Environmental Effects of Off-Highway Vehicles on 

Bureau of Land Management Lands: A Literature 

Synthesis, Annotated Bibliographies, Extensive 

Bibliographies, and Internet Resources 

By Douglas S. Ouren, Christopher Haas, Cynthia P. Melcher, 

Susan C. Stewart, Phadrea D. Ponds, Natalie R. Sexton, 

Lucy Burris, Tammy Fancher, and Zachary H. Bowen

 

Open-File Report 2007-1353 

U.S. Department of the Interior 

U.S. Geological Survey 
Cover photo courtesy of Bureau of Land Management, Denver, Colorado. 

ii 
U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2007 

For product and ordering information: 

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For more information on the USGS—the Federal source for science about the Earth, its natural world and 

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Suggested citation: 

Ouren, D.S., Haas, Christopher, Melcher, C.P., Stewart, S.C., Ponds, P.D., Sexton, N.R., Burris, Lucy, Fancher, 

Tammy, and Bowen, Z.H., 2007, Environmental effects of off-highway vehicles on Bureau of Land Management 

lands: A literature synthesis, annotated bibliographies, extensive bibliographies, and internet resources: U.S. 

Geological Survey, Open-File Report 2007-1353, 225 p. 

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by 

the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual copyright owners 

to reproduce any copyrighted material contained within this report. 

iii 
Contents 

Tables ................................................................................................................................................................vii

Conversion Factors ........................................................................................................................................viii

Glossary .............................................................................................................................................................ix

Acknowledgments ............................................................................................................................................x

Executive Summary .........................................................................................................................................xi

Terminology Used in This Report.............................................................................................................xi

How to Use This Report .............................................................................................................................xi

OHV Effects .................................................................................................................................................xii

OHV Effects on Soils and Watersheds .............................................................................................xii

OHV Effects on Vegetation .................................................................................................................xii

OHV Effects on Wildlife and Habitats: Native, Threatened, and Endangered Species...........xii

OHV Effects on Water Quality ............................................................................................................xii

OHV Effects on Air Quality .................................................................................................................xiii

Socioeconomic Implications of OHV Use .......................................................................................xiii

Potential Indicators (Both Direct and Indirect) for Evaluating and Monitoring OHV Effects .....xiii

Mitigation and Site-Restoration Techniques.......................................................................................xiv

Monitoring and Research Needs to Support OHV Management Decisions ..................................xv

1.0 Introduction..................................................................................................................................................1

1.1 Issue Context: Bureau of Land Management Land Health and Off-highway Vehicle Use ......1

1.1.1 Bureau of Land Management Land Health Standards...........................................................1

1.1.2 Increasing OHV Use......................................................................................................................2

1.2 Objectives, Scope, Organization, and Use of This Report..............................................................2

1.2.1 Objectives .......................................................................................................................................2

1.2.2 Geographical Scope .....................................................................................................................2

1.2.3 Organization ...................................................................................................................................2

1.2.4 Tips on Navigating This Document ............................................................................................3

1.3 Definitions of OHV Routes/Roads, Vehicles, and Activities...........................................................3

1.3.1 Definitions of Roads and Trails Used in This Report...............................................................3

1.3.2 Definitions of OHVs and OHV Activities Used in This Report................................................4

2.0 Effects of OHV Travel on Natural Resource Attributes and Socioeconomics.................................4

2.1 Scale and Patterns of OHV Activities and Their Effects.................................................................4

2.2 OHV Effects on Soils and Watersheds...............................................................................................5

2.2.1 Section Summary ..........................................................................................................................5

2.2.2 Soil Compaction and Reduced Water Infiltration....................................................................6

2.2.3 Effects on Soil Stabilizers and Rates of Soil Erosion ..............................................................7

2.2.4 Annotated Bibliography for OHV Effects on Soils and Watersheds ....................................8

2.3 OHV Effects on Vegetation.................................................................................................................11

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2.3.1 Section Summary ........................................................................................................................11

2.3.2 Overall Effects on Vegetation Cover and Community Composition ...................................11

2.3.3 Edge Effects Along OHV Routes ...............................................................................................12

2.3.4 Annotated Bibliography for OHV Effects on Vegetation ......................................................13

2.4 OHV Effects on Wildlife and Habitats: Native, Threatened, and Endangered Species ..........16

2.4.1 Section Summary ........................................................................................................................16

2.4.2 Loss of Habitat Connectivity: Fragmentation and Barrier Effects ......................................16

2.4.3 Edge Effects..................................................................................................................................18

2.4.4 OHV Disturbance and Noise......................................................................................................19

2.4.5 Wildlife Mortality and Related Issues .....................................................................................20

2.4.6 Annotated Bibliography for OHV Effects on Wildlife and Habitats: Native, Threatened, 

and Endangered Species....................................................................................................................22

2.5 OHV Effects on Water Quality ...........................................................................................................25

2.5.1 Section Summary ........................................................................................................................25

2.5.2 Sedimentation and Turbidity .....................................................................................................25

2.5.3 Dust and Contaminants ..............................................................................................................26

2.5.4 Annotated Bibliography for OHV Effects on Water Quality.................................................27

2.6 OHV Effects on Air Quality..................................................................................................................29

2.6.1 Section Summary ........................................................................................................................29

2.6.2 Fugitive Dust Raised by OHV Traffic ........................................................................................29

2.6.3 Contaminants Associated with OHV Use................................................................................29

2.6.4 Annotated Bibliography for OHV Effects on Air Quality .......................................................31

2.7 Socioeconomic Implications of OHV Use .......................................................................................33

2.7.1 Section Summary ........................................................................................................................33

2.7.2 Trends in OHV Use and Technology ........................................................................................33

2.7.3 Types, Sources, and Effects of OHV User Conflict................................................................33

2.7.4 OHV Users and Their Preferences...........................................................................................34

2.7.5 Economic Benefits and Costs of OHV Use .............................................................................38

2.7.6 Annotated Bibliography for Socioeconomic Implications of OHV Use .............................38

3.0 Potential Indicators for Evaluating and Monitoring OHV Effects .....................................................41

3.1 Summary................................................................................................................................................41

3.2 BLM’s Indicators of Land Health Compared to Indicators of OHV Effects Described in the 

Literature .....................................................................................................................................................43

3.3 Some Potential Indicators for Evaluating and Monitoring OHV Effects ....................................46

3.3.1 Potential Indicators of OHV Effects on Soils and Watersheds...........................................46

3.3.2 Potential Indicators of OHV Effects on Vegetation ...............................................................47

3.3.3 Potential Indicators of OHV Effects on Wildlife and Habitats: Native, Threatened, and 

Endangered Species............................................................................................................................48

3.3.4 Potential Indicators of OHV Effects on Water Quality..........................................................50

3.3.5 Potential Indicators of OHV Effects on Air Quality................................................................50

3.3.6 Potential Indicators for OHV Effects on Socioeconomics ...................................................51

4.0 Mitigation and Site-Restoration Techniques .......................................................................................52

4.1 Summary................................................................................................................................................52

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4.2 Mitigation and Site-Restoration Techniques..................................................................................52

4.2.1 Understanding Land User Preferences and Conflicts..........................................................52

4.2.2 Mitigating OHV Use Effects.......................................................................................................53

4.2.3 Restoration of OHV-Impacted Areas .......................................................................................54

5.0 Monitoring and Research Needs ...........................................................................................................55

5.1 Summary................................................................................................................................................55

5.2 Monitoring and Research Needs......................................................................................................56

5.2.1 Scientifically Rigorous Research Projects.............................................................................57

5.2.2 OHV Effects at Various Spatial and Temporal Scales, Across Habitat Types .................58

5.2.3 Research Regarding Effects of OHVs on Animal Populations ............................................58

5.2.4 Research to Determine Socioeconomic Costs Associated with OHV Use ......................59

5.2.5 Research to Improve Site Restoration ....................................................................................60

6.0 Conclusion..................................................................................................................................................60

7.0 Literature Cited ..........................................................................................................................................61

Appendix 1. Extensive Bibliographies .........................................................................................................83

1.1 OHV Effects on Soils and Watersheds.............................................................................................84

1.2 OHV Effects on Vegetation...............................................................................................................110

1.3 OHV Effects on Wildlife and Habitats: Native, Threatened, and Endangered Species ........131

1.4 OHV Effects on Water Quality .........................................................................................................165

1.5 OHV Effects on Air Quality................................................................................................................183

1.6 Socioeconomic Implications of OHV Use .....................................................................................192

Appendix 2. Search Methods and Results of Off-Highway Vehicle Effects Literature and Internet 

Resources.......................................................................................................................................................211

2.1 Methods...............................................................................................................................................211

2.1.1 Literature Search ......................................................................................................................211

2.1.2 Internet Search..........................................................................................................................211

2.2 Results .................................................................................................................................................216

2.2.1 Literature Resources ................................................................................................................216

2.2.2 Internet Resources ...................................................................................................................218

Figures 

2.1. Breakdown of unique Internet websites (n = 2,495) classified as “highly relevant” (H), 

“relevant” (R), “slightly relevant” (S), and “unrelated/unavailable” (U, Z) to off-highway 

vehicle effects and policies. .............................................................................................................219 

2.2. Focus areas of Internet websites (n = 333) classified as highly relevant to off-highway 

vehicle effects and policies. .............................................................................................................220 

2.3. Focus areas for all Internet websites (n = 1,230) classified as highly relevant, relevant, 

and somewhat relevant to off-highway vehicle effects and policies. ......................................220 

2.4. Focus areas of U.S. Bureau of Land Management Internet websites (n = 155) classified 

as highly relevant, relevant to off-highway vehicle effects and policies. ................................221 

vi 
2.5. Focus areas of U.S. Forest Service (regions 2 [Colorado only], 3, and 4 only) Internet 

websites (n = 176) classified as highly relevant to off-highway vehicle effects and policies.

................................................................................................................................................................222 

Tables 

2.1. Search terms used and publication years included when using search engines and 33 

electronic literature databases at Colorado State University’s library to assemble an 

extensive bibliography of literature on effects of off-highway vehicles. .................................212 

2.2. Search topics and their associated search terms used in searching the Internet for 

publications and documents pertaining to off-highway vehicle effects and policies. ..........216 

2.3. Relevance class codes and definitions pertaining to Internet websites found to contain 

information regarding off-highway vehicle effects and policies. ..............................................217 

2.4. Focus areas and definitions of Internet websites found to contain information regarding 

off-highway vehicle effects and policies........................................................................................217 

2.5. Number of relevant publications found, and publication dates included, in a literature 

search on effects of off-highway vehicle activity as they pertain to the U.S. Bureau of Land 

Management’s land health standards. ...........................................................................................218 

2.6. Search results, by topic, for all Internet websites pertaining to off-highway vehicle 

effects and policies (n = 22,990). ......................................................................................................219 

2.7. Internet websites classified as highly relevant, by focus area and source, pertaining to 

off-highway vehicle effects and policies........................................................................................223 

Tables 

3.1. Indicators emphasized in the literature reviewed for effects of off-highway vehicles 

(OHV) on land health compared to indicators of land health employed by the U.S. Bureau of 

Land Management (BLM) (Pellant and others, 2005). .....................................................44

 

vii 
Conversion Factors 

Inch/Pound to SI (International System of Units) 

Multiply By To obtain 

Length 

inch (in.) 2.54 centimeter (cm) 

inch (in.) 25.4 millimeter (mm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

yard (yd) 0.9144 meter (m) 

Area 

square foot (ft2) 929.0 square centimeter (cm2) 

square foot (ft2) 0.09290 square meter (m2) 

square inch (in2

) 6.452 square centimeter (cm2) 

square mile (mi2

) 2.590 square kilometer (km2) 

Volume 

cubic inch (in3) 16.39 cubic centimeter (cm3) 

cubic yard (yd3) 0.7646 cubic meter (m3) 

Mass 

ounce, avoirdupois (oz) 28.35 gram (g) 

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

ton, short (2,000 lb) 0.9072 megagram (Mg) 

ton, long (2,240 lb) 1.016 megagram (Mg) 

SI to Inch/Pound (English System of Units) 

Multiply By To obtain 

Length 

centimeter (cm) 0.3937 inch (in.) 

millimeter (mm) 0.03937 inch (in.) 

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi) 

meter (m) 1.094 yard (yd) 

Area 

square centimeter (cm2) 0.001076 square foot (ft2) 

square meter (m2) 10.76 square foot (ft2) 

square centimeter (cm2

) 0.1550 square inch (in2) 

square kilometer (km2

) 0.3861 square mile (mi2) 

Volume 

cubic centimeter (cm3) 0.06102 cubic inch (in3) 

cubic meter (m3) 1.308 cubic yard (yd3) 

Mass 

gram (g) 0.03527 ounce, avoirdupois (oz) 

kilogram (kg) 2.205 Pound, avoirdupois (lb) 

megagram (Mg) 1.102 ton, short (2,000 lb) 

megagram (Mg) 0.9842 ton, long (2,240 lb) 

viii 
Glossary 

ATV (All-Terrain Vehicle) Small, motorized 3- or 4-wheeled vehicles specifically designed for 

off-road use. The American National Standards Institute (ANSI) further defines an ATV 

as a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, 

and with handlebars for steering control. By the current ANSI definition, it is intended for 

use by a single operator, although a change to include 2-seaters (in tandem) is under 

consideration. Herein, the definition of ATV coincides with the description above and 

does not include passenger vehicles, including sport-utility vehicles or 4-wheel-drive 

jeeps. 

fugitive dust Dust raised by mechanical (anthropogenic) disturbance of granular material 

exposed to and becoming suspended in the air, then carried by wind. Arises from 

“nonpoint” sources—such as unpaved roads, agricultural tilling operations, aggregate 

storage piles, and heavy construction—rather than “point” sources—such as confined 

flow streams discharged to the atmosphere from a stack, vent, or pipe. 

indicator threshold For a given land health indicator (or set of indicators), the value(s) at or 

above which management action may be triggered or required. 

land health The condition of natural resource attributes, including soils and site stability, 

hydrologic function, and biotic integrity. 

OHV Defined herein as any civilian off-highway vehicle, including motorcycles, motorized dirt 

bikes, ATVs (see definition above), snowmobiles, dune buggies, 4-wheel-drive jeeps, 

sport-utility vehicles, and any other civilian vehicles capable of off-highway, terrestrial 

travel (including utility vehicles [UTVs] and ATVs with more than 4 wheels). 

OHV route Defined herein as any unpaved route created for OHV travel, including single-track 

paths or trails, two-tracks, and unimproved or improved dirt/gravel roads. Herein, this 

term is also applied to “rogue” (undesignated or unauthorized) routes created by OHV 

users in closed or limited areas. 

population dynamics Herein, used broadly to include wildlife or vegetation population size, 

density, and/or distribution (both spatial and temporal); rates of birth/germination, death, 

and/or survivorship; population gender/age-class structure; population genetics; and/or 

the rates/directions of change in all these parameters. 

right-of-way habitat Habitat provided within the legal description of a given transportation 

corridor.

sink population For a given metapopulation, a population sink is a local area or habitat where 

the local population’s reproductive rate is lower than the required replacement rate (in 

other words, a sink population is eventually extirpated without immigration of individuals 

from other areas). Population sinks often occur where there is excessive predation 

pressure and/or poor habitat quality. 

source population For a given metapopulation, a population source is a local area or habitat 

where the local population’s reproductive rate is greater than the required replacement 

rate. Excess individuals produced from a source population may emigrate to join sink 

populations, thereby keeping the sink populations from becoming extirpated. 

stream order A stream’s order is determined by its confluence with other streams: first-order 

streams are headwaters, the confluence of two first-order streams forms a second-order 

stream, the confluence of two second-order streams forms a third-order stream, and so on. 

ix 
Acknowledgments 

This project was funded by the U.S. Bureau of Land Management National Science and 

Technology Center, through Project Officer Victoria “Vicki” Josupait, as well as Travis Haby 

and Charisse Sydoriak. The authors would like to thank the following individuals for the time 

they offered in review, comment, and development of this document: Peter Doran, Travis Haby, 

Jeffery E. Herrick, Victoria “Vicki” Josupait, Mike “Sherm” Karl, David A. Pyke, James E. 

Roelle, Robert Stottlemyer, and Charisse Sydoriak. 

x 
Executive Summary 

This report and its associated appendixes compile and synthesize the results of a 

comprehensive literature and Internet search conducted in May 2006. The literature search was 

undertaken to uncover information regarding the effects of off-highway vehicle (OHV) use on 

land health, or “natural resource attributes,” and included databases archiving information from 

before OHVs came into existence to May 2006. Information pertaining to socioeconomic 

implications of OHV activities is included as well. The literature and Internet searches yielded 

approximately 700 peer-reviewed papers, magazine articles, agency and non-governmental 

reports, and internet websites regarding effects of OHV use as they relate to the Bureau of Land 

Management’s (BLM) standards of land health. Discussions regarding OHV effects are followed 

by brief syntheses of potential indicators of OHV effects, as well as OHV-effects mitigation, 

site-restoration techniques, and research needs. 

Terminology Used in This Report 

The BLM has definitions for several road and trail types; however, the OHV literature 

often uses somewhat different definitions. Whereas all terms are useful within their own 

contexts, herein the general term “OHV routes” is used to simplify discussions concerning all 

types of unpaved roads and trails, whether designated or unauthorized, and “roads” or 

“highways” are used to simplify discussions concerning paved roads. The definition of OHV also 

varies by agency and author, and to simplify discussions herein, OHV may include off-highway 

motorbikes, ATVs, dune buggies, snowmobiles, 4-wheel drive jeeps, motorcycles, some types of 

4-wheel drive automobiles (including sport-utility vehicles), and any other civilian vehicle 

specifically designed for off-road travel. OHV type or route/road type are specified if a given 

discussion warrants and if the literature cited in that discussion specified OHV type or route/road 

type. 

