CHAPTER 4

ENVIRONMENTAL CONSEQUENCES

ENVIRONMENTAL CONSEQUENCES

CHAPTER 4

ENVIRONMENTAL CONSEQUENCES

Introduction 

This chapter examines how herbicide treatment 

activities that utilize the three new active ingredients

(aminopyralid, fluroxypyr, and rimsulfuron) may affect 

natural, cultural, and socioeconomic resources on public 

lands. The focus of the analysis is on the impacts 

associated with application of herbicide formulations 

that include the three active ingredients, and on the 

alternative proposals for use of these herbicides. These 

herbicides would be part of a larger vegetation 

management program, and would potentially be used in 

conjunction with other treatment methods and other 

currently approved herbicides. A summary of impacts 

associated with the use of the 18 currently approved 

herbicides and with other treatment methods can be 

found in the Vegetation Treatments on Bureau of Land 

Management Lands in 17 Western States PEIS (USDOI 

BLM 2007a) and Vegetation Treatments on Bureau of 

Land Management Lands in 17 Western States PER

(USDOI BLM 2007c). 

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 in this PEIS. These 

impacts are defined as follows: 

• Direct effects – Effects that are caused by the 

action and occur at the same time and in the 

same general location as the action.

• Indirect effects – Effects that occur at a 

different time or in a different location than the 

action to which the effects are related.

• Cumulative effects – 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.

Cumulative effects also consider other types of 

vegetation treatments and treatments with other 

herbicides.

• Unavoidable adverse commitments – 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 – 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 – 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 reversible. If the site is reclaimed, 

it is possible to resume timber production.

In addition, this PEIS considers the interaction of 

effects, as follows:

• Additive – total loss of resources from more 

than one incident.

• Countervailing – negative effects are 

compensated for by beneficial effects.

• Synergistic – the 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 

that the BLM is considering for use of the three new 

herbicide active ingredients for treating vegetation, and 

Chapter 3 (Affected Environment), which describes the 

important resources and their occurrence and status on 

public lands. The analyses of environmental 

BLM Vegetation Treatments Three New Herbicides 4-1 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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 its focus is on broad-scale management 

direction. As discussed in Chapter 1, Proposed Action 

and Purpose and Need, site-specific issues would be 

addressed through environmental analyses prepared at 

the state, district, or field office level.

At the local level, the Ecosystem-Based Management 

approach would be used during development of sitespecific management goals to ensure that they are 

informed and adapted from learning based on science 

and local knowledge.

The assumptions about vegetation treatments that were 

made in the 2007 PEIS (USDOI BLM 2007a:4-1 to 4-2) 

carry over in this PEIS, as the new herbicides would be 

integrated into current treatment programs. 

Vegetation treatments are implemented with 

consideration for the larger land management context in 

which they occur. The BLM considers whether and how 

treatment areas will be revegetated or stabilized to 

ensure the long-term viability of the project area. The 

BLM strives to minimize long-term increases in bare 

ground resulting from vegetation treatments, which

might allow invasive plants to increase in abundance. 

Treated vegetation is removed from the site if it poses a 

further risk as hazardous fuel.

The impacts analysis assumes the following:

• Vegetation treatments would be developed and 

applied in an Integrated Pest Management

context, where all treatment methods, costs, 

and goals are considered.

• Tool(s) identified for the treatment would be 

the appropriate means to achieve the project 

objective. 

• Post-treatment follow-up such as seeding, 

monitoring, and retreatment would occur, as 

needed to achieve land management objectives.

• Maintenance of past treatments has occurred, 

and the BLM would maintain improved 

vegetation conditions, rather than 

implementing stand-alone, one-time 

treatments.

• The BLM would determine the need for the 

action based on inventory data and monitoring.

Post-treatment monitoring would occur after 

the project to ascertain its effectiveness in 

achieving the resource objective(s).

• The BLM would comply with federal, state, 

tribal, and local regulations that govern 

activities on public lands.

• The BLM would continue to follow SOPs and 

applicable mitigation listed in the 2007 PEIS 

(USDOI BLM 2007a:Table 2-8) and ROD 

(USDOI BLM 2007b:Table 2) under all 

alternatives to ensure that risks to human health 

and the environment would be kept to a 

minimum. 

Examples of SOPs that pertain to all resource areas 

include the following:

• Conduct a pre-treatment survey for sensitive 

resources.

• 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.

• Consider surrounding land uses before 

selecting aerial spraying as a treatment method.

• Apply the least amount of herbicide needed to 

achieve the desired results.

• Prepare a spill contingency plan in advance of 

treatment.

• Notify adjacent landowners prior to treatment.

• Require licensed applicators to apply 

herbicides.

• Use only USEPA-approved herbicides, and 

follow product label directions and “advisory” 

statements.

BLM Vegetation Treatments Three New Herbicides 4-2 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

• Follow the product label for use and storage.

• 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.

• 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 miles per hour (mph), and 

at about 30 to 45 feet above ground.

• Keep a copy of Safety Data Sheets (SDSs)/

Material Safety Data Sheets (MSDSs)1 at work 

sites.

• Keep records of each application.

• Implement additional applicable SOPs specific 

to individual resources, which are provided in 

the impact analysis section for each resource.

Additionally, mitigation measures specific to treatments 

with the three new herbicides have been identified for 

certain resource areas in Chapter 4. These mitigation 

measures could further reduce impacts associated with 

herbicide treatments.

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.

Generally, the types of incomplete and unavailable 

information are the same as those described in the 2007

1 Hazardous chemical reporting is now required to be done 

via an SDS, rather than the previously used MSDS. During 

the period of transition to the new reporting system, 

herbicides may have either an associated MSDS or SDS.

PEIS (USDOI BLM 2007a:4-3 to 4-4). Although 

knowledge about many aspects of terrestrial and aquatic 

species, forestland, rangelands, the economy, and 

society is still incomplete, the alternatives were 

evaluated using the best available information.

Ecological and human health risk assessments were 

developed by the BLM for aminopyralid, fluroxypyr, 

and rimsulfuron to address many of the risks that would 

be faced by humans, plants, and animals, including 

special status species, from the use of these three active 

ingredients. To assess risks to other resources from the 

use of herbicides, the BLM consulted information in the 

risk assessments and supporting documentation; state, 

federal, and local databases, Geographic Information 

System (GIS) data, 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. In 

these cases such information will be presented during 

analysis at the local level to make more informed 

decisions about specific treatment projects involving 

aminopyralid, fluroxypyr, and rimsulfuron. 

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 is made, 

information essential to 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 would be 

necessary to deal with site-specific conditions and 

processes. For example, mitigation measures identified 

in the following sections (and in the 2007 PEIS) 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 

BLM Vegetation Treatments Three New Herbicides 4-3 January 2016

Final Programmatic EIS

 
ENVIRONMENTAL CONSEQUENCES

and still ensure adequate protection of the resource. It is 

also possible that more restrictive measures would be 

necessary. This subsequent analysis will be used to 

bridge the gap between broad-scale direction and sitespecific decisions. This “step-down” analysis involves 

subsequent NEPA analysis at various levels, which may 

include the regional or statewide level, the district or 

field office level, and the local or project-specific level 

(USDOI BLM 2007a:1-19). 

Program Goals by Ecoregion

The goals of herbicide treatments were developed for 

the 2007 PEIS, and are presented by ecoregion in the 

following sections. These goals continue to represent

what the BLM hopes to achieve through the use of 

vegetation treatments on public lands, and are being 

carried forward in this PEIS. Herbicide treatments with 

the three new herbicides would be incorporated into the 

larger treatment program designed to meet these goals.

Temperate Desert Ecoregion

Over 70 percent 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 (as 

outlined in BLM Manual 9015 [USDOI BLM 1992]; 33 

percent of treatments), reduce hazardous fuels (25 

percent), conduct emergency stabilization and burned 

area rehabilitation activities (19 percent), and improve 

rangeland health (12 percent). Improvements of wildlife 

habitat and watershed health are objectives of lesser 

importance (6 and 5 percent of treatments, respectively) 

in this ecoregion.

Temperate Steppe Ecoregion

In the Temperate Steppe Ecoregion, most herbicide 

treatments would be conducted to meet integrated 

vegetation management (IVM) and/or IWM objectives 

(62 percent of treatments). Other important objectives 

include hazardous fuels reduction (25 percent) and 

improvement of rangeland health (11 percent). 

Subtropical Steppe Ecoregion

On BLM lands in the Subtropical Steppe Ecoregion, 

herbicide treatments would be used to improve habitat 

(38 percent of treatments), improve rangeland health 

(21 percent), reduce hazardous fuels (17 percent), and 

meet IVM and/or IWM objectives (11 percent). 

Mediterranean Ecoregion

In the Mediterranean Ecoregion, chemical treatments 

would be conducted primarily to improve forest health 

(35 percent of treatments), and to meet maintenancerelated (28 percent) and IVM and/or IWM (20 percent) 

objectives. Improvement of rangeland health (9 percent) 

and recreation areas (6 percent) 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 percent) and maintenance-related (22 

percent) objectives. Some less important treatment 

objectives include maintaining ROWs (3 percent), 

improving forest health (3 percent), and improving 

habitat for native vegetation (3 percent).

Subtropical Desert Ecoregion

Less than 1 percent of herbicide treatments would occur 

on BLM land in the Subtropical Desert Ecoregion. 

Herbicide treatments in this ecoregion would focus on 

managing woody species that have invaded shortgrass 

and mixed-grass prairies and riparian areas of the desert 

Southwest.

Tundra and Subarctic Ecoregions

Herbicide treatments in this ecoregion would occur on a 

very small portion of public lands in these ecoregions. It 

is estimated that no more than 1,000 acres of public 

lands in Alaska would be treated with herbicides in any 

year. Goals of future herbicide treatments in these 

ecoregions would be to control invasive species in 

disturbed areas (along trails and roads, and at heavy use 

areas) to prevent their spread into more pristine areas.

Land Use

Laws, regulations, and plans that pertain to land use are 

summarized in the 2007 PEIS (BLM 2007a:4-5). The 

FLPMA of 1976 directs the BLM to manage public 

lands to protect their resource values, and to develop 

resource management plans consistent with those of 

state and local governments. Management actions on 

public lands are guided by land use plans, which 

establish goals and objectives for resource management.

Similar to the 2007 PEIS, this PEIS is a national-level 

programmatic analysis. It contains broad regional 

BLM Vegetation Treatments Three New Herbicides 4-4 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

descriptions of resources, provides a broad 

environmental impact analysis, and provides Bureauwide decisions on herbicide use for vegetation 

management. Additionally, it provides an umbrella ESA 

Section 7 consultation for the broad range of activities 

described in the PEIS.

Impacts to land uses have not been identified at the 

programmatic level. It is assumed that vegetation 

treatments by all methods would continue to occur on 

up to 6 million acres annually, that treatments would 

continue to focus on areas with high levels of hazardous 

fuels and invasive plants, 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. 

Adding new active ingredients to the BLM’s list of 

approved herbicides would be expected to have a 

minimal effect on land uses. Herbicide treatments 

would continue to be conducted over the same 

geographic area and with the same program goals, and 

so would have no additional effects. However, it is 

assumed that under all alternatives, existing land use 

plans will be updated to include additions to the 

approved herbicide list, with modifications occurring

primarily at the field office level. 

Air Quality and Climate

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. This air quality analysis 

focuses on the release of criteria pollutants and GHGs

associated with herbicide treatments. 

Scoping Comments and Other Issues 

Evaluated in the Assessment

Scoping comments requested that this PEIS quantify 

GHG emissions from the proposed project activities.

Emission Sources and Impact 

Assessment Methodology

The potential impacts of herbicide use on air quality 

originate primarily from ground vehicle (truck, 

ATV/UTV, 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.

Methodology for Assessing Impacts to 

Air Quality

The methodology for assessing impacts to air quality 

from herbicide applications is discussed in detail in the 

2007 PEIS (USDOI BLM 2007a:4-6 to 4-8). Additional 

information on methodology, data sources, and results 

may be found in the air quality report that was prepared 

as supporting documentation for the 2007 PEIS (ENSR 

2005). The air quality methodology includes calculating 

annual emissions for the proposed alternatives by state 

from vehicle exhaust and fugitive dust (from travel on 

unpaved roads). Emissions were calculated for CO, 

nitrogen oxides (NOx), total suspended particulates

(TSP), PM10, PM2.5, and volatile organic compounds 

(VOCs). Annual exhaust emissions were determined 

using emission factor data for vehicles likely to be used 

in herbicide treatments and for transportation, and 

assumptions about periods of operation. It should be 

noted that the 2007 PEIS used 1998 emission factors, 

and therefore likely overestimates emissions using 

newer vehicles. Table 4-1 presents the annual emissions 

for Alternative B of the 2007 PEIS, which carries over 

to all the alternatives considered in this analysis (as the 

total treatment acreage would not change). Annual 

fugitive dust emissions were determined using emission 

factors that considered trip mileage and soil properties. 

In this analysis, PSD levels are used to indicate whether 

the herbicide use alternatives would significantly affect 

air quality.

The USEPA’s California Puff (CALPUFF) “lite” air 

pollutant dispersion model (a first level screening model

referenced in Appendix W of 40 CFR Part 51) was used 

to provide an example of potential TSP and PM 

emissions resulting from a single herbicide spraying 

event. Spray drift from various herbicide application 

methods was assessed using the AgDrift model.

As the current proposed action adds new active 

ingredients to the list of herbicides approved for use by 

the BLM, but does not increase the total amount of 

BLM Vegetation Treatments Three New Herbicides 4-5 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-1

Annual Emissions Summary for Herbicide Treatments Under All Alternatives

State Pollutant (tons per year)

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

Source: USDOI BLM 2007a.

herbicide application, a new analysis of emissions of 

criteria pollutants has not been completed for this PEIS. 

However, since the 2007 PEIS did not consider GHG 

emissions, a GHG emission analysis has been

completed for this PEIS. Mobile source GHG emissions 

were estimated using emission factor data for vehicles 

likely to be used in herbicide treatments and for 

transportation, using 2009 model year emission factors. 

A quantitative analysis of carbon sequestration 

(adsorption of atmospheric carbon dioxide by

vegetation and stored in woody biomass) was not 

conducted, as there is no appropriate protocol for 

evaluating impacts of land use changes on atmospheric 

carbon release and sequestration.

Standard Operating Procedures

The 2007 PEIS (USDOI BLM 2007a:4-8 to 4-9) lists 

SOPs that the BLM follows to minimize the potential 

adverse effects of herbicide use on air quality. These 

SOPs would continue to apply to herbicide treatments 

involving aminopyralid, fluroxypyr, and rimsulfuron:

• 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 and use appropriate 

buffer distances between spray sites and nontarget resources).

Additionally, all guidance provided in BLM manuals 

and handbooks would continue to be followed. At the 

local level, the BLM would consider best management 

practices (BMPs) to reduce GHG emissions associated 

with herbicide treatments, as appropriate. 

BLM Vegetation Treatments Three New Herbicides 4-6 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Impacts by Alternative

Impacts Common to All Alternatives

Based on the air quality analysis presented in the 2007

PEIS (USDOI BLM 2007a:4-9 to 4-13), the potential 

impacts from herbicide applications on local and 

regional air quality would be minor under all of the 

treatment alternatives. Additionally, since the total area 

treated using herbicides would be the same under all of 

the alternatives, differences in air quality emissions 

between alternatives would be minor. 

Annual Air Quality Emissions

None of the predicted annual emissions by pollutant, 

state, or alternative would exceed PSD annual emission 

significance thresholds. Furthermore, under each 

alternative, the total emissions from all the states for 

each pollutant would be less than 25 percent 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. Potential 

emissions would be highest in states with the greatest 

number of acres treated. Based on CALPUFF “lite” 

modeling, all PM concentrations resulting from a single 

example herbicide spraying event would be 

substantially lower than NAAQS thresholds at five 

representative locations, and predicted concentrations 

would be at least four orders of magnitude smaller than 

assumed background concentrations (Table 4-2).

Spray Drift and Volatilization

Under all alternatives, atmospheric concentrations of 

herbicides (predicted by particle size) resulting from 

spray drift from aerial, ground vehicle, and hand 

applications 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. Based on modeling, 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 currently approved herbicides or the three 

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, aminopyralid, fluroxypyr, and 

rimsulfuron are not expected to volatilize from dry soil 

surfaces, and are essentially non-volatile from water and 

moist soil (U.S. National Library of Medicine 2006,

2011, 2012). Therefore, application of these herbicides 

would not impact air quality through volatilization.

Greenhouse Gas Analysis

Estimated annual GHG emissions from the project were 

determined based on the methodology described under 

Methodology for Assessing Impacts to Air Quality, 

which can be found earlier in this Air Quality and 

Climate section. Based on projections for trip mileage 

made for Alternative B of the 2007 PEIS, GHG 

emissions associated with vehicles (ground and aerial) 

used to transport and apply herbicides were calculated. 

More information on the procedures used to estimate 

emissions, including uncertainties and assumptions, can 

be found in the Annual Emissions Inventory for BLM 

Vegetation Treatment Methods (ENSR 2005). As the 

total assumed treated acreage under that alternative 

(931,850) would be the same under all the alternatives 

analyzed in this document, there is no difference under 

the alternatives as far as GHG emissions.

Based on a total herbicide treatment acreage of 

approximately 932,000 acres, the proposed herbicide 

treatments would generate approximately 3,333

MTCO2e/yr of CO2, 14 MTCO2e/yr of N2O, and 2

MTCO2e/yr of methane (CH4). Therefore, total GHG 

emissions associated with the herbicide treatments

under all the alternatives is approximately 3,350

MTCO2e/yr. A comparison of this number to total 

emissions for the western U.S. helps provide an 

indication of the magnitude of GHG emissions 

associated with the project. Based on a review of GHG 

inventories provided by the USEPA (2014), not all 17 

states covered in the analysis area have completed an 

inventory; no data are available for Idaho, Nebraska, 

North Dakota, or Wyoming. For the remaining 13 states 

in the western U.S., total combined reported annual 

GHG emissions is approximately 1,400 MMT (million 

metric tons) CO2e/yr. Estimated annual project-related 

emissions are 0.0002 percent of this total, and 0.00006 

percent of the annual national reported GHG emissions 

of 5,546.3 MMTCO2e/yr. Additionally, annual 

emissions would be approximately 13 percent of the 

amount (25,000 MTCO2e/yr) that would require 

mandatory reporting under the USEPA’s GHG 

Reporting Rule, which is anticipated to capture 

BLM Vegetation Treatments Three New Herbicides 4-7 January 2016

Final Programmatic EIS
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TABLE 4-2

Example NAAQS Compliance Analysis for Herbicide Treatments Under All Alternatives

Location Pollutant Averaging 

Period

CALPUFF 

Concentration 

(μg/m3)

Background 

Concentration1

(μg/m3)

Total 

Concentration 

(μg/m3)

NAAQS 

Standard2

(μg/m3)

Tucson, 

Arizona

TSP 24-hour 2.79E-04 40 40 NA

Annual 7.65E-07 11 11 NA

PM10

24-hour 5.47E-04 30 30 150

Annual 1.50E-06 8 8 50

PM2.5

24-hour 7.21E-05 30 30 35

Annual 1.97E-07 8 8 15

Glasgow, 

Montana

TSP 24-hour 1.06E-04 40 40 NA 

Annual 2.90E-07 11 11 NA 

PM10

24-hour 2.36E-04 30 30 150

Annual 6.48E-07 8 8 50

PM2.5

24-hour 2.82E-05 30 30 35

Annual 7.74E-08 8 8 15

Winnemucca, 

Nevada

TSP 24-hour 1.36E-04 40 40 NA 

Annual 3.72E-07 11 11 NA 

PM10

24-hour 2.72E-04 30 30 150

Annual 7.44E-07 8 8 50

PM2.5

24-hour 3.60E-05 30 30 35

Annual 9.85E-08 8 8 15

Medford, 

Oregon

TSP 24-hour 3.75E-03 40 40 NA 

Annual 1.04E-05 11 11 NA 

PM10

24-hour 8.20E-03 30 30 150

Annual 2.28E-05 8 8 50

PM2.5

24-hour 1.14E-03 30 30 35

Annual 3.19E-06 8 8 15

Lander, 

Wyoming

TSP 24-hour 6.08E-05 40 40 NA 

Annual 1.67E-07 11 11 NA 

PM10

24-hour 1.37E-04 30 30 150

Annual 3.75E-07 8 8 50

PM2.5

24-hour 1.72E-05 30 30 35

Annual 4.70E-08 8 8 15

1 PM10 data from Table 5 of the Montana Modeling Guideline for Air Quality Permits (November 2007; Montana Department of 

Environmental Quality 2007). 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; and μg/m3 = micrograms per cubic meter.

approximately 85 to 90 percent of national GHG 

emissions (USEPA 2012d).

In terms of net GHG emissions, it is anticipated that 

under all of the alternatives, reductions in wildfire risk 

associated with herbicide treatments would result in 

indirect reduction in GHG emissions. Smoke from 

wildfires is a biogenic source of GHG emissions, and

wildfires can be exacerbated by certain invasive plants, 

such as cheatgrass and other annual grasses. Reducing 

wildfires is identified in the President’s Climate Action 

Plan (Executive Office of the President 2013) as a 

specific effort to protect natural resources. Wildfires 

generated approximately 97 MMT CO2e/yr in 2013 

(USEPA 2015), which represented 0.7 percent of total 

national emissions for that year. Because many factors 

contribute to wildfire risk, it is not possible to quantify 

the contribution to net reductions in GHG emissions of 

the proposed herbicide treatments. However, the 

reduction in wildfire risk from successful vegetation

BLM Vegetation Treatments Three New Herbicides 4-8 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

treatments would be expected to have long-term 

beneficial effects over many years. 

Given the relatively low amount of GHG emissions 

associated with herbicide treatments, and their role in 

larger BLM efforts to reduce the frequency, extent, and 

severity of wildfire, none of the alternatives are 

expected to have a significant adverse effect on GHG 

emissions or climate change.

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

The No Action Alternative corresponds to the Preferred 

Alternative in the 2007 PEIS. The air quality analysis 

for this alternative assumed that 932,000 acres would be 

treated using herbicides annually. While the BLM has 

not come close to this maximum acreage since the 

release of the ROD for the 2007 PEIS, for the purposes 

of this analysis, the tables from the 2007 PEIS 

(reprinted as Tables 4-1 and 4-2 in this document) are 

still considered to be suitable, conservative estimates. 

As indicated in Table 4-1, total pollutant emissions 

would include approximately 206 tpy TSP, 62 tpy CO, 

and 45 tpy PM10. Total GHG emissions would be 3,350 

MTCO2e/yr. These emissions would continue to 

dominate in states with the greatest number of acres 

treated. While Table 4-1 assumes that the greatest 

treatment acreage would occur in Idaho and Nevada, in 

reality more extensive herbicide treatments occurred in 

New Mexico during 2006 to 2011. However, no states 

had treatment acres that reached or exceeded the 

estimate for Idaho. Therefore, Table 4-1 should be used 

as a guide, with the understanding that the proportion of 

treatment acres by a state in any given year is likely to 

shift over time. Idaho, Nevada, New Mexico, Oregon, 

and Wyoming are likely to continue to be among the 

states with the greatest annual air quality emissions. 

Although not quantified, herbicide treatments under 

Alternative A would be expected to have a positive 

effect on air quality by reducing the risk of wildfire. 

Smoke and wildfire cause short-term impacts to 

visibility and air quality, predominantly through the 

release of PM and CO. Actions to reduce wildfire risk 

would continue to have an indirect effect on air quality, 

depending on the efficacy of fuels reduction treatments.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, it is expected the total 

annual emissions of criteria pollutants and GHGs would 

be similar to those under the No Action Alternative. 

With the introduction of the three new active 

ingredients, the BLM would change its relative use of

herbicides, but the total area treated is still assumed to 

be 932,000 acres. Likewise, it is assumed that there 

would be no difference in the method of application for 

the new herbicides. As under the No Action Alternative, 

it is expected that the greatest release of air quality 

pollutants would likely occur in Idaho, Nevada, New 

Mexico, Oregon, and Wyoming.

Benefits to air quality from reduction of wildfire risk 

would be similar to those under the No Action 

Alternative. Treatments would continue to target

cheatgrass and other fire fuels.

Alternative C – No Aerial Application of New 

Herbicides

Under this alternative, the new herbicides would not be 

available for treatments involving aerial application 

methods. Instead, currently approved herbicides would 

continue to be utilized for plane and helicopter 

treatments. Therefore, it is expected that the overall 

extent of aerial applications would be much the same as 

at present and under the other action alternatives. Total 

releases of air quality pollutants, including criteria

pollutants and GHGs also would be similar to those

under the other alternatives. Similar to Alternatives A 

and B, it is expected that the greatest release of air 

quality pollutants would likely occur in Idaho, Nevada, 

New Mexico, Oregon, and Wyoming.

Benefits to air quality from reduction of wildfire risk 

would be similar to those under the other alternatives.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under Alternative D, total emissions of air quality 

pollutants would be much the same as under the other 

alternatives. Although rimsulfuron would not be 

available for use under this alternative, currently 

approved herbicides (such as aminopyralid) would 

continue to be used to meet treatment goals, and the 

total area treated with herbicides by aerial and ground 

methods would be similar to the area treated under the 

other alternatives. Therefore the total emissions of 

criteria pollutants and GHGs would be about the same 

as under the No Action Alternative and the other action 

alternatives. Similar to the other alternatives, it is 

expected that the greatest release of air quality 

BLM Vegetation Treatments Three New Herbicides 4-9 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

pollutants would likely occur in Idaho, Nevada, New 

Mexico, Oregon, and Wyoming. 

Benefits to air quality from reduction of wildfire risk 

would be similar to those under the other alternatives.

Mitigation for Herbicide Treatment 

Impacts

No mitigation measures are proposed for air quality at 

the programmatic level.

Soil Resources

Introduction

Soil is an essential component of natural ecosystems, 

providing habitat for a great variety of organisms and a 

medium for plant growth, and protecting downgradient 

ecosystems by serving as a physical and biological filter 

of chemicals in the environment (Wild 1993).

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 invasive plants (Lacey et al. 1989). Many 

noxious weeds and other invasive plants have relatively 

sparse canopies, which allow for greater evaporation 

from the exposed soil than dense vegetative cover. Sites 

infested with invasive plants often have more extreme 

soil temperatures that can alter soil moisture regimes. 

Noxious weeds and other invasive plants 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 1999a). 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

Several scoping comments were concerned with the 

persistence of the herbicides in soil and residual soil 

activity, particularly in regard to aminopyralid.

Herbicide fate in soil and the potential for transport of 

the herbicide from the treatment site on wind-blown soil 

particles were also concerns.

Standard Operating Procedures

The BLM would continue to implement the SOPs 

identified in the 2007 PEIS 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 percent where there is the 

possibility of runoff carrying the granules into 

non-target areas.

In addition, the BLM follows practices, when 

implementing herbicide treatments, which help 

minimize effects to soil. The BLM considers herbicide 

and target site characteristics to determine the suitability 

of the herbicide at that location. Knowledge of herbicide 

persistence, mobility, and adsorption are included in 

herbicide selection. Additionally, herbicide applications 

are timed in relation to soil moisture and anticipated 

weather conditions to reduce the potential for off-site 

transport. Herbicide applications are avoided when the 

soil moisture status and site characteristics increase the 

possibility of runoff or deep percolation.

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 

BLM Vegetation Treatments Three New Herbicides 4-10 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

and transport. Herbicides dissipate from soils by 

transport with water or wind, through chemical or 

biological degradation processes, or by immobilization 

through adsorption onto soil surfaces. These processes 

are discussed in more detail in the 2007 PEIS (USDOI

BLM 2007a:4-14 to 4-15). The estimated half-life and 

soil adsorption (organic carbon-water partitioning 

coefficient) of the three herbicides considered in this 

PEIS are presented in Table 4-3.

TABLE 4-3

Estimated Soil Half-life (Aerobic Conditions) and 

Adsorption Affinity for Active Ingredients

Herbicide Soil Halflife (days)

Soil Adsorption 

(Koc)

Aminopyralid 32 to 533 1.05 to 24.3 mL/g

Fluroxypyr 7-23 50 to 136 mL/g

Rimsulfuron 5 to 40 19 to 74 mL/g

Sources: USEPA 2005b, New York State Department of 

Environmental Conservation (NYSDEC) 2009, U.S. National Library 

of Medicine 2011.

mL/g = milliliters per gram.

Soil structure affects water movement and may allow 

herbicides to move through the soil profile before being 

absorbed or degraded. Large soil cracks or openings can 

cause rapid herbicide movement. Soil texture affects the 

surface charge and the surface area for pesticide 

adsorption. Soils with a higher clay content have a 

greater ability to hold pesticides, but are more 

susceptible to runoff. Sandy soils leach more readily 

and provide fewer sites for pesticide adsorption. 

Organic matter content is considered the most important 

soil property affecting pesticide adsorption. Pesticides 

are very strongly attracted to the surface of organic 

matter and are less likely to leach in soils high in 

organic matter.

Summary of Herbicide Impacts

The following section discusses impacts to soil from the 

three active ingredients proposed for use. This 

assessment of impacts assumes that SOPs listed in the 

2007 PEIS (USDOI BLM 2007a:Table 2-8) would be 

followed when using the three herbicides. These 

procedures, which have designed to reduce potential 

unintended impacts to soil, 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 is reestablished. If herbicide treatments lead 

to revegetation with native plants, soil stability may be 

improved relative to sites dominated by invasive plants. 

Use of herbicides to manage noxious weeds and other 

non-native, invasive species could benefit soil. 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. 

Negative effects associated with invasive plant species 

include increased sediment deposition and erosion, and 

alteration of soil nutrient cycles (Bossard et al. 2000). 

For example, soft brome changes the physical 

characteristics of soil and alters the cycling of carbon 

and nitrogen (Norton et al. 2004).

Cheatgrass and other annual grasses increase the risk of 

fire, so control of these species can minimize risk of fire 

damage to soil. Soil can be damaged by fire through 

changes to its structure, particularly through the loss of 

organic matter, which can occur even at relatively low 

temperatures. The loss of soil structure increases the 

bulk density of the soil and reduces its porosity, thereby 

reducing soil productivity and making the soil more 

vulnerable to postfire runoff and erosion (Neary et al. 

2005).

The potential effects of herbicides on biological soil 

crusts are discussed in the 2007 PEIS (USDOI BLM 

2007a:4-15 to 4-16). Past studies have shown both 

positive and negative effects to biological soil crusts as 

a result of herbicide treatments. Cyanobacteria, lichen, 

and moss constituents may be impacted to varying 

degrees. However, use of herbicides can also benefit 

biological soil crusts by preventing the invasion of 

annual grasses, which reduce biological crust cover. The 

BLM’s guidance manual on biological soil crusts 

instructs that caution should be used when applying 

herbicides to soils that support these crusts (Belnap et 

al. 2001).

BLM Vegetation Treatments Three New Herbicides 4-11 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Impacts of Aminopyralid

Aminopyralid is broken down in the soil by microbes 

and sunlight. Studies of aminopyralid show a wide 

range of soil half-lives under aerobic conditions (from 5 

to 533 days; as summarized in AECOM 2015). Given 

the variability, there is some uncertainty as to how long 

this active ingredient persists in the environment after 

application. Dow AgroSciences (2005) lists the average 

half-life for aminopyralid at 34.5 days for North 

American soils. A recent study in Colorado found that

the half-life of aminopyralid was approximately 29 

days, with no appreciable herbicide residue left after 1 

year (Lindenmyer 2012). It is expected that 

aminopyralid remains active in the soil for a month or 

more after application, and may have residual activity 

during this time.

Based in its low toxicity to terrestrial invertebrates 

(AECOM 2015), aminopyralid is believed to be of low 

toxicity to soil macroorganisms. However, there is a 

lack of information about its toxicity to soil 

microorganisms, and about associated long-term effects 

to soil productivity.

Aminopyralid is persistent in plant materials and the 

manure of animals that have eaten plant materials 

treated with this herbicide. Therefore, compost and 

mulch made from contaminated plants and/or manure, if 

applied to soil, can adversely affect crops and other 

plantings (Washington State University Extension 

2011). These contaminated materials should not be used 

as soil amendments. 

Aminopyralid is weakly sorbed (attached by physical or 

chemical processes) to soil (Fast 2010), and therefore is 

unlikely to be transported off-site in large amounts on 

wind-blown soil. 

Impacts of Fluroxypyr

Fluroxypyr is rapidly degraded in soil by 

microorganisms, with reported half-lives of 1 week to 

23 days under aerobic conditions (Lehmann 1991,

USEPA 1998a, National Library of Medicine 2011). In 

one study, only 1 percent of the active ingredient was 

detected after 3 months (Brumhard and Fuhr 1992 cited 

in National Library of Medicine 2011). Fluroxypyr is 

mobile to very mobile in soil, but its movement is 

reduced by its quick microbial degradation. Fluroxypyr 

has very minimal residual soil activity.

Fluroxypyr has two major metabolites: a pyridine and a 

methoxypyridine. Fluroxypyr degrades first to the 

pyridine and then to the methoxypyridine, which is 

persistent in soil (Lehmann 1991; Cederlund et al. 

2012). This second degradate has a high tendency to 

adsorb to soil, and is slowly degraded in place by 

microbial degradation and volatilization (Lehmann 

1991). In one study, no significant degradation of the 

second degradate was observed after 350 days 

(Cederlund et al. 2012); however, another study 

observed soil half-lives of 90 to 570 days under various 

laboratory conditions (Lehmann et al. 1990). 

Based in its low toxicity to terrestrial invertebrates 

(AECOM 2014a), fluroxypyr is believed to be of low 

toxicity to soil macroorganisms. However, there is a 

lack of information about its toxicity to soil 

microorganisms. Long-term effects to soil productivity 

and biological processes are not known.

Given its rapid degradation, high mobility in soil, and 

minimal residual activity, there would be a low risk of 

transport of fluroxypyr off of the treatment site in 

windblown soil. The amount adsorbed to soil would be 

much less than the amount applied to the treatment site, 

and would rapidly dissipate. The second degradate 

would persist for longer and could be transported off the 

treatment site.

Impacts of Rimsulfuron 

Rimsulfuron breaks down rapidly in soil, with aerobic 

metabolism the primary route of degradation. In aerobic

conditions, it has a soil half-life of 5 to 40 days, and in 

anaerobic conditions, it has a soil half-life of 18 days 

(NYSDEC 2009). Its mobility in soil ranges from 

moderate in clay and silt loams to very mobile in sandy 

loams.

One study of rimsulfuron found that it is poorly 

mineralized, and that degradation products have the 

potential to accumulate in soil. Rimsulfuron degrades 

into a first metabolite, which then degrades rapidly into 

a second metabolite. The second metabolite is not 

readily degraded (Metzger et al. 1998). In one study of 

an aerobic soil environment, there was no decline in this 

chemical after 1 year. There is no indication that this 

degradate exhibits toxicological properties (NYSDEC 

2009).

One study of rimsulfuron found that there were no 

adverse effects to the microflora of agricultural soils for 

standard application rates of the herbicide (Radivojevic 

et al. 2011). At much higher application rates, minor, 

transitory adverse effects to soil microorganisms were 

observed, indicating that short-term adverse effects to 

BLM Vegetation Treatments Three New Herbicides 4-12 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

soil could occur under accidental spill scenarios. Longterm effects to soil productivity and biological processes 

are not known.

Rimsulfuron’s tendency to adsorb to soil varies by soil 

type, and is greatest in soils with high organic matter or 

clay content (Metzger et al. 1998). Therefore, there is 

some potential for transport off-site on soil particles, 

although clay and high-organic soils would likely have 

a relatively low potential for wind erosion.

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 its vegetation treatment programs, using only 

the 18 currently approved herbicides. Herbicide 

treatments would have both beneficial and adverse 

effects on soil, as discussed in the previous sections. 

Herbicides would continue to be used on approximately 

932,000 acres annually. 

Of the 18 active ingredients that would be used under 

this alternative, those that are most persistent in soil 

include diquat, diuron, hexazinone, imazapic, imazapyr, 

picloram, and tebuthiuron (USDOI BLM 2007a:Table 

4-7). Diquat has a half-life of 3 years or longer, but its 

use would continue to be minimal (less than 1 percent 

of all acres treated). Tebuthiuron has a half-life of 

roughly 1 year. Its use would constitute approximately 

13 percent of all acres treated under the No Action 

Alternative. Other herbicides with half-lives of 90 days 

or greater would make up approximately 30 percent of 

all herbicide treatment acres. 

Under this alternative, the herbicides with the most 

extensive use on BLM lands would be imazapic (20 

percent), triclopyr (15 percent), clopyralid (13 percent), 

and tebuthiuron (13 percent; see Table 2-4). Impacts to 

soil from these herbicides are discussed in the 2007 

PEIS (USDOI BLM 2007a:4-16 to 4-21). None of these 

herbicides have been found to have substantial impacts 

on soil or soil organisms. Tebuthiuron is extremely 

persistent in soil, and has been detected at application 

sites more than 10 years after application (Gay et al. 

1997 cited in USDOI BLM 2007a).

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, the total area receiving 

herbicide treatments would remain the same (932,000 

acres), but the suite of chemicals used at individual sites 

would change with the introduction of aminopyralid, 

fluroxypyr, and rimsulfuron into treatment programs.

Aminopyralid would be used on approximately 10 

percent, and rimsulfuron on approximately 16 percent, 

of all acres treated. Use of fluroxypyr would be minimal 

(1 percent of all acres). Fluroxypyr and rimsulfuron 

have relatively short half lives in soil (Table 4-3).

Aminopyralid also has a fairly short half-life, but there 

is evidence that it may be quite persistent (with a halflife of more than a year) under certain site conditions. 

Additionally, plant materials and residues that have 

been treated with aminopyralid may continue to release 

aminopyralid to the soil until these materials have 

decomposed. None of the new herbicides proposed for 

use have been found to have substantial impacts on soil 

or soil organisms.

With the addition of the three new herbicides, use of 

some previously-approved herbicides is expected to 

decrease, as shown in Table 2-4. Under the Preferred 

Alternative, use of glyphosate, imazapic, and picloram 

would decrease by an estimated 4 to 10 percent of the 

total acres treated. Imazapic and picloram have fairly 

long half-lives, relative to the new herbicides. 

Therefore, the overall persistence of herbicides in soil 

could be reduced under the Preferred Alternative. 

Overall, potential adverse effects to soil and soil 

organisms would be minor, although potentially less 

than those under the No Action Alternative.

If availability of the new herbicides were to increase the 

efficacy of the BLM’s vegetation treatment programs, 

resulting in better control of noxious weeds and of 

invasive species that increase fire frequency, there may 

be a slightly greater benefit to soil resources than under 

the No Action Alternative. 

Alternative C – No Aerial Application of New 

Herbicides

Under Alternative C, vegetation treatments would 

utilize the same suite of chemicals as under Alternative 

B, and the same maximum number of acres as under the 

other alternatives, but a restriction on aerial application 

BLM Vegetation Treatments Three New Herbicides 4-13 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

of the new herbicides would result in slight differences 

in the relative amounts of herbicides used. As shown in 

Table 2-4, use of the new herbicides would be less than 

under the Preferred Alternative, and the associated 

reductions in use of glyphosate, imazapic, and picloram 

would also be less. Therefore, overall persistence of 

herbicides in soil would fall somewhere between the No 

Action Alternative and the Preferred Alternative. 

Impacts to soil would be minor, similar to the other 

alternatives. 

Benefits to soil resources could be slightly greater than 

under the No Action Alternative, and slightly less than 

under the Preferred Alternative.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative, the BLM would not add 

rimsulfuron to its list of approved active ingredients. 

However, all currently approved ALS-inhibiting 

herbicides would continue to be used. As a result, the 

breakdown of herbicide usage would be very similar to 

that under the No Action Alternative. Because 

rimsulfuron would not be available to manage

cheatgrass and other winter annuals, the BLM would 

continue to rely heavily on imazapic for these uses. 

With the introduction of aminopyralid, use of 

glyphosate would be reduced. Glyphosate and 

aminopyralid have similar soil half-lives, and under 

certain conditions aminopyralid may be more persistent 

than glyphosate. Overall, impacts to soil resources 

would be minor, and would be very similar to those 

under the No Action Alternative. It is expected that 

benefits to soil from control of noxious weeds and other 

invasive vegetation also would be similar to those under 

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 has numerous uses, 

including irrigation, drinking water (for humans and 

livestock), domestic needs, aquaculture, and other uses 

(USGS 2013). Approximately 44 percent of the U.S. 

population depends on groundwater for its drinking 

water supply (National Groundwater Association 2010). 

Studies have shown some groundwater supplies to be 

contaminated with herbicides and other contaminants 

(e.g., total dissolved solids and metals). Generally, 

shallow groundwater aquifers are at greater risk for 

contamination than deeper sources. As discussed in the 

2007 PEIS (2007a:3-15 to 3-18) and Chapter 3 of this 

PEIS, 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

Scoping comments were concerned about the potential 

for the new herbicides to adversely affect water quality. 

Comments addressed herbicide drift, erosion of 

contaminated soils into waterways, and contamination 

of surface water, groundwater, and drinking water. One 

comment noted that aminopyralid has been detected in 

surface water in Montana. Another comment inquired 

about how invasive infestations of aquatic plants would 

be controlled (to prevent deterioration of water quality) 

if buffers are required around water bodies for 

treatments involving the new herbicides.

One comment mentioned the requirements of the Clean 

Water Act, and requested that the BLM show that use of 

the new herbicides would not result in degradation of 

water quality of Section 303(d)-listed waters, and 

indicate how other anti-degradation provisions of the 

Clean Water Act would be met.

Other commenters showed support for the new 

herbicides by noting that they are safe to use around 

water and have a low risk of resulting in water 

contamination.

Standard Operating Procedures

The BLM would continue to implement the SOPs 

identified in the 2007 PEIS to reduce unintended 

BLM Vegetation Treatments Three New Herbicides 4-14 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

impacts to water quality and quantity from the 

application of herbicides: 

• 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 spray drift and 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.

• As needed, maintain buffers between treatment 

areas and water bodies. Buffer widths should 

be developed based on herbicide- and sitespecific 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.

These SOPs are general to herbicide treatments, and 

would apply to treatments with the three new active 

ingredients, as applicable.

Additionally, the ROD for the 2007 PEIS has identified 

two mitigation measures for herbicide treatments that 

apply to the three new active ingredients:

• Establish appropriate (herbicide-specific) 

buffer zones to downstream water bodies, 

habitats, and species/populations of interest.

These buffer zones are based on information 

provided in the risk assessments indicating the 

minimum safe distance to protect aquatic 

organisms.

• Areas with potential for groundwater for 

domestic or municipal water use shall be 

evaluated through the appropriate, validated 

USEPA model(s) to estimate vulnerability to 

potential groundwater contamination, and 

appropriate mitigation measures shall be 

developed if such an area requires the 

application of herbicides and cannot otherwise 

be treated with nonchemical methods.

As a result of a court ruling in 2011, the National 

Pollution Discharge Elimination System (NPDES) 

regulations no longer provide an exemption for 

discharges of pesticides that leave a residue into Waters 

of the U.S. Therefore, NPDES permits are now required 

for application of pesticides in or near aquatic habitats 

in states where BLM herbicide treatments would occur. 

Necessary NPDES permits would be obtained at the 

local level for proposed herbicide treatment projects, in 

accordance with the requirements detailed on the 

USEPA’s NPDES Pesticide Homepage 

(http://water.epa.gov/polwaste/npdes/pesticides/index.cf

m).

Summary of Herbicide Impacts

Aminopyralid, fluroxypyr, and rimsulfuron would only 

be used on terrestrial vegetation; none of these 

herbicides are currently approved for aquatic uses.

Aminopyralid, however, may receive an aquatic 

registration in the near future that would address

incidental overspray of this active ingredient during 

treatment of vegetation within close proximity to 

BLM Vegetation Treatments Three New Herbicides 4-15 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

wetland and riparian vegetation. Aminopyralid would 

not be used to manage aquatic vegetation as a result of 

this registration, and would not be applied directly to the 

water column like other aquatic herbicides.

Impacts to Water Quality 

The primary means of off-site movement of terrestrial 

herbicides to water are runoff, leaching, drift, and 

misapplication/spills. If aminopyralid receives an 

aquatic registration, it could also reach water through 

incidental overspray (direct spray). Surface water could 

be affected by any type of off-site herbicide movement, 

while groundwater potentially would be affected only 

by leaching. Site conditions and application technique 

can also influence the effects of an herbicide on water 

quality. Pollution results from herbicide concentrations 

that are elevated enough to impair water quality and the 

beneficial use of the impacted water (USDOI BLM 

1991). The 2007 PEIS (USDOI BLM 2007a:4-26 to 4-

29) goes into detail about the general ways by which 

herbicides can impact water quality by the four means 

of off-site movement. This information is summarized 

in the following paragraphs.

Runoff and Leaching. Three physical properties, in 

combination with climate, geology, and topography, 

determine the runoff and leaching potential of an 

herbicide: 1) persistence (the time a chemical stays 

active); 2) soil adsorption (the tendency of a chemical to 

bind to soil particles); and 3) solubility (the tendency of 

a chemical to dissolve in water; Bonneville Power 

Administration 2000).

Table 4-4 lists the factors associated with herbicide 

movement to groundwater, and Table 4-5 lists the 

physical properties of the three active ingredients

proposed for use and the associated off-site movement 

potential via leaching and runoff. Herbicides must be 

relatively persistent to have the potential to leach or run

off. Herbicides that adsorb strongly to soil particles 

(because of herbicide and/or soil properties) tend 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 

(USDOI BLM 1991). Herbicides with low soil 

adsorption tend to leach down through the soil, although 

herbicides with low solubility in water may be more

likely to run off. Site characteristics that may affect the 

likelihood of an herbicide reaching a water body via 

runoff or leaching include amount of precipitation, 

depth to groundwater, and soil type. 

Drift. The airborne movement of herbicides beyond the 

treatment area is one mode of potential surface water 

contamination. The application technique, weather 

conditions, and applicator error can all contribute to 

drift. Broadcast treatments from an aircraft or a boom 

are more likely to drift from the treatment area than spot 

and localized treatments. The potential for drift is also 

increased during warm temperatures and wind speeds 

greater than 5 mph (Bonneville Power Administration

2000). Because of the potential for drift, buffers 

between the treatment site and nearby water bodies may 

be specified to protect aquatic species.

TABLE 4-4

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.

BLM Vegetation Treatments Three New Herbicides 4-16 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-5

Herbicide Physical Properties and Off-site Movement Potential

Herbicide

Physical Properties Off-site Movement Potential

Persistence Solubility (mg/l) Adsorption 

(Koc)

Groundwater 

Leaching

Surface Water 

Runoff

Aminopyralid Moderate 2,480 1 to 24 High High

Fluroxypyr Low 7,300 50 to 136 Low Low

Rimsulfuron Low 7 19 to 74 Low Low

Note: The information in this table applies to the active ingredient itself, not the degradation products.

Sources: USEPA 2005c, NYSDEC 2009, U.S. National Library of Medicine 2011, 2012.

Misapplications and Spills. Herbicides registered for 

use in terrestrial habitats may affect surface water and 

groundwater as a result of unintentional spills or 

accidental direct spray of water. Most experts agree that 

misapplications and spills are the leading cause of 

impacts to non-target resources. Misapplications and 

spills are caused by failure to follow label instructions 

and restrictions, unforeseen conditions and accidents, 

and by applicator carelessness. The impacts of a spill 

depend on the persistence and mobility of the spill, as 

well as how quickly the spill is cleaned up.

Other Factors. Additional factors that may influence 

the potential for herbicides to affect water quality 

include the following:

• Type of water body (small and still water 

bodies versus large and fast-moving rivers);

• Amount of rainfall;

• Type of vegetation (thick vegetation versus 

little to no vegetation); and

• Application technique (aerial/broadcast versus 

spot treatments).

