 0 0 14 <1 0 1 9 22

Annual graminoid or forb 0 0 0 16 0 <1 21 3 

Perennial forb 0 0 0 1 <1 1 14 29

Riparian/wetland 0 0 0 2 <1 1 1 0

More than one subclass 0 0 0 0 2 1 14 38 

Total for all ecoregions 0 0 1 3 15 17 51 13 1 See Table 3-4 and Vegetation section in Chapter 3 for a description of vegetation subclasses. 

used to control downy brome, hoary cress, perennial

pepperweed, and several other invasive species that are 

known to displace native vegetation and alter wildfire 

intensity and frequency. 

About 2% of all treatment acres would be treated using 

Overdrive®. Overdrive® would be used on rangelands, 

ROW, oil, gas, and mineral sites, and cultural and 

recreation sites. This herbicide is not effective at

controlling downy brome, but does have activity on oak 

species that may be controlled to reduce hazardous 

fuels. It also provides activity on several annual 

broadleaf species including burningbush, pigweed, and 

Russian thistle; several biennial species including bull,

musk, and Scotch thistle, teasel, and diffuse knapweed; 

and several perennial species including spotted and

Russian knapweed and field bindweed. The herbicide is

also effective in controlling poisonous plants, such as 

whorled milkweed. 

In addition to being able to use four new herbicides 

under this alternative, the BLM would be able to use 

herbicides in Alaska, Nebraska, and Texas. Although no 

herbicide treatments are planned on public lands in 

Alaska under this alternative, the ability to use

herbicides in Nebraska and Texas would allow for more 

comprehensive weed management programs in these 

states. 

Alternative C – No Use of Herbicides 

Under Alternative C, non-target plants would not be 

affected by herbicide use. Effects to vegetation would 

stem from other vegetation treatment methods (see the 

accompanying PER). In general, the potential negative

impacts to non-target plants from manual and

mechanical treatment methods are expected to be lower 

than those from chemical and prescribed fire methods 

(the impacts from biological methods are less certain). 

Positive ecosystem benefits as a result of vegetation 

management may be less than under the Preferred

Alternative, as there are certain invasive species for 

which herbicide use is the only effective method of 

treatment or for which treatment by other methods is

impractical due to cost, time, accessibility, or public

concerns (e.g., saltcedar in riparian areas). For example,

BLM Vegetation Treatments Using Herbicides 4-67 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

rough terrain may prevent treatment by methods that

require ground vehicle and foot access, while aerial 

treatment with herbicides would be possible in these 

areas. Vegetation treatments on ROW and oil and gas 

production facilities would have to be done by manual

and mechanical means, or not done at all. Both options

may be unfeasible for ROW, while the latter option 

would compromise the safety of oil and gas production

facilities (USDI BLM 1991a). 

In addition, it is often difficult to eradicate some

species, such as shrubs that resprout from roots, by 

means other than herbicide application (e.g., 

rabbitbrush, honey mesquite, Harvard oak, tree cholla). 

Similarly, pre-emergent herbicides that persist in the

soil are the most effective means of controlling invasive

plants with seeds that remain viable for long periods of

time. Furthermore, where prescribed fire is an 

appropriate alternative to larger-scale herbicide use 

(such as in rangelands), neighboring communities may 

object to the resulting smoke production or risk from 

escaped fires. 

Under this alternative, without the use of herbicides, 

fewer total acres would be treated annually, and in some

areas invasive plant populations would spread at a faster 

rate, than under the other alternatives, particularly

where other treatment methods are not effective or 

possible (e.g., steep, rocky terrain, and large tracts of

rangeland or grassland dominated by invasive, 

resprouting shrubs or without enough fine fuels to carry

prescribed fires). In these areas, degradation of native

plant communities would be greater than under the

other alternatives. 

Alternative D – No Aerial Applications 

Alternative D would allow the use of the same

herbicides in the same areas as allowed under the

Preferred Alternative, and the benefits associated with 

availability of new and future herbicides would be the

same for both alternatives. However, Alternative D 

would prohibit aerial herbicide applications. The total

treatment acreage would be reduced to approximately

530,000 acres, because some large and remote areas 

cannot be effectively treated by ground application

methods. This alternative would result in substantially 

fewer impacts to non-target vegetation from off-site 

drift as compared to alternatives where aerial spraying 

would be allowed. Drift is a major route of unintended

damage to plants, and aerial application is a primary 

cause of off-site drift. Impacts per treatment would also

be much lower under this alternative than under 

alternatives A and B, and would be similar to or less

than per area impacts under Alternative E. 

Under this alternative, it is likely that long-term

negative effects on desired plant communities and 

ecosystems would be greater than any potential shortterm negative effects that would result from aerial

applications under other alternatives. In addition, direct 

and indirect impacts from other vegetation treatment

options might increase if these methods were used more 

extensively to compensate for the reduced number of

acres treated by herbicides. These impacts could include

greater vegetation damage from the use of ground-based 

equipment than under the other alternatives. 

Prescribed fire and mechanical treatment would be

substituted for aerial herbicide treatments as much as 

possible in large areas proposed for treatment. Fire

would not be effective in areas with insufficient fuels to

carry fire, while mechanical treatments might not be 

suitable in areas where sprouting species, such as 

rabbitbrush, might increase after mechanical treatment.

This alternative would preclude treatment of large 

expanses of downy brome and other invasive annual 

grasses using imazapic and other herbicides. Fire could

also result in substantial damage to sagebrush stands 

and enhance the development and spread of downy 

brome and other annual grasses, while mechanical 

disturbance could also lead to conditions that enhance 

the spread of weeds and other invasive plants (USDI 

BLM 1991a). 

Nearly all (91%) aerial treatments are proposed for the 

Subtropical Steppe and Temperate Desert ecoregions. 

Of these, two-thirds would occur in evergreen 

shrublands to remove invasive vegetation, such as 

downy brome. The remaining treatments would focus 

primarily on control of undesirable annual and perennial

grasses and forbs. Controlling sprouting woody species 

in areas where an herbaceous community is desired

could be difficult because herbicide use would be

limited and sprouting might be enhanced by burning

and mechanical methods. Under this alternative, more 

acres in these ecoregions would continue to be 

dominated by shrubs, and the herbaceous component of 

plant communities would not be as diverse or 

productive as in communities where aerial applications 

of herbicides were used. 

About 7% of aerial treatments would occur in the 

Temperate Steppe Ecoregion, with most of these

treatments used to control perennial forbs such as 

knapweed, thistles, and leafy spurge. Prescribed fire

could be used to treat large acreages, but control of

BLM Vegetation Treatments Using Herbicides 4-68 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

TABLE 4-16 

Percentage of Acres Projected to be Treated Using Herbicides in Each Ecoregion for 

Each Vegetation Subclass under the Preferred Alternative 

Ecoregion 

Vegetation Subclass1

Tundra Subarctic Marine Mediterranea

n

Subtropical Desert Subtropical Steppe Temperate Desert Temperate Steppe 

Evergreen forest 0 0 79 76 0 <1 1 1

Deciduous forest 0 0 0 0 0 0 <1 <1

Mixed evergreen/deciduous forest 0 0 0 0 0 0 0 <1 

Evergreen woodland 0 0 0 6 0 1 2 <1

Deciduous woodland 0 0 0 <1 5 5 0 0

Mixed evergreen/deciduous woodland 0 0 0 0 0 0 0 0

Evergreen shrubland 0 0 0 8 26 42 36 21

Deciduous shrubland 0 0 0 0 32 4 <1 0

Evergreen dwarf-shrubland 0 0 0 0 0 0 0 0

Deciduous dwarf-shrubland 0 0 0 0 0 0 0 0

Perennial graminoid 0 0 21 <1 0 33 8 26

Annual graminoid or forb 0 0 0 10 0 8 20 2 

Perennial forb 0 0 0 <1 <1 1 12 23 

Riparian/wetland 0 0 0 <1 2 4 1 0

More than one subclass 0 0 0 0 34 3 21 26 

Total for all ecoregions 0 0 <1 4 <1 9 71 16 1 See Table 3-4 and Vegetation section in Chapter 3 for a description of vegetation subclasses. 

noxious weeds and other broadleaf species in this

ecoregion would not be as effective as under the 

Preferred Alternative. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Alternative E was developed based on a proposal for 

ecosystem-based vegetation management submitted by

the American Lands Alliance, an alliance of several

environmental and conservation groups (see Appendix 

I). Approximately 466,000 acres would be treated under 

Alternative E, which is slightly less than the acreage

that would be treated under Alternative D and less than 

half of the acreage that would be treated under the 

Preferred Alternative. However, there would still be an

increase from the average annual treatment acreage over 

the past 8 years (and likely to occur under the No 

Action Alternative). In addition to a relatively low 

impact to vegetation as a result of the low number of 

treatment acreage, per treatment impacts under 

Alternative E would also be lower than under the other 

herbicide-use alternatives because of the restrictions 

detailed by this alternative—most notably prohibition of

the use of ALS-inhibiting active ingredients. 

Sulfonylurea herbicides and other ALS-inhibiting 

herbicides (e.g., chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, sulfometuron methyl) block the 

synthesis of amino acids that are required for protein

production and cell growth; thereby resulting in plant

death. These herbicides are biologically active at small

concentrations, which is beneficial to herbicide 

applicators because a small dose may be used, thereby

saving money and possibly resulting in fewer cases of

unintended damage to wildlife and the environment

(e.g., groundwater contamination [Obrigawitch et al. 

1998]). However, because of their high potency, these

chemicals may pose excessive dangers to non-target 

plants. Off-site movement of even small concentrations 

of these herbicides can result in extensive damage to

surrounding plants, and damage to non-target plants 

may result at concentrations lower than those reportedly 

required to kill target invasive species (Fletcher et al. 

1996), including concentrations that cannot be detected 

by any standard chemical protocol (Whitcomb 1999). 

One study reported that drift of chlorsulfuron caused

BLM Vegetation Treatments Using Herbicides 4-69 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

82% to 100% reductions in the yield of several crop

species when it was applied at 0.008 to 0.004 times the 

label-suggested application rate (such as might occur 

with off-site drift) at critical stages of plant development

(Fletcher et al. 1996). However, another study reported

that risks to non-target plants associated with 

sulfonylurea herbicides are similar to those associated 

with other herbicides used at higher application rates 

(Obrigawitch et al. 1998). In addition, a predominant

problem with ALS-inhibiting herbicides is that they can

quickly confer resistance to weed populations,

particularly since they are often used extensively as the 

primary weed control method and they have a single 

mode of action and long residual activity, allowing

ample opportunity for the ALS-encoding gene in the 

target weed to mutate—resulting in a resistant version

of ALS (Whitcomb 1999, Tranel and Wright 2002). 

Sulfometuron methyl has been implicated in several 

cases of large-scale damage to non-target species as a 

result of off-site drift. In Franklin County, Washington, 

drift of sulfometuron methyl (as the active ingredient in 

the herbicide Oust®) caused over a million dollars in

damage to more than 700 miles of roadside, including

300,000 young trees in one nursery (Turner 1987). 

Damage to croplands occurred in Idaho when public 

lands damaged by wildfire were treated with Oust®

 and 

treated soils drifted off-site in wind-blown soil. 

Responses by agencies to these types of findings varies 

from warnings about applying these herbicides during 

critical reproductive periods of non-target plants or 

during likely drift conditions to suggestions that the use

of these herbicides should be severely limited or 

discontinued, or that the practice of aerial spraying

should be abandoned. Because of the risks associated

with off-site drift, the labeled use of sulfometuron

methyl for burned areas has been rescinded by the 

USEPA, although the herbicide can still be used on

noncrop and forestry sites per label directions. 

Under this alternative, the BLM would not be able to 

use chlorsulfuron, imazapic, imazapyr, metsulfuron

methyl, or sulfometuron methyl. However, other 

herbicides proposed for use by the BLM pose risks that

are similar to those associated with these five 

herbicides; therefore, it is uncertain whether this use 

restriction would actually reduce risk to non-target 

plants. 

This restriction could ameliorate some of the public 

concern associated with herbicide use on public lands. 

However, the potency of these herbicides allows them

to be used in very small amounts, which could limit

their exposure to off-site species via runoff or drift. In

addition, these herbicides may be most effective on 

particularly aggressive invasive species that have not

responded to other herbicides or treatment methods. 

Control of these aggressive species may not be possible 

under Alternative E. Furthermore, as mentioned in the 

No Action Alternative, it is useful to have a range of 

herbicides and herbicide types available for use to 

combat diverse weed problems, and to minimize the 

chance that invasive species will become resistant to

herbicides that are sprayed in the same location for 

several years. 

Alternative E incorporates other management practices 

that would be likely to have positive impacts on

vegetation communities. The suggested use of 500-foot

buffers between broadcast herbicide applications and 

special status plants would reduce risks to sensitive

plants from off-site drift and surface runoff. However, 

herbicide damage from off-site drift has been noted up

to a mile from application, and the ERA predicted risks 

to special status terrestrial plants from application of

bromacil and diuron at distances up to 900 feet.

Alternative E would limit the use of broadcast

applications, which would reduce the risks to non-target 

plants associated with off-site drift. Broadcast 

applications could be used in appropriate situations (i.e., 

where no other method is practical and non-target plant 

species and aquatic areas are distant from the

application area), however, which would result in some

ecosystem benefits from larger scale herbicide 

applications. Herbicides would not be used in riparian

conservation areas, which would protect sensitive 

aquatic plant species and attendant ecosystem 

functions in these key areas. However, if these areas 

were to become degraded by invasive species, it could

be more difficult to control and eradicate these species 

using non-herbicide methods, which would imperil

native plants and important riparian ecosystem 

functions in these and adjoining areas. 

While per treatment ecosystem benefits could be greater 

under Alternative E than under the other herbicide-use 

alternatives as a result of this ecosystem-based 

management approach, overall benefits to vegetation

and ecosystems across the 17 western states (that could 

not be attained using other treatment methods) would be 

lower under this alternative because of the relatively

low treatment acreage and the inability to use certain

practices in situations where they are warranted (e.g.,

use of ALS-inhibitor herbicides on highly aggressive 

weeds). 

BLM Vegetation Treatments Using Herbicides 4-70 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Mitigation for Herbicide Treatment 

Impacts 

In addition to the SOPs identified earlier in this section 

and in Table 2-8, the following measures are 

recommended to reduce impacts to non-target 

vegetation from the use of herbicides: 

• Minimize the use of terrestrial herbicides

(especially bromacil, diuron, and 

sulfometuron methyl) in watersheds with 

downgradient ponds and streams if potential 

impacts to aquatic plants are of concern. 

• Establish appropriate (herbicide specific) 

buffer zones around downstream water bodies, 

habitats, and species/populations of interest

(see Tables 4-12 and 4-14). Consult the ERAs 

for more specific information on appropriate 

buffer distances under different soil, moisture, 

vegetation, and application scenarios. 

• Limit aerial application of chlorsulfuron, 

metsulfuron methyl, and sulfometuron methyl

to areas with difficult land access, where no 

other means of application is possible. 

Special Status Plant Species 

Introduction

As discussed in Chapter 3, public lands in the western 

U.S. support over 1,000 plant species that have been 

given a special status based on their rarity or sensitivity. 

Special status plants include approximately 150 species 

that are federally listed as threatened or endangered, or 

are proposed for federal listing. The remaining special 

status species include candidates for federal listing, and 

other species that warrant special attention and could 

potentially require federal listing in the future. Many of 

these species are threatened by competition with nonnative plants and other invasive species. The Vegetation 

Treatments on Bureau of Land Management Lands in 

17 Western States Programmatic Biological Assessment

(USDI BLM 2007b) provides a description of the 

distribution, life history, and current threats for each 

federally-listed plant species, as well as species 

proposed for listing. The BA also discusses the risks to 

threatened and endangered species, and species 

proposed for listing (collectively referred to as TEP 

plants) associated with each of the herbicides proposed 

for use by the BLM under the different alternatives. 

Impacts Assessment Methodology 

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM and Forest Service to 

assess the impacts to sensitive plant species from the

use of herbicides (ENSR 2005b-k; SERA 2005a). The 

ERA methods are summarized earlier in the Vegetation

section of this chapter. Methods used by the BLM are 

presented in detail in the Vegetation Treatments 

Programmatic EIS Ecological Risk Assessment

Protocol (ENSR 2004) and in Appendix C; methods 

used by the Forest Service can be viewed on the Internet 

at http://www.fs.fed.us/r6/invasiveplant-eis/. 

Although BLM ERAs used the same LOC for all nontarget plant species, separate plant toxicity endpoints 

were selected to provide extra protection to special 

status plant species (see Table 4-11). Thus, ERAs for 

some herbicides predicted higher risks for special status 

plant species than for “typical” plant species under 

certain exposure scenarios. Risk assessments completed

by the Forest Service also used different toxicity

endpoints for sensitive and tolerant plant species. Risks

to special status plant species were determined by 

comparing the HQs for sensitive plant species 

developed by the Forest Service with the same LOC 

that was used to determine risks to plants in the BLM 

ERAs (see Table 4-13). 

Herbicide use does pose potential risks to sensitive plant 

species. However, these risks can be minimized by 

following certain SOPs, which can be implemented at

the local level according to specific conditions (see

Table 2-8). These SOPs include: 

• Survey for special status plant species before

treating an area. Consider effects to special 

status species when designing herbicide 

treatment programs. 

• Use drift reduction agents to reduce the risk of 

drift hazard. 

• Use a selective herbicide and a wick or 

backpack sprayer to minimize risks to special

plants. 

Summary of Herbicide Impacts 

Many special status plant species are threatened by the 

spread of non-native plants. Although a discussion of 

individual plant species is beyond the scope of this 

PEIS, the BA provides additional information on which 

TEP plant species are most at risk from competition 

with non-native plants. Invasive species are expected to 

BLM Vegetation Treatments Using Herbicides 4-71 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

continue to spread into habitats occupied by special 

status species, potentially encroaching on populations

and resulting in reductions in population size and vigor,

and even extirpation, in some cases. Furthermore,

species with very small populations are also at risk of 

extirpation as a result of fire, even in habitats that are

adapted to fire. 

Fuels reduction and control of competing vegetation are

important components of management programs for

special status plant species. However, the sensitivity of

these species requires special care during management

to ensure that the management actions themselves do

not harm or endanger populations. In the case of special 

status plant species, manual spot applications of 

herbicides may be the only suitable means of applying 

herbicides that can adequately ensure the protection of 

sensitive populations. In the case of special status plant 

species that are not federally listed or proposed for 

listing, the impacts associated with herbicide use would

be a factor of the herbicide’s ability to control nonnative plants that threaten the species’ habitat over the 

long term, and the extent of short-term harm that the 

herbicide would cause the species. For species with 

populations that are declining but secure, some

mortality or a reduction in population size over the short

term could be acceptable, provided the overall habitat

for the species was improved, and provided herbicides 

did not remain in the soil and continue to impact growth

and regeneration over the long term. In addition, 

treatment of weeds in areas that are close to sites that 

currently support special status species may improve 

habitat to such a degree that the rarer species are 

allowed to spread into portions of their original range 

that are no longer suitable for supporting them. 

In some cases, special status plants are present because 

the site is pristine or relatively undisturbed. Herbicide 

use would not be required in these places. Similarly,

most of the areas where aggressive herbicide treatments 

would take place (such as oil and gas ROW, heavily 

grazed rangelands) are unlikely (though not unknown) 

to support extensive populations of special status 

species. 

All of the herbicides analyzed in ERAs would pose risks 

to terrestrial special status plant species in a situation 

where plants were directly sprayed, at either typical or

maximum application rates, during a treatment. 

Herbicides with the greatest likelihood of harming

special status plants (i.e., those that pose a high risk

when applied at the typical application rate) include

bromacil, chlorsulfuron, clopyralid, diflufenzopyr, 

diquat, imazapyr, metsulfuron methyl, Overdrive®, 

picloram, sulfometuron methyl, and triclopyr. These 

herbicides would also present the most risk to terrestrial

special status plant species as a result of drift from a

nearby application site. The herbicide with the lowest 

risk to terrestrial plants is imazapic, which, according to 

ERAs, can be broadcast sprayed by ground methods 25 

feet from a sensitive plant without risk. 

The likelihood of adverse effects to special status 

terrestrial plants as a result of surface runoff from an

upslope treatment site is dependent both on the 

herbicide used and the site conditions. Certain sites, 

such as those with clay soils that experience high annual

rainfall, are more susceptible to surface runoff of

rainwater. The timing of the herbicide application prior 

to a major rain event and the persistence of the herbicide 

on the site are also factors. Based on information from

the ERAs, herbicides with the greatest likelihood of 

affecting special status plant species via surface runoff 

include imazapyr, metsulfuron methyl, picloram, and 

triclopyr. Of these herbicides, picloram has the longest

soil half-life (see Soil Resources section). Herbicides 

with the least likelihood of impacting special status 

terrestrial plant species include imazapic, chlorsulfuron,

and glyphosate, which pose no risk to sensitive plants 

via surface runoff, and bromacil, which poses low risks 

to sensitive plants only under a narrow range of site 

conditions. 

The vast majority of the BLM’s special status plant

species are terrestrial. However, there are also aquatic 

plant species (including species in wetland habitats) for 

which separate risk analyses were completed. Aquatic 

plants could be harmed by a normal application of an 

aquatic herbicide, accidental direct spray or spray drift

of a terrestrial herbicide from a nearby upland, 

accidental spill, or surface runoff from an upslope area

into the water body where the plant is located. Use of 

2,4-D and diquat to control vegetation in aquatic

habitats would pose the greatest risks to any special

status plant species also in the habitat. Aquatic

herbicides that would be safe for use in aquatic habitats 

where special status plant species occur include 

fluridone and aquatic formulations of glyphosate. In

addition, triclopyr acid could be applied directly to the 

water column at the standard concentration without

harm to sensitive aquatic plants. 

The terrestrial herbicides that would pose the greatest 

risks to special status aquatic plants as a result of

accidental direct spray, spray drift, or surface runoff 

include 2,4-D (assumed), bromacil, diquat, diuron,

hexazinone (assumed), and sulfometuron methyl. An

accidental spill of most terrestrial herbicides would pose

BLM Vegetation Treatments Using Herbicides 4-72 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

quite a high risk to special status plants. Notable

exceptions would be picloram, with no risk, and

diflufenzopyr with low risks. Based on the results of

risk assessments, the safest terrestrial herbicides to use

near aquatic habitats would be picloram and 

diflufenzopyr. 

Additional indirect effects to certain special status plant

species could occur if populations of pollinators were 

harmed by herbicide spraying. However, according to 

risk assessments risks to pollinators would be less than 

those associated with direct spray of the rare plants

themselves. Management efforts to protect rare plants

would also help prevent harm to insects in the vicinity. 

These management efforts include: 

• Designating buffer zones around rare plants. 

• Managing herbicide drift especially to nearby

blooming plants. 

• Using typical rather than maximum rates of 

herbicides in areas with rare plants. 

• Choosing herbicide formulations that are not

easily carried by social insects to hives, hills, 

nests and other ”homes” in areas with rare

plants. 

• Choosing herbicides that degrade quickly in the 

environment when herbicides must be used in 

rare plant habitat. 

• Timing the herbicide applications when

pollinators are least active, such as in the 

evenings or after blooming has occurred for the 

day in rare plant habitat, and if necessary 

dividing the rare plant habitat into several

treatments rather than one large treatment to 

keep from treating all blooming species at one 

time. 

Effects to pollinators would be short-term, and

population-level effects are not anticipated when these 

types of management practices are incorporated into 

project design when rare plants are present. 

Alternative A – Continue Present Herbicide Use 

(No Action Alternative) 

Under this alternative, approximately 305,000 acres of 

public lands would be treated with herbicides annually. 

Based solely on acres treated, special status plant 

species would be less likely to be exposed to herbicides 

under this alternative than under the other herbicide-use 

alternatives. Therefore, less harm to special status plants 

and plant populations from herbicide exposure should 

occur. For special status plant species, risks for impacts 

from herbicide exposure should not be substantially 

different under all the action alternatives, since the 

BLM would design herbicide treatments to avoid risks 

to these species (which would include the use of 

protective spray buffers and other mitigation measures 

identified in the BA). Nonetheless, the likelihood of an 

accidental exposure would be lower under the No 

Action Alternative, since less herbicide would be 

sprayed on public lands annually. 

Because fewer acres would be treated with herbicides 

than under the other herbicide-use alternatives, less 

fuels reduction (i.e., through control of downy brome) 

and control of non-native species using herbicides 

would occur under the No Action Alternative. Although 

most fuels reduction is done using other treatment 

methods, it is expected that the risk of a fire damaging

populations of special status species would be higher

than under the other alternatives, since there likely 

would likely be less total fuels reduction on public 

lands. Furthermore, since existing weed infestations 

would not be controlled as rigorously with herbicides, it

is expected that populations of non-native species would 

spread at a faster rate than under the other herbicide-use

alternatives. In some circumstances, populations of 

special status plant species that occur in the same

habitats as targeted weed species, and that are 

threatened by their spread, would be more likely to

decline as a result of competition with weeds under this 

alternative than under the other herbicide-use 

alternatives. 

Under this alternative, only those herbicides currently

used by the BLM would be used to treat vegetation.

Based on herbicide usage in the past decade, the

majority of the total acreage would be treated with

picloram, tebuthiuron, and 2,4-D. Risks to terrestrial

plants associated with picloram are relatively high.

Risks associated with tebuthiuron are low to moderate. 

Risks associated with 2,4-D are unknown, and given the 

lack of phytotoxicity information for this herbicide, 

assumed to be high. Risks to aquatic plants associated

with picloram are very low. Risks associated with 

tebuthiuron range from low to high. Risks associated

with 2,4-D are low to moderate. Therefore, risks to most

special status plants would likely vary from low to high

under this alternative, depending on the herbicide used. 

BLM Vegetation Treatments Using Herbicides 4-73 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Alternative B – Expand Herbicide Use and 

Allow for Use of New Herbi ides in 17 Western 

Sta es (Preferred Alternative) 

c

t

Under this alternative, approximately 932,000 acres of 

public lands would be treated with herbicides annually. 

Based solely on acres treated, special status plant 

species would be more likely to be exposed to 

herbicides under this alternative than under the other 

alternatives. Therefore, more harm to special status 

plants and plant populations from herbicide exposure 

would likely occur. In the case of special status plant 

species, the likelihood of an accidental exposure to 

herbicides would be greater than those under the other 

alternatives, since more acres would be treated, and 

more herbicide would be utilized. However, impacts to 

these species from herbicide exposure should not be 

substantially different than under the other alternatives, 

since the BLM would design herbicide treatments to 

avoid risks to these species (which would include the 

use of protective spray buffers and other mitigation 

measures identified in the BA). In addition, areas most 

in need of treatment, which would also receive the most 

intensive herbicide treatments, are not likely to support 

extensive populations of special status plant species. 

Because more acres would be treated with herbicides 

than under the other alternatives, more fuels reduction

and control of non-native species using herbicides 

would occur under the Preferred Alternative. Therefore, 

populations of special status species would be most

likely to benefit from herbicide treatments through 

habitat improvements under this alternative. It is 

expected that the extent and rate of spread of weeds 

would be lowest under this alternative, and that there 

would be less competition with populations of special

status plant species than under the other alternatives. 

Under the Preferred Alternative, the BLM would be 

able to use only 14 of the 20 herbicides that would be 

available under the No Action Alternative, but would 

also be able to use four new herbicides, and additional

new herbicides that become available for use in the

future. The two new terrestrial herbicides, imazapic and

diflufenzopyr, have low risks to sensitive terrestrial

plants under most conditions. Therefore, risks to special

status species could be reduced under this alternative, 

provided the BLM used these herbicides in place of 

herbicides with higher risks to sensitive plants, such as

picloram and 2,4-D. 

Of the two new aquatic herbicides, fluridone poses no 

risk to sensitive non-target plants during an application,

but there are moderate to high risks associated with

using diquat. Given that the risks associated with diquat

are higher than those associated with aquatic herbicides 

currently used by the BLM, impacts to aquatic special 

status plant species would likely be greater under the 

Preferred Alternative than under the No Action 

Alternative, especially if diquat was used in place of

other less toxic herbicides. 

Finally, the greater number of herbicides available for 

use and the flexibility of additional future options under 

the Preferred Alternative would potentially allow the

BLM to come up with treatment programs that are more

effective at reducing weed infestations, safer for

sensitive, non-target plants, and less likely to result in 

reduced effectiveness of herbicides from repeated use

than under the No Action alternative. 

Alternative C – No Use of Herbicides 

Under this alternative, no public lands would be treated

with herbicides. Therefore, special status species on

public lands would not be exposed to herbicides unless 

chemicals were transported onto the land from off-site. 

The risks to special status plant species for harm due to 

herbicide exposure would be near zero under this 

alternative, and therefore much lower than under the

other alternatives. However, impacts to these species 

from herbicide exposure should not be substantially 

different than under the other alternatives, since 

measures to protect these species would be 

implemented under the other alternatives. 

Under this alternative, the BLM would be less effective

at controlling weed infestation than under the other 

alternatives. Non-native plant species, including those 

that compete with, or are a threat to, special status plant

species, would spread at a faster rate than under the 

other alternatives. Although other treatment methods 

could be substituted for herbicide treatments, it is 

unlikely that these control measures would be as 

effective under all circumstances. Furthermore, some

treatments must be combined with herbicide treatments

to achieve the desired result (e.g., burning or 

mechanical treatments followed by spraying). These 

treatments would be used on their own under this 

alternative, and would not be as effective at controlling 

weed infestations. 

Under this alternative, special status plant species and 

their habitats would not benefit from manual spot

treatments of herbicides, which can be used to control 

weed infestations in areas that are too sensitive to 

receive more disturbing or wide-scale treatments. Under 

this alternative, the BLM would have fewer tools to

BLM Vegetation Treatments Using Herbicides 4-74 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

control weeds near populations of special status species, 

many of which are threatened by non-native species. 

Overall, less would be done to improve the habitat of 

these species, making them more at risk for future

population declines or extirpations. 

Alternative D – No Aerial Applications 

Under this alternative, approximately 530,000 acres 

would be treated with herbicides annually, fewer than 

under the Preferred Alternative, but more than under all

of the other alternatives. Based solely on acres treated,

special status plant species would be less likely to be

exposed to herbicides than under the Preferred

Alternative, but more likely to be exposed to herbicides 

than under the other alternatives. Accordingly, the 

second greatest amount of herbicide-related impacts to

special status plant populations would occur under this 

alternative. In the case of special status plant species,

impacts would be similar to those under the other

alternatives, since all herbicide treatments would be 

designed to avoid risks to these species. Risks for 

accidental exposure could be higher than under 

alternatives, A, C, and E. 

Plant species of concern would not be exposed to

herbicides directly from off-site drift associated with an

aerial application. Adverse effects to terrestrial and

aquatic special status plants could potentially occur by

ground applications at distances ranging from 25 to 

1,500 feet. 

The amount of fuels reduction and control of non-native 

species, and the related benefits to special status species 

from habitat improvement would also be second highest

under this alternative. Because aerial spraying would

not occur under this alternative, the BLM would be

unable to treat areas that are inaccessible by ground 

methods. In these areas, weed infestations would persist

and likely spread, potentially impacting nearby 

populations of special status plant species. 

Under this alternative, the herbicides available for use

by the BLM would be the same as those discussed for 

the Preferred Alternative. The benefits associated with 

flexibility in selecting herbicides, and in using new

herbicides that become available in the future, would be 

the same as those discussed under the Preferred

Alternative. In some instances, herbicides with lower 

risks to special status plant species could be selected

instead of herbicides that are currently being used. In 

addition, the BLM would have more flexibility to come

up with treatment programs that are more effective at

reducing weed infestations, safer for sensitive, nontarget plants, and less likely to result in reduced 

effectiveness of herbicides from repeated use than under 

the No Action Alternative. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Under this alternative, approximately 466,000 acres 

would be treated with herbicides annually, more than

under the No Action Alternative, but fewer than under 

the other herbicide-use alternatives. Based solely on 

acres treated, special status plant species would be less 

likely to be exposed to herbicides, and therefore would 

suffer fewer herbicide-related impacts than under the 

other action alternatives (with the exception of 

Alternative C). Suggested 500-foot buffers would help

to protect these species further from impacts related to

herbicide exposure, although for some herbicides this

buffer would be insufficient to prevent all impacts to

non-target sensitive plants. In the case of special status 

plant species, impacts would be similar to those under 

the other alternatives, since all herbicide treatments 

would be designed to avoid risks to these species. Risks 

for accidental exposure could be higher than under 

alternatives A and C. 

The amount of fuels reduction and control of non-native 

species, and the related benefits to special status species 

from habitat improvement would also be greater than

under alternatives A and C. Although fewer total acres

would be treated than under Alternative D, and

broadcast spraying would be minimized, the BLM

would be able to conduct aerial spraying to reduce weed

infestations in some areas if other means could not be 

used. Habitat improvements for these species would

largely depend on the amount of other treatments 

(including manual spot applications of herbicide) that 

would be feasible in these areas. 

The increased emphasis on passive restoration under 

Alternative E would likely benefit certain populations of 

special status plant species by helping to prevent the 

spread of weeds and limiting some forms of 

disturbance. With this type of management in place, it is 

possible that fewer herbicide treatments would be 

necessary in certain areas, minimizing risks to special

status plants. In areas where such restrictions would be 

inconsistent with BLM management practices, they 

would not be enacted, and no benefit to special status 

plant species would occur. 

Under this alternative, the BLM would not be able to 

use ALS-inhibiting herbicides (chlorsulfuron, imazapic, 

imazapyr, metsulfuron methyl, sulfometuron methyl, 

BLM Vegetation Treatments Using Herbicides 4-75 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

and any other ALS-inhibiting herbicides that are made 

available in the future). Chlorsulfuron, imazapyr,

metsulfuron methyl, and sulfometuron methyl pose high

risks to special status terrestrial species under scenarios 

involving spray drift, and low to high risks under 

scenarios involving surface runoff. Prohibiting use of 

these herbicides could benefit special status terrestrial

plant species, provided that one or more herbicides with 

lower risks to non-target plants were used in their stead. 

Imazapic, however, is the herbicide with the lowest risk

to sensitive terrestrial plant species out of all the

herbicides analyzed in the ERAs. Therefore, prohibiting 

its use would eliminate a suitable low risk option for 

treating weeds and other invasive vegetation such as 

downy brome, mustards, and thistles, and would require 

the BLM to use an herbicide with greater risk of

harming special status plant species, unless a safer 

replacement was made available in the future. 

The risks of ALS-inhibiting herbicides on special status 

aquatic plant species range from none to moderate, 

depending on the application rate and exposure 

scenario, and are similar to the risks associated with

most of the herbicides the BLM would be allowed to

use under this alternative. Therefore, potential impacts 

to aquatic plants from off-site drift and runoff would be 

much the same under this alternative as under 

alternatives B and D, except that there would potentially 

be less use of herbicides in riparian areas under 

Alternative E, limiting the likelihood of exposure. 

Since the BLM would be able to use new herbicides that

are made available in the future under this alternative, 

there would be more flexibility for creating effective

treatment programs that minimize risks to special status 

plant species than under alternatives A and C. Because 

of the inability to use ALS-inhibiting herbicides, 

however, this flexibility would be less than that offered 

under alternatives B and D. 

Mitigation for Herbicide Treatment Impacts 

The following mitigation is recommended to reduce the 

likelihood of impacts to special status plant species from 

herbicide applications. This mitigation should be 

implemented in addition to the SOPs designed to protect

plants presented in Chapter 2 (Alternatives) and the 

general mitigation recommended in the Vegetation 

section. 

• To protect special status plant species, 

implement all conservation measures for plants 

presented in the Vegetation Treatments on 

Bureau of Land Management Lands in 17 

Western States Programmatic Biological 

Assessment (USDI BLM 2007b). Apply these 

measures to sensitive plant species, as well as 

listed species. 

Fish and Other Aquatic 

Organisms 

Introduction 

The BLM administers lands directly affecting almost 

155,000 miles of fish-bearing streams and 4 million

acres of reservoirs and natural lakes (USDI BLM

2006c). These habitats range from isolated desert

springs of the Southwest to large interior rivers and their 

numerous tributaries throughout the Pacific Northwest

and Alaska. Today, the rapid expansion of invasive 

species across public lands is one of the primary threats 

to ecosystem health and one of the greatest challenges 

in ecosystem management. 

The BLM herbicide treatment program is designed to

benefit ecosystems by removing and controlling the 

spread of invasive plant species. In aquatic systems, 

these plants (e.g., Eurasian watermilfoil, water-thyme) 

may clog slow-moving water bodies, contaminating 

water with an overabundance of organic material. This 

organic material reduces light and dissolved oxygen 

levels, eliminating habitat and decreasing growth or 

killing native plants and animals. 

Riparian systems may be invaded by non-native species,

which can be detrimental to native aquatic species. In 

riparian areas, non-native plants (e.g., common reed, 

saltcedar, Japanese knotweed) often support fewer 

native insects than native plant species, which could 

affect food availability for insectivorous fish species, 

such as salmonids. The replacement of native riparian

plant species with some invasive species may adversely 

affect stream morphology (including shading and 

instream habitat characteristics), bank erosion, and flow 

levels. Removal of invasive species through herbicide 

use, when physical and climatic conditions and 

herbicide formulations allow treatments to be safe for

native species and water quality, can help to restore a

more complex vegetative and physical structure and 

natural levels of processes such as sedimentation and

erosion. 

BLM Vegetation Treatments Using Herbicides 4-76 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Numerous scoping comments were centered around a 

desire for the BLM to focus on long-term ecosystem

sustainability and biological diversity. There was some

concern about herbicide bioaccumulation in fish. Many

reviewers expressed a desire that the BLM use newer, 

less toxic herbicides and/or limit or avoid herbicide use. 

Standard Operating Procedures 

This assessment of impacts assumes that SOPs (listed in

Table 2-8) are used to reduce potential unintended

impacts to fish and other aquatic organisms. These 

include the following: 

• Develop and update an operational plan for 

each herbicide project that includes information 

on project specifications; key personnel

responsibilities; communication procedures;

safety, spill response, and emergency 

procedures; and minimum buffer widths for 

herbicides not approved for aquatic use. 

• Use appropriate buffer zones based on label

and risk assessment guidance. 

• Minimize treatments near fish-bearing water 

bodies during periods when fish are in life 

stages most sensitive to the herbicide(s) used, 

and use spot rather than aerial treatments. 

• Use appropriate application equipment and 

methods near water bodies if the potential for 

off-site drift exists. 

• Where feasible, use spot hand applications 

within 20 feet of perennial streams and nonperennial streams with flowing water at the

time of application. 

• Use herbicides that are least toxic to fish, yet 

still effective. 

• For treatment of aquatic vegetation, 1) treat

only that portion of the aquatic system 

necessary to achieve acceptable vegetation 

management, 2) use the appropriate application 

method to minimize the potential for injury to

desirable vegetation and aquatic organisms, 

and 3) follow use restrictions on the herbicide

label. 

Impacts Assessment Methodology 

BLM Risk Assessment Methodology 

A literature review and ERA were conducted to assess 

the impacts to fish and other aquatic resources from the 

use of herbicides. The methods presented here are a 

brief overview of the ERA process to determine the

risks of herbicide use to fish and aquatic invertebrates. 

The ERA methods are presented in detail in the 

Vegetation Treatments Programmatic EIS Ecological 

Risk Assessment Protocol (ENSR 2004) and in 

Appendix C of this document.

Problem Formulation 

Fish and aquatic species, including special status 

species, were evaluated to determine assessment

endpoints and associated measures of effect. The 

essential biological requirements (i.e., survival, growth, 

and reproduction) for each of these groups of organisms 

are the attributes to be protected from herbicide

exposure. Assessment endpoints, for the most part, 

reflect direct effects of an herbicide on these organisms,

but indirect effects were also considered. 

Measures of effect are measurable changes in an 

attribute of an assessment endpoint (or its surrogate, as 

discussed below) in response to a stressor to which it is 

exposed (USEPA 1998a). For the screening-level ERA, 

the measures of effect associated with the assessment

endpoints generally consisted of acute and chronic 

toxicity data (from pesticide registration documents and

from the available scientific literature) for the most

appropriate surrogate species. 

Exposure Characterization

The BLM uses herbicides in a variety of programs with

several different application methods. In order to assess

the potential ecological impacts of these herbicide uses,

a variety of exposure scenarios were considered. These 

scenarios were selected based on actual BLM herbicide

usage under a variety of conditions. The exposure 

scenarios considered in the ERAs were organized by 

potential exposure pathways. In general, the exposure 

scenarios describe how a particular receptor group may 

be exposed to the herbicide as a result of a particular 

exposure pathway. These exposure scenarios were 

designed to address herbicide exposure and acute and 

chronic (short- and long-term) impacts that may occur 

under a variety of conditions (e.g., accidental spills, 

surface runoff, and off-site drift into water bodies) and 

are as follows: 

BLM Vegetation Treatments Using Herbicides 4-77 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

• Direct spray of the receptor or water body 

• Off-site drift of spray to terrestrial areas and 

water bodies 

• Surface runoff from the application area to offsite soils or water bodies 

• Wind erosion resulting in deposition of 

contaminated dust into water bodies 

• Accidental spills to water bodies 

Fish and other aquatic animals are exposed to herbicides 

in three primary ways: 1) dermally, by direct absorption

through the skin from swimming in herbicidecontaminated waters; 2) breathing, by direct uptake of 

herbicides through the gills or mouth during respiration; 

and 3) orally, by drinking herbicide-contaminated water 

or feeding on herbicide-contaminated prey. The type of 

exposure depends on the nature of the application, and 

the characteristic of the herbicide and the area treated.

The susceptibility of fish and other aquatic organisms to

herbicides depends on the herbicide formulation as well

as the species exposed to it. Tolerance of fish and other 

aquatic organisms to herbicides is usually a function of 

size and metabolism. 

A major problem associated with herbicide use is offsite drift to non-target resources. Herbicides drifting off

site may eventually reach water bodies and contaminate

fish and other aquatic organisms. 

The AgDRIFT® computer model was used to estimate

off-site herbicide transport due to spray drift. The

GLEAMS computer model was used to estimate off-site

transport of herbicides in surface runoff and root zone

groundwater transport. The CALPUFF computer model

was used to predict the transport and deposition of 

herbicides sorbed (i.e., reversibly or temporarily 

attached) to wind-blown dust. Each model simulation

was approached with the intent of predicting the 

maximum potential herbicide concentration that could 

result from the given exposure scenario. 

Aquatic exposure pathways were evaluated for fish, 

aquatic invertebrates, and non-target aquatic plants in 

two types of generic aquatic habitat: 1) a small pond (1⁄4-

acre pond 1 m in depth, resulting in a volume of

1,011,715 liters); and 2) a small stream representative of 

Pacific Northwest low-order streams that provide 

habitat for critical life stages of anadromous salmonids. 

Effects Characterization

In the majority of cases, toxicological data do not exist 

for the specific ecological receptors of concern (i.e., fish

and aquatic invertebrate species of interest) considered

in the risk assessment. Consequently, toxicological data 

for surrogate species (e.g., bluegill sunfish for 

warmwater species and rainbow trout for coldwater 

species) were evaluated and used to establish 

quantitative benchmarks for the ecological receptors of

concern. These benchmark values are referred to as 

TRVs. Once developed, TRVs were compared with

predicted environmental concentrations to determine the

likelihood of adverse effects to ecological receptors. 

Risk Characterization

In order to address potential risks to ecological

receptors, RQs were calculated by dividing the EEC for 

each of the previously described scenarios by the 

appropriate toxicity endpoint, an herbicide-specific 

TRV. For fish, the TRV was a species-specific toxicity 

value derived from the literature. 

To facilitate the translation of RQs into readily

applicable estimates of risk, the calculated RQs were

compared to LOCs used by the USEPA in screening the 

potential risk of pesticides. These LOCs are used by the 

USEPA to analyze potential risk to non-target

organisms and to assess the need to consider regulatory 

action. Distinct USEPA LOCs are currently defined for 

the following risk presumption categories: 

• Acute high risk – the potential for acute risk is 

high. 

• Acute restricted use – the potential for acute 

risk is high, but may be mitigated. 

• Acute endangered species – Special status 

species may be adversely affected. 

• Chronic risk – the potential for chronic risk is 

high. 

The ecological risk implications of various exposure 

estimates can be readily determined by noting which 

RQs exceed the corresponding LOCs. 

Forest Service Methodology 

The Forest Service risk assessment methodology was 

similar to that used by the BLM (see SERA 2001a for a 

complete description of the current methodology). The 

steps involved in the Forest Service risk assessments 

BLM Vegetation Treatments Using Herbicides 4-78 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

include hazard identification, exposure assessment, dose

response assessment, and risk characterization. 

Hazard identification involved review of existing data, 

with a focus on dose-response and dose-severity 

relationships to determine the effect levels (e.g., 

NOAEL, LOAEL) and assessment endpoints (e.g., 

acute toxicity, subchronic or chronic systemic toxic 

effects, reproductive and teratogenic effects) that are 

most relevant for the herbicide risk assessments. 

In the exposure assessment phase, the Forest Service 

developed four general and accidental/incidental

exposure scenarios (i.e., direct spray, spray drift, runoff, 

and wind erosion) according to the application method

and the chemical and toxicological properties of the 

given herbicide. The Forest Service scenario of 

contaminated irrigation water—a direct application 

scenario—was not evaluated by the BLM because the 

BLM does not typically irrigate vegetation. However, 

the BLM analyzed a scenario for accidental direct spray 

over streams for all terrestrial and aquatic herbicides.

This would be the exposure route (for aquatic animals) 

most representative of what could occur while treating 

edges of ditches. 

Dose response assessment described the degree or 

severity of risk as a function of dose. The risk 

characterization process then compared the exposure 

assessment to the dose response assessment to

determine an LOC for a specific exposure scenario. 

Hazard quotients were developed through this process. 

Hazard quotients are analogous to the RQs developed in

the BLM risk assessments—they are calculated as the 

projected level of exposure (i.e., EEC) divided by an 

index of an acceptable level of exposure or otherwise

defined level of exposure (e.g., a NOAEL divided by an 

uncertainty factor). In addition, the herbicides were all

compared based on their selectivity, potency,

persistence in the environment, and ability to move off 

site. The BLM ERAs used BLM herbicide application 

rates, which may differ from those of the Forest Service. 

Adjuvants, Degradates, Inert Ingredients, and Tank

Mixes 

Adjuvants 

The BLM reviewed toxicity data for adjuvants, such as 

surfactants and anti-foam agents, to assess risks to

aquatic life. In addition, the GLEAMS model was used

to evaluate the risks associated with

polyoxyethylenamine (POEA) and R-11, surfactants 

found in some glyphosate formulations (see Appendix

D) that are more toxic to aquatic organisms than 

glyphosate itself. These adjuvants are of greatest

concern in terms of potential effects to fish and aquatic 

invertebrates. Using the GLEAMS model, the BLM 

predicted the portion of an adjuvant that would 

potentially reach an adjacent water body via surface

runoff. 

Degradates 

Degradates may be more or less mobile and more or

less toxic in the environment than their source 

herbicides (Battaglin et al. 2003). Differences in

environmental behavior (e.g., mobility) and toxicity 

between parent herbicides and degradates makes 

prediction of potential impacts challenging. For 

example, a less toxic, but more mobile, bioaccumulative

or persistent degradate may have a greater adverse 

impact due to residual concentrations in the

environment. The BLM conducted a detailed analysis of 

degradates for herbicides proposed for use under the 

herbicide treatment program. Several databases, 

including USEPA’s ECOTOX database

(http://cfpub.epa.gov/ecotox/), were searched, and 

relevant aquatic toxicity data for 11 degradates were 

identified and considered in the analysis. 

Inert Ingredients 

Relatively little toxicity information was found on inert 

ingredients during preparation of the BLM ERAs. A 

few acute studies on aquatic or terrestrial species were

reported. No chronic data, no cumulative effects data, 

and almost no indirect effects data (food chain species) 

were found for the inerts in the 10 herbicides. 

A number of the inert ingredients found in herbicides 

are List 4 compounds (Inerts of Minimal Toxicity), 

which are naturally-occurring earthen materials (e.g.,

clay materials or simple salts) that would produce no 

toxicity at applied concentrations. However, some of the 

inerts, particularly the List 3 compounds and unlisted 

compounds, may potentially be moderately to highly 

toxic to aquatic species based on information in

Material Safety Data Sheets or published data. 

As a tool to evaluate List 3 and unlisted inerts in the

ecological risk assessment, the exposure concentration 

of the generalized inert compound was calculated and 

compared to toxicity information. As described in more 

detail in Appendix D of the ERAs, the GLEAMS model

was set up to simulate the effects of a generalized inert 

compound in a base-case watershed (annual

precipitation rate of 50 inches per year, application area 

BLM Vegetation Treatments Using Herbicides 4-79 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-80 June 2007 

ogrammatic EIS 

of 10 acres, slope of 0.05, surface roughness of 0.015, 

erodibility of 0.401 tons per acre, vegetation type of 

weeds) with a sand soil type. The chemical 

characteristics of the generalized inert compound were 

set at either extremely high or low values to describe it 

as either a very mobile or stable compound. The 

application rate of the inert/adjuvant compound was 

fixed at 1 lb a.i./acre. 

Tank Mixes 

The BLM evaluated risks to aquatic organisms from 

mixing two herbicides together in a tank mix. The BLM 

assumed that products in a tank mix act in an additive 

manner. Therefore, to simulate a tank mix of two 

herbicides, RQs for those two herbicides were 

combined (see Appendix E of each ERA; diquat, 

fluridone, and tebuthiuron are not generally tank mixed 

by the BLM and were not included in the analysis). The 

application rates within the tank mix are not necessarily 

the same as those of each individual active ingredient 

applied alone. The percent of RQs exceeding LOCs for 

each of the 10 herbicide active ingredients was 

compared to the percent of RQs exceeding LOCs for 

tank mixes, to determine whether additional risks to 

aquatic organisms were predicted for tank mixes. 

Impacts by Treatment 

The potential for effects on fish and other aquatic 

populations as a result of herbicide treatments would 

vary by the extent and method of treatment and 

chemical used. Herbicides could enter water bodies and 

come into contact with fish and aquatic invertebrates 

through drift, runoff, wind transport, accidental spills, 

and direct spraying. Potential impacts include mortality, 

reduced productivity, abnormal growth, and alteration 

of critical habitat. In general, risk to aquatic 

invertebrates and fish from spray drift is greater with 

smaller buffer zones, greater application rates, and 

greater application heights (i.e., aerial application or 

ground application with a high boom). Risk to aquatic 

invertebrates and fish from surface runoff is influenced 

by precipitation rate, soil type, and application area. 

There would be a risk to aquatic invertebrates and fish 

associated with most accidental exposure scenarios (i.e., 

direct spray or spill into a water body). Persistent 

herbicides (e.g., sulfometuron methyl) adsorbed to soil 

particles could also be carried off-site by wind or water, 

affecting fish and aquatic invertebrates in nearby 

aquatic areas. However, ERAs predicted no or low 

(diuron) risk to fish as a result of wind transport of 

herbicide particles under all evaluated scenarios. 

Application rate was a major factor in determining risk, 

with higher application rates more likely to pose a risk 

to fish under the various exposure scenarios. 

The risk characterization process of the ERA suggested 

that chlorsulfuron, dicamba, diflufenzopyr, Overdrive®, 

and sulfometuron methyl are very safe to fish and 

aquatic invertebrates, as there is no risk associated with 

use of these herbicides under any of the evaluated 

scenarios, including accidental direct spray or spill. In 

addition, imazapic does not pose a risk to fish or aquatic 

invertebrates, except when directly sprayed over a 

stream at the maximum application rate. There is no risk 

to fish or aquatic invertebrates associated with off-site 

drift of bromacil or tebuthiuron. Under surface runoff 

scenarios, diuron can present a moderate to high risk to 

fish and aquatic invertebrates if applied at the maximum 

application rate. The risks to fish and aquatic 

invertebrates associated with application of aquatic 

herbicides to ponds and streams is greater for diquat 

than for fluridone, which when applied at the typical 

application rate only poses a risk to aquatic 

invertebrates in streams (aquatic herbicides are not 

typically applied to streams; therefore, this is an 

accidental scenario). Tables 4-17 and 4-18 show the 

level of risk to fish and aquatic invertebrates for the 

different herbicides and application scenarios. 

All of the herbicides pose some risk to non-target 

terrestrial and aquatic plants; these risks should be 

considered, as damage to riparian and aquatic plants 

may affect fish and aquatic invertebrates. The sections 

on Vegetation and Wetlands in this chapter discuss 

these risks, as well as herbicide application practices 

that can be used to reduce risk. 

The ALS-inhibiting herbicides evaluated in this PEIS 

are chlorsulfuron, imazapic, imazapyr, metsulfuron 

methyl, and sulfometuron methyl (all terrestrial 

herbicides). These herbicides are considered to be 

highly potent and are applied at low application rates 

because only small concentrations are necessary to 

damage plants. There is low risk to aquatic invertebrates 

associated with direct spray of imazapic or imazapyr at 

the maximum application rate. However, this risk is 

similar to or less than risks associated with the other 

evaluated herbicides, and could be avoided by applying 

at the typical application rate. Therefore, the ALSinhibiting herbicides do not appear to pose an 

unnecessary risk to fish and aquatic invertebrates. In 

addition, it is possible that because they can be applied 

at very low rates, there is less risk of off-site transport 

associated with their use. 
TABLE 4-17

Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Non Special Status 

Fish and Aquatic Invertebrates According to Exposure Scenario 

BROM1 CHLOR1 DICAMBA DIFLU1 DIQUAT DIURON FLUR1 IMAZ1 OVER1 

Application

Scenario Typ2 Max2 Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max 

Direct SprayFish pond L3 L 0 0 0 0 0 0 L L M M 0 O 0 0 0 0 Fish stream L M 0 0 0 0 0 0 L M H H 0 L 0 0 0 0 Aquatic invertebrates pond 0 0 0 0 0 0 0 0 M H M H 0 L 0 0 0 0 Aquatic invertebrates stream 0 L 0 0 0 0 0 0 H H M H 0 L 0 0 0 0 Accidental Spill to PondFish pond NE M NE 0 NE 0 NE 0 NE H NE H NE M NE 0 NE 0 Aquatic invertebrates pond NE L NE 0 NE 0 NE 0 NE H NE H NE H NE 0 NE 0 Off-Site DriftFish pond L3 L 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Fish stream L M 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates pond 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates stream 0 L 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Surface RunoffFish pond 0 0 0 0 0 0 0 0 NE NE 0 L NE NE 0 0 0 0 Fish stream 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates pond 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates stream 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 

1 BROM = Bromacil; CHLOR = Chlorsulfuron; DIFLU = Diflufenzopyr; FLUR = Fluridone; IMAZ = Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; and 2 Typ = Typical application rate; and Max = Maximum application rate.3 Risk categories: 0 = No risk (majority of RQs < most conservative LOC for non special status species); L = Low risk (majority of RQs 1-10x most conservative LOC fo

Moderate risk (majority of RQs 10-100x most conservative LOC for non special status species); H = High risk (majority of RQs >100 most conservative LOC for non Not evaluated. The risk category is based on the risk level of the majority of risk quotients observed in any of the scenarios for a given exposure group and receptor type. 

tables in Chapter 4 of the ERAs (ENSR 2005b-k) to determine the specific scenarios that result in the displayed level of risk for a given receptor group.

BLMVegetationTreatments Using Herbicides 4-81 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

Impacts of BLM-evaluated Herbicides

Bromacil 

Bromacil is a non-selective, broad-spectrum, systemic 

herbicide that can be persistent in aquatic systems. It is 

not registered for use in riparian and aquatic systems. 

Bromacil does not tend to bioconcentrate appreciably in 

fish tissue. Bromacil poses a low to moderate risk to 

fish and aquatic invertebrates in streams and ponds

under typical and accidental direct spray and spill 

scenarios. Compared to fish, aquatic invertebrates are

less sensitive to acute bromacil exposures. 

Off-site drift of bromacil generally does not pose a risk

to fish or aquatic invertebrates in streams or ponds. 

Surface runoff poses no risks to aquatic invertebrates or

fish in streams, but could pose a low acute and chronic 

risk to fish in ponds (there is a low chronic risk

associated with the typical application rate, in 

watersheds with sand or loam soils and 10 to 50 inches

per year of precipitation). Because bromacil has a

higher affinity for water than organic carbon, it is likely

to run off from soils into water bodies. 

Because of the non-selective nature of bromacil and its 

likelihood for runoff, it should not be applied near water 

bodies, especially ponds. 

Chlorsulfuron 

Chlorsulfuron is a selective, ALS-inhibitor herbicide. It

is not registered for use in aquatic systems. 

Chlorsulfuron’s physical and chemical properties 

suggest that it is highly soluble in water, and is likely to 

remain dissolved in water and runoff from soils into

water bodies. In addition, this herbicide has a long halflife in ponds, but is not likely to bioconcentrate in

aquatic wildlife. However, none of the evaluated

scenarios, including accidental direct spray and spill of

chlorsulfuron, pose any risk to fish and aquatic 

invertebrates in streams and ponds. 

Chlorsulfuron is not likely to negatively impact fish and 

aquatic invertebrates, and it may have positive effects

on these organisms if it is used to selectively target

nuisance species in riparian zones, such as perennial

pepperweed and hoary cress. 

Dicamba 

Dicamba is an active ingredient that can be used as a

stand-alone product or in the herbicide formulation

Overdrive® along with diflufenzopyr. It is not registered

for use in aquatic environments. Overdrive® can be

applied using a wick applicator in riparian areas, and 

provides good control of several thistle and knapweed 

species that can become prevalent in riparian areas. The 

ERA analysis shows that accidental direct spray and

spill scenarios do not pose a risk to fish and aquatic 

invertebrates. Off-site drift and surface runoff of 

dicamba also present no risk to fish and aquatic 

invertebrates. 

Dicamba is not likely to negatively impact fish and

aquatic invertebrates, and it may have positive effects

on these organisms if it is used to selectively target

nuisance species in riparian zones. 

Diflufenzopyr 

Diflufenzopyr, an active ingredient in the herbicide

formulation Overdrive® along with dicamba, is a 

selective, systematic post-emergence herbicide active 

ingredient. It is not registered for use in aquatic 

environments. Overdrive® can be applied using a wick 

applicator in riparian areas, and provides good control

of several thistle and knapweed species that can become

prevalent in riparian areas. The physical and chemical

properties of diflufenzopyr suggest that this herbicide 

would be removed from an aquatic environment 

relatively rapidly following contamination and would 

not appreciably bioconcentrate in fish tissue. The ERA 

analysis shows that diflufenzopyr does not pose a risk to

fish or aquatic invertebrates under direct spray and spill

scenarios. Off-site drift and surface runoff of

diflufenzopyr also present no risk to fish or aquatic 

invertebrates. 

Diflufenzopyr is not likely to negatively impact fish or 

aquatic invertebrates, and it may have positive effects

on these organisms if it is used to selectively target

nuisance species in riparian zones. 

Diquat 

Diquat is a non-selective, contact herbicide for the 

management of undesirable vegetation under noncropland terrestrial and aquatic situations. The BLM

proposes to use diquat to control aquatic plants. Plant 

species controlled using diquat include Eurasian

watermilfoil, water-thyme, water hyacinth, and giant

salvinia. 

One study reported the likelihood of bioconcentration in 

aquatic species, but other studies suggest that diquat’s 

bioconcentration potential is minimal (Howard 1991; 

BLM Vegetation Treatments Using Herbicides 4-82 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Petit et al. 1995; MacKay et al 1997). An accidental 

spill of diquat would pose a high risk to fish and aquatic

invertebrates. Direct spray of diquat to ponds, as would 

occur with typical aquatic applications, would pose a 

low risk to fish and moderate risk to aquatic

invertebrates. Direct spray to streams, which are not

typical application sites, would pose a low risk to fish 

and predominantly a high risk to aquatic invertebrates. 

Because diquat is an aquatic herbicide, risk to aquatic

organisms via off-site drift and surface runoff scenarios 

was not evaluated. 

Given the short-term risks of diquat to fish and aquatic 

invertebrates, this herbicide should be used on a 

restricted basis, and then only in ponds that support very 

few native aquatic species because they are dominated

by invasive plants. Other aquatic herbicides evaluated in

this PEIS⎯fluridone, 2,4-D, and imazapyr⎯pose much

lower risk to fish and aquatic invertebrates and could be

used instead of diquat when native aquatic species are

present, as appropriate, if they have activity on the

target species. Glyphosate is also used to control aquatic 

plants, but the risks associated with its use may be

similar to those associated with diquat, depending on

application rate, product formulation, and the receptor 

of concern. 

Diuron

Diuron is a broad-spectrum herbicide with a relatively 

short half-life and little to no impact on measured water 

quality variables (Perschbaucher et al. 2004). It would

not be used in riparian or aquatic habitats. Previous 

studies suggest that diuron tends to remain in the soil 

rather than moving into groundwater or running off into 

water bodies (Mueller-Warrant and Griffith 2005). 

Diuron has a low to moderate tendency to 

bioaccumulate in aquatic organisms (National Library 

of Medicine 2002). Accidental direct spray and spill

scenarios pose a moderate to high risk to fish and

aquatic invertebrates. When applied at the typical or 

maximum application rate, off-site drift of diuron poses 

no to low risk to fish and aquatic invertebrates. At the

maximum application rate, off-site drift of diuron poses 

low risk to fish and aquatic invertebrates in streams and

ponds under most application scenarios with a buffer 

distance of 100 feet or less. According to the ERA, 

surface runoff poses low risk to fish and no or low risk

to aquatic invertebrates in ponds in the majority of

scenarios. Surface runoff also poses a low risk to fish in 

streams in watersheds with at least 25 inches of rain per 

year (mostly at the maximum application rate), and a

low risk to aquatic invertebrates, when applied at the

typical and maximum application rates in watersheds

with at least 10 inches of precipitation per year. In all

cases, effects would be less likely in watersheds with

loam soils. 

Fluridone 

Fluridone is a slow-acting, broad-spectrum aquatic 

herbicide that can be used selectively for management 

of aquatic species, including water-thyme and Eurasian

watermilfoil. As fluridone is relatively non-persistent, it 

is not expected to affect water quality for a substantial 

period of time (Muir et al. 1980). 

Fluridone has little tendency to bioaccumulate in fish 

(Washington Department of Health 2000). An 

accidental spill of fluridone poses moderate to high risk 

to fish and aquatic invertebrates. Direct spray of 

fluridone over a pond (normal application) at the

maximum application rate poses a low risk to fish and

aquatic invertebrates. Accidental direct spray of 

fluridone over a stream (aquatic herbicides are not 

typically applied to streams) at the maximum 

application rate poses no or low risk to fish and aquatic

invertebrates. Because fluridone is an aquatic herbicide, 

off-site drift and surface runoff scenarios were not 

evaluated. 

To the extent that typical use of fluridone is successful

in removing damaging invasive vegetation with a 

minimal of residence time in the water body, water 

quality and wildlife habitat in water bodies would likely 

improve over the long term with its use. Because there

are no risks to fish and aquatic invertebrates from

normal use of fluridone at the typical application rate,

appropriate use of this herbicide would likely result in

an overall benefit to fish and other aquatic organisms. 

Fluridone poses much lower risk to fish and aquatic

organisms than diquat. 

Imazapic

Imazapic, an ALS-inhibitor, is a selective, systemic

herbicide. It would not be used for treatment of aquatic 

vegetation, but could be used in riparian areas where the 

application could be monitored to ensure that the 

herbicide would not come in direct contact with water. 

Leafy spurge and the perennial mustards would be

target species. 

The average half life for imazapic in a pond is 30 days,

and this herbicide has little tendency to bioaccumulate

in fish (Barker et al. 1998). According to the

manufacturer’s label, imazapic has a high runoff

BLM Vegetation Treatments Using Herbicides 4-83 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

potential from soils for several months or more after 

application. Accidental direct spray and spill scenarios 

generally pose no risk to fish or aquatic invertebrates 

when imazapic is applied at either the typical or 

maximum application rate. Risk assessments show fish

and aquatic invertebrates are not at risk from off-site 

drift or surface runoff of imazapic. 

When imazapic is used appropriately, it should not

impact fish or aquatic invertebrates in streams or ponds. 

There is only a low chance of risk to stream aquatic

invertebrates in the case of accidental direct spray. The

use of imazapic may have positive effects on fish and 

aquatic invertebrates if it is used to selectively target

nuisance species in riparian zones. 

Overdrive®

Overdrive® is an herbicide formulation containing the

active ingredients dicamba and diflufenzopyr. It is a 

selective, systematic herbicide, with low residence

times in water bodies and a low bioconcentration 

potential (National Library of Medicine 2002). 

Overdrive® application does not pose a risk to fish or 

aquatic invertebrates under any application scenario

(also see toxicity studies under dicamba and 

diflufenzopyr). 

Overdrive® is not likely to negatively impact fish and 

aquatic invertebrates, and it may have positive effects

on these organisms if it is used to selectively target

nuisance plant species in riparian zones, provided

herbicide use is seen as an acceptable vegetation 

treatment method in these sensitive areas. 

Sulfometuron Methyl 

Sulfometuron methyl, an ALS-inhibitor, is a broadspectrum, pre- and post-emergent herbicide. It is not

approved for use in aquatic systems, but could be used 

to treat perennial pepperweed, hoary cress, and other

weeds associated with riparian systems if the

application was made far enough from water to ensure 

that the active ingredient did not get into the water. 

Sulfometuron methyl has a relatively low residence time

in aquatic systems, and bioaccumulation in aquatic 

organisms has not been detected (Extension Toxicology

Network 1996d). 

According to ERAs, there would be no risks to fish or

aquatic invertebrates associated with the use of 

sulfometuron methyl under any of the evaluated 

scenarios. Therefore, if herbicide treatments are needed

in riparian areas, sulfometuron methyl may be able to 

effectively target nuisance plants without negative 

impacts to fish and aquatic invertebrates. In addition, 

use of sulfometuron methyl in riparian zones may have 

positive effects on fish and aquatic invertebrates if it

results in more diverse vegetation structure and native 

plant communities. 

Tebuthiuron 

Tebuthiuron is a relatively non-selective herbicide 

absorbed by plant roots through the soil. Tebuthiuron 

has little tendency to bioaccumulate in aquatic 

organisms (National Library of Medicine 2002), but 

may have a moderate residence time in water bodies 

(over 1 year in anaerobic conditions). 

Under an accidental spill scenario, tebuthiuron would

pose a low risk to fish and aquatic invertebrates in 

ponds. Accidental direct spray of tebuthiuron over the 

pond would pose a low chronic risk to aquatic 

invertebrates, and accidental direct spray over a stream

would pose a low to moderate chronic risk to aquatic

invertebrates. Fish are not at risk from accidental direct

spray. Off-site drift and surface runoff of tebuthiuron 

does not pose a risk to fish or aquatic invertebrates. 

If tebuthiuron is applied at the typical application rate, 

under normal application scenarios, it is likely to have 

little or no impact on fish or aquatic invertebrates. 

Impacts of Forest Service-evaluated Herbicides

The following information for eight herbicides used by 

the BLM is taken from ERAs prepared by the Forest

Service to support their assessment of the environmental

consequences of using these herbicides in Forest 

Service vegetation management programs. The BLM

previously evaluated and approved these eight 

herbicides in an earlier EIS—Vegetation Treatment on 

BLM Lands in Thirteen Western States (USDI BLM

1991a). 

2,4-D 

2,4-D is an herbicide that has formulations registered

for use on aquatic vegetation, including water hyacinth

and Eurasian watermilfoil, and as a tank mix partner to 

control purple loosestrife. The toxicity of 2,4-D to fish

and other aquatic organisms is relatively low (Norris et

al. 1991). Risk is greater under scenarios of direct

application to water bodies or accidental direct spills. 

The ester formulations of 2,4-D (including the BEEs 

found in Aqua-Kleen) are approximately 200 to 1,000

times more toxic to fish than the amine formulations, 

BLM Vegetation Treatments Using Herbicides 4-84 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

when toxicity is measured by acute (24- to 48-hour) 

LC50 (concentration causing 50% mortality [median

lethal concentration]) values. While these esters are

chemically stable, they are short-lived in natural water 

because of biological degradation. At the typical

application rate, 2,4-D poses a low risk to fish and

aquatic invertebrates, while at the maximum application 

rate, 2,4-D poses a moderate risk to fish and aquatic 

invertebrates under scenarios of accidental direct spray 

or spill to a stream and pond (Table 4-18). Routine

acute and chronic exposure scenarios do not pose a risk

to fish. 

Clopyralid 

Clopyralid is a selective herbicide most effectively used

post-emergence for the control of broadleaf weeds. It is 

not registered for aquatic vegetation management, but

can be used in riparian areas if the application does not

impact standing water. Clopyralid is used to treat teasel,

common cocklebur, and several species of thistles and 

knapweeds that could be found in riparian areas. Based

on limited acute bioassays, clopyralid appears to be 

relatively non-toxic to fish and aquatic invertebrates. 

The risk assessment only predicted risks to aquatic

organisms associated with accidental spill scenarios,

with low risk to fish and aquatic invertebrates for the

typical application rate and low risk to fish and

moderate risk to aquatic invertebrates for the maximum 

application rate. 

Glyphosate 

Glyphosate is a non-selective systemic aquatic 

herbicide. It can be applied as a broadcast, spot, or wipe 

application, and is effective in controlling purple 

loosestrife, common reed, cattail, and in some

situations, saltcedar. In general, glyphosate is very

immobile in soil, being readily adsorbed by soil 

particles and subject to microbial degradation (Norris et

al. 1991). This immobility reduces the potential for 

glyphosate to enter water bodies during runoff. 

Based on bioassays, technical grade glyphosate is 

classified as non-toxic to practically non-toxic in

freshwater fishes (USEPA OPP 1993). Some

formulations are more toxic to fish than technical grade

glyphosate. At the typical application rate, the less toxic 

formulation of glyphosate poses little risk to fish or

aquatic invertebrates, except under accidental spill

scenarios, for which there is a low to moderate risk to

fish and a low risk to aquatic invertebrates. At the

typical application rate, the more toxic formulation of 

glyphosate poses a high risk to fish and aquatic

invertebrates under accidental spill scenarios, and a low 

risk under routine acute exposure scenarios (moderate 

risk to sensitive fish species). At the maximum 

application rate, the less toxic formulation of glyphosate 

poses a low risk to fish and aquatic invertebrates under 

acute exposure scenarios. Accidental spills for the

maximum application rate pose moderate to high risk to

fish and low risk to aquatic invertebrates. At this same

application rate, the more toxic formulation of 

glyphosate poses a high risk to fish and a low risk to 

aquatic invertebrates under accidental spill scenarios, 

and moderate risk to fish and low risk to aquatic

invertebrates under acute exposure scenarios. Based on

these data, the USEPA classified glyphosate 

formulation as moderately toxic to practically non-toxic 

to freshwater fishes (SERA 2003a). 

Hexazinone 

According to ERAs, there is no risk to fish or aquatic

invertebrates in ponds or streams associated with any 

exposure scenario for hexazinone (accidental spill 

scenarios were not modeled). 

Bioassays on the active ingredient hexazinone and

commercial formulations that include hexazinone

indicate that commercial formulations are substantially 

less toxic than the active ingredient alone, even when

exposures are normalized for hexazinone levels (Wan et 

al. 1988). Some aquatic invertebrates, such as daphnids

and glass shrimp, are thought to be slightly more 

sensitive to hexazinone than fish. 

Imazapyr

Imazapyr is an ALS-inhibiting herbicide used in the 

control of a variety of grasses, broadleaf weeds, vines, 

brush species, and aquatic vegetation. It is effective in

the control of saltcedar, which dominates many riparian

systems in the West. Imazapyr is relatively non-toxic to 

fish and aquatic invertebrates (SERA 2004d). At the 

typical and maximum application rates, imazapyr poses

no risk to fish or aquatic invertebrates in streams or 

ponds under acute and chronic exposure scenarios. For 

the typical application rate, moderate risk is predicted 

for sensitive fish species for accidental spill scenarios,

and for the maximum application rate, high risk to

sensitive fish and low risk to tolerant fish and aquatic

invertebrates are predicted for accidental spill scenarios. 

Aquatic invertebrates have similar sensitivity to 

imazapyr as fish. Based on two studies using Daphnia 

magna, no mortality was observed at 24 or 48 hours of 

exposure of up to 100 mg/L of imazapyr; with the 

BLM Vegetation Treatments Using Herbicides 4-85 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-86 June 2007 

ogrammatic EIS 

s

second study showing a NOEC after 48 hours at 180 

mg/L (SERA 2004d). No adverse effects to fish and 

other aquatic organisms appear to be likely at either the 

typical application rate or the maximum application rate 

for a normal exposure. 

Met ulfuron Methyl 

Metsulfuron methyl is a selective ALS-inhibiting 

herbicide used pre- and post-emergence in the control of 

many annual and perennial weeds and woody plants. It 

is not registered for use in aquatic situations, but can be 

applied in riparian areas if the herbicide does not come 

into contact with water (SERA 2004e). Overall, 

metsulfuron methyl appears to have a very low potential 

to cause any adverse effects in aquatic animals. 

According to the ERAs, metsulfuron methyl poses 

almost no risk to fish or aquatic invertebrates in streams 

and ponds under accidental, acute, and chronic exposure 

scenarios involving application of typical and maximum 

rates (although an accidental spill at the maximum 

application rate poses a low risk to sensitive fish 

species). 

Values from 96-hour LC50 values for acute toxicity in 

bluegill sunfish and rainbow trout ranged from 

approximately 150 mg/L to 1,000 mg/L for both species 

(SERA 2004e). In rainbow trout, signs of sublethal 

toxicity include erratic swimming behavior, lethargy, 

and color change at concentrations around 100 mg/L, 

with a NOEC of 10 mg/L (SERA 2004e). One 

investigation did not observe any effects on rainbow 

trout hatching, larval survival, or larval growth over a 

90-day exposure period, at a NOEC of up to 4.5 mg/L 

(Kreamer 1996 cited in SERA 2004e). The NOEC of 10 

mg/L for sublethal effects in rainbow trout is 

approximately 100 times more sensitive than bluegill 

sunfish that has a NOEC of 1,000 mg/L. 

Metsulfuron methyl is relatively non-toxic to aquatic 

invertebrates. Based on acute bioassays in daphnids, 

metsulfuron methyl is relatively non-toxic, with an 

acute median exposure concentration (EC50) value for 

immobility ranging from over 150 mg/L to 720 mg/L 

and acute NOEC values for immobility ranging from 

over 150 mg/L to 420 mg/L (SERA 2004e). Typically, 

the endpoint for aquatic invertebrates when exposed to 

high concentrations of metsulfuron methyl is a decrease 

in growth rate. 

Picloram 

Picloram is a pyridine herbicide that acts as a plant 

growth regulator. It would not be used to control aquatic 

vegetation. 

The acute and chronic toxicity of picloram to aquatic 

organisms has been assayed in various species of fish 

and invertebrates. Based on studies, the USEPA 

classified picloram acid as moderately toxic to 

freshwater fish (SERA 2003b). 

According to the ERAs, when applied at either the 

typical or the maximum application rate, picloram poses 

low risk to sensitive fish species under acute exposure 

scenarios. Under accidental spill scenarios, risks to 

sensitive fish are high, risks to tolerant fish are low (for 

both application rates), risks to aquatic invertebrates are 

low for the typical rate, and risks to aquatic 

invertebrates are moderate for the maximum rate. 

Triclopyr 

Triclopyr is a selective, systemic herbicide used on 

broadleaf and woody species, including woody species 

found in riparian and aquatic areas, such as saltcedar, 

willows, and purple loosestrife. Commercial 

formulations of triclopyr may contain the acid 

formulation (TEA) or the BEE formulation; these 

triclopyr derivatives are evaluated separately in the 

Forest Service risk assessment. The risk 

characterizations for aquatic animals differ for triclopyr 

TEA and triclopyr BEE. When applied at the typical or 

maximum application rate, triclopyr TEA poses no risk 

to fish or aquatic invertebrates in streams or ponds 

under acute and chronic exposure scenarios. Under an 

accidental spill scenario, there would be low risk to fish 

and aquatic invertebrates. When applied at the typical 

rate, triclopyr BEE would pose a moderate risk to fish 

and a low risk to aquatic invertebrates under acute 

exposure scenarios, and a high risk to fish and a 

moderate risk to aquatic invertebrates under a scenario 

involving an accidental spill into a stream or pond. 

Triclopyr acid would pose a moderate risk to fish and a 

high risk to aquatic invertebrates under an accidental 

spill scenario involving the maximum application rate. 

Triclopyr BEE would pose a high risk to fish and a 

moderate risk to aquatic invertebrates under acute 

exposure scenarios at the maximum rate, and high risk 

to fish and aquatic invertebrates as a result of an 

accidental spill into a stream or pond. 

Some effects may be anticipated for fish and aquatic 

invertebrates under certain conditions. While there is a 
TABLE 4-18

Risk Categories Used to Describe Forest Service-evaluated Herbicide Effects on Fish and 

Aquatic Invertebrates According to Exposure Scenario1

2,4-D Clopyralid Glyphosate Hexazinone 2 Imazapyr Metsulfuron Methyl 

Application Scenario Typ5 Max Typ Max Typ Max Typ Max Typ Max Typ Max Acute/Accidental Exposures Fish (sensitive species) – accidental spill L6 M L L H H NE NE M H 0 L Fish (tolerant species) – accidental spill NE NE 0 0 H H NE NE 0 L 0 0 Fish (sensitive species) – acute exposure, peak EEC 0 0 0 0 M M 0 0 0 0 0 0 Fish (tolerant species) – acute exposure, peak EEC NE NE 0 0 L M 0 0 0 0 0 0 Aquatic Invertebrates – accidental spill L M L M M H NE NE 0 L 0 0 Aquatic Invertebrates – acute exposure, peak EEC 0 0 0 0 L L 0 0 0 0 0 0 Chronic Exposures Fish – chronic exposure 0 0 0 0 0 0 0 0 0 0 0 0 Aquatic invertebrates – chronic exposure 0 0 0 0 0 0 0 0 0 0 0 0 1 Risk levels are presented for the maximum application rate in aquatic applications. 2 Risk levels for the more toxic glyphosate formulation are presented here. 3 Sensitive and tolerant aquatic invertebrates were evaluated for picloram. Information is presented for sensitive aquatic invertebrates. 4 Fist value is for triclopyr acid formulation (TEA) and second value is for triclopyr butoxythel formulation (BEE).5 Typ = typical application rate; and Max = maximum application rate.6 Risk categories: 0 = No risk (HQ < LOC); L = Low risk (HQ = 1 to 10 x LOC); M = Moderate risk (HQ = 10 to 100 x LOC); H = High risk (HQ > 100 LOC); and NE = 

based on upper estimates of hazard quotients and the BLM LOCs of 0.1 for acute scenarios and 1.0 for chronic scenarios. The reader should consult the text of this sect

risk assessments to evaluate risks at central estimates of hazard quotients. 

Fish sensitive species include coldwater fish, such as trout and salmon, while fish tolerant species include warmwater fish, such as fathead minnows.

BLMVegetationTreatments Using Herbicides 4-87 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

major difference in the potential hazards posed by

triclopyr TEA formulations (which are registered for 

aquatic use; e.g., Garlon 3A®) and triclopyr BEE 

formulations (which are not registered for aquatic use;

e.g., Garlon 4®) to fish, there are no significant

differences among species in terms of sensitivity to the

various agents. Sublethal effects of Garlon 4®

 on

salmonids occur at concentrations between 0.32 and

0.43 mg/L, where fish were lethargic, while behavioral

changes to Garlon 3A® would occur at 200 mg/L. 

Subchronic toxicity in fathead minnows (at the embryolarval stages) was observed when the fish were 

subjected to 140 mg/L of triclopyr TEA for 28 days 

(Mayes et al. 1984; Mayes 1990, cited in SERA 2003c). 

This study found that survival of these minnows was 

greatly reduced at this toxicity level. 

Based on acute lethality, aquatic invertebrates are

equally sensitive as fish to the various forms of triclopyr 

(SERA 2003c). No significant effects have been noted

on frog embryos with the application of Garlon 3A® and

Garlon 4®. Studies on embryos and tadpoles of three 

frog species using Garlon 4®, exposure to 0.6, 1.2, and

4.6 ppm a.e. caused no effect on hatching success, 

malformations, or subsequent avoidance behavior of 

embryos, although the two higher concentrations were 

associated with mortality or immobility in tadpoles 

(SERA 2003c). 

Although triclopyr BEE is more toxic than triclopyr 

TEA, the risk of triclopyr BEE to aquatic animals is

low, as this formulation will rapidly hydrolyze to

triclopyr acid, lowering risk to aquatic animals. 

Impacts of Other Herbicides Currently Available for 

Use 

Asulam, atrazine, 2,4-DP, fosamine, mefluidide, and

simazine were approved for use in the earlier BLM

EISs. Research shows asulam, fosamine, mefluidide, 

and simazine are practically nontoxic to cold- and 

warmwater fish (rainbow trout and bluegill sunfish,

respectively) while asulam is slightly toxic to aquatic

invertebrates (Daphnia magna; Extension Toxicology

Network 1993; USEPA 1995b, d; English Nature 2003). 

Data show that atrazine may cause reductions in

phytoplankton, zooplankton, aquatic invertebrate, and 

fish populations, but in general, is not acutely toxic

(USEPA 2003b). 2,4-DP may be toxic to aquatic

organisms. The 2,4-DP butoxy ethyl ester (technical) is 

highly toxic to fish, but practically nontoxic to 

freshwater invertebrates (Wan et al. 1990). The BLM 

has not used any of these herbicides, except fosamine 

(less than 50 acres annually), since 1997. 

Impacts of Adjuvants, Degradates, Inert Ingredients, 

and Tank Mixes 

Adjuvants 

Various sources of toxicity data (Muller 1980; Lewis 

1991; Dorn et al. 1997; Wong et al. 1997) suggest that, 

for herbicides with high application rates, adjuvants 

have the potential to cause acute, and potentially 

chronic, adverse effects to aquatic species. 

Based on GLEAMS modeling for POEA, risks to

aquatic organisms were not predicted for the majority of 

pond and stream scenarios involving exposure to this 

adjuvant. However, risks were predicted (using the most

conservative acute endangered species LOC) for 

applications at a distance of 0 feet from the water body. 

This scenario, which essentially assumes a direct 

application to the water body with no dilution or drift, is 

highly conservative and highly unlikely under BLM

application practices. Risks to special status aquatic 

organisms in streams and ponds were also predicted for 

aerial applications of POEA at the maximum rate at a

distance of 100 feet from the water body. Therefore, a 

buffer zone of greater than 100 feet is necessary for 

aerial applications of POEA at the maximum rate in an 

area containing special status aquatic species. However,

it is unlikely that the BLM would apply glyphosate 

formulations containing POEA in an area known to 

contain special status aquatic species. 

For non special status species, the only predicted risks 

to aquatic organisms occurred under scenarios involving

POEA applications at the maximum application rate, at 

a distance of 0 feet from the water body. As stated

previously, this scenario is highly unlikely and assumes 

zero dilution and no drift (i.e., essentially direct

application). Furthermore, even under these conditions, 

risks are predicted only for fish, not invertebrates or 

amphibians. This assessment indicates that even under 

conservative conditions (scenarios with the most

conservative amount of drift, and herbicide applications

at the maximum rate) the potential risks to aquatic

receptors from POEA would be minimal. 

Because of a lack of physical chemical property 

information, POEA was not modeled for leaching 

properties and runoff to water bodies and aquatic

receptors. Therefore, there is some uncertainty 

associated with risk from this exposure. 

The adjuvant R-11 is a nonylphenol ethoxylate that is 

acutely toxic to aquatic life (Stark 2003) and is 

suspected to be an endocrine-disrupting chemical

BLM Vegetation Treatments Using Herbicides 4-88 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

(Bakke 2003). The BLM has decided to suspend the use 

of R-11 in its herbicide applications. 

When selecting adjuvants, BLM land managers must

follow all label instructions and abide by any warnings. 

In general, adjuvants compose a relatively small portion

of the volume of herbicide applied. Nonetheless, 

selection of adjuvants with limited toxicity and low 

volumes is recommended for applications near aquatic 

habitats to reduce the potential for the adjuvant to

influence the toxicity of the herbicide. 

Degradates 

Based on a review of toxicity data for adjuvants, in most

cases, predicted risks to aquatic organisms from

degradates would likely be less than risks from the 

active ingredients diquat, diuron, imazapyr, and

metsulfuron methyl predicted in ERAs. For some 

degradates associated with 2,4-D, diuron, fluridone, and 

triclopyr, selected aquatic species may be more 

sensitive to the degradate than to the active ingredient.

These findings should be considered in the context of 

herbicide use practices, the concentration of degradate

relative to the parent compound, the process of 

degradate production, and the body of available toxicity

data. For instance, in some cases, the increased toxicity 

of the degradate may be offset by the fact that only a 

minute amount of the degradate is produced, which 

would likely disperse rapidly in an active aquatic

system. Furthermore, focusing on a single toxicity study 

may be overly conservative and may not be 

representative of risks found in the field or in other 

laboratory studies. 

Inert Ingredients 

Based on GLEAMS modeling of a generalized inert

compound in a “base case” watershed, concentrations of 

inert ingredients exceeded concentrations of herbicide

active ingredients under all stream and pond scenarios. 

In general, greater exposure concentrations of inerts 

occurred under higher application rates, exceeding 1 

mg/L for the maximum pond application scenario. 

These results suggest that inerts associated with the 

application of herbicides may contribute to acute

toxicity to aquatic organisms if they reach the aquatic

environment. However, given the lack of specific inert

toxicity data, this statement may overestimate their 

potential toxicity. It is assumed that toxic inerts would

not represent a substantial percentage of the herbicide, 

and that minimal impacts to the environment would

result from these inert ingredients. 

Tank Mixes 

Risk assessment analysis of tank mixes indicates that

risks to aquatic organisms vary by tank mix. The risks 

to fish and aquatic invertebrates associated with 

applications of tank mixes of bromacil plus 

sulfometuron methyl, and imazapic plus diflufenzopyr 

are no greater than those associated with applications of 

bromacil, imazapic, or diflufenzopyr alone. Risks to

aquatic receptors for a tank mix of chlorsulfuron and

diuron are greater than those for chlorsulfuron (but not

diuron) alone, and risks for a tank mix of sulfometuron

methyl and bromacil are greater than for bromacil 

applied alone. 

There is some uncertainty in this evaluation because

herbicides in tank mixes may not interact in an additive

manner; this may overestimate risk if the interaction is 

antagonistic, or it may underestimate risk if the 

interaction is synergistic. In addition, other products 

may also be included in tank mixes and may contribute 

to the potential risk. 

To reduce the potential for negative impacts to aquatic

organisms, BLM land managers must follow all label 

instructions and abide by any warnings. Labels for both 

tank mixed products should be thoroughly reviewed, 

and mixtures with the least potential for negative effects 

should be selected, particularly when a mixture is

applied in a manner that increases the potential for risk

to nearby aquatic organisms. 

Impacts by Alternative 

Important invasive species that would be treated by the 

BLM using herbicides include water-thyme and 

Eurasian watermilfoils, which are found in ponds, lakes, 

and streams; and perennial pepperweed, saltcedar, 

knapweed, and thistles, which are found in riparian

habitats. These species displace native vegetation and 

decrease species diversity. Dense concentrations of 

aquatic plants can lower the concentration of dissolved

oxygen in the water and can upset the balance of the 

fish community by providing too much cover for small

fish (Payne and Copes 1986). Invasive riparian plants 

form monocultures that crowd out more desirable native 

plant species. 

The BLM proposes to treat aquatic and riparian

vegetation to improve habitat for fish and aquatic 

organisms on public lands. However, herbicide

treatments can also lead to the harm or even death of 

fish and aquatic organisms. The following discusses the 

BLM Vegetation Treatments Using Herbicides 4-89 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

habitat benefits and health risks to fish and aquatic 

organisms under each alternative. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation treatment programs in

14 western states, and would be able to use 20

herbicides previously approved under earlier RODs. 

Herbicide use under the No Action Alternative would 

impact target and non-target vegetation over an 

estimated 305,000 acres annually, including

approximately 2,250 acres of riparian and aquatic

habitat. Herbicides used to manage aquatic and riparian

vegetation under this alternative could include select 

formulations of 2,4-D, glyphosate, and imazapyr, and

certain formulations of triclopyr in riparian areas where

contact with water could be avoided. The BLM would 

not be able to use herbicides to treat public lands in 

Alaska, Nebraska, or Texas under this alternative. 

The nature of impacts to fish and aquatic invertebrates 

(positive and negative) would be similar to those that

have occurred in recent years. Negative impacts to fish

and aquatic invertebrates associated with herbicide use 

would be lower than under the other herbicide treatment

alternatives (B, D, and E) because far fewer acres would

be treated. However, long-term positive impacts to

riparian and aquatic vegetation communities and

resulting positive impacts on fish and aquatic

invertebrates would also be lower under this alternative. 

These positive long-term impacts to fish and aquatic 

invertebrates include improvement of riparian and 

instream habitat, through eradication of aquatic weeds 

that dominate water systems and the resulting increase 

in dissolved oxygen content, and the regrowth of native 

riparian vegetation and increase in shade habitat. 

In addition, because the new herbicides proposed in this 

PEIS (Overdrive®, diquat, fluridone, and imazapic) 

would not be used, risks to fish and aquatic

invertebrates would be different under this alternative. 

Because the BLM would not use the new herbicides,

which have low risks to aquatic wildlife, per area risks 

to fish and aquatic invertebrates from accidental and 

drift scenarios could be greater than under the other 

herbicide-use alternatives. Furthermore, fluridone is 

specifically indicated for aquatic use, whereas none of 

the other previously-approved herbicides are strictly

aquatic herbicides. Diquat and select formulations of

2,4-D would be used in the aquatic vegetation treatment

program, both of which have been effective in the 

control of Eurasian watermilfoil and water-thyme. The 

other herbicides registered for aquatic use, glyphosate 

and triclopyr, are not as effective in controlling these

species. 

Under this alternative, the BLM would be able to 

continue to use asulam, atrazine, 2,4-DP, fosamine, 

mefluidide, and simazine on public lands, although 

these chemicals have not been used, or used sparingly 

(fosamine) since 1997. These chemicals are not 

approved for use in riparian and aquatic habitats, except

for 2,4-DP, which could be used to treat western

brackenfern in riparian habitats. Except for 2,4-DP, 

these herbicides are practically nontoxic to slightly toxic 

to freshwater fish. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

The Preferred Alternative would result in the herbicide 

treatment of approximately 932,000 acres annually

across 17 western states, of which about 10,100 acres 

would consist of aquatic and riparian habitat. The BLM

would only be allowed to use 14 previously-approved

herbicides, six fewer than under the No Action 

Alternative, but would also be able to use the four new 

herbicides evaluated in this PEIS. In addition, the BLM 

would be able to treat vegetation using herbicides in 

Alaska, Texas, and Nebraska, although it is anticipated

that few or no herbicide treatments would occur in

Alaska. 

As this alternative proposes to treat the most acres of all

the alternatives (more than four times the acreage 

proposed under the No Action Alternative), it could 

result in the most extensive impacts to fish and aquatic 

invertebrates. The potential for acute and chronic toxic 

effects to fish and other aquatic organisms could be four 

times greater under this alternative than under the other 

alternatives, due to the greater acreage that would be 

considered. 

The BLM’s ability to use four new chemicals (fluridone 

and diquat for aquatic applications, and imazapic and 

Overdrive® for terrestrial applications), could reduce 

risks to fish and other aquatic organisms. For example, 

fluridone shows no risks to aquatic organisms at normal

application rates and could replace other aquatic 

herbicides currently used by the BLM on public lands.

It appears to be effective in the control of Eurasian

watermilfoil and water-thyme, and can be used instead 

of diquat in states where diquat is not legal for use in

aquatic systems, such as California (Bossard et al. 

2000). 