How to Use This Report 

Major sections of this document comprise a “manager’s report,” which includes a 

literature synthesis and related discussions of (1) OHV effects on natural resource attributes and 

socioeconomics; (2) indicators described in the literature to evaluate/monitor OHV effects on 

natural resource attributes and could serve as potential indicators in future research or monitoring 

programs; (3) mitigation and site-restoration techniques used for OHV-use areas; and (4) 

research and monitoring needs pertaining to OHV-effects. This document also includes extensive 

bibliographies pertaining to OHV effects on natural resources. It is recommended that readers 

focus first on the manager’s report, as it provides the basic understanding of OHV effects and 

potential approaches to researching, monitoring, and/or managing OHV effects. Reading the 

Executive Summary, the summaries provided in each section, and the conclusion may suffice for 

those seeking a quick overview. To facilitate a rapid review, section summaries are placed at 

the beginning of their respective sections and do not contain in-text citations. For a more 

in-depth review (with in-text citations), the entire manager’s report should be read.

Appendix 1 provides the extensive bibliographies, and Appendix 2 details the literature/Internet 

search methods and summarizes the search results (including tables and graphs). 

xi 
OHV Effects 

OHV Effects on Soils and Watersheds 

The primary effects of OHV activity on soils and overall watershed function include 

altered soil structure (soil compaction in particular), destruction of soil crusts (biotic and abiotic) 

and desert pavement (fine gravel surfaces) that would otherwise stabilize soils, and soil erosion. 

Indicators of soil compaction discussed in the OHV effects literature include soil bulk density 

(weight per unit of volume), soil strength (the soil’s resistance to deforming forces), and soil 

permeability (the rate at which water or air infiltrate soil). Generally, soil bulk density and 

strength increase with compaction, whereas permeability decreases with compaction. As soil 

compaction increases, the soil’s ability to support vegetation diminishes because the resulting 

increases in soil strength and changes in soil structure (loss of porosity) inhibit the growth of root 

systems and reduce infiltration of water. As vegetative cover, water infiltration, and soil 

stabilizing crusts are diminished or disrupted, the precipitation runoff rates increase, further 

accelerating rates of soil erosion. 

OHV Effects on Vegetation 

Plants are affected by OHV activities in several ways. As implied above, soil compaction 

affects plant growth by reducing moisture availability and precluding adequate taproot 

penetration to deeper soil horizons. In turn, the size and abundance of native plants may be 

reduced. Above-ground portions of plants also may be reduced through breakage or crushing, 

potentially leading to reductions in photosynthetic capacity, poor reproduction, and diminished 

litter cover. Likewise, blankets of fugitive dust raised by OHV traffic can disrupt photosynthetic 

processes, thereby suppressing plant growth and vigor, especially along OHV routes. In turn, 

reduced vegetation cover may permit invasive and/or non-native plants—particularly shallowrooted annual grasses and early successional species capable of rapid establishment and 

growth—to spread and dominate the plant community, thus diminishing overall endemic 

biodiversity. 

OHV Effects on Wildlife and Habitats: Native, Threatened, and Endangered Species 

Habitats for native plants and animals, including endangered and threatened species, are 

impacted by OHVs in several ways. A salient effect is habitat fragmentation and reduced habitat 

connectivity as OHV roads and trails proliferate across the landscape. Reduced habitat 

connectivity may disrupt plant and animal movement and dispersal, resulting in altered 

population dynamics and reduced potential for recolonization if a species is extirpated from a 

given habitat fragment. Wildlife is also directly affected by excessive noise (decibel levels/noise 

durations well above those of typical background noise) and other perturbations associated with 

OHV activities. Disturbance effects range from physiological impacts—including stress and 

mortality due to breakage of nest-supporting vegetation, collapsed burrows, inner ear bleeding, 

and vehicle-animal collisions—to altered behaviors and population distribution/dispersal 

patterns, which can lead to declines in local population size, survivorship, and productivity. 

OHV Effects on Water Quality 

The effects of OHV activities on water quality can include sedimentation (deposited 

solids), turbidity (suspended solids), and pollutants within affected watersheds. Sedimentation 

increases because compacted soils, disrupted soil crusts, and reduced vegetation cover can lead 

to increased amounts and velocities of runoff; in turn, this accelerates the rates at which 

xii 
sediments and other debris are eroded from OHV-use areas and flushed to aquatic systems 

downslope. Pollutants associated with deposition of OHV emissions and spills of petroleum 

products may be adsorbed to sediments, absorbed by plant material, or dissolved in runoff; once 

mobilized, these contaminants may enter aquatic systems. 

OHV Effects on Air Quality 

Air quality is affected when OHV traffic raises fugitive dust and emits by-products of 

combustion. Because wind can disperse suspended particulates over long distances, dust raised 

by OHV traffic can blanket plant foliage and disperse dust-adsorbed contaminants well beyond a 

given OHV-use area. Primary combustion by-products potentially affecting air quality in OHVuse areas include (but are not limited to) polycyclic aromatic hydrocarbons, sulfur dioxide (SO2), 

nitrogen oxides (NOx), and ozone (O3). Although leaded gasoline has not been used in the United 

States since 1996, lead emissions deposited prior to the ban on leaded gasoline may persist for 

decades and continue impacting ecosystems as wind and water erosion continue to mobilize lead 

and other contaminants downwind (or downslope) of contaminated soils. 

Socioeconomic Implications of OHV Use 

For the purposes of this document, the socioeconomics of OHV use include (1) OHV 

user demands, concerns, and attitudes; (2) the economic effects of OHV use on communities 

near OHV-use areas; (3) and the effects of OHV use on other land users. Although not one of 

BLM’s land health considerations, the socioeconomic implications of OHV use have significant 

direct and indirect effects on land health. As the popularity of OHV recreation increases, 

socioeconomic factors become increasingly important considerations in understanding and 

mitigating the overall effects of OHV use on land health. OHV recreation can have significant 

economic value to local communities where and when OHV use is popular; however, the 

economic costs to those communities remain unknown. OHV use also can lead to conflicts 

among different land users—both OHV users and people seeking non-motorized forms of 

recreation—within OHV-use areas and nearby areas. Crowding of designated OHV areas may 

encourage unauthorized use in closed areas, and adjacent or overlapping use types may cause 

dissatisfaction or discourage recreation altogether, which can diminish public support for landmanagement programs. 

Potential Indicators (Both Direct and Indirect) for Evaluating and Monitoring OHV 

Effects 

Soil Health and Watershed Condition 

• Soil strength 

• Soil bulk density 

• Soil permeability (rates of air and water infiltration) 

• Erosion rate 

• Level of sedimentation or turbidity in wetlands 

• Surface changes (for example, gully erosion) 

• Presence/condition of soil crusts 

Vegetation Health 

• Plant community composition (including species and structural diversity, 

ratio of native to non-native or invasive species) 

• Abundance of individuals and/or stem density 

xiii 
• Percent vegetation cover 

• Plant size 

• Growth rate 

• Biomass 

Habitat Condition and Health of Wildlife Populations (including indirect indicators) 

• Habitat patch size and connectivity 

• Community composition (including species diversity, ratio of native to 

non-native or invasive species) 

• Population size, density, and trend 

• Spatiotemporal distribution of populations 

• Survivorship and mortality rates 

• Productivity and body mass 

• Age-class and gender structure 

• Frequency of OHVs passing through a given area and associated wildlife 

mortalities rates 

• Road or trail type and width 

• Level (decibels), duration, and timing of traffic noise 

Water Quality

• Sedimentation rate 

• Levels of turbidity and suspended solids 

• Contaminant levels, including petroleum-derived compounds from spills 

and emissions, such as benzene; ethylbenzene; m-, p-, and o-xylene; 

toluene; 1,3-butadiene; and lead 

Air Quality

• Level of dust particulates 

• Particulate levels of OHV emission by-products, such as polycyclic 

aromatic hydrocarbons, aldehydes, carbon monoxide, nitrogen oxides, 

ozone, and sulfur oxides 

Socioeconomics

• User satisfaction with recreation experiences 

• User compliance with OHV (or other) regulations 

• User knowledge regarding effects of recreation activities on various 

aspects of land health 

• Distribution and intensity of OHV versus non-motorized recreation and 

other land uses 

• Extent to which unauthorized trails are created and damage to vegetation 

occurs 

• Trends in local economic indicators associated with OHV and nonmotorized recreation and other land uses, such as sales of camping 

equipment, gasoline, restaurants, lodging facilities 

Mitigation and Site-Restoration Techniques 

Balancing OHV-user preferences with protecting land health and the needs of other land 

users requires careful study and planning, as well as appropriate management strategies. Prior 

planning for locating OHV areas before they are opened to the public can preclude undesirable 

xiv 
effects of OHV use and costly site restoration. Once a site has been used, however, trail/area 

closures, signage, and other visual cues, as well as enforcement and limiting visitor numbers 

through “rationing,” are among the tools used to preclude additional effects. 

Because habitat fragmentation is particularly difficult to repair, planning and 

management designed to maintain habitat connectivity are crucial to minimize fragmentation. 

Variation in impacts requires various restoration techniques. Whereas a single OHV pass on a 

xeric landscape may cause long-lasting damage, a similar single pass on a mesic landscape may 

require no treatment at all. Restoration approaches may include replacing native soil where 

erosion has removed the topsoil and exposed the underlying bedrock, seeding with indigenous 

plants, inoculating soils with native microbes and mycorrhizae, scarifying, and/or mulching. 

Ultimately, the success of such measures depends on the nature and intensity of the disturbance, 

topography, soil type, climate, and the ability of land managers to enforce closures and prevent 

the proliferation of new routes. 

Monitoring and Research Needs to Support OHV Management Decisions 

Elucidating OHV impacts on soils and watersheds, vegetation, wildlife and their habitats, 

water and air quality, and/or socioeconomics, whether through monitoring or experimental 

research studies, will require careful planning and appropriate, rigorous study design. Results of 

many past ecological studies on the effects of OHVs may be regarded as preliminary, 

particularly for those that lacked comparable treatment and control sites and site replication. 

Overall, the reliability and value of monitoring and research results would increase significantly 

by including a broad range of spatial and temporal scales—from microhabitat to landscape or 

ecosystem scale, and from short-term (seasonal) to long-term (decades)—within the full range of 

impacted habitat types represented on BLM lands. The full array of site types also needs 

evaluation, including designated OHV-use sites, undesignated (rogue) OHV-use sites, unused 

areas, and restoration sites. Multiple- and simultaneous-assessment techniques that take 

advantage (and push the advancement) of existing and emerging technologies are needed to fully 

represent the scale and diversity of OHV impacts on the abiotic and biotic components of 

affected lands and communities, and to ascertain indicator thresholds as they pertain to BLM’s 

land health standards. More specifically, monitoring and research needs pertaining to OHV use 

and impacts include (but are not limited to) 

• well-designed monitoring programs and experimental studies that incorporate planned 

comparisons of treatment (OHV-impacted) and control (unimpacted/reference) sites; 

• before and after OHV-impact studies; 

• studies at various spatial and temporal scales across all impacted habitat types; 

• studies on habitat fragmentation and road-edge effects caused by OHV activities; 

• studies on various gradients in OHV disturbance at various distances from OHV routes; 

• studies to improve the understanding of the physical and chemical dynamics of soil 

compaction; 

• studies evaluating the effects of erosion, sedimentation, and turbidity at both local 

(immediately downslope of OHV-affected sites) and landscape (throughout impacted 

watersheds) scales; 

• studies of OHV effects on plant and animal population dynamics; 

• simultaneous evaluations of wildlife responses and OHV route-specific variables; 

• improvements in techniques for successful site restoration; 

xv 
xvi 

• improvements in techniques and technologies for assessing OHV impacts over large 

areas and long periods of time; 

• effectiveness evaluations of various techniques to manage OHV use and its ecological 

and socioeconomic effects while simultaneously providing the greatest satisfaction 

among all land users; and 

• studies that determine the economic and sociological costs of OHV use. 
1.0 Introduction 

1.1 Issue Context: Bureau of Land Management Land Health and Off-highway 

Vehicle Use 

1.1.1 Bureau of Land Management Land Health Standards 

In the mid-1990s, Rangeland Health: New Methods to Classify, Inventory, and Monitor 

Rangelands was published to examine the scientific basis and success of methods used by federal 

agencies to inventory, classify, and monitor rangelands, and to make recommendations for 

improvements to these methods (Committee on Rangeland Classification, Board on Agriculture, 

and National Research Council, 1994). Therein, rangeland health was defined as “...the degree 

to which the integrity of the soil and the ecological processes of rangeland ecosystems are 

sustained.” In 2001, the BLM published Rangeland Health Standards, a process framework for 

assessing rangeland health via interdisciplinary teams that, at a minimum, would evaluate (1) 

watershed function; (2) nutrient cycling and energy flow; (3) water quality; (4) habitat for 

endangered, threatened, proposed, candidate, or special status species; and (5) habitat quality for 

native plant and animal populations (U.S. Bureau of Land Management, 2001). Subsequently, it 

was clarified that the term “rangeland” is interchangeable with “land” and that “...‘the rangeland 

health standards’ really apply to the condition of the land itself regardless of the uses that may 

influence the health of that land” (U.S. Bureau of Land Management, 2007). In other words, the 

standards for rangeland health apply to all BLM lands, whether used for grazing, off-highway 

vehicle (OHV) recreation, or any other use permitted to occur on BLM lands. 

The standards of rangeland health establish minimum resource conditions that must be 

achieved and maintained to ensure the “proper functioning condition” (see Barrett and others, 

1995)—both physical and biological—and sustainability of BLM lands. These standards, 

however, must be relative to the native conditions for a given “reference site,” as native 

conditions vary widely among sites on BLM lands. For example, the BLM defines healthy soils 

in northwest California as “exhibit[ing] characteristics of infiltration, fertility, permeability rates, 

and other functional and physical characteristics that are appropriate to soil type, climate, desired 

plant community, and land form” (personal communication from M. Karl to V. Josupait, U.S. 

Bureau of Land Management, Denver, Colorado, May 2001). 

The BLM’s technical reference on Interpreting Indicators of Rangeland Health

recognizes three broad categories of natural resource attributes for assessing land health: (1) soils 

and site stability, (2) hydrologic function, and (3) biotic integrity (Pellant and others, 2005). 

Relative to off-highway vehicle (OHV) impacts on ecosystem health, soil/site stability and 

hydrologic or watershed function pertain (but are not limited) to erosion and extent of surface 

changes and patterns of water flow, including infiltration. Biotic integrity pertains to community 

structure and functionality of plants. Within these three categories, overall land health is 

qualitatively assessed via 17 parameters (or indicators) that indicate the presence, number, 

extent, percent, and/or depth or height of (1) rills, (2) water flow patterns, (3) erosional 

pedestals/terracettes, (4) bare ground, (5) gullies and gully erosion, (6) wind scoured blowouts 

and/or depositional areas, (7) litter movement, (8) soil surface resistance to erosion, (9) soil 

surface structure and content of soil organic matter (SOM), (10) effect of plant community 

composition and spatial distribution on infiltration and runoff, (11) compaction layer, (12) 

dominance hierarchy of functional/structural groups in plant communities, (13) mortality and 

1 
decadence among plant functional groups, (14) litter cover, (15) expected above-ground annual 

production, (16) potential invasive species, and (17) perennial plant reproductive capability 

(Pellant and others, 2005). Many of the indicators listed above may be assessed in terms of the 

condition and extent of abiotic (chemical) and biotic soil crusts, and soil surfaces of small stones 

known as “desert pavement,” as they help stabilize soils and/or cycle nutrients through the 

system. Indicators 1-11 largely pertain to soil/site stability and hydrologic/watershed function, 

whereas parameters 12-17 are primarily indicators of biotic integrity, although there is overlap 

among the two groups. 

1.1.2 Increasing OHV Use 

An important factor affecting the health of BLM lands is the use of OHVs. In 1993, 

2,920,000 all-terrain vehicles (ATVs) and off-highway motorcycles were estimated to be in use 

(Cordell and others, 2005). Between 1995 and 2003, sales of ATVs and off-highway motorcycles 

tripled, increasing the number of ATVs and off-highway motorcycles in use to 8,010,000 

(Cordell and others, 2005). Because the popularity of OHV-based recreation is relatively recent 

and still increasing (see Matchett and others, 2004), the full range of short- and long-term 

impacts has yet to be fully realized or understood. Overall, it is clear that OHV use on public 

lands is and will continue to be an important management issue. 

1.2 Objectives, Scope, Organization, and Use of This Report 

1.2.1 Objectives 

The objectives of this report are twofold. This first is to synthesize the results of a 

comprehensive literature search on what is currently known about the effects of OHV activities 

as they relate to the BLM’s land health standards (U.S. Bureau of Land Management, 2001). 

These discussions include socioeconomic implications of OHV use—including preferences of 

OHV users, effects of OHV activities on other land users, and the economic impacts of OHV 

recreation on local economies—because understanding these factors and incorporating that 

knowledge into management plans and policies will be crucial to management success. The 

second objective is to discuss the indicators of land health and socioeconomics described in the 

OHV effects literature, as they have potential usefulness for evaluating or monitoring lands and 

land users affected by OHV use. This report also contains brief overviews of mitigation 

approaches, site-restoration techniques, and monitoring and research needs described in the 

OHV-effects literature. 

1.2.2 Geographical Scope 

Although the vast majority of literature and other sources consulted address OHV 

impacts on ecosystems in the western United States, there are a number of useful references that 

address OHV use or impacts of roads in other parts of the United States and in other countries. 

Some of these sources have been included to provide additional information not provided 

elsewhere and/or to broaden the scope and relevance of this document. 

1.2.3 Organization 

The main body of this document—referred to herein as the “manager’s report” 

(Executive Summary and Sections 1-7)—includes the literature synthesis of OHV effects; 

annotated bibliographies that typify the body of research regarding effects of OHV activities on 

BLM’s land health standards; sections regarding indicators of OHV effects, mitigation and site2 
restoration techniques, and monitoring and research needs; and a listing of all literature cited in 

the manager’s report. To facilitate the logical flow of information, the natural resource attributes 

addressed in BLM’s land health standards serve as the underlying organizational structure of all 

major sections in the report, as indicated by parallel subsection headings pertaining to (1) soils 

and watersheds, (2) vegetation, (3) habitat for native plants and wildlife, (4) water quality, and 

(5) air quality. Although not part of the BLM’s land health agenda, a sixth subsection has been 

included in each major section to address the socioeconomic considerations of OHV use, 

because, ultimately, it is socioeconomic factors (including conflicts among land users, 

preferences of OHV users, and economics of OHV use) that drive changes in overall land health. 