Herbicides can also affect water quality by contributing 

to increased nutrient loading to surface water and 

groundwater. Nutrient enrichment of aquatic systems 

can lead to algal blooms and eutrophication (mineral 

and organic nutrient loading and subsequent

proliferation of plant life), resulting in decreased 

dissolved oxygen content. 

Benefits to water quality from herbicide treatments are 

associated with a reduced risk of fire and post-fire 

sedimentation. Additionally, control of invasive species 

in terrestrial and aquatic systems can provide long-term 

benefits to water quality with the return of more stable 

soils, attenuated nutrient cycling, and a return to normal 

fire cycles. 

Impacts to Water Quantity

Removal of vegetation through use of herbicides has the 

potential to affect water quantity by altering the 

magnitude of base flows and the frequency and 

magnitude of peak flows. Such effects would be most 

likely to occur as a result of large-scale removal of 

vegetation as a result of broadcast spraying. For some 

treatment areas, the removal of vegetation 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, large-scale removal of 

vegetation 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. Changes would persist

until the site was revegetated.

Impacts by Herbicide

The 2007 PEIS discusses the impacts to water resources 

for each of the 18 currently approved herbicides 

(USDOI BLM 2007a:4-29 to 4-34). The impacts of the 

three new herbicides are discussed in the following 

sections.

Aminopyralid

Aminopyralid is moderately persistent and has high 

mobility in most soils because of its low soil adsorption 

BLM Vegetation Treatments Three New Herbicides 4-17 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

values (Table 4-5; USEPA 2005c). Therefore, it is 

transported to surface water and groundwater. 

Breakdown by microbes in soil is the primary form of 

dissipation. Aminopyralid’s mobility and high water 

solubility suggest that the herbicide is prone to leaching 

(Lindenmeyer 2012). However, in past studies, leaching 

of aminopyralid has not been documented at levels 

below 1 foot (USEPA 2005b). 

In water, aminopyralid is stable and does not readily 

react with water, but is broken down by sunlight. The 

half-life by photolysis is very short, at 0.6 days (USEPA 

2005b). Therefore, it is expected that aminopyralid 

rapidly dissipates in clear, shallow surface water 

(USEPA 2005c). Within fast-moving water it rapidly 

dissipates through mixing. The major metabolic 

products of photolysis in water are oxamic acid and 

malonamic acid, neither of which would form in large 

concentrations, or are of concern from a toxicity 

standpoint (USEPA 2005b).

Once aminopyralid leaches down to anaerobic soil 

depths, degradation is likely to slow, which could be a 

factor in groundwater contamination (USEPA 2005c). 

At one study in Montana, aminopyralid was detected in 

groundwater in one of 23 wells (Schmidt and Mulder 

2009), indicating that there is some risk of groundwater 

contamination. It is expected that concentrations of 

aminopyralid in groundwater would be greatest in areas 

with a high water table and when rainfall happens 

immediately after application (USEPA 2005c). 

Neither aminopyralid nor its major metabolic products 

are included on the USEPA’s list of drinking water 

contaminants (USEPA 2013b). 

Because of its moderate persistence, high mobility, and 

low soil adsorption, aminopyralid has a high potential 

for surface water runoff. A Forest Service risk 

assessment for this active ingredient determined that in 

areas with high annual rainfall virtually all of the 

aminopyralid applied to a site could be transported 

offsite in surface runoff (Syracuse Environmental 

Research Associates, Inc. 2007).

Fluroxypyr

Based on soil adsorption characteristics, fluroxypyr is 

expected to have a high mobility in soil. However, it has 

a low potential for movement to groundwater because it 

is rapidly broken down by microbes in the soil (soil 

half-life is 1 to 3 weeks; California Department of 

Pesticide Regulation 2005; U.S. National Library of 

Medicine 2011). In field studies submitted to the 

USEPA, fluroxypyr was generally not found below a 

soil depth of 6 inches (USEPA 1998a), although this 

may vary depending on soil type and amount of rainfall. 

In sandy soils, the potential to leach to groundwater is 

much higher, and has been identified as a concern 

(NYSDEC 2006). Factors that influence the rate of 

fluroxypyr degradation in soils include soil microbes, 

organic matter, temperature, and soil moisture (Tao and 

Yang 2011).

In water, fluroxypyr does not readily break down by 

photolysis, but is biodegraded by microorganisms in the 

water and undergoes hydrolysis under certain 

conditions. The aquatic half-life is fairly short, at 5 to 14 

days (U.S. National Library of Medicine 2011).

The two major biotransformation products of fluroxypyr 

(a pyridine and a methoxypyridine), may be more

persistent in water than fluroxypyr (Health Canada 

2012). Studies of fluroxypyr in Sweden detected both 

fluroxypyr and pyridine in the groundwater beneath a 

railway treatment site (Cederlund et al. 2012). 

Neither fluroxypyr nor its two major biotransformation 

products are included on the USEPA’s list of drinking 

water contaminants (USEPA 2013b).

Because of its quick rate of breakdown, fluroxypyr is 

expected to have a low risk of surface water runoff. A 

Forest Service risk assessment for this active ingredient 

determined that up to 10 percent of applied herbicide 

would leave a site in surface water runoff in areas with 

clay soils and high rates of rainfall. For most other soils, 

about half this amount was expected to run off, with 

virtually no runoff from predominantly sandy soils 

(Syracuse Environmental Research Associates, Inc.

2009).

Rimsulfuron

As discussed in the soil resources section, rimsulfuron is 

unstable in soil, and therefore likely has a low risk of 

leaching to groundwater. The pH of the site conditions 

are likely a factor, with rimsulfuron less mobile in 

acidic conditions. Its metabolites may have a greater 

likelihood of contaminating groundwater, particularly 

the second metabolite, which is not readily degraded 

(Metzger et al. 1998).

There is little available information about rimsulfuron 

and its metabolites in terms of groundwater and 

surface water contamination. One study in sandy soils 

found no rimsulfuron in groundwater following an 

herbicide application, but did find the first metabolite 

BLM Vegetation Treatments Three New Herbicides 4-18 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

in the soil water at a depth of 3.3 feet, for as long as 3 

years, in concentrations unsafe for drinking water. 

Concentrations of the second metabolite were much 

lower (Rosenbom et al. 2010).

In aquatic systems, rimsulfuron is broken down via 

biodegradation and photodegradation. The 

biodegradation half-life is estimated at 10 days under 

aerobic conditions (NYSDEC 2009). 

Neither rimsulfuron nor its two metabolites are included 

on the USEPA’s list of drinking water contaminants 

(USEPA 2013b).

Given its fairly rapid dissipation rate in the soil, 

rimsulfuron has a low risk of surface runoff. If a rain 

event were to occur a week after application of 

rimsulfuron, only a very small portion of the active 

ingredient would be available for movement (NYSDEC 

1997). 

Impacts by Alternative

Under all alternatives, one goal of herbicide treatments 

would be to reduce noxious weeds and other invasive 

species to improve watershed condition and protect 

watersheds from wildfire. The BLM would also strive 

to increase the number/acreage/miles of properly 

functioning wetland/riparian areas to benefit water 

quality. Work to restore degraded habitat and native 

plant communities would be expected to benefit water 

resources under all alternatives. 

By minimizing fire risk through management of 

cheatgrass and other winter annual grasses, the risk of 

post-fire sedimentation into aquatic habitats would also 

be minimized. When soils are carried into lakes and 

streams, water quality diminishes as a function of 

increased sedimentation and turbidity (USDOI BLM 

2000). Additionally, some invasive vegetation, such as 

pinyon and juniper, reduces water availability for native 

species (USDOI BLM 1999). Furthermore, annual 

grasses reduce the overall vegetative cover in a 

watershed, relative to native grasses, which leads to 

reduced infiltration, increased runoff, and loss of soil 

moisture. Eventually, soils are transported to streams 

and other aquatic bodies, increasing sedimentation and 

reducing water quality. The benefits associated with 

herbicide treatments that reduce the cover of non-native 

invasive species would occur under all alternatives. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under the No Action Alternative, the BLM would 

continue its vegetation management programs using the 

current list of 18 herbicides. The use of individual 

herbicides may vary somewhat from historic usage 

based on identified future projects, as summarized in 

Table 2-4. The estimated total land area treated with 

herbicides would remain at 932,000 acres annually. The 

impacts under this alternative were summarized in the 

2007 PEIS (USDOI BLM 2007a:4-35). In general, 

herbicide treatments would provide benefits to water 

resources by managing invasive species that damage 

watersheds.

Approved aquatic herbicides would continue to be 

applied directly to water to control aquatic species. The 

2007 PEIS identified concerns associated with use of 

the known groundwater contaminants 2,4-D, bromacil, 

dicamba, diquat, diuron, hexazinone, and picloram. 

Other herbicides were identified as having the potential 

to leach to groundwater or be carried to surface water in 

stormwater runoff. 

Under this alternative, use of clopyralid, glyphosate, 

imazapic, tebuthiuron, and triclopyr would comprise 

herbicide treatments on approximately 73 percent of all 

acres treated. Based on information in the 2007 PEIS, 

glyphosate is a known groundwater contaminant, 

persists in aquatic environments, and may stimulate

algal growth in low concentrations. There are fewer 

concerns about the other herbicides in this list, although 

imazapic is believed to be a groundwater contaminant, 

and tebuthiuron has been detected in surface water. 

Concerns associated with use of these herbicides would 

continue under this alternative. The impact summary for 

this alternative in the 2007 PEIS was that there would 

be some risks to water resources from herbicide 

treatments, as well as benefits associated with 

watershed improvements.

Alternative B –Allow For Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, the extent of herbicide treatments 

would be the same as under the No Action Alternative, 

with associated risks to water resources over roughly

the same geographic area. However, the suite of 

herbicides used would be slightly different. 

Aminopyralid, fluroxypyr, and rimsulfuron would be 

BLM Vegetation Treatments Three New Herbicides 4-19 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

added to the list of herbicides used to treat vegetation. 

Therefore, the number of chemicals with the potential to 

impact water resources would increase under this 

alternative. None of the new herbicides are groundwater 

or drinking water contaminants of concern, although the 

potential for such contamination by these herbicides and 

their degradation products exists. 

Use of some previously-approved herbicides would 

decrease under this alternatives, primarily that of 

glyphosate, imazapic, and picloram. The use of the 

known groundwater and drinking water contaminants, 

glyphosate and picloram, would decrease by 7 percent 

and 4 percent, respectively, meaning that roughly 11 

percent fewer acres would be treated with these 

herbicides than under the No Action Alternative. Use of 

imazapic, a possible groundwater contaminant, would 

decrease by 10 percent. Use of all other currently 

approved herbicides would be the same as or within 3 

percent of the current level of usage.

Under this alternative, use of fluroxypyr would be low 

(approximately 1 percent of all acres treated), but use of 

aminopyralid and rimsulfuron would account for 26 

percent of all acres treated. As discussed in the Impacts 

by Herbicide section, there may be some risk of 

groundwater contamination associated with 

aminopyralid and the degradation products of 

rimsulfuron. Based on the available information, these 

risks are likely lower than those associated with 

glyphosate and picloram, indicating that effects to water 

resources may be reduced under this alternative, relative 

to the No Action Alternative. 

None of the new herbicides would be used to manage

aquatic vegetation. Therefore, the level of benefit to 

water resources from control of unwanted aquatic 

vegetation, such as Eurasian watermilfoil, would be the 

same as under the other alternatives. If availability of 

the new herbicides were to increase the efficacy of the 

BLM’s vegetation treatment programs, resulting in an 

improvement in watershed condition, water resources 

could receive a higher degree of benefit from treatment 

programs than under the No Action Alternative. 

Alternative C – No Aerial Application of New 

Herbicides

Under this alternative, total maximum herbicide use 

would be the same as under the other alternatives 

(932,000 acres), but aerial applications of aminopyralid, 

fluroxypyr, and rimsulfuron would not be allowed. The 

number of chemicals with the potential to impact water 

resources would be the same as under the Preferred 

Alternative. However, use of glyphosate, picloram, and 

imazapic would decrease by approximately 9 percent, 

which is less of a decrease than under the Preferred 

Alternative. Aminopyralid and fluroxypyr would only 

be used on an estimated 9 percent of treatment acres. 

Therefore, reduction in risks to water resources through 

a reduction in use of known contaminants would be less 

under this alternative than under the Preferred 

Alternative.

Watershed-level benefits to water resources could be 

slightly greater than under the No Action Alternative, 

and slightly less than under the Preferred Alternative. 

Not being able to apply the new herbicides aerially

would limit their usefulness in certain situations, 

although these needs would continue to be met through 

aerial applications of currently approved herbicides.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under Alternative D, total herbicide use would be the 

same as under the other alternatives. However, without 

the option of rimsulfuron, the percent of land area 

treated with the new herbicides would be the lowest of

all the action alternatives, at approximately 11 percent 

(10 percent for aminopyralid and 1 percent for 

fluroxypyr). This alternative is the closest to the No 

Action Alternative in terms of how much of each of the 

currently available herbicides would be used. Most of 

the currently available herbicides would be used at 

levels similar to those under the No Action Alternative, 

with the biggest reductions in use of picloram (4 percent 

reduction) and metsulfuron methyl (3 percent 

reduction). There could be some reduced risks to water 

quality as a result of a decrease in the use of picloram, 

but glyphosate would continue to be used at nearly the 

same level as under the No Action Alternative. 

The number of chemicals with the potential to impact 

water resources would be greater than under the No 

Action Alternative, but less than under the Preferred 

Alternative and Alternative C.

Watershed-level benefits would be similar to those 

under the No Action Alternative.

Mitigation for Herbicide Treatment 

Impacts

No new mitigation measures, or measures specific to the 

three new herbicides, are proposed for water resources. 

BLM Vegetation Treatments Three New Herbicides 4-20 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

The BLM’s SOPs to protect water resources would 

continue to be implemented. These include procedures 

designed to prevent accidental spills of herbicides into 

aquatic habitats.

Wetland and Riparian Areas

Introduction

Herbicide treatments have the potential to alter 

vegetation, hydrology, or soils in wetland and riparian 

areas, affecting the functions of these areas. However, 

herbicide treatments that control non-native species in 

wetland and riparian habitats would be beneficial. 

Invasive plant species are one cause of degradation in

the function of wetland and riparian areas.

Scoping Comments and Other Issues 

Evaluated in the Assessment

Scoping comments pertinent to wetland and riparian 

areas included those addressing soil resources, water 

resources and quality, and vegetation (see the Soil 

Resources, Water Resources and Quality, and 

Vegetation sections).

A few comments were specific to wetlands and riparian 

areas, including one that noted the importance of using 

aminopyralid in riparian areas to control invasive plants, 

and one concerned with residual effects of aminopyralid 

in vegetation in wetland and riparian areas. 

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. Wetlands and 

riparian areas adjacent to herbicide treatment sites can 

help filter herbicides from runoff through physical, 

chemical, and biological processes (Mitch and 

Gosselink 2000). Factors that influence herbicide fate in 

wetlands include the amount and type of vegetation, the 

amount of organic matter in the soil, oxygen 

availability, and populations of soil microbes (Stoeckel 

et al. 1997). 

Saturated wetland soils have chemical and biological 

characteristics that are different from well-drained 

upland soils, including oxidation-reduction status, pH, 

and organic content. The characteristics of wetland soils 

affect their capacity to adsorb, transport, and transform 

herbicides. The fate of herbicides in wetland soils 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. 

The rate of breakdown in anaerobic systems can be 

estimated by the measured anaerobic half-life (Table 

4-6). With the exception of fluroxypyr, anaerobic 

degradation processes are typically slower than the 

degradation processes in well-drained soils where 

oxygen is present. However, the soil type and other 

environmental conditions are also important factors.

TABLE 4-6

Anaerobic Half-life in Soil for Herbicides 

Analyzed in this PEIS

Herbicide Anaerobic Soil 

Half-life (days)

Aerobic Soil 

Half-life (days)

Aminopyralid 462-990 32-533

Fluroxypyr 3.5-14 7-23

Rimsulfuron 18 5 to 40

Sources: USEPA 2005c, NYSDEC 2009, U.S. National 

Library of Medicine 2011.

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 (AECOM 2014a,b; AECOM 

2015). 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).

The analysis of impacts to wetland and riparian areas 

assumes that the BLM would follow applicable SOPs 

identified in the 2007 PEIS:

• Survey for special status aquatic and riparian 

plant species before treating an area, at a time 

when the plants can be identified.

BLM Vegetation Treatments Three New Herbicides 4-21 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

• 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. Minimum buffer widths for herbicides 

not labeled for aquatic use are 100 feet for 

aerial, 25 feet for vehicle, and 10 feet for hand 

applications (larger buffers may be required if 

special status species are present).

Other SOPs would help minimize the risk of a spill into 

wetland habitats, including preparing a spill 

contingency plan in advance of treatments, mixing and 

loading herbicide products in an area where an 

accidental spill would not reach a water body, not 

rinsing spray tanks in or near water bodies, following 

product labels for use and storage, and having licensed 

applicators apply the herbicides.

Summary of Herbicide Impacts

None of the three active ingredients proposed for use 

are currently approved for direct aquatic applications. 

Therefore, the BLM’s minimum buffers would apply, 

unless ERAs indicate larger buffers are warranted, or 

project-specific NEPA analysis indicates that a smaller 

buffer is appropriate. Aminopyralid, fluroxypyr, and 

rimsulfuron can be applied in dry riparian areas, nonirrigation ditch banks, seasonally dry wetlands, and 

transitional areas between upland and lowland sites. 

Additionally, if aminopyralid receives an aquatic 

registration in the future, the buffers associated with its 

use near aquatic habitats could be reduced.

Based on the likely usage of the three active ingredients, 

wide-scale removal of riparian vegetation would not 

occur. Fluroxypyr and rimsulfuron would not typically 

be used near water, except possibly for spot treatments 

of certain target species. However, aminopyralid would 

be used in riparian treatments for selective removal of 

certain species (e.g., knapweeds), although extensive 

removal of riparian vegetation would be unlikely. If 

aminopyralid receives an aquatic registration in the 

future, reduced buffers near aquatic habitats would 

allow its use in targeting a variety of wetland and 

riparian species, such as purple loosestrife, Japanese 

knotweed, and saltcedar. In riparian areas and wetlands, 

aminopyralid would potentially provide an alternative to 

glyphosate, which is less selective and more likely to 

result in removal of non-target riparian and wetland 

vegetation.

A general discussion of impacts to wetlands and 

riparian areas from use of herbicides to control aquatic 

and riparian vegetation is provided in the 2007 PEIS 

(USDOI BLM 2007a:4-37 to 4-38). Herbicide 

treatments can improve habitat quality for fish and 

wildlife, improve hydrologic function, and reduce soil 

erosion. Herbicide treatments would focus on nonnative species that displace native vegetation and that 

alter wildlife habitat, hydrology and soil conditions. 

Many of the species targeted for control (such as purple 

loosestrife, reed canarygrass, and saltcedar) form dense 

monocultures that shade out native species and reduce 

wetland functions. Management of these species would 

be expected to increase the functions and values of 

treated wetlands and riparian areas. 

While loss of vegetation could lead to short-term 

impacts such as increased sedimentation and nutrient 

loading, and alteration of vegetation, water temperature, 

and hydrologic conditions, it is expected that these 

short-term impacts would be minimal given that 

extensive removal of riparian vegetation would be 

unlikely.

A general discussion of the impacts to wetlands and 

riparian areas from the use of herbicides in upland areas 

is provided in the 2007 PEIS (USDOI 2007a:4-40). 

Non-target wetland and riparian areas could be exposed 

to herbicides transported from upland areas via a variety 

of methods. The primary potential impacts would be 

loss of non-target native vegetation and contamination 

of water or soil, particularly as a result of an accidental 

spill. 

Aminopyralid

As discussed previously, aminopyralid could be used in 

dry wetlands and riparian areas. Therefore, any 

herbicide that remains adsorbed to soil particles could 

be released into the water if these areas become flooded 

or saturated following the treatments. Additionally, if 

aminopyralid receives an aquatic registration, it could 

be used in saturated conditions, and could enter the 

water directly as a result of incidental overspray. 

Aminopyralid does not have activity on submerged 

aquatic species, such as watermilfoil and water-thyme, 

and would not be applied directly to the water column 

to treat unwanted aquatic vegetation. However, it may 

BLM Vegetation Treatments Three New Herbicides 4-22 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

be effective at controlling riparian invasives. Field 

research trials support use of aminopyralid to manage

emerged shoreline invasive species (e.g., purple 

loosestrife, Japanese knotweed, and invasive thistle 

species; Peterson et al. 2013). 

Aminopyralid is effective against many invasive 

herbaceous broadleaf weeds, and may offer 

improvements in control of Russian olive and saltcedar. 

One study found that adding aminopyralid to triclopyr 

increased its control of these species without injuring 

desirable understory grass vegetation (Sluegh et al. 

2011).

Aminopyralid has a photodegradation half-life of 0.6 

days in aquatic systems (USEPA 2005c). In anaerobic 

systems, however, the active ingredient is persistent, 

with a half-life between 462 and 990 days (USEPA 

2005c). The half-life in sediment is 999 days (Yoder 

and Smith 2002). 

As described in the ERA for aminopyralid, non-target 

aquatic plants are not at risk for adverse effects from 

exposure to aminopyralid, even under direct spray and 

worst-case spill scenarios. However, non-aquatic plants 

(including riparian species and emergent wetland 

plants) would be at risk for adverse effects if a broadcast 

spray treatment were to occur near wetland and riparian 

habitats. Use of adequate buffers would be required to 

prevent adverse effects to sensitive riparian and wetland 

habitats under broadcast spray scenarios. These buffers 

are discussed in more detail in the Vegetation section 

(see Table 4-8).

Fluroxypyr

As discussed previously, fluroxypyr would have 

minimal use in wetland and riparian habitats, except for 

spot treatments of certain target species. It is not 

approved for use in aquatic habitats or wetlands when 

water is present. Therefore the amount of this active 

ingredient that is likely to be released to wetland and 

riparian areas under normal application scenarios is very 

small. Accidental spills or movement from adjacent 

upland areas could result in more of the active 

ingredient entering wetland or riparian habitats. 

Fluroxypyr is short-lived in anaerobic environments. In 

anaerobic soil the half-life is 14 days or less (National 

Library of Medicine 2011). In anaerobic aquatic 

habitats, the half-life is 8 days (USEPA 1998a). The 

breakdown products may persist for longer.

As described in the ERA for fluroxypyr, non-target 

aquatic plants are not at risk for adverse effects from 

fluroxypyr under direct spray or surface runoff 

scenarios. However, they would likely be harmed by an 

accidental spill of fluroxypyr into a pond or stream in 

which they occur. The risks of such a spill occurring 

would be reduced by applicable SOPs, as discussed 

earlier in this Wetland and Riparian Areas section. Nonaquatic plant species in wetlands and riparian areas 

would be at risk for adverse effects from spray drift at 

nearby upland habitats. Suitable buffers would be 

required to prevent adverse effects to non-target plants 

in sensitive riparian and wetland habitats. See Table 4-8 

and the Vegetation section for more information on 

buffers.

Algal growth may be stimulated at low fluroxypyr 

concentrations but depressed at higher concentrations 

(Zhang et al. 2011).

Rimsulfuron 

As discussed previously, rimsulfuron is not likely to be 

used much in or near wetland and riparian areas, except 

for spot treatments of certain target species. Similar to 

fluroxypyr, only small amounts of this chemical are 

likely to enter wetland and riparian areas under normal 

application scenarios, although larger amounts could 

enter these habitats as a result of an accidental spill or 

movement from an adjacent treatment site.

Rimsulfuron has a high rate of soil adsorption in soils 

with high organic content (Metzger et al. 1998). 

However, it is quickly degraded under anaerobic 

conditions. In anaerobic soil the half-life is 

approximately 18 days. In anaerobic aquatic habitats, 

the half-life is less than 2 days (NYSDEC 2009). 

Breakdown products may persist for longer.

According to the ERA, rimsulfuron poses a risk to nontarget aquatic plants under direct spray, accidental spill, 

spray drift, and certain surface runoff scenarios. Risks 

associated with surface runoff would be limited to 

aquatic plants in ponds, and would be greatest in areas 

with 50 inches of precipitation or more per year. Nonaquatic plants, such as riparian and emergent wetland 

species would also be at risk for adverse effects from 

treatments in nearby upland areas. These findings 

indicate that buffers are needed between treatment sites 

and wetlands/riparian areas to protect vegetation from 

unintended harm. These buffers are discussed in more 

detail in the Vegetation section and Table 4-8.

BLM Vegetation Treatments Three New Herbicides 4-23 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Impacts by Alternative

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under the No Action Alternative, the BLM would 

continue its ongoing vegetation management programs 

in 17 western states, and would be able to use the

current list of 18 approved herbicides for treatments. 

Impacts under this alternative would correspond to 

those discussed under the Preferred Alternative in the 

2007 PEIS (USDOI BLM 2007a:4-42). The total area 

receiving herbicide treatments would be 932,000 acres 

annually, of which approximately 10,000 acres would 

consist of aquatic and riparian habitat. Herbicides used 

to manage aquatic and riparian vegetation under this 

alternative could include 2,4-D, diquat, fluridone, 

glyphosate, and imazapyr, which are registered for 

aquatic uses; and dicamba, tebuthiuron, and triclopyr in 

riparian areas where contact with water can be avoided. 

Use of the currently approved herbicides would be 

associated with both beneficial and adverse effects to 

wetlands and riparian areas. There would be some risk 

for contamination of water and/or soils in these habitats 

as a result of herbicide applications or spills, as well as 

risks to non-target plant species from exposure to 

herbicides via various pathways.

Herbicide treatments that target invasive riparian and 

wetland plant species would be expected to benefit 

these habitats by promoting the reestablishment of 

native species and improving the functions provided by 

the targeted wetlands and riparian areas. The BLM 

would be able to control targeted invasive species (such 

as Eurasian water milfoil, water-thyme, purple 

loosestrife, and saltcedar) with the suite of herbicides 

available for use. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, the estimated area of wetland and 

riparian areas receiving herbicide treatments annually 

would be the same as under the No Action Alternative 

and the other action alternatives. However, 

aminopyralid, fluroxypyr, and rimsulfuron would be 

added to the list of herbicides available for use. Because 

none of the new active ingredients would be registered 

for direct applications to the water column, they would 

not be used to control invasive aquatic species. 2,4-D, 

diquat, fluridone, glyphosate, and imazapyr would 

continue to be used for these aquatic applications.

While fluroxypyr and rimsulfuron would receive minor 

use in wetland and riparian habitats, aminopyralid 

would be an important component of riparian and 

wetland treatments, particularly if it receives an aquatic

registration allowing incidental overspray into wetlands 

and aquatic habitats. The BLM has identified 

aminopyralid as a good alternative to glyphosate that is 

more selective and therefore less likely to harm target 

vegetation, and may be less of a concern in terms of 

persistence in groundwater and aquatic habitats (see the 

Water Resources and Quality section). However, 

aminopyralid persists much longer than glyphosate in 

anaerobic, wetland soils (462 to 990 days, versus 12 to 

70 days for glyphosate). Therefore, use of aminopyralid 

in and near wetland habitats may have a greater impact 

than glyphosate from an environmental persistence 

standpoint. Under this alternative, it is expected that use 

of glyphosate would be reduced, relative to the No 

Action Alternative. It is likely that the BLM would use 

aminopyralid to target knapweeds in riparian areas, as 

well as for other broadleaf invasive species. 

The addition of fluroxypyr and rimsulfuron may also 

reduce the usage of some other herbicides in wetland 

and riparian areas, but not to a substantial degree. 

Alternative C – No Aerial Application of New 

Herbicides

Alternative C is similar to the Preferred Alternative in 

that the same herbicides would be available for use, and 

the total area of wetland and riparian areas treated 

would be approximately 10,000 acres. As discussed in 

the 2007 PEIS (USDOI BLM 2007a:4-43), nearly all of 

the herbicide treatments in wetland and riparian areas 

are done using ground-based methods. Additionally, 

aerial applications of upland areas would be completed 

using the currently approved herbicides, so risks to 

wetlands and riparian areas from spray drift would be 

much the same as under the other alternatives, although 

different herbicides may be used than under 

Alternatives B and D. 

Benefits and risks to wetland and riparian areas would 

be much the same as under the Preferred Alternative. 

For ground-based treatments in wetlands and riparian 

areas, aminopyralid would likely be used instead of 

glyphosate in certain situations.

BLM Vegetation Treatments Three New Herbicides 4-24 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Effects to wetlands and riparian areas under Alternative 

D would be much the same as those under the Preferred 

Alternative. Rimsulfuron would not be available for use 

under Alternative D. However, since rimsulfuron would 

receive minimal use near wetlands and in riparian areas, 

there would be little difference in herbicide usage in 

these areas relative to the other alternatives. 

Aminopyralid would be used instead of glyphosate for 

certain treatments in and near wetlands and riparian 

areas, similar to the other action alternatives. Benefits 

and risks to wetland and riparian areas would also be 

much the same as under the other action alternatives. 

Mitigation for Herbicide Treatment 

Impacts

No mitigation measures have been developed that are 

specific to wetlands and riparian areas. The BLM’s 

SOPs to protect water resources and vegetation would 

also help protect riparian and wetland habitats. 

Additionally, mitigation measures for vegetation, 

specified in the next section, would help protect riparian 

and wetland habitats. These include utilizing adequate 

buffer zones between sensitive non-target vegetation 

and herbicide treatment areas, which in many cases 

would be applicable to riparian and wetland vegetation.

Vegetation

Introduction

The present-day composition and distribution of native 

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, and exposure), natural disturbance (e.g., insects, 

disease, fire, and wildlife browsing), and humanmanagement patterns (e.g., domestic livestock grazing). 

Non-native plant species have caused a decline in the 

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 fuels. Cheatgrass, which is 

widespread on public lands, burns more frequently than 

native vegetation types and is disproportionately 

represented in the largest fires, indicating that invasion 

of this species has substantially altered fire regimes 

(Balch et al. 2013).

Scoping Comments and Other Issues 

Evaluated in the Assessment

Numerous scoping comments received by the BLM 

pertain to vegetation, addressing both the beneficial 

effects associated with use of the three new herbicides 

to control weeds, and the potential adverse effects to 

non-target vegetation. Most comments discuss the 

efficacy and low impact of the herbicides proposed for 

use, and their low impact to native plant species relative 

to other herbicides that are currently being used by the 

BLM. Specifically, numerous comments identified the 

efficacy of rimsulfuron at controlling cheatgrass and 

medusahead rye, the efficacy of aminopyralid as a 

control of knapweed, thistles, and rush skeletonweed, 

and the efficacy of fluroxypyr on kochia.

Several comments were concerned about the effects to 

non-target vegetation from residual aminopyralid or 

fluroxypyr in manure and compost and other plant 

materials. One comment addressed the importance of 

reseeding of desirable species after treatments to 

promote recovery of native plant communities

following herbicide treatments. 

Standard Operating Procedures

Risks to non-target plants associated with herbicide use 

would continue to be minimized by following the SOPs 

listed in the 2007 PEIS, which are general procedures 

designed by the BLM to reduce potential unintended 

impacts to non-target vegetation from herbicide 

treatments. Examples of pertinent SOPs (with slight 

modifications since 2007) include the following: 

• Conduct pre-treatment surveys for sensitive 

habitat and special status species within or 

adjacent to proposed treatment areas, at a time 

when the plants can be found.

• 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, 

and colorants to obtain a uniform coverage.

BLM Vegetation Treatments Three New Herbicides 4-25 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

• 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 

vegetation will not be injured following 

application of the herbicide.

Additionally, the BLM would follow the mitigation 

measures that were adopted in the 2007 ROD (USDOI 

BLM 2007b: Table 2) for vegetation treatments 

involving the 18 currently approved herbicides. These 

mitigation measures include establishing herbicidespecific buffer zones, limiting aerial applications of 

certain active ingredients, and minimizing the use of 

terrestrial herbicides in watersheds with downgradient 

ponds and streams if potential impacts to aquatic plants 

are identified. Some of these measures would apply to 

treatments involving the three new active ingredients, 

including tank mixes that include the currently approved 

herbicides for which specific mitigation measures have 

been developed. 

These procedures would minimize impacts to plants and 

ecosystems on public lands from use of the new active 

ingredients to the extent practical. Long-term benefits to 

native plant communities from management of invasive 

plants would likely continue to outweigh any short-term 

negative impacts to native plants associated with 

herbicide use.

Impacts Assessment Methodology

The method of assessing impacts to non-target

vegetation from the three new herbicides was the same 

as the method described in the 2007 PEIS (USDOI 

BLM 2007a:4-45 to 4-46; Appendix C) for herbicides 

with BLM ERAs. A brief overview of the ERA process 

is presented here. Additionally, information about likely 

future herbicide treatments, provided by local field 

offices for development of the 2007 PEIS, was assumed 

to be applicable to the alternatives in this PEIS. This 

information includes the location, application method, 

vegetation type, and size of the treatment (in acres). 

Risk Assessment Methodology

Risk assessments evaluated the risks to terrestrial and 

aquatic non-target plants from herbicide exposure. Risk 

assessments consider assessment endpoints and 

associated measures of effect. The assessment endpoint 

is an expression of the value that is to be protected. In 

the case of non-target plants, assessment endpoints 

include mortality and negative impacts on growth, 

reproduction, or other ecologically important sublethal 

processes. For the most part, assessment endpoints 

reflect direct effects of the herbicide, although indirect 

effects were also considered.

Measures of effect are measurable changes in an 

attribute of an assessment endpoint (or its surrogate) in 

response to a stressor to which it is exposed (USEPA 

1998b). For the ERAs, these measures generally 

consisted of acute and chronic toxicity data (from 

pesticide registration documents and from the available 

scientific literature) for the most appropriate surrogate 

species.

Because the BLM applies herbicides in a variety of sites 

using a variety of application methods (e.g., via aircraft, 

vehicle, and backpack), the following exposure 

scenarios were considered to assess the potential 

ecological impacts of herbicides under a variety of uses 

and conditions: 

• Direct spray of the receptor.

• 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.

• Accidental spills to water bodies.

The AgDRIFT computer model was used to estimate 

off-site herbicide transport due to spray drift. The 

Groundwater Loading Effects of Agricultural 

Management Systems (GLEAMS) computer model was 

used to estimate off-site transport of herbicide in surface 

runoff and root zone groundwater transport. The 

AERMOD and CALPUFF computer models were used 

to predict the transport and deposition of herbicides 

adsorbed (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.

In order to address potential risks to plant receptors, 

Risk Quotients (RQs) were calculated. To help translate

RQs into estimates of risk, the calculated RQs were 

compared with Levels of Concern (LOCs) used by the 

USEPA in screening the potential risk of herbicides. For 

BLM Vegetation Treatments Three New Herbicides 4-26 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

plants, distinct USEPA LOCs are currently defined for 

the following risk categories:

• Acute high risk – the potential for acute risk is 

high.

• Acute endangered species – threatened, 

endangered, and proposed species may be 

adversely affected.

For the analysis presented in this PEIS, the LOC for

acute high risk (1) was used for typical terrestrial and 

aquatic plant species. Wherever the RQ exceeded the

LOCs, it was assumed that acute adverse effects to nontarget plant species could potentially occur under that 

exposure scenario. The methodology for determining 

risks to special status plant species is discussed later in 

this section, under the Special Status Plant Species 

subheading. 

Summary of Herbicide Impacts

Under all alternatives, treatments involving the new 

herbicides would be one component of the BLM’s 

larger vegetation management programs, which have 

been discussed in more detail in the 2007 PEIS and 

PER. As discussed in the 2007 PEIS (UDSI BLM 

2007a:4-47), the effectiveness of herbicide treatments in 

managing target plants and the extent of disturbance to 

plant communities varies by the herbicide selectivity, 

the extent and density of the infestation, the size of the 

application area, and the application method (e.g., aerial 

vs. ground). Individual plant sensitivities, physical 

features (e.g., soil type and slope), and weather 

conditions (e.g., temperature, humidity, and wind speed) 

at the time of application also factor into the success of 

a treatment. Additionally, other treatments or herbicides 

used in conjunction with treatments involving 

aminopyralid, fluroxypyr, and rimsulfuron would 

influence the effectiveness of the overall treatment.

Herbicide treatments would likely affect the plant 

species composition of an area and might affect plant 

species diversity. The discussions in this section focus 

on the impacts of the three new herbicides on vegetation 

(both target and non-target species). General discussions 

about the impacts of herbicide treatments on vegetation 

can be found in the 2007 PEIS (USDOI BLM 2007a:4-

47 to 4-48). For treatments involving one or more of the 

three new herbicides, active ingredients that adversely 

affect plants could come into contact with vegetation 

via direct spraying, drift, runoff, wind transport, or 

accidental spills. Potential impacts include mortality, 

reduced productivity, and abnormal growth. These

exposure pathways and associated risks to non-target 

plants were evaluated in risk assessments for the three 

herbicides (AECOM 2014a,b; AECOM 2015).

Impacts of Aminopyralid

Target Plants

Aminopyralid is a post-emergence, selective herbicide 

that is used to manage invasive annual, biennial, and 

perennial species. It is a plant growth regulator that 

binds to receptor sites normally used by the plant’s 

natural growth hormones, causing death of the plant. 

Anecdotal evidence and controlled studies of 

aminopyralid have found it to be effective at controlling 

yellow starthistle, Russian knapweed, various thistles, 

rush skeletonweed, and other invasive plants of 

rangelands (DiTomaso and Kyser 2006; Enloe et al. 

2008; Bell et al. 2012). Other species controlled by 

aminopyralid include oxeye daisy, Mediterranean sage, 

and Japanese and other large knotweeds (DiTomaso et 

al. 2013). The BLM has identified this herbicide for its 

activity on difficult-to-control species in rangelands, 

among other uses. It is an alternative to other growth 

regulator herbicides that are commonly used on

broadleaf weeds, such as picloram, clopyralid, 2,4-D, 

and dicamba. Studies have also found aminopyralid to 

be as or more effective than the currently approved 

growth regulator herbicides at lower application rates 

(Enloe et al. 2007, 2008; Bell et al. 2012).

Aminopyralid has a higher specific activity than other 

growth regulator herbicides, so less of it needs to be 

used to achieve the same result (Iowa State University 

2006). In mixtures with other active ingredients, it can 

be used on hard-to-control species like poison hemlock 

and catsears (DiTomaso et al. 2013).

There is some evidence that aminopyralid may be 

effective against certain annual grasses when applied at 

higher application rates pre- or early post-emergence 

(DiTomaso 2012). At sites representative of annual 

grasslands in California, it has been shown to control 

medusahead rye and result in increased cover of more 

desirable annual forage species, and may also have 

utility in suppressing cheatgrass (DiTomaso 2012). 

Additionally, aminopyralid may have a sterilizing effect 

on annual grasses, and appears to reduce seed 

production in cheatgrass (Rinella et al. 2013).

Non-Target Plants

Because aminopyralid is used to manage weedy 

broadleaf species, it poses a risk to non-target native 

BLM Vegetation Treatments Three New Herbicides 4-27 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

forbs and other desirable species in treatment areas. 

Generally speaking, it is a selective herbicide, falling 

between picloram and clopyralid in terms of selectivity 

(Iowa State University 2006). Studies with 

aminopyralid indicate that some native species are more 

tolerant to aminopyralid than others (Mikkelson and 

Lym 2013), indicating that the native species 

composition of treatment sites could be altered by the 

use of aminopyralid. Based on its documented control 

of invasive plants, key flowering plant families that are 

affected by aminopyralid include the Asteraceae (aster), 

Fabaceae (legume), and Polygonaceae (buckwheat) 

families. Additionally, the timing of a treatment may 

influence which native species will be most tolerant to 

aminopyralid (Halstvedt et al. 2011). In general, this 

herbicide is likely to select for perennial grass species 

and more resistant forb species. However, there is also 

evidence that use of aminopyralid causes an overall 

increase in the relative cover and dominance of native 

species (Green et al. 2011). Reduction in cover of nonnative species and an increase in native species would 

have a long-term beneficial effect at treatment sites.

One study documented adverse effects to forest 

communities from use of aminopyralid. Aminopyralid 

treatments in ponderosa pine stands (trees 5 to 10 years 

old, at higher rates than those proposed by the BLM)

can result in injury to ponderosa pine trees, leading to 

decreased canopy volume and variable growth patterns 

(Wallace et al. 2012).

As stated on the herbicide label, aminopyralid may 

impact non-target broadleaf plants indirectly if urine or 

manure from animals that graze on treated pasture 

within 3 days of the herbicide application comes into 

contact with these plants (Iowa State University 2006). 

Aminopyralid is persistent in plant materials, and may 

remain in undigested remains of treated vegetation for

more than 2 years (Oregon State University 2009, Dow 

AgroSciences 2014). This persistence in plant materials 

is generally a concern for crops and other plantings that 

are treated with compost that contains plant residues or 

hay or straw from treated areas. However, it is possible 

that some localized impacts to non-target native plants 

could occur if livestock or wildlife graze in treated areas 

and then release their waste materials on desirable 

broadleaf native species. 

The risk assessment for aminopyralid indicates that 

aminopyralid poses a high risk to non-target plants 

within the treatment area. As shown in Table 4-7, risks

for adverse effects to terrestrial plants would be high if 

there was direct exposure to aminopyralid as a result of

a direct spray (as part of a treatment or accidental) or an 

accidental spill. Therefore, it is likely that some nontarget broadleaf species would be adversely affected if 

they are present in the treatment area. For non-target 

aquatic plants, however, ERAs predicted no risk under 

direct spray or spill scenarios. Aminopyralid is not 

approved for aquatic uses, but is likely to receive a 

registration that addresses incidental overspray into 

aquatic habitats. These risk assessment results indicate 

that use indicate that use of aminopyralid right up to the 

water’s edge would not harm aquatic plants.

Apart from direct spray scenarios, risks to terrestrial 

plants would generally be low. Risks associated with 

off-site drift decrease as the distance from the treatment 

site increases and the application height gets lower 

(plane to helicopter to high boom to low boom). The 

buffer widths shown in Table 4-8 indicate the distances

within which adverse effects to non-target terrestrial 

plants would be expected to occur for the various 

application scenarios. For aerial applications, buffer 

distances range from 1,200 to 1,800 feet, depending on 

the application rate and type of aircraft used. Buffer 

distances for ground applications are much lower, 

ranging from 25 to 400 feet.

For surface runoff and root-zone groundwater flow 

scenarios, no risks to non-target terrestrial or aquatic 

plants were predicted. The GLEAMS model used to 

complete this portion of the risk assessments considered 

a variety of soil types and annual precipitation rates.

For wind erosion scenarios, no risks were predicted for 

non-target terrestrial plants under the majority of the 

evaluated conditions. Low risk was predicted for one of 

the modeled watersheds, with affected plants at a 

distance of 1.5 kilometers (0.9 mile) from the original 

application site. The modeled watershed was Medford, 

Oregon, a forested site with loam soils, where the 

presence of tall vegetation caused the model to predict 

relatively high rates of deposition. 

Impacts of Fluroxypyr

Target Plants

Fluroxypyr is a selective, post-emergent herbicide that 

is used to manage broadleaf species in rangelands and 

other areas (see Table 2-2). It is in the pyridine class of 

herbicides, and disrupts plant cell growth by inducing 

auxin-like responses. It is often used in industrial sites, 

along roads and railroads, and along ROWs. Based on 

its documented control of weeds, key flowering plant 

BLM Vegetation Treatments Three New Herbicides 4-28 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-7

Risk Categories Used to Describe Typical Herbicide Effects to Vegetation According 

to Exposure Scenario and Ecological Receptor Group

Application Scenario Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Typ Max Typ Max

Direct Spray/Spill

Terrestrial plants

H2 H H H H H

[1:1] [1:1] [1:1] [1:1] [1:1] [1:1]

Special status terrestrial plants

H H H H H H

[1:1] [1:1] [1:1] [1:1] [1:1] [1:1]

Aquatic plants pond

0 0 0 L H M

[2:2] [4:4] [2:2] [2:4] [1:2] [2:4]

Aquatic plants stream

0 0 0 0 H H

[2:2] [2:2] [2:2] [2:2] [1:2] [1:2]

Off-Site Drift

Terrestrial plants

L L L L L L

[10:18] [10:18] [11:18] [11:18] [9:18] [9:18]

Special status terrestrial plants

L L L L L L

[10:18] [10:18] [13:18] [11:18] [9:18] [8:18]

Aquatic plants pond

0 0 0 0 0 0

[36:36] [36:36] [36:36] [36:36] [24:36] [23:36]

Aquatic plants stream

0 0 0 0 0 0

[36:36] [36:36] [36:36] [36:36] [24:36] [23:36]

Surface Runoff

Terrestrial plants

0 0 0 0 0 0

[42:42] [42:42] [42:42] [42:42] [42:42] [42:42]

Special status terrestrial plants

0 0 0 0 0 0

[42:42] [42:42] [42:42] [42:42] [42:42] [42:42]

Aquatic plants pond

0 0 0 0 0 0

[84:84] [84:84] [84:84] [84:84] [55:84] [54:84]

Aquatic plants stream

0 0 0 0 0 0

[84:84] [84:84] [80:84] [84:84] [84:84] [84:84]

Wind Erosion

Terrestrial Plants 0 0 0 0 0 0

[9:9] [8:9] [9:9] [8:9] [8:9] [8:9]

Special status terrestrial plants 0 0 0 0 0 0

[8:9] [8:9] [8:9] [7:9] [8:9] [8:9]

1Typ = Typical application rate; and Max = Maximum application rate.

2 Risk categories: 0 = No risk (majority of RQs < applicable LOC); L = Low risk (majority of RQs 1-10 times the applicable LOC); M = Moderate risk 

(majority of RQs 10-100 times the applicable LOC); and H = High risk (majority of RQs >100 times the applicable LOC). 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. For some “no risk” 

exposure groups, RQs for one or more scenarios exceeded the applicable LOC. The reader should consult the risk tables in Chapter 4 of the ERAs 

(AECOM 2014a,b; AECOM 2015) to determine the specific scenarios that result in the displayed level of risk for a given receptor group. The number 

in brackets represents the number of RQs in the indicated risk category: number of scenarios evaluated.

BLM Vegetation Treatments Three New Herbicides 4-29 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-8

Buffer Distances to Minimize Risk to Non-target Vegetation from Off-site Drift

Application Scenario Aminopyralid Fluroxypyr Rimsulfuron

Buffer Distance (feet) from Non-Target Terrestrial Plants

Typical Application Rate

Plane1 1,300 feet 1,200 feet 1,600 feet

Helicopter1 1,200 feet 900 feet 1,400 feet

High Boom2 200 feet 400 feet 400 feet

Low Boom2 25 feet 100 feet 100 feet

Maximum Application Rate

Plane 1,800 feet 1,500 feet 1,900 feet

Helicopter 1,600 feet 1,400 feet 1,600 feet

High Boom 400 feet 600 feet 700 feet

Low Boom 100 feet 400 feet 400 feet

Buffer Distance (feet) from Terrestrial Threatened, Endangered, and Sensitive Plants

Typical Application Rate

Plane 1,800 feet 1,200 feet 1,600 feet

Helicopter 1,600 feet 900 feet 1,400 feet

High Boom 400 feet 400 feet 400 feet

Low Boom 100 feet 100 feet 100 feet

Maximum Application Rate

Plane 2,000 feet 1,500 feet 1,900 feet

Helicopter 1,700 feet 1,500 feet 1,600 feet

High Boom 600 feet 700 feet 700 feet

Low Boom 400 feet 600 feet 400 feet

Buffer Distance (feet) from Non-Target Aquatic Plants3

Typical Application Rate

Plane NA4 NA 1,300 feet

Helicopter NA NA 1,000 feet

High Boom NA NA 200 feet

Low Boom NA NA 100 feet

Maximum Application Rate

Plane NA NA 1,400 feet

Helicopter NA NA 1,800 feet

High Boom NA NA 300 feet

Low Boom NA NA 100 feet 1Aerial applications over both forested and non-forested land were considered in the ERAs. The largest buffer distances are presented in this table. 2 High boom is 50 inches above ground and low boom is 20 inches above ground. 3Aquatic plants in ponds and streams were considered in the ERAs. The largest buffer distances are presented in this table. 4NA means that no buffers are required, since direct spray of plants was not predicted to result in adverse effects. However, a direct spray into an aquatic 

habitat is not an approved use of these herbicides.