BLM Vegetation Treatments Using Herbicides 4-90 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Overdrive® and imazapic would primarily be used on 

rangelands, but could still provide benefits greater than

those under the No Action Alternative. Overdrive®

would be used to treat thistles and knapweeds, while 

imazapic could be used to control downy brome. These

invasive plant species degrade riparian and rangeland 

habitats and can lead to shortened fire cycles, followed

by soil erosion and sedimentation. Under accidental

direct spray and spill and off-site drift scenarios, 

Overdrive® and imazapic present very low or no risks to

fish and aquatic invertebrates, similar to chlorsulfuron, 

diflufenzopyr, and sulfometuron methyl but lower than 

the risks associated with other herbicides currently 

being used. For the surface runoff scenarios that were

evaluated, risks to fish and aquatic invertebrates were 

not predicted for any of the new herbicides, whereas 

some of the other herbicides do present risk to these 

organisms under some surface runoff scenarios. Each of 

the currently available and new herbicides evaluated in 

this PEIS has different properties (e.g., mode of action), 

is suggested for different uses, and is most

effective/least risky in different scenarios, suggesting

that the more herbicides available for use, the easier it is

to select one or more that would present the least risk to

fish and aquatic invertebrates for specific aquatic 

applications or terrestrial applications near water bodies. 

Under the Preferred Alternative, the BLM would be 

able to use new herbicides approved in the future under 

the Preferred Alternative. Use of these herbicides could 

potentially reduce risks to fish and aquatic organisms 

associated with herbicide use, particularly if they were

less toxic or used in smaller quantities than currently 

used and proposed herbicides. 

Alternative C – No Use of Herbicides 

Under Alternative C, fish and aquatic invertebrates 

would not be affected by herbicide use; effects would

stem from other vegetation treatment methods (see the 

accompanying PER). Ecosystem benefits resulting from 

vegetation management could be reduced under this 

alternative, as there are certain invasive species for 

which herbicide use is the only effective method of 

treatment or for which treatment using other methods is

impractical due to cost, time, accessibility, or public

concerns. For example, rough terrain may not allow 

treatment by methods requiring terrestrial vehicle and

foot access, but these inaccessible areas could

potentially be treated using herbicides applied by 

aircraft. Other treatment methods, such as mechanical

methods and fire use, can result in soil disturbance and 

sedimentation of aquatic bodies, and may not 

adequately treat the pest plant. 

In addition, it is often difficult to eradicate some

species, such as aquatic species and those that resprout 

from rhizomes, by means other than herbicide

application. For example, Eurasian watermilfoil and 

water-thyme form dense mats that crowd out native

aquatic plants and degrade fish habitat (Bossard et al. 

2000), and in some cases chemical treatments, including

the use of 2,4-D, diquat, and fluridone, are more 

effective than other treatments, such as mechanical

harvesters that tend to fragment and spread the weed.

This treatment alternative would likely leave many

aquatic areas untreated, resulting in continued negative 

impacts to the aquatic species that are native to these 

areas. 

Alternative D – No Aerial Applications 

Alternative D would allow use of the same herbicides in

the same areas as under the Preferred Alternative, and 

would have similar benefits associated with the 

increased availability of new and future herbicides. 

Although this alternative would not allow the use of 

aerial application methods, thereby reducing the total

potential treatment acreage (to 530,000 total acres), 

there would have little difference between Alternative D 

and the Preferred Alternative as far as acreage treated in 

aquatic and riparian habitats. Nearly all (98%) of the 

acres proposed for treatment in aquatic and riparian 

habitats under the Preferred Alternative would be 

treated using ground-based methods, and therefore 

could also be treated under Alternative D. This 

alternative would substantially reduce the potential for 

impacts to water bodies as a result of off-site drift from

application on upland habitats. Drift is a major route of 

unintended damage to water bodies and resident fish

and aquatic invertebrates, with aerial application the

primary cause of off-site drift. Therefore, per area

impacts would be much lower under this alternative 

than under the No Action Alternative and the Preferred

Alternative, and would be similar to or less than per 

area impacts from Alternative E. However, without the 

use of aerial spraying, large areas of vegetation would 

remain untreated under Alternative D, which could lead

to continued or future degradation of upland habitats to

the detriment of nearby streams and other aquatic 

habitats. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Approximately 466,000 acres would be treated under 

Alternative E, which is slightly less than the acreage

that would be treated under Alternative D, and less than

half of the acreage that would be treated under the 

BLM Vegetation Treatments Using Herbicides 4-91 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Preferred Alternative. In addition, the BLM would not

be able to use ALS-inhibiting active ingredients (i.e., 

chlorsulfuron, imazapic, imazapyr, metsulfuron methyl,

and sulfometuron methyl). 

Of the herbicides that would be unavailable to the BLM

under this alternative, imazapyr is the only one that 

could be used in riparian and aquatic habitats, where it 

has been shown to be very effective against saltcedar.

Imazapyr poses little risk to fish and aquatic organisms

when used at typical application rates. Without

imazapyr, the BLM would likely treat larger stands of

saltcedar using prescribed fire followed by a foliar 

application of triclopyr, and smaller stands by cutting

the stem and applying triclopyr. 

Chlorsulfuron, imazapic, and sulfometuron methyl do 

not pose risks to fish or aquatic invertebrates. 

Metsulfuron methyl poses a low risk to aquatic

invertebrates in streams under an accidental direct spray 

scenario involving the maximum application rate (an

unlikely scenario). Therefore, disallowing use of these

four herbicides would be unlikely to benefit fish and

aquatic organisms if they are replaced with herbicides 

that are more harmful to fish and other aquatic 

organisms. 

Alternative E incorporates other management practices 

that would be likely to have positive effects on fish and 

aquatic invertebrates. In addition, herbicides would not 

be used in riparian conservation areas, which would 

protect aquatic species and attendant ecosystem 

functions in these key habitats. 

Mitigation for Herbicide Treatment 

Impacts 

The following recommended general management 

practices are designed to reduce potential unintended

impacts to non special status fish and aquatic 

invertebrates from the application of herbicides in the

BLM vegetation management program. Mitigation 

appropriate for special status species is later in this

section under Special Status Fish and Other Aquatic 

Organisms. 

• Limit the use of diquat in water bodies that 

have native fish and aquatic resources. 

• Limit the use of terrestrial herbicides 

(especially diuron) in watersheds with fishbearing streams during periods when fish are in

life stages most sensitive to the herbicide(s) 

use. 

• Establish appropriate herbicide-specific buffer 

zones for water bodies, habitats, and aquatic 

species of interest (see Table 4-19, Appendix 

C, Table C-16, and recommendations in 

individual ERAs). 

• Avoid using the adjuvant R-11® in aquatic 

environments, and either avoid using 

glyphosate formulations containing POEA, or 

seek to use formulations with the least amount 

of POEA, to reduce risks to aquatic organisms. 

• Consider the proximity of application areas to 

salmonid habitat and the possible effects of 

herbicides on riparian and aquatic vegetation. 

Maintain appropriate buffer zones around 

salmonid-bearing streams (see Appendix C, 

Table C-16, and recommendations in

individual ERAs). 

These practices would help minimize impacts to fish,

aquatic invertebrates, and aquatic ecosystems on public 

lands to the extent practical. 

Special Status Fish and Other Aquatic 

Organisms 

Introduction

As discussed in Chapter 3, public lands in the western

U.S. support over 150 species of aquatic animals that

have been given a special status based on their rarity or 

sensitivity. Included are 78 species of fish, 13 mollusks, 

and 7 species of aquatic arthropods that are federallylisted as threatened or endangered, or are proposed for 

federal listing. Populations of non-native aquatic species 

and riparian weeds may alter aquatic habitats, making 

them less suitable for special status fish and aquatic 

invertebrates. The Vegetation Treatments on Bureau of 

Land Management Lands in 17 Western States 

Programmatic Biological Assessment (USDI BLM 

2007b) provides a description of the distribution, life 

history, and current threats for each federally-listed

animal species, as well as species proposed for listing. 

Impacts Assessment Methodology 

Beginning in spring 2002, the BLM participated in an

Ad Hoc Interagency Team to address the effects of 

invasive vegetation and noxious weed treatments on 

humans, plants, and animals. This team consisted of

ecologists and toxicologists from the BLM, USEPA, 

NMFS, and USFWS. 

BLM Vegetation Treatments Using Herbicides 4-92 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

TABLE 4-19

Buffer Distances to Minimize Risk to Non Special Status Fish and Aquatic Invertebrates 

from Off-site Drift of BLM-evaluated Herbicides from Broadcast and Aerial Treatments 

Application 

Scenario BROM1 CHLR DICA DIFLU DIQT DIUR FLUR IMAZ OVER SULF TEBU 

Minimum Buffer Distance (feet) from Fish and Aquatic Invertebrates

Typical Application Rate 

Aerial NA 0 NA NA NA NA NA 0 NA 0 NA 

Low boom 0 0 0 0 NA 0 NA 0 0 0 0 

High boom 0 0 0 0 NA 0 NA 0 0 0 0 

Maximum Application Rate 

Aerial NA 0 NA NA NA NA NA 0 NA 0 NA 

Low boom 0 0 0 0 NA 100 NA 0 0 0 0 

High boom 0 0 0 0 NA 100 NA 0 0 0 0 

1 BROM = Bromacil; CHLR = Chlorsulfuron; DICA = Dicamba; DIFLU = Diflufenzopyr; DIQT = Diquat; DIUR = Diuron; FLUR = Fluridone; IMAZ = 

Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; and TEBU = Tebuthiuron.

NA = Not applicable. 

Boom height = The Tier I ground application model allows selection of a low (20 inches) or a high (50 inches) boom height.

In May 2002, the BLM began the process of developing 

the assessment procedures that would be followed while 

conducting ERAs. This process involved close 

coordination with NMFS, the USFWS, and the USEPA; 

representatives of these agencies participated in weekly 

telephone calls with the BLM and its contractor who

prepared the ERAs. These agencies also provided 

information they felt was necessary to meet their 

requirements for consultation under the ESA, and

reviewed draft work products prepared by the BLM

contractor. In November 2002, the BLM submitted a 

draft Vegetation Treatments Programmatic EIS 

Ecological Risk Assessment Protocol to the USEPA, 

NMFS, and USFWS. Comments from these agencies 

were used in the development of the final ERA protocol 

(ENSR 2004). Risk assessments for 10 chemicals were 

completed in May 2005 (ENSR 2005b-k). Information

from the ERAs is included in the BA and in this section, 

including information on likely risks to special status 

fish and other aquatic resources, and on SOPs that

should be followed to minimize these risks. 

The BLM also reviewed the literature and findings from 

ERAs conducted by the Forest Service to assess the 

impacts to sensitive fish and aquatic invertebrate species 

from the use of eight herbicides currently used by the 

BLM (2,4-D, clopyralid, glyphosate, hexazinone, 

imazapyr, metsulfuron methyl, picloram, and triclopyr; 

SERA 2005a). The ERA methods are summarized

earlier in this section. Methods used by the BLM are 

presented in detail in the Vegetation Treatments 

Programmatic EIS Ecological Risk Assessment

Protocol (ENSR 2004) and in Appendix E; methods 

used by the Forest Service are available at

http://www.fs.fed.us/r6/invasiveplant-eis/. 

There are potential risks to sensitive fish and aquatic

invertebrate species. Although the predicted risks for 

adverse health effects to individual organisms are the 

same as those predicted for non special status fish and 

aquatic invertebrate species, the associated populationand species-level effects would be much greater for 

many sensitive species because of their 

limited/fragmented distribution and limited population

size. Risks to special status fish and aquatic invertebrate 

species can be minimized by following certain SOPs,

which can be implemented at the local level according 

to specific conditions (see Table 2-8). These SOPS 

include the following: 

• Survey for special status fish and aquatic 

invertebrate species before treating an area.

Consider effects to special status species when 

designing herbicide treatment programs. 

• Use drift reduction agents to reduce the risk of 

drift hazard. 

• Select herbicide products carefully to minimize 

additional impacts from degradates, adjuvants, 

inert ingredients, and tank mixtures. 

• Maintain appropriate buffer zones between 

treatment areas and water bodies with special 

status fish and aquatic invertebrates. 

• Minimize treatments near water bodies during 

periods when fish and aquatic invertebrates are 

BLM Vegetation Treatments Using Herbicides 4-93 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

in the life stage most sensitive to the herbicide 

used. 

Summary of Herbicide Effects to Special Status Fish

and Aquatic Invertebrates 

The invasion and spread of non-native plant species into

aquatic and riparian habitats may affect certain

populations of special status fish and aquatic 

invertebrates. An overview of the ways in which nonnative aquatic and riparian plants may affect aquatic 

habitats is presented earlier in this section. As discussed 

in the BA, numerous listed fish and other aquatic

species are threatened by the changes in water quality 

and flow which may result from weed infestations. 

Salmon, for example, require a high level of dissolved

oxygen, which is reduced when aquatic weeds such as 

Eurasian watermilfoil and water-thyme invade an 

aquatic system. A decrease in dissolved oxygen

associated with the encroachment/excessive growth of

vegetation has also been listed as a threat to the Foskett

specked dace in south-central Oregon (USFWS 1985) 

and the unarmored threespine stickleback in southern

California (NatureServe Explorer 2001). For species 

such as these, herbicide treatments to reduce coverage 

of non-native plant species in aquatic and riparian 

habitats would likely improve habitat over the long 

term. 

Numerous special status aquatic animals, however, are

most threatened by changes in water levels and quality 

associated with development, upslope land use 

practices, and groundwater pumping, and the expansion

of non-native fish populations. For most of the aquatic 

animals discussed in the BA, invasions of non-native

plant species into riparian and aquatic habitats were not 

listed as threats to the species’ survival. For these

animals, health risks and increased inputs of chemicals 

into the water associated with herbicide spraying could 

outweigh any habitat improvements resulting from 

minimized weed infestations. In addition, some

herbicide treatments could have short-term adverse 

effects on special status fish and aquatic invertebrates 

by killing non-target native vegetation and reducing the 

overall cover of riparian vegetation that regulates water 

temperature through shading. It is also likely, however, 

that the weed infestations (if present) in or near the 

aquatic habitats that support some of these species do

not currently require herbicide treatments under the 

BLM’s vegetation management programs. 

A more conservative LOC of 0.05 was used to

determine risks to special status fish and aquatic 

invertebrates. The potential effects of herbicides on 

special status aquatic animals could be greater than the 

effects on non special status fish and other aquatic 

organisms (an LOC of 0.1 was used for non special 

status species), as shown in Table 4-20 for BLMevaluated herbicides. Aquatic herbicides with the

greatest likelihood of impacting special status fish and

aquatic invertebrates during a normal application to an 

aquatic habitat include diquat and the more toxic 

formulation of glyphosate. Normal aquatic applications

of 2,4-D and imazapyr would not pose a risk to special

status fish or aquatic invertebrates. 

Terrestrial herbicides with the greatest likelihood of 

impacting special status aquatic animals as a result of a

spill, drift, accidental direct spray into an aquatic

habitat, or surface runoff are diuron, picloram, and the 

more toxic formulation of glyphosate. According to 

ERAs, there would be no risks to fish or aquatic 

invertebrates associated with chlorsulfuron, dicamba, 

diflufenzopyr, imazapic, Overdrive®, or sulfometuron

methyl. 

Alternative A – Continue Present Herbicide Use 

(No Action Alternative) 

Under this alternative, approximately 2,300 acres of

aquatic and riparian habitats and 302,700 acres of 

upland habitats on public lands would be treated with

herbicides annually. Considering acreage alone, it is 

likely that special status fish and aquatic invertebrates 

would be exposed to herbicides less under this 

alternative than under the other herbicide-use 

alternatives. Adverse health risks associated with 

herbicide exposure should be less extensive, as well. 

Risks to special status species would also be lower,

although mitigation would be required to protect these 

species and their habitat from harm under all

alternatives, which should minimize differences in risk

to special status species. 

Control of weed infestations in aquatic and riparian

areas would be less extensive under the No Action 

Alternative than under the other herbicide-use 

alternatives. Therefore, the degree of benefit to special

status aquatic animals, particularly species that are 

currently threatened by infestations of non-native plants, 

would likely be lower than under the other herbicideuse alternatives. However, short-term adverse impacts 

to habitats that support special status aquatic animals 

(such as increased water temperatures) would be lower 

as well. The degree of benefits versus impacts to these 

habitats from treatments would largely depend on where 

the treatments occurred. 

BLM Vegetation Treatments Using Herbicides 4-94 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Under this alternative, only those herbicides currently

used by the BLM would be used to treat vegetation. 2,4-

D, glyphosate, imazapyr, and triclopyr acid would be

used in aquatic and riparian habitats. Certain herbicides 

that are not registered for aquatic use (i.e., dicamba and

clopyralid) could also be used in riparian areas, 

provided the herbicide did not contact the water. Of 

these herbicides, only glyphosate is likely to pose 

toxicological risks to special status fish and aquatic

invertebrates during a normal application, but only if the 

more toxic formulation is used, or the less toxic 

formulation is applied at the maximum application rate. 

Although risks associated with an accidental spill would

be greater, continuing use of these herbicides to treat

riparian and aquatic vegetation should continue to pose 

a low risk to special status aquatic animals. 

Alternative B – Expand Herbicide Use and 

Allow for Use of New Herbicides in 17 Western 

States (Preferred Alternative) 

Under the Preferred Alternative, approximately 10,000 

acres of aquatic and riparian habitats and 922,000 acres 

of upland habitats on public lands would be treated with 

herbicides annually. Based on acreage, this alternative 

would entail the greatest amount of herbicide exposure 

to special status fish and aquatic invertebrates. Although

a greater amount of herbicides would be used in aquatic

and riparian habitats than under the other alternatives, 

risks to aquatic animals from their normal use would 

remain minimal, provided glyphosate was only applied 

at typical application rates, and only the less toxic 

formulation was used. However, since more terrestrial

herbicides would be used under this alternative as well,

risks associated with accidental spill of those herbicides 

in or near a water body, and accidental direct spray into

a water body, would also be greater than under the other 

alternatives. 

The most extensive control of weed infestations in 

aquatic and riparian areas would occur under this 

alternative. Therefore, the degree of benefit to special 

status aquatic animals over the long term through

habitat improvements would potentially be greater than 

under the other alternatives. As under the other 

alternatives, the degree of benefits versus impacts to 

these habitats from treatments would largely depend on

where the treatments occurred. 

Under the Preferred Alternative, the BLM would be 

able to use 14 of the 20 currently-approved herbicides 

that are currently available for use under the No Action

Alternative, as well as four new herbicides and other 

new herbicides that become available in the future. One

of the two new aquatic herbicides that could be used

under this alternative, diquat, would pose low to high

risks to fish, and moderate to high risks to aquatic 

invertebrates during a normal application, depending on

the application rate and type of aquatic habitat. 

Fluridone would pose no to moderate risks to fish and

aquatic invertebrates, depending on the application rate 

and type of aquatic habitat. Use of diquat or fluridone in 

place of safer aquatic herbicides under the Preferred

Alternative would likely increase the incidence of 

adverse health effects to aquatic organisms per area 

treated, relative to the No Action Alternative. Dicamba,

Overdrive®, and imazapic pose no risk to fish or aquatic

invertebrates. Therefore, these herbicides would provide 

the BLM with increased safe options for treating

riparian areas under the Preferred Alternative. 

Herbicides that become available in the future could 

allow the BLM even more flexibility to develop 

effective treatment programs in and near aquatic 

habitats, while minimizing risks to special status aquatic 

organisms. 

Alternative C – No Use of Herbicides 

Under this alternative, no public lands would be treated

with herbicides. Therefore, there would be no impacts 

to special status aquatic animals as a result of herbicide 

exposure during vegetation treatments. The BLM would 

likely be less effective at controlling weed infestations 

than under the other alternatives, so there would be 

fewer benefits to special status fish and aquatic 

invertebrate habitat that is degraded by non-native 

species. In addition, if other treatment methods were 

used to control weeds in riparian areas in lieu of 

herbicides, the disturbance to habitat could be greater. 

Mechanical methods and containment using domestic 

animals, for example, can result in greater

sedimentation into aquatic habitats and more extensive

removal of riparian vegetation, as compared to 

herbicide treatments, which would affect water quality.

Alternative D – No Aerial Applications 

Under this alternative, approximately 530,000 acres 

would be treated with herbicides annually, more than

under all other alternatives except the Preferred

Alternative. However, the amount of riparian and 

aquatic habitat treated would be similar to the amount

that would be treated under the Preferred Alternative, 

since ground-based methods would be used to apply

herbicides to 98% of the treated acreage in these

habitats. Therefore, the risks to aquatic animals from 

exposure to herbicides would potentially be somewhat

lower, but not substantially different, than under the

BLM Vegetation Treatments Using Herbicides 4-95 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

Preferred 

aquatic habitats that suppo

aquatic invertebrates would

drift than u

alternatives, si

adjacent upland areas. 

The am

term

associated 

the sa

the herbicides available for 

the sa

Alternative. The risks associ

fluridone, and the benefits a

selecting herbicides, and in using new herbicides that 

beco

those discussed under the Pr

Alternative E – No Use of

In

Under this al

would be treated with herbicides annually

under the No 

the other herbicide-use 

herbicide use in riparian and aquatic habi

mini

conservation areas and li

applications. These 

mini

invertebrates 

special status aquatic anim

would be lower than under the Preferred Alt

Alternative C, and in so

under No Acti

The li

restrictions on herbicide treat

habitats would li

herbicides to 

Accordingly, t

to habitats that support aquatic ani

mini

to special status fish and aquatic invertebrates would

depend on wh

occur, and whether the 

treat

treat

that support special status species. 

Under this alt

use chlorsulfuron, i

meth

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-96 June 2007 

ogrammatic EIS 

Alternative. It is likely that riparian and 

rt special status fish and 

 be exposed to less off-site 

nder the No Action and Preferred 

nce aerial spraying would not occur in 

ount of long-term benefit, as well as the short-

 adverse impacts, to riparian and aquatic habitats 

with herbicide applications would be much 

me as under the Preferred Alternative. In addition, 

use by the BLM would be 

me as those discussed for the Preferred 

ated with using diquat and 

ssociated with flexibility in 

me available in the future, would be the same as 

eferred Alternative. 

 Acetolactate Synthasehibiting Active Ingredients 

ternative, approximately 466,000 acres 

, more than 

Action alternative, but fewer than under 

alternatives. In addition, 

tats would be 

mized by prohibiting its use in riparian 

miting the use of broadcast 

management practices would help 

mize the risk that special status fish and aquatic 

would be exposed to herbicides. Risks to 

als from herbicide exposure 

ernative and 

me areas would be lower than 

on Alternative. 

mited number of acres treated and the additional 

ments in and near aquatic 

mit some opportunities for using 

make long-term habitat improvements. 

he associated short-term adverse impacts 

mals would be 

mized in certain areas as well. The degree of effect 

ere herbicide applications were allowed to 

BLM would use manual 

ment methods, or a different type of vegetation 

ment, in place of broadcast treatments in habitats 

ernative, the BLM would not be able to 

mazapic, imazapyr, metsulfuron 

yl, sulfometuron methyl, or any other ALSinhibiting herbicides that are made available in the 

future. Of these, imazapyr is registered for use in 

riparian areas, and the other four herbicides can be used 

in riparian areas, providing no herbicide is allowed to 

enter adjacent water bodies. None of these herbicides 

pose toxicity risks to special status fish or aquatic 

invertebrates during a direct spray into an aquatic 

habitat, even at the maximum application rate. 

Eliminating the use of ALS-inhibitors would reduce the 

BLM’s choices when developing treatment programs, 

and could result in greater risks to special status aquatic 

animals if other more toxic herbicides were used in their 

place. 

Mitigation for Herbicide Treatment Impacts 

The following mitigation is recommended to reduce the 

likelihood of impacts to special status fish and aquatic 

invertebrates from herbicide applications. This 

mitigation should be implemented in addition to the 

SOPs and mitigation designed to protect aquatic animals 

presented earlier in this section. 

• Implement all conservation measures for 

aquatic animals presented in the Vegetation 

Treatments on Bureau of Land Management 

Lands in 17 Western States Programmatic 

Biological Assessment (USDI BLM 2007b). 

• Establish appropriate herbicide-specific buffer 

zones for water bodies that are habitats for fish 

or other aquatic species of interest as shown in 

Table 4-21. 

• At the local level, consider effects to special 

status fish and other aquatic organisms when 

designing treatment programs. 

These practices would help minimize impacts to fish, 

aquatic invertebrates, and aquatic ecosystems on public 

lands to the extent practical. 

Wildlife Resources 

Introduction 

The nearly 261 million acres of public lands sustain an 

abundance and diversity of wildlife resources. Public 

lands provide a permanent or seasonal home for more 

than 2,400 species of amphibians, reptiles, birds, and 

mammals (USDI BLM 2006c). An important activity of 

the BLM is managing vegetation to improve wildlife 

habitat—areas where basic needs such as food,
TABLE 4-20

Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Special Status Fish and 

Aquatic Invertebrates According to Exposure Scenario

BROM1 Appli CHLOR DICAMBA DIFLU DIQUAT DIURON FLUR IMAZ OVER 

cation

Scenario Typ2 Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max 

Direct SprayFish pond L3 L 0 0 0 0 0 0 L H M H 0 M 0 0 0 0 Fish stream M M 0 0 0 0 0 0 M M H H 0 L 0 0 0 0 Aquatic invertebrates pond 0 0 0 0 0 0 0 0 M H M M 0 H 0 0 0 0 Aquatic invertebrates stream 0 L 0 0 0 0 0 0 H H M H 0 L 0 0 0 0 Accidental Spill to PondFish pond NE M NE 0 NE L NE 0 NE H NE H NE M NE 0 NE 0 Aquatic invertebrates pond NE M NE 0 NE M NE 0 NE H NE H NE H NE 0 NE 0 Off-Site DriftFish pond 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Fish stream 0 M 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates pond 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates stream 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Surface RunoffFish pond 0 0 0 0 0 0 0 0 NE NE 0 L NE NE 0 0 0 0 Fish stream 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates pond 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 Aquatic invertebrates stream 0 0 0 0 0 0 0 0 NE NE 0 0 NE NE 0 0 0 0 

1 BROM = Bromacil; CHLOR = Chlorsulfuron; DIFLU = Diflufenzopyr; FLUR = Fluridone; IMAZ = Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; and 2 Typ = Typical application rate; and Max = Maximum application rate.3 Risk categories: 0 = No risk (majority of RQs < most conservative LOC for special status species); L = Low risk (majority of RQs 1-10x most conservative LOC for spe

risk (majority of RQs 10-100x most conservative LOC for special status species); H = High risk (majority of RQs >100 most conservative LOC for special status species)

category is based on the risk level of the majority of risk quotients observed in any of the scenarios for a given exposure group and receptor type. The reader should consu

ERAs (ENSR 2005b-k) to determine the specific scenarios that result in the displayed level of risk for a given receptor group.

BLMVegetationTreatments Using Herbicides 4-97 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-21

Buffer Distances to Minimize Risk to Special Status Fish and Aquatic Organisms from Off-site Drift 

of BLM-evaluated Herbicides from Broadcast and Aerial Treatments 

Application 

Scenario BROM1 CHLR DICA DIFLU DIQT DIUR FLUR IMAZ OVER SULF TEBU 

Minimum Buffer Distance (feet) from Fish and Aquatic Invertebrates

Typical Application Rate 

Aerial NA 0 NA NA NA NA NA 0 NA 0 NA 

Low boom 0 0 0 0 NA 0 NA 0 0 0 0 

High boom 0 0 0 0 NA 100 NA 0 0 0 0 

Maximum Application Rate 

Aerial NA 0 NA NA NA NA NA 0 NA 0 NA 

Low boom 0 0 0 0 NA 100 NA 0 0 0 0 

High boom 0 0 0 0 NA 900 NA 0 0 0 0 

1 BROM = Bromacil; CHLR = Chlorsulfuron; DICA = Dicamba; DIFLU = Diflufenzopyr; DIQT = Diquat; DIUR = Diuron; FLUR = Fluridone; IMAZ = 

Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; and TEBU = Tebuthiuron.

NA = Not applicable. 

Boom height = The Tier I ground application model allows selection of a low (20 inches) or a high (50 inches) boom height.

shelter, water, reproduction, and movement are met.

Plants are an important component of habitat, providing 

food and cover for wildlife. Food is a source of nutrients 

and energy, while good cover prevents the loss of 

energy by providing shelter from extremes in wind and 

temperature. Cover also affords protection from 

predators. The eight ecoregions encompassed by public 

land in the western states support different wildlife 

species and habitats; these characteristics are described

further in Chapter 3. Areas that have been impacted by 

invasive plants may support fewer native wildlife 

species in areas with intact native plant communities. 

Invasive plants can change habitat conditions and vital

ecosystem functions in such a way that some native

species are not able to adapt to the altered ecosystem.

These areas may also support an increased number of 

non-native wildlife species, which compete with native 

wildlife for available resources. 

This section begins with an assessment of risks to

general wildlife, including insects, birds, and small and

large mammals, and is followed by an assessment of 

risks to special status wildlife species. Initial discussion

in this section focuses on the risks to wildlife health 

from the use of herbicides, followed by an assessment

of the risks and benefits to wildlife from treating

vegetation in each ecoregion, followed by an

assessment of impacts to wildlife under each alternative. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Some respondents felt that the BLM should manage for 

biodiversity and identify specific sites that have high

wildlife value. Other respondents wanted the EIS to 

address the habitat requirements of different wildlife

species and the ways in which vegetation treatments 

would influence these habitats. Considering treatment

effects to ground-nesting birds was also mentioned as 

an important issue to consider. Numerous comments

promoted the idea that wildlife habitat improvement

efforts should be directed at restoring habitat and natural

ecological processes. 

The protection of sage-grouse and their habitat was 

advised. It was noted that carefully applied herbicides 

may improve sage-grouse habitat. One respondent noted

that aggressive saltcedar removal efforts in the Mojave

River have killed wildlife in the past. Numerous

comments encouraged the BLM to use this PEIS

process as an opportunity for recovering the full range 

of native species and ecosystems across the western

states, including species such as white-tailed and blacktailed prairie dogs, black-footed ferret, Columbia 

spotted frog, Washington ground squirrel, and wolves. 

Standard Operating Procedures 

Herbicide use poses a potential risk to wildlife. 

However, risk can be minimized by following certain

standard operating procedures, which can be

BLM Vegetation Treatments Using Herbicides 4-98 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

implemented at the local level according to specific 

conditions. The following general procedures, which are 

designed to reduce potential unintended impacts to

wildlife from the application of herbicides in the BLM

vegetation management program, were taken into

consideration when evaluating risks to wildlife from

herbicide use (also see Table 2-8): 

• Use herbicides of low toxicity to wildlife. 

• Use spot applications or low-boom broadcast

applications, where possible, to limit the

probability of contaminating non-target food

and water sources, especially vegetation over

areas larger than the treatment area. 

• Conduct pre-treatment surveys for sensitive 

habitat and special status species within or

adjacent to proposed treatment areas. 

• Use timing restrictions (e.g., do not treat during 

critical wildlife breeding or staging periods) to

minimize impacts to wildlife.

Impacts Assessment Methodology 

The BLM reviewed the literature and findings from 

Ecological Risk Assessments (ERAs) conducted by the 

BLM and Forest Service to assess the impacts to

wildlife from the use of herbicides (ENSR 2005b-k; 

USDA Forest Service 2005). The methods presented 

here provide a brief overview of the ERA process to

determine the risks of herbicide applications to wildlife

species. The ERA methods are presented in detail in 

Appendix C and in the Vegetation Treatments

Programmatic EIS Ecological Risk Assessment

Protocol (ENSR 2004). 

BLM Methodology 

Problem Formulation 

Wildlife receptors, representing different categories of 

terrestrial animal species, were evaluated to determine 

the effects of herbicide exposure in terms of certain

assessment endpoints and associated measures of effect. 

The essential biological requirements for each of these 

groups of organisms are the endpoints to be protected 

from herbicide exposure. These endpoints include

mortality, growth, reproduction, or other ecologicallyimportant sublethal processes. These assessment 

endpoints, for the most part, reflect the direct effects of

an herbicide on these organisms, but indirect effects 

were also considered. Measures of effect are measurable

changes in an attribute of an assessment endpoint (or its 

surrogate, as discussed below) in response to a stressor

to which it is exposed (USEPA 1998a). For the 

screening-level ERA, the quantitative measures of effect

associated with the assessment endpoints generally 

consisted of acute and chronic toxicity data (from

pesticide registration documents and from the available 

scientific literature) for the most appropriate surrogate 

species. 

Exposure Characterization

The BLM uses herbicides in a variety of programs (e.g., 

maintenance of rangeland and recreational sites) with 

several different application methods (e.g., application

by aircraft, vehicle, backpack). In order to assess the 

potential ecological impacts of these herbicide uses to 

terrestrial wildlife, the following exposure scenarios and 

receptor types were considered as routes of the most 

plausible acute and chronic (short- and long-term)

impacts that would occur under a variety of conditions. 

These receptors represent a range of wildlife receptors 

that could be extrapolated to the typical wildlife species 

found on public lands. These receptors also represent

different feeding guilds (herbivore, omnivore, and

carnivore). The exposure scenarios include: 

Direct spray of terrestrial wildlife: 

• Small mammal – 100% absorption 

• Pollinating insect – 100% absorption 

• Small mammal – 1st order dermal absorption 

(absorption occurs over 24 hours, taking into 

consideration the potential for some herbicide 

to not be absorbed) 

Indirect contact with foliage after direct spray: 

• Small mammal – 100% absorption 

• Pollinating insect – 100% absorption 

• Small mammal – 1st order dermal absorption 

Ingestion of food items contaminated by direct spray:

• Small mammalian herbivore – acute and 

chronic exposure 

• Large mammalian herbivore – acute and 

chronic exposure 

• Small avian insectivore – acute and chronic 

exposure 

• Large avian herbivore – acute and chronic

exposure 

BLM Vegetation Treatments Using Herbicides 4-99 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

• Large mammalian carnivore – acute and 

chronic exposure 

Exposure scenarios involving off-site drift, surface 

runoff, and wind erosion were not modeled for

terrestrial wildlife because the direct spray scenarios

were more conservative than scenarios involving wind

erosion or runoff. Risk from consumption of food

would be much greater if the food item was directly

sprayed by an herbicide than if the herbicide drifted or

was carried by water onto the food item. 

Effects Characterization

In the majority of cases, toxicological data do not exist 

for specific wildlife species of concern. Consequently,

toxicological data for surrogate wildlife receptors,

obtained from a literature review, were evaluated and 

used to establish quantitative benchmarks (i.e., toxicity 

reference values for the ecological species of concern). 

Data from acceptable studies were used to compile

statistical endpoints into a matrix for each chemical and 

for each receptor. Data were further subdivided into

acute adverse-effect-levels, chronic adverse-effectlevels, and no-observed-adverse-effect-levels. For each

chemical, receptor, and route of exposure, the lowest

reported herbicide level resulting in an identified acute 

statistical endpoint was selected as the acute TRV. 

Chronic TRVs, based on longer exposure periods and 

associated endpoints such as growth and reproduction, 

were developed, when possible, to provide 

supplementary data to the risk assessment. Before the 

chronic NOAEL TRV was determined, a chronic

lowest-observed-adverse-effect-level was identified,

which was the lowest herbicide level that was found to

cause significant adverse effects in a chronic study.

Once a LOAEL was selected, the chronic NOAEL TRV 

was established as the highest NOAEL value that was 

less than both the LOAEL and the acute TRV. Once 

developed, TRVs were compared with predicted 

environmental concentrations (estimated exposure 

concentrations of the herbicide to evaluate the 

likelihood of adverse effects to ecological receptor). 

Risk Characterization

In order to address potential risks to wildlife receptors 

from exposure to herbicides, RQs were calculated by

dividing the estimated exposure concentration for each

of the previously described scenarios by the appropriate 

herbicide-specific TRV. To facilitate the translation of 

RQs into readily applicable estimates of risk, the

calculated RQs were compared to levels of concern

defined by the USEPA for screening the potential risk

of pesticides. Distinct USEPA LOCs were used for 

acute and chronic risks, and for potential increased risks 

to special status species. The ecological risk 

implications of various exposure estimates can be 

readily determined by noting which RQs exceed the 

corresponding LOCs. 

Forest Service Methodology 

The Forest Service risk assessment methodology was 

similar to that used by the BLM (see SERA [2001a] for

a complete description of the current methodology). The 

steps involved in the Forest Service risk assessments 

were classified as hazard identification (analogous to

BLM problem formulation), exposure assessment, dose 

response assessment (analogous to BLM effects 

characterization), and risk characterization.

Hazard identification involved the review of existing

data with a focus on the dose-response and doseseverity relationships to determine the effect levels (e.g., 

NOAEL, LOAEL) and assessment endpoints (e.g., 

acute toxicity, subchronic or chronic systemic toxic 

effects, reproductive effects) that are most relevant for 

the herbicide risk assessments. 

In the exposure assessment phase, the Forest Service 

developed several general and accidental/incidental

exposure scenarios: direct spray, ingestion of 

contaminated media (via grooming activities,

vegetation, prey species, or water), and indirect contact 

with contaminated vegetation. Actual exposure 

scenarios and receptors depended on the available 

herbicide toxicity data. The Forest Service also used an

allometric approach to model exposure for different

sizes of animals; however, exposure assessments were 

only as specific as the available toxicity data. For 

example, if the hazard identification process suggested 

that large mammals would be more sensitive than small 

mammals, or birds more sensitive than mammals, then

exposure levels were modeled separately. Exposures 

also varied depending on the application method and the

chemical and toxicological properties of the given

herbicide. 

Dose response assessment described the degree or

severity of risk as a function of dose. A dose was 

derived—usually from a series of experimental doses—

that was associated with a negligible, or at least a

defined, level of risk. These dose levels are generally 

referred to as reference values, or more specifically as

“reference doses” (RfDs). To derive the reference value, 

the experimental threshold was divided by an

uncertainty factor used to account for discrepancies 

BLM Vegetation Treatments Using Herbicides 4-100 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

between experimental exposure conditions and the

actual conditions the receptor might experience during 

Forest Service exposure. Often, reference values are 

standard across government agencies. 

The risk characterization process then compared the 

exposure assessment to the dose response assessment to 

develop hazard quotients for risk determination. HQs 

are analogous to the RQs developed in the BLM risk

assessments; they are calculated as the projected level of 

exposure (i.e., EEC) divided by an index of an 

acceptable level of exposure or otherwise defined level

of exposure (e.g., a NOAEL divided by an uncertainty 

factor). In addition, the herbicides were all compared

based on their selectivity, potency, persistence in the 

environment, and ability to move off site. 

Summary of Herbicide Impacts 

While some field studies suggest that appropriate

herbicide use is not likely to directly affect wildlife

(e.g., Cole et al. 1997, Sullivan et al. 1998), there is the

potential for herbicides (used properly or improperly) to

harm wildlife individuals, populations, or species 

(USDA Forest Service 2005). Possible adverse direct

effects to individual animals include death, damage to

vital organs, change in body weight, decrease in healthy

offspring, and increased susceptibility to predation.

Adverse indirect effects include reduction in plant 

species diversity and consequent availability of 

preferred food, habitat, and breeding areas; decrease in

wildlife population densities within the first year 

following application as a result of limited reproduction;

habitat and range disruption (as wildlife may avoid

sprayed areas for several years following treatment),

resulting in changes to territorial boundaries and 

breeding and nesting behaviors; and increase in

predation of small mammals due to loss of ground cover 

(USEPA 1998b). 

In the absence of prominent direct effects, it can be said 

that the main risk to wildlife from herbicide use is 

habitat modification. In forests, for example, herbicide 

use may result in minor and temporary effects on plant

communities and wildlife habitats following single

applications to young stands or stands following 

harvest, including some beneficial effects, but it usually

results in a significant drop in forage the season

following treatment. However, forage species and

wildlife use of treated areas are likely to recover two to

several years after treatment (Escholz et al. 1996;

McNabb 1997; Miller and Miller 2004). 

The extent of direct and indirect impacts to wildlife

would vary by the effectiveness of herbicide treatments 

in controlling target plants and promoting the growth of

native vegetation, as well as by the extent and method

of treatment (e.g., aerial vs. ground) and chemical used

(e.g., toxic vs. non-toxic; selective vs. non-selective), 

the physical features of the terrain (e.g., soil type,

slope), and weather conditions (e.g., wind speed) at the 

time of application. The impacts of herbicide use on

wildlife would depend directly on the sensitivity of each

species to the particular herbicides used, the pathway by

which the individual animal was exposed to the 

herbicide, and indirectly on the degree to which a 

species or individual was positively or negatively 

affected by changes in habitat. Species that reside in an

area year-round and have a small home range (e.g., 

insects, small mammals, territorial birds), would have a 

greater chance of being directly adversely impacted if 

their home range was partially or completely sprayed

because they would have greater exposure to

herbicides―either via direct contact upon application or

indirect contact as a result of touching or ingesting

treated vegetation. 

In addition, species feeding on animals that have been 

exposed to high levels of herbicide would be more 

likely to be impacted, particularly if the herbicide 

bioaccumulates in their systems. Although these 

scenarios were not modeled, wildlife could also

experience greater impacts in systems where herbicide

transport is more likely, such as areas where herbicides 

are aerially sprayed, dry areas with high winds, or areas 

where rainfall is high and soils are porous. Wildlife that

inhabit subsurface areas (e.g., insects, burrowing

mammals) may also be at higher risk if soils are nonporous and herbicides have high soil-residence times. 

The degree of interception by vegetation, which 

depends on site and application characteristics, would 

also affect direct spray impacts. The impacts of 

herbicide use on wildlife would primarily be site- and 

application-specific, and as such, site assessments 

would have to be performed at the field level, using

available impact information, to determine an herbicideuse strategy that would minimize impacts to wildlife, 

particularly in habitat that supports special status 

species. 

The BLM and Forest Service risk assessments

suggested several common impacts of herbicides to 

wildlife. Birds or mammals that eat grass that has been 

sprayed with herbicides have relatively greater risk for 

harm than animals that eat other vegetation or seeds, 

because herbicide residue is higher on grass (Fletcher et

BLM Vegetation Treatments Using Herbicides 4-101 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

al. 1994; Pfleeger et al. 19

apparent with 

risk a

rabbits and h

Forest Service 

herbicide are

exclusively 

For exam

an average h

2005), which would be about the size of the ty

application area (t

would be 400 

of a large ap

treat

chronic consum

also be unlik

dama

spray

and nu

herbicide applications because of the sm

insects and their correspondingly

Impac

Risks fro

foliage after direct spray

contam

existent for

particularl

insects. Speci

herbicide are

figures in Sect

risk info

acco

Table 4-22

typic

to different 

exposure. 

Bromacil 

Direct sp

scenarios in

application rates. This is a 

assum

no degradation or li

predicted low acute and chronic risks to sm

mamm

of food sprayed at the 

acute risk, and

mamm

the ty

chronic risks were p

scenarios inv

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-102 June 2007 

ogrammatic EIS 

96). This phenomenon is 

large mammalian herbivores in the BLM 

ssessments. Grass foragers might include deer, elk, 

ares, chukar, quail, and geese (USDA 

2005). However, harmful doses of 

 not likely unless the animal forages 

within the treatment area for an entire day. 

ple, studies of white-tailed deer have reported 

ome range of about 400 acres (Fowler 

pical 

wo-thirds of herbicide treatments 

acres or less), and less than half the size 

plication area of 1,000 acres (20% of 

ments would be 1,000 acres or larger). Scenarios of 

ption of contaminated vegetation would 

ely if vegetation were to show signs of 

ge (these signs may not occur immediately after 

ing). In addition, insect foragers (e.g., bats, shrews, 

merous bird species) would be at risk from 

all size of 

 large surface area. 

ts of BLM-Evaluated Herbicides 

m direct spray and spills, indirect contact with 

, and ingestion of food items 

inated by direct spray are generally low or non-

 terrestrial fauna, with a few exceptions, 

y for mammalian herbivores and pollinating 

fic risks to wildlife from each individual 

 presented below. See the tables and 

ion 4 of the ERAs for each herbicide for 

rmation on ecological receptor groups 

rding to herbicide application method. Also, see 

, and Appendix C, for a summary of the 

al degree of risk each of the BLM herbicides poses 

receptor categories under different routes of 

ray of a pollinating insect poses a low risk for 

volving the typical and maximum 

conservative scenario that 

es the insect absorbs 100% of the herbicide with 

mitations to uptake. The ERAs 

all 

alian herbivores for scenarios involving ingestion 

maximum application rate. No 

 low chronic risk, was predicted for large 

alian herbivores ingesting vegetation sprayed at 

pical application rate, and moderate acute and 

redicted for similar exposure 

olving the maximum application rate. 

Therefore, direct spray of bromacil at the maximum 

application rate poses a risk to pollinating insects and 

large mammalian herbivores, as well as to small 

mammalian herbivores and large mammalian 

carnivores. Chronic risks to large mammalian 

herbivores are moderate, suggesting that caution is 

needed when applying this herbicide in forage areas, 

although it is unlikely that large mammals would obtain 

food solely within the application area, as assumed by 

ERAs. Because bromacil is a non-selective herbicide 

and is registered for non-cropland uses, it is not likely to 

be used in rangelands or wildlife grazing areas where 

some vegetative cover is desired; this would limit its 

exposure to large mammalian herbivores. If typically 

foraged rangeland plants were protected from off-site 

transport of bromacil, for example by using appropriate 

buffer zones (see Vegetation section in this chapter), 

then large mammalian herbivores would not likely be at 

risk from off-site drift or surface runoff of bromacil 

(these scenarios were not modeled). Risks to birds and 

small mammals under any modeled scenario are 

unlikely. Use of bromacil in spot applications or over 

small areas would be unlikely to adversely impact 

wildlife populations and should have positive effects 

through beneficial habitat modification. 

Chlorsulfuron 

Risk quotients for terrestrial wildlife were all below the 

most conservative LOC of 0.1 (acute endangered 

species), indicating that direct spray of chlorsulfuron is 

not likely to pose a risk to terrestrial animals. Therefore, 

use of chlorsulfuron would primarily affect wildlife 

through habitat modification. Its use in forested 

rangeland and other wildlife habitat areas could benefit 

wildlife over the long term by controlling invasive plant 

species and promoting the establishment and growth of 

native plant species that may provide more suitable 

wildlife habitat and forage. 

Dicamba 

Overdrive® is a formulation of dicamba and 

diflufenzopyr. An analysis of risks to wildlife was 

conducted for dicamba during preparation of the 

Overdrive® ERA. However, an ERA report for dicamba 

was not done by the BLM as part of this PEIS, although 

some information on dicamba is included in the 

Overdrive® ERA. The Forest Service conducted an 

ERA for dicamba, which the reader is encouraged to 

review (available at 

http://www.fs.fed.us/foresthealth/pesticide/risk.shtml). 

 
TABLE 4-22

Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Non Special Status Wildlife According to Ex

BROM1 CHLOR DICAMBA DIFLU DIQUAT DIURON FLUR IMAZ OV

Application Scenario 

Typ2 Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ 

Direct Spray of Terrestrial WildlifeSmall mammal – 100% absorption 03 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pollinating insect – 100% absorption L L 0 0 0 L 0 0 L L L M 0 0 0 0 0 Small mammal – 1st order dermal absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Indirect Contact with Foliage After Direct Spray Small mammal – 100% absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pollinating insect – 100% absorption 0 0 0 0 0 0 0 0 0 0 0 L 0 0 0 0 0 Small mammal – 1st order dermal absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Ingestion of Food Items Contaminated by Direct SpraySmall mammalian herbivore – acute 0 L 0 0 0 0 0 0 0 L 0 L 0 0 0 0 0 Small mammalian herbivore – chronic 0 L 0 0 0 L 0 0 L M L M 0 0 0 0 0 Large mammalian herbivore – acute 0 L 0 0 0 L 0 0 0 M 0 L 0 0 0 0 0 Large mammalian herbivore – chronic L M 0 0 0 L 0 0 L M M H 0 0 0 0 L Small avian insectivore – acute 0 0 0 0 L M 0 0 0 M 0 L 0 0 0 0 0 Small avian insectivore – chronic 0 0 0 0 0 0 0 0 0 M 0 L 0 0 0 0 0 Large avian herbivore – acute 0 0 0 0 0 0 0 0 0 L 0 L 0 0 0 0 0 Large avian herbivore – chronic 0 L 0 0 0 0 0 0 L H 0 M 0 0 0 0 0 Large mammalian carnivore – acute 0 L 0 0 0 0 0 0 0 L 0 0 0 0 0 0 0 Large mammalian carnivore – chronic 0 0 0 0 L L 0 0 0 0 L L 0 0 0 0 0 

1 BROM = Bromacil; CHLOR = Chlorsulfuron; DIFLU = Diflufenzopyr; FLUR = Fluridone; IMAZ = Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; an2 Typ = Typical application rate; and Max = Maximum application rate.3 Risk categories: 0 = No risk (majority of RQs < most conservative LOC for non special status species); L = Low risk (majority of RQs 1-10x most conservative LOC f

Moderate risk (majority of RQs 10-100x most conservative LOC for non special status species); and H = High risk (majority of RQs >100 most conservative LOC for ncategory is based on the risk level of the majority of risk quotients observed in any of the scenarios for a given exposure group and receptor type. The reader should consuERAs (ENSR 2005b-k) to determine the specific scenarios that result in the displayed level of risk for a given receptor group.

BLMVegetationTreatments Using Herbicides 4-103 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

Accidental direct spray at the maximum application rate 

poses low risk to pollinating insects. The ingestion of 

food items contaminated by direct spray of dicamba at

the typical application rate poses a low acute risk to 

small avian insectivores and large mammalian

carnivores. The ingestion of food items contaminated by

direct spray of dicamba at the maximum application rate 

poses a moderate acute risk to the small avian 

insectivores, a low acute and chronic risk to large

mammalian herbivores, and low chronic risk to small

mammalian herbivores. Because dicamba is proposed

for use in rangelands and forestlands and has moderate 

residual activity, insects and wildlife could be at risk

from the application of this chemical, particularly if it is 

sprayed throughout the range area. The use of dicamba

in rangeland could benefit wildlife by controlling 

unpalatable invasive plant species and promoting the 

establishment and growth of native plant species that

may be more suited for forage. 

Diflufenzopyr 

Risk quotients for terrestrial wildlife were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of diflufenzopyr is not likely to pose a risk to

terrestrial animals. Therefore, use of diflufenzopyr 

would primarily affect (positively or negatively) 

wildlife through habitat modification. Its use in forested

rangeland and other wildlife habitat areas would benefit

wildlife by controlling invasive plant species and 

promoting the establishment and growth of native plant 

species that may provide more suitable wildlife habitat 

and forage. Loss of vegetation due to treatments would 

impact wildlife short-term, especially species that use

knapweeds, thistles, and other target vegetation for food

and cover. 

Diquat 

Risk quotients for terrestrial wildlife were above the 

most conservative LOC of 0.1 for several scenarios. 

Accidental direct spray of diquat at the typical and

maximum application rates poses a low risk to

pollinating insects. No risks to small mammals were

predicted due to direct spray or indirect contact with 

foliage. Both of these scenarios conservatively assumed 

100% absorption. 

Risk assessments predicted acute and chronic risks to 

nearly all of the receptor types as a result of ingesting

food items contaminated by direct spray, with the

greatest risk predicted for large mammalian and large

avian herbivores. For large mammalian herbivores, no

acute and low chronic risks and moderate acute and

chronic risks were predicted as a result of ingesting

vegetation sprayed at the typical and maximum 

application rates, respectively. For large avian 

herbivores, no acute and low chronic risks were

predicted for ingestion scenarios involving the typical

application rate, and low acute and high chronic risks 

were predicted for ingestion scenarios involving the 

maximum application rate. In addition, ERAs predicted: 

low chronic risks to small mammalian herbivores for

ingestion scenarios involving the typical application

rate, and low acute and moderate chronic risks for

ingestion scenarios involving the maximum application 

rate; moderate acute and chronic risks for ingestion 

scenarios involving the maximum application rate; and 

low acute risks to large mammalian carnivores for 

ingestion scenarios involving the maximum application 

rate. 

Diuron

Acute RQs for terrestrial wildlife were above the most

conservative LOC of 0.1 for several scenarios. Direct

spray of pollinating insects at the typical and maximum 

application rates poses a low and moderate risk, 

respectively. In addition, low risk was predicted for the

pollinating insect from indirect contact with foliage 

impacted by direct spray at the maximum application

rate. 

Risk assessments predicted acute and/or chronic risks to

all of the receptor types as a result of ingesting food 

items contaminated by direct spray, with the greatest 

risk predicted for large mammalian herbivores

(moderate chronic risk for ingestion of food sprayed at

the typical application rate, and low acute and high

chronic risks for the maximum application rate). In

addition, ERAs predicted: low chronic risks to small 

mammalian herbivores for ingestion scenarios involving

the typical application rate, and low acute and moderate

chronic risks for ingestion scenarios involving the

maximum application rate; low acute and chronic risks 

to small avian insectivores for ingestion scenarios 

involving the maximum application rate; low acute and

moderate chronic risks to large avian herbivores for 

ingestion scenarios involving the maximum application 

rate; and low chronic risks to large mammalian

carnivores for ingestion scenarios involving the typical

and maximum application rates. 

Fluridone 

Risk quotients for terrestrial animals were below the

most conservative LOC of 0.1 for all scenarios. These

results indicate that accidental direct spray or drift of 

BLM Vegetation Treatments Using Herbicides 4-104 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

this aquatic herbicide would be unlikely to pose a risk to

terrestrial wildlife. 

Imazapic

Risk quotients for terrestrial wildlife were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of imazapic is not likely to pose a risk to 

terrestrial animals. Therefore, use of imazapic would 

primarily affect wildlife through habitat modification. 

Its use in forested rangeland and other wildlife habitat 

areas could benefit wildlife by controlling invasive plant 

species and promoting the establishment and growth of 

native plant species that provide more suitable wildlife 

habitat and forage. 

Overdrive®

Most of the RQs for terrestrial wildlife were below the

most conservative LOC of 0.1, indicating that direct 

spray of Overdrive® is not likely to pose a risk to

terrestrial animals. However, there would be low 

chronic risk to large mammalian herbivores as a result

of consuming plants contaminated by direct spray at the 

typical application rate and moderate chronic risk at the

maximum application rate. Because Overdrive® is 

proposed for use in rangeland and wildlife habitat, large 

mammalian herbivores could be particularly at risk from

application of this herbicide, although it is unlikely that 

these large animals would do all of their foraging within 

or immediately adjacent to application areas. The use of

Overdrive® would primarily affect (positively or

negatively) wildlife through habitat modification. Its use 

in wildlife habitat areas could benefit most wildlife by

controlling invasive plant species and promoting the 

establishment and growth of native plant species that

provide more suitable wildlife habitat and forage. 

Sulfometuron Methyl 

Risk quotients for terrestrial wildlife were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of sulfometuron methyl is not likely to pose a risk 

to terrestrial animals. Because this herbicide is relatively

non-selective, it is not likely to be used in wildlife 

habitat areas, and therefore, should result in few 

negative or positive impacts on wildlife. Long-term

positive impacts could result if sulfometuron methyl

was used to clear former wildlife grazing habitat of an

aggressive invasive, such as downy brome, and native 

forage was able to reestablish once this area was 

cleared. 

Tebuthiuron 

Risk quotients for pollinating insects were above the

most conservative LOC of 0.1 for direct spray of insects 

(low risk at the typical and maximum application rates) 

and indirect contact with foliage after direct spray (low

risk at the maximum application rate). 

The ingestion of food items contaminated by direct

spray at the maximum application rate poses a risk to

mammalian herbivores. Low acute risk and chronic risk

were predicted for the small and large mammalian

herbivores. The strength of this herbicide is its use as a 

habitat modifier in the BLM shrub reduction program. It

is relatively non-selective, but tends to harm grasses that

are present. At low rates of application, tebuthiuron is 

used to thin shrubs, creating a more favorable habitat for 

shrub-dependent species. Because this application often 

takes place on land with a low concentration of grass 

forage, risks to mammalian herbivores associated with

its use might be lower than those predicted under the 

ingestion scenarios, and wildlife forage and habitat 

could be enhanced by these applications. Birds and

mammalian carnivores should not be adversely

impacted by direct spray of tebuthiuron under any 

application scenarios. 

Impacts of Forest Service-evaluated Herbicides

The following information for eight herbicides proposed

for use by the BLM is taken from ERAs prepared by the 

Forest Service to support assessment of the 

environmental consequences of using these herbicides 

in Forest Service vegetation management programs. As 

part of these ERAs, the Forest Service developed

worksheets (see USDA Forest Service 2005) that

allowed the BLM to assess risks for BLM typical and

maximum application rates and LOCs, rather than the 

Forest Service rates and LOCs. Thus, the risk

assessment process for the Forest Service-evaluated 

herbicides parallels the BLM process as much as

possible. However, some Forest Service modeled risk

scenarios for terrestrial animals may be different than 

those used in the BLM ERAs, depending on the 

specificity of available toxicity data. The assessment of 

impacts is presented below using the Forest Service 

upper estimates of hazard quotients to maximize the 

conservatism of the assessment. In addition, it should be 

noted that the development of HQs by the Forest

Service, as well as the BLM, is already conservative for 

many reasons (e.g., assumption of 100% dermal

absorption, assumption that 100% of diet is 

contaminated, use of most sensitive values for exposure

and dose/response assessments). Risks to TEP species

BLM Vegetation Treatments Using Herbicides 4-105 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

are speci

acco

2,4-D 

2,4-D poses 

direct spray

scenarios (

2,4-D at

poses a 

assum

mammal

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-106 June 2007 

ogrammatic EIS 

fically analyzed in the Biological Assessment 

mpanying this document (USDI BLM 2007b). 

a risk to some terrestrial wildlife under 

 as well as ingestion of contaminated food 

Table 4-23; SERA 1998). Direct spray of 

 both the typical and maximum application rates 

moderate risk to insects and small mammals, 

ing 100% absorption of the herbicide. Small 

s face low risk from direct spray if 1st order 

dermal absorption is assumed. In addition, mammals 

and large birds would be at risk from the consumption 

of vegetation contaminated by 2,4-D at the application 

site: large mammals and large birds would be at 

moderate acute and chronic risk for ingestion scenarios 

involving both the typical and maximum application 

rates (large birds face high acute risk for ingestion 

scenarios involving the maximum application rate), and 

small mammals face low acute risk for ingestion 

scenarios involving the typical and maximum 

application rates. Long-term consumption of 

contaminated vegetation would be unlikely if the 

vegetation were to show signs of damage. In other acute 

scenarios, small mammals face low risk from 

consumption of water contaminated by an accidental 

spill; small mammals face moderate to high risk and 

small birds face high risk from the consumption of 

contaminated insects; predatory birds face high risk 

from the consumption of fish contaminated by a spill; 

and carnivorous mammals and birds face low risk from 

the consumption of small mammals contaminated by 

direct spray of 2,4-D. The risk assessment indicates that 

insectivores and large herbivores eating large quantities 

of grass and other vegetation are at risk from routine 

exposure to 2,4-D, suggesting that 2,4-D should not be 

applied over large application areas where foragers 

would only consume contaminated food. 

Clopyralid 

According to the Forest Service risk assessment (SERA 

2004b), clopyralid is not likely to pose a risk to 

terrestrial animals; however there are several scenarios 

under which there would be low acute risk to a variety 

of receptors at the typical and maximum application 

rates (Table 4-23). For the typical application rate, small 

mammals are at risk from 100% absorption of direct 

spray and consumption of contaminated insects and 

vegetation. For the maximum application rate, insects 

are at risk from direct spray, large birds are at risk from 

the consumption of contaminated vegetation, and small 

birds face risk from the consumption of contaminated 

insects. Application of clopyralid at the maximum 

application rate also poses a low chronic risk to large 

mammals and large birds consuming on-site 

contaminated vegetation. The Forest Service asserts that 

use of clopyralid in Forest Service programs is not 

likely to result in adverse effects to terrestrial animals; 

risks identified all fall within the lowest risk category. 

Glyphosate 

Glyphosate applications pose low to moderate risk to 

several terrestrial wildlife receptors under multiple 

exposure scenarios involving applications at the typical 

and maximum application rates (Table 4-23; SERA 

2003a). Direct spray of a small animal and an insect, 

both assuming 100% absorption, poses a low risk at the 

typical application rate and a moderate risk at the 

maximum application rate. Consumption of vegetation 

contaminated by a spill poses a low risk to small 

mammals for scenarios involving for the maximum 

application rate only. A large mammal consuming 

contaminated vegetation would face low acute risk for 

scenarios involving the typical application rate, 

moderate acute risk, for scenarios involving the 

maximum application rate, and low chronic risk for 

scenarios involving the maximum application rate; a 

large bird consuming contaminated vegetation would 

face a low acute and chronic risk. Consumption of 

contaminated insects would pose a low risk to both 

small mammals and small birds if the herbicide was 

applied at the typical application rate. The herbicide 

would pose a moderate risk if applied at the maximum 

rate. Acute risks from glyphosate exposure are low at 

the typical application rate under all scenarios, and there 

are no chronic risks. Exposure scenarios with the 

greatest risk are direct spray and acute consumption of 

contaminated vegetation and insects. Glyphosate is nonselective, suggesting that spot applications in rangeland 

and wildlife habitat areas would be the most appropriate 

use of this herbicide. Spot applications would have 

lower risks associated with consumption of 

contaminated vegetation and insects than broadcast 

applications, as fewer non-target areas would be 

impacted by direct spray or spray drift. 

Hexazinone 

Several exposure scenarios involving application of 

hexazinone would pose a low to moderate risk to 

wildlife receptors (Table 4-23; SERA 1997). Small 

mammals would face low risk if directly sprayed at the 

maximum application rate, assuming 1st order dermal 

absorption, and low to moderate risk assuming 100% 

dermal absorption. Similarly, 100% absorption of direct 
TABLE 4-23

Ris

k Categories

1 Use

d to Describe Forest Service-evaluated Herbici

de Effects o

n Wildlife According to Exposu

 2,4-D Clopyralid 

Glyphosate2 Hexazinone Imazapyr Metsulfuron 

 Typ3 Max Typ Max Typ Max Typ Max Typ Max Typ Max 

Acute/Accidental Exposures Direct spray, s

mall ma

m

mal, 1st order absorption 

L4 L 0 0 0 0 0 L 0 0 0 0 

Direct spray, s

mall ani

mal, 100% absorption M M L L L M L M 0 L 0 L 

Direct spray, bee, 100% absorption M M 0 L L M L M 0 L 0 0 Consu

mption of conta

minated fruit, s

mall 

mammal L L 0 0 0 L 0 L 0 0 0 0 

Consu

mption of conta

minated grass, large mammal M M L L L M L M 0 L 0 L 

Consu

mption of conta

minated grass, large bird M H 0 L L L L M 0 L 0 0 

Consu

mption of conta

minated water, s

mall 

mammal, spill L L 0 0 0 L 0 L 0 0 0 0 

Consu

mption of conta

minated 

water, small mammal, strea

m 0 0 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated insects, s

mall mammal M H L L L M 0 0 0 L 0 L 

Consu

mption of conta

minated insects, s

mall bird H H 0 L L M M M L L 0 0 

Consu

mption of conta

minated s

mall mammal, predatory 

ma

m

mal L L 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated small mammal, predatory bird L L 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated fish, predatory bird, spill H H 0 0 0 0 L M 0 0 0 0 

Chronic Exposures Consu

mption of conta

minated vegetation, s

mall 

mammal, onsite 0 0 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated vegetation, small mammal, offsite 0 0 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated vegetation, large mammal, onsite M M 0 L 0 L L M 0 0 0 0 

Consu

mption of conta

minated vegetation, large

mammal, off -

site 0 0 0 0 0 0 0 0 0 0 0 0 Consu

mption of conta

minated vegetation, large bird, on-site M M 0 L 0 L L M 0 0 0 0 

Consu

mption of conta

minated vegetation, large bird, off-site 0 0 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated water, s

mall 

mammal 0 0 0 0 0 0 0 0 0 0 0 0 

Consu

mption of conta

minated fish, predatory bird 0 0 0 0 0 0 0 0 0 0 0 0 

1 Risk categories are based on upper esti

mates of hazard quotients and the BLM LOCs of 0.1 for acute scenarios and 1.0 for chronic scenarios. The reader should cons

individual Forest Service risk assess

ments to evaluate risks at central esti

mates of hazard quotients. 

2 Risk categories are the sa

me for both evaluated formulations. 3 Typ = Typical application rate; and Max = 

maxi

mum application rate. 4 Risk categories: 0 = No risk (HQ < LOC); L = Low risk (HQ = 1 to 10 x LOC); M = Moderate risk (HQ = 10 to 100 x LO

C); and H = High risk (HQ > 100 LOC). 

BLM Vegetation Treatments Using Herbicides 4-107 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

spray by insects would pose a low to moderate risk. 

Acute consumption of contaminated vegetation would

pose a low risk to the small mammal for treatments at

the maximum application rate. Acute and chronic

consumption of contaminated vegetation would pose a 

moderate risk to both large mammals and large birds. 

Acute consumption of contaminated insects would pose 

a moderate risk to small birds, and acute consumption

of contaminated fish would pose a low to moderate risk

to predatory birds. Also, acute consumption of 

contaminated water would pose a low risk to small

mammals for scenarios involving a spill at the

maximum application rate. It appears that wildlife, 

especially sensitive species, are at risk from the

application of hexazinone; the effects of hexazinone on

insects, birds, and soil microarthropods are less certain

than the effects on mammals. If food and water sources 

were not contaminated, risks would be reduced. 

Contamination of food and water sources could be 

minimized by utilizing spot applications at the typical

application rate. Because hexazinone is semi-selective, 

is used to control woody species, and is typically only 

applied in spot applications, risks to wildlife under 

normal application could be lower than those predicted

by the risk assessment. 

Imazapyr

Imazapyr does not pose substantial risks to terrestrial

animal species, but there are low risks associated with

several exposure scenarios, mostly involving herbicide 

applications at the maximum application rate (Table 4-

23; SERA 2004d). The only scenario involving the

typical application rate that would pose a risk (low risk) 

to wildlife is that of a small bird consuming 

contaminated insects. Therefore, application of

imazapyr at the typical application rate is not likely to 

result in adverse effects to terrestrial animals, with the 

possible exception of small insectivorous bird. For the 

maximum application rate, however, the following 

scenarios pose a low risk to wildlife receptors: direct 

spray of small animals and insects, consumption of 

contaminated vegetation by large mammals and large 

birds, and consumption of contaminated insects by 

small mammals and small birds. The HQs for terrestrial

invertebrates are based on a single study using mortality 

as the endpoint, so results for this receptor are less 

certain. Because imazapyr is primarily used for the 

management of saltcedar in riparian zones and is 

relatively costly to use in the management of upland

vegetation, large-scale impacts to wildlife are unlikely, 

even at the maximum application rate. Wildlife that 

reside mostly within the riparian zone would be most at 

risk from application of imazapyr. 

Metsulfuron Methyl 

None of the HQs estimated for metsulfuron methyl

exposure at the typical application rate indicate risk to 

any of the receptors (Table 4-23; SERA 2004e). For 

applications at the maximum application rate, 

metsulfuron methyl would pose a low risk to small

animals via 100% absorption of direct spray and

consumption of contaminated insects, and to large 

mammals via consumption of contaminated vegetation. 

Application of metsulfuron methyl at the typical 

application rate should not result in any adverse effects 

to terrestrial animals. 

Picloram 

Most of the HQs for the evaluated scenarios of picloram

exposure were below the LOC for both the typical and

maximum application rates (Table 4-23; SERA 2003b). 

Under three scenarios, low risk was predicted for 

applications at the typical application rate: 100% 

absorption of direct spray by small animals, acute 

consumption of contaminated vegetation by large 

mammals, and acute consumption of contaminated 

insects by small mammals. For the maximum 

application rate, risk was somewhat elevated for these

three scenarios (low to moderate risk), and two

additional scenarios posed low risk: 100% absorption of 

direct spray by insects and chronic consumption of onsite contaminated vegetation by the large bird. 

Therefore, picloram applications at the typical rate

would potentially have few adverse effects on terrestrial

animals. 

Triclopyr 

Application of the two evaluated formulations of

triclopyr, triclopyr acid and triclopyr butoxyethyl ester 

(BEE), poses a risk to insects, mammals, and birds 

under several exposure scenarios (Table 4-23; SERA

2003c). Because risks calculated for these two formulas 

are the same, no differentiation will be made between

triclopyr acid and triclopyr BEE in this section. The 

following scenarios pose a low risk for applications at

the typical rate and a moderate risk for applications at

the maximum rate: first-order and 100% absorption of 

direct spray by small mammals, 100% absorption of

direct spray by insects, acute consumption of 

contaminated vegetation by large mammals and large 

birds, acute consumption of contaminated insects by 

small birds and small mammals, and chronic 

BLM Vegetation Treatments Using Herbicides 4-108 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

consumption of on-site contaminated vegetation by

large mammals and large birds. In addition, for the 

maximum application rate, there would be low risk 

associated with acute consumption of contaminated

vegetation by small mammals following an accidental 

spill, acute consumption of contaminated small

mammals by carnivorous mammals, and chronic 

consumption of off-site contaminated vegetation by

large mammals. No risk is predicted for small mammals 

as a result of acute or chronic consumption of

contaminated vegetation or water, or for predatory birds 

as a result of consumption of contaminated fish. In

summary, acute or accidental direct spray scenarios

would pose a low to moderate risk to terrestrial 

mammals and insects, consumption of contaminated

vegetation would pose a low to moderate risk to large 

mammals and large birds, and consumption of 

contaminated insects would pose a low to moderate risk

to small birds. 

Impacts of Other Herbicides Currently Available for 

Use 

2,4-DP, asulam, atrazine, fosamine, mefluidide methyl, 

and simazine were approved for use in the earlier BLM

EISs. 2,4-DP could be used in forested rangeland. It has 

low toxicity to mammals and is practically non-toxic to

waterfowl and upland game birds. Asulam is of low

toxicity to birds and mammals, and would primarily be

used to control brackenfern on forested rangelands 

(Information Ventures, Inc. 1995a). Atrazine could be

used for vegetation treatments in conifer plantations, but

would not be used in forestlands or other rangelands. It 

is slightly toxic to non-toxic in birds, and is slightly to

moderately toxic to mammals (Information Ventures, 

Inc. 1995b; Extension Toxicology Network 1996e). 

Fosamine is practically nontoxic to insects, birds, and

mammals, although some chronic reproductive effects 

have been noted in mallards (USEPA 1995d). 

Mefluidide is of low to moderate toxicity to birds and

mammals (Information Ventures, Inc. 1995c). Simazine 

could be used by the BLM on Christmas tree 

plantations, but would likely not be used on rangeland. 

Simazine is almost non-toxic to birds and mammals, 

although sheep and cattle are more sensitive to simazine

than other mammals, and a dose as low as 500 mg/kg 

can be fatal (Information Ventures, Inc. 1995d). The 

BLM has not used any of these herbicides, except 

fosamine (< 50 acres annually), since 1997, and does 

not plan to utilize them in the near future. 

Impacts of Herbicide Treatments on

Wildlife and Habitat by Ecoregion 

Tundra and Subarctic 

Herbicides have not been used on public lands in Alaska

on Arctic tundra or in subarctic forests, and herbicide 

treatments have not been proposed for these regions. 

Use of herbicides in these habitats is discouraged 

because forbs valuable to many tundra and boreal forest

wildlife species would be reduced substantially (Braun

1980). 

Temperate Desert 

The goal of most treatments in this ecoregion is to

restore lands damaged by fires in the Great Basin, and 

to benefit sage-grouse and other wildlife that use 

sagebrush communities. In particular, efforts would be

focused on improving existing sagebrush stands and

replacing invasive annual grasses with native 

bunchgrasses and forbs (USDA Forest Service and

USDI BLM 2000). Although few wildlife vertebrates 

are endemic to the sagebrush analysis region, the Great

Basin provides habitat for about 100 bird, 70 mammal, 

and 23 amphibian and reptile species (USDI BLM 

1999). 

At low to mid-elevations, long fire intervals have

created climax sagebrush communities that are found 

on large areas of public land. These communities have

diminished perennial herbaceous understory as a result

of grazing and other habitat disturbances and 

competition from sagebrush plants. Where perennial 

species have been lost, downy brome has replaced

these grasses, to the detriment of wildlife habitat

(Perryman et al. 2003). As downy brome and other 

annual grasses have replaced native sagebrush and 

other shrubs in the region, populations of mule deer, 

pronghorn, bighorn sheep, Columbian sharp-tailed

grouse, sage-grouse, and several species of raptors 

have declined due to loss of habitat and prey species 

that depend on shrub habitat (USDI BLM 1999). 

Vegetation treatments that promote a mixed sagebrushgrass-forb community benefit wildlife. Habitat in these 

communities is improved by creating openings in 

dense and crowded sagebrush and rabbitbrush stands, 

removing invasive species, and promoting production

of perennial grasses and forbs (Paige and Ritter 1999, 

USDI BLM 1999, Sage Grouse Conservation Planning 

Team 2001). 

BLM Vegetation Treatments Using Herbicides 4-109 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Treatments can improve habitat structure, complexity, 

and layering to the benefit of species that rely on a 

diversity of plant types and cover to meet their daily 

needs. Several studies have shown that densities of 

songbirds and small mammals are greater in mixed 

communities than in pure sagebrush or grassland

stands (USDI BLM 1991a). 

Sagebrush rangelands are often treated with herbicides 

to increase herbaceous plants, with herbicides that

remove broad-leaved plants without harming grasses 

being the most widely used. As noted in the Vegetation 

section, 2,4-D, glyphosate, picloram, and tebuthiuron 

are important herbicides for control of sagebrush, 

rabbitbrush, and other woody species. Olson et al. 

(1994) used low rates of tebuthiuron to thin big

sagebrush stands and enhance wildlife habitat in

Wyoming. Glyphosate can be applied to sagebrush in 

winter months to kill only sagebrush above the snow. 

Other studies have shown, however, that nesting and

brood-rearing habitat for sage-grouse and other birds 

can be depleted by spraying. In Wyoming, it can take 

sagebrush 14 to 17 years to recover from herbicide 

spraying (see review in Connelly et al. 2000). Past

efforts to reduce sagebrush habitat has been implicated

as contributing to the decline in sage-grouse breeding

populations throughout the West, especially if the 

treated area was reseeded with crested wheatgrass 

(Robinson and Bolen 1989; see review in Connelly et

al. 2000). Herbicide use may also cause sage-grouse 

emigration from an area and reduce the suitability of an

area for broods and wintering sage-grouse (see review 

in Connelly et al. 2000). Braun et al. (1977) 

recommended that sagebrush control not occur within a 

2-mile radius of sage-grouse leks, nesting areas,

wintering grounds, or breeding grounds. However, 

Urness (1979) believed that herbicides could be used to

prevent shrub invasion onto leks and alter the size and

density of sagebrush to more closely approximate

nesting requirements. Dahlgren et al. (2006) treated

mountain big sagebrush stands with tebuthiuron to 

reduce canopy cover and increase production of forbs. 

Sage-grouse adults and their young preferred the 

treated plots over the untreated plots, although most use 

of treated plots occurred near the boundary of the 

treated plots and intact sagebrush areas. The authors 

suggested that low rates of tebuthiuron be used to

ensure that only a portion of the treated sagebrush was 

killed. 

Herbicidal control of sagebrush can reduce populations 

of some birds, such as Brewer’s sparrow and vesper

sparrow, and can reduce the production of forbs and

seeds that are important to nesting birds and their 

young for food and cover. Thus, sagebrush treatments 

must be carefully designed to ensure that large stands 

of sagebrush are not lost. 

Herbicide treatments and fire use may be the only 

effective ways to control large areas of annual weeds 

and other invasive vegetation in this ecoregion. For 

smaller areas, however, mechanical treatments are

recommended over herbicides for improving sagegrouse habitat. Mechanical methods often do less 

damage to the understory and are more effective than

herbicides for sagebrush habitat improvement (USDI 

BLM 1991a). 

Response by mammals varies with herbicide treatment. 

Deer mice seem unaffected, northern pocket gophers

and least chipmunks can decrease, American badgers 

might decrease initially should gophers or ground 

squirrels be affected negatively, and montane voles 

usually increase (Cooperrider et al. 1986; Payne and 

Bryant 1998). Once preferred forbs return to an area, 

small mammals apparently return to pretreatment

levels. 

Elk benefit from conversion of sagebrush to 

bunchgrass-dominated sites. Elk use increased 89% on 

chemically treated versus untreated sites in Wyoming

(Wilbert 1963, Severson and Medina 1983). Mule deer 

used sagebrush less in Colorado after it was sprayed 

with 2,4-D. Loss of forbs associated with herbicide

treatments of sagebrush stands can be detrimental to

white-tailed deer, as forbs can comprise 60% or more of

the deer’s diet (Robinson and Bolen 1989). 

Pronghorns rely heavily upon browse diets during fall

and winter, but forbs are important in spring and 

summer. Herbicide treatments that thin dense stands of 

tall sagebrush and improve forb and grass understories 

can benefit pronghorns (Urness 1979). 

In general, treating large units of sagebrush with

herbicides is not recommended for wildlife habitat 

management. If treatments are done in patches or strips, 

important refuge areas can be created for amphibians, 

reptiles, birds, and small mammals (Payne and Bryant

1998); staggering treatments over several years can

achieve the same effect. Howard and Wolfe (1976) 

recommended patterned treatments of small tracts,

instead of large tracts, for species such as ferruginous 

hawks because such treatments improve the prey base.

Leaving strips of untreated vegetation between strips of

treated vegetation also affords wildlife the opportunity 

to find food and cover resources while treated stands 

recover. Spraying areas with over 39% big sagebrush

cover can benefit sage-grouse as long as treatments are 

BLM Vegetation Treatments Using Herbicides 4-110 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

in small blocks, strips, or patches (Holecheck et al.

1989). Spraying should be conducted before forbs 

emerge. Little benefit from any habitat modification can 

be expected unless livestock grazing is closely regulated 

after treatment (Payne and Bryant 1998). 

Subtropical Desert

Herbicides such as 2,4-D, picloram, tebuthiuron, and 

dicamba are used to control woody species such as 

mesquite, creosotebush, and snakeweed in Subtropical

Desert habitats. Mesquite has invaded millions of acres 

of shortgrass and mixed-grass prairies of the Southwest. 

The invasion of woody species has occurred at the 

expense of native grassland species, and has reduced the 

carrying capacity for species that depend upon

shortgrass and mixed-grass prairies. In Texas, woody 

shrubs infest over 80% of the state’s rangelands 

(Robinson and Bolen 1989). Brush removal may help to 

conserve water when the foliage of the moisturedemanding brush is removed. However, in some areas,

the expanded range of mesquite has increased the 

distribution and abundance of white-tailed deer, doves, 

quail, and cottontail (McCormick 1975 cited in USDI

BLM 1991a).

Where dense canopies are a problem, treatment with

triclopyr and clopyralid might be needed to thin woody

vegetation. Stem application of triclopyr is a desirable 

method of mesquite control because it promotes quick

removal of mesquite with minimal damage to native

plants and wildlife (Waggoner et al. 2003). In general, 

no more than 60% of a mesquite-dominated habitat 

should be treated, and treatments should be in strips or

as a patchwork of openings. Germano (1978 cited in

USDI BLM 1991a) observed that jackrabbits, antelope, 

quail, and lizards favored openings in mesquite stands. 

Except for northern mockingbirds and golden-fronted

woodpeckers, most nongame birds in northern Texas 

were unaffected by herbicide-treated areas designed to 

improve habitat for mourning doves and northern 

bobwhite, as long as stems and dead trees were left

standing. Total density of nongame birds increased 54% 

on managed versus unmanaged sites; species diversity 

and richness were similar (Payne and Bryant 1998). 

Where soil is disturbed in the fall by disking to promote 

forbs and grasses, herbicides such as diuron and 2,4-D 

can be cost-effective to enhance production of foods for 

northern bobwhite and mourning doves. 

As long as cover is maintained, white-tailed deer appear 

to adapt to reduction in browse species associated with

herbicide treatments of mesquite. Spraying large blocks 

of cover habitat adversely affects deer, but treating

woodlands in alternating bands can benefit deer (USDI 

BLM 1991a, Payne and Bryant 1998). Herbicide 

treatments of upland habitat should be acceptable for 

most wildlife as long as 20% of an area is left as old, 

mature woodland. 

Herbicides have also been targeted for plants such as 

burroweed, creosote bush, American tarwort, tree 

cholla, yucca, and pricklypear. In creosote bush

communities, tebuthiuron treatments were more 

effective than mechanical treatments in killing these

plants, but changes in grass and forb densities were the

same whether creosote bush was chemically or 

mechanically treated (Morton and Melgoza 1991). In

Arizona, Smith (1984 cited in USDI BLM 1991a) 

compared bird use in creosote bush treated with 

tebuthiuron and found that birds used openings created 

through treatment for nesting and foraging sites. After 3 

years, rodent abundance was 71% higher on creosote 

bush areas treated with tebuthiuron than control plots in

southeastern Arizona (Standley and Smith 1988). 

Cautious and guarded use of herbicides in hot desert 

communities is recommended. Aside from the

semidesert grasslands, herbicides probably have limited

value, particularly in the Sonoran and Mojave deserts. 

Plant control by chemical means usually must be

followed by revegetation, which may be unsuccessful

due to low and erratic precipitation. In addition, because

of the sparse vegetation over much of the desert, 

removal of vegetation can have substantial impacts on

native wildlife that rely on affected plants for food and

cover and that cannot readily find new habitat (Payne 

and Bryant 1998). 

Temperate Steppe 

The BLM administers between 10 and 15 million acres

of short- and mixed-grass prairie grasslands that support

over 130 species of wildlife, including lesser prairie 

chicken, mountain plovers, and prairie dogs. Over threequarters of treatments in the Temperate Steppe

Ecoregion would be focused on annual and perennial 

grasses and forbs, including downy brome, leafy spurge, 

and several species of knapweeds and thistles. Much of 

this work would be done in support of the BLM’s 

Conservation of Prairie Grasslands initiative. 

Control of broadleaf plants by selective herbicides, such 

as 2,4-D, usually increases grass production. 2,4-D is

also effective in controlling weedy forbs, such as bull,

musk, and Scotch thistle. 2,4-D can be tank mixed with

other herbicides, such as glyphosate, dicamba, picloram, 

and triclopyr to enhance the activity of these herbicides. 

BLM Vegetation Treatments Using Herbicides 4-111 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Applications of picloram may damage sensitive grasses 

as well as broadleaf plants, and can substantially alter 

the composition of grassland communities and affect

wildlife diets (USDI BLM 1991a). For example,

Fagerstone et al. (1977) found that the prairie dog diet

changed significantly from forbs to grass after their

habitat was treated with 2,4-D, which significantly 

reduced the abundance of forbs on the site. Despite the 

diet change, the 2,4-D treatment appeared to have little

detrimental effect on prairie dogs. 

Leafy spurge can be controlled with picloram, dicamba, 

and glyphosate (Hickman et a1. 1990). Grasshopper 

sparrow and savannah sparrow densities were lower in

areas with high densities of leafy spurge in North

Dakota (Scheiman et al. 2003). Because forbs and other 

broadleaved plants are important to many wildlife 

species, patchwork treatments of herbicides should be 

applied when treating large areas of leafy spurge. 

Prairie threeawn is an herbaceous invader on degraded,

tallgrass prairie range sites; it colonizes bare soil and

maintains dominance for many years, and its value to 

wildlife is minimal. Atrazine effectively controls

prairie threeawn (Engle et al. 1990). 

Picloram, clopyralid, and a mixture of 2,4-D and 

clopyralid were used to treat spotted knapweed to 

enhance elk forage production in Montana (Rice et al. 

1997b). Herbicide application increased winter elk 

forage by 47% at sites with low to moderate spotted

knapweed infestations. However, success would be 

greatest at sites having a significant bunchgrass 

component prior to treatment. 

Herbicide treatments have also been used to reduce the

cover of woody shrubs, such as mesquite and Eastern

redcedar, which encroach upon prairie grasslands. 

While these woody species can benefit some wildlife 

species (see Wildlife Resources section in Chapter 3),

they can also crowd out grassland and forb species,

reducing the value of habitat for some species (Engle et

al. 1987; Payne and Bryant 1998). Woody shrubs can be 

controlled where canopy cover reduces the amount of 

understory vegetation used for food and cover. Picloram 

and tebuthiuron are effective in controlling woody 

shrubs. 

Herbicides such as 2,4-D have been used in evergreen 

and deciduous forests at higher elevations to thin 

sagebrush, snowbrush ceanothus, chokecherry, 

snowberry, and other shrubs (Vallentine 1989). After 

treatment, plants often resprout from the crown, 

producing palatable forage. Whisenant (1987) 

successfully treated big sagebrush with clopyralid, 

leaving bitterbrush and serviceberry relatively

unharmed. Treating bitterbrush areas with 2,4-D in

Idaho resulted in plants that were unharmed or only

slightly damaged (Vallentine 1989). Damage to 

bitterbrush can be reduced if an area targeted for 

sagebrush control is treated early, before bitterbrush

twigs elongate or began to flower (Payne and Bryant

1998). Bitterbrush plants less than 12 inches tall and

those that are flowering will be severely damaged or 

killed by 2,4-D. 

Subtropical Steppe Ecoregion 

Over three-quarters of treatments in the Subtropical 

Steppe Ecoregion would be focused on sagebrush and

other evergreen shrublands, while 12% would focus on 

pinyon, juniper, and other evergreen woodland species. 

Healthy pinyon-juniper woodlands, with a full 

complement of understory grasses, forbs, and shrubs, 

provide excellent wildlife habitat. However, in many

areas, pinyon and juniper have increased in density to

the point that understory vegetation is excluded, to the 

detriment of wildlife (USDA Forest Service and USDI 

BLM 2000). 

Broad-scale herbicide use in pinyon-juniper woodlands 

has not been popular over the past several decades, 

especially when used to open up pinyon-juniper stands. 

The possibility of destroying midstory shrubs that are

important food sources is a major disadvantage to 

herbicide use (Payne and Bryant 1998 

Picloram and tebuthiuron are the main herbicides used 

to treat pinyon-juniper woodlands. Both picloram and

tebuthiuron may persist in the soil for several years and

may injure understory grasses, shrubs, and forbs. 

Individual tree treatments with these herbicides are

often more effective in controlling trees and less 

injurious to understory species than broadcast 

applications. Using picloram on some sites can also 

result in dominance by annual grasses, such as downy 

brome or medusahead, if these species become resistant

to picloram (USDI BLM 1991a). 

Studies of wildlife use of treated pinyon-juniper habitats 

have shown that mule deer use was greater in a 

chemically treated plot than on a mechanically treated

plot because herbicide treatment resulted in more

openings in the woodlands and a greater retention of 

screening cover (Severson and Medina 1983). If used

properly, aerial broadcasts can create numerous, small,

irregularly-shaped openings in terrain that is too rough 

for mechanical operations (Short and McCulloch 1977). 

BLM Vegetation Treatments Using Herbicides 4-112 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Herbicides can be used with mechanical treatment to 

manipulate pinyon and juniper (Evans et a1. 1975). 

Small trees that escape chaining, cabling, or dozing can 

be treated effectively with picloram to ensure that the

opening created is free of trees. Unwanted invaders of 

mechanically prepared openings, including downy 

brome, can be controlled with atrazine or glyphosate. 

Glyphosate can be used to desiccate leaves or needles, 

rendering them more susceptible to prescribed burning. 

Tebuthiuron has been used to control sand shinnery oak

to improve habitat for lesser prairie chickens in areas 

where it forms a dense canopy cover. In a study in

Oklahoma, tebuthiuron effectively controlled sand

shinnery oak and increased grass production, yet did 

not reduce the abundance and diversity of forbs

required by lesser prairie chickens (Doerr and Guthery 

1983). 

Mediterranean and Marine Ecoregions 

Approximately 11,000 acres would be treated annually

using herbicides in the Marine and Mediterranean 

ecoregions under the proposed action, primarily using

ground-based methods. Over three-quarters of 

treatments in the Mediterranean and Marine ecoregions 

would occur in evergreen forestlands. Many of these 

efforts would be focused on integrated weed 

management and forest health. The objectives of forest

health treatments would be to stem the decline in oldforest habitats primarily due to fire exclusion, to restore 

more natural fire regimes and reduce hazardous fuels to

reduce the potential for catastrophic wildfires, and to 

restore forests recently burned by wildfires. Fire 

exclusion has resulted in a gradual shift in stand 

composition from shade-intolerant tree species such as 

ponderosa pine, to dense stands of shade-tolerant 

species such as Douglas-fir and grand fir (Wisdom et al. 

2000). High stand densities can make foraging difficult 

for Lewis’ woodpecker, and reduce the vigor of oaks 

used by western grey squirrels for foraging. The loss of 

large trees and snags can limit the abundance of nesting 

and foraging sites for woodpeckers, bats, and other

wildlife. 

Herbicides are an important tool for improving forest

productivity in the Marine Ecoregion, and studies

suggest that the range of wood volume gains from

effectively managing forest vegetation (primarily using

herbicides) is 30% to 450% for Pacific Northwest

forests (Wagner et al. 2004). Herbicides can be effective 

in improving forest wildlife habitat by 1) reducing 

populations of invasive exotic plants, 2) creating snags 

and downed woody material, 3) maintaining patches of 

early-successional vegetation within late-successional 

communities, and 4) maintaining woody and

herbaceous plant communities for browsing species

(Lautenschlager et al. 1995; Wagner et al. 2004). 

Herbicide use in forests has often been perceived by the 

public as inconsistent with the ecological aspects of

forest management. As discussed above, under typical

application scenarios, herbicides evaluated by the BLM

pose negligible chronic or acute toxicity hazards to

wildlife, and most are rapidly eliminated from animal

systems once ingested or absorbed (Tatum 2004;

Wagner et al. 2004). Response by wildlife to herbicideinduced habitat alteration is highly variable. Blacktailed deer readily browse Douglas-fir seedlings treated

with 2,4-D, atrazine, and fosamine, but reduce use of 

seedlings treated with glyphosate (Bovey 2001). 

Because herbicides can alter habitat and successional

patterns, they may be useful for restoring desirable 

habitat conditions, especially early-successional plant

communities (see review in Guynn et al. 2004). 

Due to abundant rainfall along the Pacific Coast,

amphibians are common in habitats west of the Cascade 

Range. As noted above, ERAs did not assess risks to 

amphibians from herbicide treatments, but several 

studies have evaluated risks to amphibians from 2,4-D, 

atrazine, glyphosate, hexazinone, triclopyr, and other 

pesticides. 

Amphibian populations from around the world have 

apparently declined or experienced range reductions, 

and some populations have experienced increases in

developmental deformities (Kiesecker 2002). Kiesecker

(2002) found that trematode infection was required for 

development of limb deformities in wood frogs, but that

deformities were more common at sites adjacent to 

agricultural runoff where atrazine and other pesticides 

were used. 

A study of herbicides sprayed for pest control in Canada 

showed that effects to amphibian embryos and larvae

from hexazinone, glyphosate, triclopyr, and three other 

herbicides that are not used by the BLM were similar to

those found in freshwater fish when herbicides were 

applied at typical application rates. High concentrations 

of hexazinone did not affect embryos and tadpoles, but 

2.4 ppm or greater concentrations of triclopyr did lead 

to death of newly hatched tadpoles (Berrill et al. 1994;

Berrill et al. 1997). 

Several studies have shown high rates of larval

amphibian mortality in areas treated with glyphosate

formulations containing POEA (Relyea 2005a). 

BLM Vegetation Treatments Using Herbicides 4-113 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Although glyphosate and POEA can be absorbed by soil 

and broken down by soil microbes, complete

breakdown can take weeks and death still occurs in 

amphibians exposed to glyphosate formulations 

containing POEA (Giesy et al. 2000). However, Relyea

(2005b) found that 2,4-D had no impact on tadpoles and

did not lead to a loss of species richness in aquatic 

communities. 

Herbicides can often be more selective than mechanical

or fire treatments and just as selective as manual

treatments in forestlands (Payne and Bryant 1998). 

Common herbicides used in forest wildlife management 

include asulam, atrazine, 2,4-D, glyphosate, simazine, 

and tebuthiuron; however, the BLM has not used 

atrazine or asulam on public lands since at least 1997. 