1.2.4 Tips on Navigating This Document 

It is recommended that readers focus first on the manager’s report, as it provides the basic 

understanding of OHV effects and possible indicators to use in research, monitoring, and/or 

management programs. Reading the Executive Summary, subsection summaries, and the overall 

conclusion may suffice for those seeking a quick overview. For quick and easy reference, 

subsection summaries on OHV effects are placed at the top of their respective subsections. 

In-text citations were purposely left out of all summaries to enhance readability. For a 

more in-depth, fully cited review, reading the entire manager’s report is recommended. 

Appendixes 1 and 2 provide further information and more extensive resources for those 

needing high levels of detail. The Extensive Bibliographies (Appendix 1) includes the 

approximately 700 publications and reports uncovered through the literature search (from 1960 

to May 2006) that pertain to effects of OHV use. Appendix 2 details the literature- and Internetsearch methods and provides tabular and graphical summaries of literature, websites, and 

associated resources, as they pertain to OHV effects on natural resources and related policies. 

1.3 Definitions of OHV Routes/Roads, Vehicles, and Activities 

1.3.1 Definitions of Roads and Trails Used in This Report 

BLM’s Roads and Trails Terminology document (U.S. Bureau of Land Management, 

2006) defines (1) a road as “a linear route declared a road by the owner, managed for use by lowclearance vehicles having four or more wheels, and maintained for regular and continuous use;” 

(2) a primitive road as “a linear route managed for use by four-wheel drive or high-clearance 

vehicles;” and (3) a trail as “a linear route managed for human-powered, stock, or off-highway 

vehicle forms of transportation or for historical or heritage values.” Bolling and Walker (2000) 

offer more detailed definitions of unpaved roads and trails: (1) graded, improved roads are those 

from which the topsoil has been removed by bulldozer and characterized by the presence of 

lateral berms; (2) unimproved roads are those not graded consistently; (3) jeep trails are fourwheel drive tracks impacted only by vehicular traffic and generally characterized by a center 

berm; and (4) single tracks are severely compacted trails generated by OHVs. 

The literature includes numerous reviews on the ecological effects of paved as well as 

unpaved roads (see Andrews, 1990; Forman and Alexander, 1998; Spellerberg, 1998; Trombulak 

and Frissell, 2000). Ecosystems of the West, however, are especially vulnerable to OHV-related 

activities on unpaved (gravel or dirt) roads and trails due to the effects they impose on soils and 

vegetation, which may take centuries to recover (Webb, 1982; Lovich and Bainbridge, 1999). 

Furthermore, unpaved roads comprise the majority of OHV routes used throughout public lands 

in the western United States. Therefore, the primary considerations in this report are unpaved 

3 
roads and trails. References and discussions regarding effects of paved roads are not entirely 

excluded, however, as they often inform the potential scope of OHV effects not otherwise 

addressed. When necessary to do so, the type of road is specified. 

All of terms described above for roads and trails are useful within their own contexts, but 

to distinguish between them and those used in the OHV literature would unnecessarily 

complicate discussions herein. Therefore, except where there is a need to specify in more detail, 

unpaved roads, primitive roads, and unpaved trails, are referred to as “routes,” regardless of their 

intended purpose or how they are maintained. “Routes” also include unauthorized or “rogue” 

roads and trails created by OHV users traveling off officially designated roads, primitive roads, 

and trails. Paved roads are referred to as “roads.” 

1.3.2 Definitions of OHVs and OHV Activities Used in This Report 

BLM’s Roads and Trails Terminology document (U.S. Bureau of Land Management, 

2006) defines an OHV as “any motorized vehicle capable of—or designated for—travel on or 

immediately over land, water, or other natural terrain” (excluding nonamphibious registered 

motorboats; military, fire, emergency, or law enforcement vehicles used for emergency purposes; 

official vehicles used expressly by an authorized officer; and military vehicles). Cordell and 

others (2005) further specify that OHVs may include motorcycles and off-highway motorbikes, 

ATVs, dune buggies, snowmobiles, most 4-wheel drive automobiles (jeeps, sport utility 

vehicles), and any other civilian vehicle specifically designed for off-road travel. For the purpose 

of this document, OHV is defined in accordance with BLM terminology and includes those 

vehicles listed by Cordell and others (2005), as well as utility vehicles (UTVs) and ATVs with 

more than 4 wheels. 

There are numerous activities and outcomes directly and indirectly associated with OHV 

use. To simplify discussions of OHV activities herein, the term “OHV activities” largely refers to 

driving OHVs for recreation. In certain contexts, OHV activities also may include driving and 

parking vehicles that tow trailers carrying OHVs and loading and unloading OHVs from trailers. 

Whereas the use of 4-wheel drive jeeps, automobiles, and sport utility vehicles is largely 

restricted to unpaved roads and jeep trails, the effect of ATVs and off-highway motorcycles 

extends well beyond them to double- and single-track trails, as well as unauthorized roads and 

trails. Thus, “OHV activities” may include driving OHVs on authorized roads/routes and on (or 

creating) unauthorized routes. 

2.0 Effects of OHV Travel on Natural Resource Attributes and 

Socioeconomics 

2.1 Scale and Patterns of OHV Activities and Their Effects 

Temporal and spatial scales are crucial considerations when evaluating or monitoring 

effects of any factor on ecosystems (Noon, 2003; Ringold and others, 2003). In discussing OHV 

effects on desert ecosystems, Brooks and Lair (2005) and Matchett and others (2004) describe 

the impacts of OHV activities at various spatial and temporal scales. At the highly localized 

spatial scale, one might find soil compaction taking place within the confines of a single OHV 

route, the effects of which might be limited to poor infiltration of water and reduced plant cover 

in the route itself. Brooks and Lair (2005) go on to explain, however, that the cumulative impacts 

of any one effect at many sites can result in impacts at much greater scales. For example, if 

4 
networks of OHV routes criss-cross large areas, the habitat connectivity that previously 

facilitated animal movements within that landscape may be disrupted (Forman and others, 2003: 

p. 129-134). Similarly, a single pass by one OHV probably has negligible effects on animal 

distributions, but if OHV traffic is intense and chronic, animal densities may decline (Reijnen 

and others, 1995, 1997) as cumulative impacts of this one effect occurring at many sites across a 

landscape disrupt entire populations. Furthermore, any direct effect of OHV use is also likely to 

have indirect effects that go beyond the site of disturbance. For example, reduced plant cover 

(direct effect) can result in greater rates of erosion in and around an OHV route, which, in turn, 

might increase sedimentation and turbidity in wetlands downslope of the route (indirect effect). 

Overall, Brooks and Lair (2005) conclude that effects of OHV use need to be evaluated at 

appropriate scales, which must take into account the scale at which OHV activities and 

ecosystem responses occur (Brooks and Lair, 2005). Overall, most, if not all, effects of OHV 

activities described in sections 2.2 through 2.6 can occur from the very localized and/or 

ephemeral scale to the landscape and/or long-term scale. By the same token, any direct effect 

may have a number of indirect effects, the magnitude of which may depend on the spatial and 

temporal scales at which a direct effect occurs. 

At an OHV site in California, Matchett and others (2004) classified OHV routes in terms 

that describe intensity and pattern of use. First, OHV lines (routes) were categorized as either 

dirt (lines most likely created for or by OHV use) or as wash (lines most likely created by water 

flow, but possibly used by OHVs). They went on to define levels of OHV use that also imply 

patterns of use: (1) densely tracked reticulate (OHV lines evident in a web-like pattern, but too 

dense and overlapping to distinguish individually); (2) densely tracked hill-climb (OHV lines 

evident on slopes, but too dense and overlapping to distinguish individually; (3) densely tracked 

intersection (OHV lines evident at intersections, but too dense and overlapping to distinguish 

individually; (4) densely tracked right-of-way (OHV lines evident near pipelines, transmission 

lines, and highway right-of-ways, but too dense and overlapping to distinguish individually; (5) 

densely tracked wash (OHV lines evident within washes, but too dense and overlapping to 

distinguish individually; (6) denuded hill-climb (OHV lines not readily evident on hill-climbs, 

but the preponderance of densely tracked areas in the vicinity indicate that OHV use was 

probably high within that area); and (7) denuded staging (OHV routes not readily evident in 

relatively flat camping areas, but the preponderance of densely tracked areas in the vicinity 

indicated that OHV use was probably high within that area) (Matchett and others, 2004). Overall, 

these categories indicate that OHV use often entails many criss-crossing routes as opposed to a 

single route. They also point out that OHV use may be heaviest on slopes, along right-of-ways, 

in washes, and in the vicinity of camping facilities. 

2.2 OHV Effects on Soils and Watersheds 

2.2.1 Section Summary 

Important effects of OHV activities on soils and watershed function include soil 

compaction, diminished water infiltration, diminished presence and impaired function of soil 

stabilizers (biotic and abiotic crusts, desert pavement), and accelerated erosion rates. Compacted 

soil inhibits infiltration of precipitation. In turn, soil moisture available to vegetation is 

diminished, volumes and velocities of precipitation runoff increase, and soil erosion accelerates, 

leading to the formation of gullies and other surface changes. Additionally, soil compaction may 

inhibit root growth among plants, in which case organic matter, litter, soil fertility, and 

vegetative cover are diminished, further exacerbating the soil’s susceptibility to erosion. Where 

5 
biotic and chemical crusts or other soil stabilizers are disturbed or destroyed, soil erosion from 

water and wind may increase beyond rates found in undisturbed sites with similar soils and 

conditions; nutrient-cycling processes also are likely to be disrupted, potentially leading to 

declines in soil fertility. 

2.2.2 Soil Compaction and Reduced Water Infiltration 

One of the most common and important effects of OHV activities is soil compaction 

(Liddle, 1997), which diminishes water infiltration, destroys soil stabilizers (biotic and abiotic 

crusts, desert pavement), and promotes greater rates of erosion from water and wind. In turn, soil 

moisture available for plant growth is diminished, precipitation runoff increases in volume and 

velocity, and soil erosion accelerates, which leads to surface changes, including the formation of 

rills, gullies, terracettes, and pedestals (Webb and others, 1978; Iverson and others, 1981; Webb, 

1982; Hinckley and others, 1983; Wilshire, 1983b). The extent of soil compaction may be 

measured in terms of soil bulk density, soil strength, and/or permeability. Soil bulk density, 

calculated as oven-dried soil weight per unit of volume, is typically expressed as g/cm3

 or g/cc. 

Soil strength, measured as the soil’s resistance to deforming forces—or the amount of energy 

required to break apart aggregates or move implements through the soil—is typically expressed 

as kg/cm2

 or pounds per square inch (PSI). Soil permeability is the rate at which water (or air) 

infiltrates the soil, expressed as cm/hr or inches/hr (Leung and Meyer, 2004). Generally, soil 

bulk density and strength increase with increasing compaction, whereas permeability decreases 

with increasing compaction (Adams and others, 1982; Webb, 1982; Cole, 1990). 

Important factors affecting a soil’s susceptibility to compaction include its (1) texture 

(relative proportions of sand, silt, and clay); (2) structure (the grouping of sand, silt, and clay 

particles into aggregates), including its porosity (a measure of pore space, which affects the 

amount of air or water a soil can hold) and aggregate stability (the ability of soil aggregates to 

resist disruption from outside forces—water in particular); (3) type (series) and depth; and (4) 

antecedent moisture (the soil’s water content prior to compaction). Sandy or clayey soils 

relatively uniform in texture and structure are less vulnerable to compaction than loamy sands or 

coarse-textured, gravelly soils characterized by variability in particle size (Lovich and 

Bainbridge, 1999). In addition, soils with greater water content are more susceptible to 

compaction than those containing less moisture (Webb, 1982), although even in semi-arid and 

arid lands soil compaction is problematic because the texture of these soils is slow to recover 

(Webb, 1982) through natural soil-loosening processes (including shrinking, swelling, drying, 

wetting, freezing, and thawing). 

As the number of vehicle “passes” (one pass is the equivalent of one OHV passing over a 

given area one time) increases, soil bulk density and soil strength increase and permeability (as 

indicated by water infiltration rate) decreases (Lovich and Bainbridge, 1999). Soil compaction 

may become evident after only a few vehicle passes. In fact, Iverson and others (1981) found that 

soil bulk density increased logarithmically with the number of vehicle passes. Similarly, Adams 

and others (1982) report that soil strength on routes subjected to a single vehicle pass was 5.3 to 

28.4 kg/cm2

 (75.366 to 403.848 PSI) greater (depending on the percent soil moisture) than that of 

nearby undisturbed soils; after 10 to 20 passes, soil strength was too great (impenetrable) to 

measure with a penetrometer, indicating that a few passes were enough to cause soil 

“cementation.” After initial disturbance, the effects of soil compaction can persist for years, even 

centuries, before natural soil-loosening processes can restore the soil’s texture (Webb and 

Wilshire, 1980; Webb, 1982; Froehlich and others, 1985; Prose, 1985; Lovich and Bainbridge, 

1999). For example, one year after impact, a one-pass trail was still faintly visible, as indicated 

6 
by slightly more surface gravel and growth of annual plants (the first to grow in disturbed sites) 

than on surrounding land, and trails impacted by 100 and 200 passes had notable side berms 

(Prose, 1985). 

Other effects of soil compaction include changes to soil horizons and increased 

compaction in deeper strata. The OHV traffic associated with the annual Johnson Valley-Parker 

OHV race (1980-1983) near Joshua Tree National Park on the Colorado River compacted 2 to 5 

cm (0.8 to 2.0 in) of the underlying vesicular soil horizon (composed of fined-grained, windblown material occurring about 20 cm [7.9 in] deep near surface soil horizons, often immediately 

under desert pavement, and characterized by small pores, or vesicles, of air space; typical of arid 

regions) and caused excavation (mechanical erosion) of the A and B soil horizons to depths of 20 

cm (7.9 in) (Wilshire, 1983a). Prose (1985) found that resistance (to a penetrometer) of soil 

affected by military maneuvers (including tanks, tracked equipment and personnel carriers, and 

support vehicles) was 50 percent greater than that of undisturbed soils. Overall, traffic typically 

causes significant changes to soils, which may take years, if not decades, to recover. 

2.2.3 Effects on Soil Stabilizers and Rates of Soil Erosion 

A significant effect of soil compaction is the soil’s inability to support vegetation after 

disturbance, thus increasing its susceptibility to erosion (Webb and others, 1978). Soil erosion 

resulting from soil compaction is caused by two main factors (Hinckley and others, 1983): 

reduced infiltration rates and destruction of soil stabilizers. Infiltration of water into soils 

depends, to a large extent, on the soil’s porosity, which is reduced by compaction. Soil 

stabilizers, which are characteristic of undisturbed desert substrates, may include cryptobiotic 

crusts of lichen, fungi, bacteria, mosses, and/or algae; chemical or mechanical crusts (thin upper 

coating of clay particles oriented parallel to the surface); and desert pavements (closely packed, 

interlocking fragments of pebble- and/or cobble-sized rocks from which fine-grained materials 

have been removed by wind or water erosion) (Lovich and Bainbridge, 1999). Cryptobiotic 

organisms facilitate accumulation of organic materials and nutrients, including nitrogen and 

carbon, thereby increasing soil fertility (Johansen, 1993). Since they occur in the soil’s upper 

layer, they also promote water infiltration and enhance retention of soil moisture (Belnap and 

Gardner, 1993). Their proximity to the surface, however, makes them susceptible to destruction 

by vehicular and foot traffic. 

Cole (1990) documented destruction of cryptogamic soil crusts after only 15 passes by 

hikers wearing lug-soled boots. Traffic from the Johnson Valley-Parker OHV race mentioned in 

section 2.2.2 not only destroyed the vesicular soil horizon, it destroyed the overlying desert 

pavement (Wilshire, 1983a). Webb (1982), who evaluated soil surfaces (shape; another measure 

of soil compaction) after 1, 10, 100, and 200 motorcycle passes, found changes occurring after 

the first few passes, although the effects of subsequent passes were more severe due to their 

cumulative effects: routes subjected to 100 and 200 passes were characterized by berms and 

lateral edges, and route midlines were 10-30 mm below the level of surrounding undisturbed 

ground. Once damaged or destroyed, it may take 300-500 years per inch for soil stabilizers to 

recover or return to their original state (Hudson, 1971). 

Typically, undisturbed soil surfaces are very important in controlling the soil’s response 

to precipitation runoff, particularly where the soil surface is covered with fine gravel that 

overlays soils with large pores (Webb, 1982). In the Mojave Desert, surface runoff was typically 

five times greater and sediment yield (in runoff) was 10-20 times greater in OHV-impacted areas 

than in undisturbed areas (Iverson and others, 1981). For various reasons, certain portions of the 

desert, including dunes, playas, and areas covered with coarse surface material, are fairly 

7 
resistant to erosion from runoff (Hinckley and others, 1983), whereas vulnerable areas are those 

where initial infiltration rates are low, slopes are high, and ratios of surface sand/gravel to 

smaller particles are low (Iverson and others, 1981). The character of precipitation also 

influences the susceptibility of denuded soil to erosion; erosion rates are typically greater when 

rainfall events are of long duration and high intensity (Iverson and others, 1981). Disturbed soils 

also increase the likelihood of debris eroding from areas disturbed by OHV activities (Lovich 

and Bainbridge, 1999). Indeed, debris flow has been documented to bury plants growing outside 

the area impacted (Nakata, 1983). 

2.2.4 Annotated Bibliography for OHV Effects on Soils and Watersheds 

Adams, J.A., Endo, A.S., Stolzy, L.H., Rowlands, P.G., and Johnson, H.B., 1982, Controlled 

experiments on soil compaction produced by off-road vehicles in the Mojave Desert, California: 

Journal of Applied Ecology, v. 19, no. 1, p. 167–175. 