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.

BLM Vegetation Treatments Three New Herbicides 4-30 January 2016

Draft Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

families that are affected by fluroxypyr include the 

Asteraceae (aster), and Fabaceae (legume) families.

The BLM has identified the effectiveness of this 

herbicide on annual and biennial weeds, particularly 

when tank-mixed with another herbicide such as 2,4-D, 

dicamba, metsulfuron methyl, or triclopyr. It would be 

used to manage species such as weedy (annual) kochia,

mustards, pricklypear, ragweed, leafy spurge, and 

invasive blackberry. Fluroxypyr has been shown to 

have a synergistic effect when mixed with 2,4-D to 

control certain broadleaf weeds (Smith and Mitra 2006), 

and to improve control of leafy spurge when mixed with 

picloram (Peterson 1989). Fluroxypyr mixed with 

picloram has also been shown to control cholla and 

pricklypear, which can become dense on desert 

grassland sites as a result of overgrazing (Cummings 

and Duncan 2009).

Fluroxypyr has been identified as an option for 

addressing weeds that are resistant to herbicides with 

different modes of action. Its uses would likely include 

oil and gas sites where resistance to currently approved 

herbicides could be a problem. For instance, kochia that 

is resistant to ALS-inhibiting herbicides can be treated 

with fluroxypyr, although kochia can also develop a 

resistance to fluroxypyr (Montana State University 

Extension 2011).

Non-Target Plants

Fluroxypyr is a selective herbicide that controls 

broadleaf species. Therefore it poses a risk to non-target 

forbs, as well as desirable woody species in treatment 

areas. Because fluroxypyr is often tank-mixed with 

other active ingredients, its risk for non-target effects 

should be considered in conjunction with those of the 

other active ingredients.

Fluroxypyr would be used at oil and gas sites or other 

locations where complete removal of vegetation is 

desired. In these situations, non-target plants would not 

be present within the treatment area.

The risk assessment for fluroxypyr indicates that this 

active ingredient poses a high risk to non-target 

terrestrial plants through direct spray scenarios (Table 

4-7). It is assumed that direct spray of some non-target 

vegetation within the treatment area (if present) would 

occur, particularly if fluroxypyr is broadcast sprayed 

over a large area where desirable broadleaf species are 

present and are susceptible at the time of treatment. 

In the case of aquatic habitats, direct spray into a pond 

or a stream would not pose a risk to non-target aquatic 

plant species. Therefore, standard buffers between 

treatment areas and aquatic habitats would be sufficient 

to prevent harm to aquatic plants. However, an 

accidental spill of a large quantity of fluroxypyr (i.e., an 

entire load of herbicide mixed for an application) into a 

pond would pose a risk to non-target aquatic plants. 

These risks would be minimized by SOPs, which 

include conducting mixing and loading operations in 

areas where an accidental spill would not contaminate 

aquatic habitats.

Risks to terrestrial plants from off-site drift are 

generally low, and would be greatest for aerial 

applications of fluroxypyr. Suitable buffer distances to 

protect non-target terrestrial plants range from 100 feet 

for ground applications with a low boom to 1,500 feet 

for certain airplane applications (Table 4-8). No risks to 

terrestrial plants were predicted for surface runoff 

exposure scenarios.

No risks to non-target aquatic plants were predicted for 

exposures involving off-site drift, surface runoff, or 

root-zone groundwater flow under a variety of site 

conditions.

For wind erosion scenarios, no risks were predicted for 

non-target terrestrial plants under the majority of the 

evaluated conditions. Low risk was predicted for the 

Medford, Oregon modeled watershed, with affected 

plants at a distance of 1.5 km from the original 

application site.

Additional effects to certain non-target plant species 

could occur if populations of pollinators were harmed 

by herbicide spraying. Based on ERAs, fluroxypyr 

poses a low risk to pollinators under direct spray 

scenarios. However, ERAs did not identify risks to 

pollinators from use of aminopyralid or rimsulfuron.

Impacts of Rimsulfuron

Target Plants

Rimsulfuron is a selective, ALS-inhibiting herbicide 

that controls target weeds by inhibiting the biosynthesis 

of certain amino acids. It is applied both pre- and postemergence, and is active in both the xylem and the 

phloem of the plant. Invasive plants targeted by this 

active ingredient include cheatgrass, medusahead rye, 

and other annual grasses that have invaded public lands 

in the western U.S. The BLM is proposing to use this 

BLM Vegetation Treatments Three New Herbicides 4-31 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

active ingredient extensively, based on reports that it is 

effective at controlling winter annual grasses. 

Rimsulfuron is effective against cheatgrass and 

Japanese brome in the fall pre-emergence, or post 

emergence in the fall or spring. It provides a longer 

window of control than imazapic, although it must be 

used at the highest label rates for effective spring 

applications. Rimsulfuron can also be used to control 

larger cheatgrass plants than imazapic (Beck, No date).

The effectiveness of rimsulfuron at controlling 

cheatgrass and medusahead rye has been documented 

(Zhang et al. 2010), although there is conflicting 

evidence about its effectiveness relative to currently 

approved active ingredients (primarily imazapic). Some 

studies with rimsulfuron indicate that it is not as 

effective at controlling cheatgrass as either of the 

currently approved herbicides imazapic or sulfometuron 

methyl (Clements and Harmon 2013). However, there is 

also evidence that rimsulfuron is more effective than 

imazapic under certain conditions (Hirsch et al. 2012).

Non-Target Plants

Rimsulfuron is a selective herbicide that targets annual 

grasses and other annual species. Therefore, it has 

minimal effects on perennial grasses and other desirable 

perennial species. A study in northeastern California 

rangelands found that rimsulfuron effectively controlled 

cheatgrass and medusahead rye without substantially 

impacting sagebrush and desirable perennial grasses 

such as squirreltail (Zhang et al. 2010). Additionally, 

there is some evidence that application of rimsulfuron 

can result in an increase in perennial grass cover at 

treatment sites, compared to no discernable effect by 

imazapic (Hergert et al 2012). Therefore, rimsulfuron 

may benefit perennial non-target plant species, with less 

post-treatment restoration needed.

Based on information from the ERA, rimsulfuron poses 

a high risk to non-target terrestrial plants under direct 

spray scenarios (Table 4-7). Therefore, it is likely that 

some native plant species within the treatment area (if 

present) would be affected by treatments involving

rimsulfuron, particularly as a result of broadcast spray 

applications. 

An accidental direct spray of rimsulfuron into an 

aquatic habitat (stream or pond), or a spill of 

rimsulfuron into a pond, would pose a high risk for 

adverse effects to non-target aquatic plants. The risk of 

spills and accidental direct spray would be minimized 

through the use of SOPs. 

Non-target terrestrial vegetation would be at a low risk 

for adverse effects from off-site drift of rimsulfuron 

from treatment sites. Based on ERAs, buffers of 100 to 

1,900 feet (depending on the application) would be 

necessary to protect sensitive vegetation from adverse 

effects from herbicide treatments with rimsulfuron

(Table 4-8). 

Table 4-7 indicates that there is no risk to aquatic 

vegetation from off-site drift, based on information 

provided in the ERA. While there is some indication 

that chronic (long-term) exposure to rimsulfuron 

following off-site drift could adversely affect aquatic 

plants, the modeled scenarios are overly conservative 

because a chronic exposure is unlikely, and they do not 

consider flow, adsorption to particles, or degradation of 

the herbicide over time. The buffers presented in Table 

4-8 represent the distance beyond which there would be 

no risk to aquatic plants under any of the modeled

scenarios.

There are no predicted risks to non-target terrestrial or 

aquatic plants in streams as a result of surface runoff of 

rimsulfuron from a nearby treatment site. In the pond 

setting, however, chronic exposures to surface runoff of 

this herbicide could potentially affect aquatic plants 

under certain site conditions. Modeled conditions that 

were associated with adverse effects via surface runoff 

included high levels of precipitation (25 inches or more 

a year for sandy soils, 50 inches or more a year for loam 

soils, and 100 inches or more a year for clay soils). 

For wind erosion scenarios, no risks were predicted for 

non-target terrestrial plants under the majority of the 

evaluated conditions. Low risk was predicted for the 

Medford, Oregon modeled watershed, with affected 

plants at a distance of 1.5 kilometers from the original 

application site.

Impacts of Tank Mixes and other Mixtures

Mixtures of more than one herbicide are often used to 

increase the efficacy of a treatment or to control a wider 

range of target species without requiring multiple 

applications. Because pre-mixes and tank mixes often 

include active ingredients with more than one mode of 

action, they can provide better control of a target species 

than a single active ingredient. Use of herbicide 

mixtures is also one strategy for avoiding and managing 

herbicide-resistant invasive plants (Montana State 

University Extension 2011). Some species targeted for 

control by the BLM (e.g., marestail, pigweed, and

kochia) have begun to exhibit resistance to currently 

approved herbicides. 

BLM Vegetation Treatments Three New Herbicides 4-32 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

The ERAs for aminopyralid, fluroxypyr, and 

rimsulfuron did not analyze the potential effects to nontarget plants from mixtures involving these herbicides. 

Tank mixes were discussed in Chapter 2 of this PEIS, in 

the section Herbicide Formulations Used by the BLM 

and Tank Mixes. Aminopyralid and fluroxypyr would 

likely be mixed with numerous other previously 

approved herbicides, but rimsulfuron would usually be 

applied on its own.

Some mixtures involving the three new active 

ingredients could pose a greater risk to non-target plants 

than treatments involving any of these herbicides alone. 

Certain plant species may be particularly sensitive to 

mixtures. Conversely, use of one of the three new 

herbicides in a mixture in the place of a more harmful 

herbicide would likely result in a reduced risk to nontarget plants.

There is uncertainty associated with the use of mixtures, 

as the herbicides in a mixture may not interact in an 

additive manner; some interactions may be antagonistic 

and others may by synergistic. In general, buffers for 

the formulated product will be based on the active 

ingredient that requires the greatest buffer distance.

Impacts by Ecoregion 

Table 4-9 provides a summary of the estimated percent 

of the total acres treated using herbicides within each 

ecoregion. The table also indicates how the treatments 

would be spread out among the various vegetation 

subclasses and macrogroups within each ecoregion. The 

information provided in Table 4-9 updates Table 4-16 

from the 2007 PEIS to reflect the new vegetation 

classification system utilized by the BLM. The 

treatment goals and associated target geographic areas 

and vegetation are the same as those identified for the 

Preferred Alternative in the 2007 PEIS. Table 4-9 is

applicable to all four of the alternatives being 

considered in this PEIS.

The majority (71 percent) of herbicide treatment acres 

would be in the Temperate Desert Ecoregion, in 

shrubland, grassland, and steppe macrogroups. Many 

treatments in these areas would have the goal of 

restoring fire-damaged lands in the Great Basin, 

improving sagebrush communities, and replacing 

invasive annual grasses with native bunchgrasses and 

forbs. Treatments may involve the management of such 

species as sagebrush, rabbitbrush, and other shrub 

species, annual grasses, and undesirable perennial forbs.

Rimsulfuron would likely receive wide use in this

ecoregion for managing invasive annual grasses, 

particularly cheatgrass and medusahead rye, in various 

plant community types. Aminopyralid and fluroxypyr 

would typically be used in tank mixes to manage 

broadleaf rangeland weeds such as yellow starthistle, 

knapweeds, and annual kochia. Treatments to manage 

invasive plant species can be successful with the 

currently approved herbicides, but the availability of the 

three new herbicides would allow the BLM more

flexibility when designing treatments.

An additional 25 percent of herbicide treatment acres 

would be in the Temperate Steppe and Subtropical 

Steppe Ecoregions, primarily in grassland, shrubland, 

steppe, and chaparral macrogroups. In the Temperate 

Steppe ecoregion, herbicide treatments would focus on 

management of invasive annual and perennial grasses 

and forbs, including cheatgrass, leafy spurge, 

knapweeds, and thistles. All three of the new active 

ingredients could be utilized for certain identified target 

species. In the Subtropical Steppe Ecoregion, 

rimsulfuron would be a new option for managing 

infestations of invasive annual grasses in sagebrush and 

pinyon-juniper communities, and would help to reduce 

wildfire risk in these habitats. Similar to the Temperate 

Steppe Ecoregion, the three new herbicides would offer 

the BLM more options for meeting its treatment goals in 

the Subtropical Steppe Ecoregion. 

Impacts by Alternative

The primary goals of herbicide treatments would be to 

control infestations of invasive plants and help restore 

natural fire regimes. Other goals might be to improve 

safety and protect infrastructure (e.g., controlling 

vegetation along roadsides or at oil and gas sites).

Herbicides would commonly be used on rangelands 

infested by annual grasses, such as cheatgrass and 

medusahead rye, followed by revegetation with 

perennial grasses and forbs, as needed. Herbicides 

would also be used to suppress or thin shrubs such as 

sagebrush in favor of herbaceous vegetation. In some 

areas, herbicide treatments might reduce the vigor or 

cover of perennial grasses and forbs over the short term, 

but perennial grass and forb communities should 

improve over the long term as shrub stands are thinned 

to allow more light and nutrients to reach the understory 

and competition with annual grasses and forbs is 

reduced. In most cases, multiple treatments and 

restoration would be necessary to recover native plant 

communities and restore natural fire regimes.

BLM Vegetation Treatments Three New Herbicides 4-33 January 2016

Final Programmatic EIS
BLM Vegetation Treatments Three New Herbicide

ENVIRONMENTAL CONSEQUENCES

4-34 January 2016

Final Programmatic EIS

TABLE 4-9 

Projected Herbicide Treatments1

, as a Percent of Total Acres Treated, in Each Ecoregion for 

Each Vegetation Macrogroup Under All Alternatives

Vegetation 

Subclass(es)2 Vegetation Macrogroups2

Ecoregion

TundraSubarcticMarineMediterraneanSubtropical DesertSubtropical SteppeTemperate DesertTemperate Steppe

Temperate Forest

California Forest and Woodland

Californian-Vancouverian Foothill and Valley Forest and Woodland

Southern Vancouverian Montane and Foothill Forest

0 0 0 82-83 0 0 0 0 

Californian-Vancouverian Foothill and Valley Forest and Woodland

Vancouverian Lowland and Montane Rainforest 0 0 79 0 0 0 0 0 

Madrean Warm Montane Forest and Woodland 0 0 0 0 5 0 0 0 

Northern Rocky Mountain Lower Montane and Foothill Forest

Southern Rocky Mountain Lower Montane Forest

Intermountain Singleleaf Pinyon-Western Juniper Woodland

Rocky Mountain Two-Needle Pinyon-Juniper Woodland

0 0 0 0 0 0 3-4 1-2 

Rocky Mountain Two-Needle Pinyon-Juniper Woodland 0 0 0 0 0 8-9 0 0 

Mediterranean Scrub 

and Grassland; 

Temperate and Boreal 

Shrubland and

Grassland

California Chaparral

Cool Interior Chaparral 0 0 0 8 0 0 0 0 

California Annual and Perennial Grassland 0 0 0 <1 0 0 0 0 

California Ruderal Grassland and Meadow 0 0 0 10 0 0 0 0 

Temperate Forest; 

Temperate & Boreal 

Shrubland & 

Grassland; 

Warm Semi-Desert 

Scrub & Grassland

Northern Rocky Mountain-Vancouverian Montane and Foothill 

Grassland and Shrubland

Southern Rocky Mountain Montane Grassland and Shrubland

0 0 0 0 0 0 20-21 44

Southern Vancouverian Lowland Grassland and Shrubland 0 0 21 0 0 0 0 0 

Northern Rocky Mountain-Vancouverian Montane and Foothill 

Grassland and Shrubland

Southern Rocky Mountain Montane Grassland and Shrubland

Great Plains Mixedgrass Prairie and Shrubland

Great Plains Shortgrass Prairie and Shrubland

0 0 0 0 0 0 0 26
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-35 January 2016

Final Programmatic EIS

TABLE 4-9 (Cont.) 

Projected Herbicide Treatments1

, as a Percent of Total Acres Treated, in Each Ecoregion for 

Each Vegetation Macrogroup Under All Alternatives

Vegetation 

Subclass(es)1 Vegetation Macrogroups2

Ecoregion

TundraSubarcticMarineMediterraneanSubtropical DesertSubtropical SteppeTemperate DesertTemperate Steppe

Temperate Forest; 

Temperate and Boreal 

Shrubland and

Grassland; 

Warm Semi-Desert 

Scrub & Grassland

(cont.)

Great Plains Shortgrass Prairie and Shrubland

Apacherian-Chihuahuan Semi-Desert Grassland and Steppe 0 0 0 0 0 33 0 0 

Warm Interior Chaparral 0 0 0 0 26 43-44 0 0 

Chihuahuan Desert Scrub

Southern Plains Scrub Woodland and Shrubland 0 0 0 0 32 4 0 0 

Cool Semi-Desert 

Scrub and Grassland

Great Basin and Intermountain Dry Shrubland and Grassland

Great Basin and Intermountain Tall Sagebrush Shrubland and Steppe 0 0 0 0 0 0 58-59 0 

Annual graminoid or forb3 0 0 0 0 0 8 0 2

Perennial forb3 0 0 0 <1 <1 1 0 0

Riparian/wetland3 0 0 0 <1 36 4 1 0

More than one subclass 0 0 0 0 0 0 18-19 26

Total for all ecoregions 0 0 <1 4 <1 9 71 16 1 Refers to treatments with all available herbicides. 2 See Table 3-4, the Vegetation section in Chapter 3, and Appendix D for a description of vegetation subclasses and macrogroups. 3 General vegetation types for which no macrogroups exist in these ecoregions.
ENVIRONMENTAL CONSEQUENCES

All four of the alternatives analyzed in this PEIS 

involve the same geographic area as far as herbicide 

treatments, as well as the same assumed total acreage of 

herbicide treatments annually (932,000 acres). Under all 

alternatives, the breakdown in usage by ecoregion 

(Table 4-9) would also be the same. The primary 

differences among the alternatives are associated with 

the herbicides that would be available for use, and the 

relative proportion of their use (summarized in Table 

2-4). 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under the No Action Alternative, the BLM would 

continue current vegetation management programs in 17 

western states, and would treat an estimated 932,000 

acres per year using both ground-based and aerial 

applications of the 18 previously approved herbicides. 

The impacts to vegetation under this alternative were 

included in the discussion for the Preferred Alternative 

of the 2007 PEIS (USDOI BLM 2007a:4-66 to 4-67). 

Based on projected herbicide use under this alternative 

(Table 2-4), imazapic, triclopyr, tebuthiuron, clopyralid, 

and glyphosate would be used the most, together 

accounting for approximately 73 percent of the land 

area that would be treated. The risks and benefits of 

using these herbicides are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-48 to 4-66). Imazapic is used to 

manage species such as cheatgrass, hoary cress, and 

perennial pepperweed, and generally has a low to 

moderate risk to non-target vegetation. Triclopyr is an 

herbicide registered for aquatic use that is commonly 

used on woody riparian species, as well as wetland and 

aquatic invasives (e.g., Eurasian watermilfoil and purple 

loosestrife). It has a moderate to high risk to non-target 

plants. Tebuthiuron is used primarily to manage woody 

invasive plants in rangelands and ROWs. The BLM 

uses tebuthiuron to thin sagebrush and create more 

favorable habitat for sagebrush-dependent species such 

as sage-grouse. It has a moderate to high risk to nontarget plants. Clopyralid is also used to control 

broadleaf weeds, and is used in forest and rangeland 

areas for the management of species such as diffuse and 

spotted knapweed, yellow starthistle, and bull, Canada, 

Scotch, and musk thistle. It generally has a low to 

moderate risk to non-target plants. Glyphosate is 

commonly used in areas where bare ground is desired, 

and in aquatic and riparian habitats to manage invasive

plants such as purple loosestrife, giant reed, and water 

lilies. It generally has a low to moderate risk to nontarget plants.

The goals, effectiveness, and extent of herbicide 

treatments would be much the same as at present. 

Herbicide treatments would be used in conjunction with 

other treatment methods to manage invasive plant 

species, with varying degrees of effectiveness at 

establishing and maintaining native and desirable plant 

communities. Additionally, repeated use of the same 

herbicides could allow target invasive plants to develop 

herbicide resistance over time. With multiple treatments 

over the long term, successful control of fire-adapted

invasive species such as cheatgrass would help reduce 

fire risk, and maintenance and restoration of native plant 

communities would help maintain and restore historic 

fire regimes.

Monitoring of treatment sites would continue to be 

conducted to determine the effectiveness of treatments 

and the need for retreatment. Site revisits would be 

made to compare the targeted population size against 

pre-treatment data, to compare pre-treatment and posttreatment data, and to assess the establishment and 

recovery of desirable vegetation. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, herbicide treatment projects

would be much the same as those under the No Action 

Alternative, except that aminopyralid, fluroxypyr, and 

rimsulfuron would be available for use in addition to all 

of the currently approved herbicides.

Based on projected herbicide use under this alternative 

(Table 2-4), rimsulfuron, triclopyr, tebuthiuron, 

clopyralid, aminopyralid, and imazapic would be used 

the most, together accounting for approximately 81 

percent of the land area that would be treated. The new 

active ingredients would account for an estimated 27 

percent of all acres treated, with rimsulfuron and 

aminopyralid accounting for approximately 26 percent 

of all acres treated. Compared to the No Action 

Alternative, use of imazapic, glyphosate, and picloram 

would decrease substantially with the introduction of 

these chemicals. Use of fluroxypyr would be minimal 

under this and the other action alternatives.

While the three new herbicides are generally low risk, 

they would still impact non-target plants under direct 

spray and spill scenarios, much like the herbicides that 

would be used most extensively under the No Action 

Alternative. Therefore, there would not be a substantial

difference between the No Action Alternative and the 

BLM Vegetation Treatments Three New Herbicides 4-36 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Preferred Alternative in terms of risk to non-target 

plants. 

The introduction of the new active ingredients could 

increase the effectiveness of certain components of 

vegetation management by providing additional options 

for targeting invasive plants. Aminopyralid could be 

used to control of many of the species currently targeted 

by picloram (e.g., knapweeds, thistles, and yellow 

starthistle). This active ingredient is likely to receive an 

aquatic registration in the near future that would allow 

for incidental overspray of aquatic habitats during 

treatment of wetland and riparian vegetation. With such 

a registration, aminopyralid could be used in place of 

glyphosate for management of certain invasive plants in 

riparian areas. Because aminopyralid is more selective 

than glyphosate, it may be less likely to result in 

removal of non-target riparian vegetation.

Rimsulfuron would typically be used to manage

cheatgrass and other annual grasses, and as such could 

be used instead of imazapic in some instances. 

Rimsulfuron has been observed to be more effective 

than imazapic in certain areas.

Fluroxypyr would be used minimally, but may increase 

the effectiveness of certain herbicide treatments relative 

to the No Action Alternative by controlling target 

species that are resistant to other herbicides, improving 

control of target species when mixed with other active 

ingredients, and reducing the amount of other herbicides 

products used in treatments.

Overall, there would be no change to the goals or extent 

of herbicide treatment programs, relative to the No 

Action Alternative, although it is possible that there 

could be an improvement in the effectiveness of certain 

treatments with the availability of the new herbicides.

Improved effectiveness of treatments could allow the 

BLM to better meet its goals of managing undesirable 

vegetation, reducing fire risk, and restoring natural fire 

regimes.

Alternative C – No Aerial Application of New 

Herbicides

Under Alternative C, herbicide treatment projects would 

be much the same as those under the No Action and 

Preferred Alternatives, except that in addition to all the 

other currently approved herbicides, aminopyralid, 

fluroxypyr, and rimsulfuron would be available for use 

for ground treatments only.

Based on projected herbicide use under this alternative 

(Table 2-4), triclopyr, tebuthiuron, imazapic, clopyralid, 

and glyphosate would be used the most, together 

accounting for approximately 69 percent of the land 

area that would be treated, which is similar to the No 

Action Alternative. The new herbicides would account 

for approximately 10 percent of all acres treated, with 

rimsulfuron and aminopyralid accounting for 9 percent 

of all acres treated, or about one third of the amount 

under the Preferred Alternative.

Overall risks to non-target plants under this alternative 

would not be substantially different than under the other 

alternatives. The most commonly used herbicides would 

continue to pose a risk to non-target plants as a result of 

herbicide treatments, particularly under direct spray and 

spill scenarios.

Prohibiting aerial spraying of the three new herbicides 

would limit their usefulness. For example, given the 

abundance of cheatgrass and other invasive annual 

grasses and the extensiveness of planned treatments for 

these species, aerial spraying is one of the most costeffective treatment methods. The BLM would not have 

the option to aerially spray rimsulfuron, and would 

instead continue to utilize imazapic for these 

applications. While the BLM would still have some 

options to utilize the three new active ingredients to 

increase the effectiveness of treatments, these options 

would be limited relative to the Preferred Alternative. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative, herbicide treatment projects

would be much the same as under the other alternatives. 

Similar to the other action alternatives, new active 

ingredients would be available for use, but they would 

only include aminopyralid and fluroxypyr. Based on 

projected herbicide use under this alternative (Table 2-

4), triclopyr, tebuthiuron, clopyralid, glyphosate, and 

aminopyralid would be used the most, together 

accounting for approximately 70 percent of the land 

area that would be treated. New herbicides would 

account for approximately 11 percent of all acres 

treated, with aminopyralid accounting for 10 percent.

In general, risks to non-target plants would be similar to 

those under the other alternatives. Herbicides would 

continue to pose a risk to non-target plants, particularly 

under direct spray and spill scenarios.

BLM Vegetation Treatments Three New Herbicides 4-37 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Prohibiting the use of rimsulfuron would give the BLM 

one fewer herbicide option for its herbicide treatments, 

relative to the Preferred Alternative and Alternative C. 

The BLM would continue to utilize imazapic for 

management of cheatgrass and other annual grasses. 

However, aminopyralid would be available as an option 

for management of undesirable broadleaf plants in 

upland and riparian habitats, and use of picloram would 

decrease by approximately the same amount as under 

the Preferred Alternative. The availability of 

aminopyralid and fluroxypyr could increase the 

effectiveness of certain treatments relative to the No 

Action Alternative, but this increase would be less than 

under the Preferred Alternative.

Mitigation for Herbicide Treatment 

Impacts

In addition to the SOPs identified earlier in this section 

and in the 2007 PEIS (USDOI BLM 2007a:Table 2-8), 

the following measures are recommended to reduce 

impacts to non-target vegetation from the use of 

herbicides:

• Use Table 4-8 to establish herbicide-specific 

buffer zones around downstream water bodies, 

and associated habitats and non-target plant 

species/populations of interest for 

aminopyralid, fluroxypyr, and rimsulfuron. 

Consult the ERAs for more specific 

information on appropriate buffer distances 

under different soil, moisture, vegetation, and 

application scenarios. 

Special Status Plant Species

Introduction

As discussed in Chapter 3, public lands in the western 

U.S. support numerous plant species that have been 

given a special status based on their rarity or sensitivity. 

Special status plants include approximately 165 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 Using Aminopyralid, Fluroxypyr, and 

Rimsulfuron on Bureau of Land Management Lands in 

17 Western States Biological Assessment (USDOI BLM 

2015) provides a description of the distribution, life 

history, and current threats of 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, associated 

with the use of aminopyralid, fluroxypyr, and 

rimsulfuron by the BLM. 

Impacts Assessment Methodology

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM to assess the impacts to 

sensitive plant species from the use of herbicides 

(AECOM 2014a,b; AECOM 2015). The ERA methods 

are summarized in the Vegetation section of this 

chapter, and are presented in more detail in the 

Vegetation Treatments Programmatic EIS Ecological 

Risk Assessment Protocol (ENSR 2004) and in 

Appendix C of the 2007 PEIS. 

The acute endangered species LOC for plants is 1, 

which is the same as that for typical plant species. 

However, separate plant toxicity endpoints were 

selected to provide extra protection to special status 

plant species. Thus, ERAs for some herbicides predicted 

higher risks for special status plant species than for 

“typical” plant species under certain exposure scenarios. 

The potential risks to sensitive plant species from use of 

herbicides can be minimized by following certain SOPs. 

These SOPs were identified in the 2007 PEIS (USDOI 

BLM 2007a:Table 2-8, 4-71), and would continue to be 

implemented at the local level based on site conditions. 

These SOPs include:

• Survey for special status plant species, at a time 

they can be found and identified, 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

The 2007 PEIS provides a general discussion of 

potential impacts (adverse and beneficial) to special 

status plant species from herbicide treatments (USDOI 

BLM Vegetation Treatments Three New Herbicides 4-38 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

2007a:4-71 to 4-73). This discussion considers the 

BLM’s vegetation treatment program as a whole, and

therefore would also be applicable to herbicide 

treatments that utilize the three new chemicals.

As many special status plant species are threatened by 

the spread of non-native plants, fuels reduction and 

control of competing vegetation are important 

components of management programs for special status 

plant species. Therefore, herbicide treatments conducted 

as part of these programs would be expected to benefit 

populations of special status plant species. Additionally, 

general program goals of restoring native communities 

and minimizing fire risk would also benefit these 

species by improving habitat conditions and in some 

cases reducing the risk of extirpation as a result of fire. 

The BA provides additional information on which listed 

and proposed plant species are most at risk from 

competition with non-native plants and for extirpation 

of populations from fire.

All herbicides would have the potential to harm 

populations and individuals of special status plant 

species. At the local level, locations and risks to 

sensitive plant populations would be considered when 

designing treatment projects, and the appropriate 

precautions would be taken to avoid impacts to these 

species. In some cases, manual spot treatments of 

herbicides would be the only feasible option for 

avoiding impacts to listed species. In other cases, some 

level of short-term mortality may be acceptable for 

long-term habitat improvement and increase in 

population size.

Impacts from Use of the Three New 

Herbicides

Based on information in the ERAs, all three herbicides 

would pose risks to terrestrial special status plant 

species under direct spray and off-site drift scenarios. 

The greatest risks to terrestrial special status plants from 

off-site drift would be associated with aerial 

applications, where buffer distances of 900 to 2,000 

feet (depending on application rate and site conditions) 

would likely be required to protect populations of 

special status plant species (Table 4-8). For ground 

applications, smaller buffers of 25 to 700 feet would be 

required.

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. 

Accidental direct spray or spill of fluroxypyr or 

rimsulfuron could result in harm to aquatic special 

status plant species. In the case of aminopyralid, 

however, ERAs did not predict risks to sensitive nontarget aquatic plants under these exposure scenarios. 

Should aminopyralid receive an aquatic registration in 

the future that allows for incidental overspray into 

aquatic habitats, it is not expected that sensitive aquatic 

plants would be harmed by applications in adjacent 

upland or wetland areas. Off-site drift of fluroxypyr 

would not be expected to harm sensitive aquatic plants, 

assuming standard BLM buffers around aquatic 

habitats. However, special status aquatic plants would 

be at risk for harm from spray drift of rimsulfuron. 

Buffers of 100 to 300 feet would likely be required for 

ground applications, and buffers of 1,000 to 1,400 feet 

would likely be required for aerial applications of 

rimsulfuron.

Based on the predictions in the ERA, adverse effects to 

terrestrial special status plant species should not occur 

as a result of surface runoff of any of the three 

herbicides. Additionally, it is not expected that surface 

runoff of aminopyralid or fluroxypyr would harm 

sensitive aquatic plants in downslope habitats. 

However, surface runoff of rimsulfuron would have the 

potential to adversely affect special status aquatic 

plants, particularly in sandy soils and in areas with 

greater than 50 inches of rainfall per year.

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. No adverse effects to pollinators were 

predicted for direct spray or dermal contact with 

vegetation sprayed by aminopyralid or rimsulfuron. 

Low risks to pollinators were predicted under scenarios 

involving direct spray by fluroxypyr. 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, 

BLM Vegetation Treatments Three New Herbicides 4-39 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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 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)

Impacts to special status plant species under this 

alternative were summarized in the 2007 PEIS under the 

discussion for the Preferred Alternative (USDOI BLM 

2007a:4-74). Up to 932,000 acres of public lands would 

be treated with herbicides annually. Herbicide use 

would be associated with risks to special status plant 

species, although treatments would be designed at the 

local level to avoid or minimize risks to these species. 

Regardless of measures to avoid sensitive plant 

populations, there would be some risk of accidental 

exposure to herbicides. As identified in the 2007 PEIS, 

active ingredients with the greatest risks for adverse 

effects to special status plants would be 2,4-D, 

bromacil, diquat, diuron, hexazinone, and sulfometuron 

methyl. 

Under this alternative, populations of special status 

plant species would benefit from herbicide treatments 

that reduce fuels (such as cheatgrass) and control nonnative, invasive species that compete with native plants. 

Aminopyralid, fluroxypyr, and rimsulfuron would not 

be approved for use under this alternative, but the 

species that they target would continue to be managed

using currently approved herbicides.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred

Alternative)

Under this alternative, the total acreage of public lands 

treated with herbicides annually would be the same as 

under the No Action Alternative and the other action 

alternatives. However, aminopyralid, fluroxypyr, and 

rimsulfuron could be used as part of vegetation 

management programs throughout the 17 western states. 

Special status plant species would continue to be at risk

for harm from contact with herbicides, although 

treatments would continue to be designed to avoid or 

minimize impacts to special status plant species. 

In considering the active ingredients with the greatest 

risk to non-target plants, discussed under Alternative A, 

there would be little change in the amount of these 

ingredients used under the Preferred Alternative, and all 

except 2,4-D would continue to make up a very small 

component of the total amount of herbicide used 

annually. Under the Preferred Alternative, 2,4-D use is 

estimated at 5 percent, versus 6 percent under the No 

Action Alternative.

While the three new active ingredients would not offer 

substantially different types of target species control, 

they may be able to increase the efficacy of individual 

treatments by addressing herbicide resistance issues, 

adding to the strength of other herbicides in tank mixes, 

and performing better than currently approved 

herbicides under certain site conditions.

Alternative C – No Aerial Application of New 

Herbicides

This alternative would be similar to the other 

alternatives as far as risks and benefits to special status 

plant species. Treatment acres would be the same as 

those under the other alternatives, and the suite of 

chemicals available would be the same as under the 

Preferred Alternative, except that aminopyralid, 

fluroxypyr, and rimsulfuron would only be available for 

application using ground methods; aerial spraying of 

these chemicals would not occur. 

Since aerial spraying of herbicides would not occur in 

habitats that support listed species, and is unlikely to 

occur in many habitats that support populations of 

special status plant species, this alternative would not be 

substantially different than the Preferred Alternative as 

far as risks to sensitive plant species. 

Herbicides with the greatest risk to non-target plants 

would continue to be used in small amounts, and at 

levels similar to those under the No Action Alternative. 

BLM Vegetation Treatments Three New Herbicides 4-40 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

This alternative would be similar to the other 

alternatives as far as total acres treated and herbicides 

available for use, except that rimsulfuron would not be 

added to the list of approved active ingredients. 

Aminopyralid and fluroxypyr would be integrated into 

herbicide treatment programs, including those designed 

to improve habitats occupied by, or that could be 

occupied by, special status plant species. 

Because rimsulfuron would not be available for use, the 

relative amount of each herbicide used under this 

alternative would be very similar to the breakdown 

under the No Action Alternative. Most importantly, the 

relative use of herbicides with the greatest risks to nontarget plants also would be very similar to the use of 

these chemicals under the No Action Alternative. These 

chemicals would continue to be used in small quantities, 

and risks to non-target sensitive plant species would be 

similar to those under the other alternatives. 

Mitigation for Herbicide Treatment 

Impacts

When using the previously approved herbicides, the 

BLM would continue to follow mitigation for 

vegetation and special status plants identified in the 

2007 PEIS. The following mitigation is recommended 

to reduce the likelihood of impacts to special status 

plant species from applications of aminopyralid, 

fluroxypyr, and rimsulfuron. This mitigation should be 

implemented in addition to the SOPs designed to protect 

plants presented in Chapter 2 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 Using 

Aminopyralid, Fluroxypyr, and Rimsulfuron on 

Bureau of Land Management Lands in 17 

Western States Biological Assessment (USDOI 

BLM 2015). Apply these measures to sensitive 

plant species, as well as listed species.

Fish and Other Aquatic 

Organisms

Introduction

The proposed herbicide treatments have the potential to 

affect fish and other aquatic organisms, predominantly 

through indirect effects to aquatic habitats and adjacent 

riparian and upland areas. Noxious weeds and other 

non-native invasive species can be detrimental to 

aquatic habitats. Infestations of riparian systems and 

other habitats by non-native plants can reduce the ability 

of these systems to support fish and other aquatic 

organisms. Non-native plants can affect stream 

morphology and habitat characteristics, bank erosion, 

flow levels, and populations of native insects that 

provide a food source for fish. Removal of invasive 

species can help to restore a more complex vegetative 

and physical structure and natural levels of processes 

such as sedimentation and erosion.

Scoping Comments and Other Issues 

Evaluated in the Assessment

None of the scoping comments received were specific 

to fish or other aquatic organisms. However, comments 

concerned with the potential for the new herbicides to 

impact water resources would also apply to aquatic 

organisms and their habitats. Additionally, comments 

that support the new herbicides for their limited 

environmental risk are applicable. 

Standard Operating Procedures

The SOPs listed in the 2007 PEIS would be followed 

for treatments with aminopyralid, fluroxypyr, and 

rimsulfuron, as applicable: 

• 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. 

BLM Vegetation Treatments Three New Herbicides 4-41 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

• 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.

Additional mitigation for fish and aquatic organisms is 

presented in the ROD for the 2007 PEIS (USDOI BLM 

2007b:Table 2). Many of these mitigation measures 

would apply to treatments involving the three new 

herbicides, or tank mixes with these active ingredients. 

• Limit the use of terrestrial herbicides 

(especially diuron) in watersheds with 

characteristics suitable for potential surface 

runoff that have fish-bearing streams during 

periods when fish are in life stages most 

sensitive to the herbicide(s) used.

• To protect special status fish and other aquatic 

organisms, implement all conservation 

measures for aquatic animals presented in the 

Biological Assessment for Vegetation 

Treatments on Bureau of Land Management 

Lands in 17 Western States (USDOI BLM 

2007f). 

• Establish appropriate herbicide-specific buffer 

zones for water bodies, habitats, or fish or other 

aquatic species of interest (see the 2007 PEIS 

[USDOI BLM 2007a:Appendix C, Table C16], as well as recommendations in individual 

ERAs [AECOM 2014a,b; AECOM 2015]).

• 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 the 2007 PEIS 

[USDOI BLM 2007a:Appendix C, Table C16], as well as recommendations in individual 

ERAs [AECOM 2014a,b; AECOM 2015]).

• At the local level, consider effects to special 

status fish and other aquatic organisms when 

designing treatment programs.

Impacts Assessment Methodology

The methods used to assess impacts to fish and aquatic 

organisms from the three new herbicides were the same 

as the methods described in the 2007 PEIS (USDOI 

BLM 2007a:4-77 to 4-79). A brief overview of the risk 

assessment process is provided here. 

Risk Assessment Methodology 

Aquatic receptors (fish and aquatic invertebrates) were 

evaluated to determine the effects of herbicide exposure 

in terms of certain assessment endpoints and associated 

measures of effect. The assessment endpoint is an 

expression of the value that is to be protected. In the 

case of aquatic organisms, assessment endpoints include 

survival, growth, and reproduction. These assessment 

endpoints generally reflect direct effects on 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 1998b). For ERAs, they generally 

consisted of acute and chronic toxicity data (from 

pesticide registration documents and from the available 

scientific literature) for the most appropriate surrogate 

species.

Because the BLM uses herbicides in a variety of 

programs with several different application methods, the 

following exposure scenarios were considered to assess 

the potential ecological impacts of herbicides to fish and 

other aquatic organisms under a variety of uses and 

conditions:

• Direct spray of the receptor or water body. 

• Off-site drift of spray to terrestrial areas and 

water bodies. 

BLM Vegetation Treatments Three New Herbicides 4-42 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

• 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. 

Direct spray scenarios considered both a pond (1/4 acre, 

1 meter [3.3 feet] deep) and a stream (representative of 

Pacific Northwest low-order streams that provide 

habitat for critical life stages of anadromous salmonids). 

Accidental spill scenarios were limited to a pond, which 

represents a worst-case scenario for a spill into an 

aquatic habitat.

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.

Toxicological data for aquatic organisms were 

extrapolated from data for representative or surrogate 

species. Data describing both acute and chronic effects 

were used to generate RQs for addressing potential risks 

to aquatic receptors (see the ERAs [AECOM 2014a,b; 

AECOM 2015] or the 2007 PEIS [USDOI BLM 

2007a:4-100] for additional discussion of these 

calculations). In order to address potential risks to these 

receptors from exposure to the herbicides, RQs were 

compared to LOCs 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. For non special

status fish and aquatic invertebrates, LOCs were 0.5 for 

acute high risk, and 1 for chronic risk. Wherever the RQ 

exceeded the applicable LOCs, it was assumed that 

adverse toxicological effects to the group in question 

(fish or invertebrates) could occur. Corresponding levels 

of risk (none, low, medium, or high) were obtained by 

determining the factor by which the RQ exceeded the 

LOC, and the number of modeled scenarios in which an 

exceedance occurred. 

Adjuvants, Degradates, Inert Ingredients, and Tank 

Mixes

Adjuvants

The potential risks to aquatic organisms from adjuvants 

were raised as a concern during the 2007 PEIS process. 

Adjuvants generally function to enhance or prolong the 

activity of an active ingredient, and are not under the 

same registration guidelines as pesticides. In general, 

adjuvants comprise a relatively small portion of the 

volume of herbicide applied. Adjuvants listed for use 

with the three new herbicides include the following: 

• Aminopyralid – a nonionic surfactant. 

• Fluroxypyr – a methylated seed oil surfactant.

• Rimsulfuron – several types of spray adjuvants 

(e.g., nonionic surfactant, petroleum crop oil 

concentrate, modified seed oil, ammonium 

nitrogen fertilizer, and combination adjuvant 

products).

The BLM reviewed toxicity data for these adjuvants to 

assess risks to aquatic life. In addition, the GLEAMS 

model was used in the ERAs to estimate the potential 

portion of an adjuvant that might reach an adjacent 

water body via surface runoff. 

Degradates

It was beyond the scope of the ERAs to evaluate all of 

the possible degradates of the herbicide formulations

being considered in this PEIS. 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 lack of data on the toxicity of 

degradates of the specific herbicides represents a source 

of uncertainty in the risk assessment.

This PEIS relies on information obtained during 

preparation of the 2007 PEIS to determine the likely 

effects of degradates on aquatic organisms. The BLM 

conducted studies to evaluate information on degradates 

and try to determine if it is likely for degradates to be 

BLM Vegetation Treatments Three New Herbicides 4-43 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

more toxic than the parent compounds (active 

ingredients; see Appendix D of the 2007 PEIS).

Inert Ingredients 

The BLM reviewed confidential information on inert 

compounds used in herbicide formulations with

aminopyralid, fluroxypyr, and rimsulfuron. 

Additionally, the ERAs used the GLEAMS model to 

simulate the effects of a generalized inert compound in 

a base-case watershed (annual precipitation rate of 50 

inches per year, application area 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 (see Appendix D of the ERAs; AECOM 

2014a,b; AECOM 2015).

Tank Mixes

The ERAs for aminopyralid, fluroxypyr, and 

rimsulfuron did not include a quantitative evaluation of 

potential tank mixes for these active ingredients. 

Therefore, information on simulations of tank mixes in 

risk assessments completed for the 2007 PEIS were 

used as guidance for determining how risks to aquatic 

organisms may change when a tank mix is used, as 

compared to the active ingredient alone. Aquatic 

organisms may be at greater risk from the mixed 

application than from the active ingredient alone. 

Typical tank mixes of the three herbicides are discussed 

in Chapter 2 of this PEIS. 

Summary of Herbicide Impacts 

The general impacts to fish and other aquatic organisms 

as a result of herbicide treatments are discussed in the 

2007 PEIS (USDOI BLM 2007a:4-80). Herbicides may 

come into contact with fish and aquatic invertebrates by 

entering a water body, with potential impacts that 

include mortality, reduced productivity, abnormal 

growth, and alteration of critical habitat. Factors that 

influence an herbicide’s risk to aquatic organisms 

include size of aquatic buffers, application rate, 

application method, precipitation rate, soil type, and 

herbicide mobility and persistence. 

All 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. Potential effects from 

vegetation removal in riparian areas include loss of 

necessary habitat components (i.e., cover and food), 

increased sedimentation into aquatic habitats, altered 

nutrient dynamics, and increased water temperature due 

to a reduction in shade. The sections on Vegetation and 

Wetlands and Riparian Areas in this chapter discuss 

these risks, as well as herbicide application practices 

that can be used to reduce risk. 

Based on the likely use of the three new active 

ingredients, wide-scale removal of riparian vegetation is 

unlikely to occur. Out of the three, fluroxypyr and 

rimsulfuron would typically not be used near water, 

except possibly for spot treatments of certain target 

species. Aminopyralid would be used in riparian 

treatments for selective removal of certain species (e.g., 

knapweeds), but extensive removal of riparian 

vegetation would be unlikely. Additionally, 

aminopyralid would provide an alternative to 

glyphosate, which is less selective and more likely to 

result in removal of non-target vegetation.

The BLM’s land management goals include restoring 

and enhancing fish habitat, and restoring and 

maintaining proper functioning condition of riparian 

and wetland areas. Vegetation treatment programs in 

these areas include herbicide treatments to remove 

noxious weeds and other invasive species from these 

areas. Such treatments, as part of an overall habitat 

improvement program, would be expected to have a 

beneficial effect on fish and other aquatic organisms by 

improving stream/aquatic habitat conditions and 

restoring important riparian habitat components for 

juvenile fish growth, development, and survival, such as 

streambank structure and complexity, habitat 

complexity, and water quality (Groot and Margolis 

1991). 

Impacts of Aminopyralid

Aminopyralid is not currently registered for aquatic 

uses, although it may receive an aquatic registration in 

the near future that would address incidental overspray 

of aquatic areas during treatment of adjacent upland 

areas. Even with this registration, aminopyralid would 

not be used to manage aquatic vegetation, and would 

not be applied directly to the water column like other 

aquatic herbicides.

The ERA for aminopyralid indicates that this herbicide 

would not pose a risk to fish or aquatic invertebrates in 

ponds or streams as a result of any of the modeled 

exposure scenarios (Table 4-10). The ERA included a 

direct spray scenario and a worst-case scenario 

involving a spill of the active ingredient into the aquatic 

habitat, as well as off-site drift and surface runoff 

scenarios. 

BLM Vegetation Treatments Three New Herbicides 4-44 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-10

Risk Categories Used to Describe Herbicide Effects on Non Special Status

Fish and Aquatic Invertebrates According to Exposure Scenario 

Application Scenario Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Typ Max Typ Max

Direct Spray/Spill

Fish pond 02

[2:2]

0

[4:4]

0

[2:2]

0

[4:4]

0

[2:2]

0

[4:4]

Fish stream 0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

Aquatic invertebrates pond 0

[2:2]

0

[4:4]

0

[2:2]

0

[4:4]

0

[2:2]

0

[4:4]

Aquatic invertebrates stream 0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

Off-Site Drift

Fish pond 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Fish stream 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Aquatic invertebrates pond 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Aquatic invertebrates stream 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Surface Runoff

Fish pond 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

Fish stream 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

Aquatic invertebrates pond 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

Aquatic invertebrates stream 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84] 1Typ = Typical application rate; and Max = Maximum application rate.