Spraying herbicides over conifer plantations eliminates 

competing shrubs and hardwood sprouts, but also 

reduces the value of these forests to wildlife (Rutske

1969). If treatments are done in patches or strips,

important refuge areas can be created for amphibians, 

reptiles, birds, and small mammals (Payne and Bryant

1998); staggering treatments over several years can

achieve the same effect. 

Weed management in forestlands would reduce or 

eliminate weed populations that displace native plants

that are generally more desirable to wildlife. Plant

species of concern include knapweeds, yellow 

starthistle, toadflaxes, downy brome, and several 

species of thistle. Several studies have shown that elk 

use of forest habitats was substantially lower on sites 

dominated by knapweeds than on sites dominated by

native grasses (Sheley et al. 1999a). Yellow starthistle 

forms dense stands that provide limited value to

wildlife, and it is poisonous to some animals (Sheley et 

al. 1999b). Knapweeds are effectively controlled by

picloram, clopyralid, dicamba, and 2,4-D; these 

herbicides, along with glyphosate, can also be used to 

control yellow starthistle. Dalmatian and yellow 

toadflax displace existing plant communities and 

associated wildlife, although deer have been observed to 

browse Dalmatian toadflax, the seeds are eaten by some

species of birds and small mammals, and the vegetation

can provide some cover for smaller wildlife, toadflaxes 

are not known to be heavily used by any native species 

(Lajeunesse 1999). Toadflaxes are often controlled 

using picloram. Thistle spines make them unpalatable to 

some wildlife and often create effective barriers to

movement (Beck 1999). Several herbicides, including 

chlorsulfuron, clopyralid, 2,4-D, dicamba, imazapic,

metsulfuron methyl, and picloram, are used to control

thistles. 

Phenoxy herbicides (2,4-D, 2,4-DP) have been used in

the California chaparral to stimulate shrub regrowth and 

increase production of grass and forbs (USDI BLM

1988a). Dense, decadent chaparral provides minimal

value to deer and other large mammals, but good food 

and cover for reptiles, small mammals, and birds, such 

as mountain quail, thrashers, and wrentits. In one study, 

species composition, population size, and relative

abundance of birds did not change 2 years after 

herbicide treatment of chaparral (Beaver 1976). Sites of 

dense chaparral treated as a patchwork mosaic should

benefit most edge wildlife. 

Glyphosate treatments during fall have been used to 

improve the success of perennial grass seedings in 

grasslands dominated by invading annuals in California

(Vallentine 1989). Herbicides can also be a valuable

tool for improving elk habitat by toppling oaks in areas 

where dense stands occur. Elk use increased

dramatically after Gambel oak was sprayed with

herbicides (Kufeld 1977); mule deer response was 

minimal. Small areas of 12 acres or less should be 

treated to create habitat diversity and feeding sites. 

Tebuthiuron and triclopyr are effective for treating

almost all oak species. Large trees should be protected

for their mast-producing potential because acorns are

relished by turkey, bear, deer, elk, and other wildlife

species (Payne and Bryant 1998). 

Impacts by Alternative 

The following sections detail the expected effects of

each of the five alternatives on terrestrial wildlife, and

compare these effects to those expected under the other

alternatives. These effects may vary depending on the

percentage of acres treated using different application

methods and different herbicides, as well as the size of 

treatment events. Earlier in this section, SOPs were

described that would reduce some of the impacts

described below. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation treatment programs in

14 western states. Based on the information gathered 

from BLM field offices in 2002, approximately 3.4% of 

acres would be treated specifically to benefit wildlife

and their habitats, although all treatments would be 

likely to provide long-term benefits to wildlife. 

Under this alternative, the BLM would be able to use 

the 20 herbicides previously approved in earlier EIS 

BLM Vegetation Treatments Using Herbicides 4-114 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

RODs. However, based on the recent pattern of BLM 

herbicide use, it is likely that approximately three

fourths of the area treated would involve the use of only 

four herbicides: 2,4-D, glyphosate, picloram, and

tebuthiuron (Table 2-5). Herbicide use under the No 

Action Alternative would impact wildlife on

approximately 305,000 acres. Public lands in Alaska, 

Nebraska, and Texas would not be eligible for herbicide 

treatments under this alternative. 

Wildlife impacts (positive and negative) would be 

similar to those that have occurred in the past 10 years. 

Negative impacts to wildlife could be lower than under 

the other herbicide-use alternatives, based on the

relative number of acres treated. Impacts would include

loss of non-target vegetation used by wildlife, and 

effects to wildlife health from exposure to herbicides. 

Aerial applications have the greatest potential to affect

wildlife because they typically cover the largest 

treatment areas (USDI BLM 1991a). The use of 

glyphosate is of concern in areas with amphibians. 

Long-term positive impacts on wildlife communities 

(i.e., improvements in habitat and ecosystem function) 

would be much less under this alternative than under the 

other alternatives. Invasive plant populations would

likely continue to expand at the current rate or greater,

increasing damage to native plant communities and

wildlife habitat and inhibiting ecosystem functions 

associated with those communities. 

In addition, because the new herbicides proposed in this 

PEIS (diquat, fluridone, imazapic, and Overdrive®) 

would not be used, risks to wildlife would be different

under this alternative than under the other herbicide 

treatment alternatives. Imazapic does not present any 

risks to wildlife in modeled scenarios (similar to

chlorsulfuron, dicamba, fluridone, metsulfuron methyl, 

and sulfometuron methyl), and Overdrive® poses a low 

to moderate risk to large mammalian herbivores under 

the chronic ingestion of contaminated vegetation

scenario. Diquat is fairly toxic to terrestrial wildlife, 

particularly under food ingestion scenarios (similar to

2,4-D and diuron). However, diquat is an aquatic 

herbicide and frequent exposure to terrestrial animals 

would not be expected. Therefore, the No Action

Alternative would prevent the use of a greater repertoire

of herbicides that are not injurious to terrestrial animals,

possibly increasing per area risks to wildlife if more 

injurious herbicides were used instead (e.g., 2,4-D, 

bromacil, diuron, tebuthiuron, triclopyr), as well as 

decreasing the possibilities of more effective wildlife

habitat and native ecosystem improvements. 

2,4-DP, asulam, atrazine, fosamine, mefluidide, and 

simazine were approved for use in the earlier BLM EIS 

RODs, but the BLM has not used any of these 

herbicides, except fosamine (< 50 acres annually), since

1997, and does not plan to utilize them in the near 

future. These six herbicides have low toxicity to 

wildlife, although atrazine could exhibit endocrinedisrupting effects via inhibition of androgen receptors in 

mammals, amphibians, and potentially reptiles (Rohr et

al. 2006; see review in Storrs and Kiesecker 2004). 

Atrazine appears to increase mortality in amphibians 

and acts as an endocrine disruptor that chemically

castrates and feminizes male amphibians (Hays et al.

2006; Rohr et al. 2006). A review by the USEPA 

(2003e), however, suggested that information about the 

effects of atrazine of amphibians was inconclusive. 

Under this alternative, the BLM would use other 

herbicides, including bromacil, diuron, sulfometuron

methyl, and triclopyr, which are effective in controlling

weeds and invasive vegetation, but have less risk to 

wildlife. 

The BLM would not be able to use herbicides in

Alaska, Nebraska, and Texas under the No Action 

Alternative, but would be able to conduct herbicide 

treatments in these states under the other herbicidetreatment alternatives. No herbicide treatments would

occur in Alaska or Nebraska, based on information

provided by local field offices during 2002. 

Approximately 11,000 acres would be treated annually

in Texas using herbicides under the other alternatives, 

which would benefit wildlife in the Subtropical Desert

Ecoregion. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

The Preferred Alternative would result in the treatment

of approximately 932,000 acres across the western

BLM states. In addition to the 14 previously-approved

herbicides, the BLM would be able to use the four new 

herbicides evaluated in this PEIS. Based on the 

information provided by local field offices in 2002, 

approximately 6.8% of acres (6 times as many acres as 

under the No Action Alternative) would be treated

specifically to benefit wildlife and their habitats, 

although all treatments would be likely to provide longterm benefits to wildlife. 

This alternative would result in the most extensive 

effects to wildlife because it proposes the most acres for 

treatment (3 times the acreage proposed under the No 

Action Alternative). The relative degree of positive

BLM Vegetation Treatments Using Herbicides 4-115 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

versus negative impacts would depend on the relative 

amount of each herbicide used; the chance for negative 

impacts would be higher if diuron and/or diquat and

possibly bromacil and 2,4-D were used extensively. If 

these herbicides were used only in restricted scenarios,

as is proposed, positive impacts could outweigh 

negative impacts. The use of the four new herbicides 

and the ability to use future herbicides that become

registered with the USEPA would allow BLM managers 

more options in choosing herbicides that best match

treatment goals and application conditions, and are less 

toxic, and may therefore reduce overall per capita risk to

wildlife (three of the four new herbicides present little 

to no risk to wildlife) and increase positive habitat and

ecosystem benefits from treatment. In addition, the

ability to use future registered herbicides would allow 

the BLM to employ the most technologically-advanced

herbicides, which would likely reduce risk to wildlife

and increase management benefits. This alternative 

would also reduce risk and negative impacts that might

be associated with other vegetation management

methods (e.g., risk of escaped prescribed fires; see the 

PER). 

Based on current BLM usage, 2,4-D, glyphosate, 

picloram, and tebuthiuron would comprise about 70%

of herbicides that would be used under this alternative. 

The risks and benefits of using these and other 

currently-available herbicides are discussed under the

No Action Alternative. Approximately 10% of all 

treatment acres would be treated with the new 

herbicides, and about three-fourths of these acres would

be treated using imazapic. Imazapic could be used in all

areas except riparian and wetland areas. Imazapic would 

be used to control downy brome, hoary cress, leafy

spurge, perennial pepperweed, and several other

invasive species that are known to displace native 

vegetation and alter wildfire intensity and frequency.

Imazapic use would occur in the Great Basin where

downy brome has replaced native shrubs after recent 

catastrophic fires. As noted above, several wildlife 

species populations have shown sharp declines in the 

Great Basin, apparently due to loss of sagebrush and 

other key habitat components. 

About 2% of all treatment acres would be treated using 

Overdrive®. Overdrive®

 would be used on rangelands; 

ROW; oil, gas, and mineral sites; and cultural and 

recreation sites. This herbicide is not effective in downy 

brome control, but does control oak species to reduce 

hazardous fuels. It also can be used to control several

annual broadleaf species, including burningbush, 

pigweed, and Russian thistle; several biennial species, 

including bull, musk, and Scotch thistle, teasel, and 

diffuse knapweed; and several perennial species 

including spotted and Russian knapweed and field 

bindweed. As discussed earlier, these species displace

native vegetation, which is more desirable to wildlife,

and can lead to conditions that foster wildfires that kill 

or harm wildlife and destroy habitat. 

In addition to being able to use four new herbicides 

under this alternative, the BLM would be able to use 

herbicides in Alaska, Nebraska, and Texas. Herbicide

use should be avoided in Arctic tundra and subarctic

forests. At this time, the BLM does not propose to

conduct herbicide treatments in Arctic and subarctic

tundra and forest habitats, but could do so in the 

future should the need arise and the agency deems

that treatments were safe for wildlife and their 

habitats. If used, herbicide weed treatments would 

likely be targeted for developed areas and ROW. The 

ability to use herbicides in Nebraska and Texas would

allow for more comprehensive weed management

programs in these states, which should reduce the 

negative effects of invasive species on native

vegetation and improve wildlife habitat. 

Under this alternative, over 70% of treated acres would

be in the Temperate Desert Ecoregion, a much greater

proportion than under the No Action or other 

alternatives. Fifteen percent of treatments would occur 

in the Temperate Steppe Ecoregion. As with the No

Action Alternative, treatments in the Temperate Desert 

Ecoregion would primarily target sagebrush,

rabbitbrush, and other evergreen shrubland species, and 

annual grass and perennial forb weeds, while those in

the Temperate Steppe Ecoregion would focus on control

of invasive annual and perennial grasses and forbs. 

Much of the increase in treatment acreage in this region 

is associated with the Great Basin Restoration Initiative 

and related attempts to restore fire-damaged ecosystems 

and improve habitat for sage-grouse and other 

sagebrush-dependent species. 

Alternative C – No Use of Herbicides 

Under Alternative C, wildlife would not be affected by 

herbicide use. Primary effects would stem from other 

vegetation treatment methods (see the accompanying 

PER). Positive ecosystem and habitat benefits as a result 

of vegetation management could be reduced under this

alternative, as there are certain invasive species for 

which herbicide use is the only effective method of 

treatment or for which other methods are impractical

due to cost, time, accessibility, or public concerns (e.g., 

saltcedar in riparian areas). For example, rough terrain

BLM Vegetation Treatments Using Herbicides 4-116 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

may prevent treatment by methods requiring terrestrial

vehicle and/or foot access, while aerial treatment with

herbicides in these areas would be possible. In addition, 

it is often difficult to eradicate some species, such as

shrubs that resprout from rhizomes, by means other than 

herbicide application (e.g., rabbitbrush, honey mesquite, 

sand shinnery oak, tree cholla). Similarly, pre-emergent

herbicides that persist in the soil are the most effective

means of controlling invasive plants with seeds that 

remain viable for long periods of time. 

Under this alternative, in the absence of herbicide

treatments, invasive plant populations would likely

continue to spread, possibly at increasing rates, and 

cause further damage to susceptible native plant 

communities and wildlife habitat, particularly in areas 

and for species where other treatment methods are not

effective or possible (e.g., large tracts of rangeland or 

grassland dominated by invasive, resprouting shrubs or

without enough fine fuels to carry prescribed fires). 

However, it is uncertain how potential negative impacts 

from this alternative (mostly indirect) would compare

with negative direct and indirect impacts from herbicide 

use. 

Alternative D – No Aerial Applications 

Alternative D would allow the use of the same

herbicides in the same areas as under the Preferred

Alternative, and would have similar benefits resulting

from the increased availability of new and future

herbicides. However, this alternative would not allow 

the use of aerial application methods, thereby 

dramatically reducing the acreage on which treatments 

(530,000 acres) would be possible because some large

and remote areas cannot be effectively treated by

ground application methods. 

Because non-aerial treatments would be smaller, fewer 

wildlife would be exposed to herbicides than under 

alternatives with aerial treatment options (it would be

difficult for most wildlife to avoid spray from aircraft

by fleeing). Ground treatments would also be better able

to avoid patches of important wildlife habitat or use 

areas within the larger treatment area than aerial

treatments. 

This alternative would result in fewer impacts to

wildlife due to off-site drift than under the Preferred

Alternative. Off-site drift was not specifically modeled 

for most herbicides (consumption of contaminated

vegetation off site was modeled for most of the Forest 

Service herbicides, with no risk demonstrated for any of

these herbicides except triclopyr at the maximum 

application rate); however, off-site drift impacts to

vegetation are somewhat common (see Vegetation 

section in this chapter), and could alter habitat as well as

forage. Conversely, without the option for aerial

spraying, the BLM would be unable to treat large areas 

of vegetation under Alternative D, which could 

negatively impact wildlife habitat in these areas over the

long term. 

Under this alternative, long-term negative impacts on 

wildlife habitat and ecosystems could be greater than

any potential short-term negative effects to wildlife that

would result from aerial applications under other 

alternatives. In addition, direct and indirect impacts 

from other vegetation treatment options could increase 

if these other treatments were used more extensively to 

compensate for the loss of acres able to be treated by 

herbicides (see the PER). 

Prescribed fire and mechanical treatments would be

substituted for aerial herbicide treatments as much as 

possible in large areas proposed for treatment. Fire

would not be effective in areas with insufficient fuels to

carry fire, and could kill or harm wildlife that were

unable to flee, as well as substantially alter habitats. Fire 

could also result in substantial damage to sagebrush 

stands and enhance the development and spread of 

downy brome and other annual grasses (USDI BLM

1991a). Mechanical treatments might not be suitable in

areas where sprouting species, such as rabbitbrush, 

might increase after mechanical treatment. This 

alternative would preclude treatment of large expanses 

of downy brome and other invasive annual grasses

using imazapic and other herbicides. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Approximately 466,000 acres would be treated under 

Alternative E, which is slightly less than the amount that

would be treated under Alternative D, and less than half 

of the amount that would be treated under the Preferred

Alternative. In addition to a relatively low impact to

wildlife as a result of minimal acreage treated, pertreatment impacts under Alternative E would be lower 

than under the other herbicide-use alternatives because

of some of the standards detailed by this alternative

(e.g., preferential use of spot rather than broadcast

applications, preferential treatment of small versus large

infestations). 

Sulfonylurea herbicides and other ALS-inhibiting 

herbicides (e.g., chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, sulfometuron methyl) block the 

BLM Vegetation Treatments Using Herbicides 4-117 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

synthesis of amino acids that are required for protein

production and cell growth, thereby resulting in plant

death. ALS-inhibiting herbicides would not be used

under this alternative because data suggest they have the 

potential to damage off-site native and crop plant

species under certain conditions of environment and

application. These herbicides are biologically active at

small concentrations, and relatively low application 

rates are necessary to manage target plants. In 1981, the 

Environmental Effects Division of the USEPA 

recommended against registering sulfonylurea 

herbicides because they persist for long periods of time

in the environment and they cannot be detected at low 

levels. However, in this assessment, the ALS-inhibiting 

herbicides mostly posed no risk to terrestrial wildlife

(chlorsulfuron, imazapic, sulfometuron methyl), except

for a few cases of low risk (imazapyr, metsulfuron

methyl), suggesting that prohibiting the use of these 

herbicides would not likely benefit wildlife and could 

indirectly harm wildlife if more toxic herbicides that are 

currently available to the BLM were used in their place. 

Alternative E incorporates other management practices 

that would be likely to have positive impacts on wildlife 

communities and habitats. Alternative E would limit the

use of broadcast applications, which would reduce the 

possible risks to wildlife associated with off-site drift

and consumption of vegetation across large areas. 

However, these applications would be available for use

in appropriate situations (i.e., where no other method 

was practical and susceptible non-target plant species 

and aquatic areas were distant from the application 

area), which would allow some positive ecosystem

benefits from larger-scale herbicide applications. In

addition, herbicides would not be used in National 

Riparian Conservation Areas, which would protect

wildlife species that frequent the riparian zone and 

attendant ecosystem functions in these key areas. While 

per-treatment ecosystem benefits could be greater under 

Alternative E than under the other herbicide-use 

alternatives as a result of this ecosystem-based 

management approach, overall benefits to vegetation

and ecosystems across the 17 western states (that cannot 

be attained by other treatment methods) would be lower 

under this alternative because of the relatively low 

treatment acreage and the inability to use certain 

practices in situations that might require their use (e.g., 

use of ALS-inhibiting herbicides on highly aggressive 

weeds). 

Mitigation for Herbicide Treatment 

Impacts 

The following actions would reduce the risks to wildlife

associated with herbicide applications: 

• Apply dicamba, diuron, glyphosate, 

hexazinone, tebuthiuron, and triclopyr at the 

typical application rate to minimize risks to 

terrestrial wildlife. 

• Minimize the size of application areas, where 

practical, when applying 2,4-D, bromacil,

diuron, and Overdrive® to limit impacts to

wildlife, particularly through the contamination 

of food items. 

• Where practical, limit glyphosate and 

hexazinone to spot applications in rangeland

and wildlife habitat areas to avoid 

contamination of wildlife food items. 

• Avoid using glyphosate formulations that 

include R-11® in the future, and either avoid 

using any formulations with POEA, or seek to 

use the formulation with the lowest amount of 

POEA available to reduce risks to amphibians. 

• Do not aerially apply diquat directly to 

wetlands or riparian areas. 

• Do not apply bromacil and diuron in 

rangelands, and use appropriate buffer zones 

(see Vegetation section) to limit contamination 

of off-site vegetation, which may serve as 

forage for wildlife. 

Special Status Wildlife Species 

Introduction

As discussed in Chapter 3, public lands in the western

U.S. support over 200 species of terrestrial wildlife 

(including birds, mammals, amphibians, reptiles, 

mollusks, and arthropods) that have been given a special

status based on their rarity or sensitivity. Included are 

67 species that are federally listed as threatened or 

endangered, or are proposed for federal listing. Some of 

these species have habitat requirements that have been

or are being altered or reduced by invasions of nonnative plant species. The Vegetation Treatments on

Bureau of Land Management Lands in 17 Western

States Programmatic Biological Assessment (USDI

BLM 2007b) provides a description of the distribution, 

life history, and current threats for each federally-listed

BLM Vegetation Treatments Using Herbicides 4-118 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

animal species, as well as species proposed for listing. 

The BA also discusses the risks to federally-listed

terrestrial wildlife associated with each of the herbicides 

proposed for use by the BLM under the different

alternatives. 

Impacts Assessment Methodology 

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM and Forest Service to 

assess the impacts to sensitive wildlife species from the

use of herbicides (ENSR 2005b-k; SERA 2005a). The 

ERA methods are summarized earlier in this section. 

Methods used by the BLM are presented in detail in the

Vegetation Treatments Programmatic EIS Ecological 

Risk Assessment Protocol (ENSR 2004) and in 

Appendix C; methods used by the Forest Service can be 

viewed at http://www.fs.fed.us/r6/invasiveplant-eis/. 

As discussed earlier, the USEPA has defined various 

LOCs for use in assessing risks to different organisms. 

As far as risks to terrestrial wildlife are concerned, the 

LOC for acute risks to endangered species is the most 

conservative. However, there is only one LOC to

determine chronic risks. Risk assessments completed by 

the BLM used the USEPA’s chronic risk LOC and the 

acute high risk when documenting risks to most

terrestrial wildlife. Risk assessments used the chronic 

risk LOC and the acute endangered species LOC when

documenting risks to special status terrestrial wildlife. 

There are potential risks to special status wildlife

species associated with herbicide use. Although the

predicted risks for adverse health effects to individual

organisms are the same as those predicted for non 

special status wildlife, the associated population- and

species-level effects would be much greater for many

sensitive species because of their limited/fragmented 

distribution and limited population size. Risks to

special status wildlife can be minimized by following

certain SOPs, which can be implemented at the local

level according to specific conditions (see Table 2-8). 

These SOPs include the following: 

• Survey for special status wildlife species before

treating an area. Consider effects to these

species when designing treatment programs. 

• Use drift reduction agents to reduce the risk of 

drift hazard. 

• Select herbicide products carefully to minimize 

additional impacts from degradates, adjuvants, 

inert ingredients, and tank mixtures. 

• Avoid treating vegetation during time-sensitive 

periods (e.g., nesting and migration) for species 

of concern in the area to be treated. 

Summary of Herbicide Effects to Special Status 

Wildlife Species 

Non-native plant species reduce the suitability of some

habitats to support special status wildlife species. For 

some species, particularly butterflies and moths, certain

plant species must be present on a site to serve as larval 

host plants. Other species require, or at the very least

prefer, certain plants as food sources. For example,

lesser and Mexican long-nosed bats meet most of their 

dietary needs from agave and cactus (USFWS 1994b, 

1995a), and the northern Idaho ground squirrel feeds on 

native bunchgrasses to fulfill a large portion of its 

dietary needs (USFWS 2000). Encroachment of nonnative plant species, and displacement of native plant

species that serve as important sources of food, reduces 

the suitability of the habitat for these wildlife species. 

Similarly, the risks to non-target plants associated with

herbicide applications amount to indirect risks to these

wildlife species through alteration of their habitat. 

For some special status wildlife species it is the 

structure, rather than the species composition of the 

habitat, that makes it suitable. For example, the western

snowy plover nests in areas where vegetation is sparse, 

the Yuma clapper rail is associated with dense marsh

vegetation (USFWS 1997), the southwestern willow 

flycatcher occurs in riparian areas with dense growths 

of deciduous shrubs and trees (USFWS 1995b), and 

kangaroo rats require open, grassland conditions. In 

some cases, invasive plant species alter the structure of

habitats, making them less suitable for supporting

sensitive wildlife species (e.g., the encroachment of

European beachgrass into western snowy plover habitat, 

or the exclusion of marsh vegetation by saltcedar and 

arrowweed in Yuma clapper rail habitat). For these

species, use of herbicides to control weed infestations 

would likely provide a long-term benefit. In other cases, 

non-native plant species may invade an area without

making drastic structural changes, and the suitability of 

the habitat, though not ideal, is maintained (e.g., 

thickets of saltcedar and Russian olive providing nesting

habitat for the southwestern willow flycatcher, or desert

kangaroo rats thriving in annual grasslands dominated 

by non-native plant species such as red brome). For 

these species, use of herbicides may result in some

improvement of habitat, but the long-term benefits may 

not outweigh the short-term risks to the species 

associated with herbicide treatments. 

BLM Vegetation Treatments Using Herbicides 4-119 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

Som

variety

provide adequate

breeding/nesting/denning 

be larger anim

and eat a wide variety

wolves, grizzl

species could 

weed control, 

from

through disturbances associated wit

treat

trucks/ATVs, 

The 

determ

species. Te

likelihood of i

via any

diuron, and hexazinone, for 

risks to 

for applications at the t

or m

herbicides wit

status wildlife species include

diflufenzopyr, i

which no risks to special status wildlife were predicte

via any

Although am

during their t

phase that is 

other terre

assum

Organis

aquatic am

likelihood of i

during a norm

diquat and

Norm

pose a ri

with the great

amphibian spe

direct spra

brom

herbicides wo

according to ERAs: chl

imazapic, Ove

Alter

(No Actio

Under 

public lands would be treat

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-120 June 2007 

ogrammatic EIS 

e special status wildlife species occupy a wide 

 of plant community types, as long as they 

 food, cover, and 

habitat. These species tend to 

als that cover a larger geographic area 

 of food items, such as gray 

y bears, and bald eagles. Although these 

potentially benefit to some degree from 

and are typically at low risk for impacts 

 exposure to herbicide, they may be impacted 

h herbicide 

ments (e.g., presence of herbicide applicators, 

and/or helicopters in their habitat). 

most conservative LOC of 0.1 was used to 

ine risks to special status terrestrial wildlife 

rrestrial herbicides with the greatest 

mpacting special status wildlife species, 

 exposure pathway, include 2,4-D, bromacil, 

which moderate to high 

special status terrestrial wildlife were predicted 

ypical application rate, under one 

ore exposure scenario (Table 4-24). Terrestrial 

h the least likelihood of impacting special 

 chlorsulfuron, 

mazapic, and sulfometuron methyl, for 

d 

 exposure pathway. 

phibians are considered terrestrial wildlife 

errestrial phase, they do have an aquatic 

not represented by risk assessments for 

strial animals. For these species, ERAs 

ed that risks to fish (see Fish and Other Aquatic 

ms section of this chapter) represent risks to 

phibians. Aquatic herbicides with the greatest 

mpacting special status amphibian species 

al application to an aquatic habitat are 

 the more toxic formulation of glyphosate. 

al applications of 2,4-D and imazapyr would not 

sk to aquatic amphibians. Terrestrial herbicides 

est likelihood of impacting special status 

cies as a result of a spill, drift, accidental 

y into an aquatic habitat, or surface runoff are 

acil, diuron, and picloram. The following 

uld pose no risk to aquatic amphibians, 

orsulfuron, diflufenzopyr, 

rdrive®, and sulfometuron methyl. 

native A – Continue Present Herbicide Use 

n Alternative) 

this alternative, approximately 305,000 acres of 

ed with herbicides annually. 

Based on the acreage that would be treated, it is likely 

that special status wildlife species would be exposed to 

herbicides less under this alternative than under the 

other herbicide-use alternatives. Adverse health effects 

associated with herbicide exposure should be less 

extensive as well. Risks to special status species would 

also be lower, although mitigation would be required to 

protect these species (as well as key plant food species) 

from harm under all alternatives, which should 

minimize differences in risk to special status species 

among the alternatives. 

Out of the four herbicide-use alternatives, control of 

weed infestations would likely be the least extensive 

under this alternative, and weed populations would 

spread at a faster rate. Wildlife species for which native 

plant communities provide the most suitable habitat 

would likely fare the worst under this alternative, as far 

as the quality of their habitat was concerned. For 

wildlife species that can successfully utilize habitats 

comprised of non-native plant species, differences 

among alternatives would be less clear. Although 

control of weeds and encouragement of native 

conditions would typically benefit wildlife habitat in 

general, removal of species that provide key habitat 

components (such as saltcedar and Russian olive that 

support nesting southwestern willow flycatchers) could 

harm some special status species. There are also 

disturbances associated with herbicide applications that 

could temporarily impact some special status species. 

The degree of benefits and impacts to wildlife habitat 

from treatments would largely depend on where the 

treatments occurred. 

Under this alternative, only those herbicides currently 

used by the BLM would be used to treat vegetation. The 

majority of the total acreage would continue to be 

treated with picloram, tebuthiuron, and 2,4-D. Out of all 

the herbicides currently used by the BLM, 2,4-D has the 

highest risk to wildlife, according to ERAs. Although it 

is likely that the BLM would continue to use 2,4-D 

extensively because it is inexpensive, alternatives that 

allow for the use of new herbicides (alternatives B, D, 

and E) may offer the BLM more options for substituting 

herbicides that are less toxic to wildlife where special 

status species occur. Picloram and tebuthiuron pose a 

low risk to wildlife if applied at the typical rather than 

the maximum application rate, so continued use of these 

herbicides would have little impact to special status 

wildlife species. 
TABLE 4-24

Risk Categories1 Used to Describe BLM-evaluated Herbicide Effects on Special Status Wildlife According to Expo

BROM1 CHLOR1 DICAMBA DIFLU1 DIQUAT DIURON FLUR1 IMAZ1 OVE

Application Scenario 

Typ2 Max2 Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ 

Direct Spray of Terrestrial WildlifeSmall mammal – 100% absorption 03 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pollinating insect – 100% absorption L L 0 0 L L 0 0 L M L M 0 0 0 0 0 Small mammal – 1st order dermal absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Indirect Contact with Foliage After Direct Spray Small mammal – 100% absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pollinating insect – 100% absorption 0 0 0 0 0 0 0 0 0 L 0 L 0 0 0 0 0 Small mammal – 1st order dermal absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Ingestion of Food Items Contaminated by Direct SpraySmall mammalian herbivore – acute 0 L 0 0 0 L 0 0 0 L 0 L 0 0 0 0 0 Small mammalian herbivore – chronic 0 L 0 0 0 L 0 0 L M L M 0 L 0 0 0 Large mammalian herbivore – acute 0 M 0 0 0 L 0 0 L M 0 M 0 0 0 0 0 Large mammalian herbivore – chronic L M 0 0 L M 0 0 L M M H 0 0 0 0 L Small avian insectivore – acute 0 0 0 0 0 0 0 0 L M 0 L 0 0 0 0 0 Small avian insectivore – chronic 0 0 0 0 0 0 0 0 0 M 0 L 0 0 0 0 0 Large avian herbivore – acute 0 L 0 0 0 0 0 0 0 M 0 M 0 0 0 0 0 Large avian herbivore – chronic 0 L 0 0 0 0 0 0 L H 0 M 0 0 0 0 0 Large mammalian carnivore – acute 0 L 0 0 0 0 0 0 0 L 0 L 0 0 0 0 0 Large mammalian carnivore – chronic 0 0 0 0 L L 0 0 0 0 L L 0 0 0 0 0 

1 BROM = Bromacil; CHLOR = Chlorsulfuron; DIFLU = Diflufenzopyr; FLUR = Fluridone; IMAZ = Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; an2 Typ = Typical application rate; and Max = Maximum application rate.3 Risk categories: 0 = No risk (majority of RQs < most conservative LOC for special status species); L = Low risk (majority of RQs 1-10x most conservative LOC for spec

risk (majority of RQs 10-100x most conservative LOC for special status species); H = High risk (majority of RQs >100 most conservative LOC for special status speci

Risk Category is based on the risk level of the majority of risk quotients observed in any of the scenarios for a given exposure group and receptor type. The reader should 

4 of the ERAs (ENSR 2005b-k) to determine the specific scenarios that result in the displayed level of risk for a given receptor group.

BLMVegetationTreatments Using Herbicides 4-121 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

Alternative B – Expand Herbicide Use and 

Allow for Use of New Herbicides in 17 Western 

States (Preferred Alternative) 

Under the Preferred Alternative, approximately 932,000 

acres of public lands would be treated with herbicides 

annually. Based on this acreage, the incidence of special 

status wildlife exposure to herbicides would be greater 

than under the other alternatives. Adverse health effects 

associated with herbicide exposure would likely be 

greater as well. Risks to special status species would be 

greater, although mitigation to protect these species and

their habitats from harm, as identified in the BA, would

be required under all alternatives, minimizing the 

differences in risk among alternatives. 

Out of all the alternatives, the Preferred Alternative

would likely result in the most extensive control of 

weed infestations, and it is expected that weed

populations would spread at the lowest rate under this 

alternative. Positive and negative impacts to special

status wildlife habitat resulting from herbicide 

treatments, as discussed under the No Action 

Alternative, would likely be in line with the amount of

acreage treated under each alternative, and would

therefore be greatest under this alternative. 

Under the Preferred Alternative, the BLM would be 

able to use 14 of the 20 currently approved herbicides 

that are currently available for use under the No Action

Alternative, as well as four new herbicides and other 

new herbicides that become available in the future. The

two new terrestrial herbicides, imazapic and 

diflufenzopyr pose no risks to sensitive wildlife under 

all exposure scenarios analyzed in ERAs. Therefore, 

risks to special status terrestrial wildlife could be 

reduced under this alternative, provided the BLM used

these herbicides in place of herbicides with higher risks 

to sensitive wildlife, such as 2,4-D and diuron. 

Of the two new aquatic herbicides, diquat poses low to

high risks to aquatic amphibians, depending on the

application rate. There are no risks to aquatic

amphibians associated with fluridone usage at the

typical application rate, but low to moderate risks if it is 

used at the maximum application rate. If diquat were 

used instead of another less toxic herbicide to treat

vegetation in habitats that support special status 

amphibians, herbicide-related impacts would likely be 

greater under the Preferred Alternative than under the 

No Action Alternative. Under the Preferred Alternative, 

however, less than 1% of acres treated with herbicides 

would be treated with diquat. 

Because a greater number of herbicides would be

available for use under this alternative, the BLM would 

have more flexibility to develop treatment programs that 

are more effective at improving wildlife habitat while 

minimizing risks to special status wildlife species than

under the No Action Alternative. Of particular benefit to 

special status wildlife would be a suitable, inexpensive 

replacement for 2,4-D, which poses a high risk to

terrestrial animals. 

Alternative C – No Use of Herbicides 

Under this alternative, no public lands would be treated

with herbicides. Therefore, there would be no impacts 

to special status wildlife species as a result of herbicide

exposure during vegetation treatments. However, the 

BLM would likely be less effective at controlling weed

infestations than under the other alternatives. Therefore, 

there would be fewer benefits to special status wildlife 

habitat under this alternative, as compared to the 

herbicide-use alternatives. In addition, if other treatment

methods were used to control weeds in lieu of 

herbicides, the disturbance to wildlife habitat could be 

greater. Mechanical treatments, for example, would 

potentially be louder and more disturbing to wildlife, 

especially during the breeding season, and vegetation

removal would potentially be more immediate and

complete, with a greater likelihood of altering habitat 

characteristics and injuring small animals present on the

site. 

Alternative D – No Aerial Application of

Herbicides 

Under this alternative, approximately 530,000 acres 

would be treated with herbicides annually, more than

under all other alternatives except the Preferred

Alternative. Based on acreage treated, the likelihood

that special status wildlife species would be exposed to

herbicides and suffer adverse health effects would be 

second highest under this alternative as well. Because

aerial methods would not be used to apply herbicides, 

there would potentially be less risk that special status 

wildlife species would be inadvertently sprayed during

treatments, but an increased risk of disturbing wildlife 

and crushing or hitting animals with trucks/ATVs

because there would be more ground applications. 

Benefits to wildlife habitat associated with herbicide 

treatments would not be as great as under the Preferred

Alternative, particularly in areas that are inaccessible by 

ground methods. The degree of impact to special status 

wildlife would depend on which species were present in

BLM Vegetation Treatments Using Herbicides 4-122 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

areas that could not be treated, and whether non-native 

plant species are a threat to their habitat. 

Under this alternative, the herbicides available for use

by the BLM would be the same as those discussed for 

the Preferred Alternative. The benefits associated with 

flexibility in selecting herbicides, and in using new

herbicides that become available in the future, would be 

the same as those discussed under the Preferred

Alternative. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Under this alternative, approximately 466,000 acres 

would be treated with herbicides annually, more than

under the No Action Alternative, but fewer than under 

the other herbicide-use alternatives. Considering only 

acres treated, special status wildlife species would be

less likely to be exposed to herbicides, and therefore 

would experience fewer herbicide-related impacts than

under the other action alternatives (with the exception of 

Alternative C). Impacts to special status amphibians and 

riparian species from herbicides would be reduced

under this alternative, since herbicide use would be 

discouraged in areas populated by amphibians, and

would not occur in riparian conservation areas. 

Furthermore, the limit in broadcast applications under 

this alternative would decrease the likelihood that

special status wildlife would be directly sprayed by

herbicides. 

Benefits to wildlife habitat associated with herbicide 

treatments would be minimized under this alternative, 

but would still be greater than those under the No 

Action Alternative and Alternative C. The increased

emphasis on passive restoration under Alternative E 

would likely benefit some special status wildlife species 

by reducing disturbance and preventing the spread of 

weeds in some areas. With this type of management in

place, it is possible that fewer vegetation treatments 

would be necessary in certain areas, minimizing risks to

special status wildlife species. 

Under this alternative, the BLM would not be able to 

use chlorsulfuron, imazapic, imazapyr, metsulfuron

methyl, sulfometuron methyl, or any other ALSinhibiting herbicides that are made available in the 

future. According to the ERAs, there are no risks to 

special status wildlife associated with exposure to 

chlorsulfuron, imazapic, or sulfometuron methyl under 

any exposure pathway, even when applied at the 

maximum application rate. In addition, there are no 

risks associated with exposure to imazapyr or 

metsulfuron methyl when applied at the typical

application rate, except in the case of a small bird eating 

contaminated invertebrates (low risk). The risks

associated with applying either of these two chemicals 

at the maximum application rate are none to low, 

depending on the exposure pathway. Since these ALSinhibiting herbicides are among the most benign as far 

as risks to terrestrial animals are concerned, there would 

be no apparent benefit to special status wildlife from

discontinuing their use. Furthermore, there could be

increased risks to special status wildlife from exposure 

to herbicides under this alternative if more toxic 

herbicides (such as 2,4-D, diuron, or hexazinone) were 

used in place of ALS inhibitors. 

The risks to special status amphibians associated with 

the use of ALS-inhibiting herbicides are generally none 

or low, with the exception of an accidental spill 

exposure of imazapyr. Therefore, increased risks to

special status amphibians could occur if the BLM 

substituted more toxic herbicides (e.g., bromacil, 

diuron, or glyphosate) in place of ALS inhibitors. 

However, since use of herbicides would be discouraged 

in areas populated by amphibians under this alternative, 

impacts to special status amphibians could still be lower 

under this alternative than under the other herbicide-use 

alternatives. 

Since the BLM would be able to use new herbicides that

are made available in the future under this alternative, 

there would be more flexibility for creating effective

treatment programs that minimize risks to special status 

wildlife species than under alternatives A and C.

However, the inability to use ALS-inhibiting herbicides 

would reduce this flexibility below the level offered

under alternatives B and D. 

Mitigation for Herbicide Treatment Impacts 

The following mitigation is recommended to reduce the 

likelihood of impacts to special status terrestrial wildlife 

species from herbicide applications. This mitigation 

should be implemented in addition to the SOPs 

designed to protect wildlife and the general mitigation

for wildlife. 

• To protect special status wildlife species,

implement all conservation measures for 

terrestrial animals presented in the Vegetation 

Treatments on Bureau of Land Management

Lands in 17 Western States Programmatic 

Biological Assessment. Apply these measures 

to sensitive species, as well as listed species 

(refer to conservation measures for a similar

BLM Vegetation Treatments Using Herbicides 4-123 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

size and type of species, of the same trophic 

guild). 

• Avoid using glyphosate formulations that 

include R-11® in the future, and either avoid 

using any formulations with POEA, or seek to 

use the formulation with the lowest amount of 

POEA available, to reduce risks to special 

status amphibians. 

Livestock 

Introduction 

Public lands provide an important source of forage for

many ranches and help to support the agricultural

component of many communities scattered throughout

the West. Approximately 165 million acres of public

lands are open to livestock grazing, with use levels 

established by the Secretary of the Interior and

administered through the issuance of grazing

permits/leases. The majority of the grazing permits 

issued by the BLM involve grazing by cattle, with fewer 

and smaller grazing permits for other kinds of livestock, 

primarily sheep and horses. Many allotments are 

managed according to an allotment management plan,

which outlines how livestock grazing is managed to 

meet multiple-use, sustained-yield, and other needs and 

objectives, as determined through LUPs. Even if there is 

no allotment management plan, grazing is managed to 

ensure that 1) watersheds are in or are making 

significant progress towards properly functioning 

physical condition; 2) ecological processes including 

the hydrologic cycle, nutrient cycle, and energy flow are

maintained; 3) water quality complies with state water 

quality standards; and 4) habitats are or are making 

significant progress towards being restored or

maintained for proposed, candidate or listed federal

threatened and endangered species and other special

status species.

Scoping Comments and Other Issues 

Evaluated in the Assessment 

This section aims to contribute to the understanding of 

the impacts of herbicides on non-target species, 

focusing on livestock.. Evaluation of direct impacts of

herbicides to livestock will help in the selection of lesstoxic herbicides where feasible, which was a scoping

concern identified by numerous respondents. 

The alternatives present a variety of herbicide use levels 

(including no use) for evaluation of relative positive and 

negative effects on livestock, and one of the alternatives 

will evaluate the relative impacts of aerial versus ground 

application on livestock; these were key issues

identified in the scoping process. Evaluation of the 

effects of herbicide use on livestock is in concert with

the goal identified by some respondents of improving 

the management of public lands for multiple use and 

public benefit. 

Standard Operating Procedures 

Herbicide use poses a potential risk to livestock; 

however, risk can be minimized by following certain

SOPs, which can be implemented at the local level

according to specific conditions. The following general 

procedures are designed to reduce potential unintended

impacts to livestock from the application of herbicides 

in the BLM vegetation management program: 

• Whenever possible and whenever needed, 

schedule treatments when livestock are not 

present in the treatment area. Design treatments 

to take advantage of normal livestock grazing 

rest periods, when possible. 

• As directed by the herbicide label, remove 

livestock from treatment areas prior to 

herbicide application, where applicable. 

• Use herbicides of low toxicity to livestock, 

where feasible. 

• Take into account the different types of

application equipment and methods, where

possible, to reduce the probability of 

contamination of non-target food and water

sources. 

• Avoid use of diquat in riparian pasture while 

pasture is being used by livestock. 

• Notify permittees of the project to improve 

coordination and avoid potential conflicts and 

safety concerns during implementation of the 

treatment. 

• Notify permittees of livestock grazing or 

feeding restrictions, if necessary (see below for 

restrictions associated with each herbicide).

• Notify adjacent landowners prior to treatment. 

• Provide alternate forage sites for livestock, if 

possible. 

BLM Vegetation Treatments Using Herbicides 4-124 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

These procedures would help minimize impacts to

livestock and rangeland on western BLM lands to the

extent practical. As a result, long-term benefits to

livestock from the control of invasive species would

likely outweigh any short-term negative impacts to

livestock associated with herbicide use. 

Impacts Assessment Methodology 

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM and Forest Service to 

assess the impacts to livestock from the use of 

herbicides (ENSR 2005b-k; SERA 2005a). Risks to 

livestock were not specifically evaluated in these 

documents, which focused on risks to plants, fish and

wildlife. However, results from the evaluation of 

terrestrial animal species can be applied to livestock

species (i.e., results for large herbivores [154 pound 

mule deer] are applied to evaluate risks to common

grazing animals on BLM lands—cows, sheep, and

horses). The ERA methods are summarized in the 

Wildlife section of this chapter. Methods used by the 

BLM are presented in detail in the Vegetation 

Treatments Programmatic EIS Ecological Risk 

Assessment Protocol (ENSR 2004) and in Appendix C; 

methods used by the Forest Service can be viewed on 

the Internet at http://www.fs.fed.us/r6/invasiveplanteis/. 

Summary of Herbicide Impacts 

The extent of direct and indirect impacts to livestock

would vary by the effectiveness of herbicide treatments 

in controlling target plants (that are not used as forage) 

and promoting the growth of native vegetation (that is 

used as forage), the extent and method of treatment 

(e.g., aerial vs. ground) and chemical used (e.g., toxic 

vs. non-toxic, selective vs. non-selective), the physical

features of the terrain (e.g., soil type, slope), and the

weather conditions (e.g., wind speed) at the time of 

application. Possible adverse direct effects to individual 

animals include death, damage to vital organs, change 

in body weight, decreases in healthy offspring, and

increased susceptibility to predation. Possible adverse 

indirect effects include reductions in forage amount and 

preferred forage type. The impacts of herbicide use on

livestock would depend directly on the sensitivity of

each species to the particular herbicides used, the 

pathway by which the individual animal was exposed to

the herbicide, and indirectly on the degree to which a

species or individual is positively or negatively affected

by changes in rangeland conditions, including forage 

quality and availability. 

Livestock would have a greater chance of being directly 

adversely impacted by herbicide use if their range extent 

was partially or completely sprayed because they would 

have greater exposure to herbicides⎯either via direct 

contact with the herbicide upon application or indirect 

contact via dermal contact with vegetation or ingestion 

of vegetation. However, livestock could be removed

from an area during vegetation treatment, or treatments 

could be scheduled to occur when livestock were not 

present, reducing the potential risks. If livestock are 

removed from the area specifically to facilitate

vegetation treatment, the grazing permittee would be 

adversely affected as a result of the area being

unavailable for grazing purposes. The permittee would

need to either find alternative pasture somewhere else,

or modify ranching operations to account for the 

unavailable forage, which would result in increased 

costs and/or a loss of income. 

Even though large treatments (e.g., aerial applications 

on rangelands) would usually occur when livestock are 

not in the treated pasture, some risk of indirect contact

and consumption of contaminated vegetation over a 

large area would still exist. Some spot treatments could

be applied at any time, regardless of the presence of 

livestock, but in situations where spot treatments are

proposed in livestock concentration areas such as 

riparian areas, treatments may need to be conducted

when livestock are not present or temporary fencing

may be needed to reduce livestock exposure. 

Livestock may experience greater impacts in systems 

where herbicide transport is more likely, such as areas 

where herbicides are aerially sprayed adjacent to 

rangeland, dry areas with high winds, or areas where 

rainfall is high and soils are porous; however these 

scenarios have not been modeled. The degree of 

interception by vegetation, which depends on site and 

application characteristics, would also affect direct

spray impacts. As is evident, the impacts of herbicide

use on livestock would be site and application specific, 

and as such, site assessments would have to be 

performed, using available impact information, to 

determine an herbicide-use strategy that would

minimize impacts to livestock. 

The BLM and Forest Service risk assessments

suggested several possible common impacts of

herbicides to livestock (ENSR 2005b-k; SERA 2005a). 

Livestock, which likely consume large amounts of

grass, have a relatively greater risk for harm than 

animals that feed on other herbaceous vegetation or 

seeds and fruits, because herbicide residue is higher on

BLM Vegetation Treatments Using Herbicides 4-125 June 2007 

Final Programmatic EIS
ENVI

BLM 

Final Pr

grass than it is on other pl

Pfleeger et al. 1996); this is especially

exam

the BLM risk assessm

herbicide are

exclusively 

suggesting th

appropriate fo

has dem

involving cons

In case

noxious and u

would be sho

from

herbicides are

eradicating invasive plant

infestations c

capacity fo

most 

prefe

which often have low palatability as a re

such as toxins, spines, and/or distasteful com

addition, so

houndstongue,

Johnswort

and sheep are m

cattle, they

forage species over weeds (Olsen and Wallander 1998, 

Olson 1999). The success of weed 

determ

long term

Treat

wildfi

livestock. Weeds that 

rangelands include downy bro

burningbush, oak, piny

high intensity wildfi

tracts of 

grazing. So

program

(e.g., gly

Over the 

livestock reari

associated wit

would not be 

have consu

herbicides wi

herbicide label

allowed to graze on areas tre

for the ti

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-126 June 2007 

ogrammatic EIS 

ants (Fletcher et al. 1994, 

 evident when 

ining risk levels of large mammalian herbivores in 

ents. However, harmful doses of 

 not likely unless the animal forages 

within the treatment area for an entire day, 

at smaller treatments may be more 

r rangelands in cases where an herbicide 

onstrated risk to herbivores under scenarios 

umption of contaminated vegetation. 

s where herbicide treatments reduce the cover of 

npalatable weeds on grazed lands, there 

rt- and long-term benefits to livestock 

 increased quality of forage. In some cases, 

 the most effective means of controlling or 

 species. Noxious weed 

an greatly reduce the land’s carrying 

r domestic livestock, which tend to avoid 

weeds (Olson 1999). Cattle, in particular, 

rentially graze native plant species over weeds, 

sult of defenses 

pounds. In 

me noxious weeds (e.g., common tansy, 

 Russian knapweed, and common St. 

) are poisonous to livestock. Although goats 

ore likely to consume alien weeds than 

 also tend to select native or introduced 

removal would 

ine the level of benefit of the treatments over the 

. 

ments that reduce the risk of future catastrophic 

re through fuels reduction would also benefit 

may present a fire hazard in 

me, Russian thistle, 

on, and juniper. Uncontrolled, 

res can remove forage from large 

rangeland, reducing its suitability for livestock 

me herbicides are approved for use in BLM 

s for rangeland as well as fuels management 

phosate). 

short term, there would be minor impacts to 

ng as a result of mandatory restrictions 

h the use of herbicides. Livestock owners 

able to slaughter (for food) animals that 

med forage that has been treated by certain 

thin the time period specified on the 

. In addition, dairy animals would not be 

ated with certain chemicals 

me period specified on the label. 

Impacts of BLM-evaluated Herbicides 

According to BLM risk assessments, herbicide exposure 

scenarios of direct spray, spill, and indirect contact with 

foliage after direct spray do not pose a risk to small 

mammals (large mammals were not modeled, but have 

a smaller surface area to body weight ratio, so are less 

likely to be impacted by these scenarios than small 

mammals; Table 4-25). Several herbicides do pose a 

risk to large mammalian herbivores under a scenario of 

ingestion of food items contaminated by direct spray. 

Risks to livestock associated with each individual 

herbicide are presented below. See the tables and 

figures in Section 4 of the ERAs (ENSR 2005b-k) for 

each herbicide for risk information on applicable 

ecological receptor groups according to herbicide 

application method. Also, see Table 4-25 in this section 

for a summary of the typical degree of risk each of the 

BLM herbicides pose to possible livestock receptors 

under different routes of exposure. Large mammalian 

herbivores were evaluated for a scenario in which they 

ingest food items contaminated by direct spray of the 

herbicide. The receptor chosen for the large mammalian 

herbivore was a 154-pound mule deer. Chlorsulfuron, 

imazapic, and Overdrive® are the BLM-evaluated 

herbicides that would be most likely to be used in 

rangeland situations with grazing livestock. However, it 

is possible that other herbicides used nearby could 

impact livestock if they are transported off site. 

Bromacil 

Bromacil does not present a risk to small mammals via 

direct spray or indirect contact with foliage after direct 

spray (Table 4-25; ENSR 2005b). These scenarios are 

very conservative because they assume 100% 

absorption and because small mammals have a 

relatively larger surface area for absorption of herbicide. 

Therefore, it is unlikely that bromacil would affect 

larger livestock under these scenarios. No acute risk and 

low chronic risk were predicted for a large mammalian 

herbivore ingesting vegetation sprayed at the typical 

application rate, and low acute and moderate chronic 

risks were predicted for ingestion scenarios at the 

maximum application rate. Therefore, direct spray of 

bromacil onto rangeland could pose a risk to livestock 

consuming sprayed vegetation. The prediction of 

chronic risk to livestock suggests that caution is needed 

in applying this herbicide in forage areas, particularly 

over large areas. However, bromacil is a non-selective 

herbicide that is not registered for application on 

rangelands or other livestock grazing areas where some 

vegetative cover is desired, suggesting that under
TABLE 4-25

Risk Categories Used to Describe BLM-evaluated Herbicide Effects on Livestock and Wild Horses and Burros According 

BROM1 CHLOR DICAMBA DIFLU DIQUAT2 DIURON FLUR2 IMAZ OV

Application Scenario 

Typ3 Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ 

Direct Spray of Terrestrial WildlifeSmall mammal – 100% absorption 04 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Small mammal – 1st order dermal absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Indirect Contact with Foliage After Direct Spray Small mammal – 100% absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Small mammal – 1st order dermal absorption 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Ingestion of Food Items Contaminated by Direct SpraySmall mammalian herbivore – acute 0 L 0 0 0 0 0 0 0 L 0 L 0 0 0 0 0 Small mammalian herbivore – chronic 0 L 0 0 0 L 0 0 L M L M 0 0 0 0 0 Large mammalian herbivore – acute 0 L 0 0 0 L 0 0 0 M 0 L 0 0 0 0 0 Large mammalian herbivore – chronic L M 0 0 0 L 0 0 L M M H 0 0 0 0 L 

1 BROM = Bromacil; CHLOR = Chlorsulfuron; DIFLU = Diflufenzopyr; FLUR = Fluridone; IMAZ = Imazapic; OVER = Overdrive®; SULFM = Sulfometuron methyl; and 2 Diquat and fluridone are aquatic herbicides that would not be used in terrestrial areas. Therefore, exposure of livestock via direct spray is less likely than with the other herb3 Typ = Typical application rate; and Max = Maximum application rate.4 Risk categories: 0 = No risk (majority of RQs < most conservative LOC for livestock); L = Low risk (majority of RQs 1-10x most conservative LOC for livestock); M = 

100x most conservative LOC for livestock); and H = High risk (majority of RQs >100 most conservative LOC for livestock). The Risk Category is based on the risk lev

observed in any of the scenarios for a given exposure group and receptor type. The reader should consult the risk tables in Chapter 4 of the ERAs (ENSR 2005b-k) to d

result in the displayed level of risk for a given receptor group.

BLMVegetationTreatments Using Herbicides 4-127 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

typical use bromacil would not impact livestock. Any

risk would come from off-site transport of bromacil to

livestock grazing areas⎯a situation that could be

avoided by following SOPs, including the use of 

appropriate buffer zones to prevent drift to off-site

vegetation (see Vegetation section). Use of bromacil in

spot applications or over small areas is not likely to 

impact livestock. Based on label directions, there are no

restrictions on livestock use of treated areas.

Chlorsulfuron 

Risk quotients for mammalian receptors for all modeled

scenarios were below the conservative LOC of 0.1,

indicating that direct spray of chlorsulfuron is not likely 

to pose a risk to livestock (ENSR 2005c). Therefore, as 

chlorsulfuron is likely to be used in rangelands, this 

herbicide would primarily affect (positively or 

negatively) livestock through changes in the quality and

abundance of forage. If used properly, its use in range 

and pasture areas could benefit livestock over the long 

term by controlling unpalatable invasive plant species 

and promoting the establishment and growth of native 

plant species that may be more desirable for forage.

Based on label directions, there are no restrictions on 

livestock use of treated areas.

Dicamba 

Overdrive® is a formulation of dicamba and

diflufenzopyr; an analysis of risks to livestock for 

dicamba was conducted during preparation of the

Overdrive® ERA. However, an ERA report for dicamba

was not done by the BLM as part of this PEIS, although 

some information on dicamba is included in the

Overdrive® ERA. The Forest Service conducted an

ERA for dicamba, and the reader is encouraged to 

review this document (available at: 

http://www.fs.fed.us/foresthealth/pesticide/risk.shtml). 

The ingestion of food items contaminated by direct

spray of dicamba at the maximum application rate

would pose a low acute and chronic risk to large 

mammalian herbivores. Because dicamba is proposed

for use in rangelands and forestlands and does have

moderate residual activity, livestock may be at risk from

the application of this chemical, particularly if it is

sprayed throughout the range area. The use of dicamba

in rangeland could benefit livestock by controlling 

unpalatable invasive plant species and promoting the 

establishment and growth of native plant species that

may be more suited for forage. However, because

chlorsulfuron and imazapic are less risky to livestock

and have similar target species, these herbicides could 

be considered for use instead of dicamba, where 

possible. Based on label directions, there are no 

restrictions on livestock use of treated areas, other than

for lactating animals. 

Diflufenzopyr 

Risk quotients for terrestrial animals were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of diflufenzopyr is not likely to pose a risk to

livestock (ENSR 2005d). Diflufenzopyr is proposed for 

use with the active ingredient dicamba in the herbicide 

Overdrive®, which may be used in rangelands. Based on

label directions, there are no restrictions on livestock 

use of treated areas. 

Diquat 

For large mammalian herbivores ingesting food items

contaminated by diquat, there would be a low chronic 

risk if the food was directly sprayed at the typical

application rate, and a moderate acute and chronic risk 

if the food was sprayed at the maximum application rate 

(ENSR 2005e). This suggests that livestock could be at

risk from the short- and long-term consumption of 

vegetation contaminated by diquat. Although registered

for non-cropland and aquatic applications, use on public

lands would be limited to aquatic applications. Thus, the 

likelihood of exposure of livestock to diquat is minimal. 

Livestock that feed exclusively in riparian areas, where 

drift might impact riparian grasses, and/or drink water 

from ponds treated with diquat are potentially at risk. 

These unlikely scenarios were not directly modeled

because livestock will be removed from areas where

diquat is used to avoid potential exposure. 

Diuron

For scenarios involving large mammalian herbivores 

ingesting food items contaminated by diuron, there 

would be no acute risks but there would be high chronic 

risk if the food was directly sprayed at the typical

application rate, and moderate acute and chronic risk if 

the food was sprayed at the maximum application rate

(ENSR 2005f). However, because diuron is a nonselective herbicide, it is not likely to be used in

rangelands where some vegetative cover is desired;

therefore, its exposure to livestock would be limited. If 

typically foraged rangeland plants were protected from 

off-site transport of diuron, such as with appropriate 

buffer zones (see Vegetation section), livestock should 

not be at risk from off-site drift or surface runoff of 

diuron. Based on label directions, there are no

restrictions on livestock use of treated areas. 

BLM Vegetation Treatments Using Herbicides 4-128 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Fluridone 

Risk quotients for large terrestrial animals were below

the most conservative LOC of 0.1 for all scenarios 

(ENSR 2005g). These results indicate that accidental

direct spray or drift of this aquatic herbicide would be

unlikely to pose a risk to livestock. 

Imazapic

Risk quotients for terrestrial animals were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of imazapic would be unlikely to pose a risk to

livestock (ENSR 2005h). Therefore, since imazapic 

would likely be used in rangelands, it would primarily 

affect (positively or negatively) livestock through 

changes in the quality and abundance of forage. If 

applied properly, use of imazapic in range and pasture 

areas could benefit livestock over the long term by

controlling unpalatable invasive plant species and

promoting the establishment and growth of native plant 

species that may be more desirable for forage. Based on 

label directions, there are no restrictions on livestock 

use of treated areas. 

Overdrive®

Overdrive® poses a low chronic risk to large

mammalian herbivores that consume plants 

contaminated by direct spray at the typical application 

rate and a moderate risk for ingestion scenarios 

involving direct spray at the maximum application rate 

(ENSR 2005i). Because Overdrive® is proposed for use 

in rangelands and has moderate residual activity, 

livestock may be at risk from the application of this

chemical, particularly if it is sprayed throughout the 

range area. The use of Overdrive® in rangeland could

benefit livestock by controlling unpalatable invasive 

plant species and promoting the establishment and 

growth of native plant species that may be more suited 

for forage. However, because chlorsulfuron and 

imazapic are less risky to livestock and have similar 

target species, these herbicides could be considered for 

use instead of Overdrive®, where possible. Based on 

label directions, there are no restrictions on livestock 

use of treated areas. 

Sulfometuron Methyl 

Risk quotients for terrestrial animals were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of sulfometuron methyl would be unlikely to pose 

a risk to livestock (ENSR 2005j). This herbicide is

relatively non-selective, and is not registered for sites 

that are grazed. Thus, it should not impact livestock. 

Tebuthiuron 

For large mammalian herbivores ingesting food items

contaminated by tebuthiuron, there would be a low 

acute and chronic risk if the food was directly sprayed at

the maximum application rate (ENSR 2005k). The 

strength of this herbicide is its use as a habitat modifier 

in the BLM shrub reduction program; it is relatively 

non-selective but does not tend to harm grasses present. 

Therefore, impacts to livestock would be unlikely with 

intended use of this herbicide. According to the label for 

Spike 80DF, which has tebuthiuron as an active

ingredient, if a treated area is to be used for haying or 

grazing, no more than 5 pounds per acre of Spike 80DF 

should be applied, and the product should not be applied

more than once per year. 

Impacts of Forest Service-evaluated Herbicides

The following information for eight herbicides proposed

for use by the BLM is taken from ERAs performed by

the Forest Service to support assessment of the 

environmental consequences of using these herbicides 

in Forest Service vegetation management programs 

(risk assessment results available at SERA [2005a]). 

Because the Forest Service completed these ERAs prior 

to completion of the PEIS, the BLM would use these 

ERAs to assess the potential ecological impacts of using

these herbicides in future BLM vegetation management

activities. The BLM previously evaluated and approved 

these eight herbicides in an earlier EIS—Vegetation 

Treatment on BLM Lands in Thirteen Western States

(USDI BLM 1991a). As part of its risk assessments (see 

USDA Forest Service 2005), the Forest Service 

developed worksheets (see SERA 2005b), which

allowed the BLM to assess the risks of the herbicides 

using its own maximum application rates and LOCs 

(rather than the Forest Service rates and LOCs), and to 

parallel the BLM risk assessment process as much as 

possible. However, modeled risk scenarios for terrestrial

animals may be different than those used for the BLMevaluated herbicides, depending on the specificity of

available toxicity data. The assessment of impacts 

below is presented using the Forest Service upper 

estimates of HQs, to maximize the conservatism of the

assessment. In addition, it should be noted that the HQs 

developed by the Forest Service (as well as the BLM)

are already conservative for many reasons (e.g., 

assumption of 100% dermal absorption, assumption of 

100% of diet contaminated, use of most sensitive values 

for exposure and dose/response assessments). 2,4-D, 

BLM Vegetation Treatments Using Herbicides 4-129 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

clopy

triclopyr are th

are m

grazing livestock. However, it is possibl

herbicides used nearby

were t

2,4-D 

2,4-D does p

spray

Large livestock 

than sm

area to volu

Direct sp

prevented if ani

before sp

smaller livesto

water conta

risk fro

by 2,4-D at

moderate acut

face low acute risk, for bot

application r

cons

effect

although lon

vegetation 

signs of da

because large livestock eating large quanti

and other vege

2,4-D and

rangeland, this herbicide 

large application areas 

consu

According to l

anim

for 7 da

days

from

restrictions 

users o

apply

Clopyralid 

According to the Forest 

2004b), clopy

terre

involving clopyralid applicat

would be at low ri

small 

100% absorption of direct 

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-130 June 2007 

ogrammatic EIS 

ralid, glyphosate, metsulfuron methyl, and 

e Forest Service-evaluated herbicides that 

ost likely to be used in rangeland situations with 

e that other 

 could impact livestock if they 

ransported off site. 

resent some risk to livestock under direct 

 and ingestion scenarios (Table 4-26; SERA 1998). 

may face less risk from direct spray 

all livestock because they have a smaller surface 

me ratio over which to absorb the herbicide. 

ray impacts to livestock can largely be 

mals are removed from target areas 

raying 2,4-D. Small mammals, and perhaps 

ck, face low risk from the consumption of 

minated by a spill. In addition, livestock face 

m the consumption of vegetation contaminated 

 the application site: large mammals face 

e and chronic risk, and small mammals 

h the typical and maximum 

ates. Large livestock that primarily 

ume grasses are particularly susceptible to adverse 

s under the vegetation consumption scenarios, 

g-term consumption of contaminated 

may be unlikely if the vegetation shows 

mage. The risk assessment suggests that 

ties of grass 

tation are at risk from routine exposure to 

 because 2,4-D is considered for use in 

should not be applied over 

where livestock would only 

me contaminated food. 

abel directions for one formulation, dairy 

als should be kept out of areas treated with 2,4-D 

ys. Grass for hay should not be harvested for 30 

 after treatment. Meat animals should be removed 

 treated areas 3 days prior to slaughter. Similar 

may be in place for other formulations, but 

f 2,4-D should consult label directions before 

ing formulations of this active ingredient. 

Service risk assessment (SERA 

ralid is not likely to pose a risk to 

strial animals. However, there are a few scenarios 

ions under which livestock 

sk. For all modeled application rates, 

mammals are at low chronic and acute risk from 

spray and consumption of 

contaminated insects, and large mammals face risk low 

chronic and acute risks from consumption of 

contaminated vegetation at the typical and maximum 

application rates. Application of clopyralid at the 

maximum application rate also poses a low chronic risk 

to large mammals consuming on-site contaminated 

vegetation. The most likely livestock risk scenario 

would be the consumption of contaminated grass across 

large areas by large livestock, which could be avoided 

by restricting access of livestock to sprayed areas. In 

addition, all risks identified fall within the lowest risk 

category. 

According to label directions, there are no restrictions 

on grazing or hay harvest following application at 

labeled rates, and livestock should not be transferred 

from treated grazing areas to sensitive broadleaf crop 

areas without first allowing for 7 days of grazing on 

untreated pasture. 

Glyphosate 

Livestock face some risk from the use of glyphosate in 

rangelands. Direct spray of a small animal, assuming 

100% absorption, poses a low risk at the typical 

application rate and moderate risk at the maximum 

application rate (SERA 2003a). Smaller livestock, such 

as sheep and goats, are more likely to experience 

adverse effects from direct spray than larger livestock, 

such as cattle and horses, because of their larger surface 

area-to-body weight ratios. Direct spray impacts can 

largely be prevented if livestock are removed from the 

target area before spraying glyphosate. Large mammals 

consuming contaminated vegetation face low acute risk 

for scenarios involving the typical application rate, and 

moderate acute risk for scenarios involving the 

maximum application rate, and low chronic risk for 

scenarios involving maximum application rate. Small 

mammals face low risk from consumption of 

contaminated vegetation (fruit) sprayed at the maximum 

application rate. The most likely risk scenario is the 

consumption of contaminated vegetation (acute 

exposure), which is particularly risky for cattle because 

they consume large amounts of grasses, which contain 

higher herbicide residue levels than other herbaceous 

vegetation and seeds. Glyphosate is used in rangelands 

for the management of grasses and broadleaves, 

including woody species, and it is non-selective, 

suggesting that spot applications in rangeland would be 

the most appropriate use of this herbicide. Spot 

applications would reduce risks associated with 
TABLE 4-26

Risk Categories Used to Describe Forest Service-evaluated Herbicide Effects on Livestock 

and Wild Horses and Burros According to Exposure Scenario 

 2,4-D Clopyralid Glyphosate1 Hexazinone Imazapyr Metsulfuron  Typ2 Max Typ Max Typ Max Typ Max Typ Max Typ Max 

Acute/Accidental Exposures Direct spray, small mammal, 1st order absorption L3 L 0 0 0 0 0 L 0 0 0 0 Direct spray, small animal, 100% absorption M M L L L M L M 0 L 0 L Consumption of contaminated fruit, small mammal L L 0 0 0 L 0 L 0 0 0 0 Consumption of contaminated grass, large mammal M M L L L M L M 0 L 0 L Consumption of contaminated water, small mammal, spill L L 0 0 0 L 0 L 0 0 0 0 Consumption of contaminated water, small mammal, stream 0 0 0 0 0 0 0 0 0 0 0 0 Chronic Exposures Consumption of contaminated vegetation, small mammal, on-site 0 0 0 0 0 0 0 0 0 0 0 0 Consumption of contaminated vegetation, small mammal, off-site 0 0 0 0 0 0 0 0 0 0 0 0 Consumption of contaminated vegetation, large mammal, on-site M M 0 L 0 L L M 0 0 0 0 Consumption of contaminated vegetation, large mammal, off-site 0 0 0 0 0 0 0 0 0 0 0 0 Consumption of contaminated water, small mammal 0 0 0 0 0 0 0 0 0 0 0 0 1 Risk categories are the same for both evaluated formulations.2 Typ = Typical application rate; and Max = maximum application rate.3 Risk categories: 0 = No risk (HQ < LOC); L = Low risk (HQ = 1 to 10 x LOC); M = Moderate risk (HQ = 10 to 100 x LOC); and H = High risk (HQ > 100 LOC

upper estimates of hazard quotients and the BLM LOCs of 0.1 for acute scenarios and 1.0 for chronic scenarios. The reader should consult the text of this section 

risk assessments to evaluate risks at central estimates of hazard quotients. 

BLMVegetationTreatments Using Herbicides 4-131 June 2007 

FinalProgrammaticEIS
ENVIRONMENTAL CONSEQUENCES

consumption of contaminated vegetation, as fewer nontarget areas would be impacted by direct spray or spray 

drift. Based on label directions, there are no restrictions 

on livestock use of treated areas. 

Hexazinone 

Applications of hexazinone at the typical and maximum 

application rates would pose a low to moderate risk to

livestock under several exposure scenarios (SERA 

1997). Small mammals face low risk from direct spray 

at the maximum application rate, assuming 1st order 

dermal absorption, and low to moderate risk assuming 

100% dermal absorption. Acute exposure through 

consumption of contaminated vegetation sprayed at the 

maximum application rate poses a low risk to small

mammals; and acute and chronic exposure through 

consumption of contaminated vegetation poses a 

moderate risk to large mammals. Also, acute exposure 

through consumption of contaminated water sprayed at

the maximum application rate poses a low risk to small

mammals. It appears that livestock are at risk from the

application of hexazinone, but if food and water sources

are not contaminated, risks are reduced, as direct spray 

can be avoided by removing livestock from the target

area prior to treatment. Contamination of food and

water sources could be minimized by utilizing spot

applications of hexazinone at the typical application 

rate. Because hexazinone is used for woody species, it is 

not likely to be applied in rangelands where invasive 

plants are usually grasses or herbaceous vegetation. In 

addition, hexazinone is semi-selective, and is typically

only applied in spot applications; therefore, risks to

livestock under normal application may be lower than

those predicted by the risk assessment. According to

label directions, livestock should not be grazed, nor

forage or hay cut, on treated areas for 60 days after 

application. 

Imazapyr

Applications of imazapyr at the typical application rate

should not pose a risk to livestock, assuming that

livestock consume primarily vegetation (SERA 2004d). 

Applications at the maximum application rate, however, 

would pose a low risk to livestock under a couple 

exposure scenarios: direct spray of a small animal and

consumption of contaminated vegetation by a large 

mammal. Imazapyr is not registered for use in 

rangelands; therefore, it is unlikely that impacts via

direct spray or consumption of contaminated vegetation

would occur. The chance of adverse effects could be

further minimized by removing livestock from areas 

near application sites prior to spraying and by observing

appropriate buffer distances from rangeland vegetation 

when applying imazapyr (see Vegetation section). 

Based on label directions, there are no restrictions on 

livestock use of treated areas.

Metsulfuron Methyl 

Livestock face minimal risk from the application of 

metsulfuron methyl. None of the HQs estimated for 

exposure to metsulfuron methyl exposure when applied

at the typical application rate indicate risk to any of the 

terrestrial animal receptors (SERA 2004e). Applications 

at the maximum application rate pose a low risk to 

small animals under scenarios involving 100%

absorption of direct spray and to large mammals under 

scenarios involving consumption of contaminated

vegetation. Metsulfuron methyl is registered for use in 

rangeland, but impacts to livestock are unlikely if the

typical application rate is used. If the maximum 

application rate is used, impacts to livestock can be 

avoided by removing livestock from application areas 

prior to spraying and by limiting the size of the

application area or restricting access of livestock to

recently sprayed areas to prevent consumption of large

amounts of sprayed vegetation. Based on label

directions, there are no restrictions on livestock use of 

treated areas for application rates of 12

/3 ounces active

ingredient per acre or less. If greater amounts of

metsulfuron methyl are used, forage grasses may be cut

for hay, fodder, or green forage and fed to livestock, 

including lactating animals, 3 days after treatment. 

Picloram 

Application of picloram is not likely to impact

livestock. Most of the HQs for the evaluated scenarios 

of picloram exposure were below the LOC for both the

typical and maximum application rates (SERA 2003b). 

Under two scenarios, HQs were above the LOC, 

indicating a low to moderate risk for applications at the

typical and maximum application rates: 100% 

absorption of direct spray by a small animal and acute

exposure through consumption of contaminated

vegetation by a large mammal. Picloram is registered

for use in rangeland, and can be applied over large 

areas, as its primary targets are broadleaf and woody 

species. Therefore, it might be used to manage certain

broadleaved plants without impacting native or 

desirable grasses. Impacts to livestock can be avoided

by removing animals from application areas prior to 

spraying picloram and by limiting the size of the 

application area or restricting livestock access to

recently sprayed areas to prevent consumption of large

amounts of sprayed vegetation. 

BLM Vegetation Treatments Using Herbicides 4-132 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Picloram has a number of restrictions on use in areas 

grazed by livestock or used for cutting hay. In general,

livestock should not be grazed on treated areas, nor 

should hay be cut, for 2 weeks after treatment. 

Triclopyr 

Triclopyr presents some risk to livestock, particularly 

through the consumption of contaminated vegetation

(SERA 2003c). Because risk categories determined

using calculated HQs for the two evaluated formulations

of triclopyr (triclopyr acid and triclopyr BEE) are the 

same, no differentiation will be made between these two 

formulations in this section. The following scenarios 

pose a low risk for applications at the typical application 

rate, and moderate risk for applications at the maximum

application rate: first-order and 100% absorption of 

direct spray by a small mammal, and acute and chronic 

exposure through consumption of on-site contaminated

vegetation by a large mammal. In addition, for 

applications at the maximum application rate, there

would be a low risk associated with exposure through 

acute consumption of water contaminated by a spill by

the small mammal and chronic exposure through 

consumption of off-site contaminated vegetation by the 

large mammal. No risk is predicted for small mammals 

as a result of acute or chronic exposure through 

consumption of contaminated vegetation or water. 

Triclopyr can be used in rangelands to selectively 

manage woody species without impacting native or 

desirable grasses. It also has low residual activity. 

Impacts to livestock can be avoided by removing 

animals from application areas prior to spraying and by

limiting the size of the application area or restricting 

access of livestock to recently sprayed areas to prevent 

consumption of large amounts of sprayed vegetation. 

There are few grazing restrictions for triclopyr, except 

for lactating dairy cattle. Hay should not be harvested 

within 14 days of application. Although cattle can

graze at any time they would be removed from treated

areas at least 3 days prior to slaughter. 

Impacts of Other Herbicides Currently Available for 

Use 

2,4-DP, asulam, atrazine, fosamine, mefluidide methyl, 

and simazine were approved for use in the earlier BLM

EISs. 2,4-DP could be used in forested rangeland, but 

would not be used in areas where livestock graze. It has 

low toxicity to mammals. Asulam is of low toxicity to 

mammals, but livestock should not graze in treated

areas or be fed forage from treated areas. It would

primarily be used in the control of brackenfern on

forested rangelands (Information Ventures, Inc. 1995a). 

Atrazine could be used for vegetation treatments in 

conifer plantations, but would not be used in forested or 

other rangelands where livestock might come in contact

with the herbicide. It is slightly to moderately toxic to 

mammals (Information Ventures, Inc. 1995b; Extension 

Toxicology Network 1996e). Fosamine does not have a

rangeland registration and would not be used where 

livestock graze. It is practically nontoxic to mammals 

(USEPA 1995). Mefluidide would not be cost-effective 

to use on rangelands. It is of low to moderate toxicity to

mammals (Information Ventures, Inc. 1995c). Simazine 

could be used by the BLM on Christmas tree 

plantations, but would likely not be used where 

livestock graze. Simazine has low toxicity to most

mammals, although sheep and cattle are more sensitive

to simazine than other mammals, and a dose as low as 

500 mg/kg can be fatal (Information Ventures, Inc. 

1995d). The BLM has not used any of these herbicides, 

except fosamine (< 50 acres annually), since 1997, and

does not plan to utilize them in the near future. 

Impacts by Alternative 

The following sections discuss the expected effects of

each of the five alternatives on livestock, and compare

the effects expected under each alternative with those

expected under the other alternatives. These effects may 

vary depending on the percentage of acres treated using 

different application methods and different herbicides, 

as well as on the size of treatment events. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation treatment programs in

14 western states, and would be able to use 20

herbicides previously approved under earlier RODs. 

Herbicide use under the No Action Alternative could

impact livestock over an estimated 305,000 acres. 

Impacts to livestock (positive and negative) would be 

similar in nature those that have occurred in the past 10

years. Negative impacts to livestock may be lower than

under the other herbicide-use alternatives because fewer 

total acres would be treated using herbicides. However, 

long-term positive impacts on livestock communities 

(i.e., improvements in rangeland forage) could be lower 

under this alternative, as well. Invasive plant 

populations would likely continue to expand at the 

current rate or more quickly, potentially increasing 

damage to desirable native forage, and the abundance of

unpalatable or toxic plants. 

BLM Vegetation Treatments Using Herbicides 4-133 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Because the new herbicides proposed in this PEIS 

(diquat, fluridone, imazapic, and Overdrive

®) would not 

be used under this alternative, risks to livestock would 

be different than under the other alternatives. Fluridone 

and imazapic do not present any risks to livestock in

modeled scenarios (similar to chlorsulfuron, 

metsulfuron methyl, and sulfometuron methyl), and

Overdrive® poses low to moderate risk to large 

livestock under chronic exposure scenarios in which the

animal ingests contaminated vegetation over a long time 

period. Diquat is fairly toxic to livestock, particularly 

under food ingestion scenarios (similar to 2,4-D and

diuron). However, because diquat would be used by the 

BLM as an aquatic herbicide, frequent exposure to 

livestock would not be expected. Therefore, the No

Action Alternative would prevent the BLM from using

a greater repertoire of herbicides that are not injurious to

terrestrial animals, possibly resulting in greater per area

risks to livestock than under the other alternatives if 

more injurious herbicides (e.g., 2,4-D, bromacil, diuron, 

tebuthiuron, triclopyr) were used instead of safer 

alternatives, as well as decreasing the possibilities of 

more effective rangeland improvements. Conversely,

prohibiting the use of diquat, particularly in rangeland 

riparian areas, could result in somewhat lower per area

risk to livestock than under the other alternatives. 

2,4-DP, asulam, atrazine, fosamine, mefluidide, and 

simazine were approved for use in the earlier BLM

EISs, but the BLM has not used any of these herbicides, 

except fosamine (< 50 acres annually) since 1997, and 

does not plan to utilize them in the near future. None of

these herbicides would normally be used in rangeland 

treatments where livestock might come into contact 

with the chemical. Instead, the BLM would use other 

herbicides, including triclopyr, sulfometuron methyl, 

bromacil, diuron, and Overdrive®, which are effective in 

controlling weeds and invasive vegetation, but have less 

risk to livestock. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

The Preferred Alternative would result in the treatment

of approximately 932,000 acres in 17 western states. In

addition to the 14 previously approved herbicides, the 

BLM would be able to use the four new herbicides 

evaluated in this PEIS. This alternative would result in 

the most extensive effects to livestock (both negative

and positive) because it proposes the most acres for 

treatment (3 times the acreage that would be treated 

under the No Action Alternative). The extent of positive 

and negative impacts to livestock would depend on the

relative amount each of the herbicides was used,

whether they would be applied in rangeland

environments, and the method of application. The

chance for negative impacts would be highest if diuron, 

diquat, bromacil and/or 2,4-D were used extensively.

However, diquat would be used by the BLM as an 

aquatic herbicide, and bromacil and diuron are nonselective herbicides that are not likely to be used 

extensively in rangelands. If these herbicides were used

in restricted scenarios, as proposed, and other herbicides 

were used effectively to increase the abundance of 

native forage relative to unpalatable weeds, positive 

impacts to livestock could outweigh negative impacts. 

Furthermore, the ability to use the four new herbicides 

(diquat, fluridone, imazapic, and Overdrive

®) as well as 

future herbicides that become registered with the

USEPA would allow BLM managers more options in

choosing herbicides that best match treatment goals and

application conditions and are less toxic. As a result, 

there could be an increase in per capita benefits and a

reduction in overall per capita risks to livestock (three

of the four new herbicides present little to no risk to 

livestock), and an increase in habitat and ecosystem

benefits from treatment. This alternative would also 

reduce risks and negative impacts associated with other 

vegetation management methods (e.g., risk of escaped 

prescribed fires; see the PER). 

Alternative C – No Use of Herbicides 

Under Alternative C, livestock would not be affected by 

herbicide use. Primary impacts would stem from other 

vegetation treatment methods (see the PER). Positive 

benefits to rangelands as a result of vegetation 

management could be reduced under this alternative, as 

certain invasive species are only effectively controlled 

by herbicides, and in some situations other methods are 

impractical due to cost, time, or public concerns. For 

example, mechanical and manual methods are 

impractical over large land areas, which are more

effectively treated by broadcast herbicide applications. 

In addition, it is often difficult to eradicate some species 

(e.g., rabbitbrush, honey mesquite, sand shinnery oak, 

tree cholla), by means other than herbicide application. 

Similarly, pre-emergent herbicides that persist in the

soil are the most effective means of controlling invasive

plants with seeds that remain viable for long periods of

time. 

Under this alternative, without the use of herbicides, 

invasive plant populations would likely continue to 

spread, possibly at increasing rates. The spread of

invasive plant populations would cause further damage 

to susceptible native plant communities, including 

BLM Vegetation Treatments Using Herbicides 4-134 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

rangeland communities that provide forage for 

livestock, particularly in situations where other 

treatment methods would not be effective or feasible 

(e.g., large tracts of rangeland or grassland dominated

by invasive, resprouting shrubs; or areas without 

enough fine fuels to carry prescribed fires). The spread

of invasive plant populations would likely have 

deleterious effects on livestock. Rangeland that contains 

excessive or unpalatable brush cover is less useful for 

grazing and has reduced carrying capacity for domestic 

livestock. Similarly, capacity for cattle grazing 

decreases proportionately with loss of forage caused by 

weed infestation. Economic returns in terms of

improved grazing value typically exceed herbicide 

treatment costs on lands where herbicides are used to 

control weeds (Olson 1999). In addition, acres infested

by noxious weeds that are toxic to livestock, including

common tansy, leafy spurge, Russian knapweed, 

common St. Johnswort, tansymustard, and yellow 

starthistle, would increase; in contrast, these species 

would be targeted by the BLM for herbicide treatments 

under the other alternatives. 

Alternative D – No Aerial Applications 

Alternative D would be the same as the Preferred

Alternative as far as herbicides that could be used, and 

areas that could be treated. Therefore, both alternatives 

would be equally likely to have both positive and 

negative effects on livestock and rangeland. The BLM 

would be able to choose from a suite of currentlyapproved herbicides and herbicides that could be 

approved under this PEIS, or in the future. However, 

this alternative would not allow the BLM to apply 

herbicides aerially. Fewer acres would be treated 

(535,000 acres) because some large areas, including 

rangelands, cannot be effectively treated by ground 

application methods. This alternative would 

substantially reduce the impacts of off-site drift to 

livestock, an exposure scenario that is not specifically 

modeled for most herbicides (consumption of 

contaminated vegetation off-site was modeled for most

of the Forest Service herbicides, with no risk 

demonstrated to livestock for any of these herbicides, 

except triclopyr when applied at the maximum 

application rate). Conversely, without the option to 

spray herbicides aerially, large areas of rangeland may 

remain untreated under Alternative D, and which could 

negatively impact livestock habitat and forage in these 

areas over the long term. 

Under this alternative, long-term negative impacts to

rangeland could be greater than any potential short-term

negative effects to livestock that would result from

aerial applications, particularly given that livestock 

would be removed from rangeland application areas 

before aerial spraying. Furthermore, most of the 

herbicides that are potentially damaging to livestock 

(e.g., bromacil, diquat, diuron, glyphosate, hexazinone,

tebuthiuron) are not likely to be applied aerially in

rangelands, and aerial spraying of other damaging 

herbicides (e.g., 2,4-D, Overdrive®) could be avoided. 

In addition, direct and indirect impacts from other 

vegetation treatment options could increase if these 

methods were used more extensively to compensate for 

the reduced number of acres treated by herbicides (see 

PER). 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Approximately 466,000 acres would be treated under 

Alternative E, which is slightly less than the acreage

that would be treated under Alternative D, and less than

half of the acreage that would be treated under the 

Preferred Alternative, but is still an increase from the

average annual treatment acreage that has occurred over 

the past 8 years and would likely occur under the No

Action Alternative. Herbicide-related impacts to

livestock would be lower under this alternative than

under the Preferred Alternative because fewer acres 

would be treated with herbicides, and additional

protective standards would be required during herbicide

treatment (e.g., preferential use of spot rather than 

broadcast applications, preferential treatment of small

versus large infestations). 

Sulfonylurea herbicides and other ALS-inhibiting 

herbicides (e.g., chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, sulfometuron methyl) block the 

synthesis of amino acids that are required for protein

production and cell growth, thereby resulting in plant

death. ALS-inhibiting herbicides would not be used

under this alternative because data suggest they have the 

potential to damage off-site native and crop plant

species under the right conditions of environment and 

application. These herbicides are biologically active at

low concentrations, and are applied at lower application 

rates than other herbicides to manage target plants. It is 

uncertain whether use of these herbicides would result 

in fewer cases of unintended damage to livestock and 

rangeland due to lower application rates, or more cases

due to the high potency of the herbicides and their 

persistence. In 1981, the Environmental Effects 

Division of the USEPA recommended against 

registering sulfonylurea herbicides because they persist

for long periods of time in the environment and they

cannot be detected at low levels. However, risk

BLM Vegetation Treatments Using Herbicides 4-135 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

assessments did not predict risk to livestock for any of 

the ALS-inhibiting herbicides, when applied at the 

typical application rate, under any of the modeled 

scenarios, suggesting that prohibiting the use of these

herbicides would not benefit livestock and could

indirectly harm livestock if more toxic herbicides were

used in their place. 

Alternative E incorporates other management practices 

that would be likely to have positive impacts on

livestock and rangelands. Alternative E would limit the

use of broadcast applications, which would reduce the 

possible risks to livestock associated with off-site drift

and consumption of vegetation across large areas. 

However these applications would be available for use

in appropriate situations (i.e., where no other method is 

practical, and susceptible non-target plant species and 

aquatic areas are distant from the application area),

which would result in some ecosystem benefits from

larger-scale herbicide applications. While per-treatment

ecosystem benefits may be greater under Alternative E 

than under the other herbicide-use alternatives as a 

result of this ecosystem-based management approach, 

overall positive vegetation and ecosystem benefits (that 

cannot be attained by other treatment methods) across 

the western states would be lower under this alternative 

because of the relatively small treatment acreages and

the inability to use certain practices in situations that

might require their use (e.g., use of ALS-inhibitor 

herbicides on highly aggressive weeds). For example, 

imazapic, which has been shown to be effective in 

treating downy brome and leafy spurge, would be 

unavailable under this alternative. The BLM would also

be unable to use chlorsulfuron and metsulfuron methyl

to control yellow starthistle and several species of thistle 

that are harmful to livestock. 

Mitigation for Herbicide Treatment 

Impacts 

The following actions would greatly reduce the risk of 

herbicide applications to livestock: 

• Apply diuron, glyphosate, hexazinone, 

tebuthiuron, and triclopyr at the typical, rather 

than maximum, application rate to minimize

risks to livestock. 

• Do not apply 2,4-D, bromacil, dicamba, diuron, 

Overdrive®, picloram, or triclopyr across large 

application areas, where feasible, to limit

impacts to livestock, particularly through the 

contamination of food items. 

• Where feasible, limit glyphosate and 

hexazinone to spot applications in rangeland to 

avoid contamination of food items. 

• Do not aerially apply diquat directly to 

wetlands or riparian areas. 

• Do not apply bromacil or diuron in rangelands, 

and use appropriate buffer zones (see 

Vegetation section in this chapter) to limit

contamination of off-site rangeland vegetation. 

Wild Horses and Burros 

Introduction 

The BLM, in conjunction with the Forest Service, 

manages wild horses and burros on BLM- and Forest

Service-administered lands through the Wild FreeRoaming Horse and Burro Act of 1971. Animals are 

managed within 201 Wild Horse and Burro herd 

management areas, with the goal of maintaining the 

natural ecological balance of public lands as well as the

ability to support multiple uses. Public lands inhabited

by wild horses or burros are closed to grazing by

domestic horses and burros under permit or lease. In FY 

2005, wild horse and burro populations on public lands

totaled over 31,760 animals, with nearly half of these 

animals living in Nevada (Table 3-7). Another 25,000

animals are held in holding pens. The population of 

wild horses and burros is approximately 4,000 animals

above the Appropriate Management Level (AML) of

27,500. The AML is an estimate of the number of wild 

horses and burros that public lands can support while 

maintaining a thriving natural ecological balance (USDI 

BLM 2006c, d). 

The proposed herbicide vegetation management

activities could affect wild horses and burros through

exposure to chemicals that could harm their health, or 

through changes in vegetation that could positively or 

negatively alter the carrying capacity of the HMAs. 

Adverse impacts to wild horses and burros could

include direct harm to wild horses and burros and a 

reduction in the availability or quality of forage in

HMAs (decreasing the carrying capacity of the HMAs).

Alternately, herbicide vegetation management activities

could improve the amount and quality of forage, 

potentially increasing the carrying capacity of the 

HMAs. 

BLM Vegetation Treatments Using Herbicides 4-136 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Scoping Comments and Other Issues 

Evaluated in the Assessment 

This section aims to contribute to the understanding of 

the impacts of herbicides on non-target species, 

focusing on wild horses and burros. The evaluation of 

the direct impacts of herbicides to wild horses and 

burros would help in the selection of less-toxic 

herbicides where feasible, a scoping concern identified 

by numerous respondents. The alternatives present a 

variety of herbicide use levels (including no use) for 

evaluation of relative positive and negative effect on 

wild horses and burros, and one of the alternatives will

evaluate the relative impacts of aerial versus ground

application; these were key issues identified in the 

scoping process. Evaluation of the effects of herbicide 

use on wild horses and burros is in concert with the goal 

identified by some respondents of improving the 

management of public lands for multiple use and public

benefit. 

Standard Operating Procedures 

Herbicide use carries a potential risk to wild horses and

burros. However, risks can be minimized by following

certain SOPs, which can be implemented at the local

level according to specific conditions (see Table 2-8). 

These SOPs include the following: 

• Use herbicides of low toxicity to wild horses

and burros, where feasible. 

• Remove wild horses and burros from identified

treatment areas prior to herbicide application, 

in accordance with label directions for 

livestock. 

• Take into account the different types of 

application equipment and methods, where 

possible, to limit the probability of 

contaminating non-target food and water 

sources. 

These procedures would help to minimize impacts to

wild horses and burros and rangeland on western public 

lands to the extent practical. As a result, long-term

benefits to wild horses and burros from the control of 

invasive species would likely outweigh any short-term 

negative impacts to these animals associated with

herbicide use. 

Impacts Assessment Methodology 

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM and Forest Service to 

assess the impacts to wild horses and burros from the

use of herbicides (ENSR 2005b-k; SERA 2005a). Risks 

to wild horses and burros were not specifically 

evaluated in these documents, which focused on risks to 

plants, fish, and wildlife. However, results from the

evaluation of large terrestrial animal herbivores can be 

applied to wild horses and burros (i.e., results for large

herbivores [154 pound mule deer] are used to evaluate

risks to common grazing animals on public lands, 

including wild horses and burros). The ERA methods 

are summarized in the Wildlife Resources section of 

this chapter. Methods used by the BLM are presented in

detail in the Vegetation Treatments Programmatic EIS

Ecological Risk Assessment Protocol (ENSR 2004) and

in Appendix C. Methods used by the Forest Service can 

be viewed on the Internet at

http://www.fs.fed.us/r6/invasiveplant-eis/. 