Under controlled conditions, soil crust properties were measured to determine how 

rapidly they were altered by passing vehicles. Routes impacted by a single vehicle pass had soil 

strengths 5.3 to 28.4 kg/cm2

 (75.366 to 403.848 lb/in2 [or PSI], depending on the percent soil 

moisture) greater than undisturbed soil, indicating that just a single pass can begin to affect soil 

strength. Mean soil strength on routes exposed to 10 and 20 passes was too high to measure. 

Drying caused the soil in the slightly compacted track to become much harder (increased soil 

strength) than the undisturbed soil. 

Belnap, Jayne, 1993, Recovery rates of cryptobiotic crusts—inoculant use and assessment 

methods: Great Basin Naturalist, v. 53, no. 1, p. 89–95. 

Rates of recovery of cyanobacterial-lichen soil crusts from disturbance were examined. 

Plots were either undisturbed or scalped, and scalped plots were either inoculated with 

surrounding biological crust material or left to recover naturally. Natural recovery rates were 

found to be very slow. Inoculation significantly hastened recovery of the cyanobacterial/green 

algal component, lichen cover, lichen species richness, and moss cover; even with inoculation, 

however, lichen and moss recovery was minimal. 

Belnap, Jayne, 2002, Impacts of off-road vehicles on nitrogen cycles in biological soil crusts—

resistance in different U.S. deserts: Journal of Arid Environments, v. 52, no. 2, p. 155–165. 

This study was conducted to evaluate short-term impacts of OHVs on lichen cover and 

the nitrogenase activity (NA) of biological soil crusts on various soil types in the Great Basin, 

Colorado Plateau, Sonoran, Chihuahuan, and Mojave deserts. Lichen cover was significantly 

correlated with percent silt in soil (and negatively correlated with percent sand and clay). 

Disturbance reduced NA at all 26 sites, but significantly at 12; declines were greatest in soils of 

cooler regions than hotter ones, possibly indicating that non-heterocystic cyanobacterial species 

are more susceptible to disturbance than heterocystic species. Sandy soils showed greater 

reduction of NA as sand content increased, while fine-textured soils showed a greater decline as 

sand content increased. At all sites, higher NA before the disturbance resulted in less impact to 

NA post-disturbance. These results may be useful in predicting the impacts of off-road vehicles 

in different regions and different soils. 

Cole, D.N., 1990, Trampling disturbance and recovery of cryptogamic soil crusts in Grand 

Canyon National Park: Great Basin Naturalist, v. 50, no. 4, p. 321–325. 

8 
Under controlled conditions, cryptogamic soil crusts in Grand Canyon National Park 

were trampled by hikers to determine how rapidly they were pulverized and how rapidly they 

recovered. Only 15 passes were required to destroy the structure of the crusts; visual evidence of 

bacteria and cryptogam cover was reduced to near zero after 50 passes. It took soil crusts one to 

three years to redevelop, and after 5 years the extensive bacteria and cryptogam cover left little 

visual evidence of disturbance. Surface irregularity remained low after 5 years, however, 

suggesting that recovery was incomplete. 

Eckert, R.E.J., Wood, M.K., Blackburn, W.H., and Peterson, F.F., 1979, Impacts of off-road 

vehicles on infiltration and sediment production of two desert soils: Journal of Range 

Management, v. 32, no. 5, p. 394–397. 

This project staged a series of controlled motorcycle and 4-wheel drive vehicle passes, 

followed by simulated rainfall. Two sites were chosen to represent two different soil types. 

Infiltration rates were lower and sediment yield was higher after soil was disturbed by vehicular 

traffic. High sediment yield was attributed to reduced infiltration after 10 minutes; the remaining 

20 minutes of the test period were characterized by particles being carried away in runoff water. 

Folz, R.B., 2006, Erosion from all terrain vehicle (ATV) trails on National Forest lands (abs.): 

Proceedings of the 2006 American Society of Agricultural and Biological Engineers, Portland, 

Oregon, July 9–12, 2006: St. Joseph, Michigan, 2006 American Society of Agricultural and 

Biological Engineers, http://asae.frymulti.com/abstract.asp?aid=21056&t=2. 

Concern about unmanaged use of all terrain vehicles (ATV) on U.S. Forest Service lands 

prompted an experimental study to test the relative effects of low-, medium-, and highdisturbance trails (based on traffic levels), as measured by reduced litter/vegetation and the width 

and wheel-rut depth of trails. Trail condition was assessed and then subjected to simulated 

rainfall. A negative relationship between levels of ATV traffic and rainfall infiltration was not 

statistically significant among disturbance levels; however, there were significant differences in 

infiltration and measures of erosion between undisturbed and disturbed conditions. Data from 

this study will be used to estimate ATV traffic-induced erosion and make decisions regarding 

management of ATV use. 

Iverson, R.M., Hinckley, B.S., and Webb, R.M., 1981, Physical effects of vehicular disturbances 

on arid landscapes: Science, v. 212, no. 4497, p. 915–917. 

In 50 rainfall simulation tests, vehicle-use plots had about five times more runoff and 10-

20 times greater sediment yield than adjacent unused plots. In a desert environment, such effects 

may occur even when use of off-road vehicles is light. Recovery times from vehicular traffic 

were estimated to be nearly 100 years. Erosion rates were calculated from multivariate statistical 

analyses using 22 experimental factors. The character of the rainfall was identified as the most 

important variable in predicting increases in erosion. 

Sparrow, S.D., Wooding, F.J., and Whiting, E.H., 1978, Effects of off-road vehicle traffic on 

soils and vegetation in the Denali Highway region of Alaska: Journal of Soil and Water 

Conservation, v. 33, no. 1, p. 20–27. 

This study examined the effects of vehicles on trails. The surface layer of living material 

was killed on all main trails, although soil morphology was not generally altered except in the 

surface horizon. Varying amounts of organic matter were lost from the heavily used trails, 

9 
depending on slope and vehicle type. Soil depth and drainage were the most important factors 

influencing the condition of the trail. The greatest effects on soils occurred in poorly drained 

areas or on loose, gravel-free soils that were highly susceptible to erosion. 

Tuttle, M., and Griggs, G., 1985, Accelerated soil erosion at three State Vehicular Recreation 

Areas: central and southern California, in Erosion control: A challenge in our time, proceedings 

of the 16th annual International Erosion Control Association, February 21–22, 1985, San 

Francisco, California: San Francisco, California, International Erosion Control Association, p. 

105-115. 

Soil erosion rates were evaluated at three State Vehicular Recreation Areas, with a 

particular focus on hillclimbs. The key factors contributing to erosion rates were slope, length of 

climb, soil type, and weather. Based on monitoring and catchment basin yield, erosion in open 

areas dedicated to OHV use was 10 to 25 times greater than in undisturbed areas. 

Webb, R.H., 1982, Off-road motorcycle effects on a desert soil: Environmental Conservation, v. 

9, no. 3, p. 197–208. 

The effects of controlled motorcycle traffic on a Mojave Desert soil in California were 

studied in order to quantify soil compaction. Four experimental trails treated with 1, 10, 100, and 

200 passes with an off-road motorcycle were established in loamy sand at 6.2 percent (by 

weight) moisture content. Soil penetration resistance, bulk density, infiltration rate, and response 

to rainfall were measured for undisturbed soil and the experimental trails immediately after the 

impact, and soil cores were measured in the laboratory to determine pore-size distributions. Soil 

bulk density was remeasured one year after the impact to ascertain the amount of recovery. The 

1-pass trail had a slight surface indentation with knob imprints from the tires. Along the 100- and 

200-pass trails, there were berms and lateral edges, and their centers were 10–30 mm below the 

level of undisturbed soil adjacent to the trail.

Wilshire, H.G., and Nakata, J.K., 1976, Off-road vehicle effects on California's Mojave Desert: 

California Geology, June 1976, p. 123–132. 

This study was designed to evaluate long-term effects of an off-road vehicle race on the 

desert landscape, in particular the landscape condition after vehicular use (specifically 

motorcycles), whether or not effects were confined to the areas of direct impact, and how long 

the physical effects of such activities remained. Visual observations and penetrometer 

measurements were recorded in five ground types. Soil compaction was the dominant 

consequence of motorcycle use: penetrometer data revealed decreases in mean penetration 

depths. Combined with a notable reduction in plant cover, soil compaction significantly 

increased the potential for erosion. Initial vehicle impact resulted in substantial, immediate 

mechanical erosion, followed by wind erosion, culminating in the increased potential for water 

erosion over longer periods of time. 

Wilshire, H.G., Nakata, J.K., Shipley, Susan, and Prestegaard, Karen, 1978, Impacts of 

vehicles on natural terrain at seven sites in the San Francisco Bay area: Environmental Geology, 

v. 2, no. 5, p. 295–319. 

Vegetation and soil properties were measured at seven sites exposed to off-road vehicle 

activities. Impacts on loamy soils included greater soil surface strength and bulk density, lower 

infiltration rates and soil moisture, extended diurnal temperature ranges, and reduced organic 

10 
carbon. These effects, combined with the associated loss in vegetative cover, promoted erosion, 

the rates of which significantly exceeded Federal and local standards, and the increased sediment 

yield and runoff caused adverse effects on neighboring properties. 

2.3 OHV Effects on Vegetation 

2.3.1 Section Summary 

Relative to plant communities in OHV-impacted areas, those in undisturbed sites are 

dominated by native plants, invasive species are not increasing, plant growth and reproduction 

are vigorous, age-classy structures are appropriate to the species, and canopy cover and vertical 

structure are adequate for dispersing the energy of precipitation runoff and promoting water 

infiltration. Direct impacts of OHV activities on vegetation include reduced vegetation cover and 

growth rates, and increased potential for non-native grasses and pioneering species to become 

established, thus altering vegetation communities. In certain instances, however, the impervious 

nature of compacted route and paved road surfaces could result in significant runoff that 

generates greater moisture availability immediately along OHV routes. In turn, this would 

promote increased vegetation cover and plant abundance than one might find in surrounding 

areas farther away from OHV routes. 

Some important indirect effects of OHV activities on vegetation are tied to soil properties 

altered by OHV traffic, as soil properties typically influence vegetation growth. OHV roads and 

trails also create edge habitats, which can generate conditions that promote the encroachment of 

non-native and invasive plant species. Other indirect effects include increased amounts of 

airborne pollutants and dust raised by OHV traffic. A blanket of fugitive dust on plant foliage 

can inhibit plant growth rate, size, and survivorship. 

2.3.2 Overall Effects on Vegetation Cover and Community Composition 

When soils are severely disturbed, vegetation cover can be reduced significantly (Adams 

and others, 1982; Prose and others, 1987; Bolling and Walker, 2000) and growth can be impaired 

(Spencer and Port, 1988; Angold, 1997). As stated in the previous section, even a few passes by 

vehicles can cause significant changes in soil properties. Adams and others (1982) found reduced 

cover of desert annuals in tracks created by as few as 1 (on wet loamy sand) to 20 (on dry loamy 

sand) vehicle passes; the reduction in cover, however, was not due to fewer plants, but to smaller 

plant sizes. Similarly, Bolling and Walker (2000) found that in OHV routes there were many 

small individuals of creosote bush (Larrea tridentata), but larger plants were few or absent; in 

control plots, however, there were more large plants and fewer small ones. 

Reduced plant sizes are typical where the extent of soil compaction inhibits their roots 

from penetrating to deeper soil levels. In fact, Adams and others (1982) determined that root 

growth is precluded at soil strengths of about 20 kg/cm2

 (284.4 lb/in2). Within tracks made by 1, 

3, 10, and 20 vehicle passes, Adams and others (1982) found that annuals with large taproots (for 

example, pincushion flower [Chaenactis fremontii]) decreased, whereas there was significantly 

greater cover of common Mediterranean grass (Schismus barbatus), a non-native grass with a 

fibrous root system. The fibrous root system of plants that characterized by single cotyledons, 

such as common Mediterranean grass, allows for easier germination and root growth than is 

possible for taprooted dicotyledons. 

Soil compaction also increases the potential for invasive, non-native annuals and other 

early successional plants to establish rapidly in OHV routes, whereas native perennials may 

require at least 5 years to become established (Adams and others, 1982; Prose and others, 1987; 

11 
Lovich and Bainbridge, 1999). This is due, in part, to the increased surface moisture availability 

within the tracks of OHV routes after compaction has reduced the rate of water infiltration, 

which may favor the rapid germination and growth of non-native and invasive annuals (Adams 

and others, 1982). In disturbed areas, pioneering species, such as burrobush (Ambrosia dumosa

and Hymenoclea salsola—now Ambrosia salsola; see http://ucjeps.berkeley.edu/cgibin/get_cpn.pl?3578), often dominate the plant community and typically their percent cover is 

similar to, or greater than, that of undisturbed areas (Prose and others, 1987). Davidson and Fox 

(1974) also found that non-native, early-successional species, such as redstem stork’s bill 

(Erodium cicutarium) and common Mediterranean grass were common at sites disturbed by 

OHVs. When comparing vegetation in disturbed versus protected plots, Brooks (1995) found that 

common Mediterranean grass was the only species with greater biomass in the disturbed plots. 

OHV traffic also causes direct impacts to vegetation structures (breakage, smashing), 

although population-level effects may be difficult to discern in the short term. Overall, the extent 

of immediate effects increases with the frequency of OHV passes. For example, Webb (1983) 

found that after a single pass, annual plants on an OHV route remained intact, but most were 

destroyed after 10 passes. Likewise, a series of studies to evaluate the impacts of OHV traffic on 

the Federally listed Peirson’s milkvetch (Astragalus magdalenae peirsonii) indicated that this 

plant was more likely to occur at sites closed to OHV activity than at OHV sites that have been 

rested from OHV activity (Groom and others, 2005); however, additional study indicated that the 

number of reproducing plants (and the seedbank) was adequate to maintain the milkvetch 

population (Phillips and Kennedy, 2006; for more reports, go to 

http://www.fws.gov/carlsbad/PMV_Docs.htm). It remains unclear, however, whether research 

conducted over longer time scales would yield different results. 

2.3.3 Edge Effects Along OHV Routes 

Roads and trails also create edge habitats (Johnson and others, 1975; Vasek and others, 

1975; Adams and Geis, 1983; Andrews, 1990; Holzapfel and Schmidt, 1990; Lightfoot and 

Whitford, 1991; Reed and others, 1996), resulting in a variety of effects, including changes in 

vegetation and encroachment of non-native and invasive species (Huey, 1941; Lovich and 

Bainbridge, 1999). As mentioned in section 2.3.2, the impermeable surfaces of roads and OHV 

routes shed precipitation, thereby increasing overall moisture availability in the immediate 

vicinity of the road or route. Additionally, the coarse-textured soils typically found in association 

with paved roads (roadbed materials laid down prior to paving) permit good water infiltration 

along road edges (Hillel and Tadmor, 1962); similar conditions may occur along improved 

gravel routes. The increased moisture availability may promote greater plant vigor along 

roadsides than in surrounding areas (Johnson and others, 1975), and Angold (1997) indicated 

that such effects may extend as far as 200 m from road edges. Indeed, several studies have 

shown that there can be more vegetation cover along roadsides and right-of-ways than in 

adjacent areas (Johnson and others, 1975; Vasek and others, 1975; Holzapfel and Schmidt, 1990; 

Lightfoot and Whitford, 1991). Perennial shrubs, in particular, may grow larger and attain 

greater vigor and density along road edges (Johnson and others, 1975; Lightfoot and Whitford, 

1991). Likewise, Johnson and others (1975) found that the standing crop (a measure of primary 

productivity) was 6 times greater along unpaved roads (17 times greater along paved roads) than 

it was in nearby undisturbed areas. 

The greater vegetation cover typically observed along roadsides also is often due, in part, 

to greater species richness in those areas (Holzapfel and Schmidt, 1990); however, much of this 

diversity may be represented by non-native species easily dispersed along roads and trails 

12 
(Wilcox, 1989; Tyser and Worley, 1992; Parendes and Jones, 2000). Furthermore, local-scale 

increases in species richness can be associated with decreases in species richness at the landscape 

scale, thus creating a relatively impoverished and anthropogenic vegetation community 

(Holzapfel and Schmidt, 1990). Interestingly, increased vegetation cover along roadsides may 

attract more invertebrates and other organisms. For example, Lightfoot and Whitford (1991) 

found that shrubs along a road supported greater numbers of foliage arthropods. What is not 

clear, however, is whether high densities of animals in roadside habitats represent improved 

conditions for native fauna or dominance by invasive and/or non-native organisms. Furthermore, 

high densities do not necessarily represent population sources (that is, where survivorship and 

productivity are high enough to contribute to the species’ overall population); instead, high 

densities can indicate poor-quality habitat into which subordinate animals may crowd and 

experience poor survivorship if they cannot find or defend better habitat (population sinks). In 

other words, density can be a misleading indicator of habitat quality (Van Horne, 1983). It is 

important to note, however, that the greater vegetation cover along roadsides compared to plots 

away from roads may be a phenomenon found only in arid environments (Hillel and Tadmor, 

1962; Holzapfel and Schmidt, 1990). 

Fugitive dust raised by OHV traffic also affects vegetation in the vicinity of roads. Along 

Alaskan roads heavily traveled by various types of vehicles, Walker and Everett (1987) found 

significant dust impacts up to 10 m (10.9 yd) from the roadside and dust blankets up to 10 cm 

(3.9 in) thick on mosses and other vegetation of low stature. Several morphological factors 

contribute to plant susceptibility to heavy dust loads, including mat or prostrate growth form, 

lack of a protective stem cortex or leaf cuticle, and intricate branching or closely spaced leaves 

that tend to trap dust (Walker and Everett, 1987; Spellerberg and Morrison, 1998). Processes that 

may be affected by dust include photosynthesis, respiration, and transpiration due to blocked 

stomata and cell destruction (Spellerberg and Morrison, 1998), all of which could result in 

reduced plant growth, size, productivity, and/or survivorship.