2 Risk categories: 0 = No risk (majority of RQs < applicable LOC for non special status species). 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. The reader should consult the risk tables in 

Chapter 4 of the ERAs (AECOM 2014a,b; AECOM 2015) to determine the specific scenarios that result in the displayed level of risk for a given receptor 

group. 

Based on toxicity data reviewed for the ERA, 

aminopyralid exposures to fish of as high as 100 ppm 

did not result in any observable mortality or sub-lethal 

effects. Additionally, the ERA indicates that 

aminopyralid is not likely to accumulate in fish tissue. 

Toxicity data for aquatic invertebrates was similar, with 

no adverse effects observed at concentrations of nearly 

100 ppm.

Impacts of Fluroxypyr

Fluroxypyr is not registered for use in aquatic systems. 

Therefore, routes for exposure to aquatic organisms 

would be limited to accidental direct spray through a 

misapplication or an accidental spill, or through off-site 

drift or surface runoff. The SOPs and guidelines listed 

in the 2007 PEIS and discussed in Chapter 2 of this

document would minimize the risks for misapplications 

or accidental spills into aquatic habitats. Relevant SOPs 

include preparing a spill contingency plan in advance of 

treatments, mixing and loading herbicide products in an 

area where an accidental spill would not reach a water 

body, not rinsing spray tanks in or near water bodies, 

following product labels for use and storage, and having 

licensed applicators apply the herbicides.

The ERA for fluroxypyr indicates that this herbicide 

would not pose a risk to non special status fish or 

aquatic invertebrates in ponds or streams under any of 

the modeled exposure scenarios (Table 4-10). The ERA 

included a direct spray scenario and a worst-case 

scenario involving a spill of the active ingredient into 

the aquatic habitat, as well as off-site drift and surface 

runoff scenarios.

BLM Vegetation Treatments Three New Herbicides 4-45 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Based on toxicity data presented in the ERA, no effects 

to fish were observed after exposure to fluroxypyr at 

concentrations of approximately 7 milligrams per liter

(mg/L). The ERA also indicated that based on the 

literature, fluroxypyr may accumulate in fish tissue. 

Toxicity data for aquatic invertebrates indicated that no 

adverse effects were observed at concentrations of 56 

mg/L. While the ERA considered freshwater species as 

surrogates, information from the USEPA (1998a) 

indicates that the acid form of fluroxypyr is highly toxic 

to certain marine invertebrates.

Impacts of Rimsulfuron

Rimsulfuron is not registered for use in aquatic systems. 

Therefore, possible routes for exposure to aquatic 

organisms would be the same as those for fluroxypyr: 

accidental direct spray or spill, off-site drift, or surface 

runoff. The SOPs and guidelines discussed in the 

previous section for fluroxypyr would help prevent and 

control spills and other releases into aquatic habitats.

Based on the results of the ERA, none of the modeled 

exposure scenarios were associated with risks to fish or 

aquatic invertebrates in streams or ponds, even under 

the worst case accidental spill scenarios (Table 4-10).

Based on toxicity data reviewed for the ERA, exposures 

to concentrations of rimsulfuron as high as 390 mg/L 

does not result in adverse effects to fish, although the 

potential for chronic effects is not known. Additionally, 

the ERA indicates that rimsulfuron is not likely to 

accumulate in fish tissue. Lower concentrations of the 

herbicide were noted to cause adverse effects to aquatic 

invertebrates, with test organisms affected at 50 mg/L of 

rimsulfuron.

Impacts of Adjuvants, Degradates, Inert 

Ingredients, and Tank Mixes

Adjuvants

The findings of analysis of adjuvants in the ERA 

indicate that there is no risk to aquatic organisms 

associated with the adjuvant identified for aminopyralid, 

and very low risks associated with adjuvants identified 

for fluroxypyr and rimsulfuron. The methylated seed oil 

identified for fluroxypyr may be a concern under spill 

and long-term exposure scenarios, neither of which are 

likely under the proposed treatment programs. An 

inert/adjuvant compound identified for rimsulfuron 

could potentially cause behavioral and physiological 

effects at very high exposure scenarios, which are also 

unlikely.

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 the analysis of degradates in the 2007 PEIS, 

previous studies have determined that degradates are 

often not identified or named in registration documents

and their physical and chemical attributes are often 

poorly understood. The ERAs completed for 

aminopyralid, fluroxypyr, and rimsulfuron factored in 

the lack of data on the toxicity of degradates as a source 

of uncertainty in the risk assessment process. Numerous 

degradates of other herbicides have a similar or reduced 

toxicity to the parent herbicide, but some may be more 

toxic than the parent herbicide (Sinclair and Boxall 

2003).

Inert Ingredients

As a result of the BLM’s review of confidential 

information on inert compounds, it was found that all of 

the inert ingredients identified in the formulations were 

classified as approved for “food and nonfood use,” 

which means that they are approved for use in pesticide 

products applied to food. 

The ERAs determined that inert ingredients associated 

with aminopyralid, fluroxypyr, and rimsulfuron are not 

predicted to occur at levels that would cause acute 

toxicity to aquatic life. It is assumed that toxic inert

ingredients would not represent a substantial percentage 

of the herbicide, and that minimal impacts to aquatic 

habitats would result from these ingredients.

Tank Mixes

Use of tank mixes can result in changes to the toxic 

effects of herbicides in the mixture. Herbicide 

interactions can be additive, synergistic, or antagonistic, 

and the mixture may have more or less toxicity than any

of the individual products. Based on simulations of tank 

mixes in risk assessments completed for the 2007 PEIS, 

aquatic organisms may be at greater risk from 

applications of a mix of active ingredients than from use 

of a single active ingredient alone. There is some 

uncertainty in this evaluation because herbicides in tank 

mixes may not interact in an additive manner. Thus, the 

BLM Vegetation Treatments Three New Herbicides 4-46 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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 may contribute 

to the potential risk. 

To reduce the potential for adverse 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

The BLM proposes to treat riparian vegetation with the 

three new herbicides 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 

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 treatments programs in 

the 17 western states with the 18 currently approved 

active ingredients. Approximately 932,000 acres would 

be treated annually, with approximately 10,000 acres of 

aquatic and riparian habitat treated.

The potential impacts to fish and other aquatic species 

under this alternative are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-90 to 4-91). Use of herbicides 

would result in some toxicological impacts to fish, with 

long-term beneficial effects to fish through 

improvements to aquatic and riparian areas through 

removal of invasive species from these habitats. 

The greatest risks to fish and other aquatic organisms 

would be associated with the use of diquat, triclopyr, 

and certain (non-aquatic) formulations of 2,4-D and 

glyphosate. However, many of the currently approved 

herbicides would have some level of risk to aquatic 

organisms under spill and accidental direct spray 

exposure scenarios. Buffer distances specified in the 

2007 PEIS would continue to be applied to herbicide 

treatments to protect aquatic species, and SOPs for 

mixing, handling, transporting, and applying herbicides 

would continue to be implemented to minimize the 

likelihood of accidental spills and direct spray into 

aquatic habitats.

The currently approved herbicides include active 

ingredients that would continue to be used to manage

invasive aquatic plant species such as Eurasian 

watermilfoil and water-thyme, species that alter riparian 

habitats such as common reed, saltcedar, and Japanese 

knotweed, and rangeland species that increase the risk 

of fire and associated sedimentation into aquatic 

habitats, such as cheatgrass. Treatment programs to 

improve riparian and aquatic habitats would continue 

under the No Action Alternative, which would be 

expected to benefit fish and other aquatic species.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, the amount of 

herbicide treatment on BLM-administered lands would 

be the same as under the No Action Alternative, but 

treatments could include use of aminopyralid, 

fluroxypyr, and rimsulfuron. The projected acreage of 

aquatic and riparian habitat treated annually with 

herbicides would also be the same as under the No 

Action Alternative, estimated at 10,000 acres. 

As discussed previously, of the three new active 

ingredients none would be applied directly to the water 

column, although aminopyralid is likely to receive a 

registration that would allow for incidental overspray 

into aquatic habitats. None of the herbicides would be 

used to treat invasive aquatic plant species, but 

aminopyralid would be used in riparian treatments for 

selective removal of invasive riparian and wetland 

species. Fluroxypyr and rimsulfuron would most likely 

be used for spot treatments of certain target species.

Given that the three new herbicides have no risk to

aquatic species (Table 4-10), their use in the BLM’s

vegetation management programs would be unlikely to 

have an adverse effect on aquatic species, and could 

result in a benefit to these species if they were used 

instead of active ingredients with more toxicological 

risk. As shown in Table 2-4, use of glyphosate, 

imazapic, and picloram would decrease by the greatest 

amount under this alternative. Of these, picloram and 

glyphosate both have a substantially greater 

toxicological risk to aquatic organisms than the three 

new active ingredients. Therefore, it is possible that 

aquatic organisms would be exposed to lower quantities 

of more harmful chemicals under this alternative. 

BLM Vegetation Treatments Three New Herbicides 4-47 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

As far as benefits to aquatic species through habitat 

improvements, effects under this alternative would be 

much the same as under the No Action Alternative. 

Invasive aquatic species would continue to be treated 

with the same chemicals as at present. The three new 

herbicides would be used in riparian and upland areas to 

target largely the same species as under the No Action 

Alternative.

Alternative C – No Aerial Application of New 

Herbicides

Nearly all (98 percent) of the targeted aquatic and 

riparian habitats are treated using ground-based 

methods. Therefore, prohibiting aerial applications of 

the three new herbicides under this alternative would 

have a minimal effect on the BLM’s use of chemicals in 

and around these habitats, relative to the Preferred 

Alternative. Additionally, benefits to aquatic species 

from removal of invasive species in aquatic and riparian 

habitats would be similar to those under the other 

alternatives.

The projected breakdown of herbicides used would be 

slightly different than under the No Action and 

Preferred Alternatives. Use of glyphosate would 

decrease relative to the No Action Alternative, but not 

as much as under the Preferred Alternative. Use of 

picloram would be only slightly lower than under the 

No Action Alternative. Therefore, there could be a 

minor benefit to aquatic organisms through a reduction

in toxicological risks associated with the use of 

glyphosate.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under Alternative D, aminopyralid and fluroxypyr 

would be added to the list of approved active

ingredients, but rimsulfuron would not. As 

rimsulfuron’s use near aquatic habitats would be 

minimal under the other action alternatives, banning its 

use would have very little effect on treatment programs 

that affect habitats used by fish and other aquatic 

species. Similar to the other action alternatives, 

aminopyralid would be used near aquatic habitats for 

treatment of undesirable wetland and riparian plants that 

can impact fish and other aquatic organisms.

Rimsulfuron would not be used as an option for treating 

cheatgrass under this alternative, but imazapic would 

continue to be used to manage this species to reduce fire 

risk and prevent fire-related sedimentation into aquatic 

habitats. As both imazapic and rimsulfuron pose a very 

low risk to aquatic species, there would be little 

difference between Alternative D and the other action 

alternatives as far as toxicological risks. The breakdown 

of herbicide use under this alternative would be similar 

to the No Action Alternative, with only a slight decrease 

in the use of most active ingredients resulting from the 

addition of aminopyralid and fluroxypyr. The greatest 

decrease relative to the No Action Alternative would be 

in the use of metsulfuron methyl (3 percent), which has 

a low risk to aquatic species.

Mitigation for Herbicide Treatment 

Impacts

In order to protect non special status fish and aquatic 

invertebrates from potential toxicological effects 

associated with herbicide treatments, the BLM would 

continue to follow all applicable minimum buffer 

distances for aquatic habitats, as well as all SOPs for 

transport, handling, and application of herbicides. The 

mitigation measures specified in the 2007 PEIS 

(USDOI BLM 2007a:4-92) would also apply to 

treatments involving the new herbicides, including 

applications of tank mixes that include the currently 

approved herbicides.

Based on the results of ERAs, no additional buffers or 

other mitigation measures specific to aminopyralid, 

fluroxypyr, or rimsulfuron are warranted. 

Special Status Fish and Other 

Aquatic Organisms 

Introduction

As discussed in Chapter 3, BLM lands in the western 

U.S. support numerous aquatic animals that have been 

given a special status based on their rarity or sensitivity. 

Included are fish, mollusks, and aquatic arthropods that 

are federally-listed as threatened or endangered, or are 

proposed for federal listing. The Vegetation Treatments 

Using Aminopyralid, Fluroxypyr, and Rimsulfuron on 

Bureau of Land Management Lands in 17 Western 

States Programmatic Biological Assessment (USDOI 

BLM 2015) provides a description of the distribution, 

life history, and current threats of each federally listed 

aquatic species that could potentially be affected by the 

BLM’s herbicide treatment programs, as well as species 

proposed for listing. 

BLM Vegetation Treatments Three New Herbicides 4-48 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Impacts Assessment Methodology

Assessment of impacts to sensitive aquatic animal 

species followed the same general methodology that 

was developed for the 2007 PEIS (USDOI BLM 

2007a:4-92 to 4-94). This methodology entailed 

following the protocol for completing ERAs that was 

developed with input from the USFWS, NMFS, and 

USEPA (ENSR 2004). The ERA methods for assessing 

impacts to aquatic organisms in general are summarized 

earlier in this section. To complete the ERA, a more 

conservative LOC of 0.05 (compared to an LOC of 0.5

for non special status species) was used to determine 

acute risks to special status fish and aquatic 

invertebrates. A more conservative LOC of 0.5 

(compared to 1 for non special status species) was used 

to determine chronic risks.

Corresponding levels of risk (none, low, medium, or 

high) were obtained by determining the factor by which 

the RQ exceeded the LOC, and the number of modeled 

scenarios in which an exceedance occurred.

The results of the ERA analysis for two groups of 

aquatic organisms—special status fish and aquatic 

invertebrates—were used to determine the potential 

impacts to sensitive aquatic species, which are 

presented in the BA (USDOI BLM 2015). The analysis 

presented here incorporates the findings of the BA, and 

presents a comparison of the alternatives. 

Summary of Herbicide Effects to 

Special Status Fish and Aquatic 

Invertebrates

A summary of the general effects of herbicide 

treatments on sensitive fish species and populations is 

presented in the 2007 PEIS (USDOI BLM 2007a:4-93 

to 4-94). While the general toxicological risks to 

individual organisms of sensitive species would be the 

same as those predicted for non special status fish 

species, which were described earlier in this chapter, the 

associated population- and species-level effects could

be much greater for many sensitive species because of 

their limited/fragmented distribution and limited 

population size.

In general, risks to special status fish and aquatic 

invertebrates from herbicide treatments would be 

minimized by following applicable SOPs, which 

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 

in the life stage most sensitive to the herbicide 

used.

Because the invasion and spread of non-native plant 

species in aquatic and riparian habitats affects certain 

populations of special status fish and aquatic 

invertebrates, herbicide treatments to control these 

species would benefit sensitive aquatic organisms by 

improving water quality and flow, and increasing 

dissolved oxygen. However, for most of the sensitive 

fish and other aquatic species analyzed in the BA, the 

primary threats to the species are changes in water 

levels and quality associated with development, upslope 

land use practices, groundwater pumping, and the 

expansion of non-native fish populations. For these 

species, the potential for water quality impacts 

associated with herbicide use may outweigh habitat 

improvements resulting from minimized invasive plant

infestations.

The typical risk levels for special status aquatic animals 

associated with applications of the three new herbicides 

are presented in Table 4-11. As shown in the table, the 

risk level for all of the active ingredients are shown as 0, 

or “no risk,” which means that the majority of risk 

quotients are less than the LOC used for special status 

species. In the case of aminopyralid and rimsulfuron, no 

risks to sensitive fish and aquatic invertebrates were 

predicted under any of the modeled scenarios. In the 

case of fluroxypyr, there would be no risks associated 

with accidental direct spray of the active ingredient, but 

there would be a low risk to special status fish 

associated with a truck or helicopter spill of the active 

ingredient. Special status aquatic invertebrates could be 

at risk from a helicopter spill of fluroxypyr.

BLM Vegetation Treatments Three New Herbicides 4-49 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

TABLE 4-11

Risk Categories Used to Describe Herbicide Effects on Special Status

Fish and Aquatic Invertebrates According to Exposure Scenario

Application Scenario Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Typ Max Typ Max

Direct Spray/Spill

Fish pond 02

[2:2]

0

[4:4]

0

[2:2]

0

[2:4]

0

[2:2]

0

[4:4]

Fish stream 0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

Aquatic invertebrates pond 0

[2:2]

0

[4:4]

0

[2:2]

0

[3:4]

0

[2:2]

0

[4:4]

Aquatic invertebrates stream 0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

0

[2:2]

Off-Site Drift

Fish pond 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Fish stream 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Aquatic invertebrates pond 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Aquatic invertebrates stream 0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

0

[36:36]

Surface Runoff

Fish pond 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

Fish stream 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

Aquatic invertebrates pond 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

Aquatic invertebrates stream 0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84]

0

[84:84] 1Typ = Typical application rate; and Max = Maximum application rate. 2 Risk categories: 0 = No risk (majority of RQs < most conservative LOC for special status species). 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. For some “no risk” exposure groups, RQs for 

one or more scenarios exceeded the applicable LOC. The reader should consult the risk tables in Chapter 4 of the ERAs (AECOM 2014a,b; AECOM 

2015) to determine the specific scenarios that result in the displayed level of risk for a given receptor group. 

The BLM’s SOPs would minimize the risks of spills 

into aquatic habitats. Relevant SOPs include preparing a 

spill contingency plan in advance of treatments, mixing 

and loading herbicide products in an area where an 

accidental spill would not reach a water body, not 

rinsing spray tanks in or near water bodies, following 

product labels for use and storage, and requiring 

licensed applicators to apply the herbicides. Project 

design criteria also require the BLM to consider 

sensitive species that occur near potential treatment 

areas when developing site-specific vegetation 

treatment programs. 

Impacts by Alternative

For the most part, the comparison of alternatives for 

special status fish and aquatic invertebrates is similar to 

that for all aquatic animals, which was presented earlier 

in this section. While risk levels associated with 

fluroxypyr are slightly higher for special status species 

than for non special status species, fluroxypyr 

treatments would make up only 1 percent or less of total 

herbicide use (across all habitat types; see Table 2-4)

under all alternatives.

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under this alternative, the BLM would continue its 

vegetation treatment programs at current levels and with 

currently approved herbicides, with approximately 

10,000 acres of aquatic and riparian habitats targeted for 

herbicide treatments annually. Programs would likely 

continue to include habitat restoration components that 

BLM Vegetation Treatments Three New Herbicides 4-50 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

are specifically designed to improve habitat for sensitive 

species. Use of herbicides may be included in these 

programs.

Under this alternative, there would be some risk to 

sensitive aquatic species from use of herbicides, 

particularly the more toxic formulations, such as 

glyphosate.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, the goals of vegetation treatment 

programs would be the same as under the No Action 

Alternative, including treatments that target restoration 

and improvement of special status aquatic species 

habitats. The total acreage of aquatic and riparian 

habitat treated annually would also be the same as under 

the No Action Alternative.

The 2007 PEIS indicates that the currently approved 

active ingredients with the greatest likelihood of 

impacting special status aquatic animals are diuron, 

picloram, and the more toxic formulation of glyphosate. 

With the addition of aminopyralid, fluroxypyr, and 

rimsulfuron under this alternative, use of glyphosate and 

picloram would decrease. Use of diuron would also 

decrease, but to a lesser degree (Table 2-4). Together, 

use of these three active ingredients would decrease by 

12 to 13 percent. Therefore, overall risks to aquatic 

special status species would potentially be lower than 

under the No Action Alternative.

Alternative C – No Aerial Application of New 

Herbicides

Since few aerial applications target aquatic and riparian 

areas, this alternative is likely to be similar to 

Alternative B as far as benefits to aquatic habitats and 

risks to sensitive aquatic species. The three herbicides 

of concern (glyphosate, picloram, and diuron) would 

decrease by 5 to 6 percent. Therefore, there could be 

some reduced toxicological risk to special status aquatic 

species relative to the No Action Alternative, but 

potentially less than under the Preferred Alternative.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Since rimsulfuron is not used extensively near aquatic 

habitats, prohibition of its use under this alternative 

would have little effect as far as impacts to special 

status aquatic species. Decrease in the use of 

glyphosate, picloram, and diuron would be 5 to 6 

percent under this alternative. Therefore the potential 

for reduced risk to special status aquatic species would 

be similar to that under Alternative C, and potentially 

less than under the Preferred Alternative.

Mitigation for Herbicide Treatment 

Impacts

Mitigation to reduce the likelihood of impacts to special 

status fish and other aquatic species, as included in the 

ROD for the 2007 PEIS, would continue to be 

implemented, as would all SOPs and mitigation 

presented earlier in this section. These measures would 

be applied to the three new herbicides, as relevant. The 

Biological Assessment for Vegetation Treatments Using 

Aminopyralid, Fluroxypyr, and Rimsulfuron on Bureau 

of Land Management Lands in 17 Western States 

determined that given the low toxicity of the three new 

herbicides to aquatic special status species, likely uses 

of the herbicides, and SOPs for minimizing the risks for 

spills into aquatic habitats, no new conservation 

measures were necessary for herbicide treatments using 

aminopyralid, fluroxypyr, or rimsulfuron (USDOI BLM 

2015). However, in order to ensure that the BLM 

references the most recent BA, the following mitigation 

measure has been developed: 

• To protect special status fish and other aquatic 

organisms, implement all conservation 

measures for aquatic animals presented in the 

Vegetation Treatments Using Aminopyralid, 

Fluroxypyr, and Rimsulfuron on Bureau of 

Land Management Lands in 17 Western States 

Biological Assessment (USDOI BLM 2015).

Wildlife Resources

Introduction

Public lands sustain an abundance and diversity of 

wildlife resources. Over 3,000 species of wildlife occur 

on public lands, and are dispersed over ecologically 

diverse and essential wildlife habitats. Public lands are 

vital to big game, upland game, waterfowl, shorebirds, 

songbirds, raptors, and hundreds of species of non-game 

mammals, reptiles, and amphibians (USDOI BLM

2012a).

The BLM manages vegetation to improve wildlife 

habitat—areas where basic needs such as food, shelter,

BLM Vegetation Treatments Three New Herbicides 4-51 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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. Areas that have been impacted by invasive 

plants may support fewer native wildlife species than

areas with intact native plant communities (Germano et. 

al. 2001). The important characteristics of wildlife 

habitat in the eight ecoregions that comprise the 

treatment area are presented in the 2007 PEIS (USDOI 

BLM 2007a:3-36 to 3-43). Invasive plants can change 

habitat conditions by altering the structure of plant 

communities, creating conditions that are unfavorable 

for native wildlife species. For example, in an area 

dominated by cheatgrass, fires are high in frequency and 

have fewer unburned patches than in native

communities, and can result in the loss of plant species 

that provide value for habitat, such as certain types of 

sagebrush (Miller et al. 2011). Areas dominated by 

invasive plants may also become less suitable for 

animal species that have co-evolved with native plant 

community types (Olson 1999b). 

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 using the three new active 

ingredients, followed by an assessment of impacts to 

wildlife under each alternative.

Scoping Comments and Other Issues 

Evaluated in the Assessment

Most scoping comments pertaining to wildlife resources 

addressed the benefits to wildlife from using one or 

more of the three new active ingredients. Respondents 

stated that these herbicides have lower toxicity to 

wildlife than some of the herbicides currently being 

used. They also noted that these herbicides could be 

used to control noxious weeds and invasive species that 

alter habitats used by threatened and endangered 

wildlife species. In particular, one comment addressed 

the use of rimsulfuron to control cheatgrass in order to 

maintain viable habitat for sage-grouse and other shrubsteppe species. 

The BLM also received a scoping comment requesting 

that the PEIS address potential sub-lethal effects to 

wildlife from the herbicides, reduced breeding/survival 

of sensitive species, secondary cumulative effects, and 

other unintended effects.

Standard Operating Procedures

The 2007 PEIS identified SOPs that minimize risks to 

wildlife from herbicide applications on public lands. 

These general procedures are designed to reduce the 

risk of unintended impacts to wildlife, and were taken 

into consideration when evaluating risks to wildlife 

from use of aminopyralid, fluroxypyr, and rimsulfuron:

• 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.

The 2007 PEIS also included several SOPs that have 

been developed to protect pollinators during herbicide 

treatments:

• Complete vegetation treatments seasonally 

before pollinator foraging plants bloom.

• Time vegetation treatments to take place when 

foraging pollinators are least active both 

seasonally and daily.

• Design vegetation treatment projects so that 

nectar and pollen sources for important 

pollinators and resources are treated in patches 

rather than in one single treatment.

• Minimize herbicide application rates. Use 

typical rather than maximum application rates 

where there are important pollinator resources.

• Maintain herbicide free buffer zones around 

patches of important pollinator nectar and 

pollen sources.

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• Maintain herbicide free buffer zones around 

patches of important pollinator nesting habitat 

and hibernacula.

• Make special note of pollinators that have 

single host plant species, and minimize 

herbicide spraying on those plants (if invasive 

species) and their habitats.

A complete list of SOPs can be found in the 2007 PEIS 

(USDOI BLM 2007a:Table 2-8). Additional mitigation 

that was developed for wildlife resources and 

incorporated into the ROD for the 2007 PEIS is specific 

to the currently approved herbicides, and therefore is 

not repeated here. These measures would be applicable, 

however, for tank mixes or formulations that combine 

currently approved active ingredients with the new 

active ingredients.

Since the release of the 2007 PEIS, the White House 

released the National Strategy to Promote the Health of 

Honey Bees and Other Pollinators (White House 

Pollinator Health Task Force 2015). In this strategy, the 

BLM was tasked with taking steps to conserve and 

manage pollinators and pollinator habitat on public 

lands. Therefore, in addition to the pollinator SOPs 

listed in the 2007 PEIS, the BLM would follow 

appropriate BMPs for federal lands, as described 

at http://www.fs.fed.us/wildflowers/pollinators/BMPs/d

ocuments/PollinatorFriendlyBMPsFederalLandsDRAF

T05152015.pdf). These include BMPs for pesticide use, 

which are similar to the pollinator SOPS listed above, as 

well as BMPs for improving pollinator habitat by 

removing invasive species, among others. During 

NEPA analysis for site-specific herbicide treatment 

projects, if impacts to pollinators are expected, the BLM 

would describe site-specific prescriptions to prevent 

those impacts.

Impacts Assessment Methodology

The methods used to assess impacts to wildlife from the 

three new herbicides were the same as the methods

described in the 2007 PEIS (USDOI BLM 2007a:4-99 

to 4-100). A brief overview of the risk assessment 

process is provided here, with a more detailed 

methodology presented in the risk assessments 

(AECOM 2014a,b; AECOM 2015). 

Risk Assessment Methodology

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 assessment endpoint is an expression of the value 

that is to be protected. In the case of wildlife, 

assessment endpoints include mortality, growth, 

reproduction, and other ecologically-important sublethal 

processes. These assessment endpoints generally reflect

direct effects on organisms, but indirect effects were 

also considered. Measures of effect are measurable 

changes in an attribute of an assessment endpoint (or its 

surrogate) in response to a stressor to which it is 

exposed (USEPA 1998b). For the ERAs, they generally 

consisted of acute and chronic toxicity data (from 

pesticide registration documents and from the available 

scientific literature) for the most appropriate surrogate 

species. 

Because the BLM uses herbicides in a variety of 

programs with several different application methods, 

and because a range of wildlife species are found on 

public lands, the following exposure scenarios were 

considered to assess the potential ecological impacts of 

herbicides to wildlife under a variety of uses and 

conditions:

Direct spray of terrestrial wildlife:

• Small mammal – 100 percent absorption.

• Pollinating insect – 100 percent 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 percent absorption.

• Pollinating insect – 100 percent 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.

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• Large avian herbivore – acute and chronic 

exposure.

• Large mammalian carnivore – acute and 

chronic exposure.

These exposure scenarios were considered as the most 

plausible routes for acute and chronic (short- and longterm) impacts under a variety of conditions. The 

selected receptors represent the range of wildlife species 

found on public lands, as well as the different feeding 

guilds that are present (herbivore, omnivore, and 

carnivore). 

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.

Toxicological data for wildlife were extrapolated from 

data for representative or surrogate species. Data 

describing both acute and chronic effects were used to 

generate RQs for addressing potential risks to wildlife 

receptors (see the ERAs [AECOM 2014a,b; AECOM 

2015] or the 2007 PEIS [USDOI BLM 2007a:4-100] for 

additional discussion of these calculations).

In order to address potential risks to wildlife receptors 

from exposure to herbicides, 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. For non special 

status wildlife, LOCs were 0.5 for acute risk and 1 for 

chronic risk. Wherever the RQ exceeded one or more of 

these LOCs, it was assumed that adverse toxicological 

effects to the wildlife group in question could occur. 

Corresponding levels of risk (low, medium, or high) 

were obtained by determining the factor by which the 

RQ exceeded the LOC. 

Summary of Herbicide Impacts

The 2007 PEIS provides a discussion of the general 

risks to wildlife from herbicide use (USDOI BLM 

2007a:4-101 to 4-102). Possible adverse direct effects 

include death, damage to vital organs, change in body 

weight, decrease in healthy offspring, and increased 

susceptibility to predation. Possible indirect effects 

include a reduction in 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 1998c). 

Habitat modification is often the main risk to wildlife 

from herbicide use.

This effects analysis focuses on the effects of the three 

active ingredients proposed for use, in terms of 

toxicological effects to wildlife, effectiveness at 

controlling invasive species and improving habitat, and 

potential adverse effects to habitat. 

As discussed in the 2007 PEIS, species that reside in an 

area year-round and have a small home range (e.g., 

insects, small mammals, and territorial birds) would be 

more at risk for adverse effects than more mobile 

species. In addition, species feeding on animals that 

have been exposed to high levels of herbicide could 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 and burrowing mammals) may also 

be at higher risk if soils are non-porous 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 herbicide-use strategy that would 

minimize impacts to wildlife, particularly in habitats 

that support special status species. 

Depending on the type of herbicide treatment, 

pollinators could benefit from or be adversely affected 

by treatments with herbicides. Treatments that remove 

non-native species that inhibit the growth of native plant 

species utilized by pollinators or limit native forb 

diversity would be expected to benefit pollinators. In the 

federal guidance document listing pollinator-friendly 

BMPs for federal lands, removal of invasive species is 

identified as an effective way to increase pollinator 

abundance and diversity. However, pollinators that 

utilize invasive plant species as food and nectar sources 

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could be adversely affected by treatments that target 

these species, particularly if alternative habitat plants 

are not available nearby.

Based on risk assessments, aminopyralid, fluroxypyr, 

and rimsulfuron generally have very low risk to 

wildlife, and the most substantial effects would be 

associated with habitat modification.

Impacts of Aminopyralid

Aminopyralid would commonly be used on rangelands 

to manage undesirable broadleaf species. Therefore, 

wildlife most likely to be exposed to this active 

ingredient would include those that inhabit or feed on 

grasslands and grass-dominated shrublands, such as

ground-nesting birds, ground-dwelling mammals, and 

large mammals that forage in these habitats, such as 

deer, elk, and pronghorn.

The risk assessment for aminopyralid predicted that 

exposure to this active ingredient would not pose a risk 

to terrestrial wildlife (including pollinators) under any 

of the modeled exposure scenarios (Table 4-12). Risk

quotients were all below the LOC of 0.5 (acute high 

risk). Therefore, exposure of wildlife to this active 

ingredient by direct spray, contact with sprayed 

vegetation, or ingestion of plant materials or prey items 

that have been exposed to this active ingredient is not a 

concern from a toxicological perspective.

TABLE 4-12

Risk Categories Used to Describe Herbicide Effects on Non Special Status 

Wildlife According to Exposure Scenario

Application Scenario Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Typ Max Typ Max

Direct Spray of Terrestrial Wildlife

Small mammal – 100% absorption 02 0 0 0 0 0

Pollinating insect – 100% absorption 0 0 0 0 0 0

Small mammal – 1st order dermal adsorption 0 0 0 0 0 0

Indirect Contact with Foliage After Direct Spray

Small mammal – 100% absorption 0 0 0 0 0 0

Pollinating insect – 100% absorption 0 0 0 0 0 0

Small mammal – 1st order dermal absorption 0 0 0 0 0 0

Ingestion of Food Items Contaminated by Direct Spray

Small mammalian herbivore – acute exposure 0 0 0 0 0 0

Small mammalian herbivore – chronic exposure 0 0 0 0 0 0

Large mammalian herbivore – acute exposure 0 0 0 0 0 0

Large mammalian herbivore – chronic exposure 0 0 0 0 0 0

Small avian insectivore – acute exposure 0 0 0 0 0 0

Small avian insectivore – chronic exposure 0 0 0 0 0 0

Large avian herbivore – acute exposure 0 0 0 0 0 0

Large avian herbivore – chronic exposure 0 0 0 0 0 0

Large mammalian carnivore – acute exposure 0 0 0 0 0 0

Large mammalian carnivore – chronic exposure 0 0 0 0 0 0 1Typ = Typical application rate; and Max = Maximum application rate. 2Risk categories: 0 = No risk (RQ < applicable LOC for non special status species). 

The invasive species targeted by aminopyralid 

treatments, such as yellow starthistle, knapweeds, 

thistles, and tansy ragwort generally provide minimal 

value to wildlife, and are detrimental to wildlife habitat

by forming monocultures that displace native species. 

Therefore treatments that target these species should 

benefit wildlife by improving habitat. The degree of 

benefit would vary by species of wildlife. Elk, for 

example, are adversely affected by spotted knapweed 

because they prefer the native grasses that it displaces, 

while deer are less affected because they eat more 

shrubs and other browse (Utah State University 2014). 

In grass-dominated habitats, aminopyralid has been 

shown to benefit ground-nesting birds and grounddwelling mammals by controlling invasive broadleaf 

species while stimulating development of native grass 

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species (Green et al. 2011; Halstvedt et al. 2011; 

Harrington et al. 2011).

As discussed in the Vegetation section, aminopyralid 

poses a risk to non-target native forbs and other 

desirable species in treatment areas, and therefore may 

have an adverse effect on wildlife habitat. Depending on 

the type of wildlife habitat and the size of the treatment 

area, temporary loss of herbaceous vegetation could 

have a short-term effect on broadleaf vegetation used by 

wildlife for food, cover, or nesting. Many native forbs, 

for example, provide important forage for wildlife, and 

may provide seeds that have higher energy content than 

foods provided by grass species (Kansas State 

University 1991). Native forbs also provide sources of 

pollen and nectar for certain native species of 

arthropods, and may serve as larval host plants.

In general, the long-term effects of removing invasive 

species from rangelands through aminopyralid 

applications would be to benefit native plant 

communities, improving wildlife habitat for numerous 

species in target areas.

Impacts of Fluroxypyr

Fluroxypyr would be used in very small quantities in the 

BLM’s treatment programs, accounting for 1 percent or 

less of all herbicide treatment acres annually. Like 

aminopyralid, fluroxypyr would be used extensively in 

rangeland habitats, often in tank mixes, to manage 

invasive plants while maintaining grass forage species. 

Wildlife most likely to be exposed to this active 

ingredient would include inhabitants of grasslands and 

grass-dominated shrublands, including ground-nesting 

birds and ground-dwelling mammals. Large mammals 

that forage in these habitats would also have the 

potential to be impacted. Fluroxypyr would help 

manage invasive species that have developed a 

resistance to other herbicide active ingredients. Annual 

kochia and pricklypear are two of the target rangeland 

species identified by the BLM for this active ingredient. 

Both of these species provide some value for wildlife.

The risk assessment for fluroxypyr predicted that 

exposure to fluroxypyr would not pose a risk to 

terrestrial wildlife (including pollinators) under any of 

the modeled exposure scenarios (Table 4-12). Risk 

quotients were all below the LOC of 0.5 (acute high 

risk). Therefore, exposure of wildlife to this active 

ingredient by direct spray, contact with sprayed 

vegetation, or ingestion of plant materials or prey items 

that have been exposed to this active ingredient is not a 

concern from a toxicological perspective.

One identified use of fluroxypyr is to control 

pricklypear in desert habitats. Pricklypear provides 

shelter and food for a wide variety of wildlife species, 

including nesting habitat for birds, reptiles, and small 

mammals, and cover for northern bobwhite. Its fruits, 

seeds, and pads provide food for numerous species, 

including white-tailed deer and collared peccary 

(Ueckert 1997). Therefore, use of fluroxypyr to control 

pricklypear could have adverse impacts to certain 

wildlife, depending on the species and the intent of the 

treatment.

Impacts of Rimsulfuron

Rimsulfuron could potentially see widespread use on 

public lands, depending on which alternative is selected, 

primarily for management of cheatgrass, medusahead 

rye, and other invasive winter annual grasses. This 

active ingredient would be used in a variety of wildlife 

habitats currently degraded by invasive plants, including 

(but not limited to) grasslands, sagebrush-steppe, and 

woodlands. The goals of these treatments would be to 

both reduce the cover of the target species and reduce 

the risk of future wildfire. Given its widespread use, a 

wide variety of wildlife could be exposed to this active 

ingredient. 

Possible modes of wildlife exposure to rimsulfuron 

include direct spray, dermal contact with treated 

vegetation, and ingestion of plant materials or prey 

items that have been exposed to the active ingredient. 

The risk assessment for rimsulfuron predicted that none 

of these exposure scenarios would pose a risk to any 

type of terrestrial wildlife (including pollinators; Table 

4-12). Risk quotients were all below the LOC of 0.5 

(acute high risk). Therefore, use of rimsulfuron on 

public lands does not present a toxicological concern for 

wildlife Because rimsulfuron would often be used to 

target large monocultures of cheatgrass and other 

invasive species, the short-term result of applications 

would likely be loss of vegetation and associated cover 

in treatment areas, which may constitute an impact to 

key habitat components for wildlife species. These 

short-term impacts should be offset by long-term 

improvements to habitat if treatment programs 

effectively reduce cover of target plant species and 

promote the establishment of native plant species. In 

some cases, post-treatment rehabilitation may be 

required.

While wildlife habitat on public lands has been 

adversely affected by displacement of native species by 

winter annual grasses, and associated reduced

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productivity, a potentially greater impact to wildlife 

habitat is the role of invasive plants in increasing the 

frequency and size of wildfires (Johnson and Davies 

2012). Species like cheatgrass and medusahead rye 

form a dense layer of litter that decomposes slowly and 

is highly flammable (Pellant 1996, Johnson and Davies 

2012). Therefore, even in situations where these target 

species offer some value as forage to wildlife, they 

increase the amount of fine fuels, resulting in hot, 

frequent wildfires. The invasion of cheatgrass onto the 

Intermountain rangelands, for example, has resulted in 

destructive wildfires that have negatively impacted 

wildlife and grazing resources (Clements et al. 2012; 

Clements and Harmon 2013). In addition to directly 

harming wildlife and their nests and food sources, and 

displacing them from burned habitats, fires can result in 

the long-term loss of key wildlife habitat components, 

such as big sagebrush.

The BLM currently uses approved active ingredients to 

control invasive annual grasses. The addition of 

rimsulfuron would offer the BLM more herbicide 

options for targeting these invasive species. 

Additionally, as discussed previously, there is some 

evidence that rimsulfuron may be less harmful to nontarget species and promote the reestablishment of 

desirable native species. Therefore, use of rimsulfuron 

would likely provide some level of long-term benefit to 

wildlife habitat.

Impacts of Herbicide Treatments on 

Wildlife and Habitat by Ecoregion

The 2007 PEIS gives a description of impacts to 

wildlife habitat from herbicide treatment programs, by 

ecoregion (USDOI BLM 2007a:4-109 to 4-114). These 

discussions focus on treatment goals in each ecoregion, 

and how herbicide treatments to meet those goals could 

impact wildlife and their habitat found in each 

ecoregion. As the goals of herbicide treatments and the 

assumptions of future treatments identified by local 

BLM offices during preparation of the 2007 PEIS carry 

over to this PEIS, the wildlife impacts by ecoregion are 

still applicable and are not repeated here. The discussion 

in this section focuses on new information since the 

2007 PEIS, and how use of aminopyralid, fluroxypyr, 

and rimsulfuron might change the way that herbicide 

treatment programs impact wildlife and their habitat in 

each ecoregion.

Tundra and Subarctic

Herbicides have not been used on public lands in Alaska 

on Arctic tundra or in subarctic forests, and herbicide 

treatments were not proposed for these regions as part 

of the BLM’s vegetation treatment programs during 

preparation of the 2007 PEIS. However, the BLM has 

since come out with a Draft Dalton Management Area 

Integrated Invasive Plant Strategic Plan (USDOI BLM 

2009c), which addresses control of invasive plants 

along the Dalton Highway and adjacent BLMadministered lands, along trails and spur roads, and at 

other heavy use areas (e.g., gravel pits, rest stops, mine 

sites, and airstrips). The release of this document 

indicates that some herbicide treatments are likely to 

occur in Alaska over the next 10 years, primarily to stop 

the spread of invasive plants from disturbed sites. 

Based on the current information, herbicide treatments 

(including the currently approved herbicides and the 

three new herbicides) would have a minimal effect on 

wildlife and their habitat. The proposed uses of 

herbicides in these ecoregions are largely localized to 

roadsides and other areas subject to ongoing human 

disturbance, which are not prime habitat for wildlife 

(USDOI BLM 2013i). Furthermore, early control of 

new invaders will prevent the spread of these species 

into more pristine areas, thereby minimizing the risk of 

future impacts to wildlife habitat associated with 

noxious weeds and other invasive plant species. A total 

of 19 invasive plant species have been targeted for 

control in Alaska, including the nitrogen fixers white 

sweetclover, alfalfa, bird’s-foot trefoil, and bird vetch, 

which could alter ecosystem processes and wildlife 

habitat in naturally nitrogen-poor areas.

Temperate Desert

The Temperate Desert Ecoregion would continue to 

receive the vast majority of herbicide treatments (an 

estimated 71 percent), with the goal of most treatments 

to restore lands damaged by fires in the Great Basin, 

and to benefit sage-grouse and other wildlife that use 

sagebrush communities. 

Rimsulfuron, in particular, would be used extensively in 

the Temperate Desert Ecoregion, as a tool for 

controlling winter annual grasses such as cheatgrass and 

medusahead rye. Additionally, aminopyralid and 

fluroxypyr would be used, often in tank mixes with 

currently approved herbicides, to manage broadleaf 

rangeland weeds such as yellow starthistle, knapweeds, 

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and annual kochia. Treatments with these herbicides 

would benefit a wide range of wildlife through habitat 

improvements with long-term goals of restoring native 

plant communities and reducing wildfire risk. Multiple 

treatments and post-treatment reseeding/restoration of 

native species would be necessary to meet these goals. 

Wildlife that would benefit from these treatments would

include sage-grouse and shrub-dependent species. There 

are roughly 200 species of wildlife in the Great Basin 

(USDOI BLM 1999), many of which would likely 

benefit from herbicide treatments in the Temperate 

Desert Ecoregion.

Subtropical Desert

Treatments in the Subtropical Desert Ecoregion would 

continue to make up a small fraction (less than 1 

percent) of the planned herbicide treatments. Therefore 

use of all herbicides, including the three new herbicides, 

would be minimal. Herbicide treatments in this 

ecoregion would continue to focus on managing woody 

species that have invaded shortgrass and mixed-grass 

prairies of the desert Southwest, including species such 

as mesquite, creosotebush, and snakeweed. These 

treatments benefit grassland-dwelling wildlife, such as 

jackrabbits, antelopes, and quail, by removing shrubs 

that have invaded these habitats and providing more 

open conditions (Germano 1978 cited in USDOI BLM 

1991). For species that utilize shrubbier habitats, such as 

white-tailed deer, doves, and cottontail (McCormick 

1975 cited in USDOI BLM 1991), herbicide treatments 

to control invading shrubs could have a negative effect 

on habitat.

Neither aminopyralid nor rimsulfuron has activity on 

the woody species that would be targeted for 

management in the Subtropical Desert ecoregion. 

Therefore, these herbicides would have little impact on 

wildlife habitat in this ecoregion. Fluroxypyr, however, 

provides control of undesirable woody species such as 

snakeweed and pricklypear, and could be used in 

limited amounts to control these species in the 

Subtropical Desert Ecoregion. Only a very small 

amount of this active ingredient would likely be used 

annually.

Temperate Steppe

Herbicide treatments in the Temperate Steppe 

Ecoregion would represent approximately 16 percent of 

all treated acres. More than three quarters of the 

herbicide treatments in this ecoregion would focus on 

management of invasive grasses and forbs, including 

cheatgrass, 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, and would benefit wildlife that 

inhabits short- and mixed-grass prairie grasslands, such 

as lesser prairie-chicken, mountain plovers, and prairie 

dogs.

Rimsulfuron is likely to be applied in wildlife habitat in 

this ecoregion because its predominant use would be 

control of cheatgrass. Aminopyralid has activity on 

knapweeds and thistles, and would provide the BLM 

with another option for management of these noxious 

weeds that alter the structure and species composition of 

prairie grasslands. Fluroxypyr would be used only 

minimally, but would be one option for controlling leafy 

spurge. While the BLM would be able to manage all of 

these invasive species with the currently approved 

active ingredients, the availability of aminopyralid 

would allow additional herbicide options when 

designing treatment programs to benefit wildlife habitat

in the Temperate Steppe Ecoregion.

Subtropical Steppe Ecoregion

Herbicide treatments in the Subtropical Steppe 

Ecoregion would account for approximately 9 percent 

of all treatment acres. More than three-quarters of the 

treatments would occur in sagebrush and other shrub 

habitats, and 12 percent would occur in pinyon-juniper 

and other woodlands.

In sagebrush and pinyon-juniper communities, 

rimsulfuron would be available for use as another 

option for controlling infestations of cheatgrass and 

other winter annual grasses, and helping to reduce

wildfire risk. Therefore, this active ingredient could be 

used instead of currently approved herbicides (primarily 

imazapic) in certain situations. None of the new 

herbicides, however, would play a role in treatments to 

thin sagebrush, pinyon and juniper, or other woody 

species in this ecoregion. Some control of broadleaf 

weeds could be offered by aminopyralid and 

rimsulfuron. Treatments with the new herbicides to 

control invasive plant species and reduce wildfire risk 

would provide a benefit to wildlife habitat.

Mediterranean and Marine Ecoregions

Herbicide treatments in the Mediterranean and Marine 

Ecoregions would represent approximately 5 percent of 

all treated areas. More than three-quarters of the 

treatments in these ecoregions would occur in forested 

habitats, and would be focused on integrated weed 

management and forest health. The objectives of forest 

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ENVIRONMENTAL CONSEQUENCES

health treatments would be to stem the decline in older 

forest habitats primarily due to fire exclusion, to restore 

more natural fire regimes, and to reduce hazardous fuels 

and the potential for catastrophic wildfires.

In forest and woodland habitats, the three new 

herbicides would be used to manage herbaceous 

invasive plant species that occur in the understory, or in 

canopy openings or disturbed areas, such as cheatgrass, 

knapweeds, and thistles. These treatments would be 

expected to improve habitat for forest- and woodlanddwelling wildlife by removing species that offer limited 

habitat value and displace higher value native forbs and 

grasses. Control of fire-adapted annual grasses in the 

understory would also help reduce fire risk in forest and 

woodland areas.

Impacts by Alternative

The following sections detail the expected effects of 

each of the four 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 

17 western states, using the 18 active ingredients

currently approved for use. As estimated in the 2007

PEIS, approximately 7 percent of all treatment acres are 

associated with vegetation treatments that are done 

specifically to benefit wildlife and wildlife habitat. All 

treatments, however, would be likely to benefit wildlife 

habitat, as discussed in the previous section. A 

discussion of the benefits and impacts to wildlife is 

presented in the 2007 PEIS (Alternative B; USDOI 

BLM 2007a:4-115 to 4-116).