Summary of Herbicide Impacts 

The extent of direct and indirect impacts to wild horses 

and burros would vary by the effectiveness of herbicide 

treatments in controlling target plants (that are not used

as forage) and promoting the growth of native 

vegetation (that is used as forage); the extent and 

method of treatment (e.g., aerial vs. ground); the 

chemical used (e.g., toxic vs. non-toxic, selective vs. 

non-selective); the physical features of the terrain (e.g., 

soil type, slope); the weather conditions (e.g., wind 

speed); and the time of year (e.g., newborn horses and

burros would be susceptible during foaling season, with 

March through June being a critical period) at the time

of application. Potential adverse direct effects to 

individual animals as a result of exposure to herbicides 

include death, damage to vital organs, change in body

weight, decreases in healthy offspring, and increased 

susceptibility to predation. 

Adverse indirect effects could include reductions in

forage amount and preferred forage type. Additionally, 

wild horses and burros may move out of herd

management areas and onto lands that are not legally

designated for wild horse and burro management. 

Possible positive effects include improvement in the 

quality and amount of forage and improvement in

general habitat conditions. The impacts of herbicide use 

on wild horses and burros would depend directly on the 

sensitivity of each species to the particular herbicides

used and the pathway by which the individual animal is 

BLM Vegetation Treatments Using Herbicides 4-137 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

exposed to the herbicide, and indirectly on the degree to

which a species or individual is positively or negatively 

affected by changes in herd management area 

conditions. 

Wild horses and burros would have a greater chance of 

exposure to herbicides—either via direct contact with

the herbicide upon application or indirect contact via 

dermal contact with vegetation or ingestion of 

vegetation—if their range extent was partially or

completely sprayed. However, it is unlikely that the 

entire range of a horse or burro herd would be sprayed,

as these animals are wide ranging, and herd 

management areas are often larger than 10,000 to 

100,000 acres (most treatments [77%] would be less 

than 1,000 acres). 

Wild horses and burros may also experience greater 

impacts under conditions where herbicide transport is 

more likely, such as in areas where herbicides are

aerially sprayed adjacent to herd management areas, dry 

areas with high winds, or areas with extensive rainfall

and porous soils. However, these scenarios were not

modeled. 

The BLM and Forest Service risk assessments

suggested several possible common impacts of

herbicides to wild horses and burros (USDA Forest

Service 2005; ENSR 2005b-k; SERA 2005a). Wild 

horses and burros, which likely consume large 

quantities of grass, are at relatively greater risk for harm

than smaller wildlife or wildlife that feed on other 

herbaceous vegetation, seeds, or fruits, which have less 

herbicide residue than grass (Fletcher et al. 1994; 

Pfleeger et al. 1996). This is especially evident in the 

sections of the BLM ERAs that examine risk levels of 

large mammalian herbivores. However, harmful doses

of herbicide may be unlikely unless the animal forages 

exclusively within the treatment area for an entire day,

suggesting that smaller treatments may be more 

appropriate for herd management areas in cases where 

risk to herbivores from the consumption of 

contaminated vegetation is predicted by the ERAs. 

In cases where herbicide treatments are able to reduce

the cover of noxious and unpalatable weeds on grazed 

lands and replace them with more palatable native 

plants, there would be benefits to wild horses and burros 

associated with increased availability and quality of

forage. An increase in the amount of forage within a

given herd management area could increase the carrying

capacity of that area. Many herd management areas are

currently overburdened with wild horse and burro 

populations that exceed the appropriate management

level. 

Herbicide use, or a combination of herbicide use and 

another treatment method, may be the most effective 

means of controlling or eradicating some invasive plant

species. Noxious weed infestations can greatly reduce

the land’s carrying capacity for domestic wild horses 

and burros, which tend to avoid weeds that have low 

palatability as a result of defenses such as toxins, spines, 

and/or distasteful compounds (e.g., thistle [Olson 

1999]). In addition, some noxious weeds (e.g., horsetail, 

wild mustard, poison hemlock, tansy ragwort, yellow 

starthistle, and common St. Johnswort) are poisonous to

horses. Grazing may ultimately be an effective means of

managing invasive plants in HMAs. However, if

vegetation is overgrazed (e.g., as a result of HMAs 

supporting horses and wild burros in excess of the 

AML), another method, such as herbicide treatment, is

required to return vegetation to a more desirable 

composition, followed by grazing within the carrying

capacity of the HMA. The success of weed removal 

would determine the level of benefit of the treatments 

over the long term. 

Treatments that reduce the risk of future catastrophic 

wildfire through fuels reduction would also benefit wild 

horses and burros. Weeds of concern that could be

found in rangelands include downy brome, medusahead, 

halogeton, rabbitbrush, diffuse knapweed, Russian

thistle, and perennial pepperweed. Uncontrolled, high 

intensity wildfires can remove forage from large tracts

of rangeland, reducing its suitability for wild horse and

burro grazing. Some herbicides are approved for use in

BLM programs for rangeland as well as fuels 

management (e.g., glyphosate, imazapic, sulfometuron

methyl).

Impacts of BLM-Evaluated Herbicides

BLM risk assessments indicate that herbicide exposure 

scenarios of direct spray and spill and indirect contact 

with foliage after direct spray would pose a risk to small

mammals (large mammals were not modeled, but have 

a smaller surface area-to-body weight ratio, and are less 

likely to be impacted under these scenarios than small 

mammals). Several herbicides would pose a risk to large 

mammalian herbivores under the scenario of ingestion 

of food items contaminated by direct spray. Specific 

estimated risks to wild horses and burros from each

individual herbicide are presented below. See the tables 

and figures in Section 4 of the ERAs (ENSR 2005b-k) 

for each herbicide for risk information on applicable

ecological receptor groups according to herbicide 

BLM Vegetation Treatments Using Herbicides 4-138 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

application method. Also, see Table 4-25 for a summary 

of the typical degree of risk each of the BLM herbicides 

poses to wild horse and burro receptors under different

routes of exposure. Small mammals were used in direct

spray and indirect contact with directly sprayed foliage 

scenarios. Because small mammals have a relatively 

larger surface area for absorption of herbicide and 

because 100% absorption is assumed, it is unlikely that

wild horses and burros would be at more risk than small

mammals. Large mammalian herbivores were used in

the ingestion of food items contaminated by direct spray 

scenario. The receptor chosen for the large mammalian

herbivore was a 154-pound mule deer. Chlorsulfuron, 

imazapic, and Overdrive® are the BLM-evaluated 

herbicides that are most likely to be used in rangeland 

situations with grazing wild horses and burros; 

however, it is possible that other herbicides used nearby

could impact wild horses and burros if they were 

transported off site. 

Bromacil 

Bromacil does not present a risk to small mammals via 

direct spray or indirect contact with foliage after direct

spray (ENSR 2005b). These scenarios are very 

conservative because they assume 100% absorption, 

and small mammals have a relatively larger surface area

for absorption of herbicide than large mammals.

Therefore, it is unlikely that bromacil would affect

larger wild horses and burros under these scenarios. No 

acute risk and low chronic risk were predicted for a 

large mammalian herbivore ingesting vegetation

sprayed at the typical application rate, and low acute 

and moderate chronic risks were predicted for ingestion

scenarios at the maximum application rate. Therefore,

direct spray of bromacil onto rangeland could pose a 

risk to wild horses and burros that consume sprayed

vegetation. The predicted chronic risk to wild horses 

and burros suggests that caution is needed in applying

this herbicide in HMAs, particularly over large areas. 

However, because bromacil is a non-selective herbicide

and is registered for non-cropland applications, it is not

likely to be used in HMAs where vegetative cover is 

desired, suggesting that under typical use bromacil

would not impact wild horses and burros. Any risk

would come from off-site transport of bromacil to wild

horse and burro grazing areas⎯a situation that could be

avoided by following SOPs, including the use of 

appropriate buffer zones to prevent drift to off-site

vegetation (see Vegetation section of this chapter). Use 

of bromacil in spot applications or over small areas 

would be unlikely to impact wild horses and burros. 

Chlorsulfuron 

Risk quotients for mammalian receptors for all modeled

scenarios were all below the most conservative LOC of 

0.1, indicating that direct spray of chlorsulfuron would

not likely pose a risk to wild horses and burros (ENSR

2005c). Therefore, as chlorsulfuron may be used in

HMAs, this herbicide would primarily affect (positively 

or negatively) wild horses and burros through changes 

in the quality and abundance of forage. If used properly,

its use in range and pasture areas could benefit wild 

horses and burros over the long term by controlling

unpalatable invasive plant species and promoting the 

establishment and growth of native plant species that

may be more desirable for forage. 

Dicamba 

Overdrive® is a formulation of dicamba and

diflufenzopyr; an analysis of risks to horses and burros 

for dicamba was conducted during preparation of the 

Overdrive® ERA. However, an ERA report for dicamba

was not done by the BLM as part of this PEIS, although 

some information on dicamba is included in the

Overdrive® ERA. The Forest Service conducted an

ERA for dicamba, and the reader is encouraged to 

review this document (available at 

http://www.fs.fed.us/foresthealth/pesticide/risk.shtml). 

The ingestion of food items contaminated by direct

spray of dicamba at the maximum application rate poses 

a low acute and chronic risk to large mammalian

herbivores. Because dicamba is proposed for use in

rangelands and forestlands and has moderate residual

activity, wild horses and burros may be at risk from the 

application of this chemical, particularly if it is sprayed

throughout the range area. The use of dicamba in 

rangeland could benefit wild horses and burros by

controlling unpalatable invasive plant species and

promoting the establishment and growth of native plant 

species that may be more suited for forage. However, 

because chlorsulfuron and imazapic are less risky to

wild horses and burros and have similar target species, 

these herbicides could be considered for use instead of 

dicamba, where possible. 

Diflufenzopyr 

Risk quotients for terrestrial animals were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of diflufenzopyr would not likely pose a risk to

wild horses and burros (ENSR 2005d). Diflufenzopyr is

proposed for use with the active ingredient dicamba in 

BLM Vegetation Treatments Using Herbicides 4-139 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

the herbicide Overdrive®, which may be used in

rangelands. 

Diquat 

Ingestion of food items contaminated by direct spray 

would pose a low chronic risk to large mammalian

herbivores if diquat was applied at the typical

application rate, and moderate acute and chronic risk if 

applied at the maximum application rate (ENSR 2005e). 

This suggests that wild horses and burros could be at 

risk from the short- and long-term consumption of 

vegetation contaminated by diquat. However, because

diquat is an aquatic herbicide that is not proposed for 

use in terrestrial areas, the likelihood that wild horses 

and burros would be exposed to diquat is very minimal.

Of most concern would be wild horses and burros that

feed exclusively in riparian areas, where drift might 

impact riparian grasses; however, this unlikely scenario

was not modeled. 

Diuron

Ingestion of food items contaminated by direct spray of 

diquat would pose no acute risk and moderate chronic 

risk to large mammalian herbivores if diuron was 

applied at the typical application rate, and low acute risk 

and high chronic risk if applied at the maximum 

application rate (ENSR 2005f). However, because

diuron is a non-selective herbicide and is registered for 

non-cropland applications, it is not likely to be used in 

rangelands where some vegetative cover is desired. 

Therefore, exposure of wild horses and burros to diuron

would be limited. If typically foraged rangeland plants 

were protected from off-site transport of diuron, such as 

with appropriate buffer zones (see Vegetation section in 

this chapter), then wild horses and burros would not 

likely be at risk from off-site drift or surface runoff of 

diuron. 

Fluridone 

Risk quotients for large terrestrial animals were below

the most conservative LOC of 0.1 for all scenarios 

(ENSR 2005g). These results indicate that accidental

direct spray or drift of this aquatic herbicide would not

likely pose a risk to wild horses and burros. 

Imazapic

Risk quotients for terrestrial animals were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of imazapic would not likely pose a risk to wild

horses and burros (ENSR 2005h). Proper use of

imazapic in range and pasture areas could benefit wild

horses and burros over the long term by controlling

unpalatable invasive plant species and promoting the 

establishment and growth of native plant species that

may be more desirable for forage. 

Overdrive®

Overdrive® poses low chronic risk to large mammalian 

herbivores that consume plants contaminated by direct

spray at the typical application rate and a moderate risk

for ingestion rates at the maximum application rate 

(ENSR 2005i). Because Overdrive® is proposed for use 

in rangelands and has moderate residual activity, wild

horses and burros may be at risk from the application of 

this chemical, particularly if it is sprayed throughout the

range area (an unlikely scenario). The use of Overdrive® 

in rangeland could benefit wild horses and burros by

controlling unpalatable invasive plant species and

promoting the establishment and growth of native plant 

species that may be more suited for forage. However, 

because chlorsulfuron and imazapic are less risky to

wild horses and burros and have similar target species, 

these herbicides could be considered for use instead of 

Overdrive®, where possible. 

Sulfometuron Methyl 

Risk quotients for terrestrial animals were all below the 

most conservative LOC of 0.1, indicating that direct 

spray of sulfometuron methyl is not likely to pose a risk 

to wild horses and burros (ENSR 2005j). Because this 

herbicide is relatively non-selective, it is not likely to be 

used in HMAs, and therefore, should result in few 

negative or positive impacts on wild horses and burros. 

Tebuthiuron 

The ingestion of food items contaminated by direct

spray of tebuthiuron at the maximum application rate 

would pose a low acute and chronic risk to large 

mammalian herbivores (ENSR 2005k). Tebuthiuron is 

not prominently used in rangeland habitat; the strength

of this herbicide is its use as a habitat modifier, 

including thinning sagebrush to improve sage-grouse 

habitat. It is relatively non-selective but does not tend to

harm grasses that are present. Therefore, impacts to

wild horses and burros would be unlikely with intended 

use of this herbicide. 

Impacts of Forest Service-evaluated Herbicides

The following information for eight herbicides proposed

for use by the BLM is taken from ERAs performed by

BLM Vegetation Treatments Using Herbicides 4-140 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

the Forest Service to support assessment of the 

environmental consequences of using these herbicides 

in Forest Service vegetation management programs 

(risk assessment results available at USDA Forest

Service [2005] and SERA [2005a]). Because the Forest

Service completed these ERAs prior to completion of 

the PEIS, the BLM would use these ERAs to assess the 

potential ecological impacts of using these herbicides in

future BLM vegetation management activities. The 

BLM previously evaluated and approved these eight

herbicides in an earlier EIS—Vegetation Treatment on 

BLM Lands in Thirteen Western States (USDI BLM

1991a). As part of its risk assessments (see USDA 

Forest Service 2005), the Forest Service developed

worksheets (see SERA 2005b), which allowed the BLM

to assess risks of the herbicides using its own maximum 

application rates and LOCs (rather than the Forest

Service rates and LOCs), to parallel the BLM process as 

much as possible. However, modeled risk scenarios for 

terrestrial animals may be different than those used for 

the BLM-evaluated herbicides, depending on the

specificity of available toxicity data. The assessment of 

impacts below is presented using the Forest Service 

upper estimates of HQs, to maximize the conservatism 

of the assessment. In addition, it should be noted that

the development of HQs by the Forest Service and the 

BLM is already conservative for many reasons (e.g., 

assumption of 100% dermal absorption, assumption of 

100% of diet contaminated, use of most sensitive values 

for exposure and dose/response assessments). 2,4-D, 

clopyralid, glyphosate, metsulfuron methyl, and 

triclopyr are the Forest Service-evaluated herbicides that

are most likely to be used in rangeland situations with

grazing wild horses and burros. However, it is possible 

that other herbicides used nearby could impact wild

horses and burros if they were transported off site. 

2,4-D 

2,4-D could pose a risk to some wild horses and burros 

as a result of direct spray as well as ingestion of sprayed

vegetation (Table 4-26; SERA 1998). Adult wild horses 

and burros may face less risk from direct spray than

young wild horses and burros because they have a

smaller surface area to volume ratio over which to 

absorb the herbicide. Direct spray impacts to wild 

horses and burros from 2,4-D can largely be prevented 

if animals are removed from target areas before 

spraying. In addition, wild horses and burros face risk

from the consumption of vegetation contaminated by

2,4-D at the application site; large mammals face

moderate acute and chronic risk for ingestion scenarios 

involving both the typical and maximum application

rates, and small mammals face low acute risk for 

ingestion scenarios involving the typical and maximum 

application rates. Large wild horses and burros that 

primarily consume grasses are particularly susceptible 

to risk under the vegetation consumption scenarios. 

However, long-term consumption of contaminated

vegetation may be unlikely if the vegetation shows 

signs of damage. The risk assessment suggests that 

because large wild horses and burros eating large

quantities of grass and other vegetation could be at risk

from routine exposure to 2,4-D, and because 2,4-D is 

considered for use in rangeland, this herbicide should

not be applied over large application areas where 

foragers would consume only contaminated food. 

Clopyralid 

According to the Forest Service risk assessment (SERA

2004b), clopyralid unlikely to pose a risk to terrestrial

animals. However, under a few scenarios there would

be a low acute risk to wild horses and burros. Small

mammals are at risk from 100% absorption of direct 

spray and consumption of contaminated insects, and

large wild horses and burros face risk from the 

consumption of contaminated vegetation. Application of 

clopyralid at the maximum application rate also poses 

low chronic risk to large wild horses and burros 

consuming on-site contaminated vegetation. The most 

likely risk scenario would be the consumption of 

contaminated grass across large areas by wild horses

and burros, which could likely be avoided by restricting 

access of these animals to sprayed areas. In addition, all 

risks identified fall within the lowest risk category. 

Glyphosate 

Wild horses and burros would face some risk from the

use of glyphosate in rangelands. Direct spray of a small

animal, assuming 100% absorption, would pose a low 

risk if glyphosate was applied at the typical application 

rate, and a moderate risk if applied at the maximum 

application rate (SERA 2003a). Risks to small wild

horses and burros from direct spray would likely be 

greater than risk to large wild horses and burros, 

because of their larger surface area to body weight

ratios. Direct spray impacts from glyphosate can largely 

be prevented if wild horses and burros are removed

from the target area before spraying glyphosate. For 

large mammals consuming contaminated vegetation, 

there would be low acute risk associated with

applications at the typical application rate, and moderate

acute risk and low chronic risk associated with

applications at the maximum application rate. For small

mammals there would be low risk associated with

BLM Vegetation Treatments Using Herbicides 4-141 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

consumption of contaminated vegetation sprayed at the 

maximum application rate. The most likely risk scenario 

is the acute consumption of contaminated vegetation,

which is particularly risky for herbivores that consume 

large amounts of grasses, which contain higher

herbicide residue levels than other herbaceous 

vegetation and seeds. Glyphosate is used in rangelands 

for the management of grasses and broadleaves, 

including woody species. It is non-selective, suggesting 

that spot applications in rangeland would be the most

appropriate use of this herbicide, because they would

reduce of the likelihood that wild horses and burros 

would consume contaminated vegetation, since fewer 

non-target areas would be impacted by direct spray or 

spray drift. 

Hexazinone 

At the typical and maximum application rates, several

scenarios could potentially pose low to moderate risk to

wild horses and burros (SERA 1997). Small mammals 

directly sprayed by hexazinone at the maximum 

application rate would face a low risk, assuming 1st

order dermal absorption, and low to moderate risk

assuming 100% dermal absorption. Acute exposure 

through consumption of contaminated vegetation would

pose a low risk to small mammals if hexazinone was 

applied at the maximum application rate; acute and 

chronic exposure through consumption of contaminated

vegetation would pose a moderate risk to large

mammals. Also, acute consumption of contaminated

water would pose a low risk to small mammals if

hexazinone was applied at the maximum application 

rate. It appears that wild horses and burros would be at 

risk from adverse effects from hexazinone applications. 

However, if food and water sources were not 

contaminated, risks would be minimized, and direct

spray could be avoided by removing wild horses and 

burros from the target area prior to treatment. 

Contamination of food and water sources could be 

minimized by utilizing spot applications of hexazinone

at the typical application rate. Because hexazinone is 

used for woody species, it would not likely be applied in 

rangelands where invasive plants are usually grasses or

herbaceous vegetation. In addition, hexazinone is semiselective, and is typically only applied in spot

applications; therefore, risks to wild horses and burros 

under normal applications may be lower than those 

predicted by the risk assessment. 

Imazapyr

For applications of imazapyr at the typical application 

rate, ERAs predicted no risks to wild horses and burros

under any exposure scenario (SERA 2004d). For 

applications at the maximum application rate, however, 

there is a low risk to wild horses and burros under two

scenarios: direct spray (small animal) and consumption

of contaminated vegetation (large mammal). Imazapyr 

is not registered for use in rangelands; therefore, it is

unlikely that impacts via direct spray or consumption of 

contaminated vegetation would occur. The likelihood of 

impacts could be further minimized by removing wild

horses and burros from areas near to application sites 

prior to spraying and by observing appropriate buffer 

distances from HMA vegetation when applying 

imazapyr (see Vegetation section in this chapter). 

Metsulfuron Methyl 

Wild horses and burros would face minimal risk from

the application of metsulfuron methyl. None of the HQs 

estimated for metsulfuron methyl exposure at the typical

application rate indicate risk to any of the terrestrial

animal receptors (SERA 2004e). When applied at the

maximum application rate, metsulfuron methyl would

pose a low risk to small animals via 100% absorption of 

direct spray and to large mammals via consumption of

contaminated vegetation. Metsulfuron methyl is

registered for use in rangeland, but impacts to wild

horses and burros would be unlikely if the typical

application rate was used. If the maximum application 

rate was used, impacts to wild horses and burros could

be avoided by removing animals from application areas 

prior to spraying metsulfuron methyl, and by limiting

the size of the application area or restricting access of

wild horses and burros to recently sprayed areas to 

prevent consumption of large amounts of sprayed 

vegetation. 

Picloram 

Application of picloram would not likely impact wild

horses and burros. Most of the HQs for the evaluated

scenarios of picloram exposure were below the LOC for 

both the typical and maximum application rates (SERA

2003b). Under two scenarios HQs were elevated above

the LOC, indicating low to moderate risk at the typical 

and maximum application rates: 100% absorption of

direct spray by a small animal and acute exposure 

through consumption of contaminated vegetation by a 

large mammal. Picloram is registered for use in

rangeland, and it could be applied over large areas, as its 

primary targets are broadleaf and woody species. 

Therefore, it could be used to manage certain 

broadleaved plants without impacting native or 

desirable grasses. Impacts to wild horses and burros 

could be avoided by removing animals from application 

BLM Vegetation Treatments Using Herbicides 4-142 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

areas prior to spraying picloram, and by limiting the size 

of the application area or restricting access of wild

horses and burros to recently sprayed areas to prevent

consumption of large amounts of sprayed vegetation. 

Triclopyr 

Triclopyr presents some risk to wild horses and burros, 

particularly through the consumption of contaminated

vegetation (SERA 2003c). Because risk categories 

determined using calculated HQs for the two evaluated 

formulations of triclopyr (triclopyr acid and triclopyr 

BEE) are the same, no differentiation will be made

between these two formulations in this section. The 

following scenarios pose a low risk for applications at

the typical application rate, and a moderate risk for 

applications at the maximum application rate: 1st order 

and 100% absorption of direct spray by a small 

mammal, and acute and chronic exposure through 

consumption of on-site contaminated vegetation by a 

large mammal. In addition, for applications at the 

maximum application rate, there would be a low risk

associated with acute exposure through consumption of 

water contaminated by a spill by a small mammal, and 

chronic exposure through consumption of off-site 

contaminated vegetation by the large mammal. No risk

is predicted for small mammals as a result of acute or 

chronic exposure through consumption of contaminated

vegetation or water. Triclopyr can be used in rangelands 

to selectively manage woody species without impacting 

native or desirable grasses. It also has low residual

activity. Impacts to wild horses and burros could be 

avoided by removing animals from application areas 

prior to spraying, and by limiting the size of the 

application area or restricting access of wild horses and 

burros to recently sprayed areas to prevent consumption

of large amounts of sprayed vegetation. Because large

wild horses and burros are susceptible to impacts from

long-term consumption of vegetation contaminated by

triclopyr, it is important to limit exposure of wild horses 

and burros to sprayed vegetation until residual activity 

has tapered off, particularly since sprayed grasses may 

not show signs of damage. 

Impacts by Alternative 

The following sections discuss the expected effects of

each of the five alternatives on wild horses and burros,

and compare the effects expected under each alternative 

with those expected under the other alternatives. These 

effects may vary depending on the acreage treated using

different application methods and herbicides, as well as 

the size of treatment events. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation treatment programs in

14 western states, and would be able to use 20

herbicides previously approved under earlier RODs. 

Herbicide use under the No Action Alternative could

impact wild horses and burros over an estimated

302,000 acres. The nature of impacts to wild horses and 

burros (positive and negative) would be similar to those

that have occurred in the past 10 years. Negative 

impacts to wild horses and burros could be lower than

under the other herbicide-use alternatives because fewer 

total acres would be treated using herbicides. 

Long-term positive impacts on wild horse and burro

communities (i.e., improvements in rangeland forage) 

could be lower under this alternative than the other

herbicide-treatment alternatives. Under the No Action

Alternative, invasive plant populations would likely 

continue to expand at the current rate or more quickly, 

potentially replacing desirable native forage, and 

increasing the abundance of unpalatable or toxic plants. 

Three-fourths of wild horses and burros are found in

Nevada, Utah, and Wyoming (see Table 3-7), and about 

82,000 acres of vegetation would be treated in these

states using herbicides. Of these acres, over 40% would 

occur in evergreen shrublands (primarily sagebrush), 

19% would occur in annual and perennial grasslands 

(e.g., meadows, grasslands, and prairies), 18% would 

occur in perennial forb communities (treatments 

associated with non-native forbs including knapweed, 

thistles, and leafy spurge), and 4% each would occur in 

evergreen woodlands (primarily pinyon-juniper and 

pine forest treatments) and in riparian/wetland habitats. 

The focus of these treatments would be to remove and

control invasive vegetation and improve native 

shrubland and grassland communities, to the benefit of

wild horses and burros. Wild horses favor native 

grasses, including bluebunch wheatgrass, western

wheatgrass, Indian ricegrass and blue grasses, and 

riparian/wetland vegetation, including sedges. Wild

burros feed on a variety of plants, including grasses, 

Mormon tea, paloverde, and plantain. Treatments that 

improve range habitat should benefit these plant

species. 

Because the new herbicides proposed in this PEIS 

(diquat, fluridone, imazapic, and Overdrive

®) would not 

be used under the No Action Alternative, risks to wild

horses and burros would be different than under the

other alternatives. Fluridone and imazapic do not

BLM Vegetation Treatments Using Herbicides 4-143 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

present any risks to wild horses and burros under 

modeled scenarios (similar to chlorsulfuron, 

metsulfuron methyl, and sulfometuron methyl), and

Overdrive® poses a low to moderate risk to large wild

horses and burros under a chronic exposure scenario in

which an animal ingests contaminated vegetation over a

long time period. Diquat is fairly toxic to wild horses 

and burros, particularly under food ingestion scenarios 

(similar to 2,4-D and diuron). However, diquat is an 

aquatic herbicide, and frequent exposure to wild horses

and burros would not be expected. Under the No Action

Alternative, the BLM’s repertoire of herbicides that are

not injurious to terrestrial animals would be smaller than

under the Preferred Alternative. As a result, per area 

risks to wild horses and burros would potentially be 

greater if more injurious herbicides (e.g., 2,4-D, 

bromacil, diuron, tebuthiuron, triclopyr) were used 

instead of safer herbicides, and the possibilities of more

effective rangeland improvements would be reduced. 

However, prohibiting the use of diquat from use, 

particularly in rangeland riparian areas, could somewhat

decrease per area risk to wild horses and burros. 

2,4-DP, asulam, atrazine, fosamine, mefluidide, and 

simazine were approved for use in the earlier BLM

EISs, but the BLM has not used any of these herbicides, 

except fosamine (< 50 acres annually) since 1997, and 

does not plan to utilize them in the near future. None of

these herbicides would normally be used in rangeland 

treatments where wild horses and burros might come

into contact with them. Instead, the BLM would use 

other herbicides, including triclopyr, sulfometuron

methyl, bromacil, diuron, and Overdrive

®, which are 

effective in controlling weeds and invasive vegetation,

but have less risk to wild horses and burros. 

The BLM would not be able to use herbicides in

Alaska, Nebraska, and Texas under the No Action 

Alternative, but would be able to conduct herbicide 

treatments in these states under the other herbicidetreatment alternatives. No wild horses or burros use

lands in these states. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

The Preferred Alternative would result in the treatment

of approximately 932,000 acres in 17 western states. In

addition to the 14 previously approved herbicides, the 

BLM would be able to use the four new herbicides 

evaluated in this PEIS. This alternative would result in 

the most extensive effects to wild horses and burros 

(both negative and positive) because it proposes the 

most acres for treatment (3 times the acreage that would 

be treated under the No Action Alternative). The extent 

of positive and negative impacts to wild horses and

burros would depend on the relative amount each of the 

herbicides was used, whether they would be applied in

rangeland environments, and the method of application.

The likelihood of negative impacts would be greatest if 

diuron, diquat, bromacil and/or 2,4-D were used

extensively. However, diquat, an aquatic herbicide, and 

bromacil and diuron, non-selective herbicides, are not 

likely to be used extensively in rangelands. If these

herbicides were used in restricted scenarios as proposed, 

and other herbicides were used effectively to increase

the abundance of native forage relative to unpalatable

weeds, positive impacts to wild horses and burros could

outweigh negative impacts. 

Because more acres would be treated, benefits to wild

horses and burros from improved rangeland and riparian

conditions should be much greater under this alternative 

than under the other alternatives. Over 375,000 acres are 

proposed for treatment using herbicides in Nevada, 

Utah, and Wyoming, states with the largest populations

of wild horses and burros. The percentage of treatments 

occurring in different plant community types would be

similar to that of the No Action Alternative (43% of 

acres treated would occur in evergreen shrublands, 19% 

in annual and perennial grasslands, 18% in perennial 

forb communities, and 9% in evergreen woodlands), but 

4 times as many acres would be treated in these states 

under this alternative. 

The ability to use the four new herbicides (diquat, 

fluridone, imazapic, and Overdrive®) as well as future 

herbicides that become registered with the USEPA 

would allow BLM managers more options in choosing 

the least toxic herbicides that best match treatment goals 

and application conditions. As a result, there could be 

an increase in per capita benefits and a reduction in 

overall per capita risks to wild horses and burros (three 

of the four new herbicides present little to no risk to 

wild horses and burros) and an increase in habitat and 

ecosystem benefits from treatment. This alternative 

would also reduce risks and negative impacts associated 

with other vegetation management methods (e.g., risk of 

escaped prescribed fires; see the PER). 

Alternative C – No Use of Herbicides 

Under Alternative C, wild horses and burros would not

be affected by herbicide use. Primary impacts would

stem from other vegetation treatment methods (see the 

accompanying PER; USDI BLM 2007a). Positive

benefits to rangelands as a result of vegetation 

BLM Vegetation Treatments Using Herbicides 4-144 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

management could be reduced under this alternative, as 

certain invasive species are only effectively controlled 

by herbicides, and in some situations other methods are 

impractical due to cost, time, or public concerns. For 

example, mechanical and manual methods are 

impractical over large land areas, which are more

effectively treated by broadcast herbicide applications. 

In addition, it is often difficult to eradicate some

species, such as shrubs that resprout from rhizomes

(e.g., sand shinnery oak), by means other than herbicide

application. Similarly, pre-emergent herbicides that 

persist in the soil are the most effective means of

controlling invasive plants with seeds that remain viable 

for long periods of time. 

Under this alternative, in the absence of herbicide

treatments, invasive plant populations would likely

continue to spread, possibly at increasing rates, and 

replace native vegetation, including rangeland forage

for wild horses and burros, particularly where other 

treatment methods are not effective or possible (e.g., 

large tracts of rangeland or grassland dominated by

invasive species, areas with resprouting shrubs or 

without enough fine fuels to carry prescribed fires). The 

spread of invasive weed populations would likely have 

deleterious effects on wild horses and burros. For 

example, rangeland within HMAs that contains 

excessive or unpalatable brush cover is less useful for 

grazing. However, it is uncertain how potential negative

impacts from this alternative (mostly indirect) would 

compare with negative direct and indirect impacts from

herbicide use. 

Alternative D – No Aerial Applications 

Alternative D would be the same as the Preferred

Alternative as far as herbicides that could be used, and 

areas that could be treated. Therefore, both alternatives 

would be equally likely to have both positive and 

negative effects on wild horses and burros and

rangeland. The BLM would be able to choose from a 

suite of currently-approved herbicides and herbicides 

that could be approved under this PEIS, or in the future. 

However, this alternative would not allow the BLM to 

apply herbicides aerially. Fewer acres would be treated 

(535,000 acres) because some large areas, including 

rangelands, cannot be effectively treated by ground 

application methods. However, acres proposed for aerial

treatments comprise only about 20% of all acres 

proposed for treatment in the primary wild horse and 

burro states─Nevada, Utah, and Wyoming. And of 

these acres, about 65% of aerial treatments would occur 

in evergreen shrublands, and 13% would occur in 

evergreen woodlands, habitats that provide less value to 

wild horses and burros than grassland and riparian

habitats. 

This alternative would substantially reduce the impacts 

of off-site drift to wild horses and burros, an exposure 

scenario that was not specifically modeled for most

herbicides (consumption of contaminated vegetation

off-site was modeled for most of the Forest Service 

herbicides, with no risks to wild horses and burros 

predicted for any of these herbicides, except triclopyr at

the maximum application rate). Conversely, without the 

option to spray herbicides aerially, large areas of

rangeland may remain untreated under Alternative D, 

which could negatively impact wild horse and burro

habitat and forage in these areas over the long term. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Approximately 466,000 acres would be treated under 

Alternative E, which is slightly less than the acreage

that would be treated under Alternative D, and less than

half of the acreage that would be treated under the 

Preferred Alternative, but is still an increase from the

average annual treatment acreage that has occurred over 

the past 8 years and would likely occur under the No

Action Alternative. Herbicide-related impacts to wild 

horses and burros would be lower under this alternative 

than under the Preferred Alternative because fewer 

acres would be treated with herbicides, and additional

protective standards would be required during herbicide

treatment (e.g., preferential use of spot rather than 

broadcast applications, preferential treatment of small

versus large infestations). 

Sulfonylurea herbicides and other ALS-inhibiting 

herbicides (e.g., chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, sulfometuron methyl) block the 

synthesis of amino acids that are required for protein

production and cell growth, thereby resulting in plant

death. ALS-inhibiting herbicides would not be used

under this alternative because data suggest they have the 

potential to damage off-site native and crop plant

species under the right conditions of environment and 

application. These herbicides are biologically active at

low concentrations, and are applied at lower application 

rates than other herbicides to manage target plants. It is 

uncertain whether use of these herbicides would result 

in fewer cases of unintended damage to wild horses and

burros and rangeland due to lower application rates, or

more cases due to the high potency of the herbicides 

and their persistence. In 1981, the Environmental

Effects Division of the USEPA recommended against

registering sulfonylurea herbicides because they persist

BLM Vegetation Treatments Using Herbicides 4-145 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

for long periods of time in the environment and they

cannot be detected at low levels. However, risk

assessments did not predict risk to wild horses and

burros for any of the ALS-inhibiting herbicides when

applied at the typical application rate, under any of the 

modeled scenarios, suggesting that the elimination of 

these herbicides would not benefit wild horses and 

burros and could indirectly harm wild horses and burros

if more toxic herbicides were used in their place. 

Alternative E incorporates other management practices 

that would be likely to have positive impacts on wild 

horses and burros and rangelands. Alternative E would 

limit the use of broadcast applications, which would

reduce the possible risks to wild horses and burros 

associated with off-site drift and consumption of 

vegetation across large areas. However these 

applications would be available for use in appropriate

situations (i.e., where no other method is practical and 

susceptible non-target plant species and aquatic areas 

are distant from the application area), which would

result in some ecosystem benefits from larger-scale

herbicide applications. While per-treatment ecosystem

benefits may be greater under Alternative E than under 

the other herbicide-use alternatives as a result of this

ecosystem-based management approach, overall 

positive vegetation and ecosystem benefits (that cannot

be attained by other treatment methods) across the 

western states would be lower under this alternative 

because of the relatively small treatment acreage and the

inability to use certain practices in situations that might

require their use (e.g., use of ALS-inhibitor herbicides

on highly aggressive weeds). For example, imazapic,

which has been shown to be effective in treating downy 

brome and leafy spurge, would be unavailable under 

this alternative. The BLM would also be unable to use 

chlorsulfuron and metsulfuron methyl to control yellow 

starthistle and several species of thistle that are harmful

to wild horses and burros. 

Mitigation for Herbicide Treatment 

Impacts 

The following actions would greatly reduce the risks to 

wild horses and burros from herbicide applications: 

• Apply diuron, glyphosate, hexazinone 

tebuthiuron, and triclopyr at the typical 

application rate to minimize risks to wild 

horses and burros. 

• Do not apply 2,4-D, bromacil, diuron, 

Overdrive®, picloram, or triclopyr across large 

application areas, where feasible, to limit

impacts to wild horses and burros, particularly 

through the contamination of food items. 

• Apply herbicide label grazing restrictions for 

livestock to herbicide treatment areas that 

support populations of wild horses and burros. 

• Where practical, limit glyphosate and 

hexazinone to spot applications in rangeland to 

avoid contamination of food items. 

• Do not aerially apply diquat directly to 

wetlands and riparian areas. 

• Do not apply bromacil and diuron in grazing 

lands within HMAs, and use appropriate buffer 

zones (see Vegetation section) to limit

contamination of vegetation in off-site foraging 

areas. 

• Do not apply 2,4-D, bromacil, or diuron in 

HMAs during the peak foaling season (March

through June, and especially in May and June), 

and do not exceed the typical application rate

of Overdrive® or hexazinone in HMAs during

the peak foaling season. 

Paleontological and Cultural 

Resources 

Invasive plants may have long-term negative impacts on

paleontological and cultural resource sites by displacing 

native vegetation and increasing the potential for soil

erosion, potentially leading to the loss of 

paleontological and cultural resources. In addition to 

limiting these impacts, removal of invasive vegetation

would contribute to the restoration and maintenance of 

historic and ethnographic cultural landscapes (USDI 

National Park Service 2003). 

Herbicides could harm traditional use plants, or threaten

the health of the people gathering, handling, or ingesting

recently treated plants, fish, or wildlife that are 

contaminated with herbicides (BPA 2000). Since roots 

and other plant materials harvested by Native peoples

may be found in close proximity to weed treatment

areas, the potential exists for herbicides to drift from 

treatment areas onto areas used by Native peoples

(ENSR 2001). In some cases, vegetation important to

Native peoples, including juniper, may be treated in

areas where these plants are invasive and crowding out 

more desirable vegetation. 

BLM Vegetation Treatments Using Herbicides 4-146 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Some respondents felt that cultural preservation is an

important issue, and encouraged addressing the impacts 

to cultural and archaeological sites. Other respondents 

suggested that traditional cultural properties should be

properly safeguarded, and treatments should be

completed in a way that is sensitive to cultural 

resources. There was concern about the effects of

herbicides on basket plants and the people who collect

them, in particular Native Americans. Respondents 

noted that fire generally helps these basket plants, while

herbicides are detrimental. 

Standard Operating Procedures for 

Addressing BLM Actions on 

Paleontological, Cultural, and 

Subsistence Resources 

Before proceeding with vegetation treatments, the 

effects of BLM actions on cultural resources would be

addressed through compliance with the NHPA, as 

implemented through a national Programmatic 

Agreement (Programmatic Agreement among the

Bureau of Land Management, the Advisory Council on 

Historic Preservation, and the National Conference of 

State Historic Preservation Officers Regarding the 

Manner in Which BLM Will Meet Its Responsibilities 

Under the National Historic Preservation Act) and

state-specific protocol agreements with SHPOs. Effects 

on paleontological resources would be addressed as 

outlined in resource management plans developed under 

the authority of the FLPMA and site specific NEPA 

documents developed for vegetation treatments. The 

BLM’s responsibilities under these authorities are

addressed as early in the vegetation management project

planning process as possible. 

The processes for identifying and managing cultural 

resources are addressed in USDI BLM manuals 8100

(The Foundations for Managing Cultural Resources),

8110 (Identifying and Evaluating Cultural Resources), 

8120 (Tribal Consultation under Cultural Resource 

Authorities), 8130 (Planning for Uses of Cultural

Resources), 8140 (Protecting Cultural Resources), and 

Handbook H-8120-1 (Guidelines for Conducting Tribal

Consultation). Processes for identifying and managing 

paleontological resources are outlined in Manual 8270

(Paleontological Resource Management). The BLM

Cultural Resource Management program is responsible 

for the study, evaluation, protection, management, 

stabilization, and inventory of paleontological,

historical, and archeological resources. The program

also ensures close consultation with Native American

tribal and Alaska Native group governments, as 

required by law, for the maintenance, preservation, and

promotion of native cultural heritage and resources, 

including plant and animal subsistence resources and

the use of vegetation for religious and ceremonial

purposes. The BLM initiated consultation with Native 

American tribes and Alaska Native groups to identify 

their cultural values, religious beliefs, traditional 

practices, and legal rights that could be affected by

BLM actions. Consultation included sending letters to 

all tribes and groups that could be directly affected by 

vegetation treatment activities, and requesting 

information on how the proposed activities could impact 

Native American and Alaska Native interests, including 

the use of vegetation and wildlife for subsistence, 

religious, and ceremonial purposes (see Appendix G). 

Paleontological Resources 

The processes for identifying paleontological resources 

includes consultation with BLM regional

paleontologists, paleontology program contacts in BLM

field offices, state geological survey agencies, local 

colleges, universities or museums, or SHPOs (if

individual SHPOs deal with fossil resources) as part of 

the planning process. Procedures would be developed 

for protecting significant fossil resources as outlined in

BLM Handbook 8270-1 (General Procedural Guidance 

for Paleontological Resource Management). Resource 

Management Plans may be in place that have classified

sensitivity levels for important fossil resources and

management prescriptions associated with each

sensitivity level. Specific protective measures for 

paleontological resources would be identified at the 

local level during project development. In the case of 

RMPs that lack this classification scheme, projectspecific analysis would be needed to assess whether 

paleontological resource inventories based on available

information should be conducted. If a project area 

contained documented locations with paleontological

resources within the proposed project area, or had

geological or geomorphic characteristics likely to

contain vertebrate fossils, a field inventory could be 

required to locate and report previously unrecorded

paleontological resources. Site-specific mitigation 

measures would be developed during the 

implementation stage of the vegetation treatments, if

needed. 

BLM Vegetation Treatments Using Herbicides 4-147 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Cultural Resources 

Treatments would follow standard procedures for 

identifying cultural resources, in compliance with

Section 106 of the NHPA, as implemented through the

Nationwide Programmatic Agreement and state

protocols. The process includes necessary consultations 

with SHPOs and interested tribes and Tribal Historic

Preservation Offices (THPOs), where they are in place, 

at the state or local level as projects are planned. 

As part of the process of preparing for vegetation

treatments, cultural resource specialists would identify 

historic properties eligible for the NRHP. Historic

properties may include any prehistoric or historic 

district, site, building, structure, or object included in, or

eligible for inclusion in, the NRHP. Impacts to National 

Register-eligible cultural resources can be avoided 

through project redesign or be mitigated through

recordation, data recovery, monitoring, or other 

appropriate measures. If National Register-eligible

cultural resources were discovered during vegetation

treatments, appropriate actions would be taken to 

protect these resources or recover data following 

consultation processes. An important concern regarding 

the presence of non-cultural resource personnel on the

ground during herbicide treatments is the unauthorized 

collection of artifactual material, especially from

National Register-eligible properties. Procedures would

be developed, as part of an unanticipated discoveries 

plan that would include reporting previously unrecorded

cultural resources to local BLM professionals. 

Subsistence Resources 

Discussions would be held with Native American tribes 

and Alaska Native groups to determine which plants 

that could be affected by proposed herbicide treatments 

have traditional lifeway values, and whether there are

specific, traditional collecting areas. Important plants to

Native Americans include oak, juniper, pinyon, 

lodgepole pine, cottonwood, mesquite, amaranth, 

cattail, and brackenfern. These trees, shrubs, and plants 

or their fruits and seeds are traditionally used for 

subsistence, clothing, basketry, shelter, utilitarian items, 

and possibly medicines by one or more tribes or groups 

in the western U.S. and Alaska. Since other target 

species have common names similar to those of some

plants used traditionally, such as whorled milkweed or 

common reeds, the difference in names should be 

explained to Native Americans and Alaska Natives in 

those areas where treatments are planned. Treatments of

plants that are important for maintaining traditional 

lifeways may need to be modified or cancelled in

certain areas. On the other hand, there could be longterm benefits associated with treatments, such as 

reduction or elimination of non-native or invasive plant 

competitors, which would allow proliferation of 

traditionally used native species. 

Herbicide Impacts on Paleontological

and Cultural Resources 

Paleontological Resources 

The effect of herbicide treatments on fossil material 

would vary with respect to: 1) fossil type; 2) minerals;

3) degree of fossilization; and 4) whether the fossil is 

exposed or buried. Although it may be possible for 

chemicals found in herbicides to impact unique fossil 

material, herbicide treatments are more likely to affect

researchers, students, or other field personnel 

conducting paleontological research than the

paleontological resources. More likely, damage to fossil

materials, if present, would result from the use of

wheeled equipment used to apply herbicides. The 

potential for impacts to fossils would depend on the 

attributes of the fossil material, whether the fossil is 

buried or exposed, and the method of herbicide 

application. Methods involving the use of vehicles 

driving cross-country would potentially crush fossil

material exposed on the surface. 

Cultural Resources 

While herbicide treatments may affect buried organic

cultural resources, they are more likely to have a

negative effect on traditional cultural practices of 

gathering plant foods or materials important to local 

tribes or groups. The effect of herbicide treatments on

cultural resources depends on the method of herbicide 

application and the herbicide type used. Some

chemicals can cause soil acidity to increase, which

would result in deterioration of artifacts―even some

types of stone from which artifacts are made. 

Application of chemical treatments can also result in 

impacts such as altering or obscuring the surfaces of 

standing wall masonry structures, pictograph or 

petroglyph panels, and organic materials. While 

chemicals may affect the surface of exposed artifacts,

they can generally be removed without damage if

treated soon after exposure. Organic substances used as 

inactive ingredients in herbicide formulations, such as

diesel fuel or kerosene, may contaminate the surface

soil and seep into the subsurface portions of a site.

These organic substances could interfere with the 

BLM Vegetation Treatments Using Herbicides 4-148 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

radiocarbon or Carbon 14 (C-14) dating of a site (USDI 

BLM 1991a). 

Subsistence Resources 

Depending on the selected application method for 

herbicide treatment plans, the BLM might be unable to 

avoid plants identified by Native American tribes and

Alaska Native groups as being important in traditional 

subsistence, religious, or other cultural practices. 

Consultation would be undertaken with tribes and

groups to locate any areas with plants that are of 

importance to the tribe and that might be affected by

chemical treatments. Certain chemical treatments could 

also pose a possible health risk, through residues left on 

plants used as traditional foods or for ceremonial 

purposes, or as a result of contaminating other food 

sources or drinking water, as discussed below. A study

to assess the exposure of basketweavers to forestry 

herbicides showed that detectable residues of herbicides 

were found on 49% of plant materials used by Native 

Americans inside treatment areas, but only 3% of plant

materials outside of treatment areas, and that residues 

continued to be detected for several months (Segawa et

al. 1997). However, a study of herbicide uptake by

lomatium and bitter root roots in rangeland treated with 

picloram and sulfometuron methyl showed that no

herbicide residues were found in roots at 2, 6, and 45

weeks after treatment (ENSR 2001). Thus, risks would 

vary depending upon the time of plant use and herbicide 

treatment, and the portions of the plants that were used. 

Herbicide Impacts on Native American

Health 

Exposure Characterization

The potential risks to Native Americans from exposure 

to herbicides used in BLM programs were evaluated

separately from risks to other public receptors (see

Human Health and Safety section in this chapter).

Native Americans could be exposed to higher levels of 

herbicides as a result of subsistence and cultural 

activities such as plant gathering and consumption of 

fish caught in local streams. Therefore, risk levels 

determined for Native American receptors reflect

unique exposure scenarios as well as typical scenarios 

for public receptors, but with higher levels of exposure 

than public receptors. 

The BLM risk assessments assume that the Native 

American receptors (154-pound adult and 33-pound 

child) are exposed to herbicides via dermal contact with 

spray, dermal contact with sprayed foliage, ingestion of 

drinking water from a sprayed pond, ingestion of berries 

containing spray, dermal contact with water in a sprayed

pond, and ingestion of fish from a sprayed pond. 

Dermal Contact 

For potential herbicide contact, the risk assessments 

assume the 50th percentile surface area of the Native

American’s lower legs, lower arms, and hands are 

exposed (i.e., 698 in2

 for adult men and women and 249

in2

 for children [USEPA 1997]), and that Native 

American receptors contact foliage for 3 hours per day

of subsistence activities (Harper et al. 2002). A dermal

transfer coefficient value—to estimate the amount of

herbicide transferred from foliage to skin—at the high 

end of the range was used for harvesting blueberries 

(i.e., 232 in2

/hour for the adult [USEPA 2000b] and 47

in2

/hour for the child based on the child to adult surface 

area ratio [CalEPA 1996]). The USEPA (2001c) 

recommends an exposed surface area of 2,790 in2

 for an 

adult swimmer and 1,023 in2 for a child swimmer.

Because no specific data were available regarding

surface area, these estimates were used to evaluate the 

Native American child-and-adult in the HHRA. The

exposure time for swimming is assumed to be 2.6 

hours/day in accordance with Harris and Harper (1997) 

which results in a swimming exposure frequency of 2.6

hours/day for 70 days/year. Incidental ingestion during

swimming was not evaluated for Native Americans, 

since it is assumed that the pond is also used as a source 

of drinking water; any incidental ingestion during 

swimming is therefore included in the drinking water 

scenario. 

Ingestion 

Risk assessments assume that adult Native Americans

ingest 1 quart of water per day (Harper et al. 2002) from 

a sprayed pond, and Native American children consume 

half the adult rate, or 0.5 quarts/day. The berry ingestion 

rate was developed from information provided in

Harper et al. (2002), which lists an ingestion rate of 0.7

lbs/day for an adult of the Native American Spokane 

tribe gathering aboveground terrestrial vegetation.

Berries are likely to be a small fraction of this 0.7 

lbs/day. However, since this rate was not subdivided

into additional categories, it was conservatively 

assumed that the ingestion rate for berries is 0.7 lbs/day

for an adult Native American. For a Native American

child, the ingestion rate was scaled by body weight (i.e., 

0.7 lbs/day x 33 lbs / 154 lbs) to 0.15 lbs/day (per 

CalEPA 1996). The adult fish ingestion rate was 

assumed to be 2 lbs/day based on a high fish diet 

scenario discussed in Harper et al. (2002). The high fish 

BLM Vegetation Treatments Using Herbicides 4-149 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

diet consists primarily of fish, supplemented by big

game; aquatic amphibians, crustaceans, and mollusks;

small mammals; and upland game birds. This value is

much higher than the 95th percentile fish ingestion rate

of 0.4 lbs/day recommended in USEPA (1997) for a 

Native American subsistence population. For Native 

American children, the ingestion rate was scaled by 

body weight (i.e., 1.9 lbs/day x 33 lbs / 154 lbs) to 0.4 

lbs/day (per CalEPA 1996). 

The Forest Service risk assessments evaluated risk to

Native Americans—in addition to typical risk for public 

receptors—for the scenarios of acute and chronic

consumption of contaminated fish. 

Risk Characterization

Native American adults face the same risks that public

receptors face, as well as additional risks associated

with exposure to some herbicides as a result of unique 

subsistence practices or increased time spent in treated 

areas. There are risks to Native American adults 

associated with exposure to diquat when it is 

accidentally spilled or applied at the maximum rate (low 

risk), and with the consumption of fish contaminated

with 2,4-D (high risk) and hexazinone (moderate risk). 

There are risks to Native American children associated 

with exposure to diquat when it is applied at the typical

rate. There are also risks associated with berry picking 

in areas sprayed with diquat at the typical rate. Both 

Native American adults and children residing near the 

treatment area would face additional risks (i.e., low risk 

from exposure to diquat when it is applied at the typical 

or maximum rate, and moderate risk from diquat when

accidentally spilled; low risk from exposure to fluridone

when it is accidentally spilled). See the Vegetation, Fish

and Aquatic Invertebrates, Wildlife, and Human Health

and Safety sections in this chapter for more information

on the risks of herbicides to Native Americans and the

resources they use. 

Impacts by Alternative 

The following is a discussion of how risk from

herbicides would vary under each herbicide treatment 

alternative. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Of the herbicide treatment alternatives, the fewest acres

would be treated under the No Action Alternative;

therefore, levels of risk to paleontological and cultural

resources, and health risks to Native Americans, Alaska 

Natives, and other human receptors would be lower 

than under the other herbicide treatment alternatives. If 

more acres were to be treated by other vegetation 

management methods (e.g., prescribed fire, manual, 

mechanical, or biological treatments) under the No

Action Alternative, then the risks from these methods 

would also have to be considered (see the associated

PER). In addition, the new herbicides proposed in this 

PEIS (diflufenzopyr+dicamba [Overdrive

®], diquat, 

fluridone, and imazapic) would not be used. Of these

new herbicides, diquat poses a high risk to humans;

however, diflufenzopyr, dicamba, and imazapic are all 

relatively safe to humans, with no potential adverse

effects evident from the human health risk 

characterization, except in cases of unlikely accidental 

scenarios for dicamba. Of the 20 previously-approved 

herbicides, only four (clopyralid, imazapyr, metsulfuron

methyl, and sulfometuron methyl) have negligible to 

low risks to humans. Therefore, failure to approve the

four new herbicides would limit the options for 

treatment of vegetation without appreciable risk to

humans. Thus, the risk to humans per each herbicide 

application may be greatest under the No Action

Alternative. 

Under this alternative, the BLM may be less successful

in controlling weeds and poisonous plants that adversely 

affect humans, especially weeds most effectively 

controlled by the four newly proposed herbicides, than 

under the other alternatives. Weeds and other invasive 

vegetation can displace native species that are desirable 

to Native Americans, and may provide poorer quality 

forage and cover for wildlife used by Native American 

tribes. 

Under the No Action Alternative, the BLM would be 

able to continue to use six herbicides that were

approved for use under earlier BLM vegetation

treatment RODs: 2,4-DP, asulam, atrazine, fosamine,

mefluidide, and simazine. Except for fosamine, which 

has been used on less than 50 acres annually, these 

chemicals have not been used by the BLM since 1997

and are not proposed for use under the other herbicide 

treatment alternatives. It is unlikely that these chemicals 

would be used under the No Action Alternative. 

In 1998, the BLM conducted a literature review to

determine whether the earlier vegetation treatment ROD 

conclusions for asulam, atrazine, mefluidide, and

simazine were justifiable based on past and 1998 

toxicology and risk assessment procedures. This 

assessment was based on a literature search and

California Vegetation Management Final EIS

(California EIS; USDI BLM 1988a) to identify potential

BLM Vegetation Treatments Using Herbicides 4-150 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

human health risks. A literature review was not done for 

2,4-DP or fosamine, but these herbicides were analyzed 

in the California EIS (McMullin and Thomas 2000). 

Based on this analysis, it was determined that systemic

risks from using asulam may be greater than projected 

in the earlier EIS, but that risks to humans from the

other three herbicides are similar to, or less than, those

identified in earlier EISs. Based on the earlier EISs, 

literature reviews done for the BLM, and other studies, 

the risks to humans would be low for asulam, fosamine, 

and mefluidide, low to moderate for 2,4-DP, and

simazine, and moderate to high for atrazine (USEPA 

1995d). The BLM uses sulfometuron methyl, bromacil, 

and diuron in treatment situations where it used atrazine 

in the past, and triclopyr instead of fosamine. These 

substitute herbicides have similar, or lower, risks to 

humans than the herbicides they are replacing. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Because of the large number of acres treated, this 

alternative would likely result in the most overall risk to

paleontological and cultural resources and human

health. The number of acres treated using ground-based

application methods would be greater under this 

alternative and Alternative D than under the other 

alternatives, increasing the risk of damage to 

paleontological and cultural resources from equipment. 

However, human health could benefit from a reduction 

in the noxious weeds and poisonous plants that 

adversely affect humans, which would likely occur 

under this alternative. In addition, this alternative would 

allow the use of the new herbicides evaluated in the 

BLM HHRA (ENSR 2005l). Of these four herbicides, 

three appear to be relatively harmless to humans; use of 

these herbicides would increase the options for 

appropriately managing vegetation while minimizing

the risk to human receptors. It is suggested that diquat 

be used only in very limited scenarios at the typical 

application rate and where risk to human receptors is

not predicted, such as ground applications from trucks 

not near residences or berry gathering sites. 2,4-D, 

glyphosate, picloram, and tebuthiuron would be used for 

about 70% of herbicide treatments. There is low risk to

human health associated with use of glyphosate, 

picloram, and tebuthiuron at normal application rates, 

but risks to human health are low to moderate for 2,4-D. 

Although the BLM would be able to treat vegetation in

Alaska, Nebraska, and Texas under the Preferred

Alternative and Alternatives D and E, it is unlikely that 

the BLM would use herbicides in Alaska, especially in

areas with important Alaska Native resources. 

Alternative C – No Use of Herbicides 

Alternative C would eliminate risks to paleontological,

cultural, and human health from herbicide applications. 

However, risks to these resources and human health

associated with alternative vegetation management

methods would occur (these risks are perhaps greatest

for prescribed fire treatments [see PER]). In addition,

human health might be adversely affected if populations

of noxious weeds and poisonous plants that adversely 

affect humans were to remain at current levels or 

increase as a result of ceasing herbicide treatments. 

Alternative D – No Aerial Applications 

Human health risks per application area would be lower 

for Alternative D than for the No Action and Preferred

alternatives because herbicides would not be likely to 

drift as far, potentially affecting fewer humans. For 

many herbicides, the greatest risks to occupational 

receptors are associated with aerial applications; these 

risks would be eliminated under this alternative. 

Furthermore, this alternative would allow the use of the

new herbicides, which pose on average less risk to

humans than the currently used herbicides. Overall risks 

to human health would be lower than under the 

Preferred Alternative, which would treat about 400,000 

more acres and would use aerial spraying (however, the 

Preferred Alternative could eliminate more noxious and 

poisonous weeds that adversely affect human health 

than Alternative D). Overall risks to cultural and 

paleontological resources from ground-based equipment

would be similar to the Preferred Alternative, but risks 

associated with the herbicides themselves would be less,

since fewer acres would be treated with herbicides. 

Risks under Alternative D would likely be greater than

those under Alternative E, as Alternative E places 

emphasis on spot applications over broadcast 

applications, establishes herbicide-free zones to protect

culturally significant plant and wildlife resources, and 

prioritizes treatments that would enhance and preserve 

culturally significant plants and animals. However,

Alternative E would not allow the use of ALS-inhibiting 

herbicide active ingredients (i.e., chlorsulfuron,

imazapic, imazapyr, metsulfuron methyl, and

sulfometuron methyl), which exhibit the lowest risks to

humans out of the herbicides analyzed by the BLM. In

addition, these chemicals are effective in controlling 

weeds that can displace native plant species and 

associated wildlife that are of value to Native American

tribes. Because 240,000 more acres would be treated

BLM Vegetation Treatments Using Herbicides 4-151 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

under Alternative D than under the No Action 

Alternative, but higher risk aerial applications would not

occur and chemicals of lower risk would be used, it is

difficult to infer which of these two alternatives would

have lower overall risk. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides 

The five herbicides (chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, and sulfometuron methyl) that

would not be used under this alternative are among

those that pose the least risk to human health. Even in 

accidental scenarios, imazapic, imazapyr, metsulfuron 

methyl, and sulfometuron methyl do not pose a risk to

humans, and chlorsulfuron only poses a risk to workers 

when it is applied in ground broadcast applications at 

the highest application rate, and poses a risk to the 

general public if a large amount is accidentally spilled

into a very small pond—an unlikely scenario. From a 

practical perspective, eye and/or skin irritation are likely 

to be the only effects of mishandling ALS-inhibiting 

herbicides; these effects can be minimized or avoided 

by prudent industrial hygiene practices while handling 

of these compounds. Bromacil, diquat, and diuron, 

which pose the most severe human health risks, could

be used under Alternative E; therefore, risk to humans 

per area treated is not likely to decrease dramatically as 

a result of elimination of ALS-inhibiting herbicide

active ingredients. 

Alternative E places increased emphasis on spot rather

than broadcast applications, which would tend to 

decrease per area risk relative to the No Action and 

Preferred alternatives, except in the few possible cases

where occupational receptors would be at a greater risk

from spot applications. In addition, the proposed 

number of acres treated (466,000) is half that of the 

Preferred Alternative (932,000), which would translate 

to lower overall risk. Conversely, more acres would be 

treated under Alternative E than under the No Action

Alternative (305,000), so overall risk would be greater. 

Under all alternatives, the BLM would collaborate with

Native American tribes and Alaska Native groups to

identify and protect culturally significant plants used for 

food, basketweaving, fibers, medicine, and ceremonial 

purposes, and would use minimal impact treatments 

where culturally significant species are known to occur.

In addition, under Alternative E the BLM would

establish herbicide-free zones to protect culturally 

significant plant and wildlife resources, which would

reduce the likelihood that Native Americans and Alaska 

Natives would consume vegetation with herbicide 

residues. 

Mitigation for Herbicide Treatment 

Impacts 

In addition to SOPs, there are certain herbicide-specific

measures that could be taken to substantially reduce or 

eliminate human health risk from herbicide use. The 

following mitigation measures were developed based on 

the BLM HHRA, the Forest Service HHRAs, and the

Final EIS Vegetation Treatment on BLM Lands in

Thirteen Western States (1991 13-State EIS; USDI 

BLM 1991a): 

• Do not exceed the typical application rate

when applying 2,4-D, bromacil, diquat,

diuron, fluridone, hexazinone, tebuthiuron,

and triclopyr in known traditional use areas. 

• Avoid applying bromacil or tebuthiuron

aerially in known traditional use areas. 

• Limit diquat applications to areas away from

high residential and traditional use areas to 

reduce risks to Native Americans and Alaska

Natives. 

Visual Resources 

Visual resources consist of land, water, vegetation, 

wildlife, and other natural or manmade features visible 

on public lands. Vast areas of grassland, shrubland, 

canyonland, and mountain ranges on public lands

provide scenic views to recreation visitors, adjacent 

landowners, and travelers. In addition, roads, rivers, and 

trails pass through a variety of characteristic landscapes 

where natural attractions can be seen and where cultural

modifications exist. Activities occurring on these lands 

have the potential to disturb the surface features of the 

landscape and impact scenic values. 

Bureau policy requires that all acres of BLM land be

inventoried for scenic values and be assigned a Visual

Resource Management (VRM) Class (I-IV) during the 

land use planning process. These VRM classes are part

of the land use plan decisions for a particular office and 

set the management standards for visual resources that

activity level plans must subsequently meet. The 

acreage of BLM-managed public lands that are

categorized as Class I, II, III, or IV is not currently

known. 

BLM Vegetation Treatments Using Herbicides 4-152 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

The proposed vegetation treatments would affect visual 

resources by changing the scenic quality of the 

landscape. Herbicide treatments would kill vegetation in 

the applied area, resulting in visual contrast such as 

more open, “browned” landscape until new plants were

to grow in the area. The degree of change to scenic

quality could, in terms of visitor perception, vary 

relative to a particular area’s inherent visual appeal, and 

distance from human activity, as well as public

sensitivity to changes in the landscape character of the

area. However, according to the BLM’s VRM policy,

the extent of visual impact must be evaluated at the

project level according to the visual contrast rating

process (Handbook 8431-1). This process compares the 

amount of contrast to the form, line, color, and texture

of the characteristic landscape of an area as a result of a

surface disturbing activity. 

In general, the effects of vegetation treatments on the 

visual quality of the landscape would be most notable to

travelers, sightseers, and residents for the first year to 

several years following treatment, particularly in

impacted areas near major roads or residential areas.

Scenic impacts from vegetative treatments are most

likely to be associated with projects that 1) reduce the

visual rating of the treatment site over the long term, or

2) result in short- or long-term degradation of highsensitivity visual resources. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Scoping comments stressed that treatments should 

improve management of public lands for multiple use

and maximum public benefit. The visual quality of the 

landscape is seen as one component of public benefit, 

particularly if lands are located in highly visible areas 

along roads. 

Standard Operating Procedures 

There are several SOPs that would help reduce the

impact of herbicide treatments on visual resources: 

• Minimize the use of broadcast foliar 

applications in sensitive watersheds to avoid 

creating large areas of browned vegetation.

• Consider the surrounding land use before 

assigning aerial spraying as an application 

method. 

• Avoid aerial spraying near agricultural or 

densely populated areas, where feasible. 

• At areas such as visual overlooks, leave 

sufficient vegetation in place, where possible, 

to screen views of vegetation treatments. 

• Use SOPs that minimize off-site drift and 

mobility of herbicides (e.g., do not treat when 

winds exceed 10 mph; minimize treatment in 

areas where herbicide runoff is likely; establish 

appropriate buffer widths between treatment

areas and residences), to contain the visual

changes to the intended treatment area. 

• If the area is a Class I or II visual resource,

ensure that the change to the characteristic 

landscape is low and does not attract attention

(Class I), or if seen, does not attract the

attention of the casual viewer (Class II). 

• Lessen visual impacts by 1) designing projects 

to blend in with topographic forms; 2) leaving

some low-growing trees or planting some lowgrowing tree seedlings adjacent to the

treatment area to screen short-term effects; and 

3) revegetating the site following treatment. 

• When restoring treated areas, design activities 

to repeat the form, line, color, and texture of

the natural landscape character to meet

established VRM objectives. 

A more detailed list of SOPs is found in BLM

Manual Handbook H-8431-1 (Visual Resource 

Contrast Rating). 

BLM Assessment of Visual Resource 

Values 

The BLM identifies and evaluates visual resource

values through the VRM Inventory system (Handbook

H-8410-1; USDI BLM 1986a). The VRM system is a

policy used by the BLM to inventory and manage visual

resources on public land based on the aforementioned

VRM classes describing scenic quality, sensitivity level, 

and distance zone criteria. Visual resource management

objectives are established in resource management plans 

in conformity with land use allocations (USDI BLM

1984b). These area-specific objectives provide the 

standards for planning, designing, and evaluating future 

management projects. 

A Contrast Rating System (BLM Manual Handbook H8431-1; Visual Resource Contrast Rating; USDI BLM

1986b) provides a systematic means to evaluate the 

approved VRM objectives, and to identify mitigation

measures to minimize adverse visual impacts. The

BLM Vegetation Treatments Using Herbicides 4-153 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Contrast Rating System is designed to compare the 

respective features of the existing characteristic

landscape with a proposed project and to identify those 

parts that are not in harmony. These features include the 

basic design elements of form, line, color, and texture 

that characterize the landscape and the surrounding

environment. Modifications to a landscape that repeat

the natural landscape’s basic elements are said to be in 

harmony with their surroundings, while those that differ 

markedly may be visually displeasing. The information 

generated is used to determine the amount of visual

contrast created and whether the VRM objective for the

area would be met, and to develop additional mitigation 

measures necessary to meet the VRM objective. 

Summary of Herbicide Impacts 

The removal of vegetation would affect the visual

qualities of treatment sites by creating openings and 

other vegetation-free areas that provide a noticeable 

visual contrast to the surrounding areas. In addition, the

use of herbicides could create visually distinct areas of

discolored vegetation (i.e., areas where herbicides have 

killed vegetation), which could contrast markedly from 

surrounding areas of green vegetation. The degree of 

these effects would depend on the amount of area 

treated, the appearance of the background vegetation

and the vegetation being removed, the type of treatment 

method used, and the season of treatment. 

In general, herbicide treatments would have short-term

negative effects and long-term positive effects on visual

resources. The greater the area of vegetation treatment,

the greater the visual impact is likely to be. The effects 

of treatments over a large portion of the landscape are 

more likely to be observed by people than the effects of

small-scale treatments. However, since areas receiving

large-scale treatments are most likely to be degraded 

lands of low to moderate scenic quality, the visual

impact from treatment would be minimized and there 

would likely be an improvement in the scenic quality of 

the land over the long term. Color contrasts caused by 

vegetation removal would be most apparent in areas 

dominated by green and/or flowery vegetation and by 

large plants, such as conifer trees. The visual impacts 

would be heightened if the herbicides also prevented the 

manifestation of seasonal changes in vegetation, such as 

spring flowers and/or fall color. The contrast between a 

cleared area and the surrounding vegetation would be 

less in much of the arid west, where low-growing 

shrubs, and browns, grays, and earth tones dominate the 

landscape than in areas with greater amounts of rainfall

(e.g., the Marine Ecoregion). In addition, the brown

colors associated with vegetation treatments would be 

least noticeable during the late fall and the winter, when

they would blend more naturally with surrounding 

colors, than in the spring and summer, when the green 

colors of new growth are more likely to be present. 

Impacts to visual resources from herbicide treatments 

would begin to disappear within one to two growing

seasons in most landscapes. The regrowth of vegetation 

on the site would eliminate much of the stark

appearance of a cleared area. Impacts would last for the

longest amount of time in forests and other areas where 

large trees and shrubs were removed. 

Over the long term, vegetation treatments would likely 

improve visual resources on public lands. Treatments 

that aim to rehabilitate degraded ecosystems, if 

successful, would result in plant communities that are

dominated by native species. Native-dominated

communities tend to be more visually appealing than 

plant communities that have been overtaken by weeds 

(e.g., plant communities supporting a downy brome

monoculture) or other undesired species (e.g., 

grasslands experiencing encroachment by conifer 

seedlings). 

Impacts by Alternative 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

The No Action Alternative would continue current 

vegetation and herbicide treatments; therefore, visual 

impacts would remain the same as at present. These

impacts would be less than those under The Preferred

Alternative, because only one-third as many acres

would be treated using herbicides. The greatest visual

impacts would likely be associated with the largest

treatment areas. Under the No Action Alternative, 

projects with the largest treatment acreage (those over 

1,500 acres in size; 10% of all herbicide treatments) 

would be located in New Mexico (one-third of all largescale treatments) and Idaho/Nevada (one-third of all 

large-scale treatments). However, assuming that

treatments would be effective in reducing or eliminating 

invasive species populations and promoting conditions 

that favor the development of native plant communities, 

the visual quality of degraded landscapes would not

improve over the long term to the same extent as under 

the other treatment alternatives. As compared to the

Preferred Alternative, many lands would be left 

untreated and would continue to be dominated by

invasive plants or would be invaded in the future by

BLM Vegetation Treatments Using Herbicides 4-154 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

invasive plants. Landscapes containing a large 

component of invasive species often contrast with 

surrounding natural landscapes and have a negative 

visual impact. For example, downy brome often turns 

brown during summer, while native species usually 

remain green long into summer or fall. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

The Preferred Alternative would result in the greatest 

short-term negative impact on visual resources, as it 

involves treatment of the most acres with herbicides. 

The most dramatic effects would be seen in states with

the most acres treated, such as Idaho, Nevada, and 

Wyoming, and in project areas where large acreages are

treated. Under the Preferred Alternative, projects with

the largest treatment acreage (those over 2,000 acres in 

size; 10% of all herbicide treatments) would be located

in Idaho (one-third of large-scale treatments) and

Wyoming (20% of all large-scale treatments). One third

fewer large-scale treatments would occur in New 

Mexico under this alternative than under the No Action

Alternative. However, herbicide treatments in drier 

states, such as New Mexico, Nevada, and Wyoming, 

could have reduced visual impact because visual color 

contrast between natural and “browned” treated areas 

would be less dramatic (versus wetter states with higher 

percentages of green vegetation, especially coniferous 

forests). Over the long term, this alternative could have

the greatest positive impact on visual resources, as

invasive plants and unwanted vegetation would be 

removed and visually preferable native vegetation and

ecosystems would become reestablished on more acres. 

Alternative C – No Use of Herbicides 

Because no herbicide treatments would take place under 

Alternative C, visual resources would not be adversely

impacted by herbicide treatments. Conversely, visual

resources would not improve over time, and the visual

quality of landscapes could become further degraded as 

invasive plants continued to invade and spread. There 

are certain kinds of invasive plants that are most

effectively removed by herbicide treatments (e.g.,

Russian knapweed, purple loosestrife, Canada and 

Scotch thistles, yellow star-thistle); it may be difficult to 

eliminate these species by non-chemical treatment 

methods. In addition, if prescribed burning were to

increase under this alternative in order to maintain

control of invasive plants, visual impacts from

blackened vegetation and landscapes and short-term 

smoke would likely be more dramatic than visual 

impacts from herbicide use. 

Alternative D – No Aerial Applications 

Impacts to visual resources under Alternative D would 

be less than under the Preferred Alternative, and similar 

to those under the No Action Alternative and 

Alternative E, based on number of acres treated. In

addition, because large-scale treatments are less feasible 

without aerial spraying, fewer large areas of vegetation 

are likely to be killed by herbicides, further minimizing 

the short-term visual impact of herbicide treatments. 

Over the long term, however, this alternative would 

leave more large tracts of land untreated than the other 

treatment alternatives. Therefore, the No Action and 

Preferred alternatives, and Alternative E, could result in

more large land areas of recovering native vegetation

and ecosystems, and consequently improved visual

quality over time. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides

Based on number of acres treated, the visual impacts 

from herbicide treatments under this alternative would 

be similar to those under Alternative D. Visual impacts 

under this alternative would be somewhat moderated as 

compared to the Preferred Alternative because aerial

and boom/broadcast spraying of larger tracts of land 

would be avoided, thereby reducing visibility of treated

lands and sensitivity to treatments. In addition, 

imazapic, which is proposed for use in treating large

expanses of downy brome, would not be used. As fewer 

large tracts of land with degraded visual quality would

be treated, however, fewer large improvements would 

be made in the visual quality of vegetation and 

landscapes. 

Mitigation for Herbicide Treatment 

Impacts 

No mitigation measures are proposed for visual

resources. 

Wilderness and Special Areas 

Because of their special status, wilderness and special

areas have strict guidelines for vegetation treatments. 

These guidelines prohibit activities that degrade the

quality, character, and integrity of these protected lands.

Vegetation treatments used in wilderness areas follow 

the guidance contained in 43 CFR 6300 (Wilderness 

BLM Vegetation Treatments Using Herbicides 4-155 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Management; Federal Register 2000), and in the

Management of Designated Wilderness Areas 

Handbook H-8560-1 (USDI BLM 1988e), Management 

of Designated Wilderness Areas Manual 8560 (USDI 

BLM 1993), Interim Management Policy for Lands 

under Wilderness Review Handbook H-8550-1 (USDI 

BLM 1995) and the Wilderness Inventory and Study

Procedures Handbook H-6310-1 (USDI BLM 2001a). 

The guidance states: 

• Noxious weeds may be controlled by grubbing 

or with chemicals when they threaten lands 

outside wilderness or are spreading within the

wilderness, provided the control can be done

without serious impacts on wilderness values 

and treatments are necessary to maintain the

natural ecological balances. 

• Plant control must be approved for native 

plants when needed to maintain livestock 

grazing operations where practiced prior to the 

designation of wilderness. 

• Reseeding may be done by hand or aerial 

methods to restore natural vegetation. 

There are no set restrictions on vegetation treatments in

other types of special areas. However, the unique 

characteristics of these areas would be considered when

preparing management plans for treatment activities. 

Herbicide treatments can be used to remove noxious 

weeds, as long as they do not adversely affect

wilderness values. The proposed herbicide treatments 

could affect wilderness and special areas by altering the

existing plant species composition and structure, and 

altering the visual qualities of treated areas. 

Scoping Comments and Other Issues 

Addressed in the Assessment 

Respondents suggested that weeds should be stopped 

from spreading into wilderness areas by treating them

outside of these areas, while others requested that 

treatments within wilderness areas be undertaken only 

after the spread of weeds outside of these areas has been

effectively halted. Other respondents proposed that 

unique natural areas, including riparian zones, roadless 

areas, old growth areas, and areas of highest biological

integrity, should be protected and that roadless areas 

should not be treated. 

Standard Operating Procedures 

Actions that reduce the risk of spreading noxious weeds, 

prevent the establishment of new invaders, and promote 

public awareness would be encouraged by the BLM in 

wilderness and special areas.

• Encourage backcountry pack and saddle stock 

users to feed their livestock only weed-free

feed for several days before entering a 

wilderness area. 

• Encourage stock users to tie and/or hold stock 

in such a way as to minimize soil disturbance 

and loss of native vegetation. 

• Revegetate disturbed sites with native

vegetation if there is no reasonable expectation 

of natural regeneration. 

• Provide educational materials at trailheads and 

other wilderness entry points to educate the 

public on the need to prevent the spread of 

weeds. 

• Use the “minimum tool” to treat noxious and

invasive vegetation, relying primarily on use of 

ground-based tools, including backpack pumps, 

hand sprayers, and pumps mounted on pack 

and saddle stock. 

• Use chemicals only when they are the 

minimum method necessary to control weeds 

that are spreading within the wilderness or

threaten lands outside the wilderness. 

• Give preference to those herbicides that have 

the least impact on non-target species and on

the wilderness environment.

• Implement herbicide treatments during periods

of low human use, where feasible (USDI BLM 

1988e). 

• Address wilderness and special areas in

management plans. 

• Maintain adequate buffers for Wild and Scenic 

Rivers (1⁄4 mi on either side of river, 1⁄2 mi in

Alaska). 

Summary of Herbicide Impacts 

In general, herbicide treatments in wilderness and

special areas would have short-term negative effects and

long-term positive effects on wilderness and special

status area values. In wilderness areas and WSAs, only 

BLM Vegetation Treatments Using Herbicides 4-156 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

treatments that improve the natural condition of these

areas would be allowed. Therefore, long-term effects, if

treatments were successful, would be beneficial; 

noxious weed infestations and risk of future catastrophic 

wildfires would be reduced in these areas. 

The overall effect of herbicides on wilderness and

special areas would depend on whether the end

condition of the treatment site (considering both longterm benefits and short-term impacts) was an

improvement in wilderness characteristics. In many

cases (e.g., an eradication of a small population of an

incipient pest, a prescribed fire that mimics historical 

fire), communities in the treatment area would quickly 

recover, and the overall effect would be positive. In 

other cases (e.g., treatments that require the creation of

access roads to treatment sites, treatments that require 

repeated access to a site in order to meet a desired 

objective), the impacts of the treatment to the

wilderness character of the site would outweigh the 

potential long-term benefits. 

The short-term effects of vegetation treatments in other 

special areas would typically be less than those in

wilderness areas, as human activities and influences are 

not necessarily incompatible with their unique qualities. 

However, all treatments would have the potential to

alter these unique qualities, as well as to provide longterm benefits by controlling weeds and reducing fire 

risks. 

The reduction of hazardous fuels and noxious weeds on 

lands adjacent or near to wilderness and special areas 

would provide long-term benefits by reducing the 

likelihood that noxious weeds would spread onto these

unique areas, or that a catastrophic wildfire would burn

through them, thus degrading their unique qualities. 

Because there would be fewer restrictions on the

intensity of treatments on lands adjacent to wilderness 

and special areas, preventative treatments in these areas 

would eliminate or reduce the need for intrusive

treatments in wilderness and special areas in the future.

The need for emergency fire suppression activities, 

which can be very damaging, would also be reduced. 

Use of herbicides to treat undesirable vegetation could

potentially affect the “naturalness” of wilderness areas 

and WSAs by killing non-target native vegetation 

through imprecise application and/or drift. The degree 

of effects would depend on the application method, with

spot applications less likely to cause adverse effects 

than aerial applications. For the most part, vehiclemounted sprayers would not be used to treat vegetation,

given the existing restrictions on wilderness areas. 

However, vehicles could be used in extreme scenarios,

if approved. The long-term effects of herbicide 

treatments on wilderness and special areas would

depend on the success of the treatment in controlling 

noxious weeds. In most cases, the benefits of 

eradicating noxious weeds from wilderness and special 

areas would far outweigh the potential short-term

negative effects of using chemical treatments. 

The potential effects of chemical treatments on other 

special areas would depend on numerous site-specific 

factors, as discussed for the effects of other treatment

methods above. Some special areas would support 

resources that are more sensitive to exposure to 

herbicides than the resources in other areas. There

would also be human health risks involved with using 

certain types of herbicide application (e.g., aerial 

application) in special areas that are managed to support 

wilderness activities. 

Impacts by Alternative 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Impacts to wilderness and special areas under the No 

Action Alternative as a result of herbicide treatments 

would be similar to those that are currently experienced. 

Wilderness and special areas that are dominated by

invasive species are usually less visually appealing and 

offer fewer wilderness characteristics. Under the No 

Action Alternative, the BLM would treat only a third of

the number of acres treated under the Preferred

Alternative. Although BLM field offices did not 

specifically identify how many acres would be treated 

in wilderness and special areas when providing

information for this PEIS, it is presumed that fewer 

acres in wilderness and special areas would be treated 

under the No Action Alternative than under the other

herbicide-treatment alternatives. Therefore, fewer 

positive benefits from herbicide treatments would be

generated under this alternative, but there would also be 

fewer negative impacts on wilderness characteristics,

species of concern, and other resources associated with 

herbicide treatments in wilderness and special areas. In

addition, per capita vegetation treatments would not

likely be as effective in restoring wilderness and special

lands because the No Action Alternative would not 

allow the use of the four new herbicides evaluated in 

this PEIS. 

BLM Vegetation Treatments Using Herbicides 4-157 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Because Alternative B involves the most treatment

acres, it could also have the greatest short-term adverse 

impact on wilderness and special areas, primarily by

resulting in the temporary closure of more lands. Along

with these closures, there might be more lost

opportunities for collection of plant materials than under 

other alternatives. Although only a small portion of the 

acres treated using herbicides would be in wilderness 

and special areas, more acres in wilderness and special 

areas would be treated under this alternative than the 

other alternatives. Thus, this alternative could have the 

largest positive impact on wilderness and special areas 

since it would reduce the risk of loss of wilderness 

values and improve wilderness characteristics over the 

largest acreage possible. As a result, recreation hours 

spent at a given site could be greatest under this 

alternative. Given the larger number of acres that would

be treated, it is more likely that the BLM would be able 

to contain and eradicate noxious weed populations in 

wilderness and special areas under this alternative. 

Under this alternative, four new herbicides would be 

available for use by the BLM, and herbicide treatments 

could occur in Alaska, Nebraska, and Texas. Based on 

the HHRA and ERA, the risks to recreationists and 

sensitive species from these new herbicides, in many

cases, are less than risks associated with currentlyavailable herbicides, such as 2,4-D, hexazinone, and

triclopyr. The Alaska BLM does not anticipate using 

herbicides on public lands, and public lands in Nebraska 

and Texas are not associated with wilderness or other 

special areas. 

Alternative C – No Use of Herbicides 

Alternative C would have the benefit of protecting

wilderness and special area users, sensitive species, and 

other resources from accidental exposure to herbicides. 

However, there are certain plants that could be injurious 

to humans, which are most easily controlled or 

eradicated using herbicides (e.g., Russian knapweed, 

purple loosestrife, Canada and Scotch thistles, yellow 

star-thistle). Therefore, Alternative C could negatively

impact activities in wilderness and special areas,

particularly camping, hiking, and other activities that

would present opportunities for easy contact with these

noxious weeds. Visitation to these lands could be lower 

than under the Preferred Alternative, and greater 

concentrations of visitors could occur in other 

wilderness and special areas, resulting in greater impact

to these areas. 

If other treatment methods were used in place of

herbicides, these methods could have a greater impact

on wilderness and special area values. For example,

prescribed burning would be more likely to result in

restricted access by recreationists, decreased air quality,

more dramatic changes in the visual landscape for a

longer period of time, and shorter visit times by

recreationists and sightseers. In addition, it is likely that

fewer acres would be treated in highly visible areas 

overall (as a result of the adverse visual and air quality 

impacts of prescribed burning), meaning that over the 

long term these areas would remain of a lower 

ecosystem quality. Fire use would also displace

sensitive wildlife and could lead to erosion that impacts 

fish habitat. 

Alternative D – No Aerial Applications 

Aerial spraying would be uncommon in wilderness and

special areas under all treatment alternatives. By 

prohibiting aerial spraying, Alternative D would likely 

limit the number of acres that could be covered by a 

single treatment. This limit to acreage could have the 

benefit of reducing the acreage of lands that are

temporarily closed to wilderness use. Furthermore,

wilderness and special areas and their values could be 

disproportionately negatively affected by this alternative 

if prescribed burning were to increase as a result of

fewer larger-scale areas being treated with herbicides.

Hunting, camping, backpacking, horseback riding, and

other wilderness pursuits would be limited in burned

areas, and possibly shifted to other areas. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Several components of Alternative E pertain to

wilderness and special areas (see Appendix I). As

discussed in the other resource sections, fewer acres 

would be treated under this alternative than under the

Preferred Alternative and Alternative D. While fewer 

treated acres would tend to result in fewer negative and 

positive impacts, an increased emphasis on ecosystembased management techniques under Alternative E 

would tend to decrease the short-term negative benefits 

and possibly increase the long-term positive benefits 

associated with this alternative. Limits on herbicide use

in riparian areas under this alternative would minimize 

the potential for direct and indirect harm to riparian

vegetation, aquatic animals, and water quality. 

BLM Vegetation Treatments Using Herbicides 4-158 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Under Alternative E, the following restriction would be

implemented: “except for treatment of small infestations 

without motorized equipment, prescribe treatments 

within designated wilderness or wilderness study areas 

only after the spread of invasive species from outside 

these areas has been effectively halted” (see Appendix 

I). Under the other treatment alternatives, however,

actions could be taken to control invasive species within

wilderness and special areas before controlling invasive 

species populations outside special areas. The BLM 

policy is to treat infestations where they are found and 

to prevent their further spread. By not treating an 

infestation in a wilderness or other special area until the

larger invasive species problem outside of the area is 

addressed, invasive species populations within

wilderness and special areas could grow beyond an 

effectively treatable level. 

The five herbicides (chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, and sulfometuron methyl) that

would not be used under this alternative are some of the 

least risky herbicides with respect to human health (see

Human Health and Safety section). In addition, the 

ERAs predicted no risk to fish and terrestrial wildlife 

from most ALS-inhibiting herbicides (chlorsulfuron, 

imazapic, sulfometuron methyl), and a low risk in a few 

scenarios (imazapyr, metsulfuron methyl), suggesting 

that the elimination of these herbicides would not likely 

benefit wildlife and could indirectly harm wildlife in

wilderness and special areas if more toxic herbicides 

were used in their place (see Wildlife Resources 

section). The other herbicides proposed for use by the 

BLM pose risks to non-target plants that are similar to

those associated with these five herbicides; therefore, it

is uncertain whether this use restriction would actually

reduce risk to non-target plants. Thus, avoidance of 

ALS-inhibiting herbicides might provide few, if any, 

benefits to wilderness and special areas and special area

users. 

Mitigation for Herbicide Treatment 

Impacts 

Mitigation measures that may apply to wilderness and

special area resources are associated with human and

ecological health and recreation. Please refer to the 

Vegetation, Fish and Other Aquatic Resources, Wildlife

Resources, Recreation, and Human Health and Safety

sections of this chapter. 

Recreation 

Approximately 40% of public lands are within a day’s

drive of 16 major urban areas in the West (USDI BLM

2005a). Outdoor recreation, nature, adventure, and

heritage tourism are the fastest growing segments of the 

travel and tourism industry Recreational use of public 

lands consists predominately of camping and

picnicking, which represented 43% of all visitor days in 

2005 (USDI BLM 2006d). Other important recreational

activities included non-motorized travel, such as hiking, 

horseback riding, and mountain biking; OHV travel;

viewing public land resources and interpretation and 

education; and hunting. Snow- and ice-based activities, 

such as cross-country skiing, snowmobiling, and

snowshoeing represented less than 1% of visitor days. 

The BLM administers many acres of public lands and 

facilities at least in part for these recreational pursuits. 

Many of these lands are managed for multiple uses; 

activities designed for one program or purpose (e.g., 

vegetation control/enhancement) must be compatible

with other programs and purposes. 

Less than 1% of the acreage considered in this PEIS 

consists of intensively managed, developed recreation 

areas that tend to have high public visitation. Many of 

these areas are near major urban areas in California, 

Arizona, and Utah, and include National Monuments 

and other National Conservation Areas (see Map 3-12).

In these areas, the goals of vegetation treatments include 

maintaining the appearance of the area and protecting 

visitors from the adverse effects of contact with noxious

weeds and other invasive/unwanted species. Treatments 

would likely be done using mechanical and manual

methods, or with spot treatments using herbicides, and 

treatment effects on the public would be minimal. 

However, herbicide treatments would be more likely 

with increasing distance away from high-use visitor 

areas. Thus, hikers, hunters, campers, horsemen, 

livestock owners, and users of plant resources for 

cultural, social, and economic purposes would be at the

greatest risk of coming into contact with herbicide

treatment areas. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Several respondents remarked that treatments should 

not be used as an excuse to close OHV trails. Another 

commentor requested that areas not be treated solely to

improve recreational use. If treatments require any

travel or access routes to be closed, the impacts on

BLM Vegetation Treatments Using Herbicides 4-159 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

recreation and nearby areas that would handle the shift 

in use should be addressed. The effects of herbicides on 

recreational users should also be addressed. 

Standard Operating Procedures 

There are several SOPs that could help reduce the

negative impacts of herbicide treatments on recreation: 

• Schedule treatments to avoid peak recreational 

use times, while taking into account the

optimum management period for the targeted 

species. 

• Notify the public of treatment methods, 

hazards, times, and nearby alternative 

recreation areas. 

• Adhere to entry restrictions identified on the

herbicide label for public and worker access. 

• Post signs noting exclusion areas and the 

duration of exclusion, if necessary. 

• Use herbicides during periods of low human

use, where feasible. 

In addition, SOPs identified in the Human Health and 

Safety, Fish and Aquatic Resources, and Wildlife 

Resources sections should be implemented to further 

reduce risks to recreationists and the resources they use.

Summary of Herbicide Impacts 

Vegetation treatments would have short-term negative 

impacts and long-term positive impacts on recreation.

During treatments, there would be some scenic 

degradation, as well as distractions to users (e.g., noise 

from machinery). In addition, there would be some

human health risks to recreationists associated with 

exposure to herbicides. These risks are discussed in

more detail in the Human Health and Safety section. 

Finally, some areas would be off-limits to recreation 

activities as a result of treatments, generally for a few 

hours or days, but potentially for at least one full

growing season or longer depending on the treatment. In

most cases, recreationists would be able to find 

alternative sites offering the same amenities, but a 

lessened experience could result if concentrated use 

occurred in these alternative sites. 

Site closures would generally last for a short time period

following herbicide application, depending on the

recommendations on the herbicide label. Usually the 

recommended exclosure periods would not exceed 24 

hours; however, recreational access could be restricted 

for a season or more to allow vegetation to recover 

following treatment. 

During site closures, signs would be posted stating the

chemical used, the date of application, and a contact 

number for more information, and would remain in 

place for a period of at least 2 weeks following

treatment. Dead brown vegetation could temporarily 

reduce recreational potential until vegetation recovered, 

although in most cases any substantial amounts would 

be removed to avoid hazardous fuels build up. Chemical

treatments could also pose some health risks to

recreational users, which would be greatest for aerial

herbicide applications, and to users engaging in

activities such as ingesting berries or fish (see Human

Health and Safety section). Chemical treatments would 

generally result in long-term benefits to recreationists 

by controlling noxious weeds and other unwanted 

vegetation and improving plant species diversity. 

Herbicide use would likely negatively impact

sightseeing recreational opportunities, as further 

discussed in the Visual Resources section. 

Developed recreation sites with public facilities would

be treated in order to maintain the appearance of the

area and to protect visitors from the adverse effects of

unwanted vegetation (e.g. thistles, ragweed, and poison

ivy). Long-term adverse effects on developed

recreational facilities would be unlikely, as treatments 

are expected to improve the vegetative health and utility 

of these sites. In some cases, developed recreation sites 

could be temporarily closed during treatment

implementation. 