2.3.4 Annotated Bibliography for OHV Effects on Vegetation 

Adams, J.A., Stolzy, L.H., Endo, A.S., Rowlands, P.G., and Johnson, H.B., 1982, Desert soil 

compaction reduces annual plant cover: California Agriculture, v. 36, no. 9–10, p. 6–7. 

Soil crust properties and associated changes in vegetation composition were measured 

under controlled conditions over two 6-month wet seasons to determine how rapidly they were 

altered by vehicle passes. Reductions in annual plant cover occurred in tracks created by as few 

as 1 (on wet loamy sand) to 20 vehicle passes (on dry loamy sand). This cover reduction, 

however, was not due to fewer plants; rather, the plants were smaller, and their size depended on 

the duration of drying periods, during which the soil strength intensified in impact/track areas. 

Cover of annuals with large taproots (for example, Chaenactis fremontii) decreased in vehicle 

tracks, whereas the cover of Schismus barbatus, a grass with a fibrous root system, was 

significantly greater in tracks generated by 1, 3, 10, and 20 vehicle passes. It was determined that 

root growth for plants stops at soil strengths of about 20 kg/cm2 (284.4 lb/in2 [or PSI]). Soil 

disturbance also increased the potential for grasses and pioneering annual species to become 

established, whereas perennial species would take at least 5 years to return. A possible reason for 

this may be greater water availability in the track. 

Angold, P.G., 1997, The impact of a road upon adjacent heathland vegetation—Effects on plant 

species composition: Journal of Applied Ecology, v. 34, no. 2, p. 409–417. 

13 
The effect of a road on heathland vegetation was investigated at five sites adjacent to the 

main trunk road through the New Forest, Hampshire, United Kingdom, and nine supplementary 

sites adjacent to five minor roads. There was enhanced growth of vascular plants near the road, 

notably heather and grasses, which was probably due to nitrogen oxides from vehicle emissions. 

There was a decrease in the abundance and health of lichens near the road. There was an increase 

in the abundance of grasses in the heathland near roads, which may be due to the changes in 

relative competitive ability of plant species under conditions of eutrophication. The extent of the 

edge effect in the heath was closely correlated with traffic intensity, with a maximum edge effect 

of 200 m adjacent to a dual carriageway. 

 

Benninger-Traux, M., Vankat, J.L., and Schaefer, R.L., 1992, Trail corridors as habitat and 

conduits for movement of plant species in Rocky Mountain National Park, Colorado, USA: 

Landscape Ecology, v. 6, no. 4, p. 269–278. 

Ground-layer vegetation was sampled along selected trail corridors to determine whether 

corridors provide habitat for certain species and serve as conduits for species dispersal. Patterns 

of plant species composition were analyzed in relation to distance from trail edge, level of trail 

use, and distance from trailheads, junctions, and campgrounds. Species composition was 

significantly affected by distance from trail edge and level of trail use, as species were favored or 

inhibited by the corridor, depending upon their growth habits. Species composition also was 

affected by distance from trailheads. These findings, along with the presence of exotic species, 

indicate that trail corridors in Rocky Mountain National Park function as habitat and conduits for 

dispersal of plant species. 

 

Bolling, J.D., and Walker, L.R., 2000, Plant and soil recovery along a series of abandoned 

desert roads: Journal of Arid Environments, v. 46, no. 11, p. 1–24. 

To elucidate factors controlling desert succession, soil and vegetation dynamics were 

examined along roads abandoned for 5, 10, 21, 31, 55 and 88 years in southern Nevada. None of 

the measured soil or vegetation parameters varied significantly with road age. Differences were 

found, however, between soils and vegetation on roads compared to those on nearby control 

sites, and soils differed between roads created by surface vehicular traffic and those made by 

bulldozing. Studies of recovery following disturbance in deserts must take into account natural 

patterns of plant and soil heterogeneity and initial disturbance type. 

Brooks, M.L., 1995, Benefits of protective fencing to plant and rodent communities of the 

western Mojave Desert, California: Environmental Management, v. 19, no. 1, p. 65–74. 

This paper documents the response of plant and small mammal populations to fencing 

constructed to preclude OHV activities between 1978 and 1979 at the Desert Tortoise Research 

Natural Area, Kern County, California. Aboveground live annual plant biomass was generally 

greater inside than outside the fenced plots during April 1990, 1991, and 1992. The non-native 

grass, Schismus barbatus, was a notable exception, producing more biomass in the unprotected 

area. Forb biomass was greater than that of non-native annual grasses inside the fence during all 

3 years of the study. Outside the fence, forb biomass was significantly greater than that of nonnative grasses only during spring 1992. Percent cover of perennial shrubs was greater inside the 

fence than outside, while no significant trend in density was detected. There was also more seed 

biomass inside the fence, which may have contributed to the greater species diversity and density 

of Merriam's kangaroo rats (Dipodomys merriami), long-tailed pocket mice (Chaetodipus 

14 
formosus), and southern grasshopper mice (Onychomys torridus) in the protected area. These 

results show that protection from OHV disturbance has many benefits, including greater overall 

community biomass and diversity. 

Holzapfel, C., and Schmidt, W., 1990, Roadside vegetation along transects in the Judean Desert: 

Israel Journal of Botany, v. 39, p. 263–270. 

Vegetation was studied on comparable plots along roadsides and in the surrounding area. 

The uniqueness of roadside vegetation was shown using indices and measurements that allowed 

comparison along a climatic gradient. Near roads, biomass and species diversity were notably 

greater than in surrounding areas, and the chorological composition was different, at least under 

arid conditions. The reasons for these differences are discussed based on investigations of site 

conditions. Increased water runoff and more favorable soil conditions seem to have had 

important influences on the vegetation community. 

Kutiel, P., Eden, E., and Zhevelev, Y., 2000, Effect of experimental trampling and off-road 

motorcycle traffic on soil and vegetation of stabilized coastal dunes, Israel: Environmental 

Conservation, v. 27, no. 1, p. 14–23. 

The aim of this study was to assess the response of soil and annual plants of stabilized 

Mediterranean coastal dunes in Israel to various intensities of short-duration pedestrian and 

motorcycle traffic. Experimental procedures entailed 0, 20, 50, 100, and 200 straight and 150 

turn motorcycle passes. The response of annual plants was assessed by measuring ground cover, 

height, and species richness and diversity, and soil response was assessed by measuring 

penetrable depth, organic matter, and moisture content. Motorcycle passage had an immediate 

significant impact on annual plants at all traffic intensities. The maximum effect on plants was 

observed in the wheel tracks and in the turn lanes. Mean annual ground cover and height were 

less sensitive measures than species richness and diversity for determining the overall impact of 

motorcycles on the area. 

Prose, D.V., Metzger, S.K., and Wilshire, H.G., 1987, Effects of substrate disturbance on 

secondary plant succession—Mojave Desert, California: Journal of Applied Ecology, v. 24, no. 

1, p. 305–313. 

The effects of substrate disturbance on perennial plant succession in the Mojave Desert 

were assessed at three military camps abandoned for 40 years. Soil compaction, removal of the 

top layer of soil, and altered drainage channel density caused significant changes in perennial 

plant cover, density, and relative species composition. Long-lived species, predominantly Larrea 

tridentata, were dominant in all control areas, but percent cover and density were greatly reduced 

in areas where substrate alterations were significant. At one camp where substrate alterations 

were insignificant in disturbed areas, Larrea was the dominant species (as it was in the control 

areas). 

Schultink, G., 1977, Impact analysis of off-road-vehicle use on vegetation in the Grand Mere 

Dune environment: East Lansing, Michigan, Michigan State University, Report no. 

NASACR155764, 10 p. 

A linear regression of percent unvegetated land in OHV-impacted areas versus time for 

two sample areas indicated that the areas underwent average declines of 1.9 and 5.9 percent per 

year in vegetation cover. Two factors were assumed to play roles in the difference: the difference 

15 
in accessibility and the extent of vegetation fragmented during the first year of the study (one 

sample area was located closer to potential access points and was more fragmented initially). 

Wilshire, H.G., Shipley, Susan, and Nakata, J.K., 1978, Impacts of off-road vehicles on 

vegetation: Transactions of the North American Wildlife and Natural Resources Conference, v. 

43, p. 131–139. 

Observations of the impacts of off-road vehicles on soils and vegetation were made at 

more than 400 sites in seven western states during 3 years. This type of land use had both direct 

and indirect effects on vegetation. Direct effects included crushing and uprooting plants. Indirect 

effects included modification of the soil, which affected plants beyond the areas directly 

impacted by vehicles, and restoration of the plant cover was inhibited. This paper covers the 

erosional effects on vegetation, depositional effects on vegetation, and the effects of physical and 

chemical modification of remnant soils on revegetation. 

2.4 OHV Effects on Wildlife and Habitats: Native, Threatened, and Endangered 

Species 

2.4.1 Section Summary 

The impacts of OHV activities on wildlife and their habitats are numerous and well 

documented. Networks of roads and trails fragment habitat, reduce patch size, and increase the 

ratio of edge to interior. This may have serious consequences for area-sensitive species (those 

that cannot carry out certain aspects of their life cycles without large blocks of habitat or 

corridors linking habitat patches), predator-prey relationships, and overall population dynamics. 

In particular, fragmentation and edges created by OHV routes may have strong effects on animal 

movement patterns. Precluding or inhibiting animal movements effectively diminishes dispersal 

to and recolonization in other areas, thus increasing the likelihood of local extirpations. Overall, 

studies demonstrate that even narrow roads (paved and unpaved) and trails can represent 

significant barriers to the movements of animals. Reluctance to cross even narrow trails similar 

in width to routes created by OHV travel may alter or preclude the movements of various 

species. The cumulative effects of OHV-route networks proliferating across the landscape may 

have serious ecological consequences for species reluctant to cross OHV routes. Where 

threatened and endangered species are at risk, understanding their particular responses to roads 

of varying types, widths, use intensities, and habitat contexts is crucial. 

OHV routes also generate conditions unlikely to occur in environments unaffected by 

OHV activity; in turn, these conditions can facilitate range extensions and invasions of nonnative and/or opportunistic species. In addition, OHVs can contribute directly to mortality (and 

possible population declines) of wildlife species through collisions with vehicles, nest 

destruction, and collapsing burrows. Noise generated by OHVs also has been found to cause 

inner ear bleeding. In particular, noise may alter animal behaviors, breeding populations, the 

abilities of some species to detect predators (through auditory cues), and it can stimulate 

estivating animals to emerge from their underground burrows at inappropriate times. These 

factors may result in diminished body mass, reduced productivity, and/or poor survivorship. 

2.4.2 Loss of Habitat Connectivity: Fragmentation and Barrier Effects 

Creating roads and trails (of any kind) diminishes habitat connectivity, increases the 

proportion of edge to interior habitat, and decreases patch size of habitats (Reed and others, 

1996; Forman and others, 2003). In fact, roads, including OHV routes, represent a principal 

16 
factor contributing to habitat fragmentation at various scales (Meffe and Carroll, 1997). 

Furthermore, both paved roads and OHV routes—ranging from 4-lane paved highways to twotrack routes less than 3 m (3.3 yards) wide—that separate once-continuous habitat can disrupt the 

movement and dispersal of many wildlife species between and within habitats (Swihart and 

Slade, 1984; Brody and Pelton, 1989; Yanes and others, 1995; Lovallo and Anderson, 1996; 

Clevenger, 1998; Forman and Alexander, 1998; Jackson and Griffen, 1998). In turn, these effects 

can have consequences for area-sensitive species and may encourage non-native and/or invasive 

species. Special-status wildlife species known to occur on BLM lands and whose long-term 

persistence is threatened by habitat fragmentation and diminished habitat connectivity include 

grizzly bear (Ursus arctos horribilis; Gibeau and Herrero, 1998; Servheen and others, 1998), 

black bear (Ursus americanus; Brody and Pelton, 1989), gray wolf (Canis lupus; Paquet and 

Callahan, 1996), mountain lion (Felis concolor; Beier, 1993), lynx (Felis lynx; Ruediger, 1998), 

ocelot (Leopardus pardalis; Tewes and Blanton, 1998), and desert tortoise (Gopherus agassizii; 

Boarman and Sazaki, 1996). The resulting isolation of subpopulations (Dobson and others, 1999) 

can promote increased inbreeding and a lack of genetic exchange with other subpopulations, 

ultimately leading to declines in the genetic diversity required for adaptation to variable 

conditions and possible founder effects (Hanski and Simberloff, 1997; Hanski, 1999). Another 

consequence of subpopulation isolation is the reduced potential for recolonization when 

extirpations occur as a result of localized population fluctuations and catastrophic events (Yanes 

and others, 1995). 

Until recently, only wide, multi-lane, paved roads have been considered significant 

barriers to animal movements. More recent lines of evidence from fragmentation studies, 

however, indicate that the ability or willingness of an animal to cross a given road type varies 

widely by species (Brody and Pelton, 1989; Lovallo and Anderson, 1996). For example, rodents 

in a desert habitat were found to avoid crossing a 4-lane highway, although they lived alongside 

the road in the right-of-way vegetation (Garland and Bradley, 1984). Likewise, in forested 

habitats divided highways wider than 90 m (98.4 yd) served as total barriers to dispersal by small 

forest mammals (Oxley and others, 1974). However, improved gravel roads have been found to 

inhibit crossings by mountain lions (Puma concolor; van Dyke and others, 1986), and even 

infrequently traveled, single-lane dirt roads have been found to alter movements by some species 

(Andrews, 1990). For example, Swihart and Slade (1984) report that prairie voles (Microtus 

ochrogaster) and cotton rats (Sigmodon hispidus) were strongly inhibited from crossing a route 

less than 3 m (3.3 yd)wide and composed of two dirt tracks created by the passing of 10 to 20 

vehicles per day. Oxley and others (1974) evaluated small mammal responses to roads and routes 

ranging from 4-lane paved highways to country gravel roads in forested systems of southeastern 

Canada and found that they were not willing to cross roads or other routes with a total clearance 

(the distance between forest margins, including road surfaces and immediately adjacent strips of 

vegetation kept very short via spraying and/or mowing) of 30 m (32.8 yd) or greater; road 

surface apparently was unimportant. Likewise in Germany, forest mice (Apodemus flavicollis) 

did not cross roads 6 m (6.6 yd) wide, and very few mice returned to the side of the road from 

which they were captured after being translocated to the opposite side within the same habitat 

type (Mader, 1984). Areas characterized by high densities of roads also are characterized by low 

probabilities that amphibian species will occupy breeding pools (Vos and Chardon, 1998), most 

likely because the edges were relatively impermeable (whether due to behavioral avoidance or 

direct mortality) to critical amphibian movements (dispersal, seasonal movements; Gibbs, 1998). 

On the other hand, some small mammals are known to cross paved and gravel roads (Bakowski 

17 
and Kozakiewicz, 1988), particularly where vegetated highway right-of-ways resemble those of 

adjacent habitats (Wilkins, 1982). These studies indicate that road surface type is not always the 

critical inhibiting factor; however, it does influence traffic speed, which can directly affect 

mortality rates (Oxley and others, 1974; Bakowski and Kozakiewicz, 1988). 

Invertebrates also may be precluded from crossing various road types, including those 

considered relatively narrow; again, however, there are species differences that may be 

influenced by their ecologies and physical capabilities. For example, Samways (1989) found that 

both “tarred” (paved) and “untarred” roads were almost complete or partial barriers to three 

species of bush crickets (Decticus varrucivorus monspeliensis and Platycleis fedtschenkoi azami, 

both wingless, and P. tessellate, the flight range of which is less than [<] 5m [5.5 yd]), but roads 

were only minor, very minor, or did not serve as barriers to the movements of six other bush 

cricket species, five of which can readily fly across roads (flight ranges from <30 to 150 m 

[32.8–164.0 yd]. On the other hand, Munguira and Thomas (1992) found that wide highways did 

not affect the movements of butterflies in open populations; movements of butterflies in closed 

populations, however, were slightly impeded by roads. Other butterfly species may not even 

attempt to fly across roads (described by authors as two-lane highways and secondary roads), 

possibly due to the extreme changes in microclimate over roads (including columns of warm air 

rising above roads; Boer Leffef, 1958, as interpreted and translated by van der Zande, 1980). 

Mader (1984) reported that in a five-year mark-recapture-release study involving 10,186 carabid 

beetles representing nine species, three species were never recaptured on the opposite side of 

study area roads (one- or two-lane paved roads) or parking loops, and the remainder were 

recaptured across the road only rarely. However, some individuals of a Swedish snail species 

(Arianta arbustorum) that were captured and translocated to the opposite sides of narrow paths 

or relatively wider roads did return to the capture sides of paths (Baur and Baur, 1990). 

2.4.3 Edge Effects 

Aside from fragmenting habitat, roads and trails of any kind also create habitat edges 

(Reed and others, 1996). In many instances, these edge effects extend well beyond the road’s 

actual footprint and for some species the effects may extend well into the desert interior. 

Therefore, assessing edge effects of roads and trails on wildlife may entail determining 

distributions of wildlife in reference to the extent of any one edge effect (Yahner, 1988). Even 

then there may be an array of factors that vary the distances from roads/trails at which edge 

effects may be apparent. For example, Nicholson (1978) indicates that metapopulations of desert 

tortoises may be depleted within 0.8 km (0.5 mi) of highway edges, and von Seckendorff Hoff 

and Marlow (1997) indicate that this effect may extend as far as 3.5 km (2.2 mi) from the 

highway edge. 

Given the frequent incidence of significant vegetation cover along road edges, many 

organisms may be attracted to right-of-way habitats. For example, Adams and Geis (1983) found 

greater small mammal density within interstate right-of-way habitats than in adjacent habitats. 