As identified in the 2007 PEIS, the currently approved 

herbicides of greatest concern to wildlife are 2,4-D, 

bromacil, diquat, and diuron, based on their relative 

level of risk to wildlife as predicted by ERAs. Based on 

the projections made in Table 2-4, treatments with these 

four active ingredients would comprise only about 10 

percent of all acres treated under this alternative 

(compared to historic usage of about 13 percent). Other 

currently approved herbicides may pose low to 

moderate risk to wildlife under certain exposure 

scenarios. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, the total acreage of wildlife 

habitat treated with herbicides would be the same as 

under the No Action Alternative and the other action 

alternatives. Therefore, the degree of benefit to wildlife 

from treatment programs would be expected to be 

similar under all alternatives. The target species would 

be the same as under the No Action Alternative, as 

would treatment goals, including goals to improve 

wildlife habitat. The ability to use aminopyralid, 

fluroxypyr, and rimsulfuron under this alternative would 

allow the BLM greater flexibility in designing treatment 

projects, which could have a minor benefit to wildlife if 

it translates to more effective treatments and better 

achievement of project goals. The new active 

ingredients would provide new tools for controlling 

invasive species that may be resistant to one or more of 

the currently approved herbicides. Additionally, 

rimsulfuron would offer another option for wide-scale 

cheatgrass treatment, which currently threatens shrubsteppe and other important wildlife habitats throughout 

much of the western U.S.

Under this alternative, use of 2,4-D, bromacil, diquat, 

and diuron, when added together, would make up 

roughly 8 percent of all acres treated. Their usage would 

be slightly lower than under the No Action Alternative. 

However, all three of the new active ingredients 

proposed for use are of lower risk to wildlife than nearly 

all of the other active ingredients currently approved for 

use. Therefore, toxicological risks to wildlife would be 

lower overall under this alternative than under the No 

Action Alternative.

Alternative C – No Aerial Application of New 

Herbicides

Under this alternative, the total acreage of wildlife 

habitat treated with herbicides would be the same as 

under the other alternatives. Therefore, it is expected 

that the degree of benefit to wildlife from vegetation 

treatments programs would be similar to that under the 

other alternatives. Since the new herbicides would not 

be applied using aerial methods, their use would be 

limited to ground-based treatments. As a result, 

currently approved active ingredients would continue to 

be used in herbicide treatments that improve wildlife 

habitat through large-scale control of invasive plants. 

BLM Vegetation Treatments Using Herbicides 4-59 January 2016

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ENVIRONMENTAL CONSEQUENCES

The degree of benefit to wildlife habitat could be 

slightly lower than under the Preferred Alternative if the 

effectiveness of treatment programs is limited by the 

inability to utilize the new herbicides under aerial 

spraying scenarios.

The BLM may need to continue to use herbicides with a 

greater toxicological risk to wildlife instead of the three 

new herbicides proposed for use. Under this alternative, 

use of 2,4-D, bromacil, diquat, and diuron, when added 

together, would make up roughly 9 percent of all acres, 

which is slightly less than under the No Action 

Alternative, and slightly greater than under the Preferred 

Alternative. Both glyphosate and picloram, which 

would have greater use under this alternative than under 

the Preferred Alternative, have a greater toxicological 

risk to wildlife than the three new herbicides. Risks to 

wildlife from exposure to herbicides would be greater 

than under the Preferred Alternative but less than under 

the No Action Alternative. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative, the total acreage of wildlife 

habitat treated with herbicides would be the same as 

under the other alternatives, and the degree of benefit to 

wildlife from treatment programs would be similar 

under all alternatives. The inability to use rimsulfuron 

under this alternative would remove one option for 

treatment of invasives such as cheatgrass and other 

annual grasses. Control of these target species to 

improve wildlife habitat would continue with currently 

approved herbicides (such as imazapic). However, the 

effectiveness of treatments in certain areas could be 

lower than under the other action alternatives, 

particularly the Preferred Alternative.

Under this alternative, the currently approved active 

ingredients with the greatest toxicological risk to 

wildlife (2,4-D, bromacil, diquat, and diuron), when 

added together, would make up roughly 8 percent of all 

acres treated, which is the same as under the Preferred 

Alternative, and slightly lower than under the No Action 

Alternative and Alternative C. Relative to the Preferred 

Alternative, use of glyphosate and imazapic would be 

higher, similar to levels under the No Action 

Alternative. Relative to rimsulfuron, imazapic is of a 

similar toxicity to wildlife, so there would be little 

difference from a toxicological risk standpoint between 

the use of these two chemicals. Glyphosate, however, 

has a greater toxicological risk to wildlife than 

rimsulfuron. Therefore, risks to wildlife associated with 

exposure to herbicides could be slightly greater under 

this alternative than under the Preferred Alternative.

Mitigation for Herbicide Treatment 

Impacts

The BLM would continue to implement the SOPs 

identified earlier in this section, as well as all other 

SOPs identified in the 2007 PEIS (USDOI BLM 

2007a:Table 2-8). These include, but are not limited to,

timing restrictions to avoid critical wildlife breeding or 

staging periods and pre-treatment surveys for sensitive 

wildlife and their habitats. The mitigation measures for 

wildlife specified in the 2007 PEIS (USDOI BLM 

2007a:4-118) would also apply to treatments involving 

the new herbicides, including applications of mixtures

of the new herbicides with currently approved 

herbicides.

Given the low toxicological risk of aminopyralid, 

fluroxypyr, and rimsulfuron to wildlife, no new 

mitigation measures have been developed specific to

these active ingredients.

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 

more than 60 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 non-native plant species. The Vegetation 

Treatments Using Aminopyralid, Fluroxypyr, and 

Rimsulfuron on Bureau of Land Management Lands in 

17 Western States Biological Assessment (USDOI BLM 

2015) provides a description of the distribution, life 

history, and current threats for each federally listed 

animal species, as well as species proposed for listing. 

The BA also discusses the risks to federally listed and 

proposed terrestrial wildlife associated with each of the 

herbicides proposed for use by the BLM under the 

different alternatives. 

BLM Vegetation Treatments Using Three New Herbicides 4-60 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Impacts Assessment Methodology

The BLM reviewed the literature and findings from 

ERAs conducted by the BLM to assess the impacts to

sensitive wildlife species from the use of herbicides 

(AECOM 2014a,b; AECOM 2015). The ERA methods 

are summarized in the Wildlife Resources section of 

this chapter, and are presented in more detail in the 

Vegetation Treatments Programmatic EIS Ecological 

Risk Assessment Protocol (ENSR 2004) and in 

Appendix C of the 2007 PEIS. To complete risk 

assessments for special status wildlife species, the 

chronic risk LOC of 1 and the acute endangered species 

LOC of 0.1 were used. 

Summary of Herbicide Effects to 

Special Status Wildlife Species

A summary of the general effects of herbicide 

treatments on special status wildlife species and 

populations is presented in the 2007 PEIS (USDOI 

BLM 2007a:4-119 to 4-120). Use of herbicides can 

affect the habitats of special status wildlife species, as 

discussed for wildlife in general. Herbicide treatments 

would be expected to benefit species that are threatened 

because of noxious weeds and other invasive plant 

species. Invasive plant species typically reduce the 

prevalence of native plant species, many of which serve 

as the preferred food (or in some cases the only food) of 

special status wildlife species. Invasive species may also 

detrimentally affect other important habitat components 

such as structure for nesting, foraging, and cover. 

Herbicide treatments that reduce the cover of non-native 

species and increase the cover of native species would 

be expected to benefit these special status wildlife 

species.

Potential adverse effects to the habitat of special status 

wildlife species from herbicide treatments include 

removal of vegetation used for cover, nesting, or food, 

including unintentional removal of larval host plants 

and nectar sources for listed butterfly species.

The three new herbicides proposed for use by the BLM 

could pose toxicological risks to special status wildlife 

as a result of exposure via various pathways (direct 

spray, contact with foliage after direct spray, and 

ingestion of food items contaminated by direct spray). 

Based on information presented in the ERAs, 

aminopyralid and rimsulfuron would not pose 

toxicological risks to any special status wildlife under 

the modeled exposure scenarios. In the case of 

applications involving fluroxypyr, there would be a low 

risk to pollinating insects as a result of direct spray 

scenarios. This is a conservative scenario that assumes 

the insect absorbs 100 percent of the herbicide, with no 

degradation or limitations to uptake.

The potential for special status wildlife and their habitat

to be exposed to herbicide treatments involving 

herbicides would be minimized by following applicable 

SOPs, which 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.

Herbicide treatments would adhere to the most recent 

guidance for special status species, including land use 

plan decisions for sage-grouse as amended by pertinent

sage-grouse EISs, and interim management direction as 

outlined in Instruction Memorandum 2012-043

(Greater Sage-Grouse Interim Management Policies 

and Procedures).

Impacts by Alternative

For the most part, the comparison of alternatives for 

special status wildlife is similar to that for all terrestrial 

wildlife, presented earlier in this chapter. While risk 

levels associated with fluroxypyr (presented in Table 

4-13) are slightly higher for special status species than

for non special status species, fluroxypyr treatments

would make up only 1 percent or less of total herbicide

use under all alternatives, and would only pose a risk to 

pollinating insects.

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under this alternative, the BLM would continue its 

treatment programs with the currently available 

herbicides, treating up to 932,000 acres annually. Some 

of the treatments would be implemented specifically to 

benefit special status species and their habitat.

BLM Vegetation Treatments Using Herbicides 4-61 January 2016

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TABLE 4-13

Risk Categories Used to Describe Herbicide Effects on Special Status 

Wildlife According to Exposure Scenario

Application Scenario Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Typ Max Typ Max

Direct Spray of Terrestrial Wildlife

Small mammal – 100% absorption 02 0 0 0 0 0

Pollinating insect – 100% absorption 0 0 L L 0 0

Small mammal – 1st order dermal adsorption 0 0 0 0 0 0

Indirect Contact with Foliage After Direct Spray

Small mammal – 100% absorption 0 0 0 0 0 0

Pollinating insect – 100% absorption 0 0 0 0 0 0

Small mammal – 1st order dermal absorption 0 0 0 0 0 0

Ingestion of Food Items Contaminated by Direct Spray

Small mammalian herbivore – acute exposure 0 0 0 0 0 0

Small mammalian herbivore – chronic exposure 0 0 0 0 0 0

Large mammalian herbivore – acute exposure 0 0 0 0 0 0

Large mammalian herbivore – chronic exposure 0 0 0 0 0 0

Small avian insectivore – acute exposure 0 0 0 0 0 0

Small avian insectivore – chronic exposure 0 0 0 0 0 0

Large avian herbivore – acute exposure 0 0 0 0 0 0

Large avian herbivore – chronic exposure 0 0 0 0 0 0

Large mammalian carnivore – acute exposure 0 0 0 0 0 0

Large mammalian carnivore – chronic exposure 0 0 0 0 0 0

1Typ = Typical application rate; and Max = Maximum application rate. 2 Risk categories: 0 = No risk (RQ < applicable LOC for special status species); and L = Low risk (RQ 1-10 times the applicable LOC for special status 

species).

Herbicides of greatest concern to special status wildlife 

from a toxicological perspective are 2,4-D, bromacil, 

diquat, diuron, glyphosate, hexazinone, and triclopyr. 

Based on their projected usage (summarized in Table 2-

4), treatments with these active ingredients would total 

approximately 38 percent of all acres treated (compared

to historic usage of about 44 percent). Out of these 

active ingredients, triclopyr, glyphosate, and 2,4-D 

would be used most widely, accounting for 33 percent 

of all acres treated. Other currently approved active 

ingredients may pose low to moderate risks to special 

status wildlife under a few exposure scenarios.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, efforts to improve habitats that 

support special status wildlife would benefit from the 

addition of aminopyralid, fluroxypyr, and rimsulfuron 

to the list of approved herbicides. These herbicides may 

improve the effectiveness of certain treatments, relative

to treatments using the currently approved herbicides. 

Therefore, the degree of benefit to special status species 

may be slightly greater than under the No Action 

Alternative in certain situations.

In certain treatment projects, herbicides of low toxicity 

to special status wildlife would be used instead of 

herbicides with a higher risk. In particular, use of 

glyphosate would decrease by more than half. 

Herbicides of greatest concern from a toxicological 

perspective would account for about 30 percent of all 

acres treated, with use of 2,4-D, glyphosate, and 

triclopyr accounting for 26 percent of all acres treated. 

Therefore risks for adverse effects to special status 

wildlife associated with exposure to herbicides could be 

slightly lower than under the No Action Alternative.

Alternative C – No Aerial Application of New 

Herbicides

Under this alternative, treatments that improve habitats 

utilized by special status wildlife species through largeBLM Vegetation Treatments Using Three New Herbicides 4-62 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

scale control of invasive plants would be accomplished 

using aerial spraying of currently approved herbicides, 

but not the new herbicides. This restriction would limit 

the benefits associated with introducing new herbicide 

options, relative to the Preferred Alternative.

Since the new herbicides would not be used in aerial 

applications, opportunities to use these active 

ingredients in place of those with a greater toxicological 

concern would be fewer than under the Preferred 

Alternative. Herbicides of greatest concern from a 

toxicological perspective would account for an 

estimated 35 percent of all acres treated, with use of 2,4-

D, glyphosate, and triclopyr accounting for about 31 

percent of all acres treated. Depending on where these 

herbicides are used, risks to special status wildlife from 

exposure to herbicides could be slightly lower than 

under the No Action Alternative but slightly higher than 

under the Preferred Alternative. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative, only two of the proposed active 

ingredients would be available for use under the BLM’s 

herbicide treatment programs. Use of new active 

ingredients would be approximately the same as under 

Alternative C, although the breakdown by herbicide 

would be different. Programs aimed at improving 

habitat for special status wildlife species would be 

implemented without the option of rimsulfuron. The 

degree of benefit to special status species could be 

lower than under the Preferred Alternative if certain 

treatments are less effective without the option of 

rimsulfuron. 

Under this alternative, based on herbicide usage 

estimates by the BLM, herbicides of greatest 

toxicological concern (2,4-D, glyphosate, and triclopyr) 

would account for approximately 36 percent of all acres 

treated, very similar to the No Action Alternative. 

Therefore, risks for adverse effects to special status 

wildlife would be similar to those under the No Action 

Alternative and slightly higher than under the other 

action alternatives.

Mitigation for Herbicide Treatment 

Impacts

Mitigation to reduce the likelihood of impacts to special 

status wildlife species, as included in the ROD for the 

2007 PEIS, would continue to be implemented under all 

alternatives, as would all SOPs and mitigation for 

general wildlife species presented earlier in this section. 

These measures would be applied to treatments with the 

three new herbicides, as relevant. 

The Biological Assessment for Vegetation Treatments 

Using Aminopyralid, Fluroxypyr, and Rimsulfuron on 

Bureau of Land Management Lands in 17 Western 

States determined that given the low toxicity of the 

three new active ingredients to most special status 

species and SOPs for minimizing risks to wildlife, no 

new conservation measures were necessary for 

herbicide treatments using aminopyralid or rimsulfuron

(USDOI BLM 2015). For terrestrial arthropods, 

however, the BA recommended a conservation measure 

specific to use of fluroxypyr. Therefore, the following 

mitigation is recommended to reduce the likelihood of 

impacts to special status terrestrial wildlife species from 

herbicide applications.

• When conducting herbicide treatments in or 

near habitats used by special status and listed 

terrestrial arthropods, design treatments to 

avoid the use of fluroxypyr, where feasible. If 

pre-treatment surveys determine the presence 

of listed terrestrial arthropods, do not use 

fluroxypyr to treat vegetation.

While no additional mitigation measures specific to the 

three new herbicides were identified in the BA, 

conservation measures were developed for species that 

have been listed or proposed for listing since 2007. 

Therefore, the following mitigation measure has been 

developed to ensure that the new conservation measures 

in the 2015 BA are incorporated:

• To protect special status wildlife species, 

implement all conservation measures for 

wildlife presented in the Vegetation Treatments 

Using Aminopyralid, Fluroxypyr, and 

Rimsulfuron on Bureau of Land Management 

Lands in 17 Western States Biological 

Assessment (USDOI BLM 2015).

Additional evaluations of situation-specific effects to 

special status wildlife will occur prior to local 

implementation of vegetation management activities 

that involve the use of aminopyralid, fluroxypyr, and 

rimsulfuron. Additional measures to protect special 

status wildlife may be developed at that time. 

BLM Vegetation Treatments Using Herbicides 4-63 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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 155 million acres of public 

lands are available to be grazed by livestock. Noxious 

weeds can affect the health of grazing lands by 

displacing native grasses and other plant species.

Additionally, certain noxious weeds are poisonous to 

livestock. Livestock that encounter noxious weeds may 

also contribute to the spread of noxious weeds on 

rangelands.

Scoping Comments and Other Issues 

Evaluated in the Assessment

Scoping comments directly pertinent to livestock and 

grazing included statements that the new herbicides are 

safe for use on grazing sites, and that aminopyralid in 

particular can be used in smaller amounts compared to

currently approved herbicides.

A few comments, however, indicated that use of 

aminopyralid may be incompatible with grazing 

because of its persistence in vegetation. Comments 

noted incidents involving use of manure from animals 

that had grazed on vegetation treated with aminopyralid, 

which resulted in damage to crops and other non-target 

vegetation.

Standard Operating Procedures

The 2007 PEIS lists SOPs for minimizing risks to 

livestock, which can be implemented at the local level 

according to site conditions. These SOPs would apply to 

use of the new active ingredients, when relevant, to 

reduce potential unintended impacts to livestock from 

herbicide treatments: 

• 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.

• 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.

The ROD for the 2007 PEIS (USDOI BLM 2007b: 

Table 2) also lists mitigation measures for livestock that 

are applicable to the currently approved herbicides. 

These measures could apply to the three new active 

ingredients if they are combined with one or more 

currently approved active ingredients in a formulation 

or tank mix. 

Mitigation measures and SOPs 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 methods used to assess impacts to livestock from 

the three new active ingredients were the same as those 

described in the 2007 PEIS (USDOI BLM 2007a:4-

125). Risk assessment results pertaining to mammalian 

receptors were used to assess impacts to livestock from 

the three new herbicides. The ERA methods are 

summarized in the Wildlife Resources section of this 

chapter, with a more detailed methodology presented in 

the ERAs. For dermal exposure scenarios, small 

mammals were used as receptors, as they are more 

likely to be affected than large animals (larger surface 

area to body weight ratio) and the results are more 

conservative. For ingestion scenarios, a large 

BLM Vegetation Treatments Using Three New Herbicides 4-64 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

mammalian herbivore (mule deer) was used as the 

receptor in the risk assessment.

Summary of Herbicide Impacts

The 2007 PEIS (USDOI BLM 2007a:4-125 to 4-126) 

provides a discussion of the general effects of herbicide 

use on livestock. This information is summarized here, 

with more detailed discussion included for the three 

active ingredients specifically covered by this PEIS. 

Possible direct effects from herbicides include death, 

damage to vital organs, change in body weight, 

decreases in healthy offspring, and increased 

susceptibility to predation. However, these effects are 

largely dependent on the quantity of the herbicide and 

the sensitivity of livestock to the herbicide used. 

Possible indirect effects include reduction in the amount 

of forage and the preferred forage type. 

Beneficial effects to livestock could include an increase 

in desirable forage and a decrease in noxious weeds and 

other invasive species that constitute undesirable forage.

Additionally, treatments that reduce the risk of future 

catastrophic wildfire through fuels reduction would also 

benefit livestock. Invasive plant species that may 

present a fire hazard in rangelands include cheatgrass, 

medusahead rye, other winter annual grasses such as 

ventenata and red brome, Russian thistle, oak, pinyon, 

and juniper. 

Over the short term, there would be minor impacts to 

livestock rearing as a result of mandatory restrictions 

associated with the use of herbicides. These include 

restrictions on slaughter (for food) of animals that have 

consumed treated vegetation, as well as various grazing 

restrictions. 

Noxious weed infestations can greatly reduce the land’s 

carrying capacity for domestic livestock, which tend to 

avoid most weeds (Olson 1999a). Cattle, in particular, 

preferentially graze native plant species over weeds, 

which often have low palatability as a result of defenses 

such as toxins, spines, and/or distasteful compounds. In 

addition, some noxious weeds are poisonous to 

livestock. Although goats and sheep are more likely to 

consume alien weeds than cattle, they also tend to select 

native or introduced forage species over weeds (Olsen 

and Wallander 1997, Olson 1999a). The success of 

invasive plant species removal would determine the 

level of benefit of the treatments over the long term. 

Livestock consume large amounts of grass, and 

therefore 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 

grass than it is on other plants (Fletcher et al. 1994;

Pfleeger et al. 1996). However, aminopyralid, 

fluroxypyr, and rimsulfuron generally have a very low 

risk to mammals, even when considering large 

herbivores and conservatively assuming that 100 

percent of the animal’s diet comes from treated 

vegetation. Therefore, the most likely effects would be 

associated with habitat modification and grazing 

restrictions. 

Impacts of Aminopyralid

Aminopyralid is a selective herbicide that is used to 

control undesirable broadleaf plants in rangelands and 

pastures. Therefore, it is likely to be used in areas 

grazed by livestock. 

The risk assessment for aminopyralid predicted that 

none of the possible scenarios of aminopyralid exposure 

(direct spray, contact with foliage after direct spray, 

ingestion of food items contaminated by direct spray) 

would pose a risk of adverse effects to livestock. As 

discussed previously, even scenarios that assume 100 

percent of the diet comes from treated vegetation 

indicated no risk to livestock. 

While aminopyralid is unlikely to adversely affect 

survival, growth, or reproduction of livestock, some 

restrictions in grazing would be necessary with the use 

of aminopyralid. Persistent herbicides are a class of 

systemic herbicides that are used to control a wide 

variety of broadleaf species. These herbicides are 

formulated to survive multiple years of exposure in a 

growing environment. The BLM would follow all label 

instructions when using herbicides. Aminopyralid is 

persistent in vegetation and does not break down in 

plants (Dow AgroSciences 2005), and therefore may be 

present in the urine or manure of livestock that have 

grazed in aminopyralid-treated rangelands. Therefore, 

after grazing aminopyralid-treated forage, livestock 

must graze for 3 days in an untreated pasture without 

desirable broadleaf plants before returning to an area 

where desirable broadleaf plants are present. There are 

no other restrictions on grazing following application of 

aminopyralid at the proposed typical or maximum 

application rate. If aminopyralid is used in a mixture 

with one or more other active ingredients, additional 

grazing restrictions may apply.

As discussed in the Vegetation section, aminopyralid 

has been observed to be successful at controlling 

unpalatable and/or poisonous rangeland weeds, such as 

BLM Vegetation Treatments Using Herbicides 4-65 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

musk thistle, yellow starthistle, knapweeds, and tansy 

ragwort. Russian knapweed and yellow starthistle, for 

instance, are known to be toxic to horses, causing 

“chewing disease” if large quantities are grazed over 

time, which can result in death if not treated (Turner et 

al. 2011). Tansy ragwort is toxic to various types of 

livestock, but particularly to cattle and horses. Ingestion 

of this noxious weed causes liver toxicity, and can result 

in death of animals that graze in fields where tansy 

ragwort is present (USDA Agricultural Research 

Service 2006).

Successful removal of these noxious weeds and 

restoration of grasses and other more palatable forage 

species would be beneficial to livestock. Aminopyralid 

is selective for broadleaf weeds, and therefore would 

not harm the native grasses that are favorable as forage 

for livestock. 

Many forbs have a higher nutritional value than grasses, 

even though forbs make up a small percentage of the 

total cattle diet (Weir et al 2004). Non-target broadleaf 

species that would be adversely affected by an 

application of aminopyralid could include some of the 

most nutritionally valuable forage plants for livestock 

production. Therefore, while use of aminopyralid in 

rangelands could reduce the cover of noxious weeds and 

other unpalatable species, it could also reduce the 

amount of high quality forage (forbs) available to 

grazing animals (Weir et al. 2004).

Impacts of Fluroxypyr

Fluroxypyr is a selective herbicide that is used to 

control undesirable broadleaf plants while maintaining 

grass forage species. Therefore, fluroxypyr is likely to 

be used in rangelands that are grazed by livestock.

According to the risk assessment, fluroxypyr does not 

have a risk of causing adverse health effects to livestock 

as a result of dermal exposure or ingestion scenarios. 

Fluroxypyr does not have any grazing restrictions for 

livestock, including lactating and non-lactating dairy 

animals. However, livestock must not eat treated forage 

for at least 2 days before slaughter for meat. If 

fluroxypyr is used in a mixture with one or more other 

herbicides, additional grazing restrictions may apply.

As discussed in the Vegetation section, fluroxypyr is 

effective at controlling pricklypear as well as other 

undesirable rangeland plants. Therefore, use of this 

herbicide could help improve the quality of rangeland 

forage, although its total annual use by the BLM would 

be low. 

At high densities, pricklypear can interfere with forage 

utilization and livestock movement and handling. 

However, the fruits of the plant, in particular, are high 

in carbohydrates and very palatable to livestock. While 

the spines on plants are generally avoided, they may be 

ingested by hungry animals. Ingestion of spines can 

cause ulceration and bacterial infection of the 

mouthparts and gastrointestinal tracts of sheep and goats 

(Ueckert 1997). Therefore, control of pricklypear could 

have either adverse or beneficial effects on livestock 

forage, depending on how much of the species is 

controlled and what other forage is present on the site.

Impacts of Rimsulfuron

Rimsulfuron is a selective herbicide that is used to 

control winter annual grasses, such as cheatgrass and 

medusahead rye. It is approved for use on rangelands, 

and therefore is likely to be used in areas grazed by 

livestock.

According to the ERA, rimsulfuron does not pose a risk 

to mammals under any of the modeled exposure 

scenarios. These include scenarios involving direct 

spray, indirect contact with foliage after direct spray, 

and ingestion of food that has been treated with the 

active ingredient.

The label for rimsulfuron products includes a grazing 

restriction for range and pasture areas. No livestock 

grazing should occur on treated sites for 1 year 

following application, to allow newly emerged grasses 

sufficient time to establish. 

Winter annual grasses reduce the quality of forage for 

livestock by displacing native grasses, and providing a 

very limited grazing season. Medusahead rye is rich in 

silica and becomes unpalatable to cattle and sheep in 

late spring (Oregon Department of Agriculture 2013). 

The seeds of cheatgrass produce stiff awns that make 

the plant unpalatable once the seed has dried. In 

Nevada, for example, the cheatgrass grazing season for 

livestock is only 4 to 5 weeks (University of Nevada 

Cooperative Extension 1998). Native perennial grasses 

stay green longer than invasive annual grasses, thus 

extending the grazing season (Griffith 2004). 

Additionally, cheatgrass increases the risk of wildland 

fire in rangelands, which would potentially affect 

livestock grazing in these areas. Nonetheless, cheatgrass 

is utilized as a forage species for livestock (Emmerich et 

al. 1993).

BLM Vegetation Treatments Using Three New Herbicides 4-66 January 2016

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ENVIRONMENTAL CONSEQUENCES

Impacts by Alternative

The potential effects to livestock under each alternative 

are discussed in the following sections. There are few 

differences among the alternatives, as the extent of 

herbicide treatment generally would be the same, with 

differences only in the relative percent of herbicides 

used. 

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

This alternative represents a continuation of current 

herbicide usage practices. The likely impacts of this 

alternative on livestock were presented in the 2007

PEIS, under the discussion for the Preferred Alternative 

(USDOI BLM 2007a:4-134; Tables 4-25 and 4-26). 

Both positive and negative effects to livestock are likely 

to continue under this alternative. Many of the currently 

approved herbicides are associated with some level of 

risk to livestock via one or more exposure pathways. 

The mitigation measures presented in the ROD for the 

2007 PEIS (USDOI BLM 2007b:Table 2) would 

continue to be implemented to prevent adverse effects 

to livestock from herbicide applications in areas grazed 

by these animals.

Herbicide treatments under the No Action Alternative 

would continue to improve rangeland across the West. 

These treatments are controlling noxious weeds and 

limiting the risk of wildland fire, both of which should 

benefit livestock that use public lands. Multiple 

treatments and post-treatment reseeding/restoration of 

native species would be necessary to improve rangeland 

over the long term.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, the same total acreage would be 

treated using herbicides as under the No Action 

Alternative, except that aminopyralid, fluroxypyr, and

rimsulfuron would be added to the list of approved 

active ingredients. Addition of the new herbicides 

would result in a shift in the relative amounts of the 

various herbicides that are used. However, only 

glyphosate, imazapic, and picloram would have a 

substantial reduction in usage under this alternative. 

Glyphosate and picloram are associated with low to 

moderate risks to livestock under various exposure 

scenarios (USDOI BLM 2007a:Table 4-26), but there is 

no risk to livestock associated with use of imazapic 

(USDOI BLM 2007a:4-129). Approximately 7 percent 

fewer acres would be treated with herbicides that have 

some level of risk to livestock. 

Availability of the new herbicides would allow the 

BLM more flexibility in designing treatment programs, 

and could result in more successful treatment of 

rangelands utilized by livestock. Additionally, the new 

herbicides could be used in rangelands where livestock 

mitigation measures from the 2007 PEIS restrict use of 

other herbicides, to more effectively control rangeland 

weeds. 

Alternative C – No Aerial Application of New 

Herbicides

Under this alternative, the three new herbicides would 

not be applied using aerial methods, and use of these 

chemicals would be lower than under the Preferred 

Alternative. Instead, other herbicides would be used for 

these large-scale treatments. As a result, approximately 

5 percent fewer acres would be treated with herbicides 

that have some level of risk to livestock, relative to the 

No Action Alternative.

The BLM would be able to use the new herbicides in 

some areas where use of currently approved herbicides 

is limited by livestock mitigation measures from the 

2007 PEIS, but not to the same degree as in 

Alternative B. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative, aminopyralid and fluroxypyr 

could be applied in rangelands via any application 

method, but rimsulfuron would not be added to the list 

of approved herbicides. Glyphosate and imazapic would 

continue to be used instead under most circumstances.

Glyphosate is of low to medium risk to livestock, but 

imazapic poses no risk to livestock through the modeled

exposure scenarios. Similar to the Preferred Alternative, 

approximately 7 percent fewer acres would be treated 

with herbicides that have some level of risk to livestock, 

relative to the No Action Alternative. While the BLM 

would not have rimsulfuron available for cheatgrass

treatment programs in rangelands, this invasive 

rangeland species would continue to be controlled using 

imazapic and other active ingredients.

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Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Mitigation for Herbicide Treatment 

Impacts

The BLM would continue to implement the SOPs 

identified earlier in this section, as well as all other 

SOPs identified in the 2007 PEIS (USDOI BLM 

2007a:Table 2-8). Additionally, the mitigation measures 

for livestock that were specified in the ROD for the 

2007 PEIS (USDOI BLM 2007b:Table 2) would 

continue to be followed, as applicable.

Given their low toxicological risks, no mitigation 

measures for livestock have been proposed specifically 

for herbicide treatments with aminopyralid, fluroxypyr, 

or rimsulfuron. 

Wild Horses and Burros

Introduction

Herbicide treatments have the potential to affect wild 

horses and burros on BLM-administered lands through 

exposure to chemicals that could harm their health, or 

through changes in vegetation that could positively or 

negatively alter the carrying capacity of HMAs. 

Adverse impacts 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 

treatments could improve the amount and quality of 

forage, potentially increasing the carrying capacity of 

the HMAs.

Scoping Comments and Other Issues 

Evaluated in the Assessment

One scoping comment expressed concern about the 

toxicity of herbicides to wild horses and burros. No 

other scoping comments pertaining specifically to wild 

horses and burros were received.

Standard Operating Procedures

The 2007 PEIS lists SOPs for minimizing risks to wild 

horses and burros, which can be implemented at the 

local level according to specific conditions. 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.

The ROD for the 2007 PEIS (USDOI BLM 2007b: 

Table 2) also lists several mitigation measures for wild 

horses and burros that are applicable to the currently 

approved herbicides. These mitigation measures would 

be followed, as applicable, when using mixtures of 

currently approved herbicides and new herbicides. 

Additionally, the ROD specified that the herbicide label 

grazing restrictions for livestock should be applied to 

herbicide treatments in areas that support populations of 

wild horses and burros.

Impacts Assessment Methodology

The methods used to assess impacts to wild horses and 

burros from aminopyralid, fluroxypyr, and rimsulfuron 

were the same as those described in the 2007 PEIS 

(USDOI BLM 2007a:4-137). Risk assessment results 

pertaining to mammalian receptors were used to assess 

impacts to wild horses and burros. The ERA methods 

are summarized in the Wildlife Resources section of 

this chapter, with a more detailed methodology 

presented in the ERAs. For dermal exposure scenarios, 

small mammals were used as receptors, as they are 

more likely to be affected than large animals (larger 

surface area to body weight ratio) and the results are 

more conservative. For ingestion scenarios, a large 

mammalian herbivore (mule deer) was used as the 

receptor in the risk assessment.

Summary of Herbicide Impacts

The 2007 PEIS (USDOI BLM 2007a:4-137 to 4-138) 

provides a general discussion of the potential effects of 

herbicide use on wild horses and burros. This 

information is summarized here, with more detailed 

discussion included for the three active ingredients 

specifically covered by this PEIS. 

Possible direct effects from herbicides include death, 

damage to vital organs, change in body weight, 

decreases in healthy offspring, and increased 

susceptibility to predation. However, these effects are 

BLM Vegetation Treatments Using Three New Herbicides 4-68 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

largely dependent on the sensitivity of exposed animals

to the herbicide used. Newborn horses and burros would 

be most susceptible to herbicides, with the March 

through June foaling season being a critical period. 

Possible indirect effects include reduction in the amount 

of forage and the preferred forage type. Additionally, 

wild horses and burros may move out of HMAs and 

onto lands that are not legally designated for wild horse 

and burro management.

Beneficial effects to wild horses and burros could 

include an increase in the treated area’s carrying 

capacity for wild horses and burros with the removal of 

non-native, unpalatable species. Additionally, 

treatments that reduce the risk of future catastrophic 

wildfire through fuels reduction would also benefit wild 

horses and burros.

The three herbicides generally have a very low risk to 

mammals. Therefore, the most likely effects would be 

associated with habitat modification. Application of 

herbicides in HMAs would follow guidance in the BLM 

Wild Horse and Burros Management Handbook and 

associated Herd Management Plans (USDOI BLM 

2010b).

Impacts of Aminopyralid

The risk assessment for aminopyralid predicted that 

none of the possible scenarios of aminopyralid exposure 

(direct spray, contact with foliage after direct spray, 

ingestion of food items contaminated by direct spray) 

would pose a risk to mammals. Therefore, aminopyralid 

does not pose a risk to wild horses and burros, even 

under the unlikely scenario that they would be directly 

sprayed during an herbicide application. The evaluated 

scenarios are very conservative because they assume 

100 percent absorption of the active ingredient, and that 

100 percent of the animal’s diet comes from treated 

vegetation.

Wild horses and burros forage on grasses and forbs, but 

will also consume some shrubs. Based on a literature 

review of studies about the diets of wild horses and 

burros, these animals have a wide variation in diet 

depending on the habitat and what species are available 

(Abella 2008). While control of undesirable broadleaf 

plants by aminopyralid may improve forage for wild 

horses and burros, it may also reduce the availability of 

desirable forb species, as well as the diversity of forage 

species available. Currently, many HMAs are 

overburdened with wild horse and burro populations 

(USDOI BLM 2010b). Depending on the target species 

of the treatment, herbicide treatments with aminopyralid 

could improve the capacity of HMAs. 

Impacts of Fluroxypyr

Based on the information in the ERA, there is no risk to 

mammals from exposure to fluroxypyr under the 

modeled dermal and ingestion exposure scenarios. 

Therefore, this herbicide is safe to apply in habitats used 

by wild horses and burros in standard BLM herbicide 

applications, even under direct spray scenarios and 

assuming that 100 percent of the animal’s diet comes 

from treated vegetation.

Fluroxypyr would be used in tank mixes to help control 

undesirable rangeland plants. Depending on the target 

species, use of this herbicide could benefit the quantity 

and quality of forage in wild horse and burro HMAs. 

Impacts of Rimsulfuron

According to the ERA for rimsulfuron, this active 

ingredient does not pose a risk to mammals under any 

of the modeled exposure scenarios. These include 

scenarios involving direct spray, indirect contact with 

foliage after direct spray, and ingestion of food that has 

been treated with the active ingredient. Therefore, this 

herbicide is safe to use in habitats where wild horses 

and burros occur and forage.

Rimsulfuron targets cheatgrass and other winter 

annuals. Wild horse and burros are known to feed on 

invasive annual grasses, although this may be based on 

availability rather than preference (Abella 2008). 

Treatments with rimsulfuron may improve forage for 

wild horses and burros over the long term by increasing 

the prevalence of more desirable perennial grasses. 

Additionally, control of fire-dependent winter annuals 

could decrease the occurrence of catastrophic fires that 

adversely affect HMAs (USDOI BLM 2010b). 

Impacts by Alternative

The following sections discuss the expected effects of 

each of the four alternatives on wild horses and burros, 

and compare the effects expected under each 

alternative. These effects may vary depending on the 

acreage treated using different application methods and 

active ingredients, as well as the size of treatment 

events. 

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ENVIRONMENTAL CONSEQUENCES

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under this alternative, the 18 currently approved active 

ingredients would continue to be available for use in 

habitats used by wild horses and burros. Potential 

impacts to wild horses and burros associated with these 

active ingredients were assessed in the 2007 PEIS 

(USDOI BLM 2007a:4-138 to 4-143; Tables 4-25 and

4-26). As discussed in that analysis, the currently 

approved active ingredients have varying levels of risk 

to wild horses and burros, from no risk to high risk, 

under certain exposure scenarios for certain herbicides. 

The mitigation measures in the ROD for the 2007 PEIS 

(USDOI BLM 2007b: Table 2) were developed to 

minimize these risks, and would continue to be followed 

under this alternative.

Herbicide treatments with the currently approved active 

ingredients, as a component of larger vegetation 

treatments, would have a long-term positive effect on 

wild horse and burro communities through 

improvements in rangeland forage.

The focus of vegetation treatments would continue to be 

removal and control of invasive vegetation, and 

improvement of native shrubland and grassland 

communities. If effective, these treatments would 

benefit wild horse and burro habitat. Wild horses favor 

native grasses, including bluebunch wheatgrass, western 

wheatgrass, Indian ricegrass, and bluegrasses, 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 preferred

plant species.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, the scope and extent of 

herbicide treatments would be similar to those under the 

No Action Alternative, but the three new active 

ingredients would be available for use as part of these 

treatments. The maximum assumed total area affected 

by herbicide treatments is the same as under the No 

Action Alternative and the other action alternatives 

(932,000 acres). 

The three new active ingredients—aminopyralid, 

fluroxypyr, and rimsulfuron—are effective at 

controlling rangeland weeds, but have a low toxicity to 

mammals. These herbicides could potentially be used to 

improve habitat in areas used by wild horses and burros, 

where mitigation measures restrict or limit applications 

with other chemicals. Based on information provided by 

the BLM about the likely use of herbicides under this 

alternative (Table 2-4), glyphosate, imazapic, and 

picloram would see a substantial reduction in usage as a 

result of the addition of the three new herbicides. Of 

these, glyphosate and picloram are associated with low 

to moderate risks to wild horses and burros under 

various exposure scenarios, while imazapic does not 

present a risk. Compared to the No Action Alternative, 

approximately 7 percent fewer acres would be treated 

with herbicides that have some level of risk to wild 

horses and burros under the Preferred Alternative.

Because a similar acreage of land would be treated with 

herbicides under all of the alternatives, there would be 

few differences as far as long-term benefits to 

rangelands that support wild horses and burros. 

However, addition of the new herbicides under this 

alternative may allow the BLM to more effectively 

control invasive species and reduce fire risk in wild 

horse and burro habitats. 

Alternative C – No Aerial Application of New 

Herbicides

This alternative is much like the Preferred Alternative as 

far as herbicide treatments in wild horse and burro 

habitats, except that aerial applications of the three new 

herbicides would be prohibited. For treatments requiring 

aerial applications, one or more of the currently 

approved herbicides would be used, similar to the No 

Action Alternative. Approximately 5 percent fewer 

acres would be treated with active ingredients that have 

some level of risk to wild horses and burros, relative to 

the No Action Alternative.

Long-term benefits to rangelands that support wild 

horses and burros would be similar to those under the 

other alternatives, as the acreage of land treated would 

be the same. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative, rimsulfuron would not be 

approved for use by the BLM, and would not be used in 

wild horse and burro habitats. Therefore, glyphosate and 

imazapic would continue to be used for most treatment 

programs (including cheatgrass treatments) that would 

incorporate rimsulfuron under Alternatives B and C. 

Glyphosate is of low to medium risk to wild horses and 

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Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

burros, but there is no predicted risk associated with use 

of imazapic. Similar to the Preferred Alternative, 

approximately 7 percent fewer acres would be treated 

with herbicides that have some level of risk to wild 

horses and burros, compared to the No Action 

Alternative. 

Long-term benefits to rangelands that support wild 

horses and burros would be similar to those under the 

other alternatives, as the acreage of land treated would 

be the same.

Mitigation for Herbicide Treatment 

Impacts

The BLM would continue to implement the SOPs 

identified earlier in this section, as well as all other 

SOPs identified in the 2007 PEIS (USDOI BLM 

2007a:Table 2-8). Additionally, the mitigation measures 

for wild horses and burros that were specified in the 

ROD for the 2007 PEIS (USDOI BLM 2007b:Table 2) 

would continue to be followed, as applicable.

Given their low toxicological risks, no mitigation 

measures for wild horses and burros have been 

proposed specifically for herbicide treatments with 

aminopyralid, fluroxypyr, or rimsulfuron. 

Paleontological and Cultural 

Resources

Invasive plants are present at paleontological and 

cultural resource sites on public lands. Invasive plants 

can impact paleontological and cultural resources by 

displacing native plants and contributing to soil erosion. 

Removal of invasive vegetation, when done in such a 

way that the resources are not adversely affected, can 

contribute to the restoration and maintenance of historic 

and ethnographic cultural landscapes (USDOI National 

Park Service 2003).

Scoping Comments and Other Issues 

Evaluated in the Assessment

The BLM received a few comments addressing the 

potential impact of herbicide treatments on 

paleontological and cultural resources from tribes and 

SHPOs. There was a concern about potential impacts to 

culturally important plants that might be treated with the 

new active ingredients. One comment stated that to 

address such impacts, consultation with Indian nations 

should occur at the local level, once site-specific 

treatments are known. Additionally, local tribes should 

be contacted for information about traditional cultural 

properties and other culturally significant areas that 

might be impacted. Finally, one comment was 

concerned with negative impacts to historic buildings, 

monuments, and cemetery stones from nearby herbicide 

use.

Standard Operating Procedures 

The 2007 PEIS documents the BLM’s processes for 

identifying and managing paleontological, cultural, and 

subsistence resources (USDOI BLM 2007a:4-147 to 4-

148). The BLM would continue to follow these 

processes and protocols for vegetation treatments 

involving aminopyralid, fluroxypyr, and rimsulfuron. 

These processes are outlined in a national Programmatic

Agreement with the Advisory Council on Historic 

Preservation and the National Conference of State 

Historic Preservation Officers, state-specific protocol 

agreements with SHPOs, resource management plans, 

and numerous BLM handbooks.

Before proceeding with vegetation treatments, the 

effects of BLM actions on cultural resources would be 

addressed through compliance with the NHPA. 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 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. The BLM initiated consultation with 

these 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 B).

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ENVIRONMENTAL CONSEQUENCES

As discussed in the 2007 PEIS, paleontological, 

cultural, and subsistence resources within treatment 

areas would be identified at the local level, and sitespecific mitigation measures would be developed during 

the implementation stage of vegetation treatments, if 

needed. Mitigation could include steps to avoid or 

protect cultural resources from treatments. In the case of 

subsistence resources, treatments may need to be 

modified or cancelled in certain areas to avoid impacts. 

Additionally, procedures to protect any cultural 

resources discovered during the course of vegetation 

treatments would be developed.

Additional SOPs that would apply to paleontological, 

cultural and subsistence resources are those pertaining 

to human health, which would apply to the safety of 

Native peoples who might visit areas targeted by 

treatments for subsistence, religious, or other traditional 

purposes. These procedures include (but are not limited 

to) posting treated areas with appropriate signs at 

common public access areas, observing restricted entry 

intervals specified by the herbicide label, and providing 

public notification in newspapers or other media when 

the potential exists for public exposure. Additionally, 

SOPs pertaining to fish, wildlife, and vegetation would 

help minimize potential impacts to subsistence

resources.

Summary of Herbicide Impacts 

The 2007 PEIS (USDOI BLM 2007a:4-148 to 4-149) 

provides a general discussion of the potential impacts of 

herbicide use on paleontological, cultural, and 

subsistence resources. This information is summarized 

in the sections that follow.

Paleontological Resources

Herbicides may have the potential to affect fossil 

materials, depending on: 1) fossil type; 2) minerals; 3) 

degree of fossilization; and 4) whether the fossil is 

exposed or buried. Herbicides may cause soil acidity to 

increase, or cause other chemical changes to fossil 

materials, such as discoloration or deterioration. More 

likely, damage to fossil materials, if present, would 

result from the use of wheeled equipment to apply 

herbicides, particularly vehicles traveling off roads, 

which could potentially crush fossil materials exposed 

on the surface. Additionally, herbicide treatments are 

more likely to affect researchers, students, or other field 

personnel conducting paleontological research than the 

paleontological resources themselves. 

Cultural Resources

Herbicide treatments could potentially affect buried 

organic cultural resources, but would be most likely to 

have an effect on aboveground structures and traditional 

cultural practices of gathering plant foods or materials 

important to local tribes or groups. 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. One study of the effects of glyphosate and 

triclopyr on stone and masonry material found that both 

active ingredients resulted in salt formation and color 

change. Additionally, glyphosate can lead to a longterm increased rate of deterioration (Oshida 2011). No 

other active ingredients were included in the study, but 

it is assumed that other herbicides could adversely affect 

certain materials as well. While chemicals may affect 

the surface of exposed artifacts, these materials can 

generally be removed without damage if treated soon 

after exposure. Additionally, herbicide treatment SOPs 

include protocols for identifying cultural resources and 

developing appropriate measures to mitigate or 

minimize adverse impacts.

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 radiocarbon or Carbon-14 (C14) dating of a site (USDOI BLM 1991).

Subsistence Resources

Non-target plants affected by herbicide treatments may 

include species that are important to Native American 

tribes or Alaska Native groups for traditional 

subsistence, religious, or other cultural practices. 

Impacts to these resources would be avoided through

local level consultation with tribes and groups to 

identify areas where plant resources of importance are 

located. The potential health risks associated with 

exposure to/consumption of plant materials with 

herbicide residues are discussed in the Herbicide 

Impacts on Native American Health section.

Treatments to control noxious weeds and other invasive 

species could benefit populations of native plant species 

used as subsistence or for other traditional practices, 

through restoration of native plant communities.

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Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Fish and wildlife used for subsistence could be 

adversely affected through temporary displacement 

from treatment sites or exposure to herbicides. The Fish 

and Aquatic Invertebrates and Wildlife Resources 

sections provide more detailed information on potential 

effects to wildlife from herbicide treatments.

Herbicide Impacts on Native American 

Health

Risk Assessment Methodology

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 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. These 

exposure methods are discussed further in the following 

sections, with additional detail provided in the 2007

PEIS (USDOI BLM 2007a:4-149 to 4-150).

Dermal Contact 

For scenarios involving dermal contact with sprayed 

vegetation, risk assessments assume the following:

• The 50th percentile surface area of the head, 

lower legs, forearms, and hands are exposed to 

the herbicide (884 square inches (in2

) for adults 

and 434 in2 for children; USEPA 2004).

• Native American receptors contact foliage for 3 

hours per day of subsistence activities (Harper 

et al. 2002).

• Herbicide is transferred from foliage to skin at 

a rate of 171 in2

/hour for adults and 56 

in2

/hour for children (USEPA 2012e).

For scenarios involving swimming in a contaminated 

pond, the exposure time was assumed to be 2.6 hours 

per day (Harris and Harper 1997), for 70 days per year. 