Dispersed recreation in non-developed areas would 

potentially be affected to a greater degree than 

recreation in developed sites because most of the 6 

million acres of vegetation treatments would occur in 

these undeveloped, dispersed areas. Recreational 

activities in these areas are spread out across the

landscape, and different types of recreational activities 

would be affected differently. Impacts to recreation in

areas with a greater abundance of recreational

opportunities (e.g., Alaska) would not be as significant

as impacts to areas with less extensive recreational 

opportunities. However, over the long term,

recreationists in these dispersed recreation areas would

likely benefit from a reduction in invasive plants, 

especially thorny or poisonous noxious weeds, provided 

by herbicide treatments. In addition, herbicide 

treatments that reduce the risk of wildfire would reduce 

the likelihood of recreationists being displaced from 

favorite hunting, fishing, and camping sites by wildfires. 

BLM Vegetation Treatments Using Herbicides 4-160 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

During the recent wildfires that swept through the Great 

Basin, not only were traditional recreation activities

affected, but some special events were altered or

cancelled. Signs were destroyed, hiking and camping

areas burned over, wildlife and game displaced, and the 

scenery in the Great Basin marred (USDI BLM 1999). 

Recreational use of motorized vehicles on public lands

is typically limited to designated routes and trails. Trails

located in areas of vegetation treatments would be 

closed during treatments and for a period of time 

following treatments to allow vegetation to recover. 

Closures could last for several growing seasons 

following more intensive treatments involving complete 

removal of vegetation was completely removed, while

less intensive treatments may not require site closures 

beyond what is recommended for safety on herbicideuse labels. 

The effects of herbicide treatments on fish and wildlife

could have indirect negative impacts on recreational

activities such as fishing, hunting, and wildlife viewing. 

For example, aerial application of an herbicide over a

large area could adversely affect these types of

recreation activities by harming or displacing game and 

non-game fish and wildlife species. 

Vegetation treatments could also impact scenic views, 

particularly large treatments next to roads. The effects

of vegetation management on the visual quality of the 

landscape are discussed further in the Visual Resources 

section.

The impacts of individual herbicides on recreation

would differ primarily based on human health risks to 

recreationists and short-term recreation area closures. 

The Human Health and Safety section describes the 

potential risks to different types of recreationists (e.g., 

hikers, hunters, anglers, swimmers, and plant collectors) 

associated with exposure to different herbicides. 

Herbicide-use labels present the minimum period of 

time that a sprayed site must be closed to humans. The 

longer a site is closed, the greater the adverse effect to

recreationists in terms of lost use days, particularly at

sites that experience a higher volume of visitors. 

Because most mandatory site closure periods are less 

than 24 hours, it is expected that the impacts would be 

minimal, particularly if treatments were scheduled 

during a period of low visitation. On sites experiencing 

more extensive treatments, however, longer closures 

could be required to allow vegetation to recover. 

Unintended impacts of herbicides on non-target plants

and animals could impact recreation activities (e.g., 

hiking, plant collecting, hunting, and fishing) in off-site 

areas. The risks to non-target species from use of the 

evaluated herbicides are discussed in the Vegetation, 

Fish and Aquatic Resources and Wildlife Resources 

sections. The longer an herbicide lingers in soil

(depending also on its ability to bind to soil [Koskinen

et al. 2003]), the more likely it is to contaminate 

groundwater or run off into water bodies used by

recreationists. 

Over the long term, herbicide treatments would have a 

positive effect on recreation on treated lands. Removal 

of weedy vegetation would return public lands to a more 

“natural” or “desirable” condition, which hikers and

nature enthusiasts would likely value over degraded

lands. In addition, the increased aesthetic value of 

treated sites would benefit most recreational users. In

some instances, treated sites could become more

desirable as destinations for outdoor activities, making

them more popular to recreational users. In addition, 

fuels reduction treatments would reduce the likelihood 

of future wildfires on public lands used for recreation. 

As a result, recreationists would be provided with safer 

conditions, and there would be less of a chance that a 

wildfire would burn a large acreage of lands used for 

recreation. Where wildfires do occur, they are capable

of causing damage to recreational resources in large

areas and affected sites require long periods of time for 

recovery. Treatment of sites to restore native vegetation

would enhance fish and wildlife habitat, to the benefit of 

hunters, birdwatchers, and other users of these 

resources. 

Impacts by Alternative 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Impacts to recreation areas under the No Action

Alternative as a result of herbicide treatments would be 

similar to those that are currently experienced. 

Assuming a steady increase in number of recreational

users of public lands (although numbers of recreational

visitors have held steady or trended slightly downward

in recent years), there would be more impact to lands 

from human activities (e.g., spreading weeds, starting

fires), but the same level of treatment. Developed and

undeveloped recreation lands that are dominated by

invasive species are usually less visually appealing and 

less attractive to recreationists than areas that support

native plant communities. 

BLM Vegetation Treatments Using Herbicides 4-161 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Most treatments would occur in New Mexico (32%), 

Idaho (19%), Wyoming (12%) and Nevada (8%). 

Although these states would account for 71% of 

treatment acres, they accounted for only 20% of visitor 

days during 2005 (USDI BLM 2006d). Thus, the 

likelihood of visitors to public lands coming into contact

with herbicide treatment areas would be minor, as 

treatments would occur in states with relatively few 

visitors. 

The No Action Alternative would treat only a third of 

the acreage treated under the Preferred Alternative, and 

therefore would fall short of the Preferred Alternative in 

its ability to treat vegetation and generate positive

benefits for recreation lands and users, but would also 

have fewer negative impacts on recreation associated 

with herbicide treatments. In addition, per capita

vegetation treatments would not likely be as effective in

restoring recreation lands because the No Action

Alternative would not allow the use of the four new 

herbicides evaluated in this PEIS. Because fewer total 

acres would be treated under this alternative than under

the other herbicide treatment alternatives, this 

alternative might have fewer long-term recreation

benefits than the other treatment alternatives, if a greater

amount of treatment acres were to translate to a greater 

improvement of ecosystem health and scenic quality. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

Because Alternative B involves the largest number of

treatment acres, it could also have the largest short-term

adverse impact on recreation, primarily by resulting in 

the temporary closure of more lands. Along with these 

closures, there might be more lost opportunities for 

collection of plant materials than under other 

alternatives. Because of the large number of treatment 

acres, however, this alternative could have the largest 

positive impact on recreation, since it would reduce the

risk of visitor contact with undesirable plant species and 

would increase visitor exposure to desirable plants and 

wildlife over the largest acreage possible. As a result, 

recreation hours spent at a given site could be greatest

under this alternative. 

Under the Preferred Alternative, most treatments would

occur in Idaho (28%), Nevada (22%), Wyoming (16%), 

and New Mexico (10%). Although these states account 

for 76% of treatment acres, they accounted for only 

20% of visitor days during 2005 (USDI BLM 2006d). 

Thus, the likelihood of visitors to public lands coming

into contact with herbicide treatment areas would be 

minor, as treatments would occur in states with 

relatively few visitors. 

Under this alternative, four new herbicides would be 

available for use by the BLM, and herbicide treatments 

could occur in Alaska, Nebraska, and Texas. Based on 

the HHRA, the risks to recreationists from these new 

herbicides, in many cases, are less than risks associated

with currently-available herbicides, such as 2,4-D, 

hexazinone, and triclopyr. Although the Alaska BLM

does not anticipate using herbicides on public lands, 

treatments in Nebraska and Texas could potentially

affect recreational users in those states. 

Alternative C – No Use of Herbicides 

Alternative C would have the positive benefit of 

protecting recreationists from accidental exposure to

herbicides. However, certain plants that can be injurious

to humans are most easily controlled or eradicated using 

herbicides (e.g., Russian knapweed, purple loosestrife,

Canada and Scotch thistles, yellow star-thistle). 

Therefore, Alternative C could negatively impact

recreation activities, particularly camping, hiking, and 

other activities that would present opportunities for easy 

contact with these noxious weeds. Over 900,000 acres 

treated under the Preferred Alternative would not be

subject to herbicide treatment under this alternative. As 

a result, these areas could have fewer recreationists 

because of dominance by undesirable plant species. 

Visitation to these lands could be lower than under the 

Preferred Alternative, and higher concentrations of 

visitors could occur in other areas, resulting in greater 

impacts elsewhere. 

Furthermore, if other treatment methods were used in

place of herbicides, these methods could have a greater

impact on recreation. For example, prescribed burning 

could result in restricted access by recreationists,

decreased air quality, and more dramatic changes in the

visual landscape for a longer period of time. In addition,

it is likely that fewer acres would be treated in highly 

visible areas overall (as a result of the adverse visual

and air quality impacts of prescribed burning), meaning

that in the long term these areas would remain of a 

lower ecosystem quality, limiting their attraction to 

recreationists.

Alternative D – No Aerial Applications 

It is unlikely that aerial spraying would occur in high 

public use recreational areas under any of the 

alternatives, but aerial spraying would occur in 

dispersed use areas under the No Action Alternative, 

BLM Vegetation Treatments Using Herbicides 4-162 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Preferred Alternative, and Alternative E. By prohibiting

aerial spraying, Alternative D would also likely limit the 

number of acres that could be covered by a single 

treatment. This limit could have the benefit of reducing 

the acreage of lands that are temporarily closed to 

recreation. Furthermore, dispersed recreation (i.e., 

recreation in non-developed areas) could be 

disproportionately negatively affected by this alternative 

if prescribed burning were to increase as a result of

fewer larger-scale areas being treated with herbicides.

Hunting, camping, backpacking, horseback riding and 

other pursuits would be limited in burned areas, and 

possibly shifted to other areas. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Under Alternative E herbicide treatments would result

in impacts similar to those under Alternative D, with

slightly fewer acres being treated and a reduced, though

not eliminated, emphasis on aerial spraying. While 

fewer treated acres (over Alternative D) would tend to 

correspond to fewer impacts, an increased emphasis on

ecosystem-based and passive management techniques

under Alternative E would tend to decrease the shortterm negative effects and possibly increase the longterm positive benefits associated with this alternative. 

For example, because spot treatments would be favored 

over broadcast treatments, Alternative E would limit the 

negative short-term impacts to recreationists from drift

of herbicides into off-site areas that have not been 

temporarily closed to visitors. In addition, limits on

herbicide use in riparian areas would minimize the 

potential for direct and indirect harm to riparian

vegetation, aquatic animals, and water quality. As 

compared to the Preferred Alternative, however, this 

alternative would treat substantially fewer acres, 

resulting in fewer long-term improvements to the 

environmental quality of recreation sites. 

The five herbicides (chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, and sulfometuron methyl) that

would not be used under this alternative are some of the 

least risky herbicides with respect to human health (see

Human Health and Safety section). In addition, the 

ALS-inhibiting herbicides either pose no risk to

terrestrial wildlife (chlorsulfuron, imazapic,

sulfometuron methyl), or low risk (imazapyr, 

metsulfuron methyl), suggesting that eliminating the use

of these herbicides would be unlikely to benefit fish and

wildlife and could indirectly harm fish and wildlife if 

more toxic herbicides were used in their place (see Fish

and Other Aquatic Resources and Wildlife Resources 

sections). Thus, there would likely be few, if any,

benefits to anglers and hunters and other recreationists. 

Mitigation for Herbicide Treatment 

Impacts 

Mitigation measures that may apply to recreational

resources are associated with human and ecological

health. Please refer to the Vegetation, Fish and Other 

Aquatic Resources, Wildlife Resources, and Human

Health and Safety sections of this chapter. 

Social and Economic Values 

Introduction 

Herbicide treatments have the potential to affect people,

communities, and economies in each of the 17 western

states that could receive treatments. The susceptibility 

of these entities to social and economic effects stems 

from the importance of public lands to the lives of the 

people and communities in the West, especially in the 

states with the largest amounts of public land. Public 

lands commonly provide a major portion of economic 

sustenance, especially in rural areas, by supporting 

ranching (grazing leases), mining, active and passive 

recreation opportunities, and a myriad of other activities 

that westerners rely on. The dollar value of the social

sustenance may not be readily quantifiable, but it, too, is

important to the way of life of westerners. “Wide open

spaces” are not just a cliché in western songs and 

novels, they are a tangible part of the experience that 

attracts and/or retains people who live in western states. 

The large expanses of federal lands are a significant 

contributor to the open spaces that define the “sense of

place” in many parts of the West. Through support of 

economies and the social context of the West, federal

lands are highly important to the western states. Actions 

that affect federal lands, such as the application of 

herbicides, have the potential to affect the economic and

social environment of the region. 

The extent of potential effects would vary from state to

state because of the differing prevalence of federal lands 

and also because the treatment area in each state would

vary, both in acreage and in percentage of land area 

treated, depending on local issues and needs. The most

pervasive effects would likely occur in states with large

amounts of public land. During 2002, information was 

gathered from BLM field offices on the general location

of herbicide treatment projects likely to occur under the 

No Action and Preferred alternatives. Based on this

BLM Vegetation Treatments Using Herbicides 4-163 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

information, nearly two-thirds of herbicide treatments 

proposed under the Preferred Alternative would occur in 

Idaho, Nevada, and Wyoming, with the largest increases 

in herbicide use from current levels likely to occur in

Nevada. 

This EIS is programmatic in nature and very broad in

scale. A programmatic analysis at this scale does not

permit the completion of a detailed, quantitative social

and economic analysis. Therefore, only general effects 

and expected trends will be addressed here. Concerned 

individuals should be assured that more detailed, sitespecific analyses would be conducted during the 

development of actual herbicide treatment projects. 

Public participation in developing the details of such 

proposals would be encouraged at appropriate times in

those processes. 

Scoping Comments and Other Issues 

Evaluated in the Assessment 

Among the major concerns identified during scoping, 

were suggestions that economic and ecological costs 

and benefits to local communities and residents should 

be examined. Some individuals proposed that the

BLM’s needs for people and fiscal resources should be

addressed, as should costs to state and local

governments and private individuals, including

secondary costs from such things as loss of recreational

use activities. Environmental justice issues—

disproportionate effects on minorities, low-income, and 

child populations —and Indian Trust issues were raised. 

Several comments addressed potential economic effects 

on ranchers from grazing restrictions or changes to

forage productivity, while others questioned whether 

grazing permittees would pay for a portion of the 

treatment costs. A few respondents questioned whether 

the BLM would perform the treatment work or contract 

it out; others proposed contracting to local vendors. 

Some were concerned about potential economic effects 

on local fire fighters. Evaluation of the effects of the 

herbicide use alternatives, both beneficial and

detrimental, will address these issues to the greatest

degree possible, given the scale of the potentially

affected geographic area and the necessarily inexact 

nature of the alternatives in advance of specific

treatment project proposals. 

There are numerous stakeholders throughout the

western U.S. with differing needs and perspectives, and 

all of their interests must be taken into consideration 

when planning the treatment program. On a local level,

stakeholders include people in communities located in

the vicinity of public lands, such as adjacent 

landowners, local businesses, and users of public lands 

(e.g. ranchers and recreationists), as well as the counties 

and states that benefit from BLM revenues. On a 

national level, the stakeholders include all taxpayers, 

whose tax dollars support BLM programs and who have 

partial “ownership” of federal public lands. Given the

wide range in stakeholders whose needs and interests 

must be considered, many different and often

conflicting opinions must be considered. The alternative 

selected for implementation will be one that balances 

both national and local interests. 

Standard Operating Procedures 

Herbicide use would affect local social and economic

resources; some effects would be adverse. Following

selected SOPs would reduce some of the adverse

effects. The following general procedures are designed 

to reduce potential adverse impacts to social and

economic conditions from the application of herbicides 

in the BLM vegetation management program: 

• Consider surrounding land use before selecting 

aerial spraying as a method, and avoid aerial

spraying near agricultural or densely-populated 

areas. 

• Post treated areas and specify reentry or rest

times, if appropriate. 

• Notify adjacent landowners prior to treatment. 

• Notify grazing permittees of livestock feeding 

restrictions in treated areas if necessary, as per 

label instructions. 

• Notify the public of the project to improve

coordination and avoid potential conflicts and 

safety concerns during implementation of the 

treatment. 

• Control public access until potential treatment

hazards no longer exist, per label instructions. 

• Observe restricted entry intervals specified by 

the herbicide label. 

• Notify local emergency personnel of proposed 

treatments. 

• Avoid aerial spraying during periods of adverse 

weather conditions (imminent snow or rain, 

fog, or air turbulence). 

• During helicopter applications, apply 

herbicides at an airspeed of 40 to 50 miles per 

BLM Vegetation Treatments Using Herbicides 4-164 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

hour (mph), and at an elevation of about 30 to 

45 feet above ground. 

• Comply with herbicide-free buffer zones to

ensure that drift will not affect crops or nearby 

residents/landowners. 

• Use spot applications or low-boom broadcast

applications where possible to limit the 

probability of contaminating non-target food

and water sources, especially vegetation over 

areas larger than the treatment area. 

• Consult with Native American tribes and 

Alaska Native groups to locate any areas of 

vegetation that are of significance to the tribe

and that might be affected by herbicide 

treatments. 

• Work with Native American tribes and Alaska 

Native groups to minimize impacts to these 

resources. 

• To the degree possible within the law, hire

local contractors and workers to assist with 

herbicide application projects. 

• To the degree possible within the law, 

purchase materials and supplies, including 

chemicals, for herbicide treatment projects 

through local suppliers. 

• To minimize fears based on lack of 

information, provide public educational

information on the need for vegetation

treatments and the use of herbicides in an

Integrated Pest Management program for 

projects proposing local use of herbicides.

These procedures would help minimize impacts to

people, communities, and human activities in the

vicinity of herbicide treatment projects on public lands 

in the 17-state study region. 

Impact Assessment Assumptions 

The social and economic analyses for the application of 

herbicides are guided by a number of key assumptions. 

First and foremost, this is a 17-state PEIS with no sitespecific information on which types of herbicides would 

be used in any particular area. Consequently, there will

be little or no discussion of specific application 

parameters; any such discussion will be strictly to

provide examples. It is expected that communities that

are particularly dependent on a single industry are more 

susceptible to the effects of herbicide use than other 

communities. In particular, ranching communities and

recreation-dependent communities may be more

affected than more diversified communities. However, 

it is not possible to identify particular communities at

this scale of analysis. More specific analysis of the

effects to communities would be conducted when 

individual projects were proposed, and the analysis

would consider elements cited in this section. 

The proposed use of herbicides would only apply to

public lands; this PEIS does not attempt to predict

possible decisions or actions by other agencies or

private individuals. Also, it is not expected that any of 

the alternatives would significantly affect ongoing,

long-term trends such as the increasing demand for 

outdoor recreation or growth in urban, suburban and

rural populations, particularly in states from the Rocky 

Mountains to the Pacific. 

It is assumed that herbicide treatment alternatives would

meet, to different degrees, the need for the proposed 

action (i.e., reduce the risk of wildland fire and improve 

ecosystem health). Herbicide treatments would reduce 

the risk of wildland fire by reducing hazardous fuels to

reduce the size and severity of wildland fires. In turn, 

the cost of wildland fire suppression and the loss of life 

and property would be reduced. Treatments that

improve ecosystem health could increase or improve the

amount and quality of commercial and casual uses, 

improve or maintain market and non-market values of 

existing uses, and reduce the cost of operations on 

public lands. However, it was not possible to quantify

these benefits at this programmatic level of analysis, 

since there is uncertainty as to when, where, and how 

treatments would occur. 

Summary of Herbicide Impacts 

Social effects of the individual herbicides are, for the

most part, impossible to differentiate at the scale 

addressed by this PEIS. The potential for differing

social effects among the chemicals would derive from 

people’s perceptions of different health and safety risks 

for different chemicals. Data on such perceptions are 

not available, and, in fact, could differ from one 

community to another, depending on the level of

knowledge about herbicides in the community and

possible past experiences with their use (or “misuse,”

such as accidental spills or damage to non-target plants). 

The Human Health and Safety section in this chapter

discusses health and safety issues related to the 

proposed herbicides in more detail. There is also some

potential for beneficial or adverse effects on the social

fabric of communities depending on the success or

BLM Vegetation Treatments Using Herbicides 4-165 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

failure of vegetative treatment programs using various 

chemicals. Successful improvement in the productivity 

of rangeland, for example, would help sustain a 

ranching-dependent community, whereas lack of

success could put additional pressure on often tight

economic margins in ranching, which would tend to

encourage out-migration. Successfully reducing 

hazardous fuels in the WUI could encourage people to 

remain in, or move to, a community, whereas major fire

losses, particularly in smaller communities, could 

encourage some people to move away. These potential 

effects are somewhat speculative, but should be

examined more closely at the project-specific level. 

Economic effects of individual herbicides on 

communities could be similar to social effects. Changes 

in range productivity, wildfire risk, and access or

attractiveness for recreation activities could potentially 

affect employment opportunities and income levels in a

community, in either a positive or negative fashion. As 

with social effects, however, the broad scale of this 

PEIS and the lack of data preclude the ability to

accurately predict whether and where such effects 

would occur, and whether they would be beneficial or 

adverse. 

There would be direct and indirect economic effects 

from application of herbicides. These effects would

vary, depending on the quantities of each herbicide 

selected for use and the methods of application for each. 

Table 3-23 illustrates the dramatic differences in costs 

associated with the various herbicides used in 2005, 

which ranged from approximately $1 per acre for 

tebuthiuron to almost $127 per acre for bromacil. 

In addition to the chemical costs, there would be costs 

for applying the herbicides. The USDA Forest Service

(2005) estimated the average cost per acre for 

application at $100 for ground application and $25 for 

aerial application. The BLM’s range of estimated 

application costs is even broader. For ground

applications, the BLM’s estimates range from $50 to

$300 per acre for backpack or ATV applications, and

$25 to $75 per acre for boom sprayer applications.

Aerial applications are estimated at $6 to $40 per acre 

for fixed-wing aircraft and $25 to $200 per acre for 

helicopter applications. The differences are largely due 

to the variation in labor and time required to cover an 

acre by each application mode. It takes many more

man-hours to treat an acre on foot or from a small ATV, 

for example, than to treat an acre with an aircraft. At

best, all of these estimates are crude averages; actual

costs would vary widely, dictated by terrain, scale of the 

treatment project, accessibility of the treatment area,

size of the problem vegetation stand being treated, and 

other factors. None of the specifics of these factors are

available for evaluation at the programmatic level, but 

they would be analyzed in greater detail for specific

projects as they were developed. 

The source of labor for the applications, included in the 

application cost, would vary with the project. Aerial

application projects would be contracted out in most 

cases. Ground applications would be done by a 

combination of contractors and BLM personnel, either 

full-time or part-time employees. The determination of

in-house or contract application would be determined 

for each project individually, depending on the specific

needs of the project and the capabilities of the state or

local BLM office. 

Purchase of chemicals and contracting of applications 

would generate dollars to benefit the economy; the 

location of the benefit would depend on where the 

chemicals and contractors were obtained. Locally 

purchased chemicals would generate more local benefit, 

for example, whereas mass purchase of chemicals from

a state or national distributor would likely have little

local benefit. Herbicide application would tend to

sustain local employment, and, in some cases, provide 

temporary employment for others. 

Impacts by Alternative 

Impacts Common to All Alternatives 

Population and Demography 

None of the five alternatives being analyzed are likely 

to cause substantive changes to existing patterns and 

trends in population or demographic conditions in the 

western states. While there would be some increased 

employment generated by the increase in BLM acreage

treated with herbicides under each of the alternatives, 

the jobs would generally be short-term, temporary 

positions or contracted work, which would not be

sufficient to encourage measurable in-migration of 

workers and their families. With few exceptions, 

perhaps including pilots and certified herbicide 

applicators, jobs generated by the increased herbicide

treatments program would tend to pay moderate wages. 

Depending on the size and duration of any particular 

treatment project, there could be small, localized

population increases, but it is not possible to ascertain if, 

or where, such changes would take place at this time. It

is unlikely that any such growth would excessively

burden the community in which it would occur because 

BLM Vegetation Treatments Using Herbicides 4-166 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

the growth would be small, even in the context of the 

rural West. 

Environmental Justice 

Executive Order No. 12898, “Federal Action to Address 

Environmental Justice in Minority Populations and 

Low-Income Populations” (59 FR 7629), is “intended to

promote nondiscrimination in federal programs 

substantially affecting human health and the 

environment, and to provide minority communities and

low-income communities access to public information

on, and an opportunity for participation in, matters 

relating to human health and the environment.” It

requires each federal agency to achieve environmental

justice as part of its mission by identifying and

addressing, as appropriate, disproportionately high and

adverse human health or environmental effects, 

including social and economic effects, of its programs, 

policies, and activities on minority and low-income

populations. 

Environmental justice concerns are usually directly

associated with impacts on the natural and physical

environment, but these impacts are likely to be

interrelated with social and economic impacts as well.

Native American and Alaska Native access to cultural

and religious sites may fall under the umbrella of

environmental justice concerns if the sites are on tribal 

lands or a treaty right has granted access to a specific

location. 

USEPA guidelines for evaluating potential adverse 

environmental effects of projects require specific 

identification of minority populations when either: 1) a 

minority population exceeds 50% of the population of 

the affected area, or 2) a minority population represents

a meaningfully greater increment of the affected

population than of the population of some other 

appropriate geographic unit. 

Public lands occur predominantly in rural areas. There

are large minority populations in rural areas of the West

and Alaska, particularly Hispanics and Native 

Americans. Approximately 63% of the nation’s 

Hispanic population, 68% of the nation’s American

Indian population, and 50% of the nation’s 

Asian/Pacific Islander population reside in the western

U.S., which contains less than 32% of the nation’s total 

population (Table 3-15). In addition, Hispanics 

represent a high percentage of the total population of

some states, including New Mexico, California, Texas, 

and Arizona, in particular. Similarly, Alaska, New 

Mexico, and several other western states have

disproportionately high percentages of Native 

Americans and Alaska Natives. Issues of concern might 

include the propensity of Native Americans and Alaska 

Natives to use native plants for cultural and traditional 

purposes, and the potential for herbicides to damage 

some of these native plants if projects are not carefully 

planned and implemented. This combination of factors 

suggests the possibility that any significant effects 

associated with herbicide use for vegetation treatments 

could disproportionately affect these minority 

populations. It is not possible to determine whether 

minorities or low income populations would actually be 

disproportionately affected at this broad scale of

analysis, however, because it is not known if treatment

areas would coincide with concentrations of minority or 

low-income populations, or with Native American and 

Alaska Native use areas. Specific evaluations of 

environmental justice impacts would be conducted in

concert with environmental analyses for site-specific

treatment project proposals. 

Issues specific to Native Americans, such as subsistence

gathering of rangeland products, have been addressed in

more detail in the Cultural and Paleontological

Resources section, but they must also be addressed in

detail with project-specific analyses. 

Protection of Children 

Executive Order 13045, Protection of Children from 

Environmental Health Risks and Safety Risks, instructs 

federal agencies to identify and assess environmental

health risks and safety risks that may disproportionately

affect children, and to ensure that their policies, 

programs, activities, and standards address

disproportionate risks to children that result from

environmental health or safety risks. Children could 

have a greater chance of being exposed to health and

safety risks associated with vegetation treatments than

adults because they typically spend more time outdoors, 

and because children, especially young children, tend to 

be more vulnerable to adverse effects from exposure to 

environmental contaminants. Although children may 

spend more time outdoors, they are not often on public

land without adult supervision because of the 

remoteness of most public lands. Thus, the increased

opportunity for exposure would generally be negligible 

to minor. If there are potential risks for adverse effects 

to people who happen to be outside in the vicinity of 

herbicide treatments, the project could have a 

disproportionate effect on children. 

BLM Vegetation Treatments Using Herbicides 4-167 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Employment and Income 

All of the vegetation treatment alternatives would result

in economic benefits to western states and local 

communities by providing employment and labor 

income opportunities. The BLM would require the

services of local pesticide applicators, pilots, and others,

creating jobs and generating income. The benefits are 

not quantifiable at the scale of this analysis; they would

be small in the context of the 17-state region, but could 

be more significant for some communities, depending 

on the expertise and availability of personnel in the

relevant BLM offices. Local effects cannot be

determined at the scale of this PEIS, but details of local

economic effects would be determined at the time

specific projects were analyzed under NEPA

regulations. Regardless of the local economic situation, 

the nature of treatments indicates employment and

related income effects would be short-term in nature 

and geographically dispersed, benefiting certain 

communities throughout the 17-state study area. In

general, it is expected that communities located in areas 

with large amounts of public lands, and therefore the 

most potential treatment acreage, would receive the

greatest employment and economic benefits. Idaho, 

Nevada, Wyoming, and New Mexico are the four states 

with the largest anticipated treatment acreage under 

each of the five alternatives, which suggests that

communities in these states would also be among the

largest beneficiaries of employment and income effects 

from the proposed herbicide program. Employment and 

income effects would have the greatest impact on

smaller communities, where the increase in jobs and 

dollars would have a greater influence on the area 

economy than it would in or near larger towns and 

cities. 

Perceptions and Values 

A range of stakeholder perceptions and values would be 

influenced by the herbicide treatment alternatives. For 

example, individuals who have an aversion to chemical

use in the environment could find all of the alternatives 

offensive, except Alternative C. Alternatively, 

individuals with a much greater concern about wildfires 

or the effects of invasive species would likely favor the 

most efficient means of attacking vegetation problems. 

Some westerners have philosophical issues with

government ownership and management of large land

areas, but they might be somewhat encouraged by plans 

to employ private contractors for some of the treatment 

work and would presumably favor the most efficient

means possible to reduce fire risk and improve range 

productivity. Some individuals place high values on the 

health and pristine nature of the land and would

therefore prefer to see that the least intrusive methods 

be implemented. All of the alternatives have similar 

negative and positive responses to these perceptions and 

values. A few differences are addressed below. 

Invasive Species Control Cost Savings 

Estimating the environmental and economic damages 

caused by invasive vegetation, and the environmental

benefits and cost savings from treating invasive

vegetation, cannot be quantified at the 17-state regional

scale. However, on a national scale, the costs of treating

invasive vegetation can be enormous. For example, 

purple loosestrife, which occurs in 48 states, costs 

approximately $45 million per year on control (ATTRA 

1997). A total of $100 million is spent annually in

aquatic invasive species control in the U.S. (OTA 

1993). In. U.S. agriculture, crop losses due to weeds are 

estimated at $24 billion annually, and costs of herbicide 

treatments are about $3 billion annually (Pimentel 1997, 

2005). Forage losses due to weeds total about $1 million

annually, and ranchers spend about $5 billion annually

to control invasive vegetation in pastures and

rangelands. Total direct and indirect costs of leafy 

spurge in Montana, South Dakota, and Wyoming is 

estimated at nearly $2 million annually on wildlands 

and up to $46 million annually for grazing lands 

(Bangsund and Leistritz 1991; Bangsund et al. 1993). 

Annual losses from knapweed in Montana are estimated

at over $40 million annually (Hirsch and Leitch 1996). 

The Research Group (2000) evaluated the impacts of 21

species of weeds and estimated that both existing and 

potential invasive weeds are costing Oregon about $100

million annually. 

Studies that have attempted to project the costs and

benefits of treating leafy spurge and yellow star-thistle 

have shown that benefits could total over $50 million or 

more annually if leafy spurge is controlled in the Great

Plains region (Bangsund et al. 1997, 1999a). Still, net

returns per acre are often negative early in the treatment

program, with gains in net return not seen until 10 years 

or more after treatment, with highest returns from 

ground spraying rather than aerial spraying programs 

((Bangsund et al. 1996, 1999b; Hartmans 1997). 

Kadrmas et al. (2003) estimated the cost of treating 50 

acres of public lands using a single application of

herbicides and single attempt at revegetation. The cost

of treating 50 acres of weeds was estimated at $7,500 at 

year 0. However, if the 50 acres were not treated and the

weeds continued to spread, weeds would cover an 

estimated 182 acres by year 18 and it would require 

BLM Vegetation Treatments Using Herbicides 4-168 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

approximately $27,000 to restore to a healthy 

ecosystem. 

Wildland Fire Cost Savings 

All of the herbicide treatment alternatives would

commit approximately half of the treatment acreage to 

hazardous fuels and invasive weed reduction in the 

WUI. Neither the suppression cost savings, nor the 

reduction in property losses can be quantified at the 17-

state regional scale. The potential savings should be 

addressed further in environmental reviews for specific 

projects, although they may not be quantifiable even at

that scale because of the number of variables 

contributing to when and where a fire may start and 

how much damage it may cause. These factors include

weather conditions, terrain, human acts of omission, and

structure type and density, among others. Further, it

may take several years to build a sufficient experience 

base of data to quantitatively estimate the benefits of 

vegetative treatment on wildfire suppression costs and

damage reduction. The Forest Service and BLM came

to similar conclusions when trying to ascertain the

effects of vegetation treatment activities on future fire

suppression costs in the Interior Columbia Basin

(USDA Forest Service and USDI BLM 2000). 

Despite the lack of quantifiable data, it is expected that

herbicide treatments in non-WUI areas would also

reduce hazardous fuels, including invasive weeds, 

which contribute disproportionately to fire risk. Downy 

brome provides one example of the potential cost 

savings from attacking invasive weeds, and the costs of 

fighting downy brome-fueled fires have been estimated

at around $20 million per year, and up to $15 million 

annually in southern Idaho alone, including 

rehabilitation costs (Duncan and Clark 2005). 

Consequently, it is expected that all of the alternatives 

would reduce the cost of fire suppression in the

backcountry as well as in the WUI. 

Economic Activity and Public Revenues

Generated from BLM Lands 

Commercial activities that occur on public lands could

be affected by vegetation treatments. Vegetation 

treatments would not directly affect mineral resources, 

but could temporarily reduce access to such resources.

Vegetation treatments would be unlikely to cause 

significant reductions in BLM revenues generated from

mineral leases. Most of the BLM’s mineral lease

revenues come from Alaska, Colorado, and Montana

(see Table 3-18), yet only about 8% of the herbicide

treatments would occur in these three states under the 

Preferred Alternative; herbicide treatments would not be 

allowed in Alaska under the No Action Alternative. 

Further, restrictions on access for these activities are 

likely to be minimal in most places because durable

road access is generally required for commercial

mineral extraction ventures. Consequently, adverse 

effects on employment and revenue from mineral

production due to herbicide treatments, if any, would 

likely be very minor. 

Historically, nearly all of the BLM’s revenues from 

timber sales came from Oregon. In 2005, timber sales 

amounted to $26.4 million and nearly all timber

revenues were from Oregon ($23.5 million, Table 3-18), 

where at most about 8% of all herbicide treatments are 

proposed to occur. Treatments would result in long-term 

improvements in the condition of forest resources and

would lead to increases in potential products and 

revenues generated from public lands over the long

term. However, the potential effects are not quantifiable 

at the scale of this PEIS. 

Effects on harvesting other vegetation (non-timber) 

products would depend on the product and the design of 

specific herbicide treatment projects. Indiscriminate

application of herbicides could damage resources or

reduce their value. Alternatively, herbicidal control of 

undesirable, invasive plants could enhance the habitat 

for desirable species. Public involvement in project 

planning and environmental review should be

encouraged to minimize adverse effects and maximize

benefits. 

Herbicide treatments would necessitate some site

closures to grazing activities during treatments and for a

suitable recovery period afterward, both for 

effectiveness of the treatment and for safety of the 

livestock. Treatments that require temporary rest from

grazing would result in a reduction in forage for 

livestock. Although alternative grazing sites may be 

available, the costs associated with grazing in a different

area would likely be higher. The economic effects of 

temporarily reducing forage production and/or access 

would vary depending on the size and flexibility of the

affected ranching operations. It is not possible to 

quantify the effects at the 17-state regional scale. 

Although forage production could decrease initially 

following treatment, production would likely increase 

over the long-term as woody vegetation and weed 

species were controlled, increasing the suitability of

rangeland areas for grazing. Treatments would result in 

an increased quantity and quality of forage, increased

animal production, reduced fire hazard, and a reduced

risk of sickness in livestock associated with ingesting

BLM Vegetation Treatments Using Herbicides 4-169 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

poisonous plants (see the Livestock section in this 

chapter for more information). As for other vegetation 

products, public involvement in project planning and 

site-specific environmental review should be 

encouraged to minimize adverse effects and maximize

benefits. 

Recreation-based businesses such as outfitters, bait

shops, OHV sales and repair shops, fish and hunting

shops, and outdoor gear and equipment rental shops are 

direct beneficiaries of recreational activity. Other 

services such as gas stations, restaurants, and hotels that 

are frequented by recreationists also benefit. Temporary 

closure of a popular recreation site, either to protect

public safety during herbicide treatments or to decrease 

user-related impacts during the site’s post-treatment 

recovery, would result in temporary losses of revenues 

to surrounding businesses. In most cases, these effects 

would be short term in nature, lasting only as long as the 

site closure. In general, most recreational activities 

would continue, but would shift to other locations (see 

the Recreation section in this chapter). Depending on

the location of the alternate use area, the economic 

benefits would shift from one community to another. If

there were a suitable nearby alternative to the closed 

site, the effects on surrounding businesses would be 

minimal; if not, the businesses would be adversely 

affected for a period of time. It is not possible to

quantify the potential effects at the 17-state regional 

scale, or to identify businesses that would benefit from

or be harmed by potential shifts in recreational

activities. Over the long term, an improvement in the

quality of a site from vegetation treatment could lead to 

increased recreational usage and a net increase in 

revenues to surrounding businesses. Reductions in

hazardous fuels and the risk of wildfires would benefit

the economies of rural communities, which are often

dependent on recreational and wilderness values. In 

some cases, severe wildfires, particularly those 

occurring during the tourist season, could cause longterm disruption to recreation values, which would

adversely affect recreational businesses. To the degree 

that treatments would reduce the risk of wildland fires, 

the herbicide treatment alternatives would benefit

recreation-related economic activity. 

Recreation provides revenues to the BLM through fees 

and permits. Closure of a popular fee-based recreation

site would result in a loss of revenues to the BLM. The

severity of any such losses cannot be determined at this 

scale because no specific fee-based recreation sites have 

been identified for treatment. Detailed effects would be

examined at the site-specific project level. 

Expenditures by BLM (Financial Efficiency) 

Herbicide treatments would require a large financial 

investment by the BLM, which would vary by

alternative. These costs represent a substantial input of 

financial resources into the communities surrounding 

BLM lands, particularly in areas where BLM landholdings are extensive. 

The most cost-effective alternative is the one that

produces the greatest benefits for the least amount of 

financial investment. The cheapest alternative, if it did 

not substantially improve the health of the land, could

require indefinite repeat treatments, thus costing more 

money over the long term. Unfortunately, it is not

possible to determine, on a 17-state regional scale, 

which broad alternative would be most cost-effective. 

Benefits to the health of the public lands depend on the 

specific problem to be addressed in each specific area. 

These benefits would be evaluated on a site-specific 

basis as project proposals were developed. Irrespective

of the particular alternative selected, the costs associated

with restoring or maintaining an ecosystem through 

vegetation treatments is generally much less than the

cost of suppressing wildfires and implementing fire 

rehabilitation programs (USDI 2001). 

An additional consideration regarding BLM 

expenditures is the distribution of payments to state and

local governments (see Table 3-24). None of the 

herbicide treatments would affect these payments, as 

they are established by Congress, and none of the 

alternatives would alter the formula-based payments. 

If goods and services were purchased locally, or 

additional workers were hired locally in support of the 

herbicide treatment alternatives, state and local

governments would benefit through increased tax 

revenues. The relative public benefits would depend on

the taxing structure of the individual states. 

Effects on Private Property 

Herbicide treatments could affect private property in the 

vicinity of public lands, particularly parcels adjacent to 

treatment areas. Over the short term, there would be

minor risks for property damage associated with 

herbicide treatments because it is possible that some

herbicide could drift onto private property, especially 

during aerial treatments. Under such a scenario, crops 

could be lost, or, alternatively, rangeland weeds could

be killed, resulting in benefits to private property. 

Losses and gains would likely be minor and short term 

in nature. 

BLM Vegetation Treatments Using Herbicides 4-170 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Over the long term, a reduction in hazardous fuels on

public lands would reduce the likelihood of wildfires 

migrating from public lands to nearby private property 

and impacting the WUI. Herbicide treatments would

also reduce the risks of noxious weeds spreading onto 

neighboring parcels, including poisonous weeds, which 

could harm livestock. A reduction in such risks could

lead to increased property values over the long term.

Any such effects are not quantifiable at this scale of 

analysis. 

Impacts of Individual Alternatives 

The following sections discuss the expected effects of

each of the five alternatives on social and economic

resources. These effects vary in degree, for the most

part, rather than in kind. The differences depend on the 

percentage of acres treated using different application

methods and on the total acreages to be treated. Because 

very little quantification of effects is possible at the 17-

state regional scale, the differences are often stated

roughly in proportion to the acreages to be treated. 

Alternative A – Continue Present Herbicide Use 

(No Action Alternative) 

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation treatment programs in

14 western states, and would be able to use 20

herbicides previously approved under earlier RODs. 

Approximately 305,000 acres would be treated with

herbicides annually. 

Since future treatment levels would be similar to current

levels, there would likely be little change to existing 

patterns and trends in population or demographic

conditions in the western United States. While there 

would be localized increases in employment generated

by the increase in BLM acreage treated with herbicides 

under this alternative, the jobs would generally be shortterm, temporary positions or contracted work, which

would not be sufficient to encourage measurable inmigration of workers and their families. 

Most treatments would occur in New Mexico (32%), 

Idaho (19%), Wyoming (12%) and Nevada (8%). 

Except for New Mexico, these states have substantially 

lower per capita minority and Native American

populations than the entire western U.S. (see Table 3-

15). In addition, the percentage of the population under 

18 in these states is less than or similar to the percentage 

in the remainder of the West. Thus, disproportionate 

impacts to minority populations and children from 

vegetation treatments should not occur under this 

alternative. Public lands provide lifeway values for 

Indian tribes, and there is concern among Indian tribes 

and the public that the BLM vegetation treatments could 

adversely impact native plants used for cultural and 

traditional purposes if projects are not carefully planned 

and implemented. The BLM would consult with Indian

tribes before implementing treatments that could impact

vegetation of importance to Indian tribes to reduce these 

potential impacts. 

Based on the assumption that the average costs to treat 

vegetation using ground-based and aerial methods are 

$35 per acre and $125 per acre, respectively, and using

information on the cost of herbicides in Table 3-23 and 

assumptions from the BLM on the percentage of acres 

to be treated using ground- and aerial-based methods for 

each herbicide, approximately $30.1 million would be

spent on herbicide applications; $24 million would be 

spent on ground-based applications, and $6.1 million 

would be spent on aerial applications under the No 

Action Alternative. The cost per acre treated would be

approximately $98.70 per acre. 

These expenditures would provide employment and 

income benefits. Regardless of the local economic 

situation, the nature of treatments indicates employment

and related income effects would be short-term in 

nature and geographically dispersed, benefiting certain 

communities throughout the 17-state study area. In

general, it is expected that communities located in areas 

where the most acres were treated would receive the

greatest employment and economic benefits. 

Neither the suppression cost savings nor the reduction 

in property losses can be quantified at the 17-state 

regional scale under this alternative. However, benefits 

would be most likely to occur in ecoregions/states with 

the greatest number of acres treated (Idaho, Wyoming,

Nevada, and New Mexico; Temperate Desert

Ecoregion), or where the risk of fire starting by

lightning or human causes is greatest (California in 

2005; USDA Forest Service 2000b, USDI BLM 2006c). 

Commercial activities that occur on public lands could

be affected by vegetation treatments. As noted earlier, 

most treatments would occur in New Mexico, Idaho,

Wyoming, and Nevada. Only about 1% of timber sales 

occur in these states. Effects on timber sales from

vegetation treatments would be greatest in Oregon, 

where over 95% of timber sales occur. Based on grazing 

leases, licenses, and permit fees, over 55% of these

expenditures occur in these states, while 44% of active 

animal unit months occur in these states (see Table 3-6; 

USDI BLM 2006c). Oregon and Utah also have large 

BLM Vegetation Treatments Using Herbicides 4-171 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

populations of livestock on public lands. Thus, 

vegetation treatment activities could affect grazing 

activities and income in these states. Effects on

recreation expenditures would likely be modest, as only 

27% of recreation expenditures would occur in these 

four states. Treatments in California, Oregon, and Utah

would be more likely to affect recreation expenditures, 

as nearly 56% of annual recreation expenditures occur 

in these states.

Herbicide treatment effects on private property from

drift and accidental applications would be less under 

this alternative than under the other treatment

alternatives. Over the long term, a reduction in 

hazardous fuels on public lands would reduce the

likelihood of wildfires migrating from public lands to

nearby private property and impacting the WUI. 

Herbicide treatments would also reduce the risks of

noxious weeds, including poisonous weeds, spreading

onto neighboring parcels. These benefits would be less 

under this alternative than under the other treatment 

alternatives. 

Alternative B – Expand Herbicide Use and 

Allow for Use of New Herbicides in 17 Western 

States (Preferred Alternative) 

The Preferred Alternative would result in herbicide

treatments on approximately 932,000 acres annually in

17 western states. In addition to the 14 previouslyapproved herbicides, the BLM would be able to use the 

four new herbicides evaluated in this PEIS. 

As future treatment levels would be 3 times that of 

current levels, there would likely be a minor change in 

existing patterns and trends in population and 

demographic conditions in the western states. While 

there would be localized increases in employment

generated by the increase in BLM acreage treated with

herbicides under the Preferred Alternative, the jobs

would generally be short-term, temporary positions or 

contracted work, which would not be sufficient to 

encourage measurable in-migration of workers and their 

families. 

Under the Preferred Alternative, most treatments would

occur in Idaho (28%), Nevada (22%), Wyoming (16%), 

and New Mexico (10%). Except for New Mexico, these

states have substantially lower per capita minority and

Native American populations than the entire western 

U.S. (see Table 3-15). In addition, the percentage of the 

population under 18 in these states is less than or similar 

to the percentage in the remainder of the western U.S. 

Thus, disproportionate impacts to minority populations 

and children from vegetation treatments should not

occur under this alternative. The potential for impacts to 

plants that provide traditional lifeway values would be 

greatest under this alternative. Some treatments could

occur in Alaska, Nebraska, and Texas under this 

alternative. 

Anticipated adjustments to herbicide usage would not

substantively change the expenditure per acre for 

chemicals, as nearly 90% of the herbicide usage would

simply be a proportional increase in the pattern of active 

ingredients used in recent years. Of the four new 

herbicides, imazapic would be the most heavily used; it 

falls in the lower price range for chemicals. Detailed

information is not available on types of herbicides to be 

used in each of the proposed treatment projects. 

However, based on information obtained from field 

offices in 2002, it is assumed that approximately 45% of

the acreage would be treated from the air and 55% from

the ground. Under this scenario, it is expected that 

existing social and economic trends would continue,

with a substantial increase in economic activity 

generated. 

Based on the assumptions given under the No Action

Alternative for costs to treat vegetation using herbicides, 

approximately $69.6 million would be spent on groundbased applications, and $19.5 million on aerial

applications, or $89.1 million for all applications under 

the Preferred Alternative. This figure is about 3 times 

the amount that would be spent under the No Action 

Alternative. However, the average cost per acre treated

would be $95.60 per acre, or 3% less per acre than 

under the No Action Alternative. 

Considering the scale of the increase in the herbicide

treatment program under the Preferred Alternative, it is 

expected that the economic benefits would likely spread

to more local communities than under the other 

treatment alternatives, and that some individual

communities would experience substantial gains. Which 

communities would be affected, and to what degree, 

cannot be determined at this time. 

Neither the suppression cost savings nor the reduction 

in property losses can be quantified at the 17-state 

regional scale under this alternative. However, benefits 

would be greatest under this alternative because of the 

acreage treated. As with the other treatment alternatives,

benefits would be most likely to occur in those 

ecoregions/states with the greatest number of acres

treated (Idaho, Wyoming, Nevada, and New Mexico; 

Temperate Desert Ecoregion), or where the risk of fire

starting by lightning or human causes is greatest

BLM Vegetation Treatments Using Herbicides 4-172 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

(California; USDA Forest Service 2000b, USDI BLM

2006c). 

Commercial activities that occur on public lands could

be affected by vegetation treatments. As with the other

treatment alternatives, effects on commercial activities 

should be greatest in those states where most acres 

would be treated (Idaho, Wyoming, Nevada, and New 

Mexico), where most timber sales occur (Oregon), 

where most grazing occurs (Wyoming, Montana, Idaho,

Utah, and Oregon), and where the greatest recreation

expenditures occur (California, Oregon, and Utah). 

Herbicide treatment effects on private property from

drift and accidental applications would be greatest under 

this alternative. Some herbicide could drift onto private

property, especially during aerial treatments. Under 

such a scenario, crops could be lost. Alternatively, 

rangeland weeds could be killed, resulting in benefits to 

private property. Losses and gains would likely be 

minor and short term in nature. 

Over the long term, a reduction in hazardous fuels on

public lands would reduce the likelihood of wildfires 

migrating from public lands to nearby private property 

and impacting the WUI. Herbicide treatments would

also reduce the risks of noxious weeds, including

poisonous weeds, spreading onto neighboring parcels. 

These benefits would be greatest under this alternative. 

Alternative C – No Use of Herbicides 

Under Alternative C, the BLM would not be able to use

herbicides to treat vegetation. Positive social benefits 

could be less than under the other alternatives because

wildfire risk reduction in WUI areas would not be as

effective and the economic benefits to ranching 

communities would not be as great as under the other 

alternatives. It is likely that fire suppression costs and

fire damage losses would be greater under Alternative C 

than under the other alternatives. In addition, benefits to

rangelands could be less under this alternative, as 

certain invasive species are effectively controlled only 

by herbicides, and in some situations other methods are 

impractical due to cost, time, or public concerns. 

Under this alternative, invasive plant populations would 

likely continue to spread, possibly at increasing rates, 

without use of herbicides. Related declines in rangeland 

capacity, combined with the potential for the spread of

invasive plants from public lands to private ranch lands 

in areas where other treatment methods are not effective 

or practical, would adversely affect ranching profits and

would thus be detrimental to local economies in rural

areas of the West. 

Generally, non-herbicide vegetation treatment methods 

tend to be more labor intensive and thus more expensive 

on a per acre basis in situations where herbicides are 

preferred, which translates into less effective control of 

undesirable vegetation. As a result, more workers could 

be hired in some places under this alternative, although 

many of the additional jobs would likely be low paying, 

unskilled labor positions. 

Alternative D – No Aerial Applications 

Alternative D would be the same as the Preferred

Alternative as far as which herbicides could be used, but

the limitation on aerial application would preclude 

treatments in some areas that would not be suitable for 

ground application due to access difficulties or the scale

of vegetation problems. Because of this limitation, and

perhaps also because of the often higher cost of ground 

application, fewer acres—530,000—would be treated 

under Alternative D than under the Preferred

Alternative. More acres would be treated under 

Alternative D than under the No Action Alternative. 

Consequently, the types of social and economic effects 

of Alternative D would be similar to the effects 

described for the No Action and Preferred alternatives, 

but would fall between them in magnitude. 

As under the other herbicide treatment alternatives, 

most treatments would occur in Idaho, Wyoming, 

Montana, and Nevada. These states have lower per 

capita minority and Native American populations than

the remainder of the western U.S., and the percentage of 

the population under 18 in these states is less than or 

similar to the percentage in the remainder of the western

U.S. (see Table 3-15). Thus, disproportionate impacts to

minority populations and children from vegetation 

treatments should not occur under this alternative. 

Based on the assumptions given under the No Action

Alternative for costs to treat vegetation using herbicides, 

approximately $76.7 million would be spent on groundbased applications under Alternative D, or about 14%

less than would be spent under the Preferred

Alternative, although 43% fewer acres would be treated

under Alternative D. The average cost per acre treated 

would be $144.72, or nearly 51% and 47% more than

for treatments under the Preferred and No Action 

alternatives, respectively. 

It is expected that the economic benefits to local 

communities would be less than under the Preferred 

BLM Vegetation Treatments Using Herbicides 4-173 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Alternative, but greater than under the No Action

Alternative. Which communities would be affected, and

to what degree, cannot be determined at this time. 

Herbicide treatment effects on private property from

drift and accidental applications would be intermediate

between the No Action and Preferred alternatives. Over 

the long term, a reduction in hazardous fuels on public

lands would reduce the likelihood of wildfires migrating

from public lands to nearby private property and 

impacting the WUI. Herbicide treatments would also 

reduce the risks of noxious weeds, including poisonous 

weeds, spreading onto neighboring parcels. These 

benefits would be intermediate to those of the Preferred

and No Action alternatives, and similar to Alternative E. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Active Ingredients 

Approximately 466,000 acres would be treated under 

Alternative E, which is approximately 11% less than the 

acreage that would be treated under Alternative D, and

about half of the acreage that would be treated under the 

Preferred Alternative. The acreage treated would be one 

and one-half times the acreage that would be treated 

under the No Action Alternative. 

Alternative E would have somewhat more positive 

social effects than other alternatives in that it would 

clearly establish protection for Native American and

Alaska Native resources. Economically, it could result

in prohibitions or restrictions on certain commercial and

recreational activities that support and sustain some

rural communities. Without more specific information 

on such restrictions, however, it is not possible to 

accurately predict how significant the effects would be.

In most other respects, the social and economic effects 

of Alternative E would be similar to those associated

with other alternatives and proportional to the acreage 

treated. 

The profile of selected active ingredients under 

Alternative E would be very similar to the profile for the

No Action Alternative, and would only notably differ 

from the Preferred Alternative in that there would be 

more use of glyphosate and no use of imazapic (Table

2-5). Because these are both lower priced active 

ingredients, the adjustment would not significantly

affect economic activity. 

Based on the assumptions given under the No Action

Alternative for costs to treat vegetation using herbicides, 

approximately $57.7 million would be spent on groundbased applications, and $2.3 million would be spent on 

aerial applications (assuming that the percentage of 

acres treated using aerial methods for each herbicide

would only be one-third the percentage of acres treated 

using aerial methods for each herbicide under the

Preferred Alternative). Thus, although half as many 

acres would be treated under this alternative compared

to the Preferred Alternative, costs would be reduced by

only one-third. The cost per acre treated would be about

$128.75 under this alternative, or 11% less than under 

Alternative D, but 35% and 30% greater than the cost 

per acre treated under the Preferred and No Action 

alternatives, respectively. 

Mitigation for Herbicide Treatment 

Impacts 

No mitigation measures are proposed for social and

economic resources. 

Human Health and Safety 

The use of herbicides under a variety of application

methods, as proposed in this PEIS, involves potential

risk or the perception of risk to workers and members of

the public living or engaging in activities in or near 

herbicide treatment areas. Therefore, as part of the 

PEIS, an HHRA has been conducted to evaluate

potential human health risks that may result from

herbicide exposure both during and after treatment of 

public lands. The HHRA has been conducted to be

scientifically defensible, to be consistent with currently

available guidance where appropriate, and to meet the

needs of the BLM vegetation treatment program.

Risk to two types of human “receptors” was evaluated:

occupational receptors and public receptors. Receptors 

are representative population groups that could have

specific exposures to the herbicides. Occupational 

receptors included those workers that mix, load, and 

apply herbicides and operate transport vehicles, 

recognizing that in some cases an occupational receptor 

may perform multiple tasks, increasing his or her 

exposure. Public receptors included those members of

the public most likely to come into contact with applied 

herbicides. The public receptors included adult 

hiker/hunters and anglers, and adult and child berry 

pickers, swimmers, Native Americans, and residents. 

Receptors were evaluated assuming both accidental

(e.g., direct spray or spill onto skin) and routine 

exposure scenarios (e.g., ingestion of berries that have 

been recently sprayed). 

BLM Vegetation Treatments Using Herbicides 4-174 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Scoping Comments and Other Issues 

Evaluated in the Assessment 

A large number of respondents during public scoping 

were concerned about the risks to human health from 

herbicide treatments. Respondents suggested that at-risk

groups like infants, the elderly, sick people, and people

with sensitivities to chemicals be specifically addressed. 

Numerous respondents urged the BLM to describe all

potential toxicological hazards of herbicide chemicals,

including their ability to disrupt hormone systems and

immune systems. Establishing a goal of using the 

minimum effective dosage and developing protocols for 

achieving this was encouraged. There was also concern 

about the effects of herbicides on basket plants and the 

people who collect them, in particular Native 

Americans. Some respondents also felt that the

uncertainties regarding the environmental effects of

herbicides and inert ingredients should be disclosed. 

According to some respondents, Oust® (herbicide

formulated with sulfometuron methyl) should be 

considered for evaluation even though it was evaluated 

previously in the 1991 13-State Vegetation EIS (USDI 

BLM 1991a). One respondent noted that if there are 

insufficient toxicological data to be found for a specific 

herbicide, then that herbicide should not be used. 

Standard Operating Procedures 

Standard operating procedures designed to reduce 

potential unintended impacts to human health from the 

application of herbicides in the BLM vegetation

management program, and considered when evaluating 

impacts, are listed in Table 2-8. These SOPs include the

following: 

• Establish a buffer between treatment areas and 

human residences based on guidance given in 

the HHRA, with a minimum buffer of 1⁄4 mile

for aerial applications and 100 feet for ground

applications, unless a written waiver is granted. 

• Use protective equipment as directed by the

herbicide label. 

• Post treated areas with appropriate signs at

common public access areas.

• Observe restricted entry intervals specified by 

the herbicide label. 

• Provide public notification in newspapers or

other media where the potential exists for

public exposure. 

• Have a copy of Material Safety Data Sheets at 

work sites. 

• Notify local emergency personnel of proposed 

treatments. 

• Contain and clean up spills and request help as 

needed. 

• Secure containers during transport. 

• Follow label directions for use and storage. 

• Dispose of unwanted herbicides promptly and 

correctly. 

The results from the HHRA will help inform BLM field

offices about the proper application of herbicides to

ensure that impacts to humans are minimized to the 

extent practical. 

Human Health Risk Assessment 

Methodology 

The BLM conducted an HHRA to evaluate potential

risks to humans from exposure to the following six 

active ingredients, four of which are proposed for use 

on public lands: dicamba, diflufenzopyr, diquat, 

fluridone, imazapic, and sulfometuron methyl. The four 

active ingredients not currently used on public lands are 

diflufenzopyr, diquat, fluridone, and imazapic. 

Sulfometuron methyl (Oust®) and dicamba were

evaluated for risks to humans in earlier EISs and are 

currently used by the BLM, but were reevaluated for 

this PEIS. Oust® has been found to impact non-target 

vegetation when carried on soil to untreated areas; these 

effects were not evaluated in the earlier vegetation 

treatment EISs. Dicamba is used in formulation with 

diflufenzopyr (as Overdrive®), and was reassessed as

part of the evaluation of the formulation. These active 

ingredients may be formulated into herbicides under a 

variety of trade names and manufacturers. Therefore,

specific trade names and manufacturers are not

discussed in this report. 

The remaining 18 active ingredients that are available

for use by the BLM were evaluated in other HHRAs. 

The BLM relied on HHRAs prepared in recent years by 

the Forest Service to evaluate the risks to human health

associated with nine active ingredients (2,4-D,

chlorsulfuron, clopyralid, glyphosate, hexazinone,

imazapyr, metsulfuron methyl, picloram, and triclopyr).

For the remaining nine active ingredients (2,4-DP, 

asulam, atrazine, bromacil, diuron, fosamine, 

mefluidide, simazine, and tebuthiuron), the BLM relied 

BLM Vegetation Treatments Using Herbicides 4-175 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

on information provided in earlier BLM vegetation

treatment EISs (USDI BLM 1988a, 1989a, 1991a). 

As this PEIS relies upon the HHRA results developed 

by both BLM and Forest Service, the following sections 

discuss the risk assessment methods used by the BLM 

in the current assessment, the risk assessment methods 

used by Forest Service, and the methods used by BLM

in the earlier EIS HHRAs. This discussion is followed

by a discussion of the uncertainties in the risk

assessment process. 

BLM Human Health Risk Assessment Methodology

The BLM HHRA follows the four-step risk assessment

model identified by the National Academy of Sciences 

(NAS 1983). These steps are: 1) hazard identification,

2) dose response assessment, 3) exposure assessment, 

and 4) risk characterization. The outcome of each of

these steps is discussed below. More detailed 

information on the methodology used to evaluate risks 

is in Appendix B and in the Vegetation Treatments 

Programmatic EIS Human Health Risk Assessment

Final Report (ENSR 2005l). 

Hazard Identification

The hazard identification section provides information

on the herbicide active ingredient characteristics and 

usage, and toxicity profiles. Much of the toxicity

information discussed in this section is from USEPA 

reports, such as the Pesticide Fact Sheets or HHRAs

conducted by the USEPA OPP Health Effects Division

to evaluate use of the pesticides on specific crops. In

addition, a literature search was conducted to ensure 

that relevant available information was used in these 

toxicity profiles. The databases searched include the

National Library of Medicine’s Hazardous Substances 

Data Bank and Toxline. The USEPA receives many

unpublished toxicity data sets that are referenced in

USEPA reports using Master Record Identification 

(MRID) numbers. The HHRA references USEPA

reports for the MRID information.

Both acute (short term) and chronic (longer term) 

toxicity information is discussed for the active

ingredient. The USEPA has developed toxicity

categories for pesticides based on acute toxicity animal

tests conducted in support of registration of the 

pesticides (USEPA 2003f). Acute toxicity studies are 

used to determine a number of toxicity endpoints based 

on short-term exposure to a substance. The toxicity

endpoints considered are oral, inhalation, and dermal

acute toxicity; eye irritation; skin irritation; and dermal

sensitization. An important endpoint in acute testing is

the toxicity reference level known as the median lethal

dose (LD50), which is the dose, usually administered

orally, that kills 50% of the test animals. The lower the

LD50 is, the greater the toxicity of the chemical. For the 

different toxicity endpoints, the USEPA defines four 

toxicity categories (Lists; I through IV), with higher 

toxicity categories representing lower herbicide acute 

toxicity. In longer-term toxicity studies (chronic or 

subchronic), the endpoints for evaluation are the dose at

which no adverse effects were seen (NOAEL), and the

lowest observed adverse effect level (LOAEL), which is 

the lowest level at which adverse effects are seen in 

chronic studies. 

In addition to their active ingredients, most herbicides 

contain inert ingredients (i.e., those substances included 

in the formulation that are not the active ingredients) 

that have various functions such as diluents, binders, 

dispersants, carriers, stabilizers, neutralizers,

antifoamers, and buffers. 

The USEPA categorizes inert ingredients into four lists

(54 FR 48314): 

• List 1 – Inert ingredients of toxicological 

concern. Any product containing a List 1

ingredient must include the label statement,

“this product contains the toxic inert ingredient 

(name of inert).”

• List 2 – Inerts of unknown toxicity/high 

priority for testing inerts. 

• List 3 – Inerts of unknown toxicity. Inert

ingredients on this list have not yet been

determined to be of known potential 

toxicological concern nor have they been 

determined to be of minimal concern. These 

substances will continue to be evaluated to

determine if they merit reclassification to List 

1, 2, or 4. 

• List 4 – Inerts of minimal concern. List 4 is 

subdivided into List 4A (minimal risk inert 

ingredients) and List 4B (inerts that have

sufficient data to substantiate that they can be

used safely in pesticide products). 

BLM scientists received clearance from the USEPA to

review Confidential Business Information (CBI) on 

inert compounds identified in products containing the

six active ingredients evaluated in this risk assessment. 

The information received listed the inert ingredients, as 

well as their chemical abstract number, supplier,

BLM Vegetation Treatments Using Herbicides 4-176 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

USEPA registration number, percentage of the 

formulation, and purpose of the formulation. The BLM

reviewed one formulation of diflufenzopyr and

dicamba; two formulations of diquat; four formulations 

of fluridone; two formulations of imazapic; and one 

formulation of sulfometuron methyl. Because it is 

confidential, this information, including the name of the

ingredients, may not be disclosed. 

The USEPA has a listing of regulated inert ingredients

at http://www.epa.gov/opprd001/inerts/index.html. This 

listing divides inert ingredients into four lists. The 

number of inert ingredients found in the six herbicides 

evaluated in the HHRAs for each category is shown

below (seven inerts were not found on the USEPA

lists): 

List 1 - Inert ingredients of toxicological concern: 

None. 

List 2 - Potentially toxic inert ingredients: None. 

List 3 - Inerts of unknown toxicity: 5. 

List 4A - Inerts of minimal toxicity: 9. 

List 4B - Inerts that have sufficient data to

substantiate that they can be used safely in 

pesticide products: 18. 

Based on this information, the majority of the inerts are 

of minimal risk. A few are in the category of unknown

toxicity. 

Dose-Response Assessment 

The purpose of the dose-response assessment is to 

identify the types of adverse health effects an herbicide 

may potentially cause and to define the relationship 

between the dose of an herbicide and the likelihood or 

magnitude of an adverse effect (response). The doseresponse assessment identifies quantitative doseresponse values that are used in risk calculations to 

derive risk estimates. The dose-response values used in

the HHRA were developed by the USEPA. None of the

six herbicides evaluated in the BLM HHRA are 

designated as potential carcinogens by the USEPA;

therefore, this toxicity assessment focuses on noncarcinogenic effects (i.e., potential toxic effects other 

than cancer). Non-carcinogenic effects are evaluated 

differently depending on whether the exposure is dietary 

or non-dietary.

For dietary exposures to non-carcinogenic chemicals, 

toxicity is represented by a population adjusted dose 

(PAD), which may be calculated for acute effects or

chronic effects. A PAD is an acute or chronic RfD 

divided by the Food Quality Protection Act (FQPA) 

Safety Factor, which accounts for cases where infants 

and children may have extra sensitivity to the pesticide

(USEPA 2000c). Reference doses are derived by 

identifying an NOAEL, which is obtained from the 

acute or chronic toxicity studies, and dividing the

NOAEL by the appropriate uncertainty factors (UFs). 

Typically, a 10-fold UF is applied to account for 

variation within the human population (i.e., to account

for individuals that may be more sensitive to the effects;

intraspecies), and an additional 10-fold factor is applied 

to account for the differences between humans and

animals (interspecies; USEPA 2000c). The FQPA 

Safety Factor is applied to the PAD in addition to the

uncertainty factors used to derive the RfD. 

A margin of exposure (MOE) approach is used to

evaluate potential non-dietary exposures to herbicides.

For evaluating non-cancer effects for non-dietary

exposures, toxicity is represented by the NOAEL. The 

NOAELs are identified for a variety of exposure 

durations and exposure routes (short-, intermediate-, 

and long-term exposure durations via oral, dermal, and 

inhalation exposure routes). The NOAELs representing 

non-dietary exposures were used to evaluate the

occupational receptors and the public receptors for the

following scenarios: dermal contact with spray, dermal

contact with foliage, dermal contact with water while

swimming, and incidental ingestion of water while 

swimming. The NOAEL divided by the intake (see the 

Exposure Assessment section below for a description of 

how intakes are derived) results in the MOE (USEPA 

2000c). Unless specified otherwise, the target MOE is 

100, which accounts for uncertainties in the NOAEL. 

MOEs greater than the target MOE indicate no 

significant risk. 

Exposure Assessment 

The purpose of the exposure assessment is to predict

the magnitude and frequency of potential human 

exposure to the herbicides under consideration. The

BLM takes care to prevent exposures to applied 

pesticides both through worker training programs and 

by posting areas that have just been sprayed with 

information on when reentry into these areas is

appropriate. However, to be conservative, the HHRA 

has evaluated both routine use and accidental exposure

scenarios. In addition, exposures were evaluated for

two application scenarios: applications using the

BLM Vegetation Treatments Using Herbicides 4-177 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

maximum application rate designated by the herbicide

label, and applications using a typical application rate

that was defined by BLM for this program. 

To estimate the potential risk to human health that may 

be posed by the planned herbicide use, it was first

necessary to estimate the potential exposure dose of 

each herbicide for each receptor via each applicable

exposure route. Exposure dose equations combine the

estimates of herbicide concentration in the

environmental medium of interest, with assumptions

(exposure parameters) regarding the type and

magnitude of each receptor’s potential exposure to

provide a numerical estimate of the exposure dose.

The exposure dose is defined as the amount of

herbicide taken into the receptor, expressed in units of 

milligrams of herbicide per kilogram of body weight

per day (mg/kg-day). The exposure doses were 

combined with the dose-response values (PADs or 

NOAELs) to estimate potential risks and hazards for

each receptor.

Various guidelines and databases, such as the USEPA’s 

Exposure Factors Handbook (USEPA 1997) and the 

Framework for Assessing Non-Occupational, NonDietary (Residential) Exposure to Pesticides (USEPA

1998c), were used to develop the exposure parameters.

For each exposure scenario, the exposure parameters

were used to calculate an exposure factor (EF), which 

was then used in the risk calculations. The use of the EF 

combines all the exposure parameters into one value in

order to simplify the risk calculations. 

Occupational Exposure Scenarios. Both routine-use

and accidental exposure scenarios were included in the 

occupational evaluation. For the routine-use exposure 

scenario, the exposure assumptions were derived using 

information from the BLM concerning proposed use of 

the herbicides, and unit exposure (UE) information from 

the Pesticide Handlers Exposure Database (PHED), 

which is a generic database containing empirical dermal 

and inhalation exposure data for workers mixing, 

loading, or applying pesticides (USEPA 1998d). To add

consistency to the risk assessment process, the USEPA,

in conjunction with the PHED task force, has evaluated 

all data within the system and developed a series of 

surrogate standard UE values for various exposure 

scenarios. The majority of the UE values have been 

taken from these surrogate values. In addition to these 

values, the USEPA recommended UEs separately for 

aquatic applications of diquat and fluridone. Generally,

UEs are expressed in units of milligrams per pound of 

active ingredient, and equate the milligrams of active

ingredient absorbed by an occupational receptor to the

pounds of active ingredient handled in a given day or 

exposure scenario. 

For aerial applications, occupational receptors that may 

come into routine contact with herbicides include pilots 

and mixer/loaders. For ground applications by 

backpack, the occupational receptor is assumed to be an

applicator/mixer/loader. For the remaining application 

methods (horseback, and spot and boom/broadcast

methods for ATV, truck mount, and boat applications), 

applicators, mixer/loaders, and applicator/mixer/loaders

were evaluated. In addition, for each occupational

receptor, dermal and inhalation exposure pathways were

evaluated. For the routine exposures, the exposure dose 

was calculated using the herbicide application rate and 

the acres treated per day. Details on how this was done 

are presented in the Vegetation Treatments 

Programmatic EIS Human Health Risk Assessment

Final Report, found on the CD located in the back of 

Volume I of the PEIS (ENSR 2005l). 

Accidental exposures for occupational receptors could 

occur via spills or direct spray onto a worker. To

calculate exposures from direct spills, it is necessary to 

know the concentration of active ingredient in the 

formulation that is spilled onto the worker. These

concentrations were calculated from the information 

provided on the herbicide labels. As a worst-case 

scenario for an accidental exposure, a direct spill event

on an occupational receptor was evaluated. This HHRA 

used the same spill scenario evaluated by the BLM in 

the Final EIS Vegetation Treatment on BLM Lands in

Thirteen Western States (USDI BLM 1991a). The spill

scenario assumes that 0.5 L (1⁄2 quart) of the formulation 

is spilled on a worker receptor. It is assumed that 80%

of the spill lands on clothing and 20% lands on bare 

skin. The penetration rate through clothing is assumed

to be 30%. While some of the herbicide labels require 

the use of gloves while handling the herbicide, others do

not. Therefore, this scenario assumes that gloves are not 

worn. 

Public Use Exposure Scenarios. The HHRA evaluated 

the potential risk to public receptors using public lands 

treated with herbicides. This was done by developing 

exposure scenarios that combine potential receptors and

exposure pathways to identify potential exposures to the 

herbicide active ingredient addressed in this PEIS. Two

types of public use exposure scenarios are addressed: 

• Potential exposure by public receptors during 

routine use of public lands to herbicide active

ingredient(s) that may have drifted outside of 

the area of application. 

BLM Vegetation Treatments Using Herbicides 4-178 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

• Accidental scenarios where public receptors 

may prematurely enter a sprayed area (a reentry 

scenario), be sprayed directly, or may contact

water bodies that have accidentally been 

sprayed directly or into which an herbicide 

active ingredient has accidentally been spilled. 

Although all of these public scenarios are expected to 

occur rarely, they are nonetheless used as the basis for 

evaluating potential public health risks associated with 

herbicide use in the BLM vegetation treatment program. 

Based on consideration of potential public uses of BLM

lands, and consistent with the 1991 13-State EIS (USDI 

BLM 1991a), receptors evaluated in this HHRA include

1) hiker/hunter; 2) berry picker - child and adult; 3)

angler; 4) swimmer - child and adult; 5) nearby resident

- child and adult; and 6) Native American - child and 

adult. 

Although there are many different exposure scenarios 

and receptors that could be evaluated, the selected 

scenarios cover a range of potential exposures that

could occur under worst-case conditions on public

lands. It is assumed that public receptors could be 

exposed through one or more of the following exposure 

pathways: 1) dermal contact with spray, 2) dermal

contact with foliage, 3) dermal contact with water while

swimming, 4) ingestion of drinking water or incidental

ingestion of water while swimming, 5) ingestion of 

berries, and 6) ingestion of fish. 

Although all public receptor exposures to herbicides 

used on pubic lands are considered to be accidental, 

public receptor exposures were evaluated under two

scenarios. Routine-use exposures are assumed to occur 

when public receptors come into contact with 

environmental media that have been impacted by spray 

drift. Accidental exposures are assumed to occur when 

public receptors come into contact with environmental

media that have been subject to direct spray or spills. 

Each of these scenarios is discussed below. 

Public receptors could be exposed to herbicides via offsite drift following routine aerial application. AgDRIFT, 

a computer model that is a product of the Cooperative 

Research and Development Agreement between the

USEPA’s Office of Research and Development and the 

SDTF (a coalition of pesticide registrants), was utilized 

in the HHRA to evaluate the off-site deposition of 

herbicides (SDTF 2002). See Appendix C of the 

Vegetation Treatments Programmatic EIS Human

Health Risk Assessment Final Report (ENSR 2005l) for 

a complete description of AgDRIFT modeling methods. 

In addition, public receptors could be exposed to 

herbicides via surface runoff. The GLEAMS model, a 

modified version of the Chemical Runoff Erosion

Assessment Management System (CREAMS) model

that was originally developed to evaluate non-point

source pollution from agricultural field-size areas, was 

used to simulate surface runoff of the three terrestrial

herbicides considered in the HHRA. See Appendix D of 

the Vegetation Treatments Programmatic EIS Human

Health Risk Assessment Final Report (ENSR 2005l) for 

a complete description of GLEAMS modeling methods. 

In addition to exposures due to inadvertent spray drift,

this HHRA also evaluates potential acute accidental 

exposures by public receptors to the herbicide active

ingredient. Accidental exposure could occur through 

direct spray and spills. The same types of receptors 

introduced above are also evaluated for the accidental 

scenarios. However, because direct spray and spills are 

localized, exposures to multiple media are not assumed

in these scenarios. It is assumed that each of the 

herbicide active ingredients could be directly sprayed

onto humans, foliage, and/or berries, and each of the 

herbicide active ingredients could be directly sprayed or

spilled into a water body. However, for the aquatic 

herbicide active ingredients (fluridone and diquat), the

direct spray into a water body pathway is a reentry 

scenario. 

Risk Characterization

The purpose of the risk characterization is to provide 

estimates of the potential risk to human health from 

exposure to herbicides. The results of the exposure 

assessment are combined with the results of the doseresponse assessment to derive quantitative estimates of

risk. For the noncarcinogenic active ingredients 

evaluated in this HHRA, risk is described simply by the 

comparison of the exposure doses to the appropriate 

dose-response values. 

The USEPA risk assessment guidance for pesticides 

provides different non-cancer methods for evaluating 

food and non-food exposures (USEPA 2000c). For food 

exposure, a percent PAD method is used, and for nonfood exposure, a MOE method is used, as described in 

the Dose-Response Assessment section above. 

In assessing risks to humans, it is important to evaluate

the cumulative or aggregate risk from all potential

exposure pathways for each receptor. For the public

receptors, both dietary and non-dietary pathways have

been evaluated. To address this, the USEPA’s OPP has 

developed the aggregate risk index (ARI) approach, 

BLM Vegetation Treatments Using Herbicides 4-179 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

which combines potential risks from various pathways 

expressed as MOEs (for non-dietary exposures) and 

%PADs (for dietary exposures; USEPA 1999d, 2001d).

It is important that only exposure pathways

encompassing similar exposure durations be combined

(i.e., acute exposures cannot be combined with chronic 

exposures). The ARI is an extension of the MOE 

concept. As with the MOE, potential risk increases as

the ARI decreases. The ARI is compared against a

target value of 1, which is the LOC set by the USEPA. 

Values > 1 do not exceed the USEPA’s LOC. The ARI 

method allows for direct comparisons between routes 

and between chemicals. It considers each route’s 

potency when route-specific NOAELs that may have

different UFs are used. ARIs were developed for each 

of the identified exposure scenarios. Cumulative 

accidental ARIs were not calculated, as it is assumed

that each receptor would be accidentally exposed via

only one potential exposure pathway. Details on the 

ARI method are provided in the Vegetation Treatments 

Programmatic EIS Human Health Risk Assessment

Final Report (ENSR 2005l). 

Forest Service Human Health Risk Assessment 

Methodology

The Forest Service risk assessment methodology was 

similar to that used by the BLM (see SERA [2001a] for

a complete description of the methodology). The steps 

involved in the Forest Service risk assessments included 

hazard identification, exposure assessment, dose

response assessment, and risk characterization. 

Hazard identification involved the review of 

toxicological data with a focus on the dose-response 

relationships to determine the effect levels (e.g., 

NOAEL, LOAEL) and assessment endpoints (e.g., 

acute toxicity, subchronic or chronic systemic toxic 

effects, reproductive and teratogenic effects) that are 

most relevant for the herbicide risk assessments.

Carcinogenic endpoints were evaluated for the Forest 

Service herbicides, as some contain potential

carcinogens in their formulations (i.e., 

hexachlorobenzene in clopyralid and picloram) and 2,4-

D was still being evaluated by the USEPA for 

carcinogenicity. 

In the exposure assessment phase, the Forest Service 

developed general and accidental exposure scenarios for 

workers expected to be handling the herbicides and for 

the general public who could be inadvertently exposed

to herbicides. General exposure for workers included 

exposure via directed foliar, broadcast ground, and 

broadcast aerial applications. Accidental exposure 

scenarios for workers included immersion or 

contaminated clothing and spills. Exposure scenarios for

the public included 1) direct spray, 2) dermal exposure 

from contaminated vegetation, 3) exposure to 

contaminated water, 4) acute exposure via spills, 5) 

consumption of contaminated fish, and 6) consumption

of contaminated vegetation. 

Dose response assessment described the degree or

severity of risk as a function of dose. The Forest Service

assessments used RfDs, derived by other government

agencies. The RfD is designed to be protective of 

chronic or lifetime exposure, and it is a very

conservative component of the Forest Service risk

characterization process because the duration of any 

plausible and substantial exposures is far less than a 

lifetime. 

The risk characterization process then compared the 

exposure assessment to the dose response assessment to 

determine an HQ for a specific exposure scenario. 

Hazard quotients were calculated by dividing the 

exposure level determined in the HHRA by the RfD. A 

higher HQ indicates that the exposure level exceeds the

RfD by a large amount. A quantitative risk assessment

for carcinogenicity was conducted for 

hexachlorobenzene (found in the herbicide formulations

of clopyralid and picloram), but not for any of the active

ingredients. 2,4-D was still being reviewed as a 

potential carcinogen at the time of assessment, and

therefore no carcinogenicity risk assessment was 

conducted. 

Previous BLM EISs Methodology and Toxicology 

Literature Review 

Asulam, atrazine, bromacil, diuron, fosamine, 

mefluidide, simazine, tebuthiuron, and 2,4-DP are 

herbicides currently available to the BLM for which

new HHRAs were not conducted either by the BLM or

the Forest Service. Human health risk assessments were

conducted for these herbicides by the BLM for earlier 

vegetation treatment EISs (USDI BLM 1988a, 1989a,

1991a). Since 1997, the BLM has not used asulam, 

atrazine, mefluidide, simazine, and 2,4-DP, and has 

used fosamine only sparingly (< 50 acres annually). It is 

unlikely that the BLM would use these herbicides in the

future, and they would not be available for use under the 

action alternatives (alternatives B though E). 

Literature reviews and evaluations were conducted for 

the period 1991 to 1998 to assess whether toxicity data 

for many of these herbicides (asulam, atrazine,

bromacil, diuron, mefluidide, simazine, tebuthiuron) 

BLM Vegetation Treatments Using Herbicides 4-180 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

that were reported since the 1991 13-State EIS would

indicate that a new HHRA should be conducted (i.e., if

the new toxicity data suggested greater risks to humans; 

McMullin and Thomas 2000). 2,4-DP, atrazine, 

bromacil, diuron, simazine, and tebuthiuron did not 

have recent toxicity data suggesting additional risks to 

humans; therefore, the human health risks of these 

herbicides are reported in this chapter using results from

the earlier EIS (also see Appendix B for more

information on the risks associated with these 

herbicides). The literature review suggested that 

revisions may be warranted for asulam (based on a 

lower RfD) and for mefluidide (based on development

of an RfD). 

The 1991 13-State EIS HHRA also evaluated

occupational and public receptors similar to the current

PEIS. Doses to receptors were estimated using 

assumptions about the characteristics of typical 

herbicide applications based on realistic as well as

worst-case values for these estimates. Doses to

receptors resulting from accidental exposures were 

evaluated. The risk assessment developed MOEs based 

on a ratio of the estimated herbicide intake to the

acceptable concentration represented by the RfD. In

addition, cancer slope factors were available for specific

herbicides, such as bromacil. For these herbicides, 

potential cancer risks were also estimated. The cancer 

slope factor for bromacil was available from the

USEPA at the time of the 1991 EIS. However, in the 

current review, the USEPA did not provide a cancer 

slope factor (USEPA 1994b); therefore, bromacil is

likely not carcinogenic. 

Exposure scenarios for the public included 1) dermal

exposure through spray drift, 2) dermal contact with 

vegetation, and 3) consumption of berries, water, fish, 

and game. It was assumed that occupational receptors 

could be exposed through inhalation and dermal 

contact. Occupational receptors included 1) aerial pilots;

2) mixer-loaders; 3) backpack applicators; 4) ground 

mechanical applicators; and 5) hand applicators. 

Routine and worst-case exposures were calculated using 

variable parameters such as application rate, size of 

treatment area, and drift conditions. The following 

accidental scenarios were also analyzed: 1) spills of

herbicide concentrate and mix on a person’s skin; 2)

direct spraying of a worker from a broken hose; 3)

direct spraying of a person from aerial application; 4) 

immediate reentry to a sprayed area; 5) consumption of

water from a pond that has been aerially sprayed, or that

has received a spill from an airplane or tank mix truck; 

and 6) consumption of berries that have been directly

sprayed. 

Uncertainty in the Risk Assessment 

Process 

The risk assessments conducted by the BLM and Forest 

Service incorporate various conservative assumptions to

compensate for uncertainties in the risk assessment

process. Within any of the steps of the human health 

risk evaluation process, assumptions must be made due 

to a lack of absolute scientific knowledge. Some of the 

assumptions are supported by considerable scientific 

evidence, while others have less support. Every 

assumption introduces some degree of uncertainty into 

the risk evaluation process. Regulatory risk evaluation 

methodology requires that conservative assumptions be 

made throughout the risk assessment process to ensure 

that public health is protected. This conservatism, both

in estimating exposures and in setting toxicity levels 

likely led to an exaggeration of the real risks of the

vegetation management program to err on the side of 

protecting human health. 

Impacts Common to All Herbicides

Each of the HHRAs developed risk estimates for 

occupational and public receptors for a variety of 

routine and accidental scenarios. The risk estimates for 

each herbicide, and for herbicides in general, are

presented below. 

Occupational Receptors 

Herbicide application methods may require the use of 

heavy machinery, which could involve potential health

and safety impacts to people working in the herbicide 

application programs (occupational receptors).

However, the main potential impact associated with the

use of herbicides is exposure to the chemicals 

(including the herbicide active ingredient(s) and other 

compounds added to the herbicide formula). These 

chemicals can all be toxic to human workers and

exposed members of the public to varying degrees (any 

chemical poses a health risk at a high enough dose). 

Most clinical reports of herbicide effects are of skin and 

eye irritation. 

Short-term effects of excessive exposure to herbicides 

include nausea, dizziness, or reversible abnormalities of

the nervous system. In extreme cases of prolonged, 

repeated, and excessive exposure (resulting from 

careless and/or negligent work habits), longer-term 

BLM Vegetation Treatments Using Herbicides 4-181 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

health problems can result, including: organ damage, 

immune system damage, permanent nervous system 

damage, production of inheritable mutations, damage to 

developing offspring, and reduction of reproductive 

success. It is important to note that the USEPA 

evaluates and registers herbicides according to a 

uniform, health-based standard to ensure a “reasonable

certainty of no harm” to consumers. The USEPA is

responsible for restricting a product’s use according to 

its potential impacts on human health and the 

environment. Much of that restriction is done through 

the product label, which states the precautions that must

be taken as well as how and where to apply a certain 

herbicide. 

Occupational exposure to herbicides varies with the 

method of application. The greatest risk occurs when

the worker must directly handle and/or mix chemicals. 

Spot and localized herbicide applications, including the

use of backpack sprayers and aerial mixers/loaders, 

require the most hands-on use of herbicides and, 

therefore, carry the greatest risk of exposure. Under all 

application methods, workers can be exposed to 

herbicides from accidental spills, splashing, leaking 

equipment, contact with spray, or by entering treated 

areas. Exposure can occur either through skin or 

through inhalation. Adherence to operational safety 

guidelines, use of protective clothing, equipment

checks, and personal hygiene can prevent incidents 

from occurring. The herbicide label and corresponding 

Material Safety Data Sheet (MSDS) detail these 

application requirements in addition to safety 

guidelines. 

Public Receptors 

Public receptors can be exposed by being accidentally

sprayed, by entering areas soon after treatment (e.g., 

eating berries or other foods, touching vegetation), 

drinking contaminated water, or accidentally coming

into contact with herbicides that have drifted downwind. 

Members of the general public, both visitors and 

residents, are less likely to be repeatedly exposed than 

vegetation management workers. 

Members of the public, both visitors and nearby 

residents, could potentially be exposed to herbicides 

from drift or accidental spraying if they were in the area

at the time of application. Since aerial and broadcast 

applications have a higher potential for drift, these 

application techniques might create a higher potential

for public exposure, particularly under certain weather 

conditions (e.g., high winds). 

Laboratory tests on animals have shown that most

herbicides are not carcinogenic, even at doses and 

repeated exposures well above those which could occur 

accidentally as part of vegetation management

activities. Furthermore, herbicides are designed to work

on plants, not animals, so that the toxic effects generally 

do not affect the central nervous system or other vital 

functions. 

Calculated dose-response values and exposure doses 

were combined to estimate potential risks (in terms of

ARIs for BLM HHRA herbicides and in terms of HQs 

for previously evaluated Forest Service herbicides) from 

each individual herbicide for each receptor. In addition,

the strength of these risks was evaluated by herbicide as 

well as by receptor, herbicide treatment method (e.g., 

aerial vs. terrestrial), and herbicide treatment alternative. 

Human Health Risks Associated with Herbicides

Evaluated in the BLM Human Health Risk

Assessment 

The HHRA listed the acute toxicity categories for each

herbicide developed by the USEPA, and conducted risk 

calculations to determine potential risks from routine

and accidental exposures for specific receptors. The 

USEPA has developed toxicity categories for pesticides 

based on acute toxicity animal tests conducted in 

support of registration of the pesticides (USEPA 

2003g). All six of the herbicides evaluated in the BLM

HHRA show slight to very slight acute toxicity to 

humans as designated by the USEPA in most

categories. Based on the USEPA categories, dicamba

may result in reversible eye irritation and severe skin

irritation. Diquat causes moderate acute dermal effects 

and reversible eye irritation, and fluridone causes 

reversible eye irritation. The USEPA has not developed

acute toxicity categories for sulfometuron methyl. 

None of the six herbicides are designated as potential

carcinogens by the USEPA. Therefore, the risk 

calculations discussed below consider non-cancer risk. 

Tables 4-27 and 4-28 present summaries of the level of 

risk each receptor (occupational and public) would face

during the application of a given herbicide, for both

maximum and typical application rate scenarios. ARIs 

are partitioned into no, low, moderate, and high levels 

of risk for ease of comparison (no risk is identified as an 

ARI greater than 1, low risk is between 1 and 0.1,

moderate risk is between 0.1 and 0.01, and high risk is 

less than 0.01). These designations are strictly for 

comparison purposes, and do not imply actual risks to

people. The Vegetation Treatments Programmatic EIS

BLM Vegetation Treatments Using Herbicides 4-182 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Human Health Risk Assessment Final Report (ENSR 

2005l) presents more detailed tables of ARIs for each

herbicide and receptor. 

Dicamba 

For the routine application scenarios at the typical and

maximum application rates, dicamba does not present

an unacceptable risk to occupational or public receptors.

However, dicamba applications do present low risk to 

occupational receptors during accidental scenarios. 

Diflufenzopyr 

For occupational receptors, routine use ARIs were 

calculated for inhalation exposures under both typical

and maximum application rate scenarios. No dermal

toxicity values are available for diflufenzopyr, which,

based on laboratory data, is not expected to be toxic 

through the dermal route. Routine use ARIs are greater

than 1 under both the typical and maximum 

application rate scenarios, indicating no exceedance of 

the USEPA’s LOC. Because the accidental

occupational scenarios all assume dermal exposure and 

diflufenzopyr does not have a short-term dermal 

NOAEL because it is not expected to be toxic through 

the dermal route, an accidental scenario ARI was not

calculated. 

For public receptors, routine use scenario ARIs are

greater than 1 under both the typical and maximum 

application rate scenarios for all public receptors,

indicating no LOC. Under the accidental scenario, it is

assumed that public receptors are exposed directly to 

maximum herbicide application rates via dermal 

contact, incidental ingestion of water while swimming, 

or dietary exposure pathways at the maximum 

application rate. All accidental scenario ARIs are 

greater than 1, indicating no LOC. 

These results indicate that exposures to diflufenzopyr 

are not expected to exceed the USEPA’s LOC for 

occupational or public receptors under the scenarios 

evaluated. 

Diquat 

At the typical application rate, diquat presents a low to

moderate risk to some occupational receptors (all aerial,

backpack, and horseback applicators), and a low risk to 

child residents. When diquat is applied at the maximum 

application rate, there is low to high risk to occupational

receptors (except boat applicators) and public receptors 

(except swimmers). Diquat poses a high risk to 

occupational receptors and a low to moderate risk to

public receptors under all accidental scenarios. 

Fluridone 

Fluridone does not pose a risk to occupational or public 

receptors when applied at the typical application rate. 

When fluridone is applied at the maximum application 

rate, there is low risk to aerial mixer/loaders. For 

accidental scenarios, fluridone poses a low to high risk 

to all occupational receptors, and a low risk to child and 

resident public receptors. 

Imazapic

Imazapic applications do not present risk to any 

receptors when applied in routine use situations at either 

the typical or maximum application rate. Accidental 

scenarios involving dermal contact with direct spray or 

vegetation or dietary exposure were not calculated

because imazapic has not been shown to have acute

dietary or dermal effects in hazard analyses conducted 

by the USEPA (ENSR 2005l). Accidental scenarios 

involving dermal contact with a sprayed water body or a 

water body into which herbicide is spilled do not result 

in risk to swimmers. 

Sulfometuron Methyl 

Sulfometuron methyl applications do not present risk to

any receptors when applied in routine use situations at

either the typical or maximum application rate. 

Accidental scenarios involving dermal contact with 

direct spray or vegetation or dietary exposure were not

calculated because sulfometuron methyl has not been 

shown to have acute dietary or dermal effects in hazard

analyses conducted by the USEPA (ENSR 2005l). 

Accidental scenarios involving dermal contact with a 

sprayed water body or a water body into which

sulfometuron methyl is spilled do not present a risk to 

swimmers. 