Density, however, can indicate habitats sinks to which animals retreat when more desirable 

habitats are occupied (Van Horne 1983). Alternatively, road edges may serve as ecological traps 

(Andrews, 1990) that are attractive and replete with necessary resources on the one hand, but 

impose unusually high mortality rates on the other hand. For example, birds may be attracted to 

lush roadside vegetation for breeding, nesting, or foraging (Clark and Karr, 1979), but they may 

be at great risk of mortality due to being hit by vehicles (Mumme and others, 2000). Similarly, 

avian eggs and nestlings can experience increased mortality due to high rates of predation 

(Yahner and others, 1989) in edge habitats. As mentioned in the section above, edge effects 

18 
along roads can alter or preclude the seasonal movements of amphibians to their breeding pools 

(Gibbs, 1998; Vos and Chardon, 1998). 

In the same ways that travel routes promote increased dispersal of non-native and 

invasive plant species, they also promote increased distributions of wildlife species otherwise 

unlikely to be common in a given area; in turn, this exerts additional competitive pressures on 

native species. Huey (1941) documented pocket gophers (Thomomys umbrinus) extending their 

ranges across the Mojave Desert via roads and canal systems. Although much of the surrounding 

desert landscape contained soils unsuitable for gophers, the attractive habitat (greater cover of 

vegetation resulting from increased moisture availability) along roadsides and canals facilitated 

the spread of these animals (Huey, 1941). An additional important edge effect associated with 

roads of many types is the presence of utility infrastructures, which can contribute to 

significantly altered predator-prey relationships along roads. For example, raven species (Corvus

spp.) have increased their distribution throughout the Mojave Desert, primarily due to the fact 

that they can perch along utility structures to scan for carcasses on adjacent roads (paved and 

unpaved) (Knight and Kawashima, 1993), a significant concern in light of the fact that Berry and 

others (1986) reported ravens as being responsible for 68 and 75 percent of mortality among 

juvenile desert tortoises on two study plots. 

2.4.4 OHV Disturbance and Noise 

Vehicular traffic is also a source of noise and other stimuli that have the potential for 

disturbing wildlife along any type of road or trail (Singer, 1978; van der Zande, 1980; Brattstrom 

and Bondello, 1983; Bowles, 1995; Reijnen and others, 1995, 1996; Bowles, 1995; Kaseloo and 

Tyson, 2004). Veen (1973; as interpreted and translated by van der Zande, 1980) found that four 

shorebird species inhabiting open grassland areas were disturbed within 500–600 m of a “quiet 

rural road” and within 1600–1800 m of a “busy highway;” van der Zande (1980) reanalyzed 

Veen’s data and yielded similar results for three of the four species, and went on to conclude that 

populations of these birds were diminished by as much as 60 percent over those distances. 

Forman and Alexander (1998) found that noise levels generally increase with traffic intensity, 

and Reijnen and others (1995, 1997) concluded that traffic noise can lead to significant 

reductions in breeding bird densities. Larger animals also exhibit responses to the intensity of 

traffic and traffic noise. Lyren (2001) found that coyotes changed their road-crossing periods in 

response to changes in traffic intensity throughout the day, and Singer (1978) reported that, in 

response to the shifting of truck gears, mountain goats ran away from a road edge when the truck 

was 1 km (0.6 mi) away from them, and they ran away from a lick that was 400 m (437.4 yd) 

from the road. 

Noise emitted from certain types of OHVs can be as high as 110 decibels, which is near 

the threshold of human pain (Lovich and Bainbridge, 1999). Although sounds from OHV motors 

are not the loudest anthropogenic sounds, in wildlife habitats they are emitted more frequently 

than other high-intensity sounds (Brattstrom and Bondello, 1983), and the effect on animals can 

be significant. For example, sand lizards (Uma scoparia) and kangaroo rats (Dipodomys deserti) 

experienced hearing loss that lasted for weeks after being exposed to less than 10 minutes of 

dune buggy playback recordings played intermittently at lower decibel levels than the animals 

would have been exposed to in the actual presence of a dune buggy (Brattstrom and Bondello, 

1983); subsequently, both species were unresponsive to recordings of predator sounds. In two 

other studies, kangaroo rats (Dipodomys spectabilis) experienced inner ear bleeding when 

subjected to OHV noise (Berry, 1980b; Bury, 1980). Another issue is the way in which OHV 

noise (sound pressure) may simulate that of natural sounds (thunder, for example) to which many 

19 
animals may be adapted to respond. For example, in response to 30 minutes of taped motorcycle 

sounds, Brattstrom and Bondello (1983) documented a spadefoot toad (Scaphiopus couchii) 

emerging prematurely (wrong season, absence of rain) from its burrow, most likely because the 

sound mimicked that of thunder, to which the species would normally respond. 

Noise, lights, and other disturbances associated with OHV activities also have the 

potential for eliciting stress responses from a broad spectrum of wildlife taxa. Indeed, studies 

have shown that ungulates, birds, and reptiles all experience accelerated heart rates and 

metabolic function during disturbance events; in turn, animals may be displaced and experience 

reproductive failure and reduced survivorship (see review in Havlick, 2002). For example, radiocollared mule deer disturbed by ATVs altered their patterns of foraging and spatial use of 

habitat; deer in undisturbed areas, however, exhibited no such changes (Yarmoloy and others, 

1988). In addition, Yarmoloy and others (1988) found that harassment of deer resulted in 

diminished reproductive output in the following fawning season, whereas deer that were not 

harassed experienced no change in reproduction. 

2.4.5 Wildlife Mortality and Related Issues 

Direct wildlife mortality can result from vehicular impact (Harris and Gallagher, 1989; 

Beier, 1993; Bruinderink and Hazebrook, 1996; Moore and Mangel, 1996), thus removing 

individuals from populations (Harris and Gallagher, 1989; Forman and Alexander, 1998); thus, 

habitats containing roads may represent population sinks for any species that commonly attempts 

to move from one habitat fragment to another by crossing roads (Kline and Swann, 1998). If 

mortality rates exceed rates of reproduction and immigration, wildlife populations decline (Beier, 

1993; Bruinderink and Hazebrook, 1996; Moore and Mangel, 1996; Forman and Alexander, 

1998). Previous studies indicate that mortality rates vary widely according to habitat and road or 

route characteristics (for example, road width, traffic density and speed, adjacent habitat) (Ward, 

1982; Bashore and others, 1985; Foster and Humphrey, 1995; Evink and others, 1996, 1998), as 

well as taxa studied—invertebrates: Seibert and Conover (1991), Munguira and Thomas (1992); 

reptiles and amphibians: Rosen and Lowe (1994), Ashley and Robinson (1996), Boarman and 

others (1998), Rudolph and others (1998), Means (1999); birds: Dhindsa and others (1988), 

Moore and Mangel (1996), Mumme and others (2000); and mammals: Gilbert and Wooding 

(1996), Romin and Bissonette (1996), Lehnert and Bissonette (1997), Gunter and others (1998), 

Lyren (2001). Even where the frequency of wildlife mortality is relatively low most of the year, 

it may increase during certain seasons (Feldhammer and others, 1986; Bruinderink and 

Hazebrook, 1996) or when traffic frequency increases (McCaffery, 1973). Furthermore, 

population dynamics can be altered if low mortality rates nonetheless cause disproportionate 

mortality among specific sex and/or age classes (Beier, 1993; Moore and Mangel, 1996; Mumme 

and others, 2000). 

Several researchers have conducted extensive monitoring at desert OHV sites and 

undisturbed sites to compare direct effects of OHV activity on mortality and abundance of 

certain reptile species (Bury and others, 1977; Berry, 1980a; Bury, 1980; Luckenbach and Bury, 

1983; Brooks, 1999; Grant, 2005). Of important concern is the susceptibility of desert tortoises 

to mortality on all types of roads. Berry (1980a) found a link between OHV activity and 

population declines of the desert tortoise and Couch's spadefoot toad (Scaphiopus couchii); 

numbers of tortoises and active burrows in a 25-ha control plot were significantly greater than in 

a similar plot exposed to OHV activity, presumably the result of direct mortality from vehicles or 

the collapsing of burrows caused by OHV traffic (Lovich and Bainbridge, 1999). Additionally, 

the body masses of subadult and adult tortoises in the control plot were greater than those of 

20 
tortoises in the OHV area (Bury and Luckenbach, 1986, cited in Lovich and Bainbridge, 1999). 

When comparing lizards in OHV-impacted plots to control plots, controls supported 1.8 times 

more species, 3.5 times more individuals, and 5.9 times more biomass (Luckenbach and Bury, 

1983). Similarly, Bury and others (1977) found more reptile species (1.63 times more) and 

greater reptile abundance (182 percent more individuals) at control sites than at OHV sites. In 

another study, the remains of 39 tortoises were recorded during three surveys over a 2.5-year 

period along a 24-km (14.9-mi) section of paved highway in the western Mojave Desert 

(Boarman and others, 1993). Snakes also experience high rates of mortality in the Mojave Desert 

due to their strategy for thermoregulation (lying on warm surfaces, such as roads; Sullivan, 

1981). Rosen and Lowe (1994), who conducted nighttime snake surveys along a 2-lane paved 

road in the Sonoran Desert (primarily within Organ Pipe Cactus National Monument), 

documented a 72 percent rate of snake mortality (104 live, 264 dead); mortality peaked in 

spring—when snake activity was moderately high and automobile traffic had not yet reached its 

summer minimum—and during rain events in the monsoon season (July through early 

September). Overall snake mortality during the entire 4-year study was estimated at 2,383 snakes 

(13.5 snakes/km/year; 8.1 snakes/mi/year), although actual numbers were likely closer to 4,000. 

Densities and species diversity of desert birds and small mammals also have been 

reported to decrease in areas where OHV use was extensive (Busack and Bury, 1974; Bury and 

others, 1977; Luckenbach, 1978; Luckenbach and Bury, 1983; Brooks, 1999). Direct and indirect 

effects of OHVs on these species include breaking shrubs containing nests (nests, eggs, or 

nestlings destroyed) and diminished cover when shrubs are reduced or eliminated, mortality due 

to vehicle impact (especially ground-dwelling animals), and collapse of burrows due to OHV 

traffic (Bury and others, 1977). Bury and others (1977) found greater small mammal species 

richness (1.25 times greater) and abundance (500 percent more individuals) at control sites than 

OHV sites. Similarly, Luckenbach and Bury (1983) found 1.5 times more small mammal 

species, 5.1 times more individuals, and 2.2 times more biomass in control plots than in OHVimpacted plots; the number of desert kangaroo rats recorded in OHV plots was 53 percent lower 

than the number in control plots. Luckenbach and Bury (1983) found that overall animal 

activity—as measured by track frequencies—was greater in control areas than it was in OHV-use 

areas: arthropod tracks were 24 times more abundant, kangaroo rat tracks were 5 times more 

abundant, kit fox tracks were 2 times more abundant, and cottontail rabbit tracks were 10 times 

more abundant. Finally, Brooks (1999) found that protected areas in the Desert Tortoise 

Research Natural Area supported a greater abundance and species richness of birds and lizards 

than nearby portions of the desert subjected to intense OHV use and past sheep grazing. In one 

study, however, road mortality did not appear to have detrimental effects on densities of small 

mammals inhabiting highway right-of-ways, although the authors admit that they could not rule 

out confounding effects of immigration (Adams and Geis, 1983). In a study of 36 radio-marked 

flat-tailed horned lizards (Phrynosome mcallii) subjected to high (60 percent OHV track 

coverage in 60 minutes of riding time), low (30 percent in 20 minutes of riding time), and no (0 

percent) impact by OHV traffic in 100 × 100 m (109.4 × 109.4 yd) plots, all survived. At the 

time of OHV treatment, however, 32 of the lizards were in their hibernation burrows 2–17 cm 

(0.8–6.7 in) underground (Grant, 2005), and it remains unclear whether soil substrates and 

vegetation growing above the burrows helped protect the animals from being crushed (21 of the 

32 were under shrubs, and 8 burrows were known to have been run over directly by OHVs). 

A major indirect effect of OHV activity on vertebrate survivorship is loss of vegetation 

cover. For all terrestrial vertebrates sampled, including species of conservation concern (desert 

21 
kangaroo rat [Dipodomys deserti] and fringe-toed lizard [Uma notata]), Bury and others (1977) 

found a positive correlation between the percent canopy cover of creosote bush and species 

richness, abundance, and biomass. In a study of OHV effects on biota (including herbaceous and 

perennial plants, arthropods, lizards, and mammals) of the Algodones Dunes area in California, 

Luckenbach and Bury (1983) detected 9.4 times more cover, and 40 times more overall volume 

in control plots than in OHV-impacted plots, largely because shrubby perennial cover was 

greater in control plots. Another indirect effect of OHV activity on wildlife mortality is the 

proliferation of routes that provide greater access to remote places by hunters, poachers, and 

people seeking several forms of nonconsumptive recreation (Boyle and Samson, 1985; Andrews, 

1990). Boyle and Samson (1985) also report a variety of nonconsumptive recreation impacts on 

wildlife, including flushing animals off nests; unnecessary energy expenditures; and 

displacement of animals from food, shelter, and other vital resources. Of particular concern was 

the increasing access that roads provide for tortoise collectors, which may explain declining 

trends in tortoise numbers along highways (Boarman and others, 1997). 

2.4.6 Annotated Bibliography for OHV Effects on Wildlife and Habitats: Native, Threatened, 

and Endangered Species 

Berry, K.H., 1980, A review of the effects of off-road vehicles on birds and other vertebrates, in

DeGraaf, R.M., and Tilghman, N.G., eds., Management of western forests and grasslands for 

nongame birds—Workshop proceedings, Salt Lake City, Utah, February 11–14, 1980: Ogden 

Utah, U.S. Forest Service, Intermountain Forest and Range Experiment Station, General 

Technical Report INT–86, p. 451–467. 

A review of the literature on the effects of off-road vehicles revealed that OHV use has 

significant effects and can reduce numbers, diversity, and biomass of birds and other vertebrates. 

The degree of impact depends upon amount and intensity of OHV use, habitat type, and 

sensitivity of the species. 

Boarman, W.I., and Sazaki, M., 2006, A highway's road-effect zone for desert tortoises 

(Gopherus agassizii): Journal of Arid Environments, v. 65, no. 1, p. 94–101. 

Roads can affect populations of animals directly (vehicle-animal collisions) and 

indirectly (due to habitat fragmentation and dispersal/proliferation of non-native or predatory 

species). This study investigated the effect of a 2- to 4-lane highway (with a posted speed limit of 

65 mi/hr [105 km/hr] and an average daily traffic intensity of 8500 vehicles) on threatened desert 

tortoise (Gopherus agassizii) populations in the Mojave Desert, California, and attempted to 

determine the width of the road-effect zone by counting signs of tortoises (shells, tracks, scats, 

burrows, and pallets) along transects at 0, 400, 800, and 1600 m from and parallel to the edge of 

a highway. Mean sign count was 0.2/km (0.32/mi) at 0 m (0 yd), 4.2/km (6.72/mi) at 400 m 

(437.4 yd), 5.7/km (9.12/mi) at 800 m (874.9 yd), and 5.4/km (8.64/mi) at 1600 m (yd) from the 

highway edge. The differences between all distances except 800 and 1600 m (874.9 and 1749.8 

yd) were statistically significant, suggesting that tortoise populations in the study area were 

depressed within a zone extending at least 400 m (437.4 yd) from the highway. 

Brattstrom, B.H., and Bondello, M.C., 1983, Effects of off-road vehicle noise on desert 

vertebrates, in Webb, R.H., and Wilshire, H.G., eds., Environmental effects of off-road 

vehicles—Impacts and management in arid regions: New York, Springer-Verlag, p. 167–206. 

22 
This study determined that sand lizards (Uma scoparia) and kangaroo rats (Dipodomys 

deserti) suffered hearing loss lasting for weeks after being exposed to less than 10 minutes of 

playback recordings of dune buggy sounds played intermittently at intensities lower than the 

average intensity levels actually emitted by OHVs. Such impacts led to the inability of both of 

these species to respond to recordings of predator sounds. A spadefoot toad (Scaphiopus couchii) 

emerged prematurely from its burrow when exposed to 30 minutes of taped motorcycle sounds. 

Brooks, M.L., 1999, Effects of protective fencing on birds, lizards, and black-tailed hares in the 

western Mojave Desert: Environmental Management, v. 23, no. 3, p. 387–400. 

Effects of a protective (fenced) area on birds, lizards, black-tailed hares (Lepus 

californicus), perennial plant cover, and structural diversity of perennial plants were evaluated 

from spring 1994 through winter 1995 at the Desert Tortoise Research Natural Area (DTNA), in 

the Mojave Desert, California. Abundance and species richness of birds were greater inside than 

outside the DTNA; these effects, however, were more pronounced during breeding season and a 

year of high rainfall than during winter and a year of low rainfall. Nesting activity was also more 

frequent inside the exclosure. Total abundance and species richness of lizards and individual 

abundances of western whiptail lizards (Cnemidophorous tigris) and desert spiny lizards 

(Sceloporus magister) were greater inside than outside the exclosure. Black-tailed hares 

generally prefer areas of low perennial plant cover, which may explain why they were more 

abundant outside than inside the DTNA. Habitat structure may not affect bird and lizard 

communities as much as availability of food at this desert site, and the greater abundance and 

species richness of vertebrates inside than outside the DTNA may correlate with abundances of 

seeds and invertebrate prey. 

Bury, R.B., Luckenbach, R.A., and Busack, S.D., 1977, Effects of off-road vehicles on 

vertebrates in the California desert USA: Wildlife Research Report no. 8, U.S. Fish and Wildlife 

Service, Washington, D.C., p. 1–23. 

This study compared differences in avian diversity, abundance, and biomass in unused 

and OHV-disturbed sites. Compared to OHV sites, reptile species richness was 1.63 times 

greater and there were 270 more individuals at control sites. Similarly, mammal species richness 

was 1.25 times greater and there were 115 more individuals at control sites than at OHV sites. 

The potential for ground nests of birds to be crushed and incubating birds to abandon nests was 

greater in areas of high OHV activity. Indirect effects of OHV activity on vertebrates were 

primarily caused by the loss of vegetation cover. There was a positive correlation between the 

cover of creosote bush and the total number of species, abundance, and biomass of all terrestrial 

vertebrates sampled. 