The exposed surface area was assumed to be 2,790 in2

for an adult swimmer and 1,023 in2 for a child swimmer 

(USEPA 2004).

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 quart/day. 

The berry ingestion scenario assumes that a Native 

American adult consumes 0.7 pound (lb)/day (Harper 

et. al. 2002) and a Native American child consumes 

0.15 lb/day (per California Environmental Protection 

Agency [CalEPA] 1996). 

The adult fish ingestion rate was assumed to be 2 

lbs/day based on a high fish diet scenario (Harper et al. 

2002). The high fish diet consists primarily of fish

supplemented by big game; aquatic amphibians, 

crustaceans, and mollusks; small mammals; and upland 

game birds. For Native American children, the ingestion 

rate was scaled by body weight to 0.4 lb/day (per 

CalEPA 1996).

Since it is assumed that a pond used for swimming is 

also a source of drinking water, incidental ingestion of 

contaminated water during swimming was not evaluated 

separately; it is included in the drinking water scenario.

The methodology for estimating potential risk to human 

health from exposure to herbicides is discussed in the 

Human Health and Safety section, under the Human 

Health Risk Assessment Methodology subsection.

Human Health Risks Associated with the Three New 

Herbicides

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. The risks to public receptors are discussed in the 

Human Health and Safety section. As shown in Table 

4-15, there are no risks to public receptors from 

exposures resulting from routine use (typical or

maximum application rate) or accidental scenarios. 

Additionally, there are no risks to Native American 

adults or children under any of the modeled exposure 

scenarios. These results indicate that aminopyralid, 

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ENVIRONMENTAL CONSEQUENCES

fluroxypyr, and rimsulfuron do not pose an 

unacceptable risk to Native American receptors, even 

under worst-case accidental exposure scenarios.

See the Vegetation, Fish and Aquatic Invertebrates, and 

Wildlife Resources sections in this chapter for more 

information on the potential risks of the three new 

herbicides to resources used by Native Americans.

Impacts by Alternative

The following is a discussion of how risk from 

herbicides would vary under each herbicide treatment 

alternative. Under all alternatives, the maximum 

acreage treated annually is assumed to be the same, with 

only the relative amount of each active ingredient used 

varying among the different alternatives. Under all 

alternatives, the BLM would use herbicide treatments 

for resource benefit, which would have beneficial 

effects on native plants and wildlife used by Native 

American tribes. Additionally, under all alternatives 

herbicide usage in Alaska would remain low, estimated 

at a maximum of 1,000 acres per year. 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, 

basket weaving, fibers, medicine, and ceremonial 

purposes, and would use minimal impact treatments 

where culturally significant species are known to occur.

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under this alternative, only the 18 previously approved 

herbicides would be available for use. Risks to 

paleontological and cultural resources, and to human 

health would be the same as those discussed under 

Alternative B of the 2007 PEIS (USDOI BLM 2007a:4-

151). 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) or 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. Native 

American adults and children residing near the 

treatment area 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).

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, aminopyralid, fluroxypyr, and 

rimsulfuron would be available for use in herbicide 

treatment programs, and as a result, there would be 

lower usage of other herbicides, particularly imazapic, 

glyphosate, and picloram. All of these herbicides have 

no to low human health risks. Of the herbicides with 

higher human health risks, use of 2,4-D would be 

slightly lower than under the No Action Alternative 

(approximately 1 percent fewer acres treated), 

indicating that risks associated with consumption of fish 

contaminated by 2,4-D would also be slightly lower. 

Other herbicides associated with human health risks 

(diquat, fluridone, and hexazinone) would continue to 

make up a very small component of the total herbicide 

usage. Generally, human health risks to Native 

Americans would be similar to those under the No 

Action Alternative. 

Alternative C – No Aerial Application of New 

Herbicides

Under this alternative, human health risks to Native 

American receptors would be similar to those under the 

Preferred Alternative and the No Action Alternative. 

The new herbicides would not be applied aerially, 

eliminating certain exposure pathways for Native 

American receptors. According to the HHRA, aerial 

application scenarios are generally associated with 

greater overall human health risks than ground-based 

methods. However, based on information for 

occupational receptors (see Table 4-14), risk levels for 

the three new herbicides are similar for aerial and 

ground applications. Additionally, restriction of aerial 

applications of the new chemicals would not reduce 

aerial spraying of herbicides, as different active 

ingredients would be used where aerial spraying is 

needed.

Under this alternative, herbicides with higher human 

health risks would be used at roughly the same levels as 

under the No Action Alternative, over approximately 1 

percent more land area than under the Preferred 

Alternative. In general human health risks to Native 

American receptors would be similar to those under the 

other alternatives.

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ENVIRONMENTAL CONSEQUENCES

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Herbicides (No Rimsulfuron)

Risks to Native American receptors from exposure to 

herbicides under Alternative D would be similar to 

those under the other alternatives. Rimsulfuron would 

not be used, and as a result the use of glyphosate and 

imazapic would be higher than under the other action 

alternatives (similar to the No Action Alternative). All 

three of these active ingredients pose no to low risk to 

Native American receptors, so there would be little 

difference, from a human health standpoint, associated 

with restricting the use of rimsulfuron. Use of 2,4-D 

under this alternative would be slightly lower than 

under the No Action Alternative and Alternative C (1 

percent fewer acres), indicating that risks associated 

with consumption of fish contaminated by 2,4-D would 

also be slightly lower. In general, human health risks to 

Native Americans would be similar to those under the 

other alternatives.

Mitigation for Herbicide Treatment 

Impacts

The BLM would continue to follow all of the SOPs for 

herbicide treatments in the 2007 PEIS that apply to 

paleontological and cultural resources (USDOI BLM 

2007a:Table 2-8). Additionally, the BLM would follow 

the mitigation measures identified in the ROD (USDOI 

BLM 2007b), which are specific to certain previously 

approved herbicides and would not apply to the new 

active ingredients (but would apply if a mixture with 

one or more of these previously approved herbicides is 

used).

Given the low toxicity of aminopyralid, fluroxypyr, and 

rimsulfuron to humans, no additional mitigation 

measures are recommended for herbicide treatments 

with these active ingredients.

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 users of public lands. The 

vegetation of an area, including the presence of native 

species and noxious weeds, affects its scenic qualities. 

Herbicide treatments also affect the visual quality of the 

landscape to varying degrees by killing target vegetation 

and creating a more open, “browned” landscape. Scenic 

impacts from herbicide 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 high-sensitivity 

visual resources.

Scoping Comments and Other Issues 

Evaluated in the Assessment

No scoping comments specific to visual resources were 

received by the BLM. However, the visual quality of the 

landscape is seen as a component of public benefit, and 

management of public lands must take into account 

visual resources. Lands located in highly visible areas 

along roads typically provide this benefit to the largest 

segment of the population.

Standard Operating Procedures

The 2007 PEIS identified 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; and 

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 

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ENVIRONMENTAL CONSEQUENCES

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. 

These SOPs are designed to minimize visual impacts 

associated with killing invasive plants and removing 

vegetation. Additional guidance is provided in BLM 

Manual Handbook H-8431-1, Visual Resource Contrast 

Rating (USDOI BLM 1986b). No additional mitigation 

for herbicide treatments was proposed in the 2007 PEIS 

or specified in the 2007 ROD.

BLM Assessment of Visual Resource 

Values

As discussed in BLM Handbook H-8410-1, Visual 

Resource Inventory (USDOI BLM 1986a), potential 

visual impacts from proposed activities must be 

assessed to determine whether the potential impacts will 

allow the management objective for the affected area to 

be met. A visual contrast rating is used, in which the 

project features are compared with the major features in 

the existing landscape, using basic design elements of 

form, line, color, and texture. This process is described 

in BLM Handbook H-8431-1, Visual Contrast Rating

(USDOI BLM 1986b). Activities or modifications in a 

landscape that repeat the basic design elements are 

thought to be in harmony with their surroundings. 

Modifications that do not harmonize are said to be in 

contrast with their surroundings. 

Visual resource assessments would be conducted at the 

project level to determine the potential impacts to visual 

resources associated with defined vegetation treatment 

projects.

Summary of Herbicide Impacts

As the overall vegetation treatment program is 

programmatic in scope, no visual contrast rating was 

conducted for the 2007 PEIS. It is expected that this sort 

of analysis would occur at the local level for sitespecific herbicide treatment programs. Instead, the 2007

PEIS gave a general overview of how herbicide 

treatments affect the visual quality of treated areas 

(USDOI BLM 2007a:4-154). As the new active 

ingredients affect vegetation in the same general way as 

some of the currently approved active ingredients, the 

general impact analysis for herbicide use in the 2007

PEIS would continue to apply even with the addition of 

aminopyralid, fluroxypyr, and rimsulfuron to the list of 

approved active ingredients.

In general, herbicide treatments have short-term adverse

effects and long-term positive effects on visual 

resources. Herbicide treatments create openings and 

patches of discolored vegetation that may contrast 

markedly from surrounding areas of green vegetation. 

However, these impacts would begin to disappear 

within one to two growing seasons in most landscapes. 

Over the long term, herbicide treatments would likely 

improve visual resources on public lands by removing 

infestations of invasive plants and rehabilitating 

degraded ecosystems. Native-dominated communities 

tend to be more visually appealing than plant 

communities that have been overtaken by noxious 

weeds or other undesired species. Additionally, control 

of species that serve as fuels for wildland fire would 

help reduce the size and intensity of future wildfires. A 

reduced risk of fire would benefit visual resources, as 

wildland fires substantially degrade the visual quality of 

natural areas.

Impacts by Alternative

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under the No Action Alternative, the BLM would 

continue to implement vegetation treatment projects 

using the herbicides currently approved under the ROD 

for the 2007 PEIS. As discussed in the 2007 PEIS, 

short-term adverse impacts to visual resources 

associated with herbicide use would continue to occur. 

The most dramatic effects would be seen in states with 

the most acres treated, such as New Mexico, Idaho, and 

Wyoming, and in project areas where large acreages are 

treated. 

Herbicide treatments in drier states, such as New 

Mexico, Nevada, and Wyoming, could have a reduced 

visual impact relative to those in more lush states 

because visual color contrast between natural and 

“browned” treated areas would be less dramatic.

Landscapes containing a large component of invasive 

species often contrast with surrounding natural 

landscapes and have a negative visual impact. For 

example, cheatgrass often turns brown during summer,

while native species usually remain green long into 

summer or fall. Over the long term, ongoing vegetation 

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ENVIRONMENTAL CONSEQUENCES

treatments under this alternative would have a positive 

impact on visual resources, as invasive plants and 

unwanted vegetation would be removed, and visually 

preferable native vegetation and ecosystems would 

become reestablished. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under this alternative, impacts to visual resources 

would be much the same as those under the No Action

Alternative. A comparable acreage of public lands 

would be impacted by vegetation treatments, and the 

geographic locations and size of treatments would be 

similar to those discussed under the No Action 

Alternative. It is possible that the availability of the 

three new active ingredients would result in some 

changes to treatments, but it is expected that these 

changes would be minor.

If vegetation treatments prove to be more effective as a 

result of being able to use aminopyralid, fluroxypyr, and 

rimsulfuron, there could be greater short-term visual 

impacts associated with removal of target vegetation. 

However, associated long-term benefits of recovery of 

native plant communities could also be greater. 

Alternative C – No Aerial Application of New 

Herbicides

While aminopyralid, fluroxypyr, and rimsulfuron would 

not be applied aerially under Alternative C, the 

currently approved active ingredients would continue to 

be available for aerial applications. Therefore, the 

overall extent of aerial treatments with herbicides 

should not differ substantially from that under 

Alternatives A and B. The total acreage of public lands 

affected by herbicide treatments would be the same as 

under the other alternatives, and the geographic 

locations and size of treatments would be similar to 

those discussed under the other alternatives. Short-term 

impacts and long-term beneficial effects to visual 

resources would be similar to those under the other 

alternatives. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

While rimsulfuron would not be available for use under 

this alternative, the 18 currently approved active 

ingredients would be available for use, in addition to 

aminopyralid and fluroxypyr. The maximum total 

acreage of public lands affected by herbicide treatments 

would be the same as under the other alternatives, and 

the geographic locations and size of treatments would 

be similar. Therefore, short-term impacts and long-term 

beneficial effects to visual resources would be similar to 

those under the other alternatives

Mitigation for Herbicide Treatment 

Impacts

The BLM’s SOPs for minimizing impacts to visual 

resources, listed earlier in this section, would continue 

to be implemented when conducting vegetation 

treatments. These SOPs would help reduce short-term 

impacts associated with all herbicides, including 

aminopyralid, fluroxypyr, and rimsulfuron.

No mitigation measures are proposed for visual 

resources.

Wilderness and Other Special 

Areas

Because of their special status, wilderness and other 

special areas have strict guidelines for vegetation 

treatments. These guidelines prohibit activities that 

degrade the quality, character, and integrity of these 

protected lands. Manipulation of vegetation through use 

of herbicides and other methods is generally not 

permitted, although there are exceptions in the case of

emergencies (e.g., wildfire threatening non-federal 

lands), actions taken to recover a federally listed 

threatened or endangered species, control of non-native 

species, and restoration actions where natural processes 

alone cannot recover the area from past human 

intervention (USDOI BLM 2012e). 

In WSAs, natural processes are relied on to maintain 

native vegetation and natural disturbance regimes. 

However, vegetation treatments, including herbicide 

applications, are allowed if they meet the nonimpairment standard (i.e., temporary and not creating 

surface disturbance), or if they are conducted in 

emergency circumstances, to protect or enhance 

wilderness characteristics, are grandfathered uses or 

valid existing rights, or are done to recover a federally 

listed or candidate species (USDOI BLM 2012f).

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.

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Herbicides may be applied in wilderness and other 

special areas under circumstances described in local 

Resource Management Plans or relevant NEPA 

documents. Herbicide treatments could affect these

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

None of the scoping comments received by the BLM 

were specific to wilderness or other special areas.

Standard Operating Procedures

The 2007 PEIS identified several SOPs to reduce the 

risk of spreading noxious weeds, prevent the 

establishment of new invaders, and promote public 

awareness to be followed in wilderness areas and other 

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 

invasive plants.

• 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 invasive 

plants that are spreading within the wilderness 

or threaten lands outside the wilderness.

• Give preference to 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. 

• Address wilderness and other special areas in 

management plans.

• Maintain adequate buffers for Wild and Scenic 

Rivers (1⁄4 mile on either side of river, 1⁄2 mile in 

Alaska).

These SOPs would continue to apply to herbicide 

treatments involving the three new herbicides. No 

mitigation measures specific to wilderness or other 

special areas were identified in the 2007 PEIS. 

However, all pertinent mitigation in the Vegetation, 

Fish and Other Aquatic Resources, Wildlife Resources, 

Recreation, and Human Health and Safety sections 

would potentially be applicable to herbicide treatments 

in these areas.

Summary of Herbicide Impacts

The 2007 PEIS provides a general overview of the 

effects of herbicide treatments on wilderness and other 

special areas (USDOI BLM 2007a:4-156 to 4-157). The 

discussion addresses herbicide treatments in general, 

and does not include a discussion of impacts specific to 

any of the active ingredients currently approved for use. 

In general, herbicide treatments in wilderness and other 

special areas would have short-term adverse effects and 

long-term positive effects on special status area values. 

Herbicide treatments could result in short-term closures 

of special areas, and in disturbance and removal of 

vegetation from treated areas. In the case of wilderness 

areas and WSAs, only treatments that improve the 

natural condition of these areas would be allowed. 

Furthermore, use of motorized equipment to apply 

herbicides would need to be authorized based on further 

site-specific NEPA and minimum requirements 

analysis, in accordance with BLM policy. 

Long-term effects of treatments in special areas would 

be beneficial, as noxious weed infestations and risk of 

future catastrophic wildfires would be reduced in these 

areas. The reduction of hazardous fuels and noxious 

weeds on lands adjacent or near to special areas would 

provide long-term benefits by reducing the likelihood 

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ENVIRONMENTAL CONSEQUENCES

that noxious weeds would spread onto these unique 

areas, or that a catastrophic wildfire would burn through 

them, thus degrading their unique qualities. Herbicide 

treatments in wilderness areas and WSAs, if successful,

would potentially improve the naturalness component of 

wilderness character.

Impacts by Alternative

Generally, there would be few differences between the 

alternatives as far as potential effects to wilderness and 

other special areas, as the extent of treatments in these 

areas would likely be the same under all the alternatives.

Alternative A – Continue Present Herbicide Use (No 

Action Alternative)

Under the No Action Alternative, the BLM would 

continue its herbicide treatments in wilderness and other 

special areas with the 18 currently approved herbicides.

For example, herbicide treatments would continue to be 

used to control incipient populations of noxious weeds 

and other invasive species in order to prevent the 

expansion of these populations in wilderness and other 

special areas. Additionally, the risk of wildland fire 

could be reduced in these areas. Therefore, treatments 

would benefit the targeted areas and help protect their 

unique qualities. 

Special areas that receive herbicide treatments would 

continue to be affected by disturbance associated with 

access to the treatment site (particularly for repeat 

treatments), and by a temporary reduction in the 

“naturalness” of the treated area with the loss of target 

vegetation. Additionally, users of these areas might be 

impacted by short-term closures following herbicide 

applications (see the Recreation section for more

information). In most cases, the benefits of eradicating 

noxious weeds and reducing the risk of wildland fire 

would outweigh the potential short-term effects of 

chemical treatments.

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, effects to wilderness 

and other special areas would be similar to those under 

the No Action Alternative. Herbicide treatments in these 

areas would likely involve the three new active 

ingredients, as warranted, and could be more effective at 

controlling target species as a result. However, given 

that the overall method and extent of treating wilderness 

and species areas would be more or less the same as 

under the No Action Alternative, there would be only 

minor differences as far as effects to these areas.

The three new active ingredients are all of low risk to 

human health (see the Human Health and Safety section 

for additional information), with no risk to public 

receptors under routine or accidental exposure 

pathways. However, the active ingredients that are 

likely to decrease in usage as a result of adding the three 

new active ingredients also have low to no risk to 

human health. Therefore, there would be very little 

difference between the Preferred Alternative and the No 

Action Alternative as far as potential impacts to the 

health of users of wilderness and other special areas 

from herbicide treatments.

Alternative C – No Aerial Application of New 

Herbicides 

While the three new herbicides would not be applied 

aerially under Alternative C, the total extent of aerial 

treatments using herbicides would be similar to that 

under Alternative B, as other herbicides could still be 

applied via this method. Overall, it is not expected that 

aerial applications would be used to target wilderness 

and other special areas, as treatments would generally 

not be this widespread. Impacts under this alternative 

would be similar to those under the other alternatives, 

with short-term adverse effects associated with 

treatments and long-term benefits associated with the 

removal of noxious weeds. Potential impacts to the 

health of users of wilderness and other special areas 

from herbicide treatments would also be similar to those 

under the other alternatives.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Rimsulfuron would not be used to treat vegetation under 

Alternative D, but treatments in wilderness and other 

special areas could be completed with any of the 

currently approved herbicides, aminopyralid, or 

fluroxypyr. The extent of treatments in wilderness and 

other special areas and the species targeted would be 

similar to those under the other alternatives. Therefore, 

effects to these areas would also be similar, with shortterm adverse effects associated with treatments and 

long-term benefits associated with the removal of 

noxious weeds. Potential impacts to the health of users 

of wilderness and other special areas from herbicide 

treatments would also be similar to those under the 

other alternatives.

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ENVIRONMENTAL CONSEQUENCES

Mitigation for Herbicide Treatment 

Impacts

The BLM’s SOPs for minimizing impacts to wilderness 

and other special areas, listed earlier in this section, 

would continue to be implemented when conducting 

vegetation treatments. These SOPs would help reduce 

short-term impacts associated with all herbicides, 

including aminopyralid, fluroxypyr, and rimsulfuron.

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. No mitigation measures are 

proposed specifically for wilderness or other special 

areas.

Recreation

In areas that support high recreation use, 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. In these areas, herbicide use 

is generally limited to spot treatments. However, larger 

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

No scoping comments specific to recreation were 

received by the BLM. 

Standard Operating Procedures

The 2007 PEIS presented several SOPs that the BLM 

follows to help minimize 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.

These SOPs would continue to apply to herbicide 

treatments involving the three new active ingredients. 

Additionally, SOPs identified in the Human Health and 

Safety, Fish and Aquatic Resources, and Wildlife 

Resources sections would further reduce risks to 

recreationists and the resources they use.

Summary of Herbicide Impacts

The 2007 PEIS provides a general discussion of the 

potential effects of herbicide treatments on recreation 

(USDOI BLM 2007a:4-160 to 4-161). This general 

effects analysis would also apply to treatments 

involving the three new herbicides, and is briefly 

summarized here.

Herbicide 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. 

The three new herbicides generally pose very little risk 

to human health for public receptors, even under 

scenarios involving an accidental spraying by an 

herbicide, entering a treated area soon after herbicide 

application, or accidentally coming into contact with 

herbicides that have drifted downwind. 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.

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ENVIRONMENTAL CONSEQUENCES

Over the long term, herbicide treatments would have a 

positive effect on recreation through the removal of 

undesirable vegetation on treated lands. Herbicide 

treatments would likely 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. 

Treatments to reduce fuels would reduce the risk of 

wildfire in or near recreation areas. Additionally, 

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)

Under the No Action Alternative, the BLM would 

continue its vegetation treatments with the 18 active 

ingredients that are currently approved for use. This 

alternative corresponds to the Preferred Alternative in 

the 2007 PEIS (USDOI BLM 2007a:4-162). The 

maximum acres of public lands treated with herbicides 

would remain at 932,000 annually, and the states with 

the most treatments would continue to include Idaho, 

Nevada, Wyoming, and New Mexico. While these 

states were estimated to account for 76 percent of 

treatment acres under this alternative, they accounted 

for only 18 percent of visitor days during 2012 (USDOI 

BLM 2012b). Therefore, it is likely that an extensive 

portion of the land affected by herbicide treatments 

would occur in areas with a relatively low density of 

recreational visitors. 

Under this alternative, short-term impacts and long-term 

benefits would occur on up to 932,000 acres of lands 

annually. Depending on the success of treatments, it is 

expected that degradation of public lands from wildland 

fires and infestations of invasive plants would decrease, 

and recreational users would be able to have improved 

outdoor experiences. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

This alternative would allow aminopyralid, fluroxypyr, 

and rimsulfuron to be used in the BLM’s herbicide 

treatment projects, allowing increased flexibility for 

meeting treatment objectives. The maximum land area 

treated and the states with the largest amount of 

treatment acres would be the same as under the No 

Action Alternative. Therefore, the nature, extent, and 

intensity of impacts to recreation would be similar to 

those under the No Action Alternative.

The long-term benefits associated with this alternative 

would also be similar to those under the No Action 

Alternative, given that the program goals and target 

species would not change. Allowing use of the three 

new herbicides could result in more effective 

treatments, which would have a slightly higher degree 

of benefit to recreation than under the No Action 

Alternative.

Alternative C – No Aerial Application of the New 

Herbicides

It is unlikely that aerial spraying would occur in high 

public use recreational areas under any of the 

alternatives. Although the new herbicides would not be 

applied aerially under Alternative C, aerial applications 

of currently approved herbicides would still occur in 

dispersed use areas at levels similar to those under the 

other alternatives. The maximum land area treated, and 

the states with the most treatment acres, would be the 

same as under the other alternatives. Therefore the 

nature, extent, and intensity of impacts to recreation also 

would be similar to those under the other alternatives.

The long-term benefits associated with Alternative C 

would be similar to those under the other alternatives, 

with a reduction in degradation of public lands used for 

recreation by invasive plants and wildland fire.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

While use of rimsulfuron would not be allowed under 

Alternative D, herbicide treatments would be completed 

with the 18 currently approved herbicides, as well as

aminopyralid and fluroxypyr. The maximum land area 

treated and the states with the largest treatment acreage 

would be the same as under the No Action Alternative 

and all of the action alternatives. Therefore, impacts to 

recreational sites and recreational users would be 

similar to those under the other alternatives.

The long-term benefits to recreation under this 

alternative would also be similar to those under the 

other alternatives. Program goals and target species 

would not change, so the only differences would be in 

terms of the effectiveness of treatments. Rimsulfuron 

would not be available to treat cheatgrass, but other 

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ENVIRONMENTAL CONSEQUENCES

herbicides such as imazapic and glyphosate would. 

Depending on the location and type of treatment, these 

currently approved herbicides may be less effective than 

rimsulfuron at controlling annual grasses in certain 

scenarios. 

Mitigation for Herbicide Treatment 

Impacts

The BLM’s SOPs for minimizing impacts to recreation, 

listed earlier in this section, would continue to be 

implemented when conducting vegetation treatments. 

These SOPs would help reduce short-term impacts 

associated with all herbicides, including aminopyralid, 

fluroxypyr, and rimsulfuron.

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. No 

mitigation measures that pertain specifically to 

recreation are proposed.

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. Public lands support

ranching (grazing leases), mining, active and passive 

recreation opportunities, and a myriad of other activities 

that westerners rely on. In addition to these resource 

uses, public lands provide social values that may not be 

readily quantifiable. 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. 

Therefore, 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 type of social and economic analysis presented in 

this PEIS will be similar to what was provided in the 

2007 PEIS. Given its programmatic nature, this PEIS 

will address only general effects and expected trends, 

with more detailed, site-specific analyses conducted at 

the local level during the development of herbicide 

treatment projects. Additionally, since the bulk of the 

analysis in the 2007 PEIS was general to herbicide 

treatments, and not specific to the herbicides being 

considered, much of the analysis is the same for 

treatments involving the three new herbicides. This 

information will be referenced and summarized, as 

appropriate, with additional discussion that involves any 

new information that is available.

Scoping Comments and Other Issues 

Evaluated in the Assessment

Several scoping comments were concerned with the 

potential economic impacts to home and commercial 

gardeners and composters associated with use of the 

new herbicides. Aminopyralid, in particular, was 

identified as a concern based on reports and personal 

observations about the persistence of this herbicide in 

manure, compost materials, and hay, and subsequent 

damage to crops where the contaminated materials were 

used. Additionally, a few comments cited potential 

damage to crops from movement of herbicides on 

windblown dust and off-site drift.

Other comments addressed the cost of the new 

herbicides relative to herbicides that are currently being 

used, and the cost of herbicide treatments in general, 

relative to other treatment methods. There was general 

support for aminopyralid, fluroxypyr, and rimsulfuron 

in terms of their effectiveness and the potential to 

reduce the cost of herbicide treatments.

As discussed in the 2007 PEIS (USDOI BLM 2007a:4-

164), the interests of all stakeholders must be 

considered when planning treatment programs, and the 

alternative selected for implementation must balance 

out the interests of national and local stakeholders. 

Standard Operating Procedures

The 2007 PEIS (USDOI BLM 2007a:4-164 to 4-165) 

lists SOPs that have been designed by the BLM to 

reduce potential adverse impacts to social and economic 

conditions from the application of herbicides: 

• Consider surrounding land use before selecting 

aerial spraying as a treatment 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.

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• 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 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 

vegetation of cultural significance to the tribes.

• 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 the public with 

educational information on the need for 

vegetation treatments and the use of 

herbicides in an IPM program for projects 

proposing local use of herbicides.

These SOPs would continue to apply to herbicide 

treatments involving the new chemicals. No additional 

mitigation for social and economic values were 

identified in the 2007 PEIS.

Impact Assessment Assumptions

This impact assessment generally makes the same 

assumptions that were discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-165). Site-specific information 

on likely use of the three new herbicides is unavailable, 

and no information on specific application parameters 

will be included. Other assumptions include the 

following:

• Communities that are particularly dependent on 

a single industry (e.g., ranching and recreationdependent communities) are more susceptible 

to the effects of herbicide use than other 

communities. 

• The proposed use of the new herbicides would 

only apply to public lands.

• None 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.

• Treatments involving the new herbicides would 

meet the project objective of improving the 

effectiveness of the BLM’s vegetation 

treatment programs. In turn, the cost of 

wildland fire suppression and the loss of life 

and property would be reduced. 

Summary of Herbicide Impacts

The 2007 PEIS provides a general discussion of the 

effects of herbicide treatments on social and economic 

values (USDOI BLM 2007a:4-165 to 4-166). These 

effects would continue to apply to herbicide treatments 

involving the three new herbicides. They generally 

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ENVIRONMENTAL CONSEQUENCES

include social effects deriving from perceptions of 

health and safety risks for different chemicals; the 

success or failure of treatments using different 

chemicals; economic effects associated with changes in 

range productivity, wildfire risk, and access or 

attractiveness for recreation activities, and associated 

changes in employment and income; and direct and 

indirect economic effects tied to the cost of applying the 

herbicides. 

Impacts of Aminopyralid

The BLM estimates that the cost per acre to apply 

aminopyralid, based on the typical application rate of 

this active ingredient, would be $6.73 per acre. 

Therefore, aminopyralid would be relatively 

inexpensive to apply, based on a review of the range of 

costs for the currently approved active ingredients 

provided in Table 3-21 ($1 to $115 per acre). 

Use of aminopyralid is a concern from an economic 

standpoint because of its persistence in plant materials. 

If manure or compost originating from plant materials 

that were previously treated with aminopyralid is used 

on personal or commercial crops, loss of broadleaf 

crops may occur. Incidents of crop and garden damage 

as a result of using organic matter with aminopyralid 

residues have been reported (Washington State 

University Extension 2011). In 2010, several farmers 

and gardeners in Washington State lost most of their 

vegetable crops as a result of herbicide residues from 

composted dairy manure (Oregon State University 

2011). Therefore, this active ingredient can be 

associated with economic impacts to private landowners 

if not used in accordance with the label directions. The 

BLM would follow all label instructions to prevent 

impacts to crops and gardens associated with use of this 

herbicide, including restrictions on grazing where 

applicable. The BLM would not export manure, plant 

residues, or other materials that may be treated with 

aminopyralid for use as soil amendments. 

Because aminopyralid is an active ingredient that targets 

broadleaf plants, it could be associated with damage to 

off-site crops as a result of herbicide drift. As discussed 

in the vegetation section, buffers would be required to 

prevent impacts to non-target plants, which would 

include commercial crops and other broadleaf plants. 

Therefore, the buffers specified in Table 4-8 would be 

applicable to treatments with aminopyralid that are near 

private lands.

Impacts of Fluroxypyr

According to estimates from the BLM, the cost per acre 

to apply fluroxypyr is $16.53, based on the typical 

application rate. It is relatively expensive, compared to 

the costs of the currently approved active ingredients 

(Table 3-21), but would only be used in small 

quantities.

Like aminopyralid, fluroxypyr targets broadleaf plants, 

and therefore may adversely affect nearby croplands 

and other private lands as a result of herbicide drift. As 

discussed in the Vegetation section, buffers would be 

required to prevent impacts to non-target plants, which 

would include commercial crops and other broadleaf 

plants. Therefore, the buffers specified in Table 4-8 

would be applicable to treatments with aminopyralid in

the vicinity of private lands.

Impacts of Rimsulfuron

The BLM estimates that the cost per acre to apply 

rimsulfuron, based on the typical application rate of this 

active ingredient, would be $2.81 per acre. It is 

relatively inexpensive, compared to the costs associated 

with the currently approved active ingredients (Table 

3-21). Rimsulfuron is substantially cheaper than 

imazapic, which costs $10 to $15 per acre, depending 

on the mode of application.

Rimsulfuron has activity on annual plants, and could 

harm certain crops and other non-target plants grown 

commercially. Buffers would be required to prevent 

impacts to non-target plants on private lands, as 

discussed in the Vegetation section and Table 4-8, to 

reduce the potential for adverse economic effects to 

nearby landowners.

Impacts by Alternative

Impacts Common to All Alternatives

The 2007 PEIS (USDOI BLM 2007a:4-171) includes a 

substantial discussion on the impacts of herbicide 

treatments on population and demography, 

environmental justice, protection of children, 

employment and income, perceptions and values, 

invasive species control cost savings, wildland fire cost 

savings, economic activity and public revenues 

generated from BLM lands, expenditures by the BLM, 

and effects on private property. Because the three new 

active ingredients would be incorporated into larger 

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herbicide treatment programs, with the same maximum 

acreage assumed, these general impacts associated with 

herbicide treatments would continue to occur. 

Differences would be limited to which active 

ingredients would be used. These differences are 

captured in the earlier discussion specific to each of the 

three new active ingredients, as well as in the 

discussions for each of the alternatives. 

Under all alternatives, herbicide treatments could occur 

on public lands near minority or low-income 

populations. As discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-167), it is not possible to determine 

whether these populations would be disproportionately 

affected at the broad scale of analysis in this PEIS. 

Specific evaluation of environmental justice impacts 

would be conducted in concert with environmental 

analyses for site-specific treatment project proposals.

Additionally, ongoing consultation and close 

communication with Indian tribes about the locations

and timing of future herbicide treatments would 

continue to address potential impacts to Native 

American populations.

Impacts of Individual Alternatives

Alternative A – Continue Present Herbicide Use 

(No Action Alternative)

This alternative corresponds to the Preferred Alternative 

under the 2007 PEIS (USDOI BLM 2007a:4-172 to 4-

173). Herbicide treatments would occur on up to 

932,000 acres annually in 17 western states, and would 

include only the 18 currently approved herbicides. 

These treatment levels would be much the same as at 

present, so there would likely be little change to existing 

patterns and trends in population or demographic 

conditions in the western U.S. Additionally, no changes 

in employment associated with herbicide treatment 

would occur.

Herbicide treatments would continue to generate some 

employment in geographic areas affected by the 

treatments, but the jobs would generally be short-term, 

temporary positions or contracted work, which do not 

encourage in-migration of workers and their families.

Herbicide treatments would take place on public lands, 

away from areas where children are known to 

congregate, such as schools and playground. While 

children may visit public lands or live in the vicinity, 

they are unlikely to make up a disproportionate 

percentage of nearby populations or visitors to public 

lands. Buffers between residences and treatment areas 

and advance communication of treatments and site 

closures would minimize risks to children. Therefore, 

disproportionate impacts to children should not occur. 

The 2007 PEIS estimated the costs to treat vegetation 

under the Preferred Alternative (USDOI BLM 2007a:4-

172), which corresponds to the No Action Alternative 

for this PEIS. This estimate is based on a maximum

total annual treatment area of 932,000 acres. While the 

BLM’s current levels of treatment are much lower, this 

PEIS assumes that the assumptions for treatment acres 

in the 2007 PEIS will carry forward. Assuming this 

maximum acreage and inflation costs of approximately 

3 percent per year since 2007, the estimated costs to 

treat vegetation using herbicides would be 

approximately $110 million per year. 

Herbicide treatments that reduce fire risk would 

continue to be associated with cost savings associated 

with reduced need for wildland fire suppression and 

reduced loss of property. These savings cannot be 

quantified. Herbicide treatments would also help reduce 

the spread of noxious weeds, which would provide 

some level of economic benefit by reducing the future 

costs of vegetation management.

Commercial activities that occur on public lands, such 

as timber sales, grazing, and recreation would continue 

to be impacted a minor amount by herbicide treatments. 

Additionally, there would continue to be a risk for 

herbicide treatments to impact private property, which 

could result in damage to crops or other non-target 

plants of commercial value. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, the total acres treated 

with herbicides each year would be the same as under 

the No Action Alternative. However, the breakdown in

use of the various active ingredients would change with 

the introduction of aminopyralid, fluroxypyr, and 

rimsulfuron. Under this alternative, there would be a 

substantial reduction (by approximately 21 percent) in 

the use of glyphosate, imazapic, and picloram, and the 

new active ingredients aminopyralid and rimsulfuron 

would make up approximately 26 percent of herbicide 

use, based on acres treated. Fluroxypyr, though 

relatively expensive, would only constitute 

approximately 1 percent of all acres treated. Glyphosate, 

imazapic, and picloram are more expensive than 

aminopyralid and rimsulfuron. Therefore, the estimated 

costs to treat vegetation with herbicides (based on the 

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ENVIRONMENTAL CONSEQUENCES

cost and projected future use of each active ingredient) 

would be lower under this alternative than under the No 

Action Alternative. The estimated reduction in herbicide 

costs is 1 to 2 percent per year. 

In most other regards, the potential social and economic 

impacts associated with herbicide treatments would be 

similar to those under the No Action Alternative. While 

there could be minor differences in the effectiveness of 

certain herbicide treatments with the availability of the 

new active ingredients, these differences would not 

reflect measurable changes in socioeconomic impacts. 

No changes in populations and demography, or 

employment, would occur. The potential for 

disproportionate adverse effects to minority populations 

and children would continue to be low. The level of 

economic benefit associated with fuels reduction and 

control of noxious weeds would be similar to that under 

the No Action Alternative, as would the level of risk to 

commercial activities on public lands and adjacent 

private properties. 

This alternative would allow the use of aminopyralid, 

which is of concern from an economic standpoint for its 

potential to damage crops and gardens if used 

inappropriately. However, the currently approved 

herbicides clopyralid and picloram are also pyridine 

carboxylic acids with a similar residual activity in 

manure and plant materials. While total use of this class 

of herbicides would increase by approximately 7 

percent relative to the No Action Alternative, in all 

cases, risks could be avoided by adhering to the 

restrictions on the herbicide label.

Alternative C – No Aerial Application of New 

Herbicides

Under Alternative C, the total acres treated with 

herbicides each year would be the same as under the 

other alternatives, and the list of active ingredients used 

would be the same as under the Preferred Alternative.

However, the relative amount used would vary 

somewhat because the three new active ingredients 

would only be applied using ground methods, and could 

not be utilized in aerial-based herbicide treatments.

Under this alternative, there would be a smaller 

reduction in use of more expensive active ingredients, 

as less of the new active ingredients would be used than 

under the Preferred Alternative. Costs to treat vegetation 

using herbicides (based on the cost and projected future 

use of each active ingredient) would likely decrease, but 

by a lesser amount, estimated at less than 1 percent per 

year. 

Other social and economic impacts associated with 

herbicide treatments would be similar to those under the 

other alternatives. No changes in populations and 

demography, or employment, would occur. The 

potential for disproportionate adverse effects to minority 

populations and children would continue to be low. The 

level of economic benefit associated with fuels 

reduction and control of noxious weeds would be 

similar to that under the other alternatives, as would the 

level of risk to commercial activities on public lands 

and adjacent private properties. 

This alternative would entail slightly less use of 

aminopyralid than under the Preferred Alternative, but 

total use of the three pyridine carboxylic acids of 

particular concern would be approximately 1 percent 

less than under the Preferred Alternative. In all cases, 

risks could be avoided by adhering to the restrictions on 

the herbicide label.

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under Alternative D, the maximum acreage treated with 

herbicides each year would be the same as under the 

other alternatives. The list of active ingredients would 

be different than under the other alternatives, however, 

as aminopyralid and fluroxypyr would be approved for

use and rimsulfuron would not. Under this alternative, 

there would be very little reduction in the use of 

glyphosate and imazapic, but a substantial reduction in 

the use of picloram. Costs to treat vegetation using 

herbicides would not decrease by a substantial amount, 

relative to the No Action Alternative. The herbicide cost 

reduction is estimated at a fraction of a percent per year, 

much lower than under Alternatives B and C. 

Other social and economic impacts associated with 

herbicide treatments would be similar to those under the 

other alternatives. No changes in populations and 

demography, or employment, would occur. The 

potential for disproportionate adverse effects to minority 

populations and children would continue to be low. The 

level of economic benefit associated with fuels 

reduction and control of noxious weeds would be 

similar to that under the other alternatives, as would the 

level of risk to commercial activities on public lands 

and adjacent private properties. 

Use of aminopyralid under Alternative D would be the 

same as under the Preferred Alternative, and total use of 

the three pyridine carboxylic acids of particular concern 

would also be the same as under the Preferred 

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ENVIRONMENTAL CONSEQUENCES

Alternative. In all cases, risks could be avoided by 

adhering to the restrictions on the herbicide label.

Mitigation for Herbicide Treatment 

Impacts

The SOPs listed earlier in this section were designed to 

reduce potential adverse impacts to social and economic 

conditions from the application of herbicides. They 

would apply to all treatments involving aminopyralid, 

fluroxypyr, and rimsulfuron. 

No mitigation measures are proposed for social and 

economic resources.

Human Health and Safety

The use of herbicides 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. As part of the PEIS, an HHRA has been 

conducted to evaluate the potential human health risks 

of aminopyralid, fluroxypyr, and rimsulfuron as a result 

of herbicide exposure during and/or 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.

The three new active ingredients may be used with one 

or more previously approved active ingredients, either 

as a formulation or a tank mix (see Section on Herbicide

Formulations Used by the BLM and Tank Mixes in 

Chapter 2). The human health risks associated with the 

currently approved herbicides may be found in the 2007

PEIS (USDOI BLM 2007a:4-182 to 4-194). Only the 

three herbicides proposed for use are considered in this 

PEIS.

Scoping Comments and Other Issues 

Evaluated in the Assessment

The BLM received a few scoping comments expressing 

concerns about the health risks associated with 

herbicides. In particular, one comment stressed the need 

for additional preventative measures and oversight of 

existing SOPs to protect human health, after reports that 

an individual was sprayed during an aerial herbicide 

application, and was not notified beforehand that the 

treatment would occur. Another comment indicated that 

the existing buffers between treatments and human 

habitation are not adequate. However, one comment 

also pointed out that risks associated with herbicides 

should be considered alongside the risks associated with 

other types of vegetation treatments that would be used 

if herbicides were not allowed. None of the comments 

specifically addressed the three active ingredients that 

are being considered in this PEIS.

Standard Operating Procedures

The 2007 PEIS lists SOPs that were designed by the 

BLM to reduce potential unintended impacts to human 

health from the application of herbicides. These SOPs 

would continue to apply to herbicide treatments 

involving aminopyralid, fluroxypyr, and rimsulfuron, 

and are considered when evaluating impacts to human 

health and safety: 

• 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 SDSs/MSDSs 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 

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ENVIRONMENTAL CONSEQUENCES

ensure that impacts to humans are minimized to the 

extent practical.

Human Health Risk Assessment 

Methodology

The HHRA for aminopyralid, fluroxypyr, and 

rimsulfuron follows the same methodology as the 

HHRA for the 2007 PEIS (USDOI BLM 2007a:4-175 

to 4-181), as discussed in detail in the HHRA. This 

methodology is summarized here.

The BLM HHRA follows the four-step risk assessment 

model identified by the National Academy of Sciences 

(1983). The steps are: 1) hazard identification, 2) doseresponse assessment, 3) exposure assessment, and 4) 

risk characterization. 

Hazard Identification

The hazard identification section provides information 

on the herbicide active ingredient characteristics and 

usage, and toxicity profiles. Both acute (short-term) and 

chronic (longer-term) toxicity information is 

considered. Acute toxicity endpoints include oral, 

inhalation, and dermal acute toxicity; eye irritation; skin 

irritation; and dermal acute toxicity. Acute toxicity 

endpoints include the median lethal dose (the dose that 

kills 50 percent of test animals), the dose at which no 

adverse effects were seen, and the lowest level at which 

adverse effects were seen.

Inert ingredients were considered in the HHRA for the 

2007 PEIS. As the inert ingredients found in 

formulations of the three new herbicides would be the 

same as those previously considered, no additional 

analysis of these chemicals was done in the current 

HHRA. The previous HHRA found that the majority of 

inert ingredients are of minimal risk, and a few are in 

the category of unknown toxicity. 

Dose-Response Assessment

The dose-response assessment identifies the types of 

adverse health effects an herbicide may potentially 

cause, and defines the relationship between the dose of 

an herbicide and the likelihood or magnitude of an 

adverse effect (response). Dose-response values are 

used to derive risk estimates. As none of the three 

herbicides evaluated are designated as potential 

carcinogens by the USEPA, the dose-response 

assessment focuses on non-carcinogenic effects (i.e., 

potential toxic effects other than cancer). 

Exposure Assessment 

The exposure assessment predicts 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. Additionally, 

exposures were evaluated both for applications using 

the maximum application rate designated by the 

herbicide label, and for applications using a typical 

application rate defined by BLM. 

Occupational Exposure Scenarios. Routine exposures 

for occupational receptors include dermal and inhalation 

exposures that could occur by a worker during an 

application of the herbicide. 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/UTV and 

truck mount applications), applicators, mixer/loaders, 

and applicator/mixer/loaders were evaluated. The 

exposure dose was calculated using the herbicide 

application rate and the acres treated per day.

Accidental exposures for occupational receptors could 

occur via spills or direct spray onto a worker. As a 

worst-case scenario for an accidental exposure, a direct 

spill event on an occupational receptor was evaluated. 

The spill scenario assumes that 0.5 liter (1⁄2 quart) of the 

formulation is spilled on a worker receptor. It is 

assumed that 80 percent of the spill lands on clothing 

and 20 percent lands on bare skin. The penetration rate 

through clothing is assumed to be 30 percent. 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. Public use exposure 

scenarios involve public receptors using public lands 

treated with herbicides. Public receptors include: 1)

hikers/hunters; 2) berry pickers - child and adult; 3) 

anglers; 4) swimmers - child and adult; 5) nearby 

residents - child and adult; and 6) Native Americans -

child and adult. Two types of scenarios are addressed: 

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• Routine-use exposure scenarios in which a 

public receptor is exposed to herbicide active 

ingredient(s) that have drifted outside the area 

of application. It is assumed that the public 

would heed posted signs and not enter a 

treatment area during the treatment.

• Accidental scenarios where public receptors 

may prematurely enter a sprayed area (a reentry 

scenario), be sprayed directly, or contact water 

bodies that have accidentally been sprayed 

directly or into which an herbicide active 

ingredient has accidentally been spilled. 

These public exposure scenarios are thought to be 

unlikely and represent worst-case conditions. Potential 

exposure pathways include: 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.

Risk Characterization

The risk characterization 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 dose-response 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 Aggregate Risk Index (ARI) is a numeric 

expression of risk that combines potential risks from 

various exposure pathways, as discussed in more detail 

in the HHRA (AECOM 2014c). The ARI is compared 

against a target value of 1. An ARI that is greater than 1 

does not exceed the USEPA’s level of concern, and 

indicates that no adverse health effects are expected. An 

ARI below 1 indicates a potential concern for human 

health.

Uncertainty in the Risk Assessment 

Process

The HHRA incorporates various conservative 

assumptions to compensate for uncertainties in the risk 

assessment process. Conservative assumptions are made 

throughout the risk assessment process, since every 

assumption introduces some degree of uncertainty into 

the process. Using conservative assumptions 

exaggerates the risks to err on the side of protecting 

human health. 

Human Health Risks Associated with 

Herbicides

The types of potential impacts to human health and 

safety associated with herbicide use in general are

discussed in the 2007 PEIS (USDOI BLM 2007a:4-181 

to 4-182). This general analysis would continue to apply 

to herbicide treatments involving aminopyralid, 

fluroxypyr, and rimsulfuron. It is summarized here, 

followed by a more detailed analysis specific to the

three new active ingredients.

Herbicides can be toxic to humans 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 exposure to 

herbicides include nausea, dizziness, or reversible 

abnormalities of the nervous system. In extreme cases 

of prolonged, repeated, and excessive exposure, longerterm 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. The label instructions of each 

herbicide provide restrictions and precautions on usage 

that minimize the risk of these effects. As part of 

registration of herbicides, the USEPA adheres to a 

uniform, health-based standard to ensure a “reasonable 

certainty of no harm” to consumers. 

The greatest risk for occupational exposure to 

herbicides occurs when workers must directly handle 

and/or mix chemicals. Spot and localized applications, 

which require the most hands-on use of herbicides, 

carry the greatest risk of exposure. Workers can also 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 

SDSs/MSDSs detail these application requirements in 

addition to safety guidelines.