Human Health Risks Associated with Herbicides

Evaluated in the Forest Service Human Health Risk 

Assessment 

The BLM used the results of HHRAs prepared by the

Forest Service for nine active ingredients (2,4-D,

chlorsulfuron, clopyralid, glyphosate, hexazinone,

imazapyr, metsulfuron methyl, picloram, and triclopyr 

[SERA 2005b]). The Forest Service HHRAs presented 

the risk results as HQs. To create the summary tables 

presented here, (Tables 4-29 and 4-30), HQs were used

to designate a risk level as no, low, moderate or high, 

BLM Vegetation Treatments Using Herbicides 4-183 June 2007 

Final Programmatic EIS
ENVI

BLM 

Final Pr

for ease o

greater than 1

moderate ri

risk is an HQ greater than 

present su

public receptors, 

Service

2,4-D 

Workers involved in ground 

D m

exposure, or low to 

limit

maxi

directed grou

application, 

mode

low to 

for 1 hour, exposure to a spill on the 

(maxi

legs for 1 hour. The general public faces low to 

moderate ri

typical and 

consu

risk to the general public, an

populations. However, the 

that (when ap

should not be

associated wit

exposures could pose a high

for 

consu

period of 

occur. 

Chlor

For both workers and the general 

exposures to chlorsulfuron 

application rate would not pose a ri

Ground broadcast applications at the 

application rate would pose a low ri

From

are likel

chlorsulfuron.

avoided by

the handling o

Clopyralid 

There are no risks to public or occupati

associated 

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-184 June 2007 

ogrammatic EIS 

f comparison (no risk is identified as an HQ 

, low risk is an HQ between 1 and 10, 

sk is an HQ between 10 and 100, and high

100). Tables 4-29 and 4-30

mmaries of the risks to occupational and

respectively, associated with the Forest

-evaluated herbicides. 

or aerial application of 2,4-

ay face low risks based on central estimates of

moderate risks based on upper 

s of exposure (SERA 1998). At the typical and 

mum application rates, workers involved in

nd spray, broadcast ground spray, aerial

and aquatic application face low to 

rate risk from 2,4-D exposure. Workers also face

moderate risk from wearing contaminated gloves

hands for 1 hour 

mum rate only), and exposure to spill on the lower 

sk from most modeled scenarios at the 

maximum application rates. The 

mption of contaminated fish presents a moderate 

d a high risk to subsistence 

Forest Service HHRA asserts 

plied at the typical application rate) there

 unacceptable risks to the general public

h exposure to 2,4-D, but that accidental

er risk. The major concern

members of the general public involves the 

mption of contaminated vegetation (fruit) over a 

several months, a scenario that is not likely to

sulfuron 

public, most

at the typical or maximum 

sk (SERA 2004a). 

maximum

sk to workers. 

 a practical perspective, eye and/or skin irritation 

y to be the only overt effects of mishandling

 These effects can be minimized or 

 prudent industrial hygiene practices during

f the compound. 

onal receptors 

with most of the anticipated typical and

accidental exposure scenarios for clopyralid evaluated 

in the Forest Service risk assessment. Irritation and 

damage to the skin and eyes can result from direct 

exposure to relatively high levels of clopyralid; this is

likely to be the only overt effect as a consequence of 

mishandling clopyralid (SERA 2004b). Children face 

low risk from consumption of water contaminated by an

accidental spill. 

The human health risks of hexachlorobenzene and

pentachlorobenzene were also analyzed in the Forest

Service HHRA, as technical grade clopyralid may be

contaminated with these chemicals. Hexachlorobenzene 

was evaluated for potential carcinogenicity. Based on

the levels of contamination of technical grade clopyralid 

with hexachlorobenzene and pentachlorobenzene, and 

the relative potencies of these compounds compared to 

clopyralid, this contamination is not significant in terms 

of potential systemic toxic effects. In addition, the

contamination of clopyralid with hexachlorobenzene 

does not appear to present any substantial cancer risk

above the Forest Service cancer risk LOC of 1 in 1

million. 

Glyphosate 

For both workers and members of the general public, 

there are no risks associated with nearly all exposures to

glyphosate at the typical or maximum application rate 

(SERA 2003a). The risk assessment calculated no risk

for all but one of the tested scenarios, usually at least by

a factor of 5. There is low risk to children in the general 

public associated with accidental exposure to 

glyphosate consumption of contaminated water after an

herbicide spill into a small pond. 

Hexazinone 

Over the range of plausible application rates, all worker

groups exposed to hexazinone may face risks, with the

highest risks predicted for workers using an over-theshoulder broadcast applicator (belly grinder; SERA 

1997). Workers exposed to hexazinone via direct and 

broadcast ground spray and aerial applications at the 

maximum application rate are at low risk. There would 

be a low risk associated with accidental exposure to

hexazinone mixed for the maximum application rate via 

contaminated gloves (also low risk at the typical 

application rate) and via spills on lower legs. The most 

likely effects include irritation to the eyes, respiratory 

tract, and skin. Even under the most extreme exposure 

scenarios, outward toxic effects are not likely to be

observed; however, the upper estimates of exposure 

levels could be associated with subclinical (non-
TABLE 4-27

BLM-evaluated Herbicide Risk Categories by Aggregate Risk Index for Occupational Receptor

Dicamba Diflufenzopyr Diquat Fluridone Imazapic 

Receptor

Typ1 Max Accid Typ Max Accid Typ Max Accid Typ Max Accid2 Typ Max Acci

Plane - pilot NE3 NE NE NE NE NE L M H 0 0 L-H 0 0 NE Plane - mixer/loader NE NE NE NE NE NE M H H 0 L L-H 0 0 NE Helicopter - pilot NE NE NE NE NE NE L M H 0 0 L-H 0 0 NE Helicopter - mixer/loader NE NE NE NE NE NE M H H 0 L L-H 0 0 NE Human/backpack - applicator/mixer/loader 0 0 L 0 0 NE L M H 0 0 L-H 0 0 NE Human/horseback - applicator 0 0 L 0 0 NE L L H 0 0 L-H 0 0 NE Human/horseback - mixer/loader 0 0 L 0 0 NE 0 L H 0 0 L-H 0 0 NE Human/horseback - applicator/mixer/loader 0 0 L 0 0 NE L M H 0 0 L-H 0 0 NE ATV - applicator4 0 0 L 0 0 NE 0 L H 0 0 L-H 0 0 NE ATV - mixer/loader 0 0 L 0 0 NE 0 L H 0 0 L-H 0 0 NE ATV -applicator/mixer/loader 0 0 L 0 0 NE 0 L H 0 0 L-H 0 0 NE Truck - applicator4 0 0 L 0 0 NE 0 M H 0 0 L-H 0 0 NE Truck - mixer/loader 0 0 L 0 0 NE 0 L H 0 0 L-H 0 0 NE Truck - applicator/mixer/loader 0 0 L 0 0 NE 0 M H 0 0 L-H 0 0 NE Boat - applicator NE NE NE NE NE NE 0 0 H 0 0 L-H NE NE NE Boat - mixer/loader NE NE NE NE NE NE 0 0 H 0 0 L-H NE NE NE Boat - applicator/mixer/loader NE NE NE NE NE NE 0 0 H 0 0 L-H NE NE NE 1 Typ = Typical application rate; Max = Maximum application rate; and Accid = Accidental rate. Typical and maximum application rate categories include short-, interme

Accidental scenario category includes accidents with herbicide mixed at both the typical and maximum application rates and with a concentrated herbicide.

2 For all occupational receptors accidentally exposed to fluridone, there is low risk from exposure to solutions mixed with water to the typical application rate, moderate risk f

with water to the maximum application rate, and high risk from exposure to concentrated solutions (prior to mixing with water).

3 Risk categories: 0 = No risk (majority of ARIs > 1); L = Low risk (majority of ARIs >1 but < 0.1); M = Moderate risk (majority of ARIs > 0.1 but < 0.01); H = High risk 

NE = Not evaluated. The reported risk category represents the typical/most common risk level for estimated risks from various time periods. See the Vegetation Treatm

Health Risk Assessment Final Report (ENSR 2005l) for the range of risk levels for each scenario.

4 ATV and Truck categories include spot and boom/broadcast application scenarios.

BLMVegetationTreatments Using Herbicides 4-185 June 2007 

FinalProgrammaticEIS
TABLE 4-28 

BLM-evaluated Herbicide Risk Categories by Aggregate Risk Index for Public Receptors

Dicamba Diflufenzopyr Diquat Fluridone Imazapic 

Receptor

Typ1 Max Accid Typ Max Accid Typ Max Accid Typ Max Accid Typ Max 

Hiker/hunter (adult) 02 0 0 0 0 0 0 L L 0 0 0 NE NE Berry picker (child) 0 0 0 0 0 0 0 L L 0 0 L NE NE Berry picker (adult) 0 0 0 0 0 0 0 L L 0 0 0 NE NE Angler (adult) 0 0 0 0 0 0 0 L L 0 0 0 NE NE Residential (child) 0 0 0 0 0 0 L L M 0 0 L NE NE Residential (adult) 0 0 0 0 0 0 0 L M 0 0 L NE NE Native American (child) 0 0 0 0 0 0 0 L L 0 0 0 0 0 Native American (adult) 0 0 0 0 0 0 0 L L 0 0 0 0 0 Swimmer (child) 0 0 0 0 0 0 0 0 L 0 0 0 0 0 Swimmer (adult) 0 0 0 0 0 0 0 0 L 0 0 0 0 0 1 Typ = Typical application rate; Max = Maximum application rate; and Accid = Accidental rate. Typical and maximum application rate categories include short-, interm

Accidental scenario category includes accidents with herbicide mixed at both the typical and maximum application rates and with a concentrated herbicide.

2 Risk categories: 0 = No risk (majority of ARIs > 1); L = Low risk (majority of ARIs >1 but < 0.1); M = Moderate risk (majority of ARIs > 0.1 but < 0.01); H = High r

NE = Not evaluated. The reported risk category represents the typical/most common risk level for estimated risks from various time periods. See the Vegetation Trea

Health Risk Assessment Final Report (ENSR 2005l) for the range of risk levels for each scenario.

BLMVegetationTreatments Using Herbicides 4-186 June 2007 

FinalProgrammaticEIS
TABLE 4-29

Forest Service-evaluated Herbicide Risk Categories by Hazard Quotient for Occupational Exposu

Risk Categories

2,4-D1 Chlorsulfuron Clopyralid Glyphosate Hexazinone Imazapyr Metsulfuron Methyl 

Treatme 

nt Method

Typ2 Max Typ Max Typ Max Typ Max Typ Max Typ Max Typ Max 

General ExposuresDirected foliar and spot treatments (backpack) L3 L 0 0 0 0 0 0 0 L 0 0 0 0 Broadcast ground spray(boom spray) L M 0 L 0 0 0 0 0 L 0 0 0 0 Aerial applications (pilots and mixer/loaders) L L 0 0 0 0 0 0 0 L 0 0 0 0 Aquatic applications L L NE NE NE NE NE NE NE NE NE NE NE NE Accidental/Incidental ExposuresImmersion of hands 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Wearing contaminated gloves M M 0 0 0 0 0 0 L L 0 0 0 0 Spill on hands L L 0 0 0 0 0 0 0 0 0 0 0 0 Spill on lower legs L M 0 0 0 0 0 0 0 L 0 0 0 0 1 Where different formulations exist, risks reported are the most conservative. 2 Typ = Typical application rate; and Max = Maximum application rate.

3 Risk categories: 0 = No risk (majority of HQs < 1); L = Low risk (majority of HQs >1 but < 10); M = Moderate risk (majority of HQs > 10 but < 100); H = High risk (majo

NE = Not evaluated. Risk categories are based on typical and upper HQ estimates. To determine risk for lower or central HQ estimates, see the individual herbicide risk ascategories are based on comparison to the HQ of 1 for typical and maximum application rates. 

BLMVegetationTreatments Using Herbicides 4-187 June 2007 

FinalProgrammaticEIS
TABLE 4-30

Forest Service-evaluated Herbicide Risk Categories by Hazard Q

uotient for Public Expos

ures 

Hazard Q

uotient 

2,4-D1 Chlorsulfuron Clopyralid Glyphosate Hexazino

ne Imazapyr Metsulfuron 

Treatme

nt Method

Ty

p2 Max Typ Max Typ Max Typ Max Typ 

Max Typ Max Typ Max 

Acute/Accidental ExposuresDirect spray - child, entire body 03 M 0 0 0 0 0 0 L

M 0 0 0 0 

Direct spray - woman, lower legs 0 L 0 0 0 0 0 0 0 L 0 0 0 0 Dermal - contaminated vegetation, woman 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Consumption of contaminated fruit L M 0 0 0 0 0 0 0 L 0 0 0 0 Consumption of contaminated water - pond, spill M H 0 0 0 L 0 L M M 0 0 0 0 Consumption of contaminated water - stream, a

mbient L L 0 0 0 0 0 0 0 

L 0 0 0 0 

Consumption of contaminated fish - general public M M 0 0 0 0 0 0 L L 0 0 0 0 Consumption of contaminated fish - subsistence populations H H 0 0 0 0 0 0 M M 0 0 0 0 Chronic/Longer-term ExposuresConsumption of contaminated fruit 0 L 0 0 0 0 0 0 0 L 0 0 0 0 Consumption of contaminated water 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Consumption of contaminated fish - general public 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Consumption of contaminated fish - subsistence populations 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 Where different formulations exist, risks reported are the most conservative. 2 Typ = Typical application rate; and Max = Maxi

mum application rate.

3 Risk categories: 0 = No risk (

majority of HQs < 1); L = Low risk (majority of HQs >1 but < 10); M = 

Moderate risk (majority of HQs > 10 but < 100); H = High risk (major

evaluated. Risk categories are based on typical and upper HQ estimates. To determine risk for lower or central HQ estimates, see the individual herbicide risk assessments (based on co

mparison to the HQ of 1 for typical and 

maximum application rates.

BLM Vegetation Treatments Using Herbicides 4-188 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

symptomatic) effects and possible reproductive effects.

In some accidental exposure scenarios, members of the

general public may face risks from exposure to

hexazinone. At the typical application rate, there is low 

to moderate risk to public receptors associated with 

exposure to hexazinone under the following scenarios:

direct spray of the entire body, acute consumption of

water contaminated by a spill, and acute consumption of

contaminated fish by the general public and subsistence 

populations. For application at the maximum rate, the 

risks to public receptors associated with the above

scenarios are low to moderate. The following additional

scenarios pose a low risk: direct spray of the lower legs, 

acute and chronic consumption of fruit, and

consumption of stream water contaminated by runoff or 

percolation. 

Imazapyr

Most exposures to imazapyr at either the typical or the

maximum application rate do not present a risk to either 

workers or members of the general public, suggesting 

that workers and the general public would generally not

be at any substantial risk from longer-term exposure to

imazapyr even at the upper range of the application rate 

considered in the risk assessment (SERA 2004d). From

a practical perspective, eye irritation is likely to be the

only overt effect as a consequence of mishandling

imazapyr. This effect can be minimized or avoided by 

prudent industrial hygiene practices during the handling

of the compound. 

Metsulfuron Methyl 

Typical exposures to metsulfuron methyl at the typical

or maximum application rates do not present a risk to

workers or the general public (SERA 2004e). For 

workers, there is no risk associated with acute or

chronic exposure scenarios, even at the upper ranges of 

estimated dose. For members of the general public, no 

risks were predicted for any of the exposure scenarios. 

From a practical perspective, eye and skin irritation are

likely to be the only overt effects of mishandling 

metsulfuron methyl. These effects can be minimized or 

avoided by prudent industrial hygiene practices during

the handling of this compound. 

Picloram 

Typical exposures to picloram at either the typical or

maximum application rates present few risks to workers 

or the general public (SERA 2003b). For workers, no 

risks were predicted even at the upper ranges of

exposure. For members of the general public, no risks 

were predicted except for the consumption of water by a

child following an accidental spill of a large amount of

picloram into a very small pond, which presents a low 

risk. From a practical perspective, eye irritation and skin 

sensitization are likely to be the only overt effects as a

consequence of mishandling picloram. Based on the 

standard assumptions used in this and other Forest 

Service risk assessments, the contamination of picloram

with hexachlorobenzene does not appear to present a 

substantial cancer risk, even at the upper ranges of

plausible exposure. 

Triclopyr 

Workers face low risk from directed and broadcast 

ground spray and aerial applications at the upper ranges 

of exposures for both evaluated formulations of 

triclopyr (triclopyr acid and triclopyr BEE), at the 

maximum application rate (SERA 2003c). At the 

maximum application rate, workers face low risk from

accidental exposure to contaminated gloves (1 hour 

duration). Thus, for workers who may apply triclopyr 

repeatedly over a period of several weeks or longer, it is 

important to ensure that work practices involve 

reasonably protective procedures to avoid the upper 

extremes of potential exposure. At higher application

rates, measures that limit exposure should be developed

on a case-by-case basis depending on the application

rate and method. There is low to moderate risk to the

general public from triclopyr applications under several

acute or accidental scenarios: 1) direct spray to the

entire body; 2) direct spray to the lower legs; 3) dermal

contact with contaminated vegetation; 4) acute

consumption of contaminated fruit (maximum

application rate only); and 5) acute consumption of

pond water contaminated by a spill. 

Human Health Risks Associated with Herbicides

Evaluated in Previous BLM EISs and Literature 

Review 

As discussed earlier, the human health risks of asulam, 

atrazine, bromacil, diuron, fosamine, mefluidide, 

simazine, tebuthiuron, and 2,4-DP were evaluated in

earlier BLM vegetation treatment EISs. These 

herbicides were not reevaluated in the BLM HHRA for 

the current PEIS because a literature review and 

evaluation showed that most toxicity values for these 

herbicides reported in more recent studies were not

substantially lower (i.e., present more risk) than the

values used to assess risks to human health in the 1991 

13-State EIS (McMullin and Thomas 2000). Tables 4-

31 and 4-32 present summaries of the risks to 

occupational and public receptors associated with the 

BLM Vegetation Treatments Using Herbicides 4-189 June 2007 

Final Programmatic EIS 
ENVI

BLM 

Final Pr

nine herbicides that were ev

and subseque

calculate a m

NOAEL divided by

the MOE used in the

estim

summ

that pose a high risk, whe

MOS less than 100, or a c

than 1 in 1 m

also report

scenarios, a

Another difference betwee

earlier EIS HHRAs is the t

current HHR

values for the various expo

term

convened a panel to dev

project. This ensured that the

current 

the benefit of peer review. 

values, the USEPA selected the 

from

protective of all other potent

that 

methodology

guidance. However, during

EISs, 

on the 

for evaluatio

evaluated separate toxic endpoints for 

reproductive effect

the 

toxic endpoint

most sensitive 

2,4-DP 

According t

Management Final EIS

and hand app

application practices (USDI BLM 1988a). Backpack

and hand app

loaders, and a

system

exposures. Th

and cancer effect

associated wit

direct spra

reproductive, 

contam

reproductive risks associat

spray

RONMENTAL CONSEQUENCES

Vegetation Treatments Using Herbicides 4-190 June 2007 

ogrammatic EIS 

aluated in the earlier EISs 

nt literature reviews. The earlier EISs 

argin of safety (MOS), which is the 

 the exposure dose (and the same as 

 current HHRA), and cancer risk 

ates for potential carcinogens. The EISs included 

ary tables that identified herbicides and scenarios 

re high risk is identified as an 

ancer risk estimate greater 

illion. Therefore, Tables 4-31 and 4-32

 the high risk herbicides and exposure 

s presented in the earlier EISs. 

n this PEIS HHRA and 

oxicity assessment. For the 

A, the USEPA either provided toxicity 

sure durations (acute, short 

, long term) and exposure routes (oral, dermal), or 

elop these values for this 

 toxicity values used in the 

HHRA were consistently derived and have had 

In the development of these 

most sensitive endpoint 

 the most sensitive species; therefore, the values are 

ial toxic effects (i.e., those 

may occur at higher exposure levels). This 

 is standard practice for current HHRA 

 development of the earlier 

there was not much agency-derived information 

herbicides evaluated, nor was the methodology 

n as standardized. Thus, the authors 

systemic and 

s for each herbicide, rather than just 

most sensitive endpoint. Risks are discussed by 

 below, rather than in the context of the 

endpoint. 

o the 1988 California Vegetation 

 (1988 California EIS), backpack 

licators are at risk from typical 2,4-D 

licators and ground applicators, mixerpplicator/mixer-loaders are also at risk for 

ic and reproductive effects from maximum 

ere are risks for systemic, reproductive, 

s to workers and public receptors 

h accidental scenarios of spill to skin and 

y. Public receptors are at risk for systemic, 

and cancer effects as a result of picking 

inated vegetation, and for systemic and 

ed with drinking directly 

ed water and eating berries. Nearby residents also 

face risks for systemic and reproductive effects from 

treatments on public lands. 

Asulam 

According to the 1988 California EIS, asulam 

applications would pose few risks to workers or the 

public. Hand applicators would be at risk for systemic 

and reproductive effects from maximum exposures, 

while the public would be at risk from systemic, 

reproductive, and cancer effects from contact with 

vegetation by picking. 

Atrazine 

According to the 1991 13-State EIS, workers and the 

public would face numerous risks from exposure to 

atrazine. Workers would be at risk for systemic and/or 

reproductive effects under nearly all scenarios involving 

the typical application rate, and would be at risk for 

systemic, reproductive, and cancer effects under all 

scenarios involving the maximum application, as well 

as accidental scenarios. The public would be at risk for 

systemic and/or reproductive effects under several 

exposure scenarios involving the maximum application 

rate. The public would be at risk for systemic, 

reproductive, and cancer effects under all scenarios 

involving accidental exposures, except for contact with 

vegetation by a hiker or from fishing (systemic and 

reproductive effects only), or by living near a treated 

area (reproductive effect only). 

Bromacil 

According to the 1991 13-State EIS, there would be a 

risk to workers associated with several exposure 

scenarios involving typical bromacil application 

practices. Pilots and aerial mixer-loaders face a risk for 

systemic, reproductive, and cancer effects from typical 

and maximum exposures to bromacil. Backpack and 

hand applicators and ground applicators, mixer-loaders, 

and applicator/mixer-loaders are also at risk for 

systemic and reproductive effects from maximum 

exposures. Risks for systemic, reproductive, and cancer 

effects to workers and public receptors are associated 

with accidental scenarios of spill to skin (concentrate 

and mixture), direct spray (no cancer risk), consumption 

of fish from a directly sprayed water body (no cancer 

risk), consumption of directly sprayed berries (no 

cancer risk), and drinking from water contaminated by a 

truck spill or a jettison of mixture (no cancer risk). The 

cancer slope factor for bromacil used in the HHRA was 

the one available from the USEPA at the time of the 

1991 13-State EIS. However, in its most recent review 
TABLE 4-31 

Scenarios Resulti

ng in High Risk to Occupatio

nal Receptors from Herbicides Evaluated in the 1988-1991 BL

2,4-DP Asula

m Atrazine Bromacil 

Treatme

nt Method

Ty

p1 Max Accid Typ Max Accid Typ Max Accid Typ Max Accid 

Aerial pilot 02 0 NA 0 0 NA S,R S,R,C NA R,C S,R,C NA Aerial mixer-loader 0 0 NA 0 0 NA S,R S,R,C NA S,R,C S,R,C NA Aerial fuel truck operator 0 0 NA 0 0 NA 0 S,R,C NA 0 0 NA Backpack applicator S,R S,R NA 0 0 NA R S,R,C NA 0 S,R NA Ground mechanical applicator 0 S,R NA 0 0 NA R S,R,C NA 0 S,R NA Ground mechanical mixer-loader 0 S,R NA 0 0 NA S,R S,R,C NA 0 S,R NA Ground mechanical applicator/

mixer-loader 0 S,R NA 0 0 NA S,R S,R,C NA 0 S,R NA 

Hand applicator S,R S,R NA 0 0 NA R S,R,C NA 0 S,R NA Skin spill, concentrate NA NA S,R,C NA NA S,R,C NA NA S,R,C NA NA S,R,C Skin spill, mixture NA NA S,R,C NA NA S,R,C NA NA S,R,C NA NA S,R,C Direct spray, person NA NA NA NA NA NA NA NA S,R,C NA NA S,R 

Fosamine Mefluidide Simazine Tebuthiuron Treatme

nt Method

Typ Max Accid Typ Max Accid Typ Max Accid Typ Max Accid

Aerial pilot 0 0 NA 0 S NA S,R S,R NA R S,R NAAerial mixer-loader 0 0 NA 0 0 NA S,R S,R NA R S,R NAAerial fuel truck operator 0 0 NA 0 0 NA 0 0 NA 0 S NABackpack applicator S S,R NA 0 S NA 0 0 NA 0 S,R NAGround mechanical applicator 0 S NA 0 S NA 0 0 NA 0 S,R NA Ground mechanical mixer-loader 0 S NA 0 0 NA 0 0 NA 0 S,R NA Ground mechanical applicator/

mixer-loader 0 S NA 0 0 NA 0 0 NA 0 S,R NA 

Hand applicator 0 S NA S S NA 0 0 NA R S,R NA Skin spill, concentrate NA NA S,R NA NA S,R NA NA S,R,C NA NA 0 Skin spill, mixture NA NA S,R NA NA S,R NA NA S,R,C NA NA S,R Direct spray, person NA NA NA NA NA NA NA NA S,R NA NA S,R 1 Typ = Typical application rate; Max = Maxi

mum application rate; and Accid = Accidental application. 2 Risk categories: 0 = No risk; S = Syste

mic risk; R = Reproductive risk; 

C = Cancer risk; and NA = Not applicable. Marked scenarios are those that result in high risk

under the given herbicide. High risks are defined as those exposures that 

may result in a margin of safety (MOS) < 100 or a cancer risk greater than one-in-one

million.

The MOS is the N

O

E

L divided by the dose; therefore, the larger the M

OS, the s

maller the estimated hu

man dose co

mpared to the animal N

O

E

L, and the lower the

presu

med risk to human health. 

In the earlier BL

M

EISs, risk estimates were presented separately for different land uses (rangeland, public do

main forestland, oil and gas sites, ROW, and recreation and

cultural sites). In this table, the scenario is

marked if any of these land uses showed a high risk for the specific herbicide.

BLM Vegetation Treatments Using Herbicides 4-191 June 2007 

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-32

Scenarios Resulting in High Risk to Public Receptors from Herbicides 

Evaluated in the 1988-1991 BLM EISs 

2,4DP1 ASU Atrazine BRO DIUR FOS MEF Simazine TEB 

Treatment Method

Accid2 Accid Max Accid Accid Accid Accid Accid Max Accid Accid

Direct spray, person S,R,C3 0 R S,R,C S,R S,R 0 0 0 S,R,C S,R

Drinking directly sprayed 

water S,R 0 R S,R,C 0 S,R 0 0 0 S,R,C R 

Eating fish from directly

sprayed water 0 0 R S,R,C S,R S,R 0 0 0 S,R,C 0 

Immediate reentry, hiker 0 0 R S,R 0 S S S 0 0 0 

Immediate reentry, picker S,R,C S,R,C S,R S,R,C S,R S,R 0 0 0 S,R,C S,R 

Eating directly sprayed 

berries S,R 0 S,R S,R,C S,R S,R 0 0 0 S,R,C S,R 

Angler 0 0 0 S,R 0 0 0 0 R 0 0 

Nearby resident S,R 0 0 R 0 0 S 0 0 0 0 

Drinking water 

contaminated by a jettison 

of mixture 

NA NA 0 S,R,C S,R S,R NA 0 0 S,R,C S,R 

Drinking water 

contaminated by a truck 

spill 

NA NA 0 S,R,C S,R S,R NA S 0 S,R,C S,R

1 2,4DP = 2,4-DP; ASU = Asulam; BRO = Bromacil; DIUR = Diuron; FOS = Fosamine; MEF = Mefluidide; and TEB = Tebuthiuron. 2

 Accid = Accidental application; and Max = Maximum application rate. 3

 Risk categories: 0 = No risk; S = Systemic; R = Reproductive; C = Cancer; and NA = Not applicable. Marked scenarios are those that result in high

risk under the given herbicide. High risks are defined as those exposures that may result in a margin of safety (MOS) < 100 or a cancer risk greater

than one-in-one million. The MOS is the NOEL divided by the dose; therefore, the larger the MOS, the smaller the estimated human dose compared

to the animal NOEL, and the lower the presumed risk to human health. 

In the earlier BLM EISs, risk estimates were presented separately for different land uses (rangeland, public domain forestland, oil and gas sites, ROW, 

and recreation and cultural sites). In this table, the scenario is marked if any of these land uses showed a high risk for the specific herbicide. 

of bromacil, the USEPA did not provide a cancer slope 

factor (USEPA 1994b), therefore bromacil is likely not 

carcinogenic. 

Diuron

According to the 1991 13-State EIS, there are risks to

workers and the general public associated with both 

routine and accidental exposures to diuron. Aerial

application poses a risk to most evaluated public 

receptors for systemic effects from worst-case

exposures (e.g., direct exposure of hikers, berry pickers,

anglers, and nearby residents; spray drift to skin;

vegetation contact by berry pickers; consumption of 

contaminated drinking water and fish). Berry pickers 

also face a risk for systemic effects from worst-case 

direct exposure and contact with vegetation scenarios. 

In aerial application scenarios, pilots and mixer-loaders 

are at risk for systemic and reproductive effects under 

both typical and worst-case exposures, and fuel-truck

operators are at risk for systemic and reproductive 

effects under worst-case exposures. In addition, 

backpack and hand applicators and ground applicators, 

mixer-loaders, and applicator-mixer-loaders are at risk

for systemic and reproductive effects for typical

(systemic only) and worst-case exposures. There are 

also risks to workers and the public for systemic and 

reproductive effects associated with accidental

exposures of spill to skin (herbicide concentrate and

mixture), direct spray, drinking or eating fish from a 

directly sprayed water body, or immediate reentry into a 

sprayed area by a berry picker. 

Fosamine 

According to the 1991 13-State EIS, there would be few 

risks to workers associated with applications of 

mefluidide. Backpack applicators could experience 

systemic effects at the typical and maximum rates, and

ground applicators and hand applicators could 

BLM Vegetation Treatments Using Herbicides 4-192 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

experience systemic effects at the maximum rate. 

Backpack applicators could also experience

reproductive effects as a result of applications at the

maximum rate.

Mefluidide 

According to the 1991 13-State EIS, there would be few 

risks to workers associated with applications of 

mefluidide. Pilots, backpack applicators, and hand 

applicators could experience systemic effects as a result

of application of mefluidide at the maximum rate, and

hand applicators could experience systemic effects as a

result of applications at the typical rate. Hikers 

reentering a treated area, or drinking water from a spill

at the accidental rate would be at risk for systemic

effects. 

Simazine 

According to the 1991 13-State EIS, potential effects to

workers would be limited to systemic and reproductive 

effects to pilots and aircraft mixer-loaders, and would 

be associated with application at the typical and 

maximum application rates. In addition, a spill to a

worker’s skin of either a concentrate or mixture of

simazine could result in systemic, reproductive, and

cancer effects. The public could experience systemic,

reproductive, and cancer effects under most accidental 

scenarios analyzed in the HHRA. However, hikers

entering recently treated areas and contacting 

vegetation, anglers, and nearby residents would not be 

at risk under accidental exposure scenarios. 

Tebuthiuron 

According to the 1991 13-State EIS, tebuthiuron poses 

health risks to workers under various application 

scenarios. Typical and worst-case aerial application 

exposure to tebuthiuron could result in systemic and 

reproductive effects to pilots and to mixer-loaders (no

systemic risk at typical exposures). Fuel-truck operators 

could experience systemic effects from worst-case 

exposure to tebuthiuron during aerial application.

Backpack applicators face systemic and reproductive 

risks from worst-case exposures to tebuthiuron. For 

workers using ground mechanical equipment, there are 

systemic and reproductive risks to applicators, mixerloaders, and applicator/mixer-loaders associated with 

worst-case exposures to tebuthiuron. Hand applicators 

are at risk from typical (reproductive effects) and worstcase (systemic and reproductive effects) exposures.

Several accidental scenarios also pose a risk for 

systemic and reproductive effects to workers and the 

public: 1) spill of herbicide mixture to skin; 2) direct

spray to person; 3) drinking directly sprayed water 

(reproductive only); 4) immediate reentry of a berry 

picker into a sprayed area; 5) consumption of directly

sprayed berries; and 6) consumption of water 

contaminated by a jettison of mixture or by a truck spill. 

Human Health Risks by Application Method 

Air 

Aerial applications of herbicides generally pose a 

greater risk due to off-site drift than ground 

applications, as herbicides applied at greater distances 

from the ground are able to drift farther from the target

application area. Therefore, risks to public receptors 

recreating or living near an application area would

extend out greater distances if the herbicide was applied

aerially than if it was applied by a ground application 

method. The BLM does not apply dicamba and 

diflufenzopyr by air. 

Ground 

Ground applications typically pose a lower risk to offsite receptors than aerial applications because the 

receptors are less likely to be exposed to spray drift.

Similarly, spot rather than boom/broadcast applications

are less likely to result in adverse effects to downwind 

receptors. However, these spot applications could 

present an increased risk to the occupational receptors 

charged with applying the herbicide because they are

more likely to come into contact with the herbicide 

(their exposure doses may be higher). In particular, 

occupational receptors applying diquat by backpack and 

horseback would be at low to moderate risk for adverse 

effects from exposure to the herbicide, whereas those 

applying diquat at the typical application rate by ATV 

or truck would not be at risk. In contrast, chlorsulfuron

does not pose a risk to workers involved with aerial

applications, but does pose a risk to workers conducting

ground broadcast applications at the highest application

rate, and exposure to hexazinone is greatest for workers 

using an over-the-shoulder broadcast applicator. 

Typical Application Rate 

Most of the herbicides do not present a risk to human

receptors when applied at the typical application rate. 

Diquat applications at the typical application rate would

pose a low to moderate risk to plane and helicopter

pilots and mixer/loaders, backpack 

applicator/mixer/loaders, horseback applicators and

applicator/mixer/loaders, and child residents. 2,4-D, 2,4-

BLM Vegetation Treatments Using Herbicides 4-193 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

DP, atrazine, bromacil, diuron, hexazinone, simazine, 

and tebuthiuron also pose a risk to various public and 

occupational receptors when applied at the typical

application rate. 

Maximum Application Rate 

At the maximum application rate, more herbicides, in a 

greater number of exposure scenarios, have the potential

to adversely affect human health. Fluridone, 

chlorsulfuron, clopyralid, glyphosate, picloram and

triclopyr do not pose a risk when applied at the typical

application rate, but do pose a risk under one or more 

exposure scenarios when applied at the maximum 

application rate. Clopyralid, glyphosate and picloram 

pose a low risk under the accidental scenario involving 

consumption of water from a small pond that has 

experienced a recent spill of herbicides mixed for the 

maximum application rate, which is a very unlikely 

scenario. In addition, a greater number of exposure 

scenarios and receptors are at risk for adverse effects 

from herbicide applications at the maximum application 

rate. Dicamba, diflufenzopyr, imazapic, imazapyr,

metsulfuron methyl, and sulfometuron methyl do not 

pose a risk to any receptor when applied at the

maximum (or typical) application rate. 

Accidental Direct Spray and Spill Scenarios 

Accidental direct spray and spill scenarios for many

herbicides pose a risk to many receptors (accidental 

scenarios for diflufenzopyr, imazapic, and sulfometuron

methyl were not evaluated because these chemicals are

not considered toxic through short-term dermal

exposure). These scenarios are unlikely, and can be 

avoided by following SOPs. 

Human Health Risks by Receptor 

Occupational 

2,4-D, 2,4-DP, asulam, atrazine, bromacil, diquat, 

diuron, fosamine, mefluidide, simazine, and tebuthiuron 

pose risks to occupational receptors when applied at

both typical and maximum application rates. Atrazine 

and diuron pose a risk to most receptors at the typical 

application rate. For 2,4-D, atrazine, diquat, bromacil,

simazine, and tebuthiuron, receptors working with aerial

applications would be at low to moderate risk for 

adverse effects, even for applications at the typical 

application rate, and all or most occupational receptors 

would be at risk when applying these herbicides at

maximum application rates. 2,4-D, 2,4-DP, atrazine, 

and fosamine also pose risks to ground applicators, 

particularly during applications at the maximum 

application rate. In addition, there are potential cancer 

risks to workers who apply atrazine and bromacil

aerially. Mixer/loaders working with aerial applications 

of fluridone are at low risk, and those working with 

atrazine, bromacil, diuron, simazine, and tebuthiuron

are at high risk when applying those herbicides at the 

typical and maximum application rates. 

Ground broadcast applicators are at risk from applying

atrazine and diuron at the typical application rate, and 

2,4-DP, bromacil, chlorsulfuron, fosamine, and

tebuthiuron at the maximum application rate. All

occupational receptors are at risk from applying

atrazine, hexazinone, tebuthiuron, and triclopyr at the 

maximum application rate. The rest of the scenarios of

potential exposure to herbicides pose risks to

occupational receptors were not predicted. Workers

involved in the aerial application of herbicides appear to

be at greater risk than other occupational receptors;

however, the application method that creates the most

risk to workers appears to depend on the herbicide, so

application methods for each herbicide should be

carefully evaluated with respect to potential human

health effects.

Public 

In general, there are lower risks to public receptors than 

occupational receptors. However, within this category,

there is higher risk to children than adults. Public 

receptors do not appear to be at risk from chlorsulfuron,

dicamba, diflufenzopyr, imazapic, imazapyr, 

metsulfuron methyl, or sulfometuron methyl 

applications (accidental scenarios were not evaluated for 

imazapic and sulfometuron methyl because these

chemicals are not toxic through short-term exposure for 

specific exposure routes). Diquat application at the

typical application rate poses a low risk to child

residents. At the maximum application rate, diquat 

poses a low to moderate risk to all public receptors, 

except swimmers. Under worst-case exposures, diuron

poses a risk to most public receptors. In addition, 2,4-D, 

2,4-DP, asulam, atrazine (also at maximum exposure), 

bromacil, clopyralid, diuron, fluridone, fosamine, 

glyphosate, hexazinone, mefluidide, picloram, simazine, 

tebuthiuron, and triclopyr may pose a risk to public

receptors under one or more accidental exposure 

scenarios (e.g., exposure resulting from the spill of an 

herbicide into a small pond). For most herbicides 

(except diquat), risk to public receptors can be 

minimized or avoided by using the typical application 

rate and following SOPs that greatly reduce the 

likelihood of accidents. 

BLM Vegetation Treatments Using Herbicides 4-194 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Impacts by Alternative 

The following is a qualitative discussion of how risk 

from herbicide exposure would vary under each 

herbicide treatment alternative. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative) 

Of the herbicide treatment alternatives (A, B, D, and E), 

the fewest acres treated would be under the No Action

Alternative. Therefore, health risks to occupational and 

public receptors would be lowest. If the No Action 

Alternative were to result in more acres being treated by 

other vegetation management methods (e.g., prescribed

fire, manual, biological treatments), then health risks 

from these methods would also have to be considered

(see the PER). In addition, the new herbicides proposed 

in this EIS (diflufenzopyr+dicamba [Overdrive®],

diquat, fluridone, and imazapic) would not be used. Of 

these new herbicides, diquat poses a potential risk to 

humans under various exposure pathways; however, 

diflufenzopyr, dicamba, fluridone, and imazapic are all

relatively safe to humans, with no potential adverse

effects predicted by the human health risk

characterization, except in cases of unlikely accidental 

exposures of fluridone. Of the 20 previously-approved

herbicides, only nine (asulam, clopyralid, fosamine, 

glyphosate, imazapyr, mefluidide, metsulfuron methyl, 

picloram and sulfometuron methyl) pose a similarly 

negligible to low risk to humans. Therefore, failure to

approve the four new herbicides would limit the options 

for treatment of vegetation without appreciable risk to

humans. As a consequence, the No Action Alternative 

may present greater risk to humans per each herbicide 

application than the other alternatives. In addition, this 

alternative may be less successful in controlling weeds 

and poisonous plants that adversely affect humans, 

especially weeds most effectively controlled by the four 

proposed herbicides. 

Under the No Action Alternative, the BLM would be 

able to continue to use six herbicides that were

approved for use under earlier BLM vegetation

treatment RODs: 2,4-DP, asulam, atrazine, fosamine,

mefluidide, and simazine (USDI BLM 1988b, 1991b, 

1992a). Except for fosamine, which has been used on

less than 50 acres annually, these chemicals have not

been used by the BLM since 1997 and are not proposed 

for use under the other herbicide treatment alternatives. 

In 1998, the BLM conducted a literature review to

determine if the earlier vegetation treatment ROD 

conclusions for asulam, atrazine, mefluidide, and

simazine were justifiable based on past and 1998 

toxicology and risk assessment procedures; a literature

review was not performed for 2,4-DP and fosamine, but

these herbicides were analyzed in the 1988 California

EIS (USDI BLM 1988a, McMullin and Thomas 2000). 

Based on this analysis, it was determined that systemic

risks associated with using asulam may be greater than

those projected in the earlier EIS, but that risks to 

humans from the other three herbicides were similar to, 

or less than, those identified in earlier EISs. 

Based on the earlier EISs, literature reviews done by the 

BLM, and other studies (USEPA 1995d, 2002), the

risks to humans would be low for asulam, fosamine, and

mefluidide, low to moderate for 2,4-DP and simazine, 

and moderate to high for atrazine. The BLM uses 

sulfometuron methyl, bromacil, and diuron in treatment

situations where it used atrazine in the past, and 

triclopyr instead of fosamine. These substitute

herbicides pose similar, or lower, risks to humans than

the herbicides they would replace. 

Alternative B – Expand Herbicide Use and Allow for 

Use of New Herbicides in 17 Western States 

(Preferred Alternative) 

This alternative would likely have the greatest overall 

risk to human health of the five alternatives considered

here because of the large number of acres treated. 

However, human health could benefit from the reduced 

occurrence of the noxious weeds and other invasive 

vegetation that would likely be brought about by this 

alternative. In addition, this alternative would include

the use of the new herbicides evaluated in the BLM 

HHRA (ENSR 2005l). Of these four herbicides, three 

(all but diquat) appear to be relatively harmless to 

humans; the use of these herbicides would increase the

options for appropriately managing vegetation while 

minimizing the risk to human receptors. Therefore, the

Preferred Alternative could result in more positive

impact to humans per application than the No Action

Alternative. However, the new herbicide diquat

potentially presents greater risk to humans in many

application scenarios, and it is suggested that diquat not

be used or be used only in very limited scenarios at the 

typical application rate, where there is risk to human

receptors (e.g., possibly ground applications from trucks

not near residences or berry gathering sites). 

Alternative C – No Use of Herbicides 

Alternative C would eliminate human health risk 

associated with herbicide applications. However, risks 

BLM Vegetation Treatments Using Herbicides 4-195 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

to humans associated with alternative vegetation 

management methods would likely increase (these risks 

are perhaps greatest for prescribed fire treatments [see

PER]). In addition, human health might be adversely 

affected if the noxious weeds and poisonous plants that

can harm humans increase in occurrence as a result of a 

cessation of herbicide treatments. 

Alternative D – No Aerial Applications 

Human health risks per application area would be lower 

under Alternative D than under the other herbicide 

treatment alternatives because herbicides would not be 

likely to drift as far, potentially affecting fewer humans. 

This alternative would allow the use of the new 

herbicides, which on average present less risk to

humans than the currently-used herbicides. Overall risks 

would be lower than under the Preferred Alternative, 

which would treat about 400,000 more acres and would 

use aerial spraying. However, under the Preferred

Alternative, the BLM may eliminate more unwanted

plants that adversely affect human health than under 

Alternative D. Overall risks would likely be similar to

those under Alternative E, as a similar number of acres 

would be treated, and Alternative E places emphasis on

spot applications over broadcast applications. However, 

Alternative E would prohibit the use of ALS-inhibiting

herbicide active ingredients (i.e., chlorsulfuron,

imazapic, imazapyr, metsulfuron methyl, and

sulfometuron methyl), which pose low risks to humans. 

Because the BLM would treat 240,000 more acres 

under Alternative D than under the No Action 

Alternative, but would not use higher risk aerial

applications and would use less risky chemicals, it is 

difficult to infer which alternative would have a lower 

overall risk. 

Alternative E – No Use of Acetolactate Synthaseinhibiting Herbicides

The five ALS-inhibiting herbicides (chlorsulfuron, 

imazapic, imazapyr, metsulfuron methyl, and

sulfometuron methyl) that would not be used under this 

alternative present some of the lowest risks with respect 

to human health. Even in accidental exposure scenarios,

imazapic, imazapyr, metsulfuron methyl, and

sulfometuron methyl do not pose a risk to humans, and

chlorsulfuron only poses a risk to workers where 

applied in ground broadcast applications at the highest

application rate. From a practical perspective, eye 

and/or skin irritation are likely to be the only overt

effects of mishandling the ALS-inhibiting herbicides, 

and these effects can be minimized or avoided by 

prudent industrial hygiene practices during the handling

of these compounds. Bromacil, diquat, diuron, and 

tebuthiuron, which pose greater human health risks, 

would not be excluded by Alternative E; therefore, risk

per area treated could increase if these herbicides were

used in place of ALS-inhibiting herbicides. Alternative 

E places increased emphasis on spot rather than

broadcast applications, which should mean that there 

would be less per area risk than under the No Action 

and Preferred alternatives, except in the few possible

cases where occupational receptors would be at greater

risk from spot applications. In addition, number of acres 

proposed for treatment (466,000) is half that of the

Preferred Alternative (932,000), which would

correspond to a lower overall risk. Conversely, more 

acres would be treated under Alternative E than under 

the No Action Alternative (305,000), which corresponds 

to a greater overall risk. Under Alternative D, the BLM

would treat more acres (540,000) than under Alternative 

E, but would not use aerial spraying, although there

would be a minimal amount of aerial spraying under 

Alternative E (spot applications are preferred over 

broadcast applications). However, Alternative D would

allow the use of the ALS-inhibiting herbicides, which

could limit the use of herbicides that may present higher 

human health risks, and correspond to a greater risk

than under Alternative E. 

Mitigation 

In addition to following SOPs, there are certain

herbicide-specific measures that can be taken to 

substantially reduce or eliminate human health risk from

herbicide use. The following mitigation measures were

developed based on the BLM HHRA, the Forest Service 

HHRAs, and the earlier BLM EIS HHRAs: 

• Use the typical application rate, where feasible, 

when applying 2,4-D, 2,4-DP, atrazine, 

bromacil, diquat, diuron, fluridone, fosamine, 

hexazinone, tebuthiuron, and triclopyr, to 

reduce risk to occupational and public

receptors. 

• Avoid applying atrazine, bromacil, diuron, or

simazine aerially. 

• Apply diquat by ATV, truck, or boat to reduce

risks to occupational receptors; limit diquat

applications to areas away from high 

residential and subsistence use to reduce risks 

to public receptors. 

• Evaluate diuron applications on a site-by-site 

basis to avoid risks to humans. There appear 

BLM Vegetation Treatments Using Herbicides 4-196 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

to be few scenarios where diuron can be

applied without risk to occupational receptors. 

• Do not apply hexazinone with an over-theshoulder broadcast applicator. 

Cumulative Effects Analysis 

The National Environmental Policy Act and its 

implementing guidelines require an assessment of the 

proposed project and other projects that have occurred 

in the past, are occurring in the present, or are likely to

occur in the future, which together may have cumulative

impacts that go beyond the impacts of the proposed 

project itself. According to the Act (40 CFR §1508.7

and 1508.25[a][2]): 

“Cumulative impact is the impact on the environment

which results from the incremental impact of the action 

when added to the other past, present, and reasonably 

foreseeable future actions regardless of what agency 

(federal or non-federal) or person undertakes such other 

actions. Cumulative impacts can result from

individually minor but collectively significant actions 

taking place over a period of time. In addition, to

determine the scope of Environmental Impact

Statements, agencies shall consider cumulative actions, 

which when viewed with other proposed actions have 

cumulatively significant impacts and should therefore

be discussed in the same impact statement.” 

The purpose of this cumulative effects analysis is to

determine if the effects of BLM vegetation treatments 

have the potential to interact or accumulate over time

and space, either through repetition or when combined 

with other effects, and under what circumstances and to

what degree they might accumulate. 

Structure of the Cumulative Effects 

Analysis 

For this Programmatic EIS, the analysis of cumulative

impacts is a four-step process that follows guidance 

provided in Considering Cumulative Effects Under the 

National Environmental Policy Act (CEQ 1997): 

• Specify the class of actions for which effects

are to be analyzed. 

• Designate the appropriate time and space

domain in which the relevant actions occur.

• Identify and characterize the set of receptors

to be assessed. 

• Determine the magnitude of effects on the

receptors and whether those effects are

accumulating.

Class of Actions to be Analyzed

This analysis addresses large, regional-scale trends and 

issues that require integrated management across broad

landscapes. It also addresses regional-scale trends and

changes in the social and economic needs of people. 

This analysis does not identify site-specific effects, in

part because of the level of specificity in broad-scale

management direction, and because site-specific

information is not essential for determining broad-scale 

management direction. As discussed in Chapter 1, 

Proposed Action and Purpose and Need, site-specific 

issues would be addressed through NEPA compliance 

for resource management activities and other land use 

plans prepared at the state, district, or field office level. 

The analysis of cumulative effects assumes that 

information provided in the PER is incorporated by

reference in its entirety into the cumulative effects 

analysis. The analysis of cumulative effects assumes 

that SOPs and mitigation measures identified in Chapter 

2 would be followed by the BLM under all alternatives 

to ensure that risks to human health and the

environment from herbicide treatment actions were kept 

to a minimum.

The analysis recognizes that prevention, early detection, 

and rapid response are the most cost effective methods 

for weed control. Prevention, early detection, and rapid

response strategies that reduce the need for vegetative 

treatments should lead to a reduction in the number of

acres treated using herbicides in the future by reducing 

or preventing noxious weed establishment. However, 

once weed populations become established, infestations 

can increase and expand in size. Weeds colonize highly

disturbed ground and invade plant communities that 

have been degraded, but are also capable of invading 

intact communities. 

As stated in the BLM’s Partners Against Weeds: An

Action Plan for the Bureau of Land Management [USDI

BLM 1996], prevention and public education are the 

highest priority weed management activities. Priorities 

are as follows: 

• Priority 1: Take actions to prevent or minimize

the need for vegetation control when and where 

feasible, considering the management

objectives of the site. 

BLM Vegetation Treatments Using Herbicides 4-197 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

• Priority 2: Use effective nonchemical methods 

of vegetation control when and where feasible. 

• Priority 3: Use herbicides after considering the 

effectiveness of all potential methods or in 

combination with other methods or controls. 

Although prevention, early detection, and rapid 

response are the most cost effective methods of weed

control, the analysis also recognizes that public lands 

must be administered under the principles of multiple

use and sustained yield in accordance with the intent of 

Congress as stated in the FLPMA. Thus, vegetation

must be managed to protect and enhance the health of 

the land while providing a source of food, timber, and

fiber for domestic needs (USDI BLM 2000c). Landdisturbing activities are allowed on public lands, but

must be conducted in a manner that minimizes 

ecosystem fragmentation and degradation, and lands 

should be rehabilitated when necessary to safeguard the

long-term diversity and integrity of the land. 

All vegetation treatment methods used by the BLM are 

considered in the analysis. These include herbicide use;

manual, mechanical, and biological control methods;

and use of fire, as identified in Chapter 2 (Alternatives). 

For this PEIS, potential cumulative effects include

those that were assessed for all land ownerships, 

including lands administered by other federal agencies 

and non-federal lands, particularly effects to air quality 

and terrestrial and aquatic species. 

The analysis and disclosure of cumulative effects alerts 

decision-makers and the public to the context within 

which effects are occurring, and to the environmental

implications of the interactions of known and likely

management activities. During subsequent analyses for 

site-specific activities, local cumulative effects should

be thoroughly considered when designing site-specific 

alternatives and mitigation measures. 

Appropriate Temporal and Spatial Domain 

Temporal Domain 

The analysis period covered by the cumulative effects 

analysis primarily begins in the 1930s with the passage 

of the Taylor Grazing Act, and continues through 2057. 

The ending date is based on the term that treatments 

would occur under this PEIS (about 10 years) and the 

time for treated areas to fully realize the results of the 

treatment in terms of meeting management objectives 

and desired vegetative conditions (up to 25 years or 

longer for some treatments). It is also based on the

difficulty of predicting advances in technology and the 

types and amounts of vegetation treatments needed very 

far into the future. Thus, a reasonable analysis period,

and one on which most of the cumulative effects 

analysis is focused, is 50 years into the future. 

Spatial Domain 

As discussed earlier, the BLM has been mandated under 

a variety of statutes and policy initiatives to increase the

number of acres of vegetation treated annually to

address the issues of catastrophic fire and invasive

species spread and their relationships to habitat

improvement and maintenance of healthy landscapes. 

The BLM estimates that approximately 6 million acres

would be treated annually over at least the next 10 years 

to meet these mandates. Acres to be treated by the BLM

and assessed in this PEIS were estimated based on 

information provided by BLM field offices throughout 

the western U.S., including Alaska. Treatments could 

occur on the same acres several times during a single 

year, or over several years. 

In developing acreage estimates for all alternatives, it

was assumed that if an acre was treated more than once 

using the same type of treatment during the same year,

it would be counted once. If the acre was treated using 

two or more different methods during the same year (for

example, fire use followed by herbicide treatment), each

treatment would count as one acre. Thus, if an acre was 

treated using fire and herbicides during the same year, 

two acres would be counted as treated. If an acre was 

treated using two or more herbicides in a tank mix, it 

would be counted once. 

For some resources and uses, the project area may be

where the effect can be felt (known as the “footprint”), 

but for others, the footprint may extend well beyond

that space. For example, air quality effects to humans

can extend miles beyond the footprint of the 

development. For the purposes of this analysis, the 

spatial domain for past, present, and reasonably 

foreseeable activities is primarily the 17 western states

evaluated in this PEIS. However, this PEIS also 

considers effects to resources that could occur outside of

these states. 

The alternatives analyzed in this PEIS identify 

alternative approaches to herbicide use, including 

abandonment of their use, as well as limitations on

which herbicides may be used or how herbicides may 

be applied. The effects of vegetation treatments 

disclosed in the PEIS and PER, combined with 

subsequent site-specific NEPA analysis, provide a

BLM Vegetation Treatments Using Herbicides 4-198 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

comprehensive assessment of cumulative effects of 

future vegetation treatment activities on public lands. In 

light of the broad geographic scope and spatial 

resolution of this PEIS, the cumulative effects analysis 

cannot and does not address all possible cumulative 

effects that may result at specific sites on public lands. 

For the purposes of this analysis, non-federal lands 

include lands owned and/or managed by individuals,

corporations, American Indian tribes, Alaska Native

corporations, states, counties, or other agencies. The 

BLM does not have the authority to regulate any 

activities or their timing on lands other than those the 

BLM administers. However, when an action takes place 

on public land, it may cause direct, indirect, or cumulative effects on non-federal lands. For example, a 

wildfire that begins on public land may burn to adjacent

private land, or noxious weed infestations that begin on

private land may infest adjacent public land. For these 

examples, treatment activities outlined in the PEIS and 

PER could benefit adjacent landowners indirectly as a

result of better controls on noxious weeds and less 

severe forest fires. 

This PEIS also considers the likely effects on public 

lands from reasonably foreseeable actions occurring

on non-federal land. For example, development of

non-federal land may potentially have direct impacts 

on terrestrial wildlife species that move between

federal and non-federal habitats during the year or 

during their life cycle. The role of management of

non-federal lands was considered in the analysis on

these species and their associated ecosystems.

Localized actions on non-federal lands often affect

local environmental conditions on nearby federal land

and may also affect federal management decisions. 

In preparing the cumulative effects assessment, the

BLM considered the magnitude and extent of BLM

herbicide treatments in relation to herbicide 

treatments conducted by other federal and state

agencies and private applicators, including treatments 

on privately-owned croplands and rangelands. The 

primary sources for this information were the BLM 

Pesticide Use Reports and the National Pesticide Use

Database (Croplife Foundation 2006). 

Based on the most recent information available for 

national pesticide use (2002), approximately 110

million pounds of herbicides were applied on nonfederal lands in the 17 western states evaluated in the 

PEIS (Table 4-33). Of this amount, approximately

80% of herbicides by weight were applied in

croplands, with the remainder applied in pasturelands

and rangelands. In comparison, the BLM applied 

approximately 115,500 pounds of herbicides in the 

western U.S. in 2002 (and 147,572 pounds in 2005). 

Other federal agencies that apply herbicides include 

the Forest Service (82,703 pounds applied during 

2004 within 17 western states). 

The National Center for Food and Agricultural Policy 

(2002) reviewed trends in herbicide, fungicide, 

insecticide, and other pesticide use between 1992 and 

2002 based on pounds of active ingredient applied to

agricultural rangelands and croplands. During that

period, herbicide use declined 5.5%, fungicide use 

declined 4.6%, insecticide use declined 21.2%, and 

other pesticide use increased 36.6% for the 17 western 

states. Overall pesticide use increased 2% during 

1992 to 2002. Between 1997 and 2005, BLM

herbicide use increased 21⁄2-fold and would increase 

another 4-fold (to about 650,000 pounds annually) 

under the Preferred Alternative. However, under the 

Preferred Alternative, BLM herbicide use would be 

only 0.2% of the total amount of pesticides that was 

applied to agricultural rangelands and croplands 

during 2002. 

Set of Receptors to be Assessed 

The set of receptors assessed in the cumulative effects 

analysis are the physical, biological, and human systems

discussed in Chapter 3 (Affected Environment). 

Magnitude of Effects and Whether Those Effects are 

Accumulating 

The potential extent of the total cumulative effects (e.g., 

number of animals and habitat affected), and how long

the effects might last (e.g., population recovery time) 

are estimated to determine the magnitude of effects that

could accumulate for each resource. Where possible, the 

assessment of effects on a resource is based on

quantitative analysis (e.g., level of risk to humans from

use of an herbicide). However, many effects are difficult 

to quantify (e.g., animal behaviors; human perceptions) 

and a qualitative assessment of effects is made. 

As suggested by the CEQ (1997) handbook,

Considering Cumulative Effects Under the National

Environmental Policy Act, this PEIS considers the

following basic types of effects that might occur: 

• “Additive” – total loss of sensitive resources 

from more than one incident.

• “Countervailing” – negative effects are 

compensated for by beneficial effects. 

BLM Vegetation Treatments Using Herbicides 4-199 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

TABLE 4-33

Herbicide Use in the Western United States for 

Agricultural Lands and BLM-administered Lands

Pounds of Herbicides Applied 

(2002) 

State Non-federaladministered 

lands 

BLMadministered 

lands 

Arizona 920,369 4,933 

California 12,929,480 2,621 

Colorado 4,565,041 2,108 

Idaho 3,532,008 2,826 

Montana 4,656,964 8,193 

Nebraska 22,614,643 

Nevada 55,648 5,379 

New Mexico,

Oklahoma, 

and Texas 

25,159,648 35,854 

North Dakota 14,192,512 11 

Oregon and 

Washington 7,354,557 11,403 

South Dakota 15,175,460 279 

Utah 690,410 23,829 

Wyoming 

and Nebraska 

704,570 18,066 

Total 109,588,484 115,502 

Sources: Croplife Foundation (2006) and BLM Pesticide Use 

Reports.

• “Synergistic” – total effect is greater than the

sum of the effects taken independently. 

The purpose of the analysis of cumulative effects in this 

PEIS is to determine whether the effects are additive or 

synergistic or have some other relationship. Additive (or 

combined) effects on specific resources often are

difficult to detect and do not necessarily add up in the

strict sense of one plus one equals two. It is much more 

likely that an additive or combined effect would be

greater than one but less than two. A synergistic effect,

in theory, is a total effect that is greater than the sum of 

the additive effects on a resource. To arrive at a

synergistic effect in this example (continuing with the

numeric analogy), the total cumulative effect would

need to end up greater than two. In the highly variable

western U.S. environment, where natural variations in 

population levels can exceed the impacts of human 

activity, such an effect would need to be much greater 

than the hypothetical two to be either measurable or

noteworthy. A countervailing effect has both negative

and beneficial components. For example, herbicide 

treatments would harm or destroy vegetation used by

some species of wildlife (negative effect), but would 

improve overall ecosystem health and lead to improved

watershed conditions and habitat for other wildlife 

(positive effect). 

In the analyses that follows, effects should be 

considered to be additive in nature, unless otherwise

noted. While synergistic impacts have been

demonstrated in the laboratory (for certain types of 

chemical reactions, for example), there is almost no

evidence of such impacts occurring when dealing with

biological resources. Where synergistic impacts are not

specifically accounted for in the analysis section, neither

studies nor other information are available to support 

the identification of such impacts. 

Herbicide formulations are a commercial mixture of 

both active and inert (inactive) ingredients. Inert

ingredients are ingredients that are added to the 

commercial product (formulation) but are not

herbicidally active. As part of the ERA, the BLM

assessed the general risks to plants and animals from

inert ingredients found in herbicide formulations and 

from adjuvants. The ERAs also addressed potential

risks associated with: 

• Adjuvants – Chemicals that are added to the 

herbicide formulation to enhance the toxicity of the

active ingredient or to make the active ingredient 

easier to handle. They include surfactants, materials 

that improve the emulsifying, dispersing, spreading, 

wetting, or other surface-modifying properties of

liquids. 

• Degradates – physical or biological breakdown

compounds of a complex compound. 

Based on concerns raised by the Services and the public

about adjuvants, degradates, and an issue not addressed

in the Draft PEIS or BA―the potential for herbicides to 

be endocrine disrupting chemicals―the BLM prepared

an Evaluation of Risks from Degradates, 

Polyoxyethyleneamine (POEA)) and R-11, and 

Endocrine Disrupting Chemicals for the Final PEIS (see

Appendix D of the Final PEIS) that addressed the 

following questions: 

• Some surfactants may be more toxic to aquatic

receptors than the active ingredient in an 

herbicide. Using polyoxyethyleneamine 

(POEA) as an example, what are the potential

impacts of surfactants in Roundup Original®

and Honcho® applied with glyphosate?

BLM Vegetation Treatments Using Herbicides 4-200 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

• The quantitative risk assessments only address 

the potential impacts of the active ingredients. 

What about the toxicity of degradates?

• The risk assessments did not identify endocrine

disruption as a toxic endpoint. Are any of the 

herbicides considered to be endocrine 

disrupting chemicals?

The BLM ERAs also addressed potential risks 

associated with tank mixtures―the mixture of two or

more compatible herbicides in a spray tank in order to

apply them simultaneously. 

The BLM used mixtures of two or more herbicides to 

treat approximately 25% of public lands during 2003 to 

2005. The use of tank mixtures, along with the addition 

of an adjuvant (when stated on the label), may be an

efficient use of equipment and personnel; however, 

knowledge of all products and their interactions is 

necessary to avoid unintended negative effects. The 

BLM evaluated tank mixtures to determine whether

herbicide interactions can be classified as additive,

synergistic, or antagonistic. 

The analysis assumes that maintenance of past

treatments has occurred, and that the BLM would make 

an investment in maintaining the condition achieved or 

the objectives of the project, rather than implementing 

stand-alone, one-time treatments. The analysis also

assumes that the BLM would determine the need for the

action based on past monitoring, and that additional 

monitoring would occur after the project to ascertain if 

effects are still accumulating or if the treatment has 

been effective in achieving the resource objective. 

Resource Protection Measures 

Considered in the Cumulative Effects 

Analysis 

The cumulative impacts assessment assumes that SOPs,

monitoring measures, and mitigation developed by the 

BLM for the alternatives (see Chapter 2 of the PEIS and

PER) would be adopted to protect environmental and

socioeconomic resources on public lands. 

In addition, a number of federal, state, local, and tribal 

resource management and monitoring programs have 

been established to protect environmental resources and, 

in cases where there is existing environmental

impairment, to effect restoration. The assessment of 

cumulative impacts recognizes the existence of these

programs and assumes that the mandate under which

each program was established will continue. The 

cumulative effects analysis assumes that these programs 

effectively avoid or mitigate the environmental impacts 

that they are designed to address. The programs are 

discussed in the sections that follow. 

Air Quality 

Air quality is regulated under the PSD permitting

process. For sources located in state waters and onshore, 

the PSD program is administered by the state air quality 

agencies. Although minor sources of air pollutants are 

not subject to PSD permitting requirements, the analysis

of cumulative effects to air quality in this PEIS 

considers the contribution of both major and minor 

sources of air pollution in the western U.S., including 

and Alaska. 

Water Quality 

Water quality is regulated and/or monitored through 

various permitting and regulatory programs 

administered by the USEPA and state and local

regulatory agencies. These programs have been 

established to protect against the significant degradation

of water quality associated with specific human and 

development activities. In evaluating the cumulative 

effects to water quality, collective impacts associated

with regulated and non-regulated activities and naturally 

occurring events are considered. 

Wetlands 

Wetland impacts are mitigated through SOPs, permits, 

and approvals issued at the project implementation

stages (if needed), and under Section 404 of the Clean

Water Act, administered by the USACE, and state

certification programs to protect wetlands and ensure no

net loss of wetlands, where practical. 

Essential Fish Habitat 

The amended Magnuson-Stevens Act requires federal

agencies that authorize, fund, or conduct activities that 

may harm Essential Fish Habitat to work with NMFS to

develop measures that minimize damage to EFH. By

providing EFH conservation recommendations before 

an activity begins, NMFS may help prevent habitat

damage before it occurs, rather than restoring habitat

after the fact, which is less efficient, unpredictable, and

often more costly. An analysis of EFH effects is 

provided as Appendix A in the Vegetation Treatments

on Bureau of Land Management Lands in 17 Western 

States Programmatic Biological Assessment (USDI

BLM 2006b). 

BLM Vegetation Treatments Using Herbicides 4-201 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Threatened and Endangered Species 

The Endangered Species Act of 1973 and the PEIS 

scoping process are appropriate vehicles to identify 

species that are potentially at risk from the incremental

cumulative effects of activities that may occur under the 

PEIS and PER. Effects on listed species identified for 

the analysis area by NMFS and the USFWS under 

Section 7 of the ESA are covered by this cumulative 

analysis. The potential effects on each of the other

species identified through scoping have also been

reviewed and included, as appropriate. 

Environmental Justice 

Executive Order 12898, Federal Actions to Address 

Environmental Justice in Minority Populations and 

Low-Income Populations, and an accompanying 

Presidential memorandum require each federal agency 

to make the consideration of environmental justice part

of its mission. The existing demographics (race and 

income) and subsistence consumption of plants and 

animals, and mitigating measures and their effects, are

presented. 

Consultation and Coordination with Indian Tribal 

Governments 

Executive Order 13175, Consultation and Coordination

with Indian Tribal Governments, requires consultation 

with tribal governments on “actions that have 

substantial direct effects on one or more Indian tribes.” 

Representatives of the BLM have met with local tribal

governments to discuss subsistence issues pertaining to 

the PEIS and PER (see Chapter 5, Consultation and 

Coordination), and have established a dialogue on

environmental justice with these communities. 

Other Information Considered in 

Cumulative Effects Analysis 

The assessment of cumulative impacts from vegetation

treatment activities also considered the following 

information and assumptions: 

• Mitigation and SOPs identified in PEIS would 

be more stringent than those required by the 

USEPA. 

• The BLM would comply with existing and

future regulations, including FLPMA. 

Ground-disturbing activities on public lands are

conducted only after any necessary site-specific NEPA 

analysis has been completed. Such analyses are required

to describe the cumulative impacts of the site-specific

alternatives on adjacent lands and resources. This 

process provides opportunities to detect and minimize 

cumulative environmental effects that cannot be 

specifically determined at the broad level of this PEIS. 

Subsequent analyses will help ensure that the 

incremental and interactive effects on public lands 

would continue to be considered when implementing

treatment actions. 

Analysis of Cumulative Effects by 

Resources 

Air Quality 

Cumulative impacts to air quality could result from the

emissions of particulates associated with wildfire,

wildland fire use and prescribed fire, as well as 

particulates, hydrocarbons, and other byproducts of

combustion associated with the use of equipment. 

Indirect impacts from air emissions include impacts to

human health and global climate change. These impacts 

may be regionally additive (e.g., increased 

concentrations of specific pollutants) or synergistic

(e.g., chemical reactions that form ozone). Technology 

has played an important role in reducing air emissions 

from engine operation, and an important reason for 

conducting prescribed burns is to better control smoke 

emissions and to reduce future smoke emissions 

associated with wildfire. 

Past Effects and Their Accumulation 

The cumulative effects of pollutant-producing

activities in the past have led to deterioration in air

quality in the western United States. Detailed

information about the historic and existing air quality 

in the area covered by this PEIS is only available for 

monitoring sites and for criteria pollutants. In the

undeveloped regions of public lands, ambient

pollutant levels are expected to be low, and probably

negligible in remote areas. On public lands on the 

Alaska North Slope and much of the remaining

portions of Alaska, air quality is generally good, 

except during periods with Arctic haze (USDI BLM 

2005c). In general, locations in the treatment area 

with high ambient pollutant levels are areas that

support commercial and industrial land uses (areas 

with large-scale mining operations, lumber mills, 

power plants or downwind from power plants, oil and 

natural gas extraction, etc.) and local population

centers (areas with automobile exhaust, residential

BLM Vegetation Treatments Using Herbicides 4-202 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

heating, etc). 

Despite increases in human population and 

industrialization, emissions of principal air pollutants 

in the U.S., after peaking in the 1970s and early

1980s, have generally declined or held steady during

the past 2 decades due to more stringent air quality 

regulations and improvements in pollution control 

technology (USEPA 2005). Particulate matter is the 

principal pollutant of concern, from a public health 

perspective, that is generated by fire. Emissions of

particulate matter from all sources have trended lower 

since the 1970s. However, PM emissions nationwide 

have shown a close relationship with the number of 

acres burned annually by wildfire. Since 1990, PM

emissions associated with wildfire have ranged from

145,000 tons in 1995 to 1.2 million tons in 2002; the 

number of acres burned by wildfires in 1995 was onethird the number of acres burned in 2002. The level of 

PM associated with slash and prescribed burning, 

however, has trended downward since the 1970s, and 

in 2001 (165,000 tons) was about half the level of the 

early 1990s. Based on an estimate of emissions 

generated by current vegetation treatment activities 

(primarily from fire and mechanical treatments; see

Table 4-4 in PER), BLM treatment activities have 

accounted for less than 0.5% of criteria pollutant 

emissions nationwide. 

Future Effects and Their Accumulation 

Under the action alternatives, emissions associated 

with wildland fire use and prescribed fire and other 

treatment methods would be greater than those under 

the No Action Alternative. Still, emissions associated

with BLM vegetation treatment activities would

comprise less than 1% of total criteria pollutants 

generated nationwide. If the BLM were to achieve its 

goal of treating about 2 million acres annually using 

fire, annual emissions of PM from prescribed and 

wildland fire use on public lands would be similar to

the total amount of PM emissions currently produced 

in the U.S. from prescribed fire, but would be only 

one-sixth the amount of PM produced by wildfires

annually in recent years (USEPA 2005). 

Although modeling was not done as part of the PER 

and PEIS to assess cumulative effects from use of fire

and other treatment methods, modeling was done as 

part of a programmatic assessment of vegetation 

treatments in the Interior Columbia Basin of the

Pacific Northwest (USDA Forest Service and USDI

BLM 2000). Based on this assessment, the proposed 

increase in the amount of prescribed burning 

conducted as a part of forest and rangeland 

management on Forest Service- and BLMadministered lands over the 100-year planning period 

would be expected to reduce the amount of wildfire

activity within the project area. In addition, the 

analysis revealed that wildfire impacts on air quality 

may be significantly greater in magnitude than 

emissions from prescribed burning. The lower 

emissions from prescribed fire are attributed to 

prescribed burning techniques that reduce emissions, 

as well as smoke management plans implemented by

federal, state, and tribal agencies that permit

prescribed fires only during meteorological periods 

favorable to dispersion. If the number of wildfires is 

reduced over time, air quality impacts from smoke

should also be reduced. 

Air quality modeling suggested that PM emissions from 

prescribed burning could cause regional-scale 

exceedances of the NAAQS based on the cumulative

impacts from all sources of air pollution on ambient air.

This modeling analysis also assumed that local analysis

would be done to assess the possibility of localized 

exceedances of the NAAQS caused by prescribed 

burning emissions. Local analysis would also be done

for activities conducted by the BLM under this PEIS. 

It can be assumed that state smoke management 

meteorologists would consider the cumulative effects of

emissions from other sources (such as road dust and

agricultural dust and burning) during the development 

of daily smoke management instructions, and that state 

smoke management program managers would consider 

these sources during development of the smoke 

management plan submitted for approval (as a 

component of the state smoke implementation plan) to 

the USEPA. 

The Forest Service modeled several scenarios to predict

the long-term effect of treating more acres, and/or

targeting treatments in the WUI, on regional air quality 

and the condition of the land (Hann et al. 2002). The 

model assumed that in addition to use of fire, 

mechanical and hand cutting would be important

treatment options in the WUI, where air quality and 

other considerations could limit the use of fire. Based on 

this analysis, air quality would generally improve as the

number of acres treated annually increased, with the 

most noticeable improvement in air quality associated 

with treatments targeted at high priority western U.S. 

WUI landscapes. Thus, the Preferred Alternative, which 

includes over 4.3 million acres of wildland and 

prescribed fire use and mechanical treatments, in

addition to 1.7 million acres of treatments using other 

BLM Vegetation Treatments Using Herbicides 4-203 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

methods, would be expected to provide greater 

improvement in ecosystem function and air quality than 

is projected under current treatment levels. 

The increased use of wildland fire use and prescribed

fire proposed by the BLM parallels national trends. The 

National Wildfire Coordinating Group Fire Use 

Working Team sanctioned an interdisciplinary and

interagency working framework for coordinating

development of modeling and data systems to support 

balancing the increased use of prescribed fire in the

context of reducing the local and regional impacts of

fires on air quality (Sandberg et al. 1999; USDA Forest

Service and USDI BLM 2000). A number of modeling

and data system enhancements are currently under 

development by the Joint Fire Sciences Program of the

USDA Forest Service and the USDI. These systems 

include the modeling of meteorological conditions and

smoke dispersion. The Forest Service and BLM also

have developed a data system to support prescribed

burning and to assist states with emissions tracking

under their respective state smoke management plans. 

The use of more sophisticated models during the 

implementation of prescribed burning, together with 

enhanced monitoring of emissions, will help minimize

possible impacts from the use of prescribed fire. The 

inherent limitations of any model used at the 

programmatic scale highlight the importance of the 

cooperative development and use of operational smoke 

management models by the states, with assistance from

the BLM, Forest Service, and the USEPA. 

Most emissions on public lands in Alaska are associated 

with wildfire and wildland fire use, and oil and gas 

exploration and development on the North Slope in the

National Petroleum Reserve – Alaska (USDI BLM

2005c). Long term, fire emissions would likely remain

near current levels. Emissions on the North Slope are 

expected to decrease as a result of an overall downward 

trend in oil production; therefore, any possible 

contribution from local sources to air quality and Arctic

haze would be reduced. Greater reliance on 

technologies that reduce the need for permanent roads 

and pads, and reduce the size of facility footprints, 

would also result in lower levels of PM emissions. 

Arctic haze has the potential to increase as Asian 

economies grow. Until air pollution concentrations in

Asia and Europe begin to decline, Arctic haze is likely 

to persist or get worse. 

Contribution of Alternatives to Cumulative 

Effects 

As discussed under Air Quality in Chapter 4 of the PER, 

the majority of emissions would be associated with 

wildland fire use, and prescribed fire, and to a lesser 

extent, with mechanical treatments. Manual and 

biological control methods and herbicide treatments 

would contribute only small amounts of pollutants to

the air. These emissions would accumulate and the 

amount of emissions released into the environment

would be related to the number of acres treated and the 

type of treatment. Exceedances of NAAQS, however,

should not occur under any alternative, and under all

alternatives vegetation treatments would account for 

less than 1% of pollutants generated nationwide. 

As discussed in Chapter 2 under Determination of 

Treatment Acreages, approximately 645,000 acres 

would be treated using wildland fire use and prescribed 

fire and 582,000 acres would be treated using 

mechanical methods under Alternative A (No Action

Alternative). Approximately 2,107,000 acres would be 

treated using fire and 2,232,000 acres would be treated 

using mechanical methods under the Preferred

Alternative. Under alternatives C, D, and E, 

approximately 1,055,000 acres would be treated using

fire, 1,986,000 acres would be treated using mechanical

methods, 396,000 acres would be treated using manual

methods, and 597,000 acres would be treated using 

biological control. 

The Annual Emissions Inventory for BLM Vegetation

Treatment Methods (ENSR 2005; included on the CD 

that accompanies the Final PEIS) found that annual

emissions associated with prescribed fire and

mechanical treatments for Alternative A were about 

40% and 25% of those predicted to occur under the 

Preferred Alternative. Annual emissions for fire and

mechanical treatment methods under Alternatives C, D,

and E would be about 50% and 10% less, respectively, 

than those under the Preferred Alternative. Higher 

levels of fire treatments associated with the Preferred 

Alternative would increase smoke emissions and

regional haze, although some of these impacts could be

reduced by following proper smoke management

procedures identified earlier in this chapter. 

Although air emissions associated with vegetation

treatments would be less under Alternatives A, C, D,

and E than under the Preferred Alternative, gains in

long-term air quality improvement are projected to be

greater under the Preferred Alternative than under other 

alternatives, since more acres with hazardous fuels, 

BLM Vegetation Treatments Using Herbicides 4-204 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

dense forest cover, and invasive vegetation that

contribute to wildfire would be treated under the 

Preferred Alternative than other alternatives. 

The cumulative effects of all projects affecting the 

North Slope of Alaska in the past generally have caused

little deterioration in air quality, which remains better 

than what is required by national standards. The amount

of air pollutants generated should remain near current 

levels, and approximately 50% lower than emission

levels in the late 1980s (USDI BLM 2005c). 

Improvements in air pollution control technology would 

also help to reduce emissions from current levels. 

Soil Resources 

Past Effects and Their Accumulation 

Cumulative impacts to soils on public lands and

throughout the western U.S. have occurred from

human-caused disturbance factors, including natural 

resource extraction, grazing, road construction, timber 

harvesting, OHV and other recreation use, agriculture, 

and development, as well as natural disturbances. More 

recently, large-scale, uncharacteristic wildfires have

increased the number of landscapes with declining soil

productivity by causing a reduction in effective 

vegetative ground cover and a loss of root strength, 

which has resulted in increased soil erosion rates 

(USDA Forest Service and USDI BLM 2000). Soils in

the western U.S. are generally stable in wilderness 

areas, but in other locations soils are at varying levels of 

decreasing productivity depending on soil types and

intensity of management. Determining the exact soil

conditions in any given area is difficult because of the

lack of inventory and monitoring data. In general,

greater declines in soil productivity are directly

associated with greater loss of soil through erosion and

displacement, loss of soil organic matter, changes in

vegetation composition, removal of whole trees and 

branches, and increases in bulk density from compaction. 

Soil productivity may currently be higher in areas where 

fire has been suppressed and where organic matter and

vegetation have not been removed. However, the 

unnaturally high amounts of vegetation and large 

woody material put these areas at risk for 

uncharacteristic fire intensity and severity, which can

lead to decreased soil productivity because of high rates 

of erosion, loss of organic matter, woody material, and

nutrient reservoirs. 

In Alaska, non-oil and gas activities associated with 

villages, towns, and military sites have disturbed soils 

on public lands. Since the 1970s, oil and gas exploration 

and development have been the dominant soildisturbing activities associated with public, other

federal, state, tribal, and private lands on the North

Slope. On the North Slope, direct impacts to soil and 

soil productivity persist on over 12,000 acres (USDI 

BLM 2005c). Another 18,000 acres of indirect impacts 

have occurred, some of which persist today. 

Future Effects and Their Accumulation 

As discussed earlier in this chapter, vegetation 

treatments could occur on 6 million acres. Loss of 

vegetation and soil disturbance associated with use of 

treatment equipment could cause some short-term loss 

of soil functions, process, and productivity on nearly all

treated land. However, it is assumed that watershedlevel restoration treatments designed and implemented 

by the BLM and other federal agencies with large 

landholdings in the West would achieve long-term 

effects similar to those occurring under historical

disturbance regimes (USDA Forest Service and USDI

BLM 2000). The disturbance effects resulting from 

restoration activities are predicted to have less impact

and be less severe than fire effects and erosion caused 

by past fire exclusion and traditional management

activities. Monitoring and evaluation, integrated with 

adaptive management and sustainable use practices,

would result in adjustments to treatment design and

implementation and restoration actions in order to 

reduce soil disturbance to levels similar to historic

conditions. 

Studies in forested and rangeland environments have 

suggested that landscapes that contain native plant

communities in natural mosaic patterns and have

relatively uninterrupted natural disturbance regimes 

provide favorable conditions for soil functions and 

processes that contribute to long-term sustainability of 

soil productivity (Munn et al. 1978, Cannon and Nielsen 

1984, and Hole and Nielsen 1970 cited in USDA Forest

Service and USDI BLM 2000). In addition, a reduction 

in the spread of exotic and invasive vegetation is 

expected to help maintain soil productivity and 

function. Forests and rangelands with conditions outside 

the historical range of vegetation variability are most

vulnerable to accelerated nutrient loss from

management activities or wildfire. 

In recent years, a number of policies, programs, and

initiatives have been proposed to restore soil

productivity and improve the health of ecosystems by

BLM Vegetation Treatments Using Herbicides 4-205 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

the BLM and other federal, state, and local land

management entities to meet nationwide and regionwide 

conservation goals. These include the National Fire 

Plan, Healthy Forests Restoration Initiative, this PEIS, 

the Interior Columbia Basin Ecosystem Management

Project, the Great Basin Restoration and Conservation

of Prairie Grasslands initiatives, the sage-grouse 

conservation program, and the program to treat invasive 

vegetation on Forest Service lands in the Pacific 

Northwest (USDA Forest Service and USDI BLM

2000, USDA Forest Service 2005, USDI BLM 2006c). 

The success of these policies and programs to restore 

healthy ecosystems will depend in part on future 

funding levels, and on our understanding of soil 

processes and our ability to develop and implement 

vegetation management projects that are effective and

lead to long-term improvement in soil and other 

ecosystem resources. Much of the focus of these efforts 

is on reducing hazardous fuels and wildfire activity in 

the West. In addition, conservation programs and best

management practices to reduce soil loss in agricultural

areas have been developed and implemented during the

past several decades. Although gains in soil productivity

have been slow, improvement has been observed. 

Changes in disturbance regimes, such as changes 

resulting from fire suppression, introduction of nonnative plant species, timber management practices,

human populations and related activity, minerals 

extraction, and livestock grazing over the past 100

years, have caused a departure from the historical

ranges of vegetation composition and structure and

landscape mosaic patterns. Still, in a study of the

Interior Columbia Basin, soil disturbance on

approximately 92% of federally-administered lands was 

rated as none to low. Nationwide, the estimated average

annual loss of soil due to erosion associated with 

rainfall and wind on non-federal lands has decreased by 

about a third from levels in the early 1980s; similar 

trends have been seen in the western states (National 

Resources Conservation Service 2000). These data 

suggest a need for improvement in soil productivity and 

rangeland conditions throughout the West, but also 

suggest that long-term improvement in soil productivity 

in the West can occur under careful stewardship of 

lands. 

Contribution of Alternatives to Cumulative 

Effects 

Based on the number of acres treated, short-term 

impacts to soil function and productivity would be 

greatest under the Preferred Alternative (approximately

6 million acres for all treatments), and least under the 

No Action Alternative (1.9 million acres). The number

of acres treated under Alternatives D and E (about 4.5

million acres each) would be similar, and short- and

long-term effects under these two alternatives would be 

similar, while the effects under Alternative C (4 million 

acres) would be intermediate between those under these 

alternatives and the Preferred Alternative. Treatments

would occur on about 2% of public lands annually

under the Preferred Alternative. 

During FY 2005, the BLM applied approximately 0.9

pounds of herbicide per acre treated. Based on this ratio, 

the BLM would apply about 840,000 pounds of 

herbicides annually under the Preferred Alternative, 

about half this much under Alternatives D and E, and 

about a third as much under Alternative A. Although the

BLM would contribute only about 0.1% of the amount

of pesticides applied annually in the western U.S., these 

herbicides would accumulate in the soil at a greater rate

than presently occurs. Most herbicides that would be

applied by the BLM have a soil half-life of 60 days or

less, although the soil half-life for diquat is about 1,000

days. 

Alternative E places greater emphasis on passive

restoration than the other alternatives. Poorly planned or 

managed livestock grazing, forestry practices, minerals

development, and OHV use are just some of the 

activities that can lead to loss of soil productivity and 

cause soil erosion. The BLM would also use passive 

restoration to improve soil conditions, but would have 

to balance soil protection and improvement with the 

multiple use requirements under FLPMA. As discussed 

in Chapter 2, Vegetation Treatment Programs, Policies, 

and Methods, passive restoration would be considered

first when developing restoration management plans, 

and would be used to the extent possible within the

constraints of FLPMA. 

Short-term effects to soils could accumulate under all 

alternatives, but if treatments were successful, a 

countervailing effect of long-term improvement in soil

function and productivity should more than offset shortterm soil losses. Largest improvements are expected for 

the Preferred Alternative and Alternatives D and E. 

Water Resources and Quality 

Watersheds are natural divisions of the landscape and

the basic functioning units of hydrologic systems. The 

BLM conducts monitoring of watersheds on public 

lands and bases the success of its treatments on the 

condition of watersheds and their subbasins (USDI 

BLM 2006c). Stream flow regimes and water quality 

BLM Vegetation Treatments Using Herbicides 4-206 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

can be affected by modifications to watershed processes 

occurring as a result of both natural disturbances and

land management activities. Water quality and quantity,

which are key components of wetland and riparian

habitat, can also have substantial influence over the 

health of fish and other aquatic organisms. They are 

components over which the BLM has some degree of 

influence on public lands (USDA Forest Service and

USDI BLM 2000). 

Section 303(d) of the Clean Water Act requires that

water bodies violating state water quality standards and 

failing to protect beneficial uses be identified and placed 

on a 303(d) list. The delisting of 303(d) listed streams is

a priority of the BLM. Nonpoint source pollution, which 

is the largest source of water quality problems on public

lands, comes from diffuse or scattered sources rather 

than from an outlet, such as a pipe, that constitutes a

point source. Sediment is a nonpoint source of pollution

that results from activities such as grazing and timber

harvest, and from erosion associated with wildfires and

the spread of noxious weeds. Erosion and delivery of 

eroded soil to streams is the primary nonpoint source 

pollution problem of concern to the BLM. 

Past Effects and Their Accumulation 

Problems associated with water quality in the western 

U.S. were first recognized in the 19th century when

mining in California was polluting the water so greatly

that crops could not be grown. Exploration and 

development of oil resources later contributed to water 

quality concerns, especially in California, Oklahoma, 

and Texas. New sources of pollution arose in the 20th

century, including pollutants associated with agriculture

(e.g., fertilizers, pesticides, and animals wastes), 

industry, and other human activities (e.g., sewage, 

household cleaning products, pollutants associated with

automobiles). In 1999, the USEPA released its first ever 

national index on the quality of the nation’s watersheds. 

The USEPA also conducted an assessment of general

groundwater quality (based on concentration of TDS). 

Based on these assessments, 21% of the watersheds 

have serious problems. In watersheds in the West, water 

quality is poor to moderate over many areas (based on

concentration of TDS for groundwater), primarily in

areas associated with agricultural activities. Thus, 

actions that further deteriorate water quality or

watershed health must be carefully evaluated before 

being implemented on public lands (Wright 2002). 

Minor cumulative effects to water resources have

occurred on public lands in Alaska. Cumulative effects 

to water resources from oil and gas exploration, gold 

placer mining, and other development have included: 1) 

disturbance of stream banks and beds or lake shorelines;

2) melting of permafrost (thermokarst erosion); 3)

temporary blockages of natural channels and floodways 

during construction of roads and pipelines that have

resulted in the disruption of drainage patterns; 4) 

increased erosion and sedimentation in rivers and lakes;

5) removal of water from lakes for ice roads and pads; 

6) spills; 7) removal of gravel from riverine pools and

lakes; and 8) extensive erosion of off-road trails (USDI 

BLM 2005c). 

The Clean Water Act of 1972 was intended to solve

many of the nation’s water pollution problems, but has 

had only modest success. In 1972, a third of the nation’s 

rivers were safe for fishing and swimming. That number 

improved to more than 50% in the 1980s, but began to

fall in the 1990s. The primary cause for deteriorating 

conditions in the 1990s was agricultural and municipal

wastes rather than industrial wastes. (The standard for 

classifying deteriorating conditions has also changed 

over that time.) An estimated 14.1 million Americans 

drink water that contains agricultural pesticides in

amounts that would exceed the acceptable

concentrations for food products (Wright 2002). 

Past land management activities on private and public 

lands in the western U.S. have contributed to 

deterioration in water quality. The spread of invasive

plant species is one factor that degrades hydrologic 

function. In addition, buildup of hazardous fuels can

lead to wildfires that adversely impact water resources 

and quality. Changes in hydrologic function have

occurred as a result of changes in flow regimes due to 

dams, diversions, and surface water and groundwater 

withdrawal; and as a result of changes in channel 

geometry due to sedimentation and erosion, 

channelization, and installation of roads and railroads. 

Large amounts of wetland and riparian habitat, which

function to cleanse water and recharge groundwater 

aquifers, have been lost in the West due to agriculture 

and urbanization. Over 109 million pounds of pesticides 

are applied annually in the western U.S.; these

chemicals affect water quality. 

During the early years of the BLM, most resource

conservation and management was focused on upland 

sites. An increased emphasis on wetland and riparian 

habitat protection began in the 1960s with the passage 

of the Water Resources Research Act and Water 

Resource Planning Act (1965), which allowed the BLM 

to increase watershed research and planning. Much of 

the early work consisted of identifying lands in the 

critical stages of erosion (Muhn and Stewart 1988). In

BLM Vegetation Treatments Using Herbicides 4-207 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

the 1970s, FLPMA was passed (1976) and the BLM 

began preparing land use plans to better manage natural

resources. 

Future Effects and Their Accumulation 

Despite spending nearly $1 trillion to improve water 

quality since the enactment of the 1972 Clean Water 

Act, the United States has no adequate database for 

water quality. Water quality monitoring is done by state

and federal agencies, local governments, tribes, and

others, among which there is wide variance in the extent

and types of monitoring (Hayward 2005). Additionally, 

the nature of the resource presents challenges because

the effects of both natural and man-made contaminants 

vary greatly according to specific water conditions.

Researchers must account for water source, velocity, 

volume, depth, pH, photosynthetic activity, seasonal

variations, and even time of day to accurately measure

water quality. Thus, predicting the extent and magnitude 

of future effects to water resources and quality is 

difficult. 

In its 2001 Annual Performance Plan (USDI BLM 

2000e), the BLM committed to 1) implementing water 

quality improvement prescriptions on public lands in 

20% of watersheds within priority sub-basins that do 

not meet state/tribal water quality standards; 2) 

achieving proper functioning condition or an upward 

trend in wetland/riparian areas in 80% of priority

watersheds by cooperating with the Forest Service and

other land management agencies to restore degraded

wetland and riparian areas; and 3) achieving an upward

trend in the condition of uplands within 50% of priority

watersheds by reducing the spread of weeds and 

reintroducing fire into specific landscapes. Generally, 

high priority watersheds are those that have impaired

water bodies. 

According to an Office of Management and Budget 

Program Assessment Rating Tool, in 2005 the BLM had

met or was making measurable progress toward meeting

its goals. The OMB assessment noted that the BLM was 

challenged by the need to meet multiple land use 

objectives, such as allowing oil and gas development

that may conflict with restoration objectives (Office of

Management and Budget 2005). 

Based on information provided by field offices, the 

BLM would treat about 300,000 acres to improve 

watershed, and another 30,000 acres to improve wetland

and riparian area functions and values. These types of 

treatments are not proposed for Alaska. Efforts to

restore natural disturbance regimes, reduce the potential

for large-scale wildland fire, and manage and control 

noxious weeds and other invasive vegetation would 

help to reduce erosion and sedimentation and restore 

native plant communities. In addition, the ability of the 

BLM and other resource-protection entities to use new 

herbicides, such as fluridone and imazapic, to control

weeds would benefit public lands with minimal risk to 

drinking water, human health, and fish and wildlife. 