Bury, R.B., and Luckenbach, R.A., 2002, Comparison of desert tortoise (Gopherus agassizii) 

populations in an unused and off-road vehicle area in the Mojave Desert: Chelonian 

Conservation and Biology, v. 4, no. 2, p. 457–463. 

This study examined habitat, abundance, and life history features of desert tortoises 

(Gopherus agassizii) on two 25-ha plots in the western Mojave Desert: one unused and one used 

by OHVs. The unused plot had 1.7 times more live plants, 3.9 times more plant cover, 3.9 times 

more desert tortoises, and 4.0 times more active tortoise burrows than a nearby area used heavily 

by OHVs; these between-plot differences were all statistically significant. Furthermore, the few 

large-sized tortoises in the OHV plot had less body mass than those in the unused area. Although 

23 
the scope of this study was limited to one paired-plot comparison, current data suggest that 

operation of OHVs in the western Mojave Desert results in major reductions in habitat and 

tortoise numbers, and possibly the body mass of surviving tortoises. 

Lovich, J.E., and Bainbridge, D., 1999, Anthropogenic degradation of the southern California 

desert ecosystem and prospects for natural recovery and restoration: Environmental 

Management, v. 24, no. 3, p. 309–326. 

Large areas of the southern California desert ecosystem have been affected by offhighway vehicle use, overgrazing by domestic livestock, agriculture, urbanization, construction 

of roads and utility corridors, air pollution, military training exercises, and other activities. 

Secondary contributions to degradation include the dispersal and proliferation of exotic plant 

species and a higher frequency of anthropogenic fire. Effects of these impacts include alteration 

or destruction of macro- and micro-vegetation elements, establishment of annual plant 

communities dominated by exotic species, destruction of soil stabilizers, soil compaction, and 

increased erosion. This paper provides a broad view of impacts on biota and cites several 

pertinent studies relative to OHV impacts on wildlife. The authors suggest that given the 

sensitivity of desert habitats to disturbance and the slow rate of natural recovery, the best 

management option is to limit the extent and intensity of impacts as much as possible. 

Luckenbach, R.A., and Bury, R.B., 1983, Effects of off-road vehicles on the biota of the 

Algodones Dunes, Imperial County, California, USA: Journal of Applied Ecology, v. 20, no. 1, 

p. 265–286. 

Algodones Dunes, the largest dune complex in California, contains many unique species; 

however, it also receives the greatest use by off-road vehicles in California. Studies of paired 

plots (unused versus OHV-impacted) and animal tracks along sand sweeps clearly demonstrated 

that OHV activities in the Algodones Dunes significantly reduced the biota. There were marked 

declines in herbaceous and perennial plants, arthropods, lizards, and mammals in OHV-used 

areas compared with nearby controls. All sand-adapted species, including several rare or 

threatened plants, were greatly reduced in habitats where OHVs operate; the biota was affected 

even by relatively low levels of OHV activity. Areas heavily used by OHVs had virtually no 

native plants or wildlife. 

Rosen, P.C., and Lowe, C.H., 1994, Highway mortality of snakes in the Sonoran Desert of 

southern Arizona: Biological Conservation, v. 68, no. 22, p. 143–148. 

A total of 368 snakes (104 live, 264 dead) were recorded over four years on a paved 

highway during 15,525 km (9,647.2 mi; mostly within Organ Pipe Cactus National Monument, 

Arizona) of driving along the road to detect amphibians and reptiles during rainfall events or 

while basking on the warm road surface. During 4 years, an estimated 2,383 snakes were killed 

on this stretch of pavement, although the actual number killed was probably closer to 4,000. 

Webb, R.H., and Wilshire, H.G., 1983, Environmental effects of off-road vehicles—Impacts and 

management in arid regions: New York, Springer-Verlag, 534 p. 

This book discusses the physical and biological effects of OHVs (recreational, mining, 

and military vehicles) on arid-land ecosystems, including effects on soils, vegetation, and 

wildlife. It also points out the loss of choices that OHV effects impose on future land users. 

Actual case studies are presented, complete with practical solutions, detailed planning measures 

24 
that can be taken to reduce the adverse effects of OHVs, methods that can be used to rehabilitate 

the physical systems and vegetation communities of disturbed areas, and management concepts 

and practices that can be employed in protecting susceptible areas, including regulations and 

education. 

2.5 OHV Effects on Water Quality 

2.5.1 Section Summary 

The direct effects of OHV activity on aquatic systems have received surprisingly little 

attention, due, in part, to the fact that OHV-impact research has focused on arid environments, 

where aquatic systems are seasonal or rare. Nonetheless, there is great potential for OHV 

activities to affect water quality in arid environs as well as well-watered regions. As described in 

Sections 2.2 and 2.3, soil properties and vegetation cover may be altered by OHV use; in turn, 

surface patterns of precipitation runoff (amount, velocity) may be altered, resulting in accelerated 

rates of erosion and sedimentation and elevated levels of turbidity in affected watersheds. Where 

slope is a factor, the extensive networks of OHV routes proliferating across landscapes can serve 

as conduits that direct or alter the direction of surface flows. These conduits may be eroded to 

form gullies that channel dislodged sediments and contaminants into aquatic ecosystems. Water 

quality also is adversely affected by OHV-raised dust that settles into aquatic systems. 

OHV-dispersed chemicals also may be transported into aquatic systems. The operation of 

OHV engines, especially 2-stroke engines, can impact water quality through spills and 

emissions. These contaminants may enter aquatic systems via direct flushing, or they may be 

adsorbed to sediments and/or absorbed by plant materials, both of which are easily transported to 

aquatic systems by precipitation runoff or wind. Spill or emission contaminants may include 1,3-

butadiene, benzene and ethylbenzene, xylenes, and toluene. Prior to the ban on leaded gasoline, 

lead levels were high in plants and animals near roads, and although the 1996 ban on leaded 

gasoline has resulted in dramatic declines in lead levels, it persists in the soil and may be 

mobilized when soils are eroded into wetlands. 

2.5.2 Sedimentation and Turbidity 

Areas naturally most susceptible to water-quality problems are those where infiltration 

rates are low, slopes are steep, the ratio of surface sand and gravel to finer particles is low, and 

where rainfall events are typically prolonged and intense (Iverson and others, 1981). Altering 

soil texture, disrupting soil crusts or desert pavement, and reducing vegetation cover can increase 

the soil’s susceptibility to erosion; in turn, rates of sedimentation and turbidity levels can 

increase and alter the water quality of a given watershed, including streams and rivers, lakes, and 

small, isolated wetlands, including vernal pools (Forman and others, 2003). Sediments can 

displace the water-holding volume of a wetland, thus diminishing or eliminating the wetland’s 

hydrological function (Luo and others, 1977). For example, where OHVs had traveled over the 

soil, Iverson and others (1981) found that surface runoff was 5 times greater and yielded 10-20 

times more sediment than where soils were undisturbed. 

Where OHV activity occurs, networks of OHV routes proliferate. Wheel cuts and tracks 

within these networks may serve as water conduits that channel and direct water flow containing 

sediments and contaminants into aquatic ecosystems (Wemple and others, 1996; Forman and 

others, 2003, p. 185–197). The generally impervious nature of soils compacted by OHV traffic 

enhances gully formation in these conduits, thus promoting additional flows of sediments and 

suspended solids into aquatic systems, effectively extending the drainage network of a given 

25 
watershed, and potentially changing the timing of peak runoff flows (Wemple and others, 1996). 

The presence of OHV-route networks is an important factor in determining the severity of 

potential sedimentation in nearby aquatic systems. In particular, Wemple and others (1996) 

found that the drainage ditches along logging roads and the gullies that form below culvert 

outlets (where drainage flows pass under a road, or cross-drains) on steep slopes served as 

primary conduits linking surface flows to streams. The extent to which sediments might be 

carried along these conduits and into aquatic systems depends primarily on the presence of 

obstructions below cross drains and the spatial intervals between them (Haupt, 1959). In 

situations where cross drains were positioned at sufficient distances from streams, the drainage 

discharge infiltrated the soil and did not contribute to sedimentation in streams (Haupt, 1959). In 

areas characterized by soils with relatively low infiltration rates, such as those compacted by 

OHV use, transport of sediments over greater distances and into aquatic systems may be 

substantial. 

Furniss and others (2000) describe similar effects of road and/or trail networks across a 

landscape. In particular, they discuss the continuous “hydrological connections” that facilitate 

sediment transport between surface flows and waterways. Furniss and others (2000) go on to list 

ways in which water and associated sediments enter stream systems from roads, including (1) 

inboard ditches (ditches perpendicular to the road footprint and that bisect the road) delivering 

runoff to a stream at a road-stream crossing, (2) inboard ditches delivering water to a cross-drain 

(culvert, dip, waterbar), (3) where sufficient discharge is available to create a gully or sediment 

plume that extends to the stream channel, (4) roads sufficiently close to streams so that the 

fillslope (road fill between the outside edge of the road and the base of the fill where it meets the 

natural ground surface) encroaches on the stream, and (5) landslide scars on the road fill. These 

connections provide direct routes for accelerated runoff transporting sediments and roadassociated contaminants to natural drainage channels. 

2.5.3 Dust and Contaminants 

Water quality also is adversely affected when fugitive dust and contaminants enter 

aquatic systems. Emissions from OHVs, particularly those with 2-stroke engines, can include a 

variety of contaminants, which may settle directly in wetlands or they may be deposited in snow 

or directly on soils during rain events, from which they may be mobilized into wetlands. Arnold 

and Koel (2006), who tested snowmelt runoff exposed to significant snowmobile emissions in 

Yellowstone National Park, detected benzene, ethylbenzene, m- and p-xylene, o-xylene, and 

toluene, and although all compounds were within the limits set by the U.S. Environmental 

Protection Agency, it is not clear what the cumulative impacts of these chemicals may be in 

watersheds. Adams (1975) found that the stamina of brook trout experimentally exposed to 

elements commonly found in snowmobile emissions, as measured by their ability to swim 

against the water current, was significantly diminished compared to that of control fish. 

Airborne dust—and contaminants adsorbed to dust particles—raised by OHV traffic may 

eventually settle directly into wetlands (Forman and others, 2003, p. 231–234). The potential for 

adsorbed contaminants to be carried along with precipitation runoff and into wetlands is also a 

concern, as are plant materials containing absorbed contaminants. Finally, contaminants may 

enter aquatic habitats by direct flushing of exposed contaminants (for example, petroleum 

puddles). Prior to the ban on leaded gasoline, lead levels were high in plants and animals near 

roads (Daines and others, 1970; Motto and others, 1970; Quarles and others, 1974; Wheeler and 

Rolfe, 1979). Although the 1996 ban on leaded gasoline has since resulted in dramatic declines 

26 
in lead levels along roadsides and in organisms, it persists in the soil and may be mobilized when 

soils are eroded into wetlands. 

2.5.4 Annotated Bibliography for OHV Effects on Water Quality 

Adams, E.S., 1975, Effects of lead and hydrocarbons from snowmobile exhaust on brook trout 

(Salvelinus fontinalis): Transactions of the American Fisheries Society, v. 104, no. 2, 

p. 363–373. 

Prior to snowmobiling season, hydrocarbon levels in the water of a pond in Maine were 

undetectable; by the time of ice-out in spring, hydrocarbon levels had reached 10 parts per 

million (ppm) in the water and 1 ppm in exposed fish. In addition, exposed brook trout 

fingerlings contained 9 to 16 times more lead than control trout. Brook trout (Salvelinus 

fontinalis) held in aquaria for 3 weeks in melted snow containing three different concentrations 

of snowmobile exhaust also showed hydrocarbon and lead uptake. Stamina, as measured by the 

ability to swim against current, was significantly less in trout exposed to snowmobile exhaust 

than in control fish. 

Brabec, E., Schulte, S., and Richards, P.L., 2002, Impervious surfaces and water quality—A 

review of current literature and its implications for watershed planning: Journal of Planning 

Literature, v. 16, no. 4, p. 499–514. 

This paper focuses on the effect of impervious surfaces on the health of nearby aquatic 

habitats. Although considerable research has been done to define watershed thresholds of 

impervious surfaces (beyond which water quality declines), there are numerous flaws in the 

assumptions and methodologies used. Given refinement of the methodologies, accurate and 

usable parameters for preventive watershed planning can be developed, including thresholds of 

impervious surfaces and balances between pervious/impervious surfaces within a watershed. 

Brown, K.J., 1994, River-bed sedimentation caused by off-road vehicles at river fords in the 

Victorian Highlands, Australia: Water Resources Bulletin, v. 30, no. 2, p. 239–250. 

This study investigated some of the effects occurring at OHV crossings on two rivers in 

eastern Australia, where many road crossings occur at low-level fords. It provides a method 

whereby the amount of sediment redeposited downstream of a ford can be measured. Attention is 

drawn to the fact that sediment is contributed to rivers by five major processes: the exposure of 

surfaces, the concentration of surface runoff in wheel ruts, soil compaction and subsequent 

reduction of water infiltration leading to increased surface runoff, backwash from the vehicle, 

and undercutting of banks by bow-wave action. The last two of these processes have not been 

reported previously. Sediment collection experiments in two upland rivers indicated a mean 

deposition rate at the stream bed of approximately 1,000 g/m2

 over a period of 30 days. 

Furniss, M.J., Flanagan, S.A., and McFadin, B.A., 2000, Hydrologically connected roads—An 

indicator of the influence of roads on chronic sedimentation, surface water hydrology, and 

exposure to toxic chemicals: U.S. Forest Service, Stream Systems Technology Center, Rocky 

Mountain Research Station, Technical Report, 4 p., 

http://www.stream.fs.fed.us/streamnt/jul100/jul100_2.htm. 

This study defines the concept of forest-road drainage as a transport system for sediment 

into streams and proposes design changes to road drainage that would prevent or minimize this 

movement. The proportion of road that is hydrologically connected to a stream network may be a 

useful indicator of the potential for several adverse effects, including (1) the delivery of road27 
derived sediments to streams; (2) hydrologic changes associated with subsurface flow 

interception, concentration, and diversion; (3) increased drainage density; (4) extension of the 

stream network; and (5) the potential for road-associated spills and chemicals to enter streams. 

Hamilton, L.J., 2002, A study of the effects of ORV stream crossings on water quality of two 

streams located in the Angelina National Forest, Texas—A physicochemical and benthic 

macroinvertebrate analysis: Masters Abstracts International, v. 40, no. 3, p. 668. 

A study was conducted for the U.S. Forest Service to determine whether OHV-based 

stream crossings affected water quality of two streams located in Texas. The sites differed most 

in turbidity, total solids, Shannon’s diversity index, dissolved oxygen, nitrate, and ratios of 

Chironomidae:EPT (Ephemeroptera + Plecoptera + Trichoptera, a common indicator of 

taxonomic richness detected during stream surveys to assess water quality), although there were 

no significant differences in the physicochemical properties. At one site, however, the upstream 

and downstream plots differed significantly in terms of two benthic indices—Hilsenhoff's Biotic 

Index and Ratio of Scrapers to Filtering Collectors. 

Katz, M., Legore, R.S., Weitkamp, D., Cummins, J.M., and Anderson, D., 1972, Effects on 

freshwater fish: Journal of the Water Pollution Control Federation, v. 44, no. 6, p. 1226–1250. 

This is a literature review of the effects of water pollutants on freshwater fish. Topics 

include (1) tests to determine the lethality of estuarine and some polluted river waters to trout 

and cyprinids; (2) estimated degrees of river pollution based on bacterial and chemical analysis 

of water samples; (3) documentation of some effects of municipal wastewater effluents on the 

water quality, fish populations, and bottom-fauna characteristics of a receiving stream; and (4) 

observations of the environmental effects of pollutants such as synthetic detergents, industrial 

wastes, and pesticides. 

Roy, A.H., Rosemond, A.D., Leigh, D.S., Paul, M.J., and Wallace, J.B., 2003, Habitat-specific 

responses of stream insects to land cover disturbance—Biological consequences and monitoring 

implications: Journal of the North American Benthological Society, v. 22, no. 2, p. 292–307. 

This study analyzed the impact of a range of physical and chemical stressors on aquatic 

insects and tested whether the effects of these stressors differed in three habitat types: riffles, 

pools, and banks. Riffle assemblages were affected by both physical (for example, streambed 

mobility) and chemical (specific conductance, nutrient concentration) variables. The density of 

aquatic insects in pools also was correlated to physical and chemical variables, but there were 

few relationships with pool or bank richness or bank density. Because relative impacts of 

disturbance in riffles were greater than in banks, the authors found greater differences between 

riffle and bank richness in streams with greater sedimentation. The proportion of bank richness 

(bank richness/bank + riffle richness) increased with finer bed sediment and increased bed 

mobility. The study also compared richness of facultative taxa (found in multiple habitats) 

between sites characterized as minimally impacted and sediment-impacted. In riffles, richness of 

facultative taxa was lower in sediment-impacted than in minimally impacted sites, but was 

similar for both disturbance groups in banks. 

Wheeler, A.P., Angermeier, P.L., and Rosenberger, A.E., 2005, Impacts of new highways and 

subsequent landscape urbanization on stream habitat and biota: Reviews in Fisheries Science, 

v. 13, no. 3, p. 141–164. 

28 
This paper emphasizes a more thorough consideration of highway impacts and, 

ultimately, better land-use decisions by conceptualizing road development in three stages: initial 

construction, road presence, and eventual landscape urbanization. Road construction is 

characterized by localized physical disturbances, which generally subside through time. In 

contrast, road presence and landscape urbanization are characterized by persistent physical and 

chemical impacts. Though not specific to OHV activity, this paper does focus on the fact that 

landscape urbanization is clearly the greatest threat to stream habitat and biota, as stream 

ecosystems are sensitive to even low levels (less than 10 percent of a given watershed) of urban 

development. Researchers know little about the occurrence, loading rates, and biotic responses to 

specific contaminants in runoff from roads. Also needed is a detailed understanding of how 

drainage crossings, especially culverts, affect fish populations via constraints on movement and 

how road networks alter natural regimes (streamflow, temperature). 