Public receptors can be exposed to herbicides by being 

accidentally sprayed, by entering areas soon after 

treatment (e.g., eating berries or other foods, and 

touching vegetation), drinking contaminated water, or 

accidentally coming into contact with herbicides that 

BLM Vegetation Treatments Using Herbicides 4-89 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

have drifted downwind. Members of the general public, 

both visitors and residents, are less likely to be 

repeatedly exposed than vegetation management 

workers. The BLM has SOPs in place to prevent 

exposure of the public to treated areas. However, there 

has been one documented account of an accidental 

spraying (via drift) of a worker engaged in other 

resource work at the same time as an aerial herbicide 

application in Nevada. The findings of this incident 

indicate that both the contractor doing the spraying and 

the BLM failed to implement SOPs that would have 

prevented this occurrence. While the BLM has taken 

steps to ensure that SOPs are followed in the future, the 

incident shows that even with SOPs in place, accidental 

exposures to herbicides can occur. 

Tables 4-14 and 4-15 are summary tables that show 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. The 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. Tables 4-16 through 4-24 present 

more detailed tables of ARIs for each herbicide and 

receptor under occupational and public exposure 

scenarios. Based on the HHRA (AECOM 2014c), the 

three herbicides generally pose very little risk to human 

health, with rimsulfuron posing some risk to 

occupational receptors under accidental exposure 

scenarios.

Aminopyralid

Based on the hazard identification presented in the 

HHRA, aminopyralid has low acute toxicity via oral, 

dermal, and inhalation routes of exposure, but may 

cause severe eye irritation in some forms. At mid- and 

high-level doses, adverse effects to the stomach, ileum,

and cecum have been noted. Developmental and 

reproduction studies indicate no evidence that fetuses or 

offspring have increased susceptibility to aminopyralid. 

Aminopyralid has been classified as “not likely to be 

carcinogenic to humans,” and there is no evidence that 

it is mutagenic or an endocrine disrupter (USEPA 

2009b).

Dermal studies indicate that aminopyralid does not have 

significant toxicity via the dermal route of exposure, as 

it is either not absorbed or poorly absorbed through the 

skin. For this reason, ARIs were derived using oral and 

inhalation exposures.

As shown in Tables 4-14 and 4-15, there are no risks to 

occupational or public receptors from exposures 

resulting from routine use (typical or maximum 

application rate) or accidental scenarios. Tables 4-16 

through 4-18 show the detailed HHRA results for 

aminopyralid, presenting ARIs by receptor and 

exposure scenario. For all receptors, ARIs were all well 

above 1, with the lowest ARI of 94 for a child 

swimming in a water body following a helicopter spill 

(Table 4-18). This exposure pathway assumes incidental 

ingestion of water while swimming. These results 

indicate that aminopyralid does not present an 

unacceptable risk to occupational or public receptors, 

even under worst-case accidental exposure scenarios.

Fluroxypyr

Based on the hazard identification in the HHRA, 

fluroxypyr has low acute toxicity via oral and dermal 

routes, and moderate acute toxicity via inhalation. It is 

not irritating to the skin, but is a mild eye irritant. At 

high doses, it can target the kidney and result in other 

adverse health effects. There is no evidence of increased 

susceptibility following in utero, pre-natal, or post-natal 

exposure. Endocrine disruption studies have not been 

conducted. There is no indication that fluroxypyr is 

carcinogenic or mutagenic (USEPA 2007).

Based on studies involving subchronic dermal 

exposures of high doses of fluroxypyr, in which no 

effects were observed, the USEPA has determined that 

dermal risk assessment is not required for this chemical 

(USEPA 2007). Therefore, ARIs were derived using 

oral and inhalation exposures.

As shown in Table 4-14 and 4-15, and shown in more 

detail in Tables 4-20 and 4-21, there are no risks to 

occupational or public receptors from exposures 

resulting from routine use (typical or maximum 

application rate) or accidental scenarios. For all 

receptors, ARIs were above 1, with the only ARIs 

below 500 for accidental exposures involving 

swimming in a water body following an accidental spill 

of fluroxypyr. These exposure pathways assume 

incidental ingestion of water while swimming (Table 

4-21). The lowest ARI was for a Native American child 

swimming in a body of water following a helicopter 

spill. These results indicate that fluroxypyr does not 

present an unacceptable risk to occupational or public 

receptors, even under worst-case accidental exposure 

scenarios.

BLM Vegetation Treatments Using Three New Herbicides 4-90 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-91 January 2016

Final Programmatic EIS

TABLE 4-14

Herbicide Risk Categories by Aggregate Risk Index for Occupational Receptors

Receptor

Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Accid1 Typ Max Accid Typ Max

Accid

Typ2 Max2

Plane - pilot 03 0 NC 0 0 NC 0 0 L M 

Plane - mixer/loader 0 0 NC 0 0 NC 0 0 L M 

Helicopter - pilot 0 0 NC 0 0 NC 0 0 L M 

Helicopter - mixer/loader 0 0 NC 0 0 NC 0 0 L M 

Human/backpack - applicator/mixer/loader 0 0 NC 0 0 NC 0 0 L M 

Human/horseback - applicator/mixer/loader 0 0 NC 0 0 NC 0 0 L M 

ATV/UTV - applicator4 0 0 NC 0 0 NC 0 0 L M 

ATV/UTV - mixer/loader 0 0 NC 0 0 NC 0 0 L M 

ATV/UTV - applicator/mixer/loader 0 0 NC 0 0 NC 0 0 L M 

Truck - applicator4 0 0 NC 0 0 NC 0 0 L M 

Truck - mixer/loader 0 0 NC 0 0 NC 0 0 L M 

Truck - applicator/mixer/loader 0 0 NC 0 0 NC 0 0 L M 

1 As a main heading: Typ = Typical application rate; Max = Maximum application rate; and Accid = Accidental rate. Typical and maximum application rate categories include short-, intermediate-, and 

long-term exposures. Accidental scenario category includes accidents with herbicide mixed at both the typical and maximum application rates and with a concentrated herbicide. 2 As a subheading of the Accidental scenario category: Typ = solution mixed for the typical application rate; and Max = solution mixed for the maximum application rate. 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); and NC = Not calculated. The reported risk 

category represents the typical/most common risk level for estimated risks from various time periods. See Tables 4-16, 4-19 and 4-22 for the range of risk levels for each scenario. Accidental scenario 

ARIs were not calculated for aminopyralid or fluroxypyr because accidental scenarios assume a spill directly onto the receptor and aminopyralid and fluroxypyr are not toxic via the dermal route of 

exposure.

4 ATV/UTV and Truck categories include spot and boom/broadcast application scenarios.
BLM Vegetation Treatments Three New Herbicide

ENVIRONMENTAL CONSEQUENCES

4-92 January 2016

Final Programmatic EIS

TABLE 4-15 

Herbicide Risk Categories by Aggregate Risk Index for Public Receptors

Receptor

Aminopyralid Fluroxypyr Rimsulfuron

Typ1 Max1 Accid1 Typ Max Accid Typ Max Accid

Hiker/hunter (adult) NC NC NC NC NC NC 02 0 0 

Berry picker (child) NC NC NC NC NC NC 0 0 0 

Berry picker (adult) NC NC NC NC NC NC 0 0 0 

Angler (adult) NC NC NC NC NC NC 0 0 0 

Residential (child) NC NC NC NC NC NC 0 0 0 

Residential (adult) NC NC NC NC NC NC 0 0 0 

Native American (child) 0 0 0 0 0 0 0 0 0 

Native American (adult) 0 0 0 0 0 0 0 0 0 

Swimmer (child) 0 0 0 0 0 0 NC NC NC

Swimmer (adult) 0 0 0 0 0 0 NC NC NC

1 As a main heading: Typ = Typical application rate; Max = Maximum application rate; and Accid = Accidental rate. Typical and maximum application rate categories include short-, intermediate-, and 

long-term exposures. 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); and NC = Not calculated. The reported risk category represents the typical/most common risk level for estimated risks from various time periods. 

See Tables 4-17, 4-18, 4-20, 4-21, 4-23, and 4-24 for the range of risk levels for each scenario. For aminopyralid and fluroxypyr, no dose-response values are available for dermal exposure or acute 

dietary exposure due to low toxicity. For rimsulfuron, no dose-response values are available for the incidental oral pathway due to use pattern.
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-93 January 2016

Final Programmatic EIS

TABLE 4-16

Aminopyralid Aggregate Risk Indices – Occupational Scenarios

Application 

Type

Application 

Vehicle

Application 

Method Receptor1

Typical Application Rate Scenario 

ARIs

Maximum Application Rate Scenario 

ARIs

Accidental 

Scenario 

ARIs (Shortterm Dermal)

ShorttermIntermediatetermLongtermShorttermIntermediatetermLongtermConcentrated 

Solution2

Aerial Plane Fixed Wing Pilot 15,588 15,588 NC 3,684 3,684 NC NC

Aerial Plane Fixed Wing Mixer/Loader 3,643 3,643 NC 861 861 NC NC

Aerial Helicopter Rotary Pilot 38,971 38,971 NC 9,211 9,211 NC NC

Aerial Helicopter Rotary Mixer/Loader 9,107 9,107 NC 2,125 2,152 NC NC

Ground Human Backpack Applicator/Mixer/Loader 684,755 684,755 NC 121,388 121,388 NC NC

Ground Human Horseback Applicator/Mixer/Loader 91,301 91,301 NC 36,416 36,416 NC NC

Ground ATV/UTV Spot Applicator 217,436 217,436 NC 42,828 42,828 NC NC

Ground ATV/UTV Spot Mixer/Loader 4,856,816 4,856,816 NC 860,981 860,981 NC NC

Ground ATV/UTV Spot Applicator/Mixer/Loader 202,338 202,338 NC 39,855 39,855 NC NC

Ground ATV/UTV Boom/Broadcast Applicator 779,412 779,412 NC 153,520 153,520 NC NC

Ground ATV/UTV Boom/Broadcast Mixer/Loader 1,517,755 1,517,755 NC 322,868 322,868 NC NC

Ground ATV/UTV Boom/Broadcast Applicator/Mixer/Loader 419,968 419,968 NC 82,721 82,721 NC NC

Ground Truck Mount Spot Applicator 119,208 119,208 NC 19,273 19,273 NC NC

Ground Truck Mount Spot Mixer/Loader 2,396,455 2,396,455 NC 322,868 322,868 NC NC

Ground Truck Mount Spot Applicator/Mixer/Loader 110,931 110,931 NC 17,935 17,935 NC NC

Ground Truck Mount Boom/Broadcast Applicator 415,686 415,686 NC 122,816 122,816 NC NC

Ground Truck Mount Boom/Broadcast Mixer/Loader 809,469 809,469 NC 191,329 191,329 NC NC

Ground Truck Mount Boom/Broadcast Applicator/Mixer/Loader 223,983 223,983 NC 66,177 66,177 NC NC 1 Receptor refers to a single worker doing all of the listed tasks.

2 Based on the assumption that a spill of concentrated liquid occurs to worker skin.

The ARI is based on inhalation exposure because based on the toxicity assessment, dermal exposure is not of concern. Values less than 1 represent a level of concern.

NC = Not calculated. Based on toxicity assessment, dermal exposure is not of concern, and long-term inhalation is not a concern for seasonal treatment.
BLM Vegetation Treatments Three New Herbicide

ENVIRONMENTAL CONSEQUENCES

4-94 January 2016

Final Programmatic EIS

TABLE 4-17

Aminopyralid Aggregate Risk Indices, Routine Exposure Scenarios for Public Receptors, Short-term Exposure

Typical Application Rate Scenario ARIs Maximum Application Rate Scenario ARIs

AgDrift 

Scenario Aerial Aerial Aerial Aerial Ground Ground Aerial Aerial Aerial Aerial Ground Ground

Land Type1 Nonforested

Nonforested Forested Forested NA NA NonforestedNonforested Forested Forested NA NA

Equipment Plane Helicopter Plane Helicopter Low 

Boom

High 

Boom Plane Helicopter Plane Helicopter Low Boom

High 

Boom

Hiker/Hunter 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Berry Picker 

(Child) NC NC NC NC NC NC NC NC NC NC NC NC

Berry Picker 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Angler 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Residential 

(Child) NC NC NC NC NC NC NC NC NC NC NC NC

Residential 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Native 

American 

(Child)

9,894,117 9,904,690 9,812,094 9,950,628 9,951,298 9,946,385 7,013,584 7,021,934 6,957,082 7,055,988 7,056,377 7,052,925

Native 

American 

(Adult)

19,227,567 19,248,114 19,068,170 19,337,386 19,338,688 19,329,142 13,629,732 13,645,958 13,519,929 13,712,136 13,712,892 13,706,184

Swimmer 

(Child) 1,982 1,984 1,966 1,994 1,994 1,993 1,405 1,407 1,394 1,414 1,414 1,413

Swimmer 

(Adult) 17,752 17,771 17,605 17,853 17,855 17,846 12,584 12,599 12,482 12,660 12,660 12,65

1 Land type is not applicable to ground scenarios.

ARI values less than 1 represent a level of concern. ARI does not include dietary or dermal exposure due to low toxicity. ARIs are based on swimming exposure.

NA = Not applicable.

NC = Not calculated. No dose-response values are available for dermal exposure or acute dietary exposure due to low toxicity.
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-95 January 2016

Final Programmatic EIS

TABLE 4-18

Aminopyralid Aggregate Risk Indices for Accidental Exposure Scenarios for Public Receptors Based on Maximum Application Rates

Receptor

Dermal Contact Exposure Pathways Dietary Exposure Pathways

Direct 

Spray of 

Receptor

Dermal 

Contact 

with 

Foliage

Swimming1 Drinking Water Ingestion Fish Ingestion

Berry 

Ingestion Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Angler NC NC -- -- -- NC NC NC NC NC NC --

Berry Picker 

(Adult) NC NC -- -- -- NC NC NC -- -- -- NC

Berry Picker 

(Child) NC NC -- -- -- NC NC NC -- -- -- NC

Hiker/Hunter NC NC -- -- -- NC NC NC -- -- -- --

Native 

American 

(Adult)

NC NC 102,250,368 912,950 3,195,324 NC NC NC NC NC NC NC

Native 

American 

(Child)

NC NC 52,615,970 469,785 1,644,249 NC NC NC NC NC NC NC

Residential 

(Adult) NC NC -- -- -- -- -- -- -- -- -- --

Residential 

(Child) NC NC -- -- -- -- -- -- -- -- -- --

Swimmer 

(Adult) -- -- 94,403 843 2,950 -- -- -- -- -- -- --

Swimmer 

(Child) -- -- 10,542 94 329 -- -- -- -- -- -- --

1 Includes incidental ingestion for the swimmer. Incidental ingestion is not included for the Native American pathway because the drinking water pathway is included. 2 Assumes accidental spray of water body.

-- = Receptor not exposed via this pathway.

ARI values less than 1 represent a level of concern.

NC = Not calculated. No dose-response values available.
BLM Vegetation Treatments Three New Herbicide

ENVIRONMENTAL CONSEQUENCES

4-96 January 2016

Final Programmatic EIS

TABLE 4-19

Fluroxypyr Aggregate Risk Indices – Occupational Scenarios

Application 

Type

Application 

Vehicle

Application 

Method Receptor1 

Typical Application Rate Scenario 

ARIs

Maximum Application Rate Scenario 

ARIs

Accidental 

Scenario ARIs 

(Short-term 

Dermal)

ShorttermIntermediatetermLongtermShorttermIntermediatetermLongtermConcentrated 

Solution2

Aerial Plane Fixed Wing Pilot 4,497 4,497 4,497 779 779 779 NC

Aerial Plane Fixed Wing Mixer/Loader 1,051 1,051 1,051 182 182 182 NC

Aerial Helicopter Rotary Pilot 11,242 11,242 11,242 1,949 1,949 1,949 NC

Aerial Helicopter Rotary Mixer/Loader 2,627 2,627 2,627 455 455 455 NC

Ground Human Backpack Applicator/Mixer/Loader 197,525 197,525 197,525 25,678 25,678 25,678 NC

Ground Human Horseback Applicator/Mixer/Loader 26,337 26,337 26,337 7,703 7,703 7,703 NC

Ground ATV/UTV Spot Applicator 62,722 62,722 62,722 9,060 9,060 9,060 NC

Ground ATV/UTV Spot Mixer/Loader 1,401,004 1,401,004 1,401,004 182,131 182,131 182,131 NC

Ground ATV/UTV Spot Applicator/Mixer/Loader 58,367 58,367 58,367 8,431 8,431 8,431 NC

Ground ATV/UTV Boom/Broadcast Applicator 224,830 224,830 224,830 32,475 32,475 32,475 NC

Ground ATV/UTV Boom/Broadcast Mixer/Loader 437,814 437,814 437,814 68,299 68,299 68,299 NC

Ground ATV/UTV Boom/Broadcast Applicator/Mixer/Loader 121,145 121,145 121,145 17,499 17,499 17,499 NC

Ground Truck Mount Spot Applicator 34,387 34,387 34,387 4,077 4,077 4,077 NC

Ground Truck Mount Spot Mixer/Loader 691,285 691,285 691,285 68,299 68,299 68,299 NC

Ground Truck Mount Spot Applicator/Mixer/Loader 31,999 31,999 31,999 3,794 3,794 3,794 NC

Ground Truck Mount Boom/Broadcast Applicator 119,910 119,910 119,910 25,980 25,980 25,980 NC

Ground Truck Mount Boom/Broadcast Mixer/Loader 233,501 233,501 233,501 40,473 40,473 40,473 NC

Ground Truck Mount Boom/Broadcast Applicator/Mixer/Loader 64,611 64,611 64,611 13,999 13,999 13,999 NC 1 Receptor refers to a single worker doing all of the listed tasks.

2 Based on the assumption that a spill of concentrated liquid occurs to worker skin.

The ARI is based on inhalation exposure because based on the toxicity assessment, dermal exposure is not of concern. Values less than 1 represent a level of concern.

NC = Not calculated. Based on toxicity assessment, dermal exposure is not of concern, and long-term inhalation is not a concern for seasonal treatment.
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-97 January 2016

Final Programmatic EIS

TABLE 4-20

Fluroxypyr Aggregate Risk Indices, Routine Exposure Scenarios for Public Receptors, Short-term Exposure

Typical Application Rate Scenario ARIs Maximum Application Rate Scenario ARIs

AgDrift 

Scenario Aerial Aerial Aerial Aerial Ground Ground Aerial Aerial Aerial Aerial Ground Ground

Land Type1 Nonforested

Nonforested Forested Forested NA NA NonforestedNonforested Forested Forested NA NA

Equipment Plane Helicopter Plane Helicopter Low 

Boom

High 

Boom Plane Helicopter Plane Helicopter Low Boom

High 

Boom

Hiker/Hunter 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Berry Picker 

(Child) NC NC NC NC NC NC NC NC NC NC NC NC

Berry Picker 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Angler 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Residential 

(Child) NC NC NC NC NC NC NC NC NC NC NC NC

Residential 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

Native 

American 

(Child)

1,072 975 1,044 1,090 1,086 1,082 556 558 542 567 565 562

Native 

American 

(Adult)

2,082 1,895 2,029 2,118 2,110 2,102 1,080 1,084 1,053 1,101 1,097 1,093

Swimmer 

(Child) 1,724 1,569 1,680 1,754 1,747 1,740 894 898 872 912 909 905

Swimmer 

(Adult) 4,776 4,347 4,653 4,858 4,840 4,821 2,477 2,487 2,414 2,526 2,517 2,507

1 Land type is not applicable to ground scenarios.

ARI values less than 1 represent a level of concern. ARI does not include dietary or dermal exposure due to low toxicity. ARIs are based on swimming exposure.

NA = Not applicable.

NC = Not calculated. No dose-response values are available for dermal exposure or acute dietary exposure due to low toxicity.
BLM Vegetation Treatments Three New Herbicide

ENVIRONMENTAL CONSEQUENCES

4-98 January 2016

Final Programmatic EIS

TABLE 4-21

Fluroxypyr Aggregate Risk Indices for Accidental Exposure Scenarios for Public Receptors Based on Maximum Application Rates

Receptor

Dermal Contact Exposure Pathways Dietary Exposure Pathways

Direct 

Spray of 

Receptor

Dermal 

Contact 

with 

Foliage

Swimming1 Drinking Water Ingestion Fish Ingestion

Berry 

Ingestion Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Angler NC NC -- -- -- NC NC NC NC NC NC --

Berry Picker 

(Adult) NC NC -- -- -- NC NC NC -- -- -- NC

Berry Picker 

(Child) NC NC -- -- -- NC NC NC -- -- -- NC

Hiker/Hunter NC NC -- -- -- NC NC NC -- -- -- --

Native 

American 

(Adult)

NC NC 1,027 9 32 NC NC NC NC NC NC NC

Native 

American 

(Child)

NC NC 528 5 17 NC NC NC NC NC NC NC

Residential 

(Adult) NC NC -- -- -- -- -- -- -- -- -- --

Residential 

(Child) NC NC -- -- -- -- -- -- -- -- -- --

Swimmer 

(Adult) -- -- 2,355 21 74 -- -- -- -- -- -- --

Swimmer 

(Child) -- -- 850 8 27 -- -- -- -- -- -- --

1 Includes incidental ingestion for the swimmer. Incidental ingestion is not included for the Native American pathway because the drinking water pathway is included. 2 Assumes accidental spray of water body.

-- = Receptor not exposed via this pathway.

ARI values less than 1 represent a level of concern.

NC = Not calculated. No dose-response values available.
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-99 January 2016

Final Programmatic EIS

TABLE 4-22

Rimsulfuron Aggregate Risk Indices – Occupational Scenarios

Application 

Type

Application 

Vehicle

Application 

Method Receptor1

Typical Application Rate 

Scenario ARIs

Maximum Application Rate 

Scenario ARIs

Accidental Scenario ARIs 

(Short-term Dermal)

ShorttermIntermediatetermLongtermShorttermIntermediatetermLongterm

Mixed 

(Maximum) 

Solution2

Mixed 

(Typical)

Solution2

Aerial Plane Fixed Wing Pilot 87 87 NC 29 29 NC 0.089 0.12

Aerial Plane Fixed Wing Mixer/Loader 4 4 NC 1.5 1.5 NC 0.089 0.12

Aerial Helicopter Rotary Pilot 217 217 NC 7.2 7.2 NC 0.089 0.12

Aerial Helicopter Rotary Mixer/Loader 11 11 NC 3.7 3.7 NC 0.089 0.12

Ground Human Backpack Applicator/Mixer/Loader 94 94 NC 24 24 NC 0.089 0.12

Ground Human Horseback Applicator/Mixer/Loader 13 13 NC 7 7 NC 0.089 0.12

Ground ATV/UTV Spot Applicator 283 283 NC 79 79 NC 0.089 0.12

Ground ATV/UTV Spot Mixer/Loader 5,978 5,978 NC 1,494 1,494 NC 0.089 0.12

Ground ATV/UTV Spot Applicator/Mixer/Loader 262 262 NC 73 73 NC 0.089 0.12

Ground ATV/UTV Boom/Broadcast Applicator 6,459 6,459 NC 1,794 1,794 NC 0.089 0.12

Ground ATV/UTV Boom/Broadcast Mixer/Loader 1,868 1,868 NC 560 560 NC 0.089 0.12

Ground ATV/UTV Boom/Broadcast Applicator/Mixer/Loader 955 955 NC 265 265 NC 0.089 0.12

Ground Truck Mount Spot Applicator 155 155 NC 35 35 NC 0.089 0.12

Ground Truck Mount Spot Mixer/Loader 2,950 2,950 NC 560 560 NC 0.089 0.12

Ground Truck Mount Spot Applicator/Mixer/Loader 144 144 NC 33 33 NC 0.089 0.12

Ground Truck Mount Boom/Broadcast Applicator 3,445 3,445 NC 1,435 1,435 NC 0.089 0.12

Ground Truck Mount Boom/Broadcast Mixer/Loader 906 906 NC 332 332 NC 0.089 0.12

Ground Truck Mount Boom/Broadcast Applicator/Mixer/Loader 509 509 NC 212 212 NC 0.089 0.12 1 Receptor refers to a single worker doing all of the listed tasks.

2 Based on the assumption that a spill of mixed solution occurs to worker skin.

The ARI is based on inhalation exposure because based on the toxicity assessment, dermal exposure is not of concern. Values less than 1 represent a level of concern. Bolded cells indicate scenarios with ARI 

values less than 1.

NC = Not calculated. Based on toxicity assessment, dermal exposure is not of concern, and long-term inhalation is not a concern for seasonal treatment.
BLM Vegetation Treatments Three New Herbicide

ENVIRONMENTAL CONSEQUENCES

4-100 January 2016

Final Programmatic EIS

TABLE 4-23

Rimsulfuron Aggregate Risk Indices, Routine Exposure Scenarios for Public Receptors, Short-term Exposure

Typical Application Rate Scenario ARIs Maximum Application Rate Scenario ARIs

AgDrift 

Scenario Aerial Aerial Aerial Aerial Ground Ground Aerial Aerial Aerial Aerial Ground Ground

Land Type1 Nonforested

Nonforested Forested Forested NA NA NonforestedNonforested Forested Forested NA NA

Equipment Plane Helicopter Plane Helicopter Low 

Boom

High 

Boom Plane Helicopter Plane Helicopter Low Boom

High 

Boom

Hiker/Hunter 

(Adult) 252 305 59 713 2,139 1,426 178 225 47 535 1,426 328

Berry Picker 

(Child) 96 116 23 271 813 542 68 86 18 203 542 125

Berry Picker 

(Adult) 241 291 57 681 2,043 1,362 170 215 45 511 1,362 313

Angler 

(Adult) 252 305 59 713 2,139 1,426 178 225 47 535 1,426 328

Residential 

(Child) 79 95 19 222 667 445 56 70 15 167 445 102

Residential 

(Adult) 183 222 43 518 1,553 1,036 129 163 34 388 1,036 238

Native 

American 

(Child)

94 114 22 267 801 534 67 84 18 200 534 123

Native 

American 

(Adult)

236 285 56 667 2,000 1,333 167 210 44 500 1,333 307

Swimmer 

(Child) NC NC NC NC NC NC NC NC NC NC NC NC

Swimmer 

(Adult) NC NC NC NC NC NC NC NC NC NC NC NC

1 Land type is not applicable to ground scenarios.

ARI values less than 1 represent a level of concern. ARI does not include dietary or dermal exposure due to low toxicity. ARIs are based on swimming exposure.

NA = Not applicable.

NC = Not calculated. No dose-response values are available for incidental oral pathway due to use pattern.
ENVIRONMENTAL CONSEQUENCES

BLM Vegetation Treatments Three New Herbicide 4-101 January 2016

Final Programmatic EIS

TABLE 4-24

Rimsulfuron Aggregate Risk Indices for Accidental Exposure Scenarios for Public Receptors Based on Maximum Application Rates

Receptor

Dermal Contact Exposure Pathways Dietary Exposure Pathways

Direct 

Spray of 

Receptor

Dermal 

Contact 

with 

Foliage

Swimming1 Drinking Water Ingestion Fish Ingestion

Berry 

Ingestion Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Spray of 

Water 

Body2

Helicopter 

Spill

Truck 

Spill

Angler 12 104 -- -- -- NC NC NC NC NC NC --

Berry Picker 

(Adult) 7 61 -- -- -- NC NC NC -- -- -- NC

Berry Picker 

(Child) 3 35 -- -- -- NC NC NC -- -- -- NC

Hiker/Hunter 7 104 -- -- -- NC NC NC -- -- -- --

Native 

American 

(Adult)

7 51 NC NC NC NC NC NC NC NC NC NC

Native 

American 

(Child)

3 29 NC NC NC NC NC NC NC NC NC NC

Residential 

(Adult) 7 15 -- -- -- -- -- -- -- -- -- --

Residential 

(Child) 3 9 -- -- -- -- -- -- -- -- -- --

Swimmer 

(Adult) -- -- NC NC NC -- -- -- -- -- -- --

Swimmer 

(Child) -- -- NC NC NC -- -- -- -- -- -- --

1 Includes incidental ingestion for the swimmer. Incidental ingestion is not included for the Native American pathway because the drinking water pathway is included. 2 Assumes accidental spray of water body

-- = Receptor not exposed via this pathway.

ARI values less than 1 represent a level of concern.

NC = Not calculated. No dose-response values available.
ENVIRONMENTAL CONSEQUENCES

Rimsulfuron

Based on the hazard identification presented in the 

HHRA, rimsulfuron has low acute toxicity orally, by 

dermal exposure, and by inhalation, but is a moderate 

eye irritant. It is not a dermal sensitizer. Based on 

subchronic and chronic toxicity studies, long-term 

exposures to rimsulfuron can cause a variety of adverse 

health effects targeting multiple organs. No 

developmental toxicity has been observed at high doses, 

and there is no evidence that rimsulfuron is an 

endocrine disruptor. Rimsulfuron is classified as “Not 

Likely a Human Carcinogen” (USEPA 2011).

As shown in Table 4-14, there is no risk to occupational 

receptors under routine exposure scenarios, but low to 

moderate risk under accidental exposure scenarios. 

These scenarios assume that a mixed solution of 

rimsulfuron is spilled directly onto an occupational 

receptor, and that use of proper personal protective

equipment (PPE) would not prevent dermal exposure. 

Therefore, this risk represents an unlikely scenario that 

could be avoided through proper handling of the 

herbicide, following all SOPs and label instructions, and 

use of appropriate personal protective equipment. Table 

4-22 shows the detailed HHRA results for occupational 

exposure scenarios.

As summarized in Table 4-15, and shown in more detail 

in Tables 4-23 and 4-24, there is no risk to public 

receptors under routine or accidental exposure 

pathways. All of the calculated ARIs are above 1. The 

lowest ARIs were for accidental direct spray scenarios 

involving children. These results indicate that 

rimsulfuron does not present an unacceptable risk to 

public receptors, even under worst-case accidental 

exposure scenarios.

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)

Under this alternative, the BLM would continue to 

implement herbicide treatments using the 18 herbicides 

previously approved in the 2007 PEIS. The total area 

treated with herbicides would be the similar to the 

action alternatives, with differences in risk pertaining to 

the relative amount of different herbicides used, and 

their associated level of risk. Risks to humans from the 

use of the previously approved chemicals vary, ranging 

from no risk to high risk to occupational and public 

receptors, depending on the exposure scenario. 

Herbicides with the greatest amount of associated risk 

include 2,4-D, bromacil, diquat, fluridone, hexazinone, 

tebuthiuron, and triclopyr (see the 2007 PEIS for more 

information [USDOI BLM 2007a:4-182 to 4-193]). Of 

these, the active ingredients with the greatest projected 

usage under this alternative include triclopyr, 

tebuthiuron, and 2,4-D. Human health risks from these 

chemicals would continue to be minimized by following 

all label instructions, and SOPs to prevent accidental 

exposures and protect human health. Additionally, the 

mitigation measures specified in the ROD for the 2007

PEIS (USDOI BLM 2007b:Table 2), such as using the 

typical application rate of these chemicals, where 

feasible, would help to further minimize risks to 

occupational and public receptors.

Under this alternative, ongoing treatment programs with 

the currently approved herbicides would continue to 

provide benefits to human health by reducing the 

occurrence of noxious weeds and other invasive 

vegetation. Additionally, ongoing treatment of species 

that increase the risk of wildfire, such as cheatgrass, 

would reduce the risk of wildfire and the associated 

public health and safety risks. 

Alternative B – Allow for Use of Three New 

Herbicides in 17 Western States (Preferred 

Alternative)

Under the Preferred Alternative, general risks associated 

with herbicide treatments would be much the same as 

under the No Action Alternative, as roughly the same 

acreage would be treated with herbicides. The ability to 

use aminopyralid, fluroxypyr, and rimsulfuron for

vegetation treatments could result in a slight change in 

risk in certain treatment areas, as the relative amount of 

herbicides would change. All three of the new 

herbicides have no to very low risk to human health 

(with an unacceptable risk only predicted for one 

accidental exposure scenario involving rimsulfuron). 

However, the three herbicides with the most substantial 

predicted decrease in usage under this alternative—

imazapic, glyphosate, and picloram—also have no to 

low human health risks. Use of the herbicides with 

higher risk would likely remain at or near current levels. 

Therefore, there would be little difference in risks to 

human health and safety between the Preferred 

Alternative and the No Action Alternative.

Introduction of the three new herbicides may allow the 

BLM to be more efficient at controlling certain target 

BLM Vegetation Treatments Using Herbicides 4-102 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

noxious weeds and other invasive vegetation, which 

would have an associated health benefit. Use of 

rimsulfuron may allow for better control of cheatgrass, 

and an associated reduction in wildfire risk. These 

beneficial effects are expected to be minor.

Alternative C – No Aerial Application of New 

Herbicides

Under Alternative C, human health risks associated with 

herbicide treatments would be similar to those under the 

Preferred Alternative and the No Action Alternative. 

The new herbicides would not be applied aerially, 

eliminating certain exposure pathways for occupational 

and public receptors. According to the HHRA, ARIs for 

aerial application scenarios are generally lower than 

those for ground-based methods, indicating greater 

overall risk. However, there are no differences in risk 

categories between aerial and ground application, as 

shown in Tables 4-14 and 4-15. Additionally, restriction 

of aerial applications of the new chemicals would not 

reduce aerial spraying of herbicides, as different active 

ingredients would be used where aerial spraying is 

needed. For instance, to control cheatgrass, the currently 

approved imazapic would be used in aerial applications 

where rimsulfuron would have otherwise been used. 

Furthermore, the maximum total area treated using 

herbicides would not differ from that under the other 

alternatives.

The relative use of the different chemicals would be 

slightly different than under the No Action and 

Preferred Alternatives, with use of the three new 

herbicides being lower than under the Preferred 

Alternative, and use of glyphosate, imazapic, and 

picloram falling between the levels estimated for the No 

Action and Preferred Alternatives. The relative amounts 

of the other herbicides used would be roughly the same 

as under the other alternatives. As the active ingredients 

with usage levels that would change are all generally no 

to low risk herbicides, overall risk from herbicide use 

would be similar to that under the other alternatives.

Being unable to aerially apply the new herbicides could 

have an impact on the effectiveness of herbicide 

treatments to some degree, although the currently 

approved herbicides could still be used to control the 

target species via aerial methods. While less benefit to 

human health from control of noxious weeds and 

wildfire fuels is possible, the differences are expected to 

be minor, relative to the Preferred Alternative. 

Alternative D – No Use of New Acetolactate 

Synthase-inhibiting Active Ingredients (No 

Rimsulfuron)

Under this alternative rimsulfuron would not be used, 

and as a result use of glyphosate and imazapic would be 

higher than under the other action alternatives, similar 

to the No Action Alternative. However, since the 

differences in relative projected use involve all no- to 

low-risk active ingredients, overall risks to human 

health associated with herbicide treatments would be 

similar to those under the other alternatives. Since the 

total area treated using herbicides is expected to be the 

same under all the alternatives, there would be little to 

no difference in human health risk associated with 

potential exposure to herbicides.

Under this alternative, the BLM would not be able to 

use rimsulfuron to control cheatgrass and other winter 

annual grasses. As there is evidence that rimsulfuron 

may be more effective than imazapic and glyphosate in 

certain situations, the human health benefits associated 

with cheatgrass removal could be slightly less under this 

alternative than under the Preferred Alternative. It is 

expected that this difference would be minor.

Mitigation

As discussed previously, herbicide treatments involving 

the new chemicals would continue to follow all of the 

applicable SOPs for herbicide treatments listed in the 

2007 PEIS and earlier in this resource section. The 

ROD (USDOI BLM 2007b:Table 2) lists additional 

mitigation measures for herbicide applications that 

would also continue to be followed, although these 

measures are specific to currently approved herbicides 

and would not apply to the new herbicides, unless used 

in a mixture with one of the other active ingredients.

Given the safety of aminopyralid, fluroxypyr, and 

rimsulfuron to humans, no additional mitigation 

measures are recommended for herbicide treatments 

with these active ingredients. 

Cumulative Effects Analysis

Under NEPA and its implementing guidelines, 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, is required. 

BLM Vegetation Treatments Using Herbicides 4-103 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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 

with aminopyralid, fluroxypyr, and rimsulfuron 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. 

The 2007 PEIS provides a thorough cumulative effects 

analysis for the BLM’s herbicide treatment program 

(USDOI BLM 2007a:4-197 to 4-246). Since the three 

new herbicides would be added to an existing program, 

with no change in goals or acres or areas treated, much 

of the 2007 analysis is inclusive of their use and does 

not warrant repetition here. The analysis presented here 

provides a general summary of the 2007 analysis, with 

updated information provided where available. 

Additionally, the analysis will include a discussion of 

the cumulative effects associated with adding the three 

new herbicide active ingredients to the BLM’s list of 

approved active ingredients.

Structure of the Cumulative Effects 

Analysis

The structure of the cumulative effects analysis is 

described in the 2007 PEIS (USDOI BLM 2007a:4-197 

to 4-201). 

Class of Actions to be Analyzed – Large, regional scale 

trends and issues that require integrated management 

across broad landscapes, and regional-scale trends and 

changes in the social and economic needs of people.

Appropriate Temporal Domain – The analysis period is 

from 1930 through 2057. This is the date that was 

identified in the 2007 PEIS. As the three new active 

ingredients are being incorporated into the treatment 

programs identified in the 2007 PEIS, the analysis 

period remains the same. 

Appropriate Spatial Domain – The analysis area 

includes public lands in 17 western states, as well as 

adjacent and nearby non-federal lands, depending on the 

resource area. 

Set of Receptors to be Assessed – The physical, 

biological, and human systems discussed in Chapter 3 

(Affected Environment). 

Magnitude of Effects and Whether They are 

Accumulating – Consider additive, countervailing, and 

synergistic effects, using quantitative (where possible) 

and qualitative analysis.

Resource Protection Measures and 

Other Information Considered in the 

Cumulative Effects Analysis

The resource protection measures considered in the 

2007 cumulative effects analysis (USDOI BLM 

2007a:4-201 to 4-202) are considered in the current 

analysis. They include SOPs, monitoring measures, and 

mitigation provided in the 2007 PEIS and PER (USDOI 

BLM 2007a:Chapter 2; USDOI BLM 2007c:Chapter 2). 

Additionally, they include all new mitigation measures 

that have been developed by the BLM for use of the 

three new herbicides, which can be found in Chapter 2 

of this document.

Additionally, federal, state, local, and tribal resource 

management and monitoring programs that pertain to 

protection of environmental resources and restoration of 

impaired resources are also considered in the 

cumulative effects analysis. Regulatory programs exist 

for air quality, water quality, wetlands, essential fish 

habitat, threatened and endangered species, and 

environmental justice.

Other pertinent information considered in the 

cumulative effects analysis includes the following:

• Mitigation and SOPs identified in 2007 PEIS 

would be more stringent than those required by 

the USEPA.

• The BLM would comply with existing and 

future regulations, including the FLPMA.

BLM Vegetation Treatments Using Herbicides 4-104 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

• A site-specific NEPA analysis would be 

conducted prior to implementing vegetation 

treatments on public lands.

Analysis of Cumulative Effects by 

Resources

Air Quality

Past Effects and Their Accumulation

Past effects to air quality, and their accumulation, are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-202 

to 203). They include emissions associated with wildfire 

and prescribed fire, vehicle exhaust, commercial and 

industrial land uses, and residential heating, among 

other sources.

Since the 2007 PEIS was released in 2007, the USDOI 

has begun to track GHG emissions, and in 2012 

developed goals for reducing GHG emissions (USDOI 

BLM 2014f). Since 2008, the USDOI has reduced direct

(vehicle) and certain indirect (e.g., purchased electricity) 

GHG emissions by 11.6 percent, and reduced other 

indirect GHG emissions (e.g., airline business travel) by 

7.5 percent.

Nationwide, air quality has continued to improve since 

over the last few decades. Between 1990 and 2000, air 

pollution decreased for PM10 (38 percent), lead (83 

percent), NO2 (45 percent), CO (73 percent), and SO2

(75 percent). PM2.5 concentrations decreased between 

2001 and 2010, and ozone concentrations decreased 

between 2002 and 2010. Many toxic air pollutants also 

declined. Pollutants of primary concern continue to be 

PM and ozone. Greenhouse gas emissions continue to 

increase in the U.S.; they have increased by 7 percent 

since 1990 (USEPA 2012f).

Based on data from the National Interagency Fire 

Center, the annual number of wildfires between 1987 

and 2012 has remained relatively steady, but the acreage 

burned and average size of fires has increased (EcoWest 

2014). Therefore, wildfires continue to contribute to air 

pollution at increasing levels, although there is quite a 

bit of variability from year to year.

Future Effects and Their Accumulation

Future effects to air quality, and their accumulation,

are discussed in the 2007 PEIS (USDOI BLM 

2007a:4-202 to 203). The discussion focuses on firerelated impacts to air quality, which are a main source 

of concern in the area affected by the BLM’s 

vegetation treatments. Sources of air quality 

pollutants discussed in the preceding section, such as 

wildfire and vehicle emissions, will continue to 

contribute to cumulative air quality emissions. 

Contributions of GHG emissions will also be 

cumulative, and will potentially have an impact at a 

global scale by contributing to climate change. It is 

expected that in the future, air quality overall will 

continue to improve, although emissions associated 

with wildfire may continue to increase. Better vehicle 

emission standards, other regulations, and efforts by 

the USEPA, local air agencies, and other agencies to 

reduce air quality emissions will all contribute to this 

improvement in air quality. 

Based on current trends, it is expected that GHG 

emissions will continue to increase in the future, and 

will continue to contribute to climate change. 

Increased drought conditions in the western U.S. 

could, in turn, contribute to an increase in wildfire, 

which would contribute additional air quality 

pollutants to the atmosphere.

Efforts by the BLM, Forest Service, and other 

agencies to reduce the risk of wildfire on lands that 

they manage will help offset some of the impacts to 

air quality associated with wildfires. These programs 

are likely to be ongoing during the duration of the 

period of analysis covered by this PEIS. 

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be the similar under all of the 

alternatives, the contribution to air quality in terms of 

pollutants generated during treatments would also be the 

similar under all the alternatives. Air quality emissions 

are directly correlated with treatment acreage, as they 

are correlated to number of vehicle miles driven. The 

geographic location of air quality impacts would also be 

the similar under all the alternatives. Air quality 

emissions associated with treatment programs would be 

cumulative to other releases of criteria pollutants and 

GHGs within the geographic areas affected by 

treatments.

Long-term benefits to air quality from a reduction in 

wildfire risk would also be similar under all the 

alternatives.

BLM Vegetation Treatments Using Herbicides 4-105 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Soil Resources

Past Effects and Their Accumulation

Past effects to soil resources and their accumulation are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-

205). They are predominantly associated with natural 

resource extraction, renewable energy development, 

grazing, road construction, timber harvesting, OHV and 

other recreation use, agriculture, development, wildland 

fire, and natural disturbances. 

Future Effects and Their Accumulation

Future effects to soil resources and their accumulation 

are discussed in the 2007 PEIS (USDOI BLM 2007a:4-

205 to 4-206). The factors contributing to past effects to 

soil, as described in the previous paragraph, are ongoing 

in the West, and will continue to impact soil resources. 

Additionally, vegetation treatments by the BLM will 

contribute to short-term loss of soil functions, process, 

and productivity on nearly all treated land. Adverse

effects to soil will be offset by watershed-level 

restoration treatments designed and implemented by the 

BLM and other federal agencies with large landholdings 

in the West. Numerous policies, programs, and 

initiatives have been proposed to restore soil 

productivity and improve the health of ecosystems by 

the BLM and other federal, state, and local land 

management entities. In addition, conservation 

programs and BMPs to reduce soil loss in agricultural 

areas have been developed and implemented during the 

past several decades. All efforts to reduce the spread of 

invasive vegetation, and to reduce the risk of wildfire,

are expected to help maintain soil productivity and 

function. 

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

the contribution of the various alternatives to soil 

impacts in terms of losses in soil function and 

productivity would also be similar. Countervailing 

effects associated with long-term improvement in soil 

function and productivity would also be similar under 

all the alternatives.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

soil resources would be 18. Under Alternatives B and C, 

three additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

It is expected that impacts associated with all of the 

herbicide active ingredients would be short-lived, as 

herbicides and their breakdown products would degrade 

over time. However, the ways in which these chemicals 

might interact and the potential for synergistic effects 

from use of multiple active ingredients are largely 

unknown. The action alternatives would result in a 

cumulative increase in the number of herbicide active 

ingredients with the potential to impact soil and soil 

organisms. 

Water Resources and Quality

Past Effects and Their Accumulation

Past effects to water resources and their accumulation 

are discussed in the 2007 PEIS (USDOI BLM 2007a:4-

207 to 4-208). They are predominantly associated with 

mining activities, exploration and development of oil 

resources, agriculture (including use of pesticides), 

industry, and other human activities.

Based on the most recent (2004) National Water Quality 

Inventory Report to Congress (USEPA 2009a), an 

assessment of streams in the western U.S. determined 

that the most prevalent stressors were nitrogen, 

phosphorus, riparian disturbance, and streambed 

sediments. 

Based on the most recent Alaska Water Quality 

Assessment Report (USEPA 2010b), the primary causes 

of impairment are turbidity, fecal coliform, and 

sedimentation/siltation, with resource extraction and 

urban runoff/stormwater as the primary sources of 

impairment.

Groundwater and surface water quality in the West have 

been impacted by pollutants associated with agriculture 

and other activities. Additionally, water quantity has 

been impacted in many areas of the West, largely as a 

result of ongoing population growth and irrigation. As 

documented by the NAWQA, pesticides or their 

degradates are prevalent in streams, and have been

detected in more than half of the shallow wells sampled 

in agricultural and urban areas, and in 33 percent of the 

deeper wells that tap major aquifers (USGS 2006). 

About 1 percent of public-supply wells sampled by 

NAWQA had a pesticide concentration greater than a 

human health benchmark. 

According to a recent study documenting trends in 

pesticide concentrations in U.S. streams and rivers, the 

proportion of mixed land use streams with pesticides 

exceeding aquatic life benchmarks has generally stayed 

the same over the last 20 years, with concentrations of 

BLM Vegetation Treatments Using Herbicides 4-106 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

individual pesticides varying in response to shifts in use 

patterns (Stone et al. 2014).

Future Effects and Their Accumulation

Future effects to water resources and their accumulation 

are discussed in the 2007 PEIS (USDOI BLM 2007a:4-

208).

While it is difficult to predict the extent and magnitude 

of future effects to water resources and quality, it is 

assumed that activities that contribute to water quality 

pollution and depletion will continue in the western 

states. At the same time, efforts to improve water 

quality are ongoing, including goals by the BLM for 

percent of water bodies meeting State Water Quality 

Standards. Target goals are raised every year. The BLM 

and other land management agencies also continue 

programs to restore degraded wetland/riparian areas, 

which includes vegetation management programs.

Programs that will be implemented to meet restoration 

goals are the same as those that were discussed in the 

2007 PEIS.

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

the impacts to water resources in terms of degradation 

of water quality associated with treatments also would 

be similar under all the alternatives. Countervailing 

effects associated with long-term improvement in 

function of wetlands, riparian areas, streams, and other 

water bodies would also be similar under all the 

alternatives.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

water resources would be 18. Under Alternatives B and 

C, three additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

It is expected that impacts associated with all of the 

herbicide active ingredients would be short-lived, as 

herbicides and their breakdown products would degrade 

over time. However, the ways in which these chemicals 

might interact and the potential for synergistic effects 

from use of multiple active ingredients are largely 

unknown. Additionally, it is unknown the degree to 

which these degradates might persist in groundwater. 

The action alternatives would result in a cumulative 

increase in the number of herbicide active ingredients 

with the potential to impact water resources and result 

in groundwater contamination.

Wetland and Riparian Areas

Past Effects and Their Accumulation

Past effects to wetland and riparian areas and their 

accumulation are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-209 to 4-210). They are predominantly 

associated with natural resource extraction, recreation, 

dams and diversions, road construction, agriculture, 

urbanization, and fire exclusion. Invasive plants and 

catastrophic wildfires degrade wetland and riparian 

function. Wetland losses in the lower 48 states have 

continued to decline, although the rate has been slowed 

by reestablishment of wetlands. Estimated net wetland 

loss for the lower 48 states from 2004 to 2009 was 

62,300 acres (USFWS 2011). However, most of these 

wetlands were in the southeastern United States.