Gravel mining, construction of roads, permanent drill

pads, and water use from lakes during the winter 

months would be the major contributors to water 

resource impacts in Arctic Alaska. Impacts from

activities such as gold mines in placer gravels,

deteriorated OHV trails, and fires and fire control are

the major contributors in the rest of the state. Because of 

the abundance of water resources in Alaska, the overall

cumulative impact to water resources on public lands in 

Alaska would probably be small in magnitude, and most

effects would be local in nature. 

Contribution of Alternatives to Cumulative 

Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to 

hydrologic function and water quality would be greatest 

under the Preferred Alternative (approximately 6

million acres for all treatments), and least under the No

Action Alternative (1.9 million acres). The number of

acres treated under Alternatives D and E (about 4.5

million acres each) would be similar, and short- and

long-term effects under these two alternatives would be 

similar, while the effects under Alternative C (4 million 

acres) would be intermediate between those under these 

alternatives and the Preferred Alternative. In addition,

approximately twice as many acres would be treated 

using prescribed and wildland fire under the Preferred

Alternative (2.2 million acres) than under alternatives C, 

D, and E (1.06 million acres), and three times as many

as compared to the No Action Alternative (645,000 

acres). It is anticipated that use of fire and herbicides 

would have the greatest short-term impact on water 

quality and quantity and watershed conditions. Adverse

effects to water quality from wildfire and spread 

invasive species would accumulate in the West, but if

BLM and other public and private vegetation treatment

efforts were successful, a countervailing effect of longterm improvement in water resources and quality should

help than slow losses. Improvements in water resources

and quality should be greatest for the Preferred

Alternative and Alternatives D and E. 

BLM Vegetation Treatments Using Herbicides 4-208 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Based on recent herbicide use, the BLM would apply 

about 652,000 pounds of herbicides annually under the 

Preferred Alternative, about half this much under 

Alternatives D and E, and about a third as much under 

Alternative A. This would amount to about 0.6% of the

amount of pesticides applied annually in the western

U.S. based on the Preferred Alternative. An increase in 

use of herbicides, regardless of source, would contribute 

to loss of water quality both on and off public lands, as 

these herbicides have the potential to move off site in

surface water or groundwater. The movement of

herbicides off public lands could contaminate public 

drinking water sources and water sources used by fish

and wildlife. However, the use of newer herbicides by 

the BLM that pose fewer risks to humans and fish and 

wildlife, and strict adherence to buffer guidelines given 

in the PEIS, PER, ERAs, and HHRA during treatments 

to protect water resources, should mitigate for some of

the loss in water quality. Alternative E places greater 

emphasis on passive restoration than the other 

alternatives. Passive restoration is often an important

first step in improving watershed health because the 

anthropogenic activities that are causing degradation or

preventing recovery are reduced or eliminated.

Livestock grazing and OHV use are often cited as 

factors that lead to loss of wetland and riparian habitat 

function and watershed degradation. By prohibiting 

livestock from entering wetland and riparian areas, and

placing limits on OHV activity, improvement in

watershed function can be expected (Kauffman et al. 

1997). Improvements in the management of these 

activities can also reduce potential impacts to wetland 

and riparian areas, and the BLM would have to balance 

watershed protection with the multiple use requirements 

under FLPMA. As discussed in Chapter 2, Vegetation 

Treatment Programs, Policies, and Methods, passive 

restoration would be considered first when developing

restoration management plans, and would be used to the

extent possible within the constraints of FLPMA. 

Regardless of the alternative chosen, there would be an

accumulation of loss of water resources and quality 

under all alternatives, but the rate of loss would be 

expected to slow from historic levels over the long term. 

Wetland and Riparian Areas 

Under natural conditions, wetland and riparian plant 

communities have a high degree of structural and 

species diversity, reflecting past disturbances from 

floods, fire, and fish and wildlife use (Gregory et al.

1991). Since European settlement, many wetland and

riparian areas have been drained or altered and their 

functions and values lost or reduced. The Clean Water 

Act (1972) and Executive Order 11990, Protection of 

Wetlands and Floodplains (1977), identified the 

importance of wetland and riparian areas and directed 

federal and state agencies to focus more attention on the

health of these areas. As a result of legislative and

policy guidance, the BLM and other land management 

entities have spent considerable effort and money to 

restore wetland and riparian functions and values during

the past several decades. 

Past Effects and Their Accumulation 

Cumulative impacts to wetland and riparian areas on

public lands and throughout the western U.S. have 

occurred from human-caused disturbance factors, 

including natural resource extraction, recreation, dams

and diversions, road construction, agriculture, 

urbanization, and fire exclusion. An estimated 53% of 

wetlands present at the time of colonization in the lower 

48 states have been lost in the U.S., but less than 0.1%

have been lost in Alaska. The USFWS estimates that

about 117,000 acres of wetlands were lost annually 

between 1985 and 1995 (Wright 2002), while the 

USEPA has estimated wetland losses on non-federal

rural lands at approximately 70,000 to 90,000 acres 

annually (Washington State Department of Ecology 

2005). 

Today, the BLM’s annual budget for wetland and 

riparian management is nearly $22 million (USDI BLM

2006b). Program priorities include identifying priority 

watersheds on which to focus restoration efforts, with

special emphasis on watersheds that contain habitat for 

sage-grouse. The BLM spent an additional $13 million

in FY04 assessing the condition of watersheds and 

conducting restoration efforts in areas that are less than

properly functioning (USDI BLM 2006c). 

Even with these efforts, 25% of wetlands surveyed on 

public lands in the lower 48 states are not functioning

properly or are functioning at risk (USDI BLM 2006c), 

while 50% of riparian areas are non-functional, or are 

functioning at risk. The poorest functioning riparian 

areas are found in the southwest and Montana, while 

most riparian areas in Alaska, Colorado, and Utah 

function properly. High sediment and turbidity levels

and high temperatures are the primary reasons for 

listing wetlands and riparian areas as not functioning 

properly (USDA Forest Service and USDI BLM 2000;

USDI BLM 2006b). In addition to water quality and

flow concerns, many wetlands and streams have lost the

capability to support salmonids and other aquatic

organisms. 

BLM Vegetation Treatments Using Herbicides 4-209 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

The spread of invasive plant species is one factor that

degrades wetland and riparian function. In addition, 

hazardous fuels buildup can lead to catastrophic

wildfires that adversely impact wetland and stream

habitat. Within riparian woodlands, the abundance of 

mid-size trees has increased while the abundance of

trees in other size categories has decreased, primarily

due to fire exclusion, increasing the risk of wildfire and

reducing the value of these habitats to fish and wildlife. 

Within riparian shrublands, there has been extensive

conversion to riparian herblands and increases in exotic 

grasses and forbs, primarily because of processes and

activities associated with excessive livestock grazing. 

This conversion has made these shrublands more 

susceptible to fire and reduced their value to fish and

wildlife (USDA Forest Service and USDI BLM 2000). 

Future Effects and Their Accumulation 

The rate of loss of wetland and riparian habitat in the

West has slowed, and on public lands there has been

some improvement in the functional quality of these 

areas. For example, the percentage of wetland and 

riparian areas in the lower 48 states that lack the 

characteristics necessary for high function has decreased

by about 10% since 1996 (USDI BLM 1997, USDI 

BLM 2006d). Vegetation treatment programs proposed

by the BLM and Forest Service, and similar efforts by

other agencies, private landowners, and private entities 

(e.g., Ducks Unlimited, The Nature Conservancy) to

protect and preserve wetland and riparian habitat, 

should restore wetland and riparian habitat and health 

over the long term. In the Interior Columbia Basin, 

proposed treatment efforts could improve aquatic 

habitat capacity by 50% over 100 years (USDA Forest

Service and USDI BLM 2000). 

Efforts to restore natural disturbance regimes, reduce 

the potential for large-scale wildland fire, and control

noxious weeds and other invasive vegetation should

help to reduce erosion and sedimentation and restore 

native plant communities. In addition, the ability of the 

BLM and other resource-protection entities to use new 

herbicides, such as fluridone, to control aquatic weeds 

would benefit lakes and ponds and the aquatic 

organisms that use these habitats. In Alaska, early 

detection and control of weeds would be effective in

protecting wetland and riparian habitat, as the state does 

not yet face a severe weed problem as in the lower 48

states (Hebert 2001). 

Contribution of Alternatives to Cumulative 

Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to 

wetland and riparian area function and productivity 

would be greatest under the Preferred Alternative, and

least under the No Action Alternative. The number of

acres treated, and short- and long-term impacts, under 

alternatives D and E would be similar, while Alternative 

C would be intermediate between these alternatives and

the Preferred Alternative. Treatments would occur on 

about 10,000 and 2,300 acres of wetland and riparian

habitat annually under the Preferred Alternative under 

the No Action Alternative, respectively. Short-term 

effects could accumulate, but if treatments were

successful, a countervailing effect of long-term

improvement in wetland and riparian area function and

productivity should more than offset short-term losses. 

Herbicide treatments would not be allowed under 

Alternative C. Therefore, control of some aquatic

weeds, including giant salvinia, water-thyme, and

Eurasian watermilfoil could be difficult, as mechanical

and other treatment methods would be less effective. 

Under alternatives C and D, it could be difficult for the 

BLM to adequately treat weed infestations in remote

areas and large weed infestations to benefit aquatic 

organisms. Thus, the risk of loss of aquatic habitat and 

habitat function in more remote areas could be greater 

under these alternatives than under the Preferred

Alternative. 

Alternative E places greater emphasis on passive

restoration than the other alternatives. Passive 

restoration is often a critical first step in successful

riparian or wetland area restoration because the 

anthropogenic activities that are causing degradation or

preventing recovery are reduced or eliminated.

Livestock grazing is often cited as a factor that causes 

loss of wetland and riparian habitat function; by 

prohibiting livestock from entering these areas, 

improvement in habitat function can be expected

(Kauffman et al. 1997). However, the BLM must

balance wetland and riparian habitat protection with the 

multiple use requirements under FLPMA. Therefore,

the BLM modifies the timing and duration of grazing to 

reduce potential impacts, rather than implementing total

exclusion, whenever possible. As discussed in Chapter 

2, Vegetation Treatment Programs, Policies, and

Methods, passive restoration would be considered first

when developing restoration management plans, and 

would be used to the extent possible within the 

constraints of FLPMA. 

BLM Vegetation Treatments Using Herbicides 4-210 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Regardless of the alternative chosen, there would be an

accumulation of loss of wetland and riparian functions 

and values under all alternatives over the short term, but

the rate of loss would be expected to slow from historic 

levels, over the long term, if the BLM was successful in

improving wetland and riparian habitat functions and

values. 

Vegetation 

Historically, ecosystems on public lands were 

comprised of a mosaic of vegetation types adapted to

natural disturbances, including climate, fire, flood, and 

geological events. They were dynamic and resilient, 

tending to return to some developmental pathway when

disturbed or changed. However, ecosystems have 

biological or physical limits that, if exceeded as a result

of natural or human causes, can lead to deterioration in 

ecosystem health. If these limits are exceeded for 

extended periods of time, the characteristics of the

ecosystem can change, often substantially, to the

detriment of the ecosystem. 

Past Effects and Their Accumulation 

North America has been occupied by Native peoples for 

at least 12,000 years (USDI BLM 2005c). Contrary to

the beliefs of European emigrants arriving in the 

western U.S. in the 18th century, western lands at that

time were not pristine wilderness but ecological systems 

in which humans were an active component. American 

Indians used fire as a tool to manage vegetation. As 

Euroamericans moved west, they reshaped ecosystems 

to meet their needs. They cleared forests for agriculture 

and grazed livestock, fragmenting landscapes and

changing plant and animal species composition. As 

people settled areas, they built homes and other 

structures, and began suppressing fires to protect their 

property. The resultant fire exclusion promoted aging

forests and shrublands, insect and disease outbreaks, an

overaccumulation of fuel, and a consequent increase in

fire severity and intensity. The disruption of natural fire

cycles in fire-adapted ecosystems became the dominant

agent of change that initiated an increased wildland fire

risk (Hann et al. 2002). 

Most rangelands have experienced significant changes

in fire regimes during the past 150 years. Removal of 

the use of fire by native Americans would have 

significantly changed fire regimes for many rangelands. 

Some rangelands have experienced reductions in 

herbaceous cover and increased dominance of woody 

species, resulting in a lengthening of the fire return

interval. Other rangelands have shorter fire return

intervals, primarily as a result of wildland fire

disturbances that created conditions favorable for exotic 

species’ invasions. 

Previously, wildland fire had maintained grasslands by

rejuvenating decadent grasses and killing young woody

species that might have seeded between fire

occurrences. Although woody species would have 

increased based on reductions in the frequency of fires 

alone, other factors also contributed to these changes. 

During the late 19th and early 20th centuries, decreases 

in grass cover caused by overgrazing by livestock

provided open sites that promoted more rapid

establishment of woody species. As woody species 

increased, they competed for soil nutrients and 

moisture, which inhibited recovery and production of 

herbaceous cover. Because combustible vegetation 

became patchier, fire frequency continued to decrease 

on these sites. 

Later in the 20th century, organized fire suppression 

further contributed to the invasion of grasslands by 

woody species and the increased density of woodlands 

and shrublands. Some rangeland sites lost much of their 

herbaceous ground cover. On some sites, this loss of

ground cover resulted in increased wind and water 

erosion. Erosion further reduced herbaceous cover, 

perpetuating the cycle of degradation. During the 20th

century, many of these rangelands also provided 

suitable sites for non-native species establishment. 

Invasive herbaceous non-native species affect rangeland

fire regimes much differently than invasive woody 

species. Many non-native annual plant species dry out

earlier than native perennials, prompting a longer 

annual flammable period. The longer flammable season, 

coupled with denser ground cover typical of these nonnative species, triggers much more frequent fire. In

many cases, each time a fire occurs, additional

opportunities for the establishment of non-native 

species are created. The result is a cycle of ecosystem

degradation and costly, unwanted wildland fires. 

Fire exclusion and historical logging practices altered

forest structure, species composition, and associated fire

regimes, particularly in forest types with high frequency

fire regimes. Fire suppression efforts began influencing 

forest structure and composition more than 100 years 

ago. In the absence of fire, understory trees became

much denser in dry forest types. In these areas,

understories shifted to species that were more shadetolerant and less resistant to fire and drought cycles. As 

these forests aged, resistance further declined and they 

became increasingly susceptible to insect and disease

outbreaks. As a result, wildland fires in these degraded 

BLM Vegetation Treatments Using Herbicides 4-211 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

forests burned more severely and became more difficult 

to control. 

Natural reseeding and well-intentioned, aggressive 

planting programs also helped create dense stands of 

smaller trees and brush where forests of large trees had

once existed. Although mechanical thinning and slash

treatment programs were planned for many of these 

plantations, funding for these activities did not keep 

pace with the need to reduce stand density.

Today, forest structure on significant portions of federal

lands has shifted to a dominance of these small, more 

closely spaced trees. As these stands age, they become

susceptible to, and provide fuel for, intense wildland fire

(USDA Forest Service and USDI BLM 2000). 

In some forests and woodlands, logging, grazing, and

unnaturally severe fires have also contributed to 

increases in non-native plants, insects, and pathogens. 

The invasion of non-native plants has caused various 

impacts to ecosystems, including displacement and

endangerment of native species, reduced site 

productivity, and degraded water quality. 

Since the 1970s, the interior West’s population has 

increased more rapidly than the country at large. As

human populations continue to grow in the WUI, 

even more people and their property will be at risk

from unwanted wildland fires. The vegetation in many

of these interface areas, where wildland fire now poses

the greatest threat to human lives and values, evolved 

with fire. 

Actions taken by the BLM and other land management 

agencies to restore watersheds and ecosystem health by 

treating invasive vegetation and reducing hazardous 

fuels can reverse the trend of increasing risk of

unwanted wildland fire and deteriorating land health.

For example, in 1986, the BLM reported that only 34% 

of public land was in excellent or good condition

(Forest Service 1989). Today, approximately 42% of 

public land is considered to be in excellent or good

condition (USDI BLM 2006c). 

Future Effects and Their Accumulation 

Treatments that remove hazardous fuels from public 

lands would be expected to benefit the health of plant

communities in which natural fire cycles have been

altered. Treatments that restore and maintain fireadapted ecosystems, through the appropriate use of 

mechanical thinning, fire, and other vegetation

treatment methods, would decrease the effects of 

wildfire on plant communities and improve ecosystem

resilience and sustainability. Treatments should also 

reduce the incidence and severity of wildfires across the

western U.S. (USDA Forest Service and USDI BLM

2000). Treatments that control populations of nonnative species on public lands would be expected to

benefit native plant communities by reducing the 

importance of non-native species and aiding in the 

reestablishment of native species. 

Over half the treatments would occur in the Temperate

Desert Ecoregion. Much of this ecoregion is comprised

of grasslands and shrublands that have altered fire 

regimes, have suffered catastrophic fires during the past

decade, and are dominated by downy brome and other 

invasive species. Recovery to pre-fire conditions could

take decades to centuries. Treatments would improve

the mix of habitats so that vegetation would be more 

resilient to disturbance and sustainable over the long 

term. Treatments would reduce the encroachment and 

density of woody species in shrublands and/or 

herblands. Treatments would slow the spread of weeds 

and increase the number of acres dominated by

bunchgrasses and other important forage species for 

wildlife and livestock. As a result, plant communities 

that have declined substantially in geographic extent

from historical to current periods (e.g., big sagebrush

and bunchgrasses) would increase. Treatments would 

not be implemented in shrublands and other 

communities with the potential to become dominated by

downy brome. In situations where loss of native 

understory has occurred, such as in pinyon-juniper 

woodlands, and prescribed fire is desired to remove 

woody vegetation after mechanical treatments, analysis

should show that reseeding and possibly application of a 

selective herbicide can be effective to restore desired

native species. 

Given the current rate of urbanization and degradation 

of privately-owned lands and the limited funding

available to restore public and other publicly-owned

lands, the extent of weeds and other exotic and 

undesirable plants would continue to increase, but the 

rate of expansion would slow (USDA Forest Service 

and USDI BLM 2000). Based on modeling done for 

development of the cohesive strategy and assuming

vegetation treatment funding would remain near current 

levels, the cumulative number of acres of site 

degradation within 15 years from severe wildland fires 

and invasive plants would triple from current levels. 

However, even in that short time frame, risk to

watersheds would only increase by one-fifth under the 

proposed program (assuming equal weighting of 

BLM Vegetation Treatments Using Herbicides 4-212 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

treatments in the WUI and non-WUI), and would

remain static if more emphasis was given to restoring

natural fire regimes and healthy ecosystems in the nonWUI (67% of treatments in non-WUI; Hann et al. 

2002). Modeling done for treatments of BLM- and 

Forest Service-administered lands in the Interior 

Columbia Basin, which encompasses much of the

Pacific Northwest, showed that over a 100-year analysis 

period, there would be a decrease in vegetation types 

that are most susceptible to fire, insect, and disease

risks, and an increase in vegetation that is more resilient 

to these risks if treatments similar to those proposed in 

this PEIS were implemented (USDA Forest Service and

USDI BLM 1996). 

Contribution of Treatment Alternatives to

Cumulative Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to 

vegetation would be greatest under the Preferred

Alternative, and least under the No Action Alternative. 

The total number of acres treated, and the effects to

vegetation would be similar under Alternatives D and E. 

Effects to vegetation under Alternative C would be

intermediate between these alternatives and the

Preferred Alternative. 

It is anticipated that the use of wildland and prescribed 

fire and herbicides, and mechanical methods, would

have the greatest short term impacts on vegetation, and

that impacts would be somewhat in proportion to acres 

treated. Approximately three times as many acres would

be treated annually using herbicides under the Preferred

Alternative than under the No Action Alternative, and

about twice as many acres would be treated using

herbicides under the Preferred Alternative than under 

alternatives D and E. No acres would be treated using

herbicides under Alternative C. In addition,

approximately twice as many acres would be treated 

using prescribed and wildland fire under the Preferred

Alternative (2.2 million acres) than under alternatives C, 

D, and E (1.06 million acres), and three times as many

as compared to the No Action Alternative (645,000 

acres). Acres treated using mechanical methods would 

be similar among alternatives B, C, D, and E (about 2

million acres annually), and greater than for the No

Action Alternative (about 582,000 acres annually). 

Alternative E places greater emphasis on passive

restoration than the other alternatives. Passive 

restoration is often considered a critical first step in

successful restoration of degraded areas, since

anthropogenic activities that are causing degradation or

preventing recovery are halted. As discussed at the 

beginning of the cumulative effects section, passive 

restoration would be considered under all alternatives 

when developing restoration management plans, and 

would be used to the extent possible within the 

constraints of FLPMA. However, alternatives A through

D would likely take a more aggressive approach to

vegetation management than Alternative E. 

All alternatives include both passive and active

management. Recovery of vegetation through passive 

management is expected to take longer than under 

active management, where treatments such as seeding

with native species, establishing intermediate vegetation 

to control erosion, and use of pre-emergent herbicides to 

prevent weed establishment would be expected to

promote faster recovery. 

The use of ever greater amounts of herbicides and their 

repeated use may result in weed populations that

develop a resistance to a particular herbicide over time. 

This risk would be greatest under the Preferred

Alternative and least under Alternatives C and A. 

Herbicide resistant plants are present in a population in

extremely small numbers. The repeated use of one 

herbicide allows these few plants to survive and 

reproduce. The number of resistant plants then increases 

in the population until the herbicide no longer 

effectively controls the weed. To reduce this risk, the

BLM would 1) rotate herbicides, 2) apply these 

herbicides with the understanding that they can lead to 

weed resistance if used yearly for several consecutive 

years, 3) use mechanical and biological management

options to eliminate weed escapes that may represent

the resistant population, 4) use passive methods of weed

control to reduce or eliminate factors leading to the

spread of weeds, and 5) keep accurate records of

herbicide application. 

Regardless of the alternative chosen, there would be a 

cumulative loss of native vegetation function. Over the

long term, treatments should restore native vegetation

and natural fire regimes and benefit ecosystem health

and slow the loss of native vegetation function. The rate 

of loss under each alternative would be somewhat in 

proportion to the number of acres treated under each

alternative and the ability of the BLM to implement

passive restoration techniques to slow the spread of 

weeds. 

Fish and Other Aquatic Organisms 

Fish, the dominant aquatic vertebrate in the analysis

area, constitute a key component of aquatic systems on

BLM Vegetation Treatments Using Herbicides 4-213 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

public lands. Fish are a critical resource to humans and

as such have influenced the development, status, and 

success of social and economic systems in Alaska and 

the western U.S. Aquatic organisms such as insects and

other aquatic invertebrates provide food for fish. The 

health of fish and other aquatic organisms is often

indicative of the health of the watershed. Fish and other 

aquatic organisms are often more sensitive than humans 

and wildlife to herbicides and other chemicals in their 

environment, and thus can be an indicator of the 

concentrations of these pollutants in aquatic bodies. 

The BLM administers lands directly affecting almost 

155,000 miles of fish-bearing streams and 4 million

acres of reservoirs and natural lakes (USDI BLM

2006c). These habitats range from isolated desert

springs of the Southwest to large interior rivers and their 

numerous tributaries throughout the Pacific Northwest

and Alaska. Today, the rapid expansion of invasive 

species and buildup of hazardous fuels across public

lands are threats to ecosystem health and one of the

greatest challenges in ecosystem management. 

Past Effects and Their Accumulation 

Cumulative impacts to fish and other aquatic organisms

and the lakes, ponds, wetlands, and riparian areas that

provide habitat for aquatic organisms on public lands 

and throughout the western U.S. have occurred from

human-caused disturbance factors, including natural 

resource extraction, recreation, fire exclusion, 

construction of roads, dams, and hydropower facilities, 

agriculture, and urbanization. In addition to natural

disturbances, use of wetland and riparian areas by

livestock and wild horses and burros has degraded 

habitat values. Water withdrawal from ditches and

diversions have impacted fish habitat on public and 

other lands. Overfishing has been blamed for the 

declines in some fish populations (USDA Forest 

Service and USDI BLM 2000). The introduction of 

non-native game fish has also impacted some native fish

populations. 

The condition of much of the remaining habitat has

become degraded since that time. BLM surveys show 

that about 25% of wetlands and 50% of riparian habitat 

on public lands outside of Alaska lack characteristics 

necessary for “proper” functioning condition (USDI 

BLM 2006c). A proper functioning wetland or riparian

area has the necessary physical and structural

components to dissipate stream energy associated with

high water flows, as well as conditions that support a 

diverse and healthy population of fish and other aquatic 

organisms. 

The spread of invasive plant species is one factor that

degrades habitat for aquatic organisms. In addition, 

hazardous fuels can lead to large-scale wildfires that can 

adversely impact wetland and stream habitat. Within 

riparian woodlands, the abundance of mid-size trees has 

increased while the abundance of trees in other size 

categories has decreased, primarily due to fire 

exclusion, increasing the risk of wildfire and reducing 

the value of these areas to aquatic organisms. Within 

riparian shrublands, there has been extensive conversion

to areas dominated by exotic grasses and forbs, 

primarily because of processes and activities associated

with excessive livestock grazing pressure. This

conversion has made these areas more susceptible to

fire and reduced their value to aquatic organisms

(USDA Forest Service and USDI BLM 2000). 

Activities in Alaska, including oil and gas development 

and subsistence and recreational fishing, have impacted

fish and other aquatic organisms on public lands. These 

effects have accumulated, but do not appear to have

adversely affected fish populations to a great extent.

The permitting process and the regulatory environment

for protecting fish have improved over time and are 

generally effective. Proper construction and placement

of bridges and culverts have greatly reduced effects but

have not eliminated them. Little is known about the 

effects of water withdrawals from lakes on fish. Some

fish have been harmed or killed during water extraction, 

but these numbers have been small and have not

accumulated (USDI BLM 2005c). 

As discussed under Wetland and Riparian Areas, during 

the early years of the BLM, most resource conservation 

and management was focused on upland sites. An

increased emphasis on wetland and riparian habitat 

protection began in the 1960s. In the 1970s, FLPMA 

was passed (1976) and the BLM began preparing land

use plans to better manage natural resources on public 

lands. Land use plans set goals and objectives for 

natural resource management and identify priority

watersheds on which to focus restoration efforts, with

special emphasis on watersheds that contain habitat for 

sage-grouse. In addition, the BLM is assessing the 

condition of wetland and riparian areas, and conducting

restoration efforts in areas that are less than proper 

functioning. The BLM has restored about 160,000 acres 

of wetlands, and about 1,000 miles of stream habitat. 

Past control efforts by the BLM, other federal and state 

agencies, private landowners, and businesses 

(particularly the agricultural industry) have resulted in

the application of thousands of tons of herbicides and

other pesticides to the environment. As discussed

BLM Vegetation Treatments Using Herbicides 4-214 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

earlier, some of these herbicides break down relatively

quickly in the environment or are not harmful to aquatic

organisms at typical application rates. However, some 

herbicides are harmful to aquatic organisms, and may 

persist in the environment for many months. 

Future Effects and Their Accumulation 

The rate of loss of wetland and riparian areas has 

slowed with the passage of federal, state, and local

regulations that strive to protect wetland and riparian

habitat. There has been some improvement in the 

functional quality of wetland and riparian areas on 

public lands, a trend that is likely to continue. For 

example, the percentage of wetland and riparian areas 

that lack the characteristics necessary for high function 

has decreased by about 10% since 1996 (USDI BLM

1997, USDI BLM 2006d). As a result, the loss of

riparian and wetland functions and values over portions 

of the West should slow in the future. 

Efforts to restore natural disturbance regimes, reduce 

the potential for large-scale wildland fire, and manage 

and control noxious weeds and other invasive 

vegetation would help to reduce erosion and 

sedimentation and restore native plant communities. 

Restoration of native vegetation should improve 

riparian habitat and moderate stream temperatures and

water flows. In addition, the ability of the BLM and 

other natural resource management agencies to use 

aquatic herbicides to control aquatic weeds would

benefit lakes and ponds and the aquatic organisms that 

use these habitats. 

Modeling done for the Interior Columbia Basin

assessment predicted that vegetation treatments

proposed by the BLM and Forest Service would

improve the habitat capacity for fish and other aquatic

organisms, including threatened and endangered

salmon, but that fish populations might be slow to

respond to improved habitat conditions. Fish inhabit

streams found on and off public lands, and streams

cross multiple jurisdictions, including private land, 

along their entire course. In many cases the condition of 

the stream habitat off of public lands and on private or

other jurisdiction lands is unknown and could be of

lower quality. A portion of most fish populations is 

harvested each year. Competition with non-native fish

may limit the ability of native species to access or fully 

utilize available habitat. Perhaps most importantly, 

dams and other diversions found in the Columbia River, 

Colorado River, and most other major rivers in the West

also limit access to upriver habitats and alter occupied 

habitats for certain anadromous fish and other species. 

Thus, restoration of native vegetation and natural

ecosystems may be most immediately beneficial to 

resident fish rather than migratory fish that may travel

off of public lands to meet part of their life requisites 

(USDA Forest Service and USDI BLM 2000). 

Most water-related impacts to fish resources on public 

lands in Alaska would be associated with oil and gas

development, mining, and other development.

Development would include an increased number of ice 

roads and new pipelines, spills of hazardous materials,

and habitat disturbance. Potential impacts to fish would

be related to water withdrawal and direct habitat loss or

indirect disturbance associated with construction of 

facilities. 

Contribution of Alternatives to Cumulative 

Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to the 

health and productivity of aquatic organisms would be

greatest under the Preferred Alternative, and least under 

the No Action Alternative. The number of acres treated 

under alternatives D and E and their associated shortand long-term effects would be similar, while 

Alternative C would be intermediate between these

alternatives and the Preferred Alternative. Treatments

would occur on about 10,000 acres of wetland and

riparian habitat annually under the Preferred

Alternative, but aquatic organisms would also benefit

from upland treatments located near aquatic habitats. 

Because herbicide treatments would not be allowed 

under Alternative C, control of some aquatic weeds, 

including giant salvinia, water-thyme, and Eurasian 

watermilfoil, could be difficult, as mechanical and other 

non-herbicide treatment methods are less effective. 

Under Alternative B, the BLM’s ability to use four new 

chemicals (fluridone and diquat for aquatic applications, 

and imazapic and Overdrive® for terrestrial 

applications), and new herbicides as they become

available, would provide new capabilities to the BLM

for controlling problematic invasive species and would

provide benefits to aquatic resources and habitats if 

invasive species were controlled or eliminated. Under 

alternatives C and D, it could be difficult for the BLM

to adequately treat remote areas or large weed 

infestations to benefit aquatic organisms. Thus, the risk

of loss of aquatic habitat and habitat function in more

remote areas could be greater under alternatives C and

D than under the other alternatives. 

BLM Vegetation Treatments Using Herbicides 4-215 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Alternative E places greater emphasis on passive

restoration than the other alternatives. Passive 

restoration of aquatic habitats would likely entail

mitigation and management of terrestrial-based

activities, which could directly or indirectly affect

habitat quality. As discussed in Chapter 2, Vegetation 

Treatment Programs, Policies, and Methods, passive 

restoration would be considered when developing

restoration management plans, and would be used to the

extent possible within the constraints of FLPMA. 

Under Alternative E, the BLM would not be able to use

ALS-inhibiting active ingredients (i.e., chlorsulfuron, 

imazapic, imazapyr, metsulfuron methyl, and

sulfometuron methyl). 

Of the herbicides that would be unavailable to the BLM

under this alternative, imazapyr is the only one that 

could be used in riparian and aquatic habitats, where it 

has been shown to be very effective against saltcedar.

Imazapyr poses little risk to fish and aquatic organisms

when used at typical application rates. Without

imazapyr, the BLM would likely treat larger stands of

saltcedar using prescribed fire followed by a foliar 

application of triclopyr, and smaller stands by cutting

the stem and applying triclopyr. 

Chlorsulfuron, imazapic, and sulfometuron methyl do 

not pose risks to fish or aquatic invertebrates. 

Metsulfuron methyl poses a low risk to aquatic

invertebrates in streams under an accidental direct spray 

scenario involving the maximum application rate (an

unlikely scenario). Therefore, disallowing use of these

four herbicides would be unlikely to benefit fish and

aquatic organisms if they are replaced with herbicides 

that are more harmful to fish and other aquatic 

organisms. 

Short-term effects could accumulate, but if treatments 

were successful, a countervailing effect of long-term

improvement in habitat for aquatic organisms would

offset habitat losses. Regardless of the alternative 

chosen, loss of aquatic habitat and values would 

accumulate under all alternatives, but the rate of loss

would be expected to slow from historic levels over the 

long term.. 

Wildlife Resources 

Public lands sustain an abundance and diversity of

wildlife and wildlife habitat. Wildlife is found in areas 

where basic needs—food, shelter, water, reproduction, 

and movement—are met (Anderson 2001). In general,

the greater the diversity of habitats in an area the more 

species of wildlife that area can support. Some species, 

however, have special behaviors and physical traits that 

allow them to successfully compete with other animals 

in only one or a few habitats, limiting their distribution. 

As discussed in Chapter 3, several structural features

make some habitats better for wildlife than others. 

These features include: 1) structure, 2) vertical layers, 3) 

horizontal zones, 4) edge, and 5) and special features. 

The more of these features that are present in a habitat, 

the more niches there are in which animals can live 

(Cooperrider et al. 1986). 

Historically, landscapes provided a continuous mosaic

of vegetation types adapted to climatic and natural

disturbance regimes. Plant communities were dynamic 

and resilient, tending to return to some developmental 

(successional) pathway after a disturbance. Although

structural complexity varied depending on the

characteristics of the dominant vegetation (e.g., 

forestlands tend to be more structurally complex than

grasslands), even structurally “simple” habitats

provided numerous niches for wildlife to exploit. For

example, grasslands may provide only one or two strata, 

or levels, of vegetation for wildlife to use, but still 

contain a diversity of wildlife species (Payne and 

Bryant 1998). 

At the ecoregion level, habitats showed little change 

over decades or even hundreds or thousands of years. 

However, at the landscape level (1,000 to 100,000s of 

acres; Paige and Ritter 1999) and stand level (1 to

1,000s of acres), vegetation and habitats were in

constant flux, changing and adapting to natural

perturbations in the environment. Disturbances 

consisting of infrequent, high-intensity events (such as 

drought, flood, and major fire) interspersed with

frequent, low intensity events (wildlife grazing, low 

intensity burns, disease) constantly shaped and modified

the environment. As a result, habitat types varied over 

time and space and resulted in different species groups

being dominant at different times depending on the

characteristics of the habitat. 

Past Effects and Their Accumulation 

North America has been occupied by Native peoples for 

at least 12,000 years. As humans settled the West, they 

altered succession and introduced disturbance processes 

to which many native plants and animals were not

evolved. The following sections examine direct and

indirect human-related effects on wildlife habitat loss, 

modification, and fragmentation, and on wildlife health. 

These effects have resulted in death and harm to 

BLM Vegetation Treatments Using Herbicides 4-216 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

wildlife that has accumulated since the arrival of man in

North America. 

Habitat Loss. Approximately 21% of land in the 

western states (excluding Alaska) has been converted to 

intensive uses—urbanization, agriculture, and

pastureland—that provide fewer benefits for wildlife 

than undisturbed habitats or habitats subjected to less 

intensive uses (Wright 2002). Although wildlife find

food and shelter in highly modified habitats, these 

habitats generally provide fewer habitat values and are 

less structurally complex than the habitats they replace.

Therefore, they support fewer wildlife species and

numbers. 

Conversion of lands to more intensive uses has caused

injury and mortality to wildlife, primarily less mobile

species that live near the ground surface, and species 

that depend on special habitat lost during conversion. 

Large numbers of wildlife have been displaced, and 

many of these animals have died because they were 

unable to find food, shelter, or other life requisites, or

were unable to successfully compete with species found 

in their new environs. As urbanization and development 

has intensified in the West during the past several

decades, it has not been uncommon to see coyote, bear,

deer, and other wildlife in urbanized settings. Some of

these animals prey upon dogs, cats, and other domestic 

animals, or upon vegetation used for landscaping, and 

must be captured, removed, and in some case 

euthanized, to reduce this problem. Loss of habitat is 

also an important factor contributing to the increase in

the number of species listed as threatened or endangered 

in recent years (see BA prepared for this PEIS; USDI 

BLM 2007b). 

Some lands that have been developed for agricultural, 

urban, and industrial uses were once some of the most

productive lands in terms of resource values and

wildlife habitat. Once converted to these uses, the

habitat values they provided were impacted, often

significantly, and most wildlife populations they 

supported decreased. Wetland and riparian areas in the 

West are good examples of productive habitats that

have been lost or modified as a result of development. 

Even where wetlands and riparian areas still exist, they 

have often been converted to other uses. For example, 

much of the remaining wetland habitat in central and 

northern California has been converted to agricultural

uses (e.g., rice production). Although these areas 

provide habitat for waterfowl and other wildlife, their 

food, cover, and other habitat values are usually less 

than they were before the conversion. 

Industrial activities, such as mining, can substantially 

modify or eliminate habitat within and near the 

development footprint. Dams and water diversions have 

been constructed on most major rivers in the West. 

Where streams and rivers that once supported a 

productive riparian ecosystem have been dammed, the 

riparian ecosystems have been inundated by large lakes 

or reservoirs that provide some habitat for wildlife, but

are generally not as productive as they once were. 

Not all species are harmed by conversion of land to

more intensive uses. Numerous species are adapted to 

urbanized environments. Even native species that can 

readily adapt to change, or find their needs met by the

modified habitat, may thrive. For example, deer, elk, 

geese, and some songbirds have benefited by the 

conversion of lands to urban, agricultural, and

recreational uses. These species find food and water at

bird feeders, in intensively managed pasturelands, at 

golf courses and other parks, and in cornfields and other 

croplands. In some cases, species that use developed 

habitats may benefit from reduced predation pressure, 

as their predators are unable to adapt to the new 

surroundings. 

Habitat Modification. Most of the remaining 79% of 

lands that have not been converted to more intensive 

land uses (which would include most of the lands 

managed by the BLM) have still undergone some

modification that has reduced their value to wildlife. An

analysis of habitat condition in the Interior Columbia

Basin showed a general downward trend in habitat 

value from historical conditions for nearly all habitat 

types evaluated in the study (USDA Forest Service and

USDI BLM 2000). This study also showed that species 

that rely upon older forests, sagebrush, and grassland 

habitats have been most affected by loss and

modification of habitat in the region; similar losses of 

these habitat types have been seen throughout the

western U.S. (Payne and Bryant 1998, Paige and Ritter 

1999, Smith 2000). Factors that have modified habitat 

in the West include grazing by domestic livestock and 

wild horses and burros, timber management, fire

suppression, and invasion by weeds and other unwanted 

vegetation. 

Grazing. Excessive grazing pressure has modified

wildlife habitat over many areas in the West. Wetland

and riparian areas, in particular, have suffered from

heavy domestic livestock and wild horse and burro 

grazing pressure (USDA Forest Service and USDI BLM 

2000). Livestock grazing can remove or trample 

vegetation used by wildlife for food and cover. 

Domestic livestock removed much of the native grass in

BLM Vegetation Treatments Using Herbicides 4-217 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

the Great Basin by the early 20th century, and today, less 

than 1% of the sagebrush steppe in the region remains 

untouched by livestock (Paige and Ritter 1999). 

Livestock selectively choose grasses and forbs because

of their palatability and avoid browsing on sagebrush, 

which can have a toxic effect on the microorganisms in

their rumen (Young 1994). Grasses and forbs also 

provide food and cover for sage-grouse and other

sagebrush-dependent species. In areas with sparse

vegetative cover, such as the Subtropical Desert

Ecoregion, livestock can remove much of the available

forage. 

Timber Management. Since the 1800s, millions of acres 

of timber have been harvested in the West. Historically, 

preferred timber species were often the more valuable 

shade-intolerant species such as ponderosa pine, 

western white pine, and western larch, and the larger 

trees. Many stands were harvested using even-aged 

harvest techniques, such as clearcutting, which 

promoted conversion of forests to shade-intolerant trees 

that usually had single-storied canopies and lacked 

vertical structure (Payne and Bryant 1998). Species that

depend upon late seral forest habitat or a mosaic of 

forest types, such as spotted owl, white headed

woodpecker, white-breasted nuthatch, and western grey

squirrel, declined in numbers. Deer and elk thrived in

intensively managed forests, as dense even-aged stands 

provided good hiding cover (although poor snow 

intercept-thermal cover), and were often in close

proximity to recently-harvested clearcuts that provided 

grasses, forbs, and shrubs for forage. The checkerboard

system of clearcutting also increased edge (a place 

where two habitat types meet, such as a forestland and 

shrubland), to the benefit of edge species, including 

most game species, but to the detriment of forestinterior species (Payne and Bryant 1998). 

Fire Exclusion. During the past 100 years, fires have 

become less frequent and more intense in the western

U.S. (Agee 1993; Lyon et al. 2000a). Exceptions to this 

general trend have occurred in grassland and shrubland 

habitats that have been invaded by exotic annual

grasses, where fire frequency has increased beyond

natural fire cycles. Intense wildfires likely harm or kill 

more wildlife than less intense fires, and are more likely 

to destroy large areas of habitat, potentially eliminating

“islands” of habitat that may provide the only remaining

refuge for some species (Lyon et al. 2000b). 

Lack of frequent non-lethal burns has resulted in an

increase in stand density, an increase in shade tolerant 

species, and an encroachment of invasive species and 

trees into grasslands. In forests, nearly uniform stands of

dense, mid-seral trees limit the amount of light that can

reach the understory, preventing growth of understory

shrubs, grasses, and forbs (Payne and Bryant 1998). 

These changes have not only resulted in habitat loss for 

species that require open old-growth stands and early 

seral stages, but have also led to conditions that could 

result in large, severe fires in the future. Fire

suppression has benefited some species, such as 

northern spotted owl in parts of its range, but has made 

them more susceptible to harm by a large fire (Thomas 

et al. 1990). 

Dense stands of mid-seral trees are often lacking in 

special habitat features that are found in more mature 

forests. For example, early- and mid-seral forests are

less able to capture snow in their branches than more

mature trees. Where large trees capture snowfall in their 

branches during winter, rather than letting it accumulate

on the ground, shrubs and other types of forage are 

more readily available to deer and other browsers, and 

animals are able to travel through the snow without 

difficulty. 

Changes in rangeland habitat, either from fire 

suppression that has allowed shrubs and trees to invade 

grasslands, or from high fire frequency that has 

encouraged the growth of non-native annual weeds, has

impacted rangeland species such as sage-grouse,

Brewer’s sparrow, and sage sparrow (Paige and Ritter 

1999). Encroaching shrubs and trees crowd out grasses 

and forbs used by wildlife, while annual weeds provide 

little forage value or habitat structure for wildlife. 

Declines in big game winter range, density of nesting

raptors, and non-game bird abundance have also been 

observed in areas dominated by downy brome (USDA 

Forest Service and USDI BLM 2000). 

Invasive Species. Euroamerican settlement facilitated 

the invasion and spread of invasive plants. Weeds and

other invasive species are able to colonize disturbed 

(downy brome) and relatively intact (spotted knapweed, 

yellow starthistle, and leafy spurge) sites, reproduce and

grow quickly, and outcompete native species for water 

and nutrients. Construction of roads and ROWs has 

facilitated the spread of weeds. Noxious weeds and

other exotic plants harm wildlife by reducing the

amount of high quality forage and habitat complexity in

an area so that it is unable to support an abundance and 

diversity of wildlife (Payne and Bryant 1998). Invasive 

species can also increase sedimentation and surface

water runoff to the detriment of amphibians and other 

aquatic species whose habitats may be impacted. 

Pinyon-juniper woodlands have encroached into

grasslands over much of the West, to the detriment of 

BLM Vegetation Treatments Using Herbicides 4-218 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

edge species and ground-nesting and foraging species. 

However, the expansion of these species has also

benefited wildlife, as pinyon-juniper woodlands provide 

forage for wintering deer, and in some areas, support 

more bird species than forest and sagebrush 

communities (Payne and Bryant 1998). 

Habitat Fragmentation. From historical to current

periods, there has been an increase in fragmentation of 

larger habitats into smaller “islands” of habitat and a

loss of connectivity within and between blocks of 

habitat, especially in lower elevation forests, 

shrublands, and riparian areas (USDA Forest Service 

and USDI BLM 2000). All of the factors discussed

above have contributed to the fragmentation of habitats

in the West. 

In general, the smaller the habitat island, the fewer the 

species it can support, since larger areas support a

greater diversity of vegetation types and microhabitats. 

Larger areas are also able to support uncommon species

that live at low population densities. In addition, small

islands, on average, support small populations, which 

are more likely than large populations to go extinct 

(Hunter 1990). This risk of extinction is a concern for 

several special status species that are restricted to small

islands of habitat. A catastrophic wildfire or other major 

habitat-disturbing event could make the habitat

unsuitable for some special status species, leading to 

their extinction. For example, pygmy rabbits in

Washington State are restricted to a few small areas of

sagebrush habitat in central Washington surrounded

primarily by agricultural land. A major fire event or 

disease would likely eliminate the population 

(McAllister 1995). 

Fragmentation isolates sedentary and less mobile animal

populations, or populations with restricted habitat 

requirements, and reduces their ability to disperse across 

the landscape, potentially leading to long-term loss of

genetic exchange. Even where habitats are contiguous, 

human disturbance (e.g., roads, noise) and development

can discourage wildlife from moving between adjacent

areas, effectively fragmenting habitat. Fencing for 

livestock can also inhibit the free movement of some

wildlife species. 

Public land settlement policies have, in part, contributed 

to the fragmentation of habitats across the West. Public 

lands in many states outside of Nevada are often

scattered and have taken on checkerboard, jigsaw, and

patchwork patterns as a result of public land policies 

pursued by the country prior to the BLM’s founding in 

1946. As a result, blocks of public land are often 

isolated and surround by agricultural or other lands.

From a wildlife perspective, these blocks act as islands, 

and some species may be unwilling or unable to travel 

between blocks of public land or other suitable habitat 

(Muhn and Stewart 1988). In contrast, there are also

large tracts of contiguous public lands in the West that 

provide habitat connectivity for many species, including 

sage-grouse, deer, elk, and numerous migratory bird

species. 

Wildlife Health. Human-related activities are 

responsible for the death and injury of wildlife each

year. Hunting removes large numbers of animals each

year. Approximately 409,000 hunters used public lands 

in FY 2005 (USDI BLM 2006d). Hunting did not

adversely affect populations of most species, but 

overharvest of other species, including American bison, 

pronghorn antelope, and wild turkey, nearly led to their 

demise. 

Thousands of animals are killed each year by 

automobiles and other vehicles, and from flying into

powerlines and other elevated structures associated with 

ROW, wind-power generating facilities, transmission 

towers, and other structures. Wildland and prescribed

fires kill or harm animals, with animals that have 

limited mobility and live above the ground being most

vulnerable (Lyon et al. 2000b). Disturbance associated 

with public recreation, including public-use facilities 

and OHV use, has displaced wildlife or impacted their 

activity patterns and habitat use, and likely led to some

deaths or reduced animal health. 

The use of pesticides, especially organochlorine 

pesticides such as DDT, has caused death, sickness, and

poor reproduction in birds and other wildlife, especially 

prior to the 1980s when the public was largely unaware

of these issues. Diseases that spread from domestic 

animals to wildlife (e.g., rabies) can also contribute to 

the loss or harm of wildlife. 

In recent years, several studies have focused on the 

effects of herbicides and other pesticides on amphibian 

survival, development, and growth. A study of 

herbicides sprayed for pest control in Canada showed

that effects to amphibian embryos and larvae from 

hexazinone, glyphosate, triclopyr, and three other 

herbicides that are not used by the BLM, were similar to

those found in freshwater fish when herbicides were 

applied at typical application rates; high concentrations 

of hexazinone did not affect embryos and tadpoles, but 

concentrations of triclopyr 2.4 ppm or greater led to

death of newly hatched tadpoles (Berrill et al. 1994;

Berrill et al. 1997). 

BLM Vegetation Treatments Using Herbicides 4-219 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Herbicides can often be more selective than mechanical

or fire treatments and just as selective as manual

treatments in forestlands (Payne and Bryant 1998). 

Common herbicides used in forest wildlife management 

include asulam, atrazine, 2,4-D, glyphosate, simazine, 

and tebuthiuron; however, the BLM has not used 

atrazine or asulam on public lands since at least 1997. 

Spraying herbicides over conifer plantations eliminates 

competing shrubs and hardwood sprouts, but also 

reduces the value of these forests to wildlife (Rutske

1969). If treatments are done in patches or strips,

important refuge areas can be created for amphibians, 

reptiles, birds, and small mammals (Payne and Bryant

1998); staggering treatments over several years can

achieve the same effect. 

Future Effects and Their Accumulation 

The objective of future management will be to restore 

native vegetation in fire-adapted ecosystems to benefit 

wildlife and their habitats. Treatments that reduce

hazardous fuels on public lands, control the spread of 

non-native plant species, and restore natural fire regimes 

would benefit most wildlife. Species that have adapted

to, or have exploited, habitats that have developed as a

result of fire suppression and weed spread may decline 

in numbers. However, modeling conducted during 

development of the cohesive strategy, and for the 

Interior Columbia Basin assessment, suggests that it

will take decades to centuries for treatments to result in

major habitat changes (USDA Forest Service and USDI

BLM 2000; Hann et al. 2002). 

Habitat Loss. Vegetation treatments will do little to 

slow the loss of habitat in the West. Population growth 

in the West will likely continue to exceed that of the rest

of the country, placing new demands on undeveloped

land to meet human-related needs, including

urbanization, agriculture, and recreation. As a result, 

more wildlife will be lost or displaced as lands are

converted to uses that do not support historic species or

numbers of wildlife, and it is likely that many displaced

animals will perish. It is also possible that loss of habitat

could lead to the extirpation of species, although the 

provisions of the ESA should minimize this risk. Most

habitat loss would occur on privately-owned lands, 

although public lands will continue to be developed for 

mining, oil and gas, recreation, roads and other uses as 

authorized under FLPMA. 

Habitat Modification. The basic premise of the 

vegetation treatment program is to manage ecosystems

to maintain viable populations of native and desirable 

non-native plant and animal species. This goal would be

accomplished by using fire and other treatments to

reduce hazardous fuels and the risk of catastrophic fire, 

to reduce or eliminate weeds and other invasive plants, 

and to promote conditions that favor the restoration and 

development of native vegetation. While treatments 

would not stem the loss and modification of vegetation 

and wildlife habitat that occurs on private lands, they 

would improve ecosystem health on public lands and 

improve habitat for wildlife that historically used

treatment areas. 

Over half the treatments would occur in the Temperate

Desert Ecoregion. Much of this ecoregion is comprised

of grasslands and shrublands that have altered fire 

regimes, have suffered large-scale fires during the past

decade, and are dominated by downy brome and other 

invasive species. Treatments are also targeted at

evergreen woodlands, primarily to slow the 

encroachment of pinyon, juniper and other woodland 

species into grassland habitats. 

There is currently greater awareness than there was 

historically, on the part of the BLM and other federal

land management agencies, and the public, about the

effects of livestock, wild horses and burros, timber

management practices, mining, fluid minerals, and other 

land disturbing activities, on wildlife habitat. Better 

management of human-related disturbance factors

through application of site-specific mitigation, SOPs, 

reclamation and rehabilitation, and monitoring, will

continue to benefit wildlife habitat. 

Habitat Fragmentation. Factors that contribute to habitat

fragmentation on and off public lands will continue,

increasing the likelihood of local extinctions of wildlife 

and loss of species diversity; these risks are greatest on 

privately-owned lands. Vegetation management that

creates a mosaic of native vegetation within larger 

continuous areas of similar habitat would be beneficial

to “interior” and wide-ranging species. Efforts to restore 

native vegetation in disturbed areas would help to link 

islands of habitat, as would forest treatments focused on

thinning, rather than clearcutting, timber. Closing and

revegetating little-used or abandoned roads and 

removing or modifying fencing and other barriers 

would encourage the movement of wildlife among

habitats and facilitate genetic exchange among

populations. Treatments that reduce the risk of 

catastrophic fire and the spread of weeds would result in

more continuous stands of similar vegetation and a

reduced likelihood that islands of good habitat would be 

surrounded by less desirable habitat (e.g., a patch of 

native riparian sagebrush surrounded by a continuous

stand of downy brome). 

BLM Vegetation Treatments Using Herbicides 4-220 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

In addition, efforts by the BLM and Forest Service to

consolidate landholdings through land tenure 

adjustments, such as land exchanges with other federal 

agencies and private landowners to create larger blocks 

of common ownership, would help to reduce habitat

fragmentation and improve management of federal and

private lands. 

Wildlife Health. Hunting and other disturbance factors 

that have impacted wildlife in the past are likely to 

continue. However, current management of game

populations and enforcement of hunting laws has 

reduced the risk of major declines in the numbers of

game species from historic levels. Development and

implementation of land use and project-level plans that

consider the effects of OHVs and other disturbance 

factors, road closures, screening of facilities, and other 

SOPs to minimize disturbances would benefit wildlife. 

Although the amount of herbicides used by the BLM

and Forest Service to treat vegetation would increase in 

response to proposed treatment programs, the risks to

wildlife should remain near current levels, or decline, as 

both agencies move towards used of less toxic 

chemicals to treat vegetation. In particular, the BLM 

and other federal agencies would ensure that herbicide 

formulations that have been shown to be harmful to

amphibians and other wildlife, such as atrazine and 

glyphosate formulations containing POEA and R-11, 

are not used or are used minimally and only in areas 

where benefits of use greatly outweigh risks to wildlife. 

Atrazine appears to increase mortality in amphibians 

and acts as an endocrine disruptor that chemically

castrates and feminizes male amphibians (Hays et al.

2006; Rohr et al. 2006). Atrazine, which would be

available for use only under Alternative A, has not been 

used by the BLM for over 7 years and there are no plans 

to use this herbicide in the future. 

The use of atrazine, glyphosate formulations containing 

POEA and R-11, triclopyr, and other herbicides that are 

harmful to amphibians and other wildlife, would

continue be used on private lands and could cause the

decline in numbers of amphibians and other wildlife in

areas where they are used. Fifty-one thousand tons of 

glyphosate, thirty-eight thousand tons of atrazine, and 

six hundred sixty-eight tons of triclopyr were applied to

non-federal agricultural lands and rangelands during

2002. Use of triclopyr has increased 11-fold, and

glyphosate 6-fold, since 1992 on these lands. 

Contribution of Treatment Alternatives to

Cumulative Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to 

wildlife and habitat would be greatest under the 

Preferred Alternative, and least under the No Action

Alternative. The number of acres treated, and the effects 

to wildlife and habitat would be similar under 

alternatives D and E. Effects to wildlife and habitat 

under Alternative C would be intermediate between 

these alternatives and the Preferred Alternative. 

It is anticipated that the use of wildland fire use and 

prescribed fire and herbicides, and mechanical methods, 

would have the greatest short term impacts on wildlife

and their habitat, and that impacts would be somewhat

in proportion to acres treated. Approximately three 

times as many acres would be treated annually using 

herbicides under the Preferred Alternative than under 

the No Action Alternative, and about twice as many

acres would be treated using herbicides under the 

Preferred Alternative than under alternatives D and E. 

No acres would be treated using herbicides under

Alternative C. In addition, approximately twice as many 

acres would be treated using prescribed and wildland 

fire under the Preferred Alternative than under 

alternatives C, D, and E, and three times as many as

compared to the No Action Alternative. Acres treated

using mechanical methods would be similar among 

alternatives B, C, D, and E (about 2 million acres

annually), and greater than for the No Action

Alternative (about 582,000 acres annually). 

Short-term effects from treatments and other human

causes would accumulate, but a countervailing effect of

long-term improvement in the ecosystem health and 

wildlife habitat with success and maintenance of 

treatments, would offset short-term losses. 

Alternative E places greater emphasis on passive

restoration than the other alternatives. Passive 

restoration is often considered a critical first step in

successful restoration of degraded areas, since

anthropogenic activities that are causing degradation or

preventing recovery are halted. As discussed at the 

beginning of the cumulative effects section, passive 

restoration would be considered under all alternatives 

when developing restoration management plans, and 

would be used to the extent possible within the 

constraints of FLPMA. However, alternatives A through

D would likely take a more aggressive approach to

vegetation management than Alternative E. 

BLM Vegetation Treatments Using Herbicides 4-221 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

All alternatives include both passive and active

management. Recovery of vegetation through passive 

management is expected to take longer than under 

active management, where treatments such as seeding

with native species, establishing intermediate vegetation 

to control erosion, and use of pre-emergent herbicides to 

prevent weed establishment would be expected to

promote faster recovery. 

The risks to wildlife from use of herbicides could be 

less under Alternative E than under the other herbicide 

use alternatives because ALS-inhibiting herbicides 

would not be used under Alternative E. ALS-inhibiting

herbicides are effective at very low doses and could 

drift onto wildlife and harm them. However, in this 

assessment, the ALS-inhibiting herbicides mostly posed

no risk to terrestrial wildlife (chlorsulfuron, imazapic,

sulfometuron methyl), except for a few cases of low risk

(imazapyr, metsulfuron methyl), suggesting that 

prohibiting the use of these herbicides would not likely 

benefit wildlife and could indirectly harm wildlife if

more toxic herbicides that are currently available to the 

BLM were used in their place. 

The risk of herbicide drift affecting wildlife and their 

habitats would be less under alternatives D and E than

under the other herbicide treatment alternatives, as 

aerial treatments are prohibited under Alternative D, and

discouraged under Alternative E. 

Over the long term, treatments should restore native 

vegetation and natural fire regimes and benefit 

ecosystem health and wildlife and their habitats. 

Regardless of the alternative chosen, however, there

would be a cumulative loss of native vegetation and 

healthy ecosystem function that would continue into the

future. 

Livestock 

Approximately 165 million acres of public lands are

open to livestock grazing, with use levels established by 

the Secretary of the Interior and administered through 

the issuance of grazing permits/leases. The majority of

the grazing permits issued by the BLM involve grazing

by cattle, with fewer and smaller grazing permits for 

other kinds of livestock, which would include primarily 

sheep and horses. Livestock grazing leases and fees 

contribute $12 to $15 million annually to the U.S. 

Treasury, and ranching is an important economic and

social component of many rural communities (USDI 

BLM 2006c). There are over 12.7 million active animal 

unit months that could be authorized for use on public 

lands. The ability of public lands to support healthy 

populations of domestic livestock is important to the

livelihood of livestock producers. 

Past Effects and Their Accumulation 

Loss of native vegetation and deterioration in ecosystem

health on public land due to changes in fire regimes, as 

well as an increase in lands dominated by noxious

weeds and other invasive vegetation, has contributed to 

reductions in the ability of public lands to support

livestock grazing. Livestock grazing itself is a factor

contributing to some of these changes. However, 

increases in other human-caused factors such as mineral

extraction and recreation have also affected vegetation 

communities or resulted in conflicts that reduce the

ability of public lands to support livestock grazing. 

Where human activities and wildland fire have

disturbed the land, weeds and other unwanted species 

have taken over and in some cases dominated

landscapes (USDA Forest Service and USDI BLM

2000). It is estimated that downy brome alone covers 

over 11 million acres in the West, and that leafy spurge

covers 3 million acres (Lajeuness et al. 1998). Weed

species are often of little nutritional value to livestock, 

and some weed species are toxic to livestock. 

Future Effects and Their Accumulation 

The focus of management in the future is on restoring

ecosystem processes and maintaining livestock 

populations in balance with the health of rangelands. 

Many of these treatments will require rest from

livestock grazing and will therefore result in temporary 

reductions in livestock grazing. In the long term, 

treatments that remove hazardous fuels from public 

lands would be expected to benefit the health of plant

communities in which natural fire cycles have been

altered. Treatments that restore and maintain fireadapted ecosystems through the appropriate use of 

mechanical thinning, fire, and other vegetation

treatment methods would decrease the effects of 

wildfire on communities and improve ecosystem

resilience and sustainability. Treatments should also 

reduce the incidence and severity of wildfires across the

western U.S. to the benefit of livestock (USDA Forest

Service and USDI BLM 2000). 

Vegetation treatments would provide a better mix of 

habitats so that vegetation would be more resilient to

disturbance and sustainable in the long term. Treatments

would reduce the encroachment and density of woody

species in shrublands and/or undesirable herbaceous 

species in rangelands. Treatments would slow the 

spread of weeds and increase the number of acres 

BLM Vegetation Treatments Using Herbicides 4-222 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

dominated by bunchgrasses and other important forage

for livestock. Although the number of acres impacted by

weeds and other exotic and undesirable plants would 

continue to increase, the rate of increase should slow 

(USDA Forest Service and USDI BLM 2000). 

In addition, the BLM will continue efforts to bring 

livestock populations in balance with the condition of 

rangelands. Where feasible, the BLM will incorporate

the use of livestock as part of the overall weed 

management program, and improvements will be made

to the grazing management program and grazing

regulations (see Proposed Revisions to Grazing 

Regulations for the Public Lands Final EIS; USDI 

BLM 2004). Although these efforts should benefit the 

livestock industry, it is projected that there will be a 

slow, but steady loss in availability of public lands for 

livestock grazing (USDA Forest Service 1989, USDA 

Forest Service and USDI BLM 2000). 

Contribution of Treatment Alternatives to

Cumulative Effects 

Based on the number of acres treated, short-term

impacts and long-term improvements to domestic

livestock would be greatest under the Preferred 

Alternative, and least under the No Action Alternative. 

The number of acres treated, and the effects to these

animals, would be similar under alternatives D and E. 

Effects to livestock under Alternative C would be 

intermediate between these alternatives and the

Preferred Alternative. Short-term effects from

treatments and other human causes would accumulate,

but if treatments were successful, a countervailing effect

of long-term improvement in the ecosystem health and 

range conditions. 

Alternative E places greater emphasis on passive

restoration through the elimination or reduction of uses 

on public lands than the other alternatives. Livestock

grazing is often cited as a factor contributing to loss of 

resource function and degradation of rangeland quality. 

By reducing the number of livestock entering degraded

areas, improvement in ecosystem health can be 

expected (Kauffman et al. 1997). Thus, fewer livestock 

may be able to graze on public lands under this 

alternative than under the other alternatives. 

The risks to non-target vegetation from use of

herbicides could be less under Alternative E than under

the other herbicide use alternatives because ALSinhibiting herbicides would not be used. ALS-inhibiting

herbicides are effective at very low doses and could 

drift onto non-target vegetation, where a potential 

impact could occur, depending on the species 

composition of the non-target site and the ALSinhibiting herbicide selected. However, risk assessments 

did not predict risk to livestock for any of the ALSinhibiting herbicides when applied at the typical

application rate under any of the modeled scenarios, 

suggesting that prohibiting the use of these herbicides 

would not benefit livestock and could indirectly harm

livestock if more toxic herbicides were used in their 

place. 

The risk that herbicide drift would affect livestock 

would be less under alternatives D and E than under the

other herbicide treatment alternatives, as aerial

treatments are prohibited under Alternative D, and

discouraged under Alternative E. Regardless of the 

alternative chosen, there would be a cumulative loss of 

rangeland forage for livestock. 

Wild Horses and Burros 

The Wild Free-Roaming Horses and Burros Act of 1971

provides protection for all wild horses and burros on 

federal lands and provides guidance for their 

management as a wildland species. At the time the Act 

was passed, approximately 17,000 wild horses occupied

federal lands designated for their protection. By 1980, 

the number of wild horses had increased to between 

65,000 and 80,000 (USDI BLM 2005d). As a result of 

this increase, impacts to vegetation, water, and soil from 

wild horses and burros increased, especially in heavily 

used areas. Loss of native vegetation, especially grasses 

and some shrubs, due to wildfires and invasive plants 

further reduced available forage and increased 

competition among wild horses and burros, livestock, 

and wildlife for dwindling resources. The loss of native 

vegetation and degradation of ecosystems has impacted

wild horses and burros and has likely reduced herd 

productivity in some herd management areas. At the 

same time, wild horses and burros have adversely 

impacted vegetation, although efforts to reduce herd 

populations in recent years have reduced these effects 

(USDI BLM 2001c). 

Past Effects and Their Accumulation 

The wild horses that roam the West are feral

descendants of domestic stock that were brought to 

North America by European colonists. No native wild

horses existed in North America at that time, even 

though horses evolved in North America, and spread to

Eurasia about 2.5 to 3 million years ago. The last

remaining native horses persisted in North America 

until about 8,000 to 10,000 years ago, when they 

BLM Vegetation Treatments Using Herbicides 4-223 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

became extinct. Climate change, change in vegetation, 

and perhaps overexploitation by Native Americans may

have contributed to the horse’s demise in North 

America (USDI BLM 2005d). 

The Spaniards reintroduced horses and burros into 

North America during the 1500s. By the 1800s, more 

than 2 million wild horses roamed western North

America. Population growth resulted from successful 

reproduction in the wild, and from escape or

abandonment of domestic horses brought to the frontier 

by trappers, settlers, miners, and other immigrants. Wild

burro herds also increased as individuals escaped from

shepherds and miners. At the same time, the available

open range began to shrink as livestock, fences, farms, 

ranches, and roads proliferated. Wild horses were shot 

to reduce competition with livestock, or rounded up and

sold for use as draft animals, military mounts, and food. 

Burros were less persecuted because they tended to

graze lands that were too barren and dry for livestock to 

use (USDI BLM 2001c, 2005f). 

The Taylor Grazing Act of 1934 authorized the 

formation of the Grazing Service (a precursor to the

BLM) and empowered the Service to responsibly 

manage grazing pressure on federal rangelands. This 

step accelerated the capture and removal of wild horses 

and burros, which were primarily used as pet food.

Lucrative European markets for horsemeat emerged, as

did domestic markets for use of horsemeat in pet and 

chicken feed. By the 1950s, the number of wild horses 

dropped to less than 20,000. In addition, professional

horse-catchers often used brutal methods to capture and

transport wild horses for sale to slaughterhouses. Public 

concern developed over the falling population and 

inhumane treatment of animals (USDI BLM 2005d). 

In response to concerns over the plight of wild horses 

and burros, the Wild Horse Annie Act was passed in

1959 that prohibited hunting or harassment of wild

horses on public lands using motorized vehicles or 

aircraft, although enforcement was difficult. In the Wild 

Free-Roaming Horses and Burros Act of 1971, 

Congress stated that free-roaming horses and burros 

were living symbols of the historic and pioneer spirit of

the West; that they contributed to the diversity of life

forms within the Nation and enriched the lives of the 

American people; and that these horses and burros were

fast disappearing from the American scene. Congress 

mandated that wild free-roaming horses and burros be 

protected from capture, branding, harassment, and death

(USDI BLM 2005d). Responsibility for management 

fell upon the BLM and Forest Service. 

Under protection, herds thrived and increased to over 

65,000 by 1980. Unlike wildlife, which are hunted, and 

livestock, which are managed under a permit system, 

there were no controls on wild horse and burro 

populations. In absence of control, populations increase 

by 15 to 20% annually. 

The BLM strives to manage wild horses and burros as 

wildland species, not as livestock. Typically, the BLM

does not feed or water the animals, but does intervene 

during extreme drought, fire, or freezing weather, and

may relocate animals or remove them from the range

during extreme conditions. For example, more than 

3,500 animals were removed from public lands in 2000

due to extreme drought conditions and placed in longterm holding facilities (USDI BLM 2001c). 

Wild horses and burros are managed in herd 

management areas, where the BLM tries to balance the 

number of animals with the available resources needed

by the animals for survival. Land managers consider the 

number of animals, rangeland health, and other desired

rangeland uses in developing an appropriate 

management level. Wild horse advocates express 

concern about keeping numbers too low to maintain 

genetic diversity. Many sportsmen and ranchers want

the number of wild horses and burros reduced because 

they compete with wildlife and livestock for food 

(USDI BLM 2001c). 

Urbanization has reduced the amount of private land 

near public land that is available to wild horses and 

burros. Paved highways, traffic, cross-fencing, and

livestock gates impede herd movements and have 

reduced the amount of land available for wild horses 

and burros. Loss of native vegetation and deterioration 

in ecosystem health on public land during the past 100 

years due to changes in fire regimes, increases in lands 

dominated by weeds and other noxious vegetation, and 

other human-caused factors, have increased competition

for dwindling plant resources by these animals and 

further contributed to the loss and degradation of native

plants. Livestock and wild horses and burros often

congregate in areas with high quality forage or water, 

including wetland and riparian areas. As some native 

habitats are impacted, they provide new areas for 

invasive weeds, perpetuating the downward trend in

land health. Although wild horses and burros occur in 

10 states, most animals are found in Nevada (46%) or 

Wyoming (13%), in the Temperate Desert Ecoregion

(see Table 3-7). Rangeland conditions in many areas 

where wild horses and burros are found are degraded. 

To reduce damage to rangeland ecosystems, the BLM

began to reduce wild horse and burro numbers 

BLM Vegetation Treatments Using Herbicides 4-224 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

beginning in the 1980s. By 1996, there were about

40,000 wild horses and burros on public lands. In FY 

2005, wild horse and burro populations on public lands

totaled over 31,760 animals, with nearly half of these 

animals living in Nevada (Table 3-7). Another 25,000

animals are held in holding pens. The population of 

wild horses and burros is approximately 4,000 animals

above the Appropriate Management Level (AML) of

27,500. The AML is an estimate of the number of wild 

horses (USDI BLM 2006c, d). 

Future Effects and Their Accumulation 

The focus of management in the future will be on

restoring native ecosystem processes and keeping wild

horse and burro populations in balance with the health

of rangelands. Treatments that remove hazardous fuels 

from public lands would be expected to benefit the 

health of plant communities in which natural fire cycles

have been altered. Treatments that restore and maintain

fire-adapted ecosystems, through the appropriate use of

mechanical thinning, fire, and other vegetation

treatment methods would decrease the effects of 

wildfire on communities and improve ecosystem

resilience and sustainability. Treatments should also 

reduce the incidence and severity of wildfires across the

western U.S. to the benefit of wild horses and burros 

(USDA Forest Service and USDI BLM 2000). 

Treatments would improve the mix of habitats so that 

vegetation would be more resilient to disturbance and 

sustainable over the long term. Treatments would

reduce the encroachment and density of woody species 

in shrublands and/or herblands. Treatments would slow 

the spread of weeds and increase the number of acres 

dominated by bunchgrasses, Indian ricegrass, western

wheatgrass, and other important forage species of wild

horses and burros. As a result, plant communities that

have declined substantially in geographic extent from

historical to current periods (e.g., big sagebrush and 

bunchgrasses) would increase. Although the number of 

acres impacted by weeds and other exotic and 

undesirable plants would continue to increase, the rate 

of increase should slow (USDA Forest Service and

USDI BLM 2000, USDI BLM 2001c). 

The BLM will continue management efforts to keep 

wild horse and burro populations at appropriate 

management levels in balance with the condition of 

rangelands. This will require continued removal and

adoption of animals, and continuing efforts to develop a 

fertility control agent for these animals. Nearly 209,000 

animals have been adopted since 1971 (USDI BLM

2006d). The number of animals found in the Temperate 

Desert. However, populations on public lands need to

be reduced from about 31,000 to 27,500 animals to

bring populations in balance with their habitat. As a 

result, effects to wild horses and burros from habitat 

degradation will continue to accumulate because fewer 

animals can be supported by degraded ecosystems than 

by healthy ecosystems (USDI BLM 2001c, 2005f). 

Contribution of Treatment Alternatives to

Cumulative Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to the 

wild horses and burros would be greatest under the 

Preferred Alternative, and least under the No Action

Alternative. The number of acres treated, and the effects 

to these animals would be similar under alternatives D 

and E. Effects to wild horses and burros under

Alternative C would be intermediate between these

alternatives and the Preferred Alternative. Short-term

effects from treatments and other human causes would

accumulate. A countervailing effect of long-term 

improvement in ecosystem health and the ability of 

public lands to support wild horses and burros would

offset short-term losses through successful treatments 

meeting desired objectives. 

Alternative E places greater emphasis on passive

restoration than the other alternatives. Passive 

restoration is often considered a critical first step in

successful restoration of degraded areas, since

anthropogenic activities that are causing degradation or

preventing recovery are halted. Foraging by wild horses 

and burros is often cited as a factor contributing to loss 

of resource function and degradation of rangeland 

quality. By maintaining the number of wild horses and

burros on public lands at levels in balance with 

rangeland productivity, improvement in habitat function 

would be expected (Kauffman et al. 1997). 

The risks to non-target vegetation from use of

herbicides could be less under Alternative E than under

the other herbicide use alternatives because ALSinhibiting herbicides would not be used. ALS-inhibiting

herbicides are effective at very low doses and could 

drift onto non-target vegetation and degrade the forage 

quality of the impacted area. However, as with

livestock, risk assessments did not predict risk to wild

horses and burros for any of the ALS-inhibiting

herbicides, when applied at the typical application rate, 

under any of the modeled scenarios, suggesting that

prohibiting the use of these herbicides would not benefit

livestock and could indirectly harm these animals if

more toxic herbicides were used in their place. 

BLM Vegetation Treatments Using Herbicides 4-225 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

The risk of drift affecting wild horse and burro health

would be less under alternatives D and E than under the

other herbicide treatment alternatives, as aerial

treatments are prohibited under Alternative D, and

discouraged under Alternative E. Regardless of the 

alternative chosen, there would be a cumulative loss of 

rangeland habitat for wild horses and burros. 

Paleontological and Cultural Resources 

Paleontological Resources 

Paleontological resources (plant and animal fossils) are 

nonrenewable. Since paleontological material is buried, 

the location of plant and animal fossils is predictable 

only to a limited degree, and most fossil localities 

remain unknown, making assessment of cumulative 

impacts difficult. In many settings, paleontological

resources are well protected by nature, in that they are

so deeply buried and completely encased in sediments 

or rock that virtually nothing can impact them aside 

from excavation. In other instances, they are located on 

or near the ground surface and are very susceptible to 

impacts. 

Once paleontological resources are impacted or 

displaced from their natural context, the damage is 

irreparable and cumulative. Paleontological resources 

are found over much of the West. Except perhaps for 

mechanical treatments and fire use, vegetation treatment

methods do not present a substantial threat to 

paleontological resources. 

Past Effects and Their Accumulation. Most

paleontological material is typically buried considerably 

deeper than archaeological material and is therefore not

regularly encountered by chance. However, some

fossiliferous formations, particularly in the arid West, 

crop out at or near the surface and may have surface

expressions or eroded material as “float.” Natural and 

human activities that cause ground disturbance have 

likely impacted near-surface paleontological resources 

throughout the West. Paleontological research and

excavation, necessary for the recovery of scientific data, 

have contributed to the displacement of paleontological

resources. Past exploration and development of the 

West led to legal and illegal collecting and inadvertent 

damage, especially prior to the 1970s when there was 

less concern for protecting these resources. As 

awareness for the importance of these resources has 

increased, and as state and federal regulations have been 

put in place that require surveys for and prohibit the

removal of paleontological resources, the cumulative 

loss of paleontological resources has slowed. 

Future Effects and Their Accumulation. Most

paleontological material is exposed as a result of natural 

erosion. Typically, erosion occurs as a result of the

action of flowing water, but it also can occur as a result

of wind, seasonal freezing and thawing, ground 

subsidence, and the movement of soil down slopes. 

Natural erosion, and its impact on paleontological

resources, is difficult to assess because in most cases it

is regarded as discovery rather than a negative impact to

the resource. Some of the most important

paleontological resources are associated with river bank 

cuts and drainages. 

An estimated 305,000 to 932,000 acres could be 

disturbed by herbicide treatments during the next 10 to 

15 years under the herbicide treatment alternatives. Of 

this area, about half would be treated using grounddisturbing equipment, and only a small portion would 

involve substantial ground disturbance that could

impact paleontological resources. An additional 1.7 to 

5.1 million acres could be impacted by other vegetation 

treatment methods, including 4.3 million acres by 

wildland fire use or prescribed fire and grounddisturbing equipment. These treatment methods pose

the greatest risks to paleontological resources, either 

through direct harm to resources, or indirectly as a result 

of soil erosion and other soil disturbances that could 

result from treatments (see PER). In addition,

population growth and development in the West have

resulted in land impacts that disturb soil. These actions 

have the potential to add to the cumulative loss of

paleontological resources. Site reclamation would not

reduce this loss, as paleontological resources would 

have already been lost during site disturbance and

development. 

New innovations in technology that reduce the amount

of surface disturbance associated with development on

public and private lands, and enforcement of regulations

that require the assessment and protection of 

paleontological resources before ground-disturbing 

activities can occur, would contribute to the future

protection of paleontological resources and slow their 

cumulative loss. Assessments to identify and protect 

paleontological resources in proposed treatment areas 

should minimize or avoid the loss of these resources. In

addition, vegetation treatments that restore natural fire 

regimes and native plant communities, and improve

ecosystem health, would lead to conditions that would 

slow soil erosion and reduce risk of fire, slowing the 

loss of paleontological resources. 

Contribution of Alternatives to Cumulative Effects. 

The potential for cumulative impacts to paleontological 

BLM Vegetation Treatments Using Herbicides 4-226 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

resources from vegetation treatments would be least 

under the No Action Alternative and greatest under the 

Preferred Alternative, based on the number of acres that 

would be impacted by ground-disturbing activities. 

Other treatment alternatives would be intermediate

between these two. Most equipment would disturb only 

the upper few inches of soil, and in many cases, would 

be confined to existing disturbed areas such as 

roadways, trails, and other ROWs. All treatment

methods could cause indirect loss of paleontological

resources as a result of erosion and soil disturbance, but 

these effects would be minimal. Potential effects would

be further reduced because the BLM has surveyed, or 

would conduct surveys in the future, for paleontological

resources to lessen the chance they would be impacted

by treatment activities. Thus, there would be a

negligible cumulative loss of paleontological material

on public lands due to vegetation treatment methods

under all alternatives. 

Cultural Resources and Traditional Lifeway 

Values

Cultural resources, including archaeological and historic 

sites and materials, as well as traditional cultural 

properties, have a very limited ability to absorb

cumulative impacts. Cultural resources, which are nonrenewable resources, risk being destroyed by erosion,

construction, excavation, data collection, and looting; 

removal of artifacts from their surrounding contexts; 

movement of the material such that it loses context; or 

removal or re-deposition of artifacts and their 

surrounding context to another location. Cultural 

properties, including camps, cabins, hunting and fishing 

sites, graves, and areas of particular religious or 

traditional importance, lose their integrity and thus their 

potential eligibility for the National Register of Historic

Places when they become degraded as a result of natural

or human disturbance processes, or when the people

who value these places can no longer access them, thus

losing their cultural connection to the site over time. 

Past Effects and Their Accumulation. Prior to 

European settlement, Native American and Alaska

Native tools, pottery, artwork, religious artifacts, and 

other cultural resources were subject only to the effects 

of the natural environment, such as the forming, 

deforming, and destroying of resources and sites, and

the effects of human activity, such as Native people

reusing found objects and materials. Later, as Europeans 

settled in North America, settlers collected, harmed, or 

destroyed cultural resources and sites and displaced 

Native peoples. Under the influence of inspired leaders,

however, traditional Native cultures have survived

(Garbarino and Sasso 1994, Zimmerman and

Molyneaux 1996). 

As settlement continued in the West, more lands were

developed and additional cultural resources were 

destroyed, taken, or lost. On public lands in the western 

U.S., grazing, timber removal, and mineral extraction

were activities that likely caused the greatest loss of 

cultural materials due to land disturbance, especially 

prior to the 1960s, when the National Historic 

Preservation Act (1966) and NEPA (1969) were passed. 

Historically, Alaska Natives were geographically

widespread and technologically capable people who

lived in dispersed, small communities based on family

and social connections (USDI BLM 2005c). Life in the 

northern subarctic revolved around the caribou, or 

reindeer, while the Inuit and Aleut hunted waterfowl

and marine mammals including whales, and fish. 

Alaska Natives had intermittent contact with Russian, 

American, British, and Norwegian traders, explorers, 

missionaries, and government representatives in the 

early 1800s. This contact intensified when commercial 

whaling north of the Bering Strait began in the 1850s.

Activities that have had the greatest effect on cultural

resources in Alaska, particularly in public lands along 

the Arctic Coast, are most likely linked to both oil

development and military activity, given that public 

lands on the Arctic North Slope were designated as a

Naval Petroleum Reserve in 1920. Alaska also was a 

theatre of war during World War II, and remnants of 

military bases and other Cold War-related facilities 

remain today and are considered historic resources. 

The inadvertent loss of cultural materials was slowed by

the passage of the National Historic Preservation Act

and NEPA, which mandated the identification of 

cultural resources potentially affected by developments

and mitigation for potential impacts. In addition, these 

developments resulted in the discovery of many

previously undocumented cultural resources. The 

Archaeological Resources Protection Act of 1979 added

additional protections for cultural resources on public or 

Native-owned lands. In addition, the Native American

Graves Protection and Repatriation Act of 1990 

provided protection for Native human remains, sacred 

objects, and associated funerary objects on federal and 

Native-owned lands. 

Future Effects and Their Accumulation. Cultural

resources are distributed unevenly across the western

states and Alaska. Areas with high probabilities of 

prehistoric and historic use are generally predictable, 

but specific subsurface cultural resources are often

BLM Vegetation Treatments Using Herbicides 4-227 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

unknown until some sort of disturbance occurs, making

it difficult to assess the cumulative impacts to cultural 

resources. The more surface and subsurface disturbance

that occurs, the larger the area affected and the greater 

the possibility that cultural resources will be impacted. 

Because of their surface or near-surface stratigraphic 

contexts, cultural resources are not well protected by 

soil and vegetation, and are vulnerable to any surfaceor subsurface-disturbing activity. 

The buildup of hazardous fuels and spread of noxious 

weeds and other invasive vegetation have increased the 

risk of wildfire and displacement of plants and animals 

that are important to Native peoples for their traditional 

lifeway values. Although fire is being reintroduced to

undeveloped areas in the West that were historically

burned by Native peoples to maintain early successional

plant species and improve habitat for game species, 

natural disturbance regimes have not been restored over 

much of the West. Encroachment by non-native species 

into natural ecosystems continues, to the detriment of

many native species of importance to Native peoples. 

Resource extraction, livestock grazing, motorized 

recreation, and other land disturbing activities would 

increase the potential for impacts to cultural resources. 

However, federal regulations and management policies 

that require the identification of cultural resources and

mitigation of impacts prior to most ground-disturbing

activities, including those associated with vegetation 

treatments are likely to remain in effect. An increase in

the number of acres treated to restore native vegetation 

and natural fire regimes, and to promote ecosystem

health could have short-term impacts on access to 

traditional resources by Native peoples. For example, 

herbicide use, wildland fire use, or prescribed fire could 

prohibit use of traditional areas by Native peoples until

areas are safe to enter and resources are suitable for use. 

Contribution of Alternatives to Cumulative Effects. 

As with paleontological resources, the potential for 

cumulative impacts to cultural resources from the use of 

herbicides and other treatment methods would be least 

under the No Action Alternative and greatest under the 

Preferred Alternative, based on the number of acres that 

would be impacted by ground-disturbing activities. 

Other treatment alternatives would be intermediate

between these two. It is anticipated that the use of 

wildland and prescribed fire and mechanical methods 

would have the greatest short term impacts on wildlife

and their habitat, and that impacts would be somewhat

in proportion to acres treated. Approximately twice as 

many acres would be treated using prescribed and 

wildland fire under the Preferred Alternative than under 

alternatives C, D, and E, and three times as many as

compared to the No Action Alternative. Acres treated

using mechanical methods would be similar among 

alternatives B, C, D, and E, and greater than for the No 

Action Alternative. 

Most ground-based equipment would disturb only the 

upper few inches of soil, and in many cases, would be 

confined to existing disturbed areas such as roadways,

trails, and ROWs. Cultural resources on the surface 

should be discovered during pretreatment surveys. All

treatment methods could cause indirect loss of cultural 

resources as a result of erosion and soil disturbance, but 

these effects should be minimal. Potential effects would 

be further reduced because the BLM has inventoried, or 

would conduct inventories for, cultural resources in

treatment areas to lessen the chance that they would be 

impacted by BLM vegetation treatment activities. Thus, 

there should be a negligible cumulative loss of cultural 

resources on public lands due to herbicide and other

vegetation treatment methods under all alternatives. 

Based on the number of acres treated using herbicide

and non-herbicide treatment methods, short-term 

impacts to plants that are important to Native peoples, 

as well as habitats used by fish and wildlife that are 

important to Native peoples, would be greatest under 

the Preferred Alternative and least under the No Action 

Alternative. However, as the long-term objective of

treatments is to restore native plant communities and

habitats, including those of traditional importance to 

Native peoples, the greatest benefits should accrue 

under the Preferred Alternative. In addition, since the 

herbicides proposed for use by the BLM are less 

harmful to non-target vegetation, fish and wildlife, and

humans than most currently-available herbicides used

by the BLM, and any future herbicides used by the 

BLM would also likely have low risk. The Preferred 

Alternative and Alternative D should have fewer 

cumulative impacts than the other herbicide-use

alternatives. 

As long as surveys and inventories were completed

prior to vegetation treatments in areas that are likely to

have cultural resources and lifeway values, the effects 

on those resources would be minimized. The accidental

discovery or damage to sites, presently known or

unknown, would affect those sites to some extent, but 

would also require measures to recover or record the 

remaining material, adding that information to the

archaeological record. 

The National Historic Preservation Act requires federal

agencies to take into account the effects of a proposed

BLM Vegetation Treatments Using Herbicides 4-228 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

action on properties included in, or eligible for, the 

National Register of Historic Places (also known as

historic properties) before approving or funding the

action. The Act also requires federal agencies to 

complete a cultural resources survey prior to federal 

actions and ground-disturbing activities that occur on

federal lands, and in some cases to survey private lands 

if there is a clear link between the land and the activities 

on federal lands. Surveys on private lands are most

applicable to cooperative projects involving federal 

agencies and private landowners to reduce hazardous 

fuels or invasive species on commingled land

jurisdictions. These surveys ensure that the protection of 

cultural resources goes beyond just the federal

component. The BLM’s guidelines and policies require 

that all effects to identified historic properties and other 

cultural resources identified during surveys be mitigated 

to the satisfaction of the land manager and the State

Historic Preservation Officer. Standard operating

procedures and agency guidance, as identified in 

manuals and handbooks (see Table 2-8 of the PEIS and

Table 2-5 of the PER), would reduce the likelihood of 

impacts to cultural resources.

Visual Resources 

Humans have had a profound effect on landscapes 

across the western U.S. and Alaska. While much of 

Alaska is still primarily a natural landscape with scenic

qualities that have not been changed substantially by 

humans, changes to the landscape in the lower 48 states

have been substantial (USDA Forest Service and USDI

BLM 1997; USDI BLM 2005c). Much of this change 

reflects past land management goals that focused on 

resource allocation, as commodity production took

precedence over custodial protection of land. Since the 

1970s, however, concern for ecosystem conditions has 

gained importance and is reflected by a greater effort on 

the part of federal, state, tribal, and other land stewards 

to restore ecosystems to near historic conditions. The 

objective of these efforts is to provide continued,

predictable flows of resources, including visual

resources, which contribute to both traditional and

current human demands and values (USDA Forest

Service and USDI BLM 1997). 

Past Effects and Their Accumulation 

Scenic quality, a measure of the visual appeal of the 

land, is rated based on landform, vegetation, water, 

color, adjacent scenery, scarcity, and cultural 

modifications. Sensitivity levels, which are measures of 

public concern for scenic quality, consider the types of

users of the area, the amount of use, public interest in

the area, adjacent land uses, and whether the area is 

classified as a special area. As landscapes are modified

by human factors, impacts to scenic quality occur, and

visual effects may accumulate on a particular landscape, 

based on levels of activity and degree of modification. 

For example, an area of high mining interest may 

display landscapes modified in form and color due to

waste dumps, open pits, and other facilities. Efforts to

mitigate these effects by designing waste dumps to

mimic landforms and rehabilitating with vegetation 

cover often reduce these effects concurrently and over

time to a point where the modifications may be

substantially unnoticeable in the long term. Contrary to

some common perceptions, lands in the western U.S. 

were not pristine wilderness prior to settlement by nonIndian emigrants, but ecological systems in which 

humans were an active component. American Indians 

used fire as a tool to manage vegetation to provide

better forage for game animals, to encourage growth of

plants used for food, and in ceremonial events (USDA 

Forest Service and USDI BLM 1997). 

As European settlers moved into the West, impacts to

the natural landscape accelerated. With population

growth came an increase in extraction of minerals and

other resources, agriculture, road construction, 

urbanization, and similar types of development that

have the potential to adversely impact the visual

qualities of the landscape. In addition, timber

harvesting, livestock grazing, the introduction of exotic

species, and the exclusion of fire have resulted in 

substantial changes to the landscape, succession and 

disturbance regimes, and associated vegetation

composition, structure, and pattern. 

The systematic exclusion of fire from western

ecosystems began in the early 1900s, with the intent of 

reducing threats to lives, property, and timber from fire. 

The result over time was a change from seral, fireadapted species to more fire-susceptible species that

often formed dense, unhealthy stands subject to largescale fires and disease outbreaks. Trees that are dead or 

dying as a result of insect infestations, and areas that

have been browned and blackened by wildland fire,

have become common visual characteristics of western 

landscapes during the last several decades. Where

human activities and wildland fire have disturbed the 

land, weeds and other unwanted invasive species have 

taken over and dominated landscapes (USDA Forest 

Service and USDI BLM 1997). It is estimated that

downy brome alone covers over 11 million acres in the 

West, and that leafy spurge covers 3 million acres

(Lajeuness et al. 1998). In addition, some invasive

BLM Vegetation Treatments Using Herbicides 4-229 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

species have spread into pristine areas independently of 

human activities or wildland fire because they compete

well and are adaptable. Regardless of whether these 

species are present because of anthropogenic or natural

processes, they may provide a seasonal visual contrast

to native vegetation, particularly downy brome, which

turns brown and dries during summer and fall when

most native plant species are still green. 

Future Effects and Their Accumulation 

The proposed vegetation treatments would affect visual 

resources by changing the scenic quality of the 

landscape. Vegetation treatments would kill or harm 

vegetation in the applied area, resulting in a more open, 

browned or blackened landscape until new plants were

to grow in the area. Treatment areas would vary in

terms of their visual appeal prior to treatment and their 

distance from human activity, as well as in terms of the 

resulting public sensitivity to the pre- and posttreatment visual character of the area. The effects of

vegetation treatments on the visual quality of the 

landscape would be most notable to travelers, 

sightseers, and residents for the first year to several

years following treatment, particularly in treated areas 

located near major roads or residential areas. 

The BLM’s treatment program would focus on nearterm vegetation management to improve the likelihood 

of moving toward or maintaining ecosystem processes 

that function properly over the long term (50 to 100

years or more from now) and require less treatment in 

the future to maintain. Through long-term passive 

management to reduce disturbance factors (e.g., 

limitations on OHVs, reduction in grazing activity), and

active management of forestlands and rangelands (e.g., 

use of fire, weed removal), landscapes that have been 

degraded in the past will gradually return to a mosaic of

plant community types that are more diverse and 

visually appealing. 

The BLM will continue to pursue initiatives and 

planning efforts to preserve and protect intact 

landscapes and restore degraded lands. In addition to the

initiatives listed above, the BLM, through land use 

planning, provides support to the National Landscape 

Conservation System, Congressionally-designated 

National Conservation Areas and Monuments, and 

wilderness and special areas, including Areas of Critical

Environmental Concern, by identifying appropriate 

goals, objectives, and management actions, with public 

input, to preserve and conserve special public land

values. 

Other federal, state, tribal, and local agencies, and 

private conservation groups have also increased their 

commitment to improving land health and therefore the 

visual characteristics of lands in the western U.S.,

including Alaska. Their ability to improve land health 

will depend on future funding and competing demands 

on land resources. Given the population growth in the 

western U.S., and the need to provide food and other 

resource commodities, visual impacts to lands in the 

western U.S. will continue to accumulate over the long 

term. At the same time, continual implementation of

Congressional and administrative policies that aim to 

conserve and enhance resources will provide some

countervailing effect to these long term changes. 

Contribution of Treatment Alternatives to

Cumulative Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to the 

visual qualities of public lands would be greatest under 

the Preferred Alternative, and least under the No Action

Alternative. The number of acres treated, and the effects 

to visual resources, would be similar under Alternatives 

D and E. Effects to visual resources under Alternative C 

would be intermediate between these alternatives and 

the Preferred Alternative. Short-term effects from

treatments and other human causes would accumulate,

but would be offset in the long term through the

countervailing effect of treatment success and 

improvement in the health and visual characteristics of 

the land. 

The risks to non-target vegetation from use of

herbicides could be less under Alternative E than under

the other herbicide use alternatives because ALSinhibiting herbicides would not be used. Because ALSinhibiting herbicides are effective at very low doses, any 

drift onto non-target vegetation could temporarily and

locally degrade the visual qualities of the affected area. 

Regardless of the alternative chosen, there would be a 

cumulative loss of visual resources. Longer term, these 

resources should improve, and the cumulative loss 

should slow. 

Wilderness and Other Special Areas 

The toughest challenge faced by the BLM and other 

federal wilderness land stewards is to keep wilderness 

wild, and (as stated in the Wilderness Act of 1964) 

“affected primarily by the forces of nature, with the 

imprint of man’s work substantially unnoticeable” 

(Hendee and Dawson 2002). The invasion of wilderness 

BLM Vegetation Treatments Using Herbicides 4-230 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

ecosystems by noxious weeds and other non-native 

plant species is of great risk to wilderness. Some species 

have been introduced to wilderness areas by pack stock, 

livestock that have been specifically brought into these 

areas, or wild horses and burros, which may travel in 

and out of wilderness areas. Native migratory wildlife, 

particularly birds, can be vectors for spreading nonnative seeds in their droppings or on their fur as they 

migrate through wilderness. Hikers may also bring in 

weed seeds on their clothing, 

Past Effects and Their Accumulation 

There are numerous threats to wilderness and special 

areas. These threats include: 1) exotic and non-native

species; 2) wildland fire suppression; 3) loss of water 

and deterioration in water quality; 4) fragmentation and 

isolation of wilderness as ecological islands; 5) loss of 

threatened and endangered species; 6) deterioration in 

air quality; 7) motorized and mechanical equipment 

trespass and use; 8) increasing commercial and public

recreation use; 9) adjacent land uses; and 10) 

urbanization and encroachment. Wilderness and special

areas comprise about 4% of lands in the U.S. As 

wilderness and special areas often represent the last

remaining pieces of many ecosystems, wild conditions, 

and natural landscapes that have either disappeared or 

been altered, these threats could have a profound effect

on the values of wilderness and special area values now

and in the future (Hendee and Dawson 2002). Loss of 

wilderness values associated with these threats has 

accumulated in the past and will continue to do so into

the future. 

Vegetation treatments primarily would address threats 1

through 6. Non-native species are a direct threat to 

wilderness. Noxious weeds often outcompete native 

species and spread rapidly, altering native ecosystems to

the detriment of wilderness. Secondary impacts can then 

result from vegetation management, such as use of 

mechanical methods and wildland and prescribed fire. 

Although treatments are usually implemented with the

intent of restoring native conditions, sometimes 

management actions cause other perturbations to the 

ecosystem. 

Fire prevention and suppression alter the natural fire 

frequency of fire dependant ecosystems, leading to

changes in ecosystem function and structure. As 

discussed in Vegetation, fire suppression has led to an 

accumulation of fuel loads, as well as forest stands 

dominated by dense concentrations of shade-tolerant 

trees, that contribute to larger and more intense 

wildfires. The use of fire and other treatment methods to

reduce hazardous fuels and the risk of wildfire should

improve ecosystem function on public lands. However, 

benefits to wilderness and special areas may be minimal 

because treatments are primarily targeted toward the

WUI and priority watersheds, rather than toward

wilderness and special areas. In addition, the public is 

often not receptive to the wildland fire use approach and 

use of fire and other treatments (especially mechanical) 

in these areas because they disturb the sense of solitude 

and wilderness. 

Water resources in wilderness and special areas are

threatened. In some cases, water storage facilities in

wilderness and special areas that were built before

passage of the Wilderness Act continue to be used

today. The quality of water in some wilderness streams 

may be affected by runoff from grazed areas and other 

pollutant sources within and outside of wilderness and

special areas. 

Because of their small size (42% of all wilderness areas 

in the U.S. are 10,000 to 50,000 acres, and the average 

size of wilderness areas administered by the BLM is

42,000 acres), most wilderness areas are ecological

“islands” that are vulnerable to outside influences. A

large fire or infestation of weeds can substantially alter 

the characteristics of wilderness. Without connectivity

to other wilderness areas, it is often impossible for lowmobility species, species with narrow habitat

requirements, or species with large home ranges to find

enough habitat within the wilderness to survive, or to

survive a major fire or other threat to survival. 

Polluted air is a threat to wilderness and special areas

because of its physical and biological impacts and its 

accompanying reduced visibility. The wilderness 

experience can be greatly diminished for visitors to

wilderness areas near urban sources of air pollution. 

Treatments involving the use of fire in wilderness areas 

would contribute to these impacts. 

The remaining threats listed can affect wilderness when

they weaken the natural conditions, processes, and

variability that were historically part of a wilderness or 

special area. Most of these threats will increase over 

time, and their impacts to wilderness resources and

values will accumulate. 

Future Effects and Their Accumulation 

The goal of wilderness fire management would be to

restore fire to its natural role in the wilderness 

ecosystem. Although benefits would accrue from fire

management―reduced hazardous fuels, improved

BLM Vegetation Treatments Using Herbicides 4-231 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

wildlife habitat, and a mosaic of vegetation types―the

intent of management would be to restore naturalness. 

In larger wildernesses, land managers also aim to

perpetuate landscapes and landscape processes. 

However, there are limits to fire management. As 

mentioned earlier, fires can impact regional air quality, 

escape from within the wilderness and harm people and 

property, and alter habitat to the detriment of threatened 

and endangered species. Mechanical and manual 

treatments can disturb solitude, while chemical

treatments can affect plant, animal, and human health

and impact the wildness of an area. 

In wilderness and special areas, where noxious weeds 

and other invasive species are limited to small areas, it

may be possible to control weed infestations with 

minimal tools. Introducing and establishing native

plants is also necessary to successfully manage weed

infestations and restore desirable plant communities 

(Jacobs et al. 1999). The degree of benefit would

depend on the success of these treatments over both the 

short and long term. Successful management would also 

require knowledge of the source of weeds and

implementation of controls to minimize future spread of 

weeds onto wilderness and special areas. 

Increasing recreational use of wilderness and special 

areas, which is projected to occur in the 21st century,

will put greater pressure on wilderness ecosystems, 

resources, and values, especially in areas located near 

major population centers. The BLM, Forest Service, and 

other federal land management agencies with 

wilderness protection responsibilities work closely to

protect and enhance wilderness values. However, 

disturbances outside of wilderness boundaries, 

including urbanization and agriculture, could further 

isolate some wilderness areas. Approximately 86% of 

wilderness acres administered by the BLM are

achieving wilderness character as specified by statute,

and about 73% of wilderness study areas are meeting 

their heritage resource objectives (USDI BLM 2006c). 

Although impacts to wilderness areas from altered fire 

regimes and spread of weeds should slow as treatments 

restore ecosystems and historic fire regimes, loss of 

wilderness values may be inevitable from other threats 

identified above, which are outside the agency’s control

and would continue to accumulate over the long term. 

Contribution of Alternatives to Cumulative 

Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to 

wilderness and special areas should be greatest under 

the Preferred Alternative, and least under the No Action

Alternative. The number of acres treated, and the effects 

to wilderness and special areas, would be similar under 

Alternatives D and E. Effects to these resources under 

Alternative C would be intermediate between these

alternatives and the Preferred Alternative. Short-term

effects from treatments and other human causes would

accumulate. However, a countervailing effect of longterm improvement in the function of wilderness and

special areas from successful treatments would offset

short-term losses. 

Several components of Alternative E pertain to

wilderness and special areas (see Appendix I of the 

PEIS). As discussed in the other resource sections, 

fewer acres would be treated under this alternative than 

under the other treatment alternatives. 

Under Alternative E, except for treatment of small 

infestations without motorized equipment, treatments 

would be prescribed within designated wilderness or

wilderness study areas only after the spread of invasive 

species from outside these areas was effectively halted. 

Under the other treatment alternatives, however, actions 

could be taken to control invasive species within

wilderness and special areas before controlling invasive 

species populations outside special areas. The BLM 

policy is to treat infestations where they are found and 

to prevent their further spread. By not treating an 

infestation in a wilderness or other special area until the

larger invasive species problem outside of the area is 

addressed, invasive species populations within

wilderness and special areas could grow beyond an 

effectively treatable level. 

The five herbicides (chlorsulfuron, imazapic, imazapyr,

metsulfuron methyl, and sulfometuron methyl) that

would not be approved under this alternative are some

of the least risky herbicides with respect to human

health (see Human Health and Safety section). In

addition, the ERAs predicted no risk to fish and

terrestrial wildlife from most of these herbicides

(chlorsulfuron, imazapic, sulfometuron methyl), and a 

few cases of low risk (imazapyr, metsulfuron methyl),

suggesting that the elimination of these herbicides 

would not likely benefit wildlife and could indirectly

harm wildlife in wilderness and special areas if more 

toxic herbicides were used in their place (see Wildlife 

Resources section). The other herbicides proposed for 

use by the BLM pose risks to non-target species that are 

similar to the risks associated with these five herbicides; 

therefore, it is uncertain whether this use restriction 

would actually reduce risk to non-target plants and 

animals. Thus, avoidance of ALS-inhibiting herbicides 

BLM Vegetation Treatments Using Herbicides 4-232 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

might provide few, if any, benefits to wilderness and

special areas and special area users. 

Regardless of the alternative chosen, there would be a 

cumulative loss of wilderness values and other special

area values. Over the long term, these values should

improve, and cumulative loss should be slowed. 

Recreation

The BLM’s long-term goal for recreation is to provide 

opportunities to the public for environmentally 

responsible recreation. Public lands host over 68 million

visitors annually. Over 4,000 communities with a 

combined population of 23 million people are located 

within 25 miles of public lands. Although much of the 

focus of the recreation program is on providing visitor 

services, the BLM’s most daunting challenge is to 

manage travel on public lands. Technological advances 

in modes of transportation, coupled with the explosive

growth of this activity, have created a management 

challenge to meet these needs while protecting land 

resources (USDI BLM 2005a). As identified during 

scoping, the public recognizes the potential for travel

access routes to spread weeds and for off-road travel 

activities to degrade land, leading to conditions that

favor the establishment and spread of unwanted

vegetation. 

Cumulative effects to recreational resources would

result from past and future activities that have long-term 

effects on solitude, naturalness, or primitive/unconfined 

recreation. Short-term or transient loss of an area’s 

naturalness and solitude from such impacts as 

temporary roads and noise from equipment would not 

be cumulative. Therefore, their contribution to the

cumulative impacts would be “momentary.”

Past Effects and Their Accumulation 

Although the BLM showed interest in recreational 

activities on public lands in the 1940s and 1950s, it was

not until 1961 that the BLM developed a recreation 

management handbook, and not until 1963 that the 

agency began an inventory to identify recreation sites 

and facilities (Muhn and Stewart 1988). Between 1963 

and 1968, the number of recreational visits to public 

lands more than tripled, and over the next decade visits 

nearly doubled to about 50 million visitors annually. 

With population growth in the western U.S. came an

increase in extraction of mineral and other resources, 

agriculture, road construction, urbanization, and similar 

types of development, which have altered western

landscapes and reduced the amount of land available for 

recreation. Timber harvesting and livestock grazing, the 

introduction of exotic species, and the exclusion of fire

have also resulted in substantial changes to the 

landscape, succession and disturbance regimes, and 

associated vegetation composition, structure, and

pattern that have impacted the quality of the recreation 

experience (USDA Forest Service and USDI BLM

1997). The effects of OHV use on soil and vegetation

were first brought to public attention in the late 1960s in

the California deserts, and eventually led to the

development of a management program for OHV use 

on public lands and establishment of the Imperial Sand

Dunes National Recreation Lands (Muhn and Stewart

1988). OHV and other travel-related activities continue 

to present challenges for land managers. 

Wildfires and the spread of weeds have led to the 

cumulative loss of recreational resources, although these 

losses are not irreversible. Wildfires are capable of

causing substantial damage to large areas of recreational 

resources and require long periods of time for recovery. 

During the recent wildfires that swept through the Great 

Basin, not only were traditional recreation activities

affected, but some special events were altered or

cancelled. Signs were destroyed, hiking and camping

areas burned over, wildlife and game displaced, and the 

scenery in the Great Basin marred (USDI BLM 1999). 

Noxious weeds and other invasive vegetation adversely 

impact the scenic and recreational qualities of public 

lands. They displace native vegetation to the detriment 

of fish and wildlife sought by wildlife viewers, hunters, 

and fishermen. Given the increase in the number and 

magnitude of wildfires during the past decade, and a 

weed population that grows by 1,000 acres a day on

public lands, losses of recreational opportunities 

continue to accumulate (USDI BLM 2006c). 

In recent years, several initiatives have been introduced 

to provide additional recreation opportunities, including

the National Landscape Conservation System, Great

Basin Restoration Initiative, Sage-grouse Habitat

Conservation Strategy, and the Prairie Grasslands 

Conservation Initiative. All of these initiatives are

designed to bring improved management to critical

natural systems under the BLM’s jurisdiction and to

address conservation at the landscape level. Continued

implementation of these initiatives will lead to 

improved recreational opportunities on public lands. 

Future Effects and Their Accumulation 

As urbanization of the West continues and the 

American public’s desire to recreate increases, public 

BLM Vegetation Treatments Using Herbicides 4-233 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

land recreation areas will experience greater usage. 

Although the satisfaction rating of visitors to public

lands is presently 94%, increased usage will inevitably 

increase the expectations of the public regarding the 

quality of their recreation experience (USDI BLM

2006c). The trend towards greater limits on public 

access to privately-held forestlands and hunting and 

fishing lands, as a result of concerns by landowners 

over public safety, litigation, vandalism, and damage to 

natural resources and commodity products (e.g., timber) 

produced on these lands, will put additional pressure on

public lands to meet the recreational needs of 

Americans. 

Vegetation treatments would have short-term

cumulative effects. There would be some scenic

degradation, as well as distractions to users (e.g., noise 

from machinery) from treatments. In addition, there 

would be some human health risks to recreationists 

associated with exposure to herbicides or smoke from 

fire. Some areas would be off-limits to recreation

activities as a result of treatments, for periods ranging

from a few hours to days, or even one full growing

season or longer, depending on the treatment. In most

cases, recreationists would be able to find alternative 

sites offering the same amenities or experiences, 

although a lessened experience could result from more 

concentrated use in these alternative sites. The effects of

herbicide treatments and fire use on fish and wildlife

could have indirect negative impacts on recreational

activities such as fishing, hunting, and wildlife viewing. 

For example, aerial application of an herbicide over a

large area could adversely affect these types of

recreation activities by harming or displacing fish and 

wildlife species. Vegetation treatments could also 

impact scenic views, particularly those located next to 

roads. The effects of vegetation management on the 

visual quality of the landscape are discussed further 

under Visual Resources. 

The BLM’s treatment program would focus on nearterm vegetation management to improve the likelihood 

of moving toward or maintaining properly functioning

ecosystems in the long term (50 to 100 years or more 

from now). Through passive management to reduce 

disturbance factors (e.g., closure of roads, reduction in 

grazing activity), and active management of forestlands 

and rangelands (e.g., through use of fire, weed

removal), the BLM hopes to restore a mosaic of plant 

community types that are more diverse and visually

appealing than those in lands that are not functioning 

properly. Vegetation treatments that reduce hazardous 

fuels, restore natural fire regimes, and control weeds

and other invasive vegetation would slow the loss of

recreational opportunities and the reduction in quality of 

the recreation experience. In addition, treatments that

reduce the risk of wildfire would reduce the likelihood

of recreationists being displaced from their favorite

hunting, fishing, and camping sites by wildfires. 

Treatments in public use facilities (e.g., campgrounds, 

visitor centers) could have short-term impacts, but

would enhance the visitor experience and ensure 

continued high-satisfaction ratings from visitors over 

the long term. 

Contribution of Alternatives to Cumulative 

Effects 

Based on the number of acres treated, short-term 

adverse impacts and long-term improvements to 

recreation resources on public lands would be greatest 

under the Preferred Alternative, and least under the No

Action Alternative. However, based on visitor use days, 

the number of visitors to public lands in states where the 

majority of treatments would take place, as a percentage 

of all visitors to public lands, is small in relation to the 

number of acres treated in those states (USDI BLM 

2006d), suggesting that effects to recreationists could be 

less than expected based on treatment acreage. 

Alternative E places greater emphasis on passive

restoration than the other alternatives. Passive 

restoration is often a critical first step in successful

restoration of degraded areas, since it entails halting 

anthropogenic activities that are causing degradation or

preventing recovery. OHVs are often cited as a factor 

contributing to loss of resource function and

degradation of scenic quality. By controlling OHV use, 

improvement in recreational values can be expected 

(Kauffman et al. 1997). However, the BLM would have 

to balance resource protection with the multiple use

requirements under FLPMA. As discussed in Chapter 2

of the PEIS, Vegetation Treatment Planning and

Management, passive restoration would be considered 

when developing restoration management plans, and 

would be used to the extent possible within the 

constraints of FLPMA. 

Regardless of the alternative chosen, there would be an

accumulation of loss of recreation resources. Longer 

term, these resources should benefit from the proposed

treatments and cumulative losses should slow. 

Social and Economic Values 

The western U.S., including Alaska, is more sparsely

populated than the rest of the U.S., containing about 

BLM Vegetation Treatments Using Herbicides 4-234 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

32% of the total U.S. population, but comprising 

approximately 65% of the total land area. However, 

population growth between 1990 and 2000 averaged 

over 16%, which was slightly higher than the national

average. Many of the western states exceeded the 

national average, with growth rates of 20% or higher 

during this time period. 

The western U.S. contains a large percentage of the 

nation’s minority populations, including over 60% of 

the nation’s Hispanics and American Indians, and over 

50% of the nation’s Asian/Pacific Islanders. In

particular, Arizona, California, New Mexico, and Texas 

contain large Hispanic populations, which comprise 

from 25% to over 40% of the total population in each of 

these states. Over 15% of Alaska’s population is

comprised of Alaska Natives. Federal agencies must be 

cognizant of the needs of these peoples when 

formulating management decisions. Executive Order 

12898, Environmental Justice, requires that federal

agencies address the potential for their actions to have

disproportionate effects on minority populations and/or 

low-income populations.

Population growth can stimulate economic growth and 

provide economic diversification. However, 

development in support of the growing population is 

encroaching on previously undeveloped areas near 

public lands. Growth also increases demands on public

lands for timber, minerals, livestock grazing, and other

commodities, and for recreation and roads. Because

public lands and open space are an important 

component of the western landscape, they are valued by 

westerners, who expect the BLM to manage public

lands to ensure their protection and enhancement. These 

conflicting demands can make it challenging for BLM

land managers to meet the multiple need requirements 

under FLPMA, while still preserving the natural 

characteristics of the landscape. 

Agency social and economic policy has long 

emphasized the goal of supporting rural and tribal 

communities by promoting the continued production of 

goods and services from public lands for those 

communities deemed dependent upon timber harvest

and processing, mineral extraction, and livestock forage. 

In addition, the BLM promotes the use of services 

provided by communities in support of BLM

management activities (e.g., firefighting and herbicide 

applications; USDA Forest Service and USDI BLM

2000, USDI BLM 2006c). 

Past Effects and Their Accumulation 

Population. Population growth rates in much of the 

West exceed those of the rest of the country. Nevada,

Arizona, Idaho, and Utah have been among the fastest 

growing states in the U.S. in recent years; between 1970

and 2000, Nevada’s population grew 309%, while the 

population of the rest of the country grew only 38%. 

This growth has placed increasing demands on public 

lands and other open spaces for recreation, and for 

providing the natural resources needed to support

growth in this region and in the world. 

Population growth has been highest in the WUI. 

Increasing migration to rural areas with a high quality of 

life is expected to continue as our country moves toward

a more service-based economy (USDA Forest Service 

and USDI BLM 2000). Growth in the WUI, however, 

has increased the risk of wildfire to people and property, 

and has impacted fish and wildlife habitat use and 

movements among public lands, rural areas, and the 

WUI. 

Environmental Justice. The western U.S. contains a 

large percentage of the nation’s minority populations.

These populations use public lands, and Native

Americans and Alaska Natives depend on public lands

for food and other traditional lifeway values. Many 

individuals in the forestry, mining, oil and gas, and

service sectors also derive work from public lands.

Native American, Alaska Native, and Hispanic 

populations increased at 2 to 4 times the rate of growth 

of the population as a whole during the past decade, 

suggesting that ever greater numbers of minorities use

public lands for pleasure and work and have the 

potential to be affected by vegetation treatments and 

other activities. 

Employment and Income. Over 23% of the nation’s 

employment opportunities, amounting to over 40 

million jobs, are located in the western U.S. (Table 3-

17). Employment in the trade and services industries 

accounts for over half of the total jobs. Industries related

to natural resources, such as agriculture and mining, are 

important sources of employment and represent nearly

one third of the nation’s agricultural services, forestry, 

and fishing jobs. Recreation and tourism associated with

public lands provide many jobs in the services sector. 

For example, an estimated $1.3 billion was spent by

hunters and anglers on hunting and fishing supplies 

while using public lands, and $1.7 billion was spent by 

wildlife viewers using public lands during FY 2005

(USDI BLM 2006d). Changing federal land uses have

affected the number and types of jobs associated with

BLM Vegetation Treatments Using Herbicides 4-235 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

public and other federal lands. For example, jobs

associated with the timber industry have declined in

recent years as the amount of timber harvested on 

federal lands has declined, while recreation employment

has increased. In addition, some industries, including 

timber harvesting, wood products manufacturing, and 

mining, have become more mechanized, reducing 

employment opportunities over time. Still, sales of 

timber, wood products, and non-wood forest products 

from public lands totaled approximately $36 billion, and 

leasable minerals generated $38.9 million, in FY 2005

(USDI BLM 2006c, d). 

Vegetation treatments have likely had minimal impact 

on employment and income in the West. However, 

increased federal budgets for wildland fire suppression 

and restoration of natural fire regimes have increased

employment and income in communities that have

supported these efforts. For example, $201 million was 

spent on hazardous fuels reduction treatments and $25 

million was spent by the BLM on Emergency Fire 

Stabilization and Rehabilitation Projects during FY 

2005 (USDI BLM 2006b, c). 

Perceptions and Values. Survey research shows 

differences in the opinions of residents of small, rural 

towns and residents of larger urban areas. Residents of 

urban areas tend to be more concerned about 

environmental protection, be less sympathetic to local

economic impacts, and have greater trust in the federal

government and environmental organizations than do

residents of rural areas (Harris and Associated 1995

cited in USDA Forest Service and USDI BLM 2000). 

Rural residents want less government intrusion into

their lives, and believe that current government policies 

tend to favor the environment too much over jobs. Rural 

residents seek a balance between the environment and 

jobs, enjoying the open spaces and clean air and water 

that public and other federal lands provide, while still

wanting jobs so that they and their children will be able 

to remain in the community. In recent decades, federal

land management policies have discouraged 

employment in some sectors (e.g., forestry), while 

promoting employment in others (e.g., oil and gas and

other mineral exploration and development). However, 

some of the values that rural westerners associate with

public lands, including clean air and native vegetation,

have been lost or degraded by the increase in the

number and severity of wildfires and the spread of

noxious weeds and other invasive vegetation. 

Revenues. Mineral leases, recreation and grazing fees,

and sale of timber are important sources of revenue for 

the federal government, although the contribution of 

each to the U.S. Treasury fluctuates in response to the 

national and global economy and national and local

policies. For example, the amount of revenue collected

from mineral leases and permits and recreation fees in

FY 2005 was about 4 times that collected in 1996, 

which reflected national energy policies, higher energy

prices, and increases in the recreating population. In 

contrast, in 2005 timber sale revenues were 4 times less, 

and grazing fee collections were about 15% less, than in 

1996 (USDI BLM 2006c). Timber sale reductions

reflect policies that have discouraged timber harvesting

on federal lands in response to concerns over the loss of 

forest wildlife, including the spotted owl, and forest 

habitat, including mature and old-growth forests.

Livestock use reductions reflect continuing resource 

damage and implementation of protections for

federally-listed plant and animal species (USDA Forest

Service and USDI BLM 2000). 

Expenditures. The BLM makes payments to counties 

to compensate them for the non-taxable status of federal 

lands in their jurisdiction. Generally, there is a per acre

payment associated with the county population, 

(payments in lieu of taxes, or PILT) and an additional

revenue-sharing payment based on revenues received

from the sale of timber, grazing fees, recreation fees,

special use permits, and other uses. There is concern in

counties over the potential loss of revenue if changes in

federal land uses cause a decline in timber harvest or 

other resource revenue. However, since 1996, payments 

have doubled, with the largest gains seen in states with

an active mining and oil and gas industry (e.g., Alaska 

and Nevada). 

Effects on Private Property. The value of rural 

property has increased in recent years as the population 

has increased and more people are able to move to rural

areas or buy second homes for recreation, retirement, or 

as investment property. In some areas, however, it is 

likely that recent wildfires have depressed home values,

either because of the future risk of fire, or because of 

land degradation associated with recent fires. 

Future Effects and Their Accumulation 

Population. None of the proposed treatment methods

being analyzed is likely to cause substantive changes to

existing patterns and trends in population or

demographic conditions in the western states. In

particular, it is unlikely that vegetation treatments would

either exacerbate or counteract the trend toward outmigration from small rural communities. Effects of

growth upon the landscape would continue to

accumulate. 

BLM Vegetation Treatments Using Herbicides 4-236 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Environmental Justice. As Hispanic, Native

American, and Alaska Native populations grow, the 

likelihood of these groups using public lands is likely to

increase. With increasing levels of treatment, the

possibility increases that any significant effects 

associated with vegetation treatments would

disproportionately affect these minority populations.

However, there are no data to suggest that there is any 

relationship between treatment areas and areas of low 

income or minority population, because treatment areas 

are widely scattered across the landscape. The BLM is 

proposing to use new herbicides that are less harmful

than many currently-available herbicides, and would 

likely use even safer herbicides in the future. This could 

reduce health risks to minority groups and to the general

public on a per-acre basis. 

Employment and Income. Based on an assessment 

done for the BLM and Forest Service for the Interior

Columbia Basin, recreation and tourism associated with

public lands are expected to show little change during 

the next decade (USDA Forest Service and USDI BLM

2000). If fuel prices remain high, fewer people may 

travel to public lands for recreation. Jobs associated

with the timber industry could increase as more timber

is harvested to restore natural fire regimes and reduce 

the risk of wildfire. Employment in mining and oil and 

gas industries would reflect the global economy. 

However, since many of the available and potential oil 

and gas and mineral resources in the U.S. are located on 

public lands, and since the need for these resources is 

likely to continue to grow, these industries will continue

to be important employers in the West. 

Vegetation treatments will have a minimal impact on

employment and income in the West. However, 

increased federal budgets for vegetation treatment

activities discussed in this PEIS, and wildland fire

suppression and restoration of natural fire regimes, 

would increase employment and income in

communities that provide support to these efforts. 

Perceptions and Values. The treatment alternatives 

would be associated with a range of stakeholder 

perceptions and values. For example, individuals who 

have an aversion to chemical use in the environment

could find all of the alternatives undesirable. 

Alternatively, individuals with a much greater concern

about wildfires or the effects of invasive species would

likely favor the most efficient means of attacking 

vegetation problems that could lead to catastrophic fires. 

As the number of acres treated could increase 3-fold 

from current levels, it is likely that both groups would

be affected by treatments. Some westerners have 

philosophical issues with government ownership and

management of large land areas, but they might be 

somewhat encouraged by plans to employ private

contractors for some of the treatment work and would

presumably favor the most efficient means possible to 

reduce fire risk to protect and maintain range 

productivity. 

Revenues. Certain commercial activities that occur on 

public lands could be adversely affected by vegetation 

treatments over the short term, such as OHV tours or

guide and outfitter operations. Vegetation treatments 

would not directly affect mineral resources and would 

be unlikely to cause significant reductions in BLM 

revenues generated from mineral leases. Vegetation

treatments to reduce fire risk in forested areas would

serve to protect commercially valuable timber from loss 

through catastrophic fire (USDA Forest Service and

USDI BLM 2000). 

Vegetation treatments could necessitate closures of

some sites to grazing activities during treatments and for 

a suitable recovery period afterward, usually two

growing seasons, both for effectiveness of the treatment

and, for some methods, for safety of the livestock. 

Treatments that require temporary rest from grazing

would force livestock operators to find alternative 

forage sources on private or other lands, which could 

lead to increased costs for the same amount of revenue. 

Livestock grazing on lands administered by the BLM

and Forest Service in the Interior Columbia Basin is 

projected to decline about 1% annually to ensure 

protection of rangeland habitats and special status 

species. It is likely that alternative sources of forage will

become scarcer as population growth leads to greater 

use of private pasturelands for crop production and

urban uses. 

Recreation-based businesses such as outfitters, bait

shops, OHV sales and repair shops, fish and hunting

shops, and outdoor gear and equipment rental shops are 

direct beneficiaries of recreation use of public lands. 

Other services such as gas stations, restaurants, and

hotels that are frequented by recreationists also benefit. 

Temporary closures of recreation areas due to

treatments would reduce revenues from these sources. 

As discussed above, recreation activity on public lands 

is expected to remain near current levels over the next 

decade. 

Expenditures. Vegetation treatments would require a 

large commitment of financial resources by the BLM, 

which would vary by treatment method, location, terrain 

and other factors. Using guidance from the Healthy 

BLM Vegetation Treatments Using Herbicides 4-237 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Forests Initiative, the National Fire Plan, and the 10-

Year Comprehensive Strategy Implementation Plan, the

USDA and USDI are proposing to spend $770 million

during FY 2007 for wildland fire management. Of this, 

nearly $200 million would be spent on hazardous fuels 

treatments and $24 million on land rehabilitation (USDI 

BLM 2006b). In addition, funding to conduct additional 

vegetation treatments would come from other program 

budgets within both agencies for program-specific 

treatments. These benefits would accumulate in the

communities where the funds were spent. Over $984 

million was spent by the federal government to control 

wildland fire during 2005, and based on modeling done 

for the cohesive strategy, even greater sums may be 

needed in the future to manage wildfire risk (Hann et al.

2002; USDI BLM 2006c). 

A major component of vegetation treatments, as 

proposed under the National Fire Plan and 10-Year 

Comprehensive Strategy Implementation Plan, is to

promote community assistance. In FY 2004, assistance 

with fuel hazard treatments, risk assessment plans, and

other wildfire preparedness was given to over 14,000

communities by the USDA and USDI. The agencies 

also initiated approximately $140 million in contractual 

actions. 

Effects on Private Property. Vegetation treatments 

could affect private property in the vicinity of public 

lands, particularly parcels adjacent to treatment areas.

Over the short term, there would be minor risks for 

property damage associated with treatments because it 

is possible that some treatment effects would extend 

beyond BLM boundaries onto private property. Long 

term, treatments that reduce the risk of loss of property 

to wildfire and improve the scenic and recreational

values of public lands should increase property values 

near public lands. 

Contribution of Treatment Alternatives to

Cumulative Effects 

The costs of prescribed fire range from $50 per acre to

$1,300 per acre depending on the location of the burn, 

but the cost in most circumstances would be about $290

per acre in the WUI, and $105 per acre outside the WUI 

based on average treatment costs during 2002 to 2005

(USDI BLM 2006c). The range of costs for mechanical 

treatments is also quite broad: from $100 to $600 per 

acre. Estimated costs for manual treatments range from

$70 to $700 per acre. Costs for biological treatment

vary depending on the type of organism employed. Use 

of domestic animals—cattle, sheep or goats—is quite

inexpensive, in the range of $12 to $15 per acre. Use of

biological control agents such as insects, nematodes,

mites or other pathogens is more costly, ranging from 

$80 to $150 per acre for ground applications and $150

to $300 per acre for aerial applications. As itemized in

the PEIS, the overall average cost per acre would be 

approximately $96 per acre for treatment involving both

ground-based and aerial applications. 

Based on the number of acres treated as discussed under 

treatment acreages in Chapter 2 of the PEIS, estimated

annual treatment costs would be greatest under the 

Preferred Alternative ($1.4 billion) and lowest under 

Alternative A ($420 million). Treatment costs for the

other three alternatives are estimated at $1.1 billion 

annually. Short-term adverse impacts in terms of costs 

and long-term improvements in terms of resource 

benefits would be greatest under the Preferred

Alternative, and least under the No Action Alternative. 

The other three alternatives would be intermediate

between these two. However, the contribution of 

treatment actions to the economy of the western U.S.

would be minor. 

Human Health and Safety 

When addressing cumulative impacts to human health 

and safety, the impacts to individuals conducting

vegetation treatments, as well as the effects of these

treatments (or lack of treatment) on the welfare of the

public must be considered. In addition, it must also be 

acknowledged that vegetation treatments to improve 

ecosystem resilience and promote the welfare of the

public are a cooperative effort among federal, tribal, 

state, and county land-management agencies, as well as

other local and private cooperators. The bulk of the 

responsibility, however, falls upon the BLM and Forest

Service because of the large amounts of public land they 

administer in the WUI. Finally, it must be taken into 

consideration that it will take many years before 

measurable results are achieved. 

Past Effects and Their Accumulation 

Risks to public health in areas in close proximity to

public lands include risks from occupational injury and 

death, from exposure to industrial pollutants, including 

pesticides and herbicides, from cancer, and from 

wildfire. 

Occupational Risks. In 2005, more than 29 million

nonfatal injuries were reported in the United States 

(CDC 2007a). Some chronic injuries are directly linked 

to the nature of the work performed. For example, 

vibration syndrome affects a large proportion of 

BLM Vegetation Treatments Using Herbicides 4-238 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

workers using chippers, grinders, chainsaws,

jackhammers, or other handheld power tools, causing

blanching and reduced sensitivity in the fingers. Noiseinduced hearing loss may also affect production workers 

who are exposed to noise levels of 80 decibels or more 

on a daily basis. Still, since 1992, the nationwide

nonfatal injury rate has declined by about 34% (CDC 

2007a). 

The occupational fatality rate in 2005 was 

approximately 4.0 fatalities per 100,000 employed. The

fatality rate for the agriculture, forestry, fishing, and

hunting sector was the highest, at 32.5 fatal industries 

per 100,000 workers. The mining sector had the second

highest rate, at 25.6 fatalities per 100,000 employed. 

The largest number of fatal work injuries resulted from

construction-related incidents, which accounted for 21% 

of workplace fatalities in 2005 (U.S. Department of

Labor Bureau of Labor Statistics 2007). In 1994, the 

occupational fatality rate was 5.3 per 100,000

employed. During the past decade, the trend in the 

fatality rate has steadily declined (Centers for Disease

Control and Prevention 2005). Deindustrialization and

greater emphasis on safety in the workplace are factors 

often cited as accounting for the downward trend in

occupation injury risk in the U.S. (Loomis et al. 2003).

Only minor injuries have occurred to workers involved 

in vegetation treatment activities on public lands during 

the past decade. As discussed under Human Health and

Safety in the PER, there are minor risks to workers from

treating vegetation, primarily associated with the 

operation of heavy equipment and power tools, and the 

use of fire and herbicides. Workers would follow SOPs 

to minimize the risk of injury when treating vegetation, 

including using protective equipment, and using 

herbicides with low health risks. 

Cancer Risks. Based on the data shown in Table 3-25, 

cancer accounted for between 13% and 33% of all 

deaths in the treatment states in 2002-2003. Nationwide, 

cancer accounts for approximately 23% of all fatalities 

(National Center for Health Statistics 2007b). In the 

western U.S., cancer mortality rates are generally 

highest in counties in western and southern Nevada and 

northern California, and lowest in counties in Utah, 

central Colorado, and northern New Mexico (Devesa et

al. 1999). Cancer rates increased during most of the 20th

century, but began to decline in the 1990s for the 

leading causes of cancer (Wingo et al. 2005). Improved

detection and treatment, along with healthier lifestyles, 

are believed to account for the declining rates. 

Several herbicides used by the BLM could cause cancer 

in workers and the public based on exposure scenarios 

evaluated in HHRAs done for earlier EISs. These 

include 2,4-DP, asulam, atrazine, bromacil, and

simazine (see Tables 4-31 and 4-32). With the exception 

of atrazine, cancer risks were only predicted for 

accidental exposure scenarios. In the case of atrazine,

cancer risks were predicted for maximum and accidental

exposure scenarios (USDI BLM 1991a). Except for 

bromacil, these chemicals have not been used by the 

BLM since at least 1997, and bromacil is used on less 

than 1% of the total acreage treated using herbicides. 

Exposure to Pollutants. Exposure to industrial

pollutants and toxic chemicals, including those

produced by industries operating on public lands (e.g., 

mining, oil and gas), is a public health concern. The 

Toxics Release Inventory (TRI) is the principal source

of data for analyzing the amount of toxic chemicals 

used in American industry. Although data on recent

trends in toxic emissions are confusing due to differing

data reporting requirements, the overall trend in toxic

emissions since 1988 is downward, a sign of the 

increasing efficiency and dematerialization of our 

economy (Hayward 2005). 

Air pollutants have the potential to impact the health 

of people using or living near public lands. The 

USEPA has identified criteria pollutants that affect air 

quality and human health (see Air Quality in Chapter 

3). Despite increases in human population and

industrialization, emissions of principal air pollutants 

in the U.S., after peaking in the 1970s and early

1980s, have generally declined or held steady during

the past 2 decades due to more stringent air quality 

regulations and improvements in pollution control 

technology (USEPA 2005). 

Particulate matter is the principal pollutant of concern, 

from a public health perspective, for activities 

occurring on public lands. Nationwide, emissions of 

particulate matter from all sources have trended 

downward since the 1970s. However, PM emissions 

have shown a close relationship with the number of 

acres burned annually by wildfire. Since 1990, PM

emissions associated with wildfire have ranged from

145,000 tons in 1995 to 1.2 million tons in 2002; the 

number of acres burned by wildfires in 1995 was onethird the number of acres burned in 2002. The level of 

PM associated with slash and prescribed burning, 

however, has trended downward since the 1970s, and 

in 2001 (165,000 tons) was about half the level of the 

early 1990s. Based on an estimate of emissions 

generated by current vegetation treatment activities 

BLM Vegetation Treatments Using Herbicides 4-239 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

(primarily fire and mechanical treatments; see Table

4-4 in PER), BLM treatment activities have accounted 

for less than 0.5% of criteria pollutant emissions 

nationwide. 

Herbicides contain chemical compounds that are 

harmful to human health. Most of the herbicides used

by the BLM do not pose a risk to human receptors when

applied at the typical application rate. At the maximum 

application rate, however, more herbicides, in a greater 

number of exposure scenarios, have the potential to

adversely affect human health. Aerial applications of

herbicides pose a greater risk to the public due to offsite drift than ground applications, as herbicides applied

at greater distances from the ground are able to drift 

farther from the target application area. Spot 

applications would be less likely to pose a risk to 

downwind receptors than boom/broadcast applications. 

However, spot applications would be more likely to

pose a risk to workers charged with applying the

herbicide through dermal contact. 

In recent years there has been concern regarding the 

potential for herbicides used by the BLM or other 

federal, state, or private applicators to contain

compounds that are endocrine disruptors. According to 

the World Health Organization (2002), endocrine 

disrupters have been defined as exogenous substances 

that alter function(s) of the endocrine system and 

consequently cause adverse health effects in an intact 

organism or its progeny, or in (sub)populations. 

Endocrine disrupters interfere with the functioning of

the endocrine system in at least three possible ways: 

• By mimicking the action of a naturallyproduced hormone, such as estrogen or 

testosterone, and thereby setting off similar 

chemical reactions in the body; 

• by blocking the receptors in cells receiving the

hormones (hormone receptors), thereby 

preventing the action of normal hormones; or 

• by affecting the synthesis, transport, 

metabolism and excretion of hormones, thus 

altering the concentrations of natural 

hormones. 

During the toxicity review for the HHRAs, no

endocrine disrupting effects were noted. The toxicity

review consisted of a literature search and a review of 

USEPA registration data. In order to further evaluate 

whether any of the BLM herbicides have endocrine 

disruption effects, the BLM conducted a search of

endocrine disrupter databases, including sources from 

the U.S., the European Union, and Japan. The databases 

included official government lists and lists published by 

concerned citizen groups, such as the Pesticide Action 

Network. The results of this search are presented in 

Table D-5 in Appendix D. With the exception of 2,4-D 

and diuron, none of the BLM herbicides were included 

among those associated with endocrine disrupting 

effects. As shown in the table, diuron and 2,4-D are 

listed by the European Commission Directorate-General

for the Environment (2000) as Category 2 chemicals, 

meaning that there is evidence of the potential for the 

listed chemical to cause endocrine disruption. Diuron

only appeared on a single list, so there is some

uncertainty within the scientific community about this 

chemical’s status as an endocrine disruptor. 

Several other lists include 2,4-D as a potential or 

probably endocrine disrupting chemical. However, the 

Endocrine Disruptor Knowledge Base supported by the 

U.S. Food and Drug Administration’s National Center 

for Toxicological Research indicates that there are no 

reports in the scientific peer-reviewed literature of 2,4-D 

acting as an estrogen receptor binder. 

The USEPA Health Effects Division (HED) HHRA that

was used in the RED, and a correction to the HED 

HHRA provided by the 2,4-D Industry Task Force, 

were reviewed. The HED HHRA and Task Force

correction provided additional detail regarding the 

studies used to test for potential endocrine effects. In 

general, the studies cited as showing evidence of 

endocrine disruption effects were conducted using

extremely high doses of 2,4-D, where often renal 

saturation or other systemic effects were noted. The 

findings of these studies, therefore, do not indicate that

2,4-D has selective toxicity to the endocrine system. 

In the health risk assessment conducted to support the 

reregistration of 2,4-D (USEPA 2004c), the USEPA 

concluded that there is not sufficient evidence that 2,4-

D is an endocrine disrupting chemical. The USEPA did

not conduct the health risk assessment using endocrine 

disruption endpoints. Since the current studies that 

showed evidence of endocrine effects were tested using 

doses above renal saturation, the USEPA recommended 

formal testing of 2,4-D for endocrine endpoints. 

However, there is no standard protocol for 

determination of endocrine effects of chemicals. 

The lack of a standardized and broadly accepted set of 

protocols for identifying and quantifying potential

endocrine effects has very important implications. The 

absence of such a test has contributed to the 

development of several, potentially conflicting, 

BLM Vegetation Treatments Using Herbicides 4-240 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

summaries of potential endocrine disruptors. As 

importantly, in the absence of an agreed upon process to

quantify dose-response relationships, quantitative risk

assessments are difficult and highly uncertain. 

Nationwide, the annual amount of herbicide use has 

declined from an estimated 620 million pounds of active 

ingredient in 1982 to 553 million pounds in 2001, 

although the amount of herbicide use has remained 

relatively steady since the late 1980s. The amount of

other pesticides used has also declined by about 15%

during the same period (Donaldson et al. 2004). 

Vegetation treatment activities by the BLM, Forest

Service, and other agencies, for agricultural and other 

uses, have contributed to the release of harmful

materials into the environment. As discussed above, 

prescribed fire use has steadily increased during the past

decade and has contributed to PM emissions. Heavy 

equipment, transport vehicles, and power tools have 

also contributed minor amounts of PM and other 

pollutants into the atmosphere. Herbicide use by the 

BLM, Forest Service, agricultural operations, and others 

has steadily increased, but these users have emphasized

the use of less toxic herbicides that have shorter halflives and do not bioaccumulate. Users have also kept 

application rates as low as possible, to minimize the 

amount of toxic material released into the environment

while still meeting treatment goals. In addition, these 

users have increased passive treatments and nonherbicide treatments, such as biological control, to

minimize the use of herbicides in vegetation control. 

Risks from Wildfire. Wildfires cause loss of life and

property. According to the National Interagency Fire 

Center (2005), 12 people died from wildland fire 

accidents in 2005. During 1999 to 2005, 149 individuals

died from wildland fire accidents, including agency

personnel, contractors, volunteers, and private 

individuals. The largest number of fatalities was 

associated with use of a vehicle or ground-based

mechanical equipment (23.8%), heart attacks (22.7%),

use of aircraft (22.3%), or burnovers (20.2%). During

2005, wildland fires resulted in the loss of 240 primary 

structures, many on or near BLM- or Forest Serviceadministered lands (USDI BLM 2006c). 

Growth in the western U.S. has exceeded that of the rest

of the country, and while the region remains more rural

than the rest of the country, over 23 million people now 

live within 25 miles of public lands (USDI BLM 

2006c). As wildfires have become more severe, the 

associated risks to life and property within the WUI 

have increased. Because of concern about this risk, the 

Department of the Interior stepped up efforts to reduce 

hazardous fuels in the WUI from 164,000 acres in 1991

to over 506,168 acres in FY 2005. Despite these efforts, 

over $91 million was spent by the BLM in 2005 on fire 

control, much of it in the WUI (USDI BLM 2006c). 

Future Effects and Their Accumulation 

Occupational Risks. It is projected that incidence of 

occupational injury and death will continue to decline as 

our nation moves to a more service-oriented economy. 

Occupations with higher risk of injury and death will

continue to be associated with rural areas and public

lands; risks in these areas will likely be greater than in 

more urbanized areas. However, continued

improvement in equipment and emphasis on workplace 

safety should help to reduce risks of occupational injury 

and death in the West. 

Out of the various treatment activities, mechanical

treatments and herbicide use pose the greatest risk to

worker health. The number of acres treated using 

herbicides and mechanical methods will increase 3-fold 

under the Preferred Alternative. Thus, risks of injury 

associated with equipment could also increase 3-fold,

and permanent injuries and loss of life could

accumulate. It is likely that risk to workers from

application of and exposure to herbicides would not be 

as great as at present, since the BLM would place the 

greatest emphasis on use of herbicides that have low 

risk to humans. For example, three of the four

herbicides proposed for use by the BLM would pose 

essentially no risk to humans under exposure scenarios 

modeled in the HHRA. 

Cancer Risks. Cancer rates have declined for over a

decade, and are likely to continue to do so with 

improvements in lifestyle and our ability to recognize 

and treat the underlying causes. Cancer risks for 

workers conducting fire and herbicide treatments on 

public lands could increase because more acres would 

be treated by these methods. However, risks to workers 

would be lessened by improvement in equipment and 

treatment technologies and use of newer herbicides, 

including those proposed for use in this PEIS, that pose 

no known cancer risk. 

Exposure to Pollutants. The trend in pollutant 

emissions is expected to continue to decrease

nationwide. For example, the USEPA projects that 

emissions from automobiles will decline by more than 

80% over the next 25 years as Americans shift to more

fuel efficient and less polluting vehicles and use fuels 

that have been developed to reduce emissions. Industrial

BLM Vegetation Treatments Using Herbicides 4-241 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

pollution is also expected to decline as our economy

becomes more service-based (Hayward 2005). 

The proposed increase in use of fire by the BLM, Forest

Service, and other federal and state land management

agencies to restore natural fire regimes and reduce 

hazardous fuels could increase the amount of smoke, 

and therefore the incidence of health effects associated

with PM and other harmful constituents of smoke in the

West. The Forest Service modeled several scenarios to 

predict the long-term effect of treating more acres 

and/or targeting treatments in the WUI on regional air

quality and the condition of the land (USDA Forest

Service and USDI BLM 2000). The model assumed that 

in the WUI, where air quality and other considerations 

could limit the use of fire, mechanical and hand cutting

would be important treatment options, in addition to use 

of fire. According to the model, air quality would 

generally improve as the number of acres treated 

annually increased, and improvement in air quality 

would be most noticeable for treatments targeted at high 

priority western U.S. WUI landscapes. Thus, the 

proposed action, which includes over 4.3 million acres 

of fire use and mechanical treatments, in addition to 1.7 

million acres of treatments using other methods, would

be expected to provide greater improvement in 

ecosystem function and air quality than is projected 

under current treatment methods (see Air Quality). 

Risks to the public and workers on or near public lands 

from exposure to herbicides could increase as a result of 

the increase in herbicide use. To reduce this risk, the 

BLM would primarily use herbicides that have low risk

to humans, including new herbicides proposed for use 

as part of this PEIS, and would continue to identify and 

make available to field offices herbicides that have

lower risk to workers than currently-available

herbicides. 

Risks from Wildfire. In response to the threats of 

wildfire and invasive vegetation and noxious weeds, the 

President and Congress have directed the USDI and 

BLM, through implementation of the National Fire 

Plan (USDI and USDA Forest Service 2001), and the 

Healthy Forests Restoration Act of 2003, to take more

aggressive actions to reduce catastrophic wildfire risk

on public lands. The intent of these actions is to protect

life and property, and to manage vegetation in a manner 

that provides for long-term economic sustainability of 

local communities, improved habitat and vegetation 

conditions for fish and wildlife, and other public land

uses. 

Treatment activities to reduce fire risk include timber

harvest, thinning, prescribed fire, fuel reduction 

activities, greenstrips, brush reduction, and effective

suppression efforts. While prescribed fire is not without 

risk, it is generally safer to burn under the controlled 

conditions of prescribed fire than to chance a wildfire

when fuels are extremely dry and weather conditions 

are unfavorable. 

The proposed treatment program would restore natural

fire regimes and encourage the growth of native 

vegetation that is more resilient to wildfire, reducing the 

risk of wildland fire. If plant community structure,

species composition, and disturbance regimes return to 

near historical ranges, then disturbances should have

effects that are similar to historical effects, which would 

be less severe, and result in less fire danger, than at

present. Because of the limitations on the types and 

amounts of treatments that can occur in the WUI, it may

be more difficult to restore natural fire regimes on lands 

in the WUI than on non-WUI lands, but over the long

term, benefits to the WUI should accrue and the loss of 

life and property associated with wildfire should slow or 

begin to decrease (USDA Forest Service and USDI 

BLM 2000; USDI BLM 2006c). 

An assessment of risks to people and property from

varying levels and types of treatments was done for the 

cohesive strategy. Assuming funding levels remained

static and two-thirds of treatments were targeted for the 

WUI, risks to people and property would remain near 

current levels after 15 years (Hann et al. 2002). If more 

funding was provided, it would be possible to 

substantially reduce the risk that life and property would 

be lost. 

Contribution of Treatment Alternatives to

Cumulative Effects 

As discussed above, short-term risks to human health

are related to the types of treatments and methods used, 

and the number of acres treated. Based on number of 

acres treated, the greatest risk to human health would 

occur under the Preferred Alternative, and the least risk

would occur under the No Action Alternative. The other 

alternatives would likely be intermediate between these

two. 

Risks associated with fire use and mechanical, manual, 

and biological control treatments would be similar for 

the four action alternatives, which differ primarily in the

types of herbicides available for use and number of 

acres treated. Risks associated with herbicide use could 

be less under alternatives C, D and E than under the

BLM Vegetation Treatments Using Herbicides 4-242 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Preferred Alternative, because fewer acres would be 

treated and aerial spraying would be prohibited 

(Alternatives C and D) or discouraged (Alternative E). 

The risk of off-site drift would be less under these 

alternatives, with no risk under Alternative C. 

Alternative E would prohibit use of ALS-inhibiting 

herbicides, some of which have less risk to humans than 

herbicides that would be allowed under this alternative. 

About one-third as many acres would be treated using

herbicides under the No Action Alternative, compared

to the other alternatives. However, the BLM would be 

able to use several herbicides (2,4-DP, asulam, atrazine,

fosamine, mefluidide, and simazine) under the No

Action Alternative that pose high risks to human health, 

but that would not be available for use under the other 

herbicide treatment alternatives. 

Alternative E places greater emphasis on passive

restoration than the other alternatives and would result

in fewer risks or injuries to workers due to less 

emphasis on the use of mechanical, herbicide or fire 

treatments. Alternative E also focuses more hazardous 

fuels treatments in the WUI, and encourages practices to

reduce vegetation near homes and to develop a 

defensible space in the WUI to reduce risks to people

and property from wildfires. 

Regardless of the alternative chosen, there could be an

accumulation of injury or loss of human life from 

treatments, and there would be a cumulative loss of

property from wildfires. Over the long term, restoration

of natural fire regimes and improvement in ecosystem 

health should reduce risk to human health from 

activities originating on public lands and affecting

public land users or those living near public lands. 

Unavoidable Adverse Effects 

This section summarizes the unavoidable adverse 

effects that would occur under the actions considered in 

the PEIS and PER. Unavoidable adverse effects would 

primarily be associated with the use of herbicides and 

fire. 

Air Quality 

An increase in emissions of air pollutants would occur 

as a result of all the action alternatives. However, air 

quality standards would not be exceeded under any of

the alternatives (see Air Quality Modeling for BLM 

Vegetation Treatment Methods [ENSR 2005m] and

Annual Emissions Inventory for BLM Vegetation

Treatment Methods [ENSR 2005a] that are found on the

CD that accompanies the PEIS and on the BLM website 

at http://www.blm.gov). 

Soil Resources 

Regardless of the method used to remove vegetation,

vegetation treatments would potentially result in 

adverse short-term impacts through increased erosion

and reduced water infiltration, leading to loss of soil and

reduced soil productivity. The degree of these effects 

would vary by region, depending on climate, landform, 

hydrology, soil, vegetation, and land use. In many

western U.S. regions, the combination of hydrologic 

characteristics, steep topography, and slow vegetative 

growth make soil erosion a serious concern (Kennard

and Fowler 2005). 

Vegetation treatments could disturb biological soil 

crusts, potentially reducing soil quality and ecosystem

productivity. The extent of impacts to biological soil

crusts would be dependent on the intensity and kind of 

disturbance and the amount of area covered. The 

duration of the effects would vary, but recovery of 

biological soil crusts typically takes much longer than

the recovery of vascular vegetation. 

Water Resources and Quality 

An increase in soil erosion and surface water runoff 

could result from vegetation removal, which could lead

to stream bank erosion and sedimentation (Ott 2000). 

Rates of runoff would be influenced by precipitation

rates, soil types, and proximity to the treated area. All 

vegetation removal activities could disturb the soil and 

reduce the amount of vegetation binding to soil, 

potentially causing erosion and increased sedimentation. 

The removal of vegetation would decrease the amount 

of rainfall captured by plants, detritus, and soil,

potentially leading to increased stormwater flows,

runoff velocity, and sedimentation. Herbicides have the 

potential to directly impact surface water quality or 

leach through the soil and impact groundwater quality. 

Wetland and Riparian Areas 

An increase in soil erosion and surface water runoff 

could result from vegetation removal, and could lead to 

streambank erosion and sedimentation in wetlands and

riparian areas (Ott 2000). Rate of runoff would be 

influenced by precipitation rate, soil type, and proximity

to the treated area. All vegetation removal activities 

could disturb the soil and reduce the amount of 

vegetation binding to soil, potentially causing erosion

and increased sedimentation of wetlands and riparian

BLM Vegetation Treatments Using Herbicides 4-243 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

areas. Sediments can impact plants within wetland and

riparian areas by reducing the amount of sunlight

reaching plants and slowing or stopping plant growth. 

The removal of vegetation would decrease the amount 

of rainfall captured by plants, detritus, and soil,

potentially leading to increased stormwater flows and 

runoff velocity in both ecosystems. Increased

stormwater runoff can scour wetlands, modify their 

morphology, and affect the distribution and abundance

of aquatic organisms within the area. Decomposition of 

treated non-target aquatic vegetation could result in 

oxygen depletion. Siltation of wetlands could reduce 

water quality and the amount of oxygen available to 

aquatic organisms. In addition, siltation could reduce 

the acreage of wetland and riparian habitat. 

Vegetation 

The proposed vegetation treatments would cause 

unavoidable short-term disturbances to plant 

communities by killing both target and non-target

plants. The extent of disturbances would vary by the 

extent and type of treatment. In many cases, the 

treatments would return all or a portion of the treated

area to an early successional stage by freeing up 

resources such as light and nutrients for early

successional species, such as annual grasses and forbs. 

Fish and Other Aquatic Organisms 

Removal or alteration of terrestrial vegetation, either 

through treatment activities or natural occurrences such

as catastrophic fire, could result in an increase in soil 

erosion and surface water runoff, potentially leading to

streambank erosion and sedimentation in aquatic 

habitats (Ott 2000). Sediments can harm spawning

habitat, make foraging more difficult for aquatic 

organisms, and harm breathing organs of aquatic 

animals. The effects of catastrophic fire in watersheds 

would be ameliorated through timely emergency 

stabilization activities that are usually implemented

within the same season as the fire, and are designed to 

minimize erosion and siltation. 

Wildlife Resources 

The proposed vegetation treatments could kill or harm 

wildlife, and cause unavoidable short-term adverse

impacts to wildlife habitat and behavior. The extent of 

these disturbances would vary by the extent and type of 

treatment. In general, greatest risks would be associated

with the wildland fire use, prescribed fire, and herbicide 

treatments. If treatments were successful, species using

sites prior to treatment could be displaced by species 

better adapted to the restored sites. 

Many species that use wetlands have evolved lifehistory strategies that depend upon stable conditions 

(i.e., stable water quality and quantity). For example, 

vegetation removal resulting in increased water flows to

wetlands during the spring could flood the breeding

sites of aquatic organisms that breed or lay eggs in

moist soil, harming or killing eggs or juveniles. 

Livestock 

The proposed vegetation treatments could temporarily 

affect non-target vegetation that might provide forage, 

shelter, or other life requisites for livestock. Livestock

could also be adversely impacted by herbicide 

treatments. Livestock, which consume large quantities 

of grass, are at greater risk for harm than smaller 

wildlife or wildlife that feed on other herbaceous 

vegetation, seeds, or fruits, because herbicide residue is

higher on grass than it is on these other plants (Fletcher 

et al. 1994; Pfleeger et al. 1996; see Appendix C). These 

potential impacts are usually mitigated because 

livestock can be removed from areas scheduled for 

treatment. 

Wild Horses and Burros 

The proposed vegetation treatments could adversely 

affect wild horse and burro populations by killing or 

harming non-target vegetation that might provide

forage, shelter, or other life requisites for wild horses 

and burros. Wild horses and burros could also be

impacted by herbicide treatments. Because these

animals likely consume large quantities of grass, they

are at greater risk for harm than smaller wildlife or

wildlife that feed on other herbaceous vegetation, seeds, 

or fruits. However, harmful doses of herbicide would be 

unlikely unless an animal were to forage exclusively 

within the treatment area for an entire day. Therefore,

smaller treatments may be most appropriate in herd

management areas in certain cases involving use of an 

herbicide with a demonstrated risk to herbivores from 

the consumption of contaminated vegetation. In some 

cases, treatment areas can be designed to exclude use by 

wild horse and burros to reduce the likelihood of 

adverse impacts to these animals. 

BLM Vegetation Treatments Using Herbicides 4-244 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Paleontological and Cultural Resources 

Paleontological Resources 

The loss of paleontological resources has the potential

to be adverse, especially if it results in the loss of 

scientifically important fossils. However, if surveys and

inventories were conducted in areas where grounddisturbing activities were proposed to occur, and 

treatments avoided paleontological resource sites, the 

incidence of impacts would be greatly reduced, and any 

impacts that did occur would be minimal. Use of SOPs 

would reduce the likelihood of impacts to

paleontological resources. 

Cultural Resources and Traditional Lifeway 

Values 

Cultural resources are nonrenewable, so any effects to

these resources would have some importance. Because 

the exact locations of all potential cultural resources 

sites are unknown, their disturbance cannot be entirely 

avoided. There are cultural resources on public lands

that may relate to the entire span of human occupation,

including locales used by the first humans to enter the 

Western Hemisphere. Historic and prehistoric sites 

representing varied ages, cultures, and functions, may 

be located anywhere within the treatment area. Because

soil forms slowly in the Arctic, cultural resources that

are thousands of years old may be near the surface at

Arctic sites. If surveys and inventories for cultural

resources were conducted in areas where vegetation

treatments were proposed to occur before the work 

began, effects to cultural resources in these areas could

be reduced or avoided. Timely intervention following

the discovery of cultural resources would effectively

mitigate many effects, either through site avoidance or 

data recovery. Archaeological excavation to recover 

scientific data under the terms of an appropriate data 

recovery plan could result in the partial or total

destruction of the site, although the recovered data 

would effectively mitigate for this destruction. 

In many areas of the West, noxious weeds and other 

invasive vegetation grow together with more desirable 

vegetation used for traditional lifeway values such as 

food or basketweaving. Vegetation treatments in these 

areas could harm desirable plants, discourage or 

prohibit Native peoples from using these areas, or in the 

case of herbicides, potentially harm Native peoples 

harvesting plant materials in treated areas. 

Visual Resources 

The proposed vegetation treatments would not result in

unavoidable adverse effects to visual resources over the 

long term. Over the short term, vegetation treatments 

would kill or harm vegetation in the applied area, 

resulting in a more open, browned or blackened 

landscape until new plants were to grow in the area. 

While these effects are unavoidable, they are considered

short-term impacts, as the vegetation would recover and 

lead to improved natural conditions. Treatment areas 

would vary in terms of their visual appeal prior to

treatment and their distance from human activity, as 

well as in terms of the resulting public sensitivity to the 

pre- and post-treatment visual character of the area. The

effects of vegetation treatments on the visual quality of 

the landscape would be most noticeable to travelers,

sightseers, and residents for the first year to several

years following treatment, particularly near major roads 

or residential areas. 

Wilderness and Special Areas 

The effects of fire on wilderness and special areas 

would depend on a number of factors, such as the

vegetation on the site, the condition of the site, the

weather, fuel and soil moisture conditions under which

the fire occurred, and the particular unique quality of the

site that requires special management. In general, sites 

with special qualities that could be destroyed by fire

would be the most likely to experience significant 

adverse effects from fire treatments. 

Use of mechanical treatment methods would adversely

affect wilderness areas and wilderness study areas

because vehicles and heavy equipment are incompatible

with the “unspoiled” nature of wilderness. For this 

reason, mechanical treatments would only be allowed

on a very limited number of sites where no other 

method was feasible (e.g., tamarisk removal) and in the

few areas where mechanical treatments have occurred in

the past and repeat treatments are required.

Use of herbicides to treat undesirable vegetation could

potentially affect the condition of wilderness areas and

wilderness study areas by killing non-target native 

vegetation through imprecise application and/or drift. 

Since label directions, SOPs, and any additional 

wilderness restrictions would be followed during

application of herbicides, there is little impact expected 

from drift due to imprecise application or other 

accidental scenarios. The degree of effects would 

depend on the application method, with spot

BLM Vegetation Treatments Using Herbicides 4-245 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

applications less likely to cause adverse effects than

aerial applications. 

Recreation

There would be some scenic degradation, as well as 

distractions to public land users (e.g., noise from 

machinery) from treatments. In addition, there would be 

some human health risks to recreationists associated 

with exposure to herbicides (if use were allowed) or

smoke from fire. These risks are discussed in more 

detail under Human Health and Safety. Finally, some 

areas would be off-limits to recreation activities as a

result of treatments, from periods ranging from a few 

hours to days, or even one full growing season or 

longer, depending on the treatment. In most cases, 

recreationists would be able to find alternative sites 

offering the same amenities, although a lessened

experience could result from more concentrated use in 

these areas. 

The effects of herbicide treatments and fire use on fish 

and wildlife could have indirect negative impacts on

recreational activities such as fishing, hunting, and

wildlife viewing. For example, aerial application of an

herbicide over a large area could adversely affect these

activities by harming or displacing wildlife. 

Social and Economic Values 

Short-term closures or restrictions on public lands for 

certain vegetation treatments, such as implementation of

herbicide use re-entry restrictions to protect public 

health or to restrict access by grazing animals until

seeding efforts are established (up to two growing 

seasons) are unavoidable. It is expected that

communities that are particularly dependent on a single

industry would be most susceptible to adverse effects to 

employment or income due to vegetation treatment

projects. In particular, ranching communities and 

recreation-dependent communities may be more

affected than communities with diversified industries. 

Limits on grazing activity on public lands could put 

additional pressure on often tight economic margins in

ranching. Closures of treatment areas for extended 

periods of time could temporarily affect some

recreational uses and commercial activities. 

Human Health and Safety 

All treatment methods have the potential to injure or kill

workers or the public. The health and safety of workers 

could be at risk from exposure to herbicides; from 

working on uneven ground, broken terrain, and in dense 

vegetation; from use of hand and power tools; from 

inhalation of smoke; from exposure to falling debris;

and from other accidental situations. Although workers

would follow SOPs to reduce risks, not all risks could

be avoided. 

Members of the public could be at risk from flying

debris if they were near an area where manual or 

mechanical equipment was used. Risks could be

avoided if a safe zone was established around work

areas and the public did not enter this area. However, 

spray drift of herbicide, particulate matter, and other 

harmful materials associated with herbicide and fire

treatments could harm the public outside of treatment

areas. Smoke risks would be minimized or avoided by 

following fire management plans and conducting burns 

during periods when meteorological conditions were 

favorable to reduce smoke impacts to the public.

Herbicide drift would be minimized by using proper 

application equipment, using drift reduction agents, and

spraying during periods with little or no wind. 

Relationship between the Local Shortterm Uses and Maintenance and 

Enhancement of Long-term 

Productivity 

This section discusses the short-term effects of

vegetation treatment activities, versus the maintenance

and enhancement of potential long-term productivity of 

public land environmental and social resources. 

Short term refers to the total duration of vegetation 

treatment activities considered in the PEIS and PER

(about 10 to 15 years), whereas long term refers to an

indefinite period of time. The specific impacts vary in 

kind, intensity, and duration according to the activities

occurring at any given time. Initial activities, such as 

herbicide and mechanical treatments and fire use, result

in short-term, localized impacts. However, the 

overarching goal of the proposed vegetation treatments 

program is to restore natural fire regimes, vegetation,

and ecosystems, which should benefit all resources over 

the long term. 

Air Quality 

Vegetation treatments would cause short-term

degradation of air quality, with most degradation 

associated with fire use. As discussed earlier, much of 

the focus of treatments is on restoring natural fire

regimes and reducing the incidence and severity of 

BLM Vegetation Treatments Using Herbicides 4-246 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

wildfires. In general, wildfire impacts on air quality 

would likely be significantly greater than emissions 

from prescribed burning (USDA Forest Service and

USDI BLM 2000), since techniques to minimize 

emissions would be implemented during prescribed

burns and smoke management plans would permit

prescribed fires only during meteorological periods 

favorable to dispersion. Thus, the proposed vegetation

treatments should reduce smoke emissions associated 

with public lands over the long term. 

In addition, state smoke management meteorologists 

would consider the cumulative effects of emissions 

from other sources (such as road dust, other federal

vegetation management activities, and agricultural dust 

and burning) during the development of daily smoke 

management instructions. State smoke management

program managers would also consider these sources 

during development of smoke management plans 

submitted for approval (as a component of the state

smoke implementation plan) to the USEPA (USDA 

Forest Service and USDI BLM 2000). 

Soil Resources 

Although treatments would have short-term effects on

soil condition and productivity, it is predicted that the 

soil disturbance associated with restoration activities 

would have less impact and be less severe than soil 

erosion caused by wildfire and encroachment by

invasive species and noxious weeds. Furthermore,

monitoring and evaluation, integrated with an adaptive 

management approach, would allow the BLM to adjust

treatments to reduce soil disturbance to levels similar to 

historical conditions. 

Studies in forested and rangeland environments

indicate that forest and range landscapes that resemble 

conditions within historical ranges of variability 

provide favorable conditions for soil functions and 

processes that contribute to long-term sustainability of 

soil productivity (Munn et al. 1978, Cannon and

Nielsen 1984, and Hole and Nielsen 1970 cited in

USDA Forest Service and USDI BLM 2000). 

Restoration activities that move forests and rangelands 

toward historical ranges of variability would provide

favorable conditions for soil functions and processes, 

and contribute to long-term soil productivity levels at

the broad scale (USDA Forest Service and USDI BLM

2000). 

Water Resources and Quality 

The BLM proposes a 3-fold increase in overall 

treatment acreage, and over a 4-fold increase in the

number of acres treated in wetland and riparian habitats. 

Treatment of vegetation would cause a short-term

increase in soil erosion and surface water runoff.

Successful control of invasive plants, however, would 

lead to improved conditions in watersheds over the long

term, with the greatest improvement likely to occur in

degraded watersheds. The eventual growth of desirable 

vegetation in treated areas would moderate water 

temperatures, buffer the input of sediment and

herbicides from runoff, and promote streambank

stability. Ongoing efforts by the BLM to enhance

vegetation would also help to increase the acreage of 

watersheds that are functioning properly. Improvement 

of watersheds and water resources and quality would 

benefit salmonids and other species of concern that

depend upon these habitats for their survival (USDA 

Forest Service and USDI BLM 2000). 

Vegetation treatments that reduce hazardous fuels 

would benefit ecosystems by reducing the chances of a 

large, uncontrolled wildfire, which could result in the

destruction of a large amount of high quality habitat

potentially leading to erosion, especially if followed by

heavy rainfall. Hazardous fuels reduction would also

decrease the likelihood that wildfire suppression

activities would occur in or near aquatic habitats. 

The BLM’s ability to use four new chemicals (fluridone 

and diquat for aquatic applications, and imazapic and 

Overdrive® for terrestrial applications), and new 

herbicides as they become available, would provide new 

capabilities for controlling problematic invasive species 

that would be less likely to contaminate water than

treatments with many of the currently available 

herbicides. 

Wetland and Riparian Areas 

Removal of vegetation could cause a short-term 

increase in soil erosion and surface water runoff and 

could impact wetland and riparian areas. Successful

control of invasive plants in wetlands and riparian areas, 

however, would lead to improved conditions in these

habitats over the long term. The eventual growth of

desirable vegetation in treated areas would moderate 

water temperatures, buffer the input of sediment and 

herbicides from runoff, and promote bank stability in 

riparian areas. Ongoing efforts by the BLM to enhance 

wetland and riparian vegetation would also help to 

increase the miles of streams and acres of wetlands that

BLM Vegetation Treatments Using Herbicides 4-247 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

are classified by the BLM as “Proper Functioning.” 

Improvement of riparian and wetland habitat would also

benefit salmonids and other species of concern that

depend upon these habitats for their survival (USDA 

Forest Service and USDI BLM 2000). 

Control of aquatic and riparian vegetation can improve 

habitat quality for fish and wildlife, improve hydrologic 

function, and reduce soil erosion. Non-native species, 

such as purple loosestrife, form extensive monotypic 

stands that displace native vegetation used by wetland

animal species for food and cover (Bossard et al. 2000).

Water-thyme is an aquatic species that forms large mats

that fill the water column and can severely restrict water 

flow, leading to a decrease in water quality and habitat

for fish and wildlife. Eurasian watermilfoil, a species of 

aquatic plant that has spread widely over the western

U.S., alters the physical and chemical characteristics of

lakes and streams. Much of the BLM’s vegetation 

control efforts in wetland and riparian areas would 

focus on these species. 

Vegetation 

All treatments would have short-term adverse impacts 

to target vegetation, and in some cases non-target

vegetation. Treatments that remove or control invasive 

vegetation could provide immediate benefits to nontarget species, however, such as increased access to 

water and nutrients and enhanced vigor from reduced

competition with invasive species. 

Treatments that remove hazardous fuels from public 

lands would be expected to benefit the long-term health

of plant communities in which natural fire cycles have 

been altered. The suppression of fire results in the 

buildup of dead plant materials (e.g., litter and dead

woody materials), and often increases the density of 

flammable living fuels on a site. Treatments that restore 

and maintain fire-adapted ecosystems, through the 

appropriate use of mechanical thinning, wildland fire

use or prescribed fire, and other vegetation treatment

methods, would decrease the effects of future wildfires 

on plant communities and improve ecosystem resilience 

and sustainability. Over the long term, treatments

should also reduce the incidence and severity of

wildfires across the western U.S.

Treatments that control populations of non-native 

species on public lands would be expected to benefit

native plant communities over the long term by aiding 

in the reestablishment of native species. The degree of 

benefit would depend on the success of these treatments 

over both the short and long term. Some treatments are 

very successful at removing weeds over the short term,

but are not successful at promoting the establishment of

native species in their place. In such cases, seeding and 

planting of native plant species would be beneficial. 

Although modeling was not done as part of the PEIS 

and PER to determine the long-term effects of 

vegetation treatments, modeling done for similar 

treatments proposed by the BLM and Forest Service in

the Interior Columbia Basin showed that improvements 

in land condition would be slow. However, treatments 

would improve the mix of habitats so that vegetation

would be more resilient to disturbance and sustainable

in the long term. Plant communities that have declined

substantially in geographic extent from historical to

current periods (e.g., big sagebrush and bunchgrasses) 

would increase. Although the extent of weeds and other 

exotic and undesirable plants would continue to

increase, the rate of expansion would be slower (USDA 

Forest Service and USDI BLM 2000). 

Fish and Other Aquatic Organisms 

Control of aquatic and riparian vegetation can improve 

habitat quality for fish and wildlife, improve hydrologic 

function, and reduce soil erosion. Vegetation treatments 

that reduce hazardous fuels would benefit aquatic

organisms by reducing the chances of a large, 

uncontrolled wildfire, which could result in the 

destruction of a large amount of high quality wetland

and riparian habitat, especially if followed by heavy 

rainfall. Hazardous fuels reduction would also decrease 

the likelihood that wildfire suppression activities would

occur in or near aquatic habitats. Treatments that restore

natural fire regimes and native vegetation near streams 

should ensure a steady supply of large woody debris 

that would provide habitat for aquatic organisms in the 

future. 

Wildlife Resources 

All treatments would have short-term adverse impacts 

to wildlife and their habitats, as discussed above. 

Treatments that improve habitat would provide longterm benefits to wildlife. Treatments that remove

hazardous fuels from public lands and reduce the risk of 

large, intense wildfire would reduce the potential for 

future death and injury of wildlife and lead to improved

habitat. Treatments that control populations of nonnative species on public lands would be expected to

benefit most wildlife over the long term by aiding in the

reestablishment of native vegetation and restoring

wildlife habitat to near historical conditions. 

BLM Vegetation Treatments Using Herbicides 4-248 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

Although modeling was not done as part of the PEIS 

and PER to determine the long-term effects of 

vegetation treatments, modeling done for similar 

treatments proposed by the BLM and Forest Service in

the Interior Columbia Basin showed that improvements 

in habitat would be slow, perhaps not occurring for

decades. 

Livestock 

The proposed vegetation treatments would affect the 

availability and palatability of vegetation over the short

term. These impacts would begin to disappear within

one to two growing seasons after treatment. 

All treatments that successfully reduce the cover of 

noxious weeds and restore native vegetation on grazed

lands would benefit livestock by increasing the number

of acres available for grazing and the quality of forage. 

In addition, treatments would remove some noxious 

weeds (e.g., tansy ragwort, houndstongue, Russian

knapweed, and common St. Johnswort) that are harmful

to livestock. The success of weed removal and 

restoration of native habitats would determine the level 

of benefit of the treatments over the long term. 

Treatments that reduce the risk of future catastrophic 

wildfire through fuels reduction would also benefit

livestock. Uncontrolled, high intensity wildfires can

remove forage from large tracts of rangeland, reducing 

its suitability for livestock in the short term. Treatments 

that restore and maintain fire-adapted ecosystems,

through the appropriate use of mechanical thinning, fire, 

and other vegetation treatment methods would decrease 

the effects of wildfire on rangeland plant communities 

and improve ecosystem resilience and sustainability. 

Wild Horses and Burros 

The proposed vegetation treatments would affect the 

availability and palatability of vegetation over the short

term. These impacts would begin to disappear within

one to two growing seasons after treatment. 

All treatments that successfully reduce the cover of 

noxious weeds and restore native vegetation on grazed

lands would benefit wild horses and burros by 

increasing the number of acres available for foraging

and the quality of forage. In addition, treatments would 

remove some noxious weeds (e.g., tansy ragwort, 

houndstongue, Russian knapweed, and common St. 

Johnswort) that are poisonous to wild horses and burros. 

The success of weed removal and restoration of native 

habitats would determine the level of benefit of the

treatments over the long term. 

Treatments that reduce the risk of future catastrophic 

wildfire through fuels reduction would also benefit wild 

horses and burros. Uncontrolled, high intensity wildfires 

can remove forage from large tracts of rangeland,

reducing its suitability for wild horses and burros. 

Treatments that restore and maintain fire-adapted

ecosystems, through the appropriate use of mechanical

thinning, fire, and other vegetation treatment methods

would decrease the effects of wildfire on rangeland 

plant communities and improve ecosystem resilience

and sustainability. 

Paleontological and Cultural Resources 

Paleontological Resources 

Because paleontological resources are nonrenewable,

there is no difference between short-term and long-term 

impacts. The resource cannot recover from some types 

of adverse impacts. Once disturbed, the materials and

information of paleontological deposits may be 

permanently compromised. Any destruction of 

paleontological sites, especially those determined to 

have particular scientific value, would represent longterm losses. Furthermore, once paleontological deposits

were disturbed and exposed, natural erosion could 

accelerate the destruction of fossils, and exposed fossils

would be vulnerable to unauthorized collecting and

digging. Any discoveries of paleontological resources as 

a result of surveys required prior to treatment would

enhance long-term knowledge of the area and these 

resources. 

Cultural Resources and Traditional Lifeway 

Values

Any destruction of cultural resource sites would

represent long-term losses. Archaeological excavation 

to recover scientific data under the terms of an 

appropriate data recovery plan could result in the partial

or total destruction of the site, although the recovered

data would effectively mitigate for this destruction. Any 

investigations of cultural resources made during 

inventories or investigations required prior to vegetation 

treatments would enhance knowledge of the history and

early inhabitants of the region and serve to effectively

mitigate further potential effects of activities in the area. 

Vegetation treatments could have short-term impacts on

vegetation used for traditional lifeway values, especially

if herbicide drift were to impact non-target vegetation, 

BLM Vegetation Treatments Using Herbicides 4-249 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

or treatments were to affect both target and non-target 

vegetation, as would occur during certain herbicide 

treatments (such as with non-selective herbicides) and

fire use. In addition, fire use and herbicide treatments 

could displace Native peoples from traditional use areas 

until it was safe to reenter, or desirable vegetation was 

reestablishing. However, long-term restoration of native 

plant communities and natural ecosystem processes to 

the benefit of traditional lifeway resources should

compensate for the short-term losses in use. 

Visual Resources 

The proposed vegetation treatments would affect visual 

resources by changing the scenic quality of the 

landscape. Over the short-term, impacts to visual

resources from all treatment methods would begin to

disappear within one to two growing seasons. The 

regrowth of vegetation on the site would eliminate 

much of the stark appearance of cleared areas, and the 

site would develop a more natural appearance. Impacts 

would last for the longest amount of time in forests and

other areas where large trees and shrubs were removed. 

Over the long term, vegetation treatments would likely 

improve visual resources on public lands. Treatments 

that aim to rehabilitate degraded ecosystems, if 

successful, would result in plant communities 

dominated by native species (see Vegetation section for 

more information). Native-dominated communities tend

to be more visually appealing and productive than areas 

that have been overtaken by weeds (e.g., areas 

supporting a downy brome monoculture), or that have

been invaded by woody species (e.g., grasslands 

experiencing encroachment by conifer seedlings). 

Wilderness and Special Areas 

Impacts to wilderness and sensitive area resources 

would begin to disappear within one to two growing

seasons after treatment, regardless of the treatment 

method. The regrowth of vegetation on the site would 

eliminate much of the stark appearance of cleared areas, 

and the site would develop a more natural appearance. 

The longest lasting impacts would occur in forests and 

other areas where large trees and shrubs were removed. 

Benefits to plants and animals in terms of ecosystem

function and improved forage and cover would occur as 

the treated area recovered. 

Over the long term, vegetation treatments would likely 

improve resources on wilderness and special areas.

Treatments that aim to rehabilitate degraded ecosystems 

would result in plant communities that are dominated by 

native species (see Vegetation section for more

information). Native-dominated communities often 

provide better habitat for fish and wildlife, including

species of concern. 

Recreation

There would be some scenic degradation, as well as 

distractions to users (e.g., noise from machinery), from

treatments. In addition, there would be some human 

health risks to recreationists associated with exposure to 

herbicides (if use were allowed) or smoke from fire.

Finally, some areas would be off-limits to recreation 

activities as a result of treatments. These effects would 

be localized and short term.

Developed recreation sites with public facilities would

be treated in order to maintain the appearance of the

area and to protect visitors from the adverse effects of

unwanted vegetation (e.g. thistles, ragweed, and poison

ivy). Some mechanical activities, such as mowing in 

visitor use areas or along ROWs, would provide an

immediate benefit in terms of improved appearance of 

vegetation. Long-term adverse effects on developed

recreational facilities would be unlikely, as treatments 

are expected to improve native vegetation and the utility 

of these sites. In some cases, developed recreation sites 

could be temporarily closed during treatments. 

Treatments that restore native vegetation and natural 

fire regimes and other ecosystem processes would be 

beneficial to recreationists. Treatments would improve 

the aesthetic and visual qualities of recreation areas for 

hikers, bikers, horseback riders, and other public land 

users; reduce the risk of recreationists coming into

contact with noxious weeds and poisonous plants; 

increase the abundance and quality of plants harvested

from public lands; and improve habitat for fish and 

wildlife sought by fishermen and hunters. These 

benefits would be long term and improve the 

productivity of land resources and their ability to 

provide recreational values. 

Social and Economic Values 

Vegetation treatments would adversely affect use of

treated areas over the short term. Any restrictions on the

use of treated lands could cause social and economic 

hardship to affected parties. However, individuals and 

industries involved in the restoration of native

ecosystems on public lands would benefit. 

Over the long term, most users of public lands, and 

those with interests near public lands, would likely 

BLM Vegetation Treatments Using Herbicides 4-250 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

benefit. An important goal of treatments is to restore 

ecosystem health so that public lands can provide

sustainable and predictable products and services. In

addition, treatments would reduce risks to communities 

associated with large-scale wildfire, improve ecosystem

health to the benefit of recreationists and other public 

land users, and emphasize employment- and incomeproducing management activities near those

communities most in need of economic support and 

stimulus. The enhancement in long-term productivity of 

public lands to provide for social and economic needs 

would reflect not only the success or failure of

treatments, but also the influence of outside forces (e.g., 

economy, lifestyle changes, climate) over which the 

BLM and other federal agencies have no control

(USDA Forest Service and USDI BLM 2000). 

Human Health and Safety 

The proposed vegetation treatments could harm the 

health of workers and the public over the short term. 

Adverse reactions to smoke and herbicides could cause

minor to severe discomfort to sensitive individuals, but 

most symptoms would go away in a few hours. If 

serious injury or death resulted from treatments, the 

effects to the health of the affected individual would be 

long term, or in the case of death, permanent. 

All treatments that successfully reduce the cover of 

noxious weeds and restore native vegetation would help

to restore natural fire regimes and improve ecosystem 

health. If treatments were successful, long-term

improvement in fire regimes and ecosystem health 

would reduce the risk of wildfire and slow the spread of 

poisonous and other noxious weeds that are harmful or

annoying to humans. As native vegetation was restored, 

it could be possible to reduce the number of acres

treated with herbicides. Even if this were not possible, 

the ability to use several new herbicides evaluated in 

this PEIS, and new herbicides that may become

available in the future that are effective and less harmful

to humans than currently-available herbicides, should

reduce the risk to humans from herbicides on a per acre

basis. 

Irreversible and Irretrievable 

Commitment of Resources 

This section identifies irreversible and irretrievable 

commitments of resources that would occur from 

vegetation treatments. Irreversible and irretrievable 

commitments of resources refer to impacts or losses to

resources that cannot be reversed or recovered.

Examples are the extinction of a species or the 

permanent conversion of a vegetated wetland to open

water. In the first case, the loss is permanent and not

reversible under current genetic technology. In the 

second case, it is possible the open water could be

drained, so while the initial loss of the vegetated 

wetland is irretrievable, the action could be reversible. 

Air Quality 

Air quality would be affected by all treatment methods, 

with fire use contributing the most to degradation of air 

quality. These effects would occur only during the 

period of the treatment activity and there would be no

irreversible or irretrievable effects on air quality. 

Soil Resources 

Disturbance activities associated with current and 

proposed treatments could result in soil erosion and loss 

of soil and soil productivity. This loss of soil and soil

productivity would be irretrievable in the disturbance 

area, although the soil could be available for use at 

some other location. However, a benefit of increasing 

the amount of acres treated would be to slow the loss of 

soil and soil productivity due to invasive vegetation and

wildfire and to restore soil structure and function on

degraded sites as part of a larger goal to restore native 

ecosystem processes. As a result of these actions, soil

productivity in disturbed areas should reestablish over 

time. 

Water Resources and Quality 

An accidental herbicide spill or uncontrolled prescribed

fire could cause damage to water bodies lasting for 

several months. The ability to use water resources in the

affected area could be lost for an unknown period of 

time. However, these impacts could be reversed if 

restoration treatments were successful and herbicides 

naturally degraded. Other treatments should not result in

irreversible or irretrievable commitments of water 

resources. 

Wetland and Riparian Areas 

There would be no irreversible or irretrievable 

commitment of wetland or riparian resources. Although 

there would be short-term impacts to these resources 

from vegetation treatments, these impacts would not be

irretrievable and would be reversed if restoration

treatments were successful. In Alaska, it is possible that 

changes in the melting permafrost due to fire use could 

BLM Vegetation Treatments Using Herbicides 4-251 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

cause subsidence that could last a long time and 

possibly be permanent. 

Vegetation 

Native vegetation and plant productivity that was lost as 

a result of treatments would be irretrievable only until 

vegetation was reestablished, usually within several

growing seasons. 

Fish and Other Aquatic Organisms 

Several of the herbicides currently used, or proposed for 

use, by the BLM would have a moderate to high risk of

causing adverse health effects to fish and other aquatic 

organisms under maximum application and accidental

spill scenarios, and could potentially result in illness or

death. Loss of control over a prescribed fire could also

harm aquatic habitat and cause mortality or injury to

aquatic organisms. Treatments would likely result in

short-term habitat degradation and some reduction in

populations of fish and other aquatic organisms. These 

effects, however, would be reversible, as habitats would

improve and aquatic organism populations would likely

increase as a result. 

Wildlife Resources 

Native wildlife and habitat productivity that was lost as

a result of treatments would be irretrievable until native

plant communities were reestablished, usually within 

several growing seasons. Treatments that improve 

rangeland and forestland ecosystem health, including

plant productivity, would translate into benefits for 

wildlife, except for those species that have adapted to or 

thrive in areas where vegetation has changed from 

historic conditions. 

Livestock 

Short-term loss in vegetation function and quality from

treatments would have a short-term impact on livestock

productivity. Although some livestock could be

displaced from public lands, forage could be found 

elsewhere, although possibly at a higher cost. As 

rangelands improved, their ability to support livestock 

use levels at or near current levels should also improve. 

Herbicide treatments have the potential to cause injury 

or death to livestock. Although this impact would

represent an irreversible loss of the individual animal, 

the impacts to the livestock operation and industry 

would be reversible. 

Wild Horses and Burros 

Short-term loss in vegetation function and quality as a

result of treatments would have a short-term impact on

wild horse and burro productivity. Wild horses and

burros could be removed from rangelands to reduce 

their impacts to rangeland health and to speed up the 

process of rangeland restoration. These animals would 

be placed into adoption and would provide value to their 

owners. As rangelands improved, their ability to support

populations of wild horses and burros near current

levels would also improve. 

Herbicide treatments have the potential to cause injury 

or death to wild horse and burros. Although this impact

would represent an irreversible loss of the individual 

animal, the impacts to the wild horse and burro

populations would be reversible. 

Paleontological and Cultural Resources 

Paleontological Resources 

Because paleontological resources are nonrenewable,

any impacts would render the resource disturbance 

irreversible and the integrity of the resource

irretrievable. 

Cultural Resources and Traditional Lifeway 

Values

Cultural resources are nonrenewable, so any impacts 

would be irreversible, and the integrity of the affected

resource would be irretrievable. If near-surface cultural

resources were encountered, as during disking or 

chaining, such resources could be damaged or 

destroyed. The loss of such cultural resource

information would be irreversible and irretrievable. 

Archaeological excavation to recover scientific data 

under terms of an appropriate data recovery plan could 

result in the partial or total destruction of the site, 

although the recovered data would effectively mitigate

for this destruction. Any investigations of cultural

resources made during inventories or investigations 

required prior to vegetation treatments would enhance

knowledge of the history and early inhabitants of the 

region and serve to effectively mitigate further potential

effects of activities in the area. Overall, such finds could

help fill gaps in our knowledge of the history and early

inhabitants of the area. 

Vegetation treatment activities would impact plants and 

animals of traditional importance to Native peoples. 

However, these effects should be short-term and 

BLM Vegetation Treatments Using Herbicides 4-252 June 2007 

Final Programmatic EIS 
ENVIRONMENTAL CONSEQUENCES

reversible, as native plant communities would recover 

and habitat for fish and game species would improve. 

Visual Resources 

There would be no irreversible or irretrievable 

commitment of visual resources. Although there would

be short-term impacts to visual resources from

vegetation treatments, loss of visual resources would

not be irretrievable and could be reversed if restoration

treatments were successful. 

Wilderness and Special Areas 

There would be no irreversible or irretrievable 

commitment of resources. Although there would be 

short-term impacts to wilderness and special area

resources from vegetation treatments, these impacts 

would not be irretrievable and could be reversed if

restoration treatments were successful. 

Recreation

There would be no irreversible or irretrievable 

commitment of recreation resources. Although there 

would be short-term impacts to recreation resources 

from vegetation treatments, these impacts would not be

irretrievable and could be reversed if restoration

treatments were successful. 

Social and Economic Values 

Vegetation treatments would involve a substantial 

commitment by the BLM in terms of labor and financial 

resources. An estimated $1.1 billion would be needed to 

treat 6 million acres annually using the treatment and 

acreage assumptions outlined in Chapter 2. Several

thousand jobs would be created to support treatment and

restoration activities. Once the financial resources were

used, they could not be retrieved. Treatments that result

in the closure of recreation or grazing areas could have 

an irretrievable impact on the income of those involved

in these industries. 

Human Health and Safety 

Serious injury or death to humans caused by vegetation 

treatments could be irreversible and irretrievable. 

However, risk of death or serious injury is very 

unlikely, based on incidence of injury (very low) and

death (none) associated with BLM vegetation

treatments during the past decade. It is likely that

humans would experience minor discomfort from fire 

and herbicide treatments, but these effects would be 

short term and reversible. 

Energy Requirements and 

Conservation Potential 

Herbicide formulations may contain petroleum 

products, and all herbicide treatment methods require 

the use of energy, to operate equipment to treat 

vegetation and to transport workers to and from the job

site. Wildland fire use and prescribed fire would likely

require the least amount of energy per acre treated, 

followed by biological control, manual, herbicide, and 

mechanical treatment methods. For herbicide

treatments, less energy would be used to conduct aerial 

treatments than ground treatments for each acre treated. 

Because the Preferred Alternative treats the most acres 

using herbicides, it would use the most energy. The 

amount of energy used to treat vegetation using fire, 

mechanical, manual, and biological control methods 

would be similar among the action alternatives. The 

fewest acres treated, and the least amount of energy

used would occur under the No Action Alternative. 

Natural or Depletable Resource 

Requirements and Conservation 

Herbicide formulations may contain natural or 

depletable resources as constituents of the herbicide 

products or as carriers. It is anticipated that the use of 

natural and depletable resources would be minimal, 

with greatest use under the Preferred Alternative, and 

least amount of use under the No Action Alternative, 

with other alternatives intermediate between these two. 

All herbicide treatment methods require the use of 

energy, as described above. 

BLM Vegetation Treatments Using Herbicides 4-253 June 2007 

Final Programmatic EIS