2.6 OHV Effects on Air Quality 

2.6.1 Section Summary 

Fugitive dust raised by OHV traffic on unpaved roads/trails can contribute significantly 

to air-quality problems. Also problematic are OHV emissions, particularly from 2-stroke 

engines. Currently, many OHVs in use, including off-highway motorbikes and ATVs, run on 2-

stroke engines, which do not burn fuel completely and produce significant amounts of airborne 

contaminants, including nitrogen oxides, carbon monoxide, ozone, aldehydes, and extremely 

persistent polycyclic aromatic hydrocarbons (PAH), including the suspected human carcinogen, 

methyl tert-butyl ether (MTBE). Some airborne contaminants settle onto plants or into soils and 

function as fertilizers, thus causing changes in plant community composition and altering growth 

rates. The accumulation of emissions contaminants is evident in the tissues of plants and animals 

exposed to them. Prior to the ban on leaded gasoline, lead also was prevalent in plants and 

animals near paved roads and other travel routes, and because it persists in the environment, it 

can still have impacts when contaminated soils are mobilized. 

2.6.2 Fugitive Dust Raised by OHV Traffic 

Fugitive dust (largely composed of lightweight soil particles, including silt and clay) 

suspended in the air may impact more total area than any other impact of roads (paved or 

unpaved; Forman and others, 2003), and it can have significant effects on ecosystems (Westec, 

1979). Dust is created and raised into the air as OHVs disturb soil crusts, abrade and pulverize 

soils, and generate wind currents. Once soil surfaces are disturbed, wind erosion may increase 

the amount of debris flow (Lovich and Bainbridge, 1999). In 1973, satellite photos detected six 

dust plumes in the Mojave Desert covering more than 1,700 km2

 (656.2 mi2); the plumes were 

attributed to destabilization of soil surfaces resulting from OHV activities (Nakata and others, 

1976; Gill, 1996). Along roads in Alaska heavily traveled by various types of vehicles, Walker 

and Everett (1987) found that dust had buried mosses and very low-statured vegetation in the 10-

m-wide area adjacent to each side of the road; dust blankets measured up to 10 cm (3.9 in) deep. 

Accumulations of dust on vegetation can disrupt photosynthetic and respiration processes, 

leading to reduced plant growth, reproduction, and survivorship. 

2.6.3 Contaminants Associated with OHV Use 

Before emissions controls on automobiles became significantly more effective, there was 

little concern about emissions from small engines; today, however, their relative contribution to 

29 
air-quality problems is significant (see 

http://www.egr.msu.edu/erl/Small%20Engine%20Emissions.html). This is because small 

engines, especially 2-stroke models (many of which are being phased out), do not burn fuels 

completely; thus, their emissions contain the resulting by-products of incomplete combustion, 

including nitrogen oxides NOx, sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3), 

aldehydes, and extremely persistent polycyclic aromatic hydrocarbons (PAH). In fact, a very 

small, 2-stroke engine running for 2 hours emits the same amount of hydrocarbons as driving 10 

cars (of the fuel-burning efficiency produced in 1995) for 250 miles each 

(http://www.arb.ca.gov/msprog/offroad/sm_en_fs.pdf ). 

Pollutants emitted from exhaust can cause a variety of impacts on vegetation. Carbon 

dioxide may function as a fertilizer and cause changes in plant species composition (Bazzaz and 

Garbutt, 1988; Hunt and others, 1991; Ferris and Taylor, 1995); nitrogen oxides also may 

function as fertilizers, producing similar effects along roadsides (Falkengren-Grerup, 1986; 

Holzapfel and Schmidt, 1990; Angold, 1997). Spencer and Port (1988) found that the soluble 

nitrogen content of perennial ryegrass (Lolium perenne) plants growing within 0-6 m (0-6.6 yd) 

of a paved road than in plants growing more than 6 m (6.6 yd) from the road, which contributed 

to greater growth rates and fecundity of aphids (Rhopalosiphum padi) inhabiting the plants 

closest to the road. Sulfur dioxide, which can be taken up by vegetation, may result in altered 

photosynthetic processes (Winner and Atkison, 1986; Mooney and others, 1988). 

Several species of Mojave Desert perennials and annuals were fumigated in experimental 

chambers to determine their sensitivities to SO2, nitrogen dioxide (NO2), and O3; Thompson and 

others, 1980; Thompson and others, 1984). Creosote bush (Larrea sp.), the only perennial 

species found to be sensitive to SO2 and NO2, exhibited leaf injury and reduced growth when 

exposed to SO2 and NO2; however, numerous annuals, including redstem stork’s bill (Erodium 

cicutarium) and desert Indianwheat (Plantago insularis; extremely sensitive), cleftleaf 

wildheliotrope (Phacelia crenulata; very sensitive), and wooley desert marigold (Baileya 

pleniradiata), exhibited more dramatic effects, including extensive injury and death (Thompson 

and others, 1980). Another study by Thompson and others (1984) revealed several annual 

species that are extremely sensitive to SO2 and O3, including brown-eyed primrose (Camissonia 

claviformes), Santa Cruz Island suncup (C. hirtella), and Nevada cryptantha (Cryptantha 

nevadensis). 

OHV emissions also contain a variety of heavy metals, including zinc, copper, nickel, 

chromium, and lead (National Research Council, 1986). In terms of overall quantity, lead was 

one of the most significant heavy metals emitted prior to the ban on leaded gasoline in 1996 

(Daines and others, 1970; Motto and others, 1970; Quarles and others, 1974; Wheeler and Rolfe, 

1979). At least in desert regions, concentrations of lead particulates along roads were positively 

correlated with traffic volume (Motto and others, 1970). Within 80 m (87.5 yd) of roadsides, 

Quarles and others (1974) found that lead concentrations diminished notably from road edges 

(543 and 190 ppm) to 10 m (47 and 5 ppm, respectively) away from the edge; beyond 80 m, 

accumulations of lead diminished at lower rates. The declining gradient in lead concentrations 

away from roadsides may have been due, in part, to the direction of surface water flow (Byrd and 

others, 1983) as soil and other debris to which lead adheres were flushed away by the volume of 

water that runs off road surfaces. Although lead emissions from gasoline have declined 

dramatically since control policies were implemented in the 1970s (Forman and others, 2003), it 

persists in soils and can continue to move through the environment when contaminated soils are 

dislodged. 

30 
2.6.4 Annotated Bibliography for OHV Effects on Air Quality 

Agrawal, Y.K., Patel, M.P., and Merh, S.S., 1981, Lead in soils and plants—Its relationship to 

traffic volume and proximity to highway (Lalbag, Baroda City): International Journal of 

Environmental Studies, v. 16, no. 3–4, p. 222–224. 

Accumulations of lead from motor-vehicle exhausts on soils and trees growing along a 

busy thoroughfare in the Lalbag area of Baroda City were studied. Analysis of soils and tree 

samples showed that the distribution of emitted lead was influenced by the direction of the 

prevailing wind. Lead concentrations in plants and soils near the roadside were greater than they 

were in soils and plants 4–6 m away from the roadside. 

Bazzaz, F.A., and Garbutt, K., 1988, The response of annuals in competitive neighborhoods—

Effects of elevated CO2: Ecology, v. 69, no. 4, p. 937–946. 

Four members of an annual plant community were used to investigate the effects of 

changing neighborhood complexity and increased carbon dioxide (CO2) concentration on 

competitive outcome. Plants were grown in monoculture and in all possible combinations of two, 

three, and four species in CO2-controlled growth chambers at CO2 concentrations of 350, 500, 

and 700 microliters/liter (μL/L) (1 ppm), with ample moisture and light. Species responded 

differently to enhanced CO2 level. The biomass of some species (Abutilon theophrasti, for 

example) increased with increasing CO2, while that of others (Amaranthus retroflexus) decreased 

with increasing CO2 concentration. The potential effects of CO2 on community structure could 

be profound, particularly at the intermediate levels of CO2 that are predicted for the first half of 

the 21st century. 

Gish, C.D., and Christensen, R.E., 1973, Cadmium, nickel, lead, and zinc in earthworms from 

roadside soil: Environmental Science and Technology, v. 7, p. 1060–1062. 

Cadmium (Cd), nickel (Ni), lead (Pb), and zinc (Zn) in soils and earthworms along two 

Maryland highways decreased with increasing distance (10, 20, 40, 80, and 160 ft) from the road. 

Along each highway, metal residues were greater where traffic volume was greater. Correlations 

between residues in earthworms and soil decreased with decreasing atomic weights (Pb, Cd, Zn, 

Ni). Metal residues in soils were positively correlated with quantities of soil organic matter. 

Earthworms accumulated up to 331.4 ppm of Pb and 670.0 ppm of Zn, concentrations that may 

be lethal to earthworm-eating animals. 

Motto, H.L., Daines, R.H., Chilko, D.M., and Motto, C.K., 1970, Lead in soils and plants—Its 

relationship to traffic volume and proximity to highways: Environmental Science and 

Technology, v. 4, p. 231–237. 

Lead concentrations increased with traffic volume and decreased with distance from 

highways. Much of the lead was present as removable surface contamination on plants, and 

major effects were limited to the soil surface within 100 ft (30.48 m) of the highway. 

Nakata, J.K., Wilshire, H.G., and Barnes, G.C., 1976, Origin of Mojave Desert dust plumes 

photographed from space: Geology, v. 4, p. 644–648. 

OHV-raised dust has been an enormous problem in the Mojave Desert, as illustrated by 

satellite photos that revealed six dust plumes covering more than 1,700 km2

 (656.4 mi2) of the 

western Mojave region in January 1973; the dust plumes were attributed to destabilization of 

ground surfaces, primarily from OHV activity. 

31 
Quarles, H.D., Hanawalt, R.B., and Odum, W.E., 1974, Lead in small mammals, plants, and 

soil at varying distances from a highway: Journal of Applied Ecology, v. 11, no. 3, p. 937–949. 

Lead particulates were measured at varying distances from three highways. Lead 

concentrations were greatest within 10 m (10.9 yd) of the highways. Lead concentrations in the 

soil along two transects dropped from 543 ppm and 190 ppm at the road edge to 47 ppm and 5 

ppm 10 m from the road edge. Both plants and animals were susceptible to lead uptake. 

Spencer, H.J., and Port, G.R., 1988, Effects of roadside conditions on plants and insects. II. Soil 

conditions: Journal of Applied Ecology, v. 25, no. 22, p. 709–715. 

An experiment was done to investigate the performance of plants (Lolium perenne) 

grown in roadside soil. Significantly fewer plants germinated in soil taken 0 to 6 m from the road 

compared with soil taken 6 m from the road. For a given population size, however, plants grown 

in soil taken from beside the road attained significantly greater dry weight and significantly 

greater soluble nitrogen content. Nitrogen oxide emissions, identified as the probable cause of 

these effects, were absorbed by the roadside soil and subsequently assimilated by the plants. 

Thompson, C.R., Olszyk, D.M., Kats, G., Bytnerowicz, A., Dawson, P.J., and Wolf, J.W., 1984, 

Effects of ozone or sulfur dioxide on annual plants of the Mojave Desert: Journal of the Air 

Pollution Control Association, v. 34, no. 10, p. 1017–1022. 

Forty-seven species of annual plants from the Mojave Desert were grown in pots and 

exposed in open-top field chambers located at Riverside, California, to test their relative 

sensitivity to SO2 and O3. Species differed widely in their response to the pollutants. Three 

species, Camissonia claviformis, Camissonia hirtella, and Cryptantha nevadensis, were quite 

sensitive to both pollutants, exhibiting leaf injury when exposed to 0.1 ppm O3 or 0.2 ppm SO2. 

The other species were intermediate in sensitivity, and O3 sensitivity did not always correspond 

to SO2 sensitivity. For 8 of 11 species tested, total sulfur concentration was greater in plants 

exposed to 0.2 ppm SO2 than in unexposed plants. Baileya pleniradiata and Perityle emoryi

exhibited the greatest increases in sulfur concentration for exposed versus control plants. 

Walker, D.A., and Everett, K.R., 1987, Road dust and its environmental impact on Alaskan taiga 

and tundra: Arctic and Alpine Research, v. 19, no. 4, p. 479–489. 

The physical and chemical characteristics and ecological consequences of road dust in 

arctic regions were reviewed with emphasis on recent information gathered along the Dalton 

Highway and the Prudhoe Bay Spine in northern Alaska. Enhanced dust-control measures were 

considered, particularly where the road passes through scenic lichen woodlands, acidophilic 

tundra, and in calm valleys where dust commonly was a traffic-safety hazard. 

Westec Services Inc., 1979, Fugitive dust impacts during off-road vehicle (ORV) events in the 

California desert: Tustin, California, WESTEC Services, Inc., Technical Report, 40 p. 

Results and analysis of dust monitoring for five desert races demonstrated that factors 

such as distance from the point of generation, soil moisture, soil characteristics, wind, and 

relative humidity, as well as the type and number of vehicles in the race, had the largest effect on 

the amount and type of dust, particulate size, how quickly it settled, and the extent of the human 

health hazard present during the race. Long period (daily) dust-exposure levels were 10 times 

32 
greater than the standard, whereas short period (hourly) dust levels were 100 times greater than 

the standard under adverse conditions near the race activity. 

2.7 Socioeconomic Implications of OHV Use 

2.7.1 Section Summary 

The socioeconomics of OHV use include OHV user demands, concerns, and attitudes; the 

economic effects of OHV use on communities near OHV-use areas; the economics of managing 

OHV activities; the effects of OHV use on non-motorized recreators; and the economics of 

losing ecosystem services. Although not currently addressed through BLM’s indicators of 

rangeland health, natural resource attributes are heavily influenced by socioeconomic factors. 

Since the mid 1980s, the incidence of OHV use on public lands has increased substantially, and 

this trend is expected to continue. Moreover, the economic benefits from travel expenditures and 

the sales of supplies and equipment in communities bordering OHV-use areas generates 

significant pressure to maintain or increase current levels of OHV activity. As OHV activity 

increases, however, increasing stress is placed on natural resources, land managers who must 

monitor and regulate OHV activities, and visitors seeking non-motorized forms of recreation. 

2.7.2 Trends in OHV Use and Technology 

In a survey of Utah OHV users commissioned by the Utah Department of Natural 

Resources, Fisher and others (2001) found that public lands are primary destinations among most 

users; only one quarter of survey respondents took trips to private land. More specifically, BLM 

land was the primary destination for ATV, motorcycle, and 4 x 4 vehicle users; U.S. Forest 

Service land was the secondary destination among ATV and 4 x 4 users; and State land was the 

secondary destination among motorcycle users (Fisher and others, 2001). Increasing OHV use is 

likely to be accompanied by greater demand for places where OHVs can be used, particularly 

near urban areas and corridors; as urban populations increase, so do the numbers of recreators on 

nearby public lands, thereby putting more stress on the landscape (Brooks and Champ, 2006). 

The increasing demands also pose problems for land managers already balancing the needs of a 

dynamic land base, often with limited budgets and/or staffing (Brooks and Champ, 2006; Rocky 

Mountain Research Institute, 2002). These limitations constrain land managers but not OHV use; 

thus, OHV recreation is largely “unmanaged.” In addition, technology advancements in outdoor 

recreation equipment have led to production of OHVs that easily access lands previously 

unimpacted by mechanized recreation (Meine, 1998; Ewert and Shultis, 1999). As a result, new 

problems have arisen for both previously unimpacted areas and backcountry users who now 

encounter OHVs. Problems potentially arising from a constrained ability to manage lands 

include resource degradation, displacement of wildlife, and conflict among users, both within 

and across user types. 

2.7.3 Types, Sources, and Effects of OHV User Conflict 

Much of the OHV literature addresses conflicts between OHV users and other land users, 

even those who are not directly affected by OHV users. Researchers have addressed conflict 

issues by using a variety of tools or models designed to help managers understand and reduce 

conflicts between or among user groups. Bury and others (1983, p. 401) describe conflict as 

existing “whenever incompatible activities occur” and offer three elements that contribute to the 

incompatibility of activities: spatial and temporal proximity, dominance over the environment, 

and dependence on technology. When the proximity of activities does not result in direct or 

33 
indirect (seeing the effects of other uses) encounters among user types, then environmental 

dominance and technological dependence are more likely to come into play. Dominance over the 

environment refers to how much an individual feels the need to exert some kind of control over 

the environment. Dependence on technology can cause conflict when people who retreat to 

backcountry to seek solace from modern technology clash with those who use technology to 

enhance their outdoor experiences. Conflict also occurs between land users and land managers. 

Inconsistent management policies across different land management agencies can cause such 

conflict, particularly as OHV recreation is ushered from being “unmanaged” to “managed.” On 

many public lands, trails are currently considered open unless posted as closed, and once a trail 

has been established by users, it is often considered open for use (Brooks and Champ, 2006). 

Graefe and Thapa (2004) outline some of the traditional approaches to examining user 

conflicts through research, including studies of goal interference (first introduced by Jacob and 

Shreyer, 1980). Goal interference occurs when a user comes into direct (seeing the conflicting 

recreation type) or indirect (seeing the effects of a recreation type) contact with another user type 

and is impeded from accomplishing the desired purpose of his or her recreation (Badaracco, 

1976). The factors that contribute to goal interference are activity style, resource specificity, 

mode of experience (whether individuals are focused or unfocused), and tolerance for lifestyle 

diversity. Another model classifies conflict as either interpersonal conflict or a conflict of social 

values (Vaske and others, 1995). Interpersonal conflict is similar to goal interference in that a 

user has a problem with another use type and encounters an individual participating in, or 

evidence of, that type (hearing OHV noise, for example). Social values conflict occurs regardless 

of whether or not differing user types encounter one another—just knowing that the other 

recreation type is permitted may be unacceptable. 

In the literature on user conflict, conflict is more often characterized as one-sided than 

two-sided (Badaracco, 1976; Bury and others, 1983; Watson and others, 1997; Graefe and 

Thapa, 2