On BLM lands in the lower 48 states, 44 percent of 

wetlands surveyed are not functioning properly or are 

functioning at risk (USDOI BLM 2012a). This 

percentage continues to increase, despite efforts by the 

BLM to improve proper functioning condition. Only 16 

percent of riparian areas in the lower 48 states are nonfunctional or functioning at risk, and the trend on BLM 

lands is one of improvement in riparian condition. In 

Alaska, impacts have been less, and nearly all wetlands 

and riparian areas are in properly functioning condition.

Future Effects and Their Accumulation

Future effects to wetlands and riparian areas and their 

accumulation are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-210).

Factors that contribute to degradation of wetlands and 

riparian areas, as described in the previous section, 

continue to varying degrees in the West. Climate change 

may also contribute to impacts, particularly as a result 

of increased temperatures and extended drought periods. 

Ongoing efforts to protect wetlands and riparian areas 

have reduced the level of impact of natural and human 

factors that degrade these habitats. Additionally, 

vegetation treatment programs by the BLM and Forest 

Service, along with restoration efforts by other agencies, 

private landowners, and other entities, continue to 

improve the condition of degraded wetland and riparian 

habitats. While it is difficult to predict the extent and 

magnitude of future effects to water resources and 

quality, it is assumed that activities that contribute to 

water quality pollution and depletion will continue in 

the western states. At the same time, efforts to improve 

water quality are ongoing, including goals by the BLM 

for percent of water bodies meeting State Water Quality 

BLM Vegetation Treatments Using Herbicides 4-107 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Standards, which increase each year. The BLM and 

other land management agencies also continue 

programs to restore degraded wetland/riparian areas, 

which includes vegetation treatment programs. Future 

treatment programs that will be implemented to meet 

restoration goals are the same as those that were 

discussed in the 2007 PEIS.

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

potential impacts to wetlands and riparian areas 

associated with herbicide treatments would also be 

similar under all the alternatives. Some herbicides 

would be released into wetland and riparian areas, and 

removal of vegetation could have short-term impacts to 

functions. Countervailing effects associated with longterm improvement in function of wetlands, riparian 

areas, streams, and other water bodies would also be 

similar under all the alternatives.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

water resources would be 18. Under Alternatives B and 

C, three additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

It is expected that impacts associated with all of the 

herbicide active ingredients would be short-lived, as 

herbicides and their breakdown products would degrade 

over time. However, the ways in which these chemicals 

might interact and the potential for synergistic effects 

from use of multiple active ingredients are largely 

unknown. Additionally, it is unknown the degree to 

which these degradates might persist in groundwater or 

wetland or riparian soils. The action alternatives would 

result in a cumulative increase in the number of 

herbicide active ingredients with the potential to impact 

wetland and riparian habitats and the species found in 

them.

Vegetation

Past Effects and Their Accumulation

Past effects to vegetation (including native plant 

communities and special status plant species), and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-211 to 4-212). They are predominantly 

associated with exclusion of fire and alteration of 

natural disturbance regimes, timber harvest, reseeding 

and planting programs, and grazing. Human activities 

have altered native plant communities, and have led to 

the introduction and spread of invasive species. 

Future Effects and Their Accumulation

Future effects to vegetation, and their accumulation, are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-212 

to 4-213). Many of the same human activities that have 

altered native plant communities in the past will 

continue to do so in the future. Populations of invasive 

species will continue to spread, and altered disturbance 

regimes will continue to cause large wildfires that 

further alter vegetation in the western U.S. Treatments 

by the BLM, Forest Service, and other entities to 

remove hazardous fuels and control invasive species 

will help offset these adverse effects, although multiple 

treatments followed by restoration would be necessary 

to recover native communities and restore disturbance 

regimes in targeted areas. 

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

the contribution to vegetation impacts in terms of 

departure from native conditions and disturbance 

regimes would also be similar under all the alternatives.

Countervailing effects associated with long-term 

improvement in plant communities and reduction in fire 

risk would also be similar under all the alternatives.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

vegetation would be 18. Under Alternatives B and C, 

three additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

Under all alternatives, herbicides would be available 

that would allow the BLM to meet their treatment goals 

to restore native communities. The action alternatives 

would allow the BLM additional options for treating 

invasive species that could improve the effectiveness of 

treatment programs in certain circumstances. In all 

cases, herbicide treatments could be used in concert 

with other vegetation treatment methods. Additionally, 

aminopyralid and fluroxypyr would be tank mixed with 

other active ingredients, which could result in additive 

or even synergistic effects to non-target plants.

Fish and Other Aquatic Organisms

Past Effects and Their Accumulation

Past effects to fish and other aquatic resources

(including special status aquatic species), and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-214 to 4-215). They are predominantly 

associated with natural resource extraction; recreation; 

BLM Vegetation Treatments Using Herbicides 4-108 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

fire exclusion; construction of roads, dams, and 

hydropower facilities; agriculture; and urbanization. In 

Alaska, oil and gas development, and subsistence and 

recreational fishing, have been the primary factors 

affecting fish and aquatic resources. 

The spread of invasive plant species and increase in 

catastrophic wildfires in the western U.S. have also 

been a factor in the degradation of water bodies that 

provide habitat for fish and other aquatic organisms.

The BLM, other federal and state agencies, private 

landowners, and businesses have implemented pest and 

invasive plant control efforts that have resulted in the 

application of thousands of tons of herbicides and other 

pesticides to the environment. Some of these pesticides 

break down relatively quickly in the environment or are 

not harmful to aquatic organisms at typical application 

rates. However, some are harmful to aquatic organisms 

and may be persistent in the environment.

Future Effects and Their Accumulation

Future effects to fish and other aquatic resources, and 

their accumulation, are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-215). As discussed under the 

cumulative effects discussions for water resources, 

wetlands, and riparian areas, it is assumed that activities 

that contribute to the degradation and loss of these 

habitats will continue to occur in the western states, 

although they will be offset to some degree by 

protective regulations and restoration efforts, driven by 

goals to improve water quality and regain the proper 

functioning condition of riparian areas. Additionally, 

efforts to remove dams and other blockages to fish 

passage will continue to benefit fish populations by 

expanding their ranges. 

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

the impacts to habitats that support fish and aquatic 

resources would also be similar under all the 

alternatives. Countervailing effects associated with 

long-term improvement in function of aquatic habitats 

would also be similar under all the alternatives.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

water resources would be 18. Under Alternatives B and 

C, three additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

The potential toxicological effects to fish and aquatic 

invertebrates associated with the active ingredients vary. 

By allowing the BLM the option of using additional 

active ingredients, the action alternatives would result in 

a cumulative increase in the number of active 

ingredients released to the environment that could enter 

aquatic habitats. As the three herbicides have a very low 

risk to aquatic species, a cumulative effect of adding 

these active ingredients could be a reduction in overall

risk to aquatic species associated with herbicide use. 

It is expected that impacts associated with all of the 

herbicide active ingredients would be short-lived, as 

herbicides and their breakdown products would degrade 

over time. However, the ways in which these chemicals 

might interact and the potential for synergistic effects 

from use of multiple active ingredients are largely 

unknown. Additionally, it is unknown the degree to 

which these degradates might persist in aquatic habitats. 

Herbicides and other pesticides may interact with a 

wide range of pollutants and various other chemical and 

non-chemical factors, in ways that are poorly 

understood, to result in adverse effects to aquatic 

populations, species, communities, and ecosystems 

(Scholz et al. 2012).

Wildlife Resources

Past Effects and Their Accumulation

Past effects to wildlife and their accumulation are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-216 

to 4-220). The discussion considers habitat loss, 

modification, and fragmentation, and wildlife health. 

Habitat loss has occurred as a result of conversion to 

agriculture, pastureland, and residential, commercial 

industrial, and other development. On lands that have 

not been converted to other uses, including most of the 

lands managed by the BLM, habitat modification has 

reduced their value to wildlife. The primary factors 

contributing to habitat modification in the West include 

grazing by domestic livestock and wild horses and 

burros, timber management, fire suppression, and 

invasion by invasive plants and other unwanted 

vegetation. Mature forests, sagebrush habitats, and 

grasslands have been most affected. Causes of wildlife 

death, injury, sickness, and disturbance include hunting, 

collisions with vehicles and structures, wildland and 

prescribed fires, recreation, and pesticide use.

BLM Vegetation Treatments Using Herbicides 4-109 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Future Effects and Their Accumulation

Future effects to wildlife, and their accumulation, are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-212 

to 4-213). Many of the causes of impacts to wildlife 

discussed in the preceding section will continue to have 

effects on wildlife. Loss, modification, and 

fragmentation of habitat will likely continue, increasing 

the likelihood of local extirpations of wildlife

populations and loss of species diversity. Actions to 

protect sensitive species and their habitats, restore 

native plant communities and disturbance regimes, 

control the spread of invasive species, and reduce the 

risk of catastrophic wildfire are all expected to help 

offset some of the adverse impacts to wildlife and 

wildlife habitat.

Use of herbicides and other pesticides will continue and 

likely increase, and wildlife will continue to be at risk 

for exposure to these chemicals. Identifying and 

restricting use of active ingredients with the greatest 

toxicological risks to wildlife in favor of active 

ingredients with lower risks would help reduce 

cumulative effects associated with exposure to 

pesticides.

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

the impacts to wildlife habitat would also be similar

under all the alternatives. Countervailing long-term 

effects associated with restoration of native plant 

communities and disturbance regimes would also be 

similar under all the alternatives.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

wildlife would be 18. Under Alternatives B and C, three 

additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

The potential toxicological effects to wildlife associated 

with the active ingredients vary. By allowing the BLM 

the flexibility to use additional herbicides, the action 

alternatives would result in the release of a larger

number of active ingredients. As the three herbicides 

have a very low risk to wildlife, a cumulative effect of 

adding these active ingredients could be a reduction in 

overall risk to wildlife associated with herbicide use, as 

use of herbicides with a greater risk to wildlife would 

potentially be less. 

It is expected that impacts associated with all of the 

herbicide active ingredients would be short-lived, as 

herbicides and their breakdown products would degrade 

over time. The ways in which aminopyralid, fluroxypyr, 

and rimsulfuron might interact with other active 

ingredients and the potential for synergistic effects are 

largely unknown. Additionally, the toxicity of 

breakdown products to wildlife is largely unknown.

Livestock

Past Effects and Their Accumulation

Past effects to livestock, and their accumulation, are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-

222). They are predominantly associated with a 

decrease in the ability of public lands to support 

livestock grazing, which has occurred as a result of 

changes in fire regimes and the spread of noxious 

weeds. Past livestock grazing has contributed to these 

adverse effects, as have mineral extraction, recreation, 

and other activities.

Future Effects and Their Accumulation

Future effects to livestock, and their accumulation, are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-222

to 4-223). Many of the factors discussed in the 

preceding paragraph are ongoing and will continue to 

impact the quality of rangelands utilized by livestock. 

However, these effects will be minimized or offset by 

ongoing management programs designed to restore 

ecosystem processes and maintain livestock populations 

in balance with the health of rangelands. Treatments 

that control noxious rangeland weeds and reduce the 

risk of fire will also help to improve rangeland quality.

Contribution of Treatment Alternatives to 

Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be the same under all of the 

alternatives, there would be no difference in the amount 

of rangeland targeted by herbicide treatments under any 

of the alternatives. Use of herbicides in rangelands 

could have some short-term adverse effects by 

removing large areas of vegetation and non-target 

species used by livestock as forage. However, over the 

long term it would have countervailing effects of 

improving the quality of rangeland forage and 

controlling noxious weeds that are unpalatable or toxic 

to livestock.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

livestock would be 18. Under Alternatives B and C, 

BLM Vegetation Treatments Using Herbicides 4-110 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

three additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

The potential toxicological effects to livestock 

associated with herbicide active ingredients vary. 

However, the three new herbicides are not associated 

with toxicological risks to livestock, and their use may 

result in a reduction in the use of active ingredients with 

greater toxicological risks. Therefore, a cumulative 

effect of adding these active ingredients could be a 

reduction in overall risk to livestock associated with 

herbicide use.

Wild Horses and Burros

Past Effects and Their Accumulation

Past effects to wild horses and burros, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-223 to 4-225). They include a large 

reduction in the wild horse and burro populations in the 

1930s and 1940s as a result of capture and removal, 

which was halted with the passage of the Wild FreeRoaming Horses and Burros Act of 1971. Since then, 

the BLM has attempted to maintain populations at 

levels that can be supported by the available resources, 

but populations continue to be well above that level. 

Activities that reduce the quantity or value of available 

resources have had an adverse effect on wild horses and 

burros. These include development, grazing, and 

building of fences and other structures that impede herd 

movements.

The maximum AML is currently 26,684, which is lower 

than it was when the 2007 PEIS was completed. 

However, the total number of wild horses and burros on 

public lands has increased since then to 49,209, which is 

over 22,500 animals more than public rangeland can 

sustain (USDOI BLM 2014a).

Future Effects and Their Accumulation

Future effects to wild horses and burros, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-225). The BLM will continue 

management efforts to keep wild horse and burro 

populations at AMLs in balance with the condition of 

rangelands, which will require continued removal and 

adoption of animals, as well as measures to control 

reproduction. Additionally, the factors discussed in the 

preceding section will continue to impact the quality of 

rangelands and impede movement by wild horses and 

burros. Treatments that control noxious rangeland 

weeds and reduce the risk of fire will also help to 

improve rangeland quality and its ability to support wild 

horse and burro populations.

Contribution of Alternatives to Cumulative Effects

The acreage of rangelands treated with herbicides would 

be similar under all of the alternatives. Use of herbicides 

in rangelands could have some short-term adverse 

effects by removing large areas of vegetation and nontarget species used by wild horses and burros as forage. 

However, over the long term it would have 

countervailing effects of improving the quality of 

rangeland forage and controlling noxious weeds that are 

unpalatable or toxic to wild horses and burros.

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

wild horses and burros would be 18. Under Alternatives 

B and C, three additional herbicides would be used, and 

under Alternative D, two additional herbicides would be 

used. The potential toxicological effects to wild horses 

and burros associated with herbicide active ingredients 

vary. However, the three new herbicides are not

associated with toxicological risks to large mammals, 

and their use may result in a reduced need for active 

ingredients with greater toxicological risks. Therefore, a 

cumulative effect of adding the three new active 

ingredients could be a reduction in overall risk to wild 

horses and burros associated with herbicide use.

Paleontological and Cultural Resources

Past Effects and Their Accumulation

Past effects to paleontological and cultural resources, 

and their accumulation, are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-223 to 4-225). Past exploration 

and development in the western U.S. has led to legal 

and illegal collection of paleontological resources and 

inadvertent damage. Many cultural resources have been 

lost or damaged by exposure to the elements or by 

collection or destruction of cultural sites. These losses 

are permanent, but have been slowed by legislation 

designed to protect these resources from damage and 

removal.

Future Effects and Their Accumulation

Future effects to paleontological and cultural resources, 

and their accumulation, are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-226 to 4-228). While the 

widespread loss and damage of paleontological and 

cultural resources has been slowed, ground-disturbing 

activities with the potential to disturb undiscovered 

BLM Vegetation Treatments Using Herbicides 4-111 January 2016

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ENVIRONMENTAL CONSEQUENCES

resources continue to occur in the western U.S. These 

activities include resource extraction, livestock grazing, 

and motorized recreation, among others. Over time,

additional buried resources may be exposed naturally 

through erosion, increasing their susceptibility to 

damage or collection. Additionally, wildfires and 

invasive species have altered native plant communities, 

and continue to displace native plants and animals that 

provide traditional lifeway values to Native peoples.

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be the same under all of the 

alternatives, there would be no difference in the 

geographic extent of public lands targeted by herbicide 

treatments under any of the alternatives. Therefore, risks 

for impacts to paleontological and cultural resources 

would also be the same. Countervailing effects 

associated with controlling invasive species and 

reducing the risk of catastrophic wildland fire, which 

would improve conditions for native plants and animals 

that provide traditional lifeway values, would also be 

similar under all the alternatives. 

Under the No Action Alternative, the number of 

herbicides used by the BLM would be 18. Under 

Alternatives B and C, three additional herbicides would 

be used, and under Alternative D, two additional 

herbicides would be used. Adding new herbicides 

would increase the total number of active ingredients 

released into the environment. From a perspective of 

potential risks to Native Americans from exposure to 

herbicides, the three new herbicides have no to low risk 

to humans via various exposure scenarios. The potential 

for synergistic human health effects associated with 

mixtures of multiple ingredients is not known. 

Visual Resources

Past Effects and Their Accumulation

Past effects to visual resources, and their accumulation,

are discussed in the 2007 PEIS (USDOI BLM 2007a:4-

229 to 4-230). Humans have altered the visual character 

of lands in the western U.S. through activities such as 

resource extraction, agriculture, road construction, 

urbanization and other development, timber harvesting, 

livestock grazing, introduction of exotic species, and 

exclusion of fire. As a result, landscapes have changed, 

and are now marked by different vegetation 

composition, structure, and pattern.

Future Effects and Their Accumulation

Future effects to visual resources, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-225). The activities described in the 

preceding paragraph continue to influence the visual 

characteristics and scenic quality of landscapes. 

Ongoing vegetation management programs will alter the 

visual quality of public lands over the short term by 

removing vegetation, and in some cases creating large 

areas of open, browned, or blackened landscapes. 

However the BLM’s long-term goals to restore 

degraded lands, reinstate properly functioning 

ecosystem processes, and restore degraded lands will 

likely help improve the visual character of public lands, 

particularly for VRM Class I and II lands with high 

scenic values. Other federal, state, tribal, and local 

agencies, and private conservation groups will also 

continue efforts to improve land health which will result 

in countervailing effects to visual resources. 

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides would be similar under all of the alternatives, 

impacts to visual resources would occur over a similar

geographic area under all alternatives. Additionally, the 

degree of the effects, and their contribution to 

cumulative effects, would be similar under all the 

alternatives. None of the alternatives would alter land 

uses on public lands, or introduce long-term changes 

that would be in conflict with the BLM’s visual 

resource management goals. Over the long term, all of 

the alternatives would be expected to contribute 

positively to scenic qualities of public lands. 

Additionally, all of the alternatives would help reduce 

the risk of wildfire that has a visual impact on public 

lands and other scenic lands in the western U.S.

Wilderness and Other Special Areas

Past Effects and Their Accumulation

Past effects to wilderness and other special areas, and 

their accumulation, are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-229 to 4-231). While wilderness 

and other special areas continue to be protected from

development by their status designations, these areas are 

threatened by factors that degrade their unique qualities. 

These factors include: 1) exotic and non-native species; 

2) wildland fire suppression; 3) loss of water and 

deterioration in water quality; 4) fragmentation and 

BLM Vegetation Treatments Using Herbicides 4-112 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

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. All of these factors 

continue to contribute to loss of wilderness values or 

other unique qualities. 

Future Effects and Their Accumulation

Future effects to wilderness and other special areas, and 

their accumulation, are discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-231 to 4-232). The threats 

described in the previous paragraph are ongoing, and 

will continue to impact the unique qualities of 

wilderness and other special areas. With increases in 

population these areas may be further degraded through 

overuse. Additionally, pressure to utilize protected areas 

for resource extraction may result in future loss or 

degradation of these areas. Vegetation treatment 

programs in and near these areas that aim to control the 

spread of noxious weeds and restore natural fire 

regimes, if successful, will help reduce some of the 

threats to wilderness and other special areas, but not 

others. Actions by conservation groups and other 

entities to protect these areas may also help offset or 

slow some of the factors that degrade the unique 

qualities of wilderness and other special areas. 

Contribution of Alternatives to Cumulative Effects

Because the acreage of public lands treated with 

herbicides, as well as the areas targeted for treatments,

would be similar under all of the alternatives, the 

impacts to wilderness and other special areas would also 

be similar under all the alternatives. Adverse effects to 

these areas would generally be short-term effects 

associated with site closures and disturbances during 

herbicide treatments. Therefore, they would not be 

expected to contribute to long-term adverse effects. 

Countervailing effects associated with slowing future 

degradation of these areas or improving them through 

control of invasive species and restoration of native 

habitats and disturbance regimes would also be similar

under all the alternatives.

The number of herbicides used, which would vary to 

some degree under the alternatives, would not be 

expected to have a substantial difference in how the 

action contributes to cumulative effects. The BLM 

would be able to control target species and reduce 

wildfire risk under all alternatives, although there would 

be a few additional options under the action alternatives. 

Under the No Action Alternative, the number of 

herbicides used by the BLM with the potential to impact 

wildlife would be 18. Under Alternatives B and C, three 

additional herbicides would be used, and under 

Alternative D, two additional herbicides would be used. 

The use of new active ingredients could introduce new 

chemicals to areas that are relatively undisturbed. 

Although the new active ingredients have low risk to 

fish, wildlife, and other resources, the cumulative 

increase in pesticide use in wilderness and other special 

areas could have a negative connotation from a public 

opinion perspective.

Recreation

Past Effects and Their Accumulation

Past effects to recreation, and their accumulation, are 

discussed in the 2007 PEIS (USDOI BLM 2007a:4-223 

to 4-233). Recreation opportunities on public lands have 

increased with the creation of recreational facilities and 

development of numerous recreation programs. These 

programs provide opportunities for outdoor recreation 

for millions of visitors annually. Other uses on BLM 

lands, such as livestock grazing, timber harvesting, and 

oil and gas activities, have limited recreation 

opportunities in certain locations. Additionally, the 

spread of invasive plants and wildfires have adversely 

affected recreation opportunities.

Future Effects and Their Accumulation

Future effects to visual resources, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-233 to 4-234). With the growth of the 

population in the West and a continued interest in 

recreation, the amount of use that BLM lands receive by 

the public will likely continue to increase. At the same 

time, the BLM will not be able to substantially expand 

its recreational opportunities. Therefore, existing lands 

and recreational facilities will be used more intensively, 

potentially reducing the recreation experience in certain 

areas and resulting in degradation of recreational 

facilities. Recreational visitors likely contribute to the 

spread of invasive species on public lands. Additionally, 

development and other activities in areas near public 

lands could lessen recreational experiences if they are 

visible from public lands. 

Vegetation treatment programs by the BLM have a goal 

of restoring native plant communities, improving 

wildlife habitat quality, controlling the spread of 

invasive species, and reducing wildfire risk, and would 

help to offset some of the impacts caused by 

BLM Vegetation Treatments Using Herbicides 4-113 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

recreationists, as well as improve the quality of 

recreational opportunities on public lands. 

Contribution of Alternatives to Cumulative Effects

The acreage of public lands treated with herbicides 

would be similar under all of the alternatives, and 

impacts to recreation would occur over a similar

geographic area under all alternatives. Additionally, the 

degree of the effects, and their contribution to 

cumulative effect, would be similar under all the 

alternatives. Adverse effects associated with herbicide 

treatments would be short-term in duration, and would 

be unlikely to contribute to long-term adverse effects to 

recreation. Beneficial effects associated with control of 

invasive species, reduction of wildfire risk, and 

restoration of native plant communities would be 

similar under all of the alternatives. 

Under the No Action Alternative, the number of 

herbicides used by the BLM would be 18. Under 

Alternatives B and C, three additional herbicides would 

be used, and under Alternative D, two additional 

herbicides would be used. Under all alternatives, 

herbicides would be available that would allow the 

BLM to meet its treatment goals, including control of 

invasive species at visitor centers and other recreational 

facilities, restoration of native communities, and 

protection of recreation sites from risks associated with 

wildfire. The action alternatives would allow the BLM 

additional options for treating invasive species that 

could improve the effectiveness of treatment programs 

in certain circumstances. Additionally, aminopyralid 

and fluroxypyr would be mixed with other active 

ingredients to improve their effectiveness against certain 

target plants, and may help address resistance 

management issues at sites where invasive species are 

controlled repeatedly. 

Social and Economic Values

Past Effects and Their Accumulation

Past effects to social and economic values, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-235 to 4-236). Social and economic 

factors that are important from the perspective of public 

lands include the continued population growth in the 

western U.S. (13.8 percent between 2000 and 2010; 

U.S. Department of Commerce Bureau of the Census 

2011), environmental justice concerns associated with 

communities with high densities of Native Americans 

and other minority populations, the importance of jobs 

and industries associated with natural resources and 

resource extraction, increasing wildfire risks and 

associated risks to private property, and economic 

benefits from activities conducted on BLM lands, such 

as grazing, harvest of timber and other forest products, 

and oil, gas, and geothermal development. 

Industries related to natural resources, such as 

agriculture and mining, are important sources of 

employment and represent nearly half of the nation’s 

agricultural services, forestry, and fishing jobs.

Future Effects and Their Accumulation

Future effects to social and economic values, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-236 to 4-238).

It is expected that populations in the western U.S. will 

continue to increase, and that use of BLM-administered 

lands by the public will also continue to increase. 

Population growth is cumulative, and actions on public 

lands and elsewhere will continue to affect greater 

numbers of people, including larger minority and low 

income populations. BLM lands will continue to 

provide a source of revenue for the federal government 

and local economies, with a possible low-level increase 

in those benefits through activities to improve the 

condition of rangelands and other public lands. Oil, gas, 

geothermal, and mineral resource extraction on public 

lands is expected to continue to be an important source

of income into the future. Recreation is also likely to 

continue to be an important source of income, with 

vegetation treatments that improve the quality of public 

lands for recreation likely to benefit recreational 

opportunities. 

It is expected that expenditures by the BLM will 

continue to range from about $1 billion to $1.15 billion, 

with budgets fluctuating from year to year. It is also 

expected that the BLM will continue to generate more 

revenue for the federal government than it spends. Oil 

and gas resources will likely continue to be the primary 

source of revenue, with timber sales, grazing, and 

recreation also important, although to a much lesser 

degree. 

With population increases in the western U.S., it is 

expected that effects to private property from activities 

on public lands will be an increasing concern. However, 

efforts by the BLM, Forest Service, and other agencies 

to reduce wildfire risk may have an overall benefit to 

private property over the long term if incidence and 

severity of wildfire is reduced, particularly in the WUI. 

BLM Vegetation Treatments Using Herbicides 4-114 January 2016

Final Programmatic EIS
ENVIRONMENTAL CONSEQUENCES

Contribution of Alternatives to Cumulative Effects

All of the alternatives would reduce the costs of 

herbicide treatments, although it is expected that there 

would be no difference in the BLM’s overall 

expenditures on vegetation treatments. Under 

Alternative B, the cost reduction could be between 1 

and 2 percent, whereas the reduction would be less than 

1 percent under Alternative B, and a fraction of 1 

percent under Alternative D. Annual vegetation 

treatments costs, assuming all methods, would be 

similar under all the alternatives, amounting to an 

estimated $1.4 billion. Under all alternatives, short-term 

adverse impacts in terms of costs and long-term 

improvements in terms of resource benefits would be 

similar, although the cost to obtain the same degree of 

benefit could be slightly higher under Alternatives B 

and C because of lower herbicide costs. Under all 

alternatives, the contribution of treatment actions to the 

economy of the western U.S. would continue to be 

minor.

Human Health and Safety

Past Effects and Their Accumulation

Past effects to human health and safety, and their 

accumulation, are discussed in the 2007 PEIS (USDOI 

BLM 2007a:4-238 to 4-241). In terms of occupational 

risks, workers in the western U.S., including workers on 

public lands, have been exposed to risks associated with 

use of power tools, vehicles, loud noises, and other risk 

factors. Certain occupations may expose workers to 

chemicals (including pesticides) and other substances 

that can lead to cancer and other health conditions. Jobrelated fatalities and injuries continue to be reported in 

the western states. The public is also exposed to various 

chemicals and environmental pollutants, and may be at 

risk for injury or death as a result of fire, particularly in 

the WUI. 

Future Effects and Their Accumulation

Future effects to human health, and their accumulation, 

are discussed in the 2007 PEIS (USDOI BLM 2007a:4-

212 to 4-213). Many of the health and safety concerns 

discussed in the preceding paragraph will continue to be 

concerns in the future. Many occupations will continue 

to be associated with some level of risk, particularly 

when vehicles and machinery are operated, and when 

workers are exposed to potentially hazardous chemicals. 

Firefighters will continue to be exposed to high levels of 

risk. However, implementation of employer health and 

safety programs and associated steps to reduce risk will 

continue to help protect worker health and safety. 

Pesticide operators and other BLM workers will 

continue to transport and handle ingredients that pose a 

toxicological risk to humans, although these risks will 

continue to be minimized through SOPs and use of 

appropriate personal protective equipment.

The public will continue to be exposed to various 

pollutants; the cumulative effects of these exposures 

could include development of cancer and health 

conditions. Risks associated with wildfire, such as 

smoke inhalation risks and potential for loss of life, 

could increase if large, difficult to control wildfires 

continue to increase in frequency and size. Treatment 

programs by the BLM and other agencies to take 

aggressive actions to reduce catastrophic fire risk may 

continue to offset some of the wildfire risk in targeted 

areas, such as the WUI where the most people are likely 

to be affected. 

Contribution of Alternatives to Cumulative Effects

Under all of the alternatives, a similar acreage would be 

treated with herbicides annually, with the same 

treatment goals, so the geographic extent of adverse and 

beneficial effects associated with herbicide use would 

also be similar. Under all of the alternatives, herbicides 

with some risk to human health would be applied in the 

same areas on public lands, although the number of 

herbicides used and the amounts of usage would vary 

among the alternatives. Under the action alternatives, 

two or three new active ingredients would be used, in 

addition to currently approved herbicides, resulting in a 

cumulative increase in the number of ingredients used 

on public lands. The new herbicides have no to very low 

risk to human health via various exposure scenarios. 

The potential for synergistic human health effects 

associated with mixtures of multiple ingredients is not 

known.

Benefits to human health from herbicide treatments 

would be similar under all the alternatives. Treatments 

would help reduce wildfire risk and associated risks to 

human health. Over the long term, restoration of natural 

fire regimes and improvement in ecosystem health 

should reduce risks to human health from activities 

originating on public lands and affecting public land 

users or those living near public lands.

Unavoidable Adverse Effects

The 2007 PEIS summarizes the unavoidable adverse 

effects that would occur as a result of the BLM’s 

vegetation management programs, including herbicide

BLM Vegetation Treatments Using Herbicides 4-115 January 2016

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ENVIRONMENTAL CONSEQUENCES

treatments with the 18 currently approved herbicides 

and other forms of vegetation treatment analyzed in the 

2007 PER (USDOI BLM 2007a:4-243 to 4-246).

As the three new herbicides would be incorporated into 

the BLM’s treatment programs, but the extent and goals 

of those programs would remain unchanged, the 

analysis provided in the 2007 PEIS is largely applicable 

to treatments involving aminopyralid, fluroxypyr, and 

rimsulfuron. This information is summarized here.

Air Quality

Herbicide treatments would continue to result in the 

release of air quality pollutants, including GHGs. No 

new air emissions would occur as a result of adding the 

three new herbicides.

Soil Resources

Herbicide treatments would continue to result in 

increased erosion over the short term, and potentially 

loss of soil and soil function and productivity. No

additional impacts to soil would occur as a result of 

adding the three new herbicides, although soil resources 

would be exposed to new active ingredients and their 

degradation products.

Water Resources and Quality

Herbicide treatments would continue to result in soil 

erosion and surface water runoff from removal of 

vegetation, and impacts to surface water and 

groundwater quality. The geographic extent of water 

resources potentially exposed to herbicide treatments

would show little change as a result of adding the three 

new herbicides, but new active ingredients, degradates, 

and other ingredients would be released to the 

environment, increasing the number of potential water 

contaminants.

Wetland and Riparian Areas

Herbicide treatments in wetlands and riparian areas 

would continue to increase soil erosion and surface 

water runoff, potentially leading to streambank erosion 

and sedimentation into wetlands and riparian areas. 

Removal of vegetation could also alter wetland 

hydrology and function. The extent of these impacts 

would not change substantially from current levels as a 

result of adding the three new herbicides.

Vegetation

Herbicide treatments would continue to cause 

unavoidable short-term disturbances to plant 

communities by killing both target and non-target 

plants. The extent of these impacts is not expected to 

change substantially as a result of adding the three new 

herbicides, as they act by modes of action similar to 

those of some of the currently approved active 

ingredients. 

Fish and Other Aquatic Organisms

Removal or alteration of vegetation in and near aquatic 

habitats would continue to affect fish and other aquatic 

organisms through release of sediments into habitats, or 

by changing other habitat characteristics (such as 

amount of shading). With the addition of the three new 

herbicides, the extent of these impacts would show little 

change.

Wildlife Resources

Some wildlife would be exposed to herbicides as a 

result of treatments and could suffer toxicological 

effects. Adding the three new herbicides would not 

substantially change the level of effects to wildlife, and 

could potentially decrease them, as the three new 

herbicides are of low risk to wildlife. Herbicide 

treatments would also continue to alter wildlife habitat, 

and could cause unavoidable short-term adverse effects 

to wildlife habitat and behavior. With the addition of the 

three new herbicides, the extent of these impacts would 

not change substantially. 

Livestock

Herbicide treatments would continue to temporarily 

affect livestock by removing non-target vegetation used

as forage or for other needs. Some exposure of livestock 

to herbicides could also occur, potentially resulting in 

toxicological effects. The three new herbicides do not 

pose a risk to livestock, and would not increase impacts 

to vegetation used by livestock over current levels.

Wild Horses and Burros

Herbicide treatments would continue to have the 

potential to impact wild horses and burros by removing 

non-target vegetation used as forage or for other needs. 

Some exposure of livestock to herbicides could also 

occur, potentially resulting in toxicological effects. The 

three new herbicides do not pose a risk to wild horses 

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ENVIRONMENTAL CONSEQUENCES

and burros, and would not increase impacts to 

vegetation used by these animals over current levels.

Paleontological and Cultural Resources

Paleontological Resources

Herbicide treatments would continue to have the 

potential to affect fossil resources through exposure of 

these resources or potential chemical alterations 

associated with active or other ingredients in herbicide 

formulations. The action to add three new herbicides 

would not increase the likelihood of risk to these 

resources unless one of the active ingredients is 

particularly damaging to fossil resources. Use of SOPs 

would reduce the likelihood of impacts to 

paleontological resources. 

Cultural Resources and Traditional Lifeway 

Values 

Herbicide treatments would continue to have the 

potential to affect cultural resources, primarily through 

chemical alterations of cultural materials associated 

with active or other ingredients in herbicide 

formulations. Use of herbicides would continue to have 

the risk of impacting non-target plant species of cultural 

importance to Native peoples. Herbicide treatments 

could also discourage or prohibit Native peoples from 

using these areas, or potentially harm Native peoples 

harvesting plant materials or conducting other activities 

in treated areas. However, the addition of three new 

active ingredients would not increase these unavoidable 

risks or impacts beyond current levels.

Visual Resources

Herbicide treatments would not result in unavoidable 

adverse effects to visual resources over the long term, 

but over the short term they could adversely affect the 

visual character of the treated areas. Adding the three 

new herbicides would not substantially change the 

extent or degree of effects to visual resources.

Wilderness and Other Special Areas

Herbicide treatments would continue to affect 

wilderness and other special areas through removal of 

vegetation, alteration of plant communities, and through 

human presence in wilderness areas. Adding the three 

new herbicides would not substantially change the 

extent or degree of these effects.

Recreation

Unavoidable adverse effects to recreation from 

herbicide treatments would continue to include scenic 

degradation and noise associated with treatments, 

alteration of resources, and the temporary closure of 

certain areas to recreation. Adding the three new 

herbicides would not substantially change the extent or 

degree of these effects. 

Social and Economic Values

Short-term closures or restrictions on public lands, such 

as implementation of herbicide use re-entry restrictions 

to protect public health or to restrict access by grazing 

animals for the time period specified on the herbicide 

label until seeding efforts are established (up to two 

growing seasons), would continue to be unavoidable. 

Communities that are particularly dependent on a single 

industry would continue to be the 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 

continue to 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.

Adding the three new herbicides would not substantially 

change the extent or degree of these effects.

Human Health and Safety

Herbicide treatments would continue to have the risk of 

harming workers or the public, primarily through 

accidental exposures to herbicides. Although workers 

would follow all SOPs to reduce risks, not all risks 

could be avoided. The addition of three new active 

ingredients would not increase the degree of risks to 

human health and safety. The three new active 

ingredients have no to low risks to humans.

Relationship between the Local Shortterm Uses and Maintenance and 

Enhancement of Long-term 

Productivity

This section discusses the short-term effects of 

herbicide treatment activities, versus the maintenance 

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ENVIRONMENTAL CONSEQUENCES

and enhancement of potential long-term productivity of 

public land environmental and social resources. The 

2007 PEIS summarized this information for the BLM’s 

ongoing vegetation management programs (USDOI 

BLM 2007a:4-246 to 4-251).

As the three new herbicides would be incorporated into 

the BLM’s vegetation management programs, but the 

extent and goals of those programs would remain 

unchanged, the analysis provided in the 2007 PEIS is 

largely applicable to treatments involving aminopyralid, 

fluroxypyr, and rimsulfuron. This information is 

summarized here.

In all cases, short-term refers to the total duration of 

vegetation treatment activities (10 to 15 years) and longterm refers to an indefinite period of time.

Air Quality

Herbicide treatments would have a small short-term 

impact on air quality, predominantly associated with use 

of vehicles during applications. Much of the focus of 

treatments is on reducing hazardous fuels, restoring 

natural fire regimes and reducing the occurrence of 

large, unwanted wildfires. Thus, the proposed 

vegetation treatments should reduce smoke emissions 

associated with public lands over the long term. While 

individual herbicide treatment projects would have 

GHG emissions, repeated herbicide treatments and posttreatment reseeding/restoration may reduce the risk of

wildfire, leading to fewer GHG emissions in the long 

term.

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.

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 USDOI 

BLM 2000).

Water Resources and Quality

Herbicide treatments would result in short-term impacts 

to water quality through movement of active and other 

ingredients into the water and through erosion and 

surface water runoff from treatment sites. 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. Additionally, treatments that 

reduce hazardous fuels would benefit ecosystems by 

reducing the chances of a large, unwanted 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.

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. Additionally, 

there could be some release of active and other 

ingredients into 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. 

Vegetation

Herbicide treatments would remove vegetation from 

treatment sites over the short term, and could impact 

non-target desirable vegetation. However, treatments 

that remove or control invasive vegetation would 

benefit non-target species by providing increased access 

to water and nutrients and enhanced vigor from reduced 

competition with invasive species. Over the long term, 

target sites should have an increased component of 

native species. Additionally, control of cheatgrass and 

other fire adapted species would benefit the long-term 

health of plant communities in which natural fire cycles 

have been altered. Over the long term, treatments 

should also reduce the occurrence of large, unwanted

wildfires across the western U.S.

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Fish and Other Aquatic Organisms

Herbicide treatments could have short-term adverse 

impacts to fish and other aquatic organisms through 

release or movement of active and other ingredients into 

aquatic habitats. These impacts would be minimized 

through the use of buffers. The three new herbicides are 

of low risk to aquatic species. Over the long term, 

control of noxious weeds in riparian habitats, reduction 

of wildfire risk through hazardous fuels reduction, and 

other efforts to improve the quality of watersheds would 

have beneficial effects on fish and other aquatic 

organisms. Benefits would include improved habitat 

quality, improved hydrologic functions, and reduced 

soil erosion. 

Wildlife Resources

All treatments could have short-term adverse impacts to 

wildlife and wildlife habitat, as discussed under 

Unavoidable Adverse Effects above. The three new 

herbicides are of lower risk to wildlife than many of the 

currently approved herbicides. Treatments that improve 

habitat would provide long-term benefits to wildlife by 

restoring wildlife habitat and reducing the risk of 

catastrophic wildfire. Habitat improvements would 

likely be slow, occurring over multiple decades.

Livestock

The proposed vegetation treatments would affect the 

availability and palatability of livestock forage over the 

short term. These impacts would begin to disappear 

within one to two growing seasons after treatment. Over 

the long term, the quality of forage should improve, as 

noxious weeds that are unpalatable or toxic to wildlife 

would be controlled. Additionally, reduction in the risk 

of future catastrophic wildfire would benefit livestock 

by preventing the temporary loss of large blocks of 

rangeland to fire, and reducing the prevalence of fireadapted species.

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. Over the 

long term, the quality of forage should improve, as 

noxious weeds that are unpalatable or toxic to wild 

horses and burros would be controlled. Additionally, 

reduction in the risk of future catastrophic wildfire 

would benefit wild horses and burros by preventing the 

temporary loss of large blocks of habitat that would 

displace wild horses and burros and potentially reduce 

the AML.

Paleontological and Cultural Resources 

Paleontological Resources

Because paleontological resources are nonrenewable, 

there is no difference between short-term and long-term 

impacts. These resources cannot recover from some 

types of adverse impacts. Once disturbed, the materials 

and information of paleontological deposits may be 

permanently compromised. Chemical alterations to 

fossil materials would likely be permanent. Any 

destruction of paleontological sites, especially those 

determined to have particular scientific value, would 

represent long-term losses. Furthermore, once 

paleontological deposits are 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. Chemical alterations to 

historic materials would likely be permanent. 

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 herbicide 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.

Herbicide treatments could have short-term impacts on 

traditional lifeway values by temporarily restricting 

access to traditional use sites, and by impacting nontarget vegetation of cultural importance. Herbicide 

treatments could also temporarily displace wildlife used 

for subsistence. 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. 

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Visual Resources 

Vegetation treatments would continue to affect visual 

resources by changing the scenic quality of the 

landscape. Over the short term, impacts to visual 

resources from herbicide treatments 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 treated areas, and the 

site would develop a more natural appearance. 

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 the 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 cheatgrass monoculture). 

Wilderness and Other Special Areas

Impacts to wilderness and other special areas would 

begin to disappear within one to two growing seasons 

after herbicide treatments. The regrowth of vegetation 

on the site would eliminate much of the stark 

appearance of treated areas, and the site would develop 

a more natural appearance. 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 in wilderness and other special areas. 

Treatments that successfully rehabilitate degraded 

ecosystems would result in plant communities that are 

dominated by native species (see the Vegetation section 

for more information). Native-dominated communities 

often provide better habitat for fish and wildlife, 

including species of concern, that occur in communities 

with a large component of non-native species.

Recreation

There would be some scenic degradation, as well as 

distractions to users (e.g., noise from vehicles), from 

treatments. In addition, there would be some human 

health risks to recreationists associated with exposure to 

herbicides, which would be minimized through use of 

SOPs. Finally, some areas would be off-limits to 

recreation activities as a result of treatments. These 

effects would be localized and short-term.

Treatments that restore native vegetation and natural 

fire regimes and other ecosystem processes would 

provide a long-term benefit to recreationists. Treatments 

would improve the aesthetic and visual qualities of 

recreation areas, 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. 

Social and Economic Values

Over the short term, 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 

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, and climate) over which the 

BLM and other federal agencies have no control 

(USDA Forest Service and USDOI BLM 2000). 

Human Health and Safety

Herbicide treatments could harm the health of workers 

and the public over the short term, although SOPs 

would minimize these risks. The three new herbicides 

have no to low health risks under most exposure 

scenarios. Adverse reactions to 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 were to result from treatments 

(most likely to occur as a result of vehicle operation), 

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 

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ENVIRONMENTAL CONSEQUENCES

to restore natural fire regimes and improve ecosystem 

health, which would in turn provide a benefit to human 

health. A reduced risk of wildfire would reduce the risk 

of injury, death, and other health risks associated with 

fire. Additionally, herbicide treatments would slow the 

spread of poisonous and other noxious weeds that are 

harmful or annoying to humans. 

Irreversible and Irretrievable 

Commitment of Resources

This section identifies irreversible and irretrievable 

commitments of resources that would occur from 

herbicide 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.

Since aminopyralid, fluroxypyr, and rimsulfuron would 

be utilized in existing treatment programs and are 

generally of low risk to resources, their addition to the 

list of approved active ingredients would not result in 

additional irreversible or irretrievable commitments of 

resources above what was discussed in the 2007 PEIS 

(USDOI BLM 2007a:4-251 to 4-253). Commitments 

pertaining to herbicide treatments from this earlier 

document are summarized here.

Air Quality

Air quality would be affected by emissions from 

vehicles used during herbicide applications. 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

Herbicides could impact soil biota and productivity, 

although it is unclear to what degree these effects would 

be irreversible or irretrievable. It is expected that soil 

functions would eventually return with the 

establishment of native vegetation and a reduced risk of 

wildfire. 

Water Resources and Quality

An accidental herbicide spill 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. In many cases, these 

impacts could be reversed over time through 

degradation of the active and other ingredients and their 

degradates. In other cases, irreversible or irretrievable 

commitments of water resources could occur.

Wetland and Riparian Areas

Although there would be short-term impacts to these 

resources from herbicide treatments, these impacts 

generally would not be irretrievable and would be 

reversed with degradation of the herbicides and if 

restoration treatments were successful. Under certain 

circumstances, irreversible or irretrievable commitments 

of wetland or riparian resources could occur.

Vegetation

Native vegetation and plant productivity that is lost as a 

result of treatments would be irretrievable only until 

vegetation is reestablished, usually within several 

growing seasons. Some individual plants would be 

affected irreversibly. However, with the use of 

appropriate buffers to protect populations, irreversible 

and irretrievable loss of special status plants would not 

occur.

Fish and Other Aquatic Organisms

Special status aquatic invertebrates would be at risk for 

adverse toxicological effects from herbicide treatments

with fluroxypyr under accidental spill scenarios. Buffer 

zones to protect aquatic species would minimize these 

risks. While some individual organisms could be 

affected irreversibly by alterations to habitat, overall 

effects to populations would be reversible. Additionally, 

populations would benefit from treatments that improve 

riparian and aquatic habitats. 

Wildlife Resources

While none of the three new herbicides pose a 

toxicological risk to wildlife, some individual organisms 

could be affected irreversibly by equipment used during 

treatments or habitat modification. However, overall 

effects to populations would be reversible. Native 

wildlife and habitat productivity that is lost as a result of 

treatments would be irretrievable until native plant 

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ENVIRONMENTAL CONSEQUENCES

communities are 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 improve as a result of treatments, their 

ability to support livestock use levels at or near current 

levels should also improve. Herbicide treatments have 

the potential to cause toxicological impacts to livestock, 

although the three new herbicides are of low toxicity to 

large grazing mammals. Any 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 herbicide 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 or long-term pastures, or 

sold. As rangelands improve, their ability to support 

populations of wild horses and burros near current 

levels would also improve.

Herbicide treatments have the potential to cause 

toxicological impacts to wild horses and burros, 

although the three new herbicides are of low toxicity to 

large grazing mammals. Any associated impacts to 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. Any chemical changes 

to cultural materials associated with herbicide exposure 

would potentially be permanent. 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 

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 are successful.

Wilderness and Other 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 are 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 

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ENVIRONMENTAL CONSEQUENCES

irretrievable and could be reversed if restoration 

treatments are successful.

Social and Economic Values

Herbicide treatments would continue to involve a 

substantial commitment by the BLM in terms of labor 

and financial resources. Herbicide treatments associated 

with restoration activities would continue to provide

temporary jobs in the western U.S. Once financial 

resources are used, they cannot 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 herbicide 

treatments could be irreversible and irretrievable. Risk 

of death or serious injury is very low, based on low 

numbers of past incidents, but accidents do occur. It is 

possible that humans would experience minor 

discomfort from herbicide treatments, but provided 

appropriate safety SOPs are implemented, 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. Less energy would be used to conduct aerial 

treatments than ground treatments for each acre treated. 

Because all of the alternatives treat the same land area 

using herbicides, energy use for all, including the No 

Action Alternative, would be similar. 

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, and 

would be roughly the same under all of the alternatives, 

as the acreage treated would be similar. All herbicide 

treatment methods require the use of energy, as 

described in the preceding section.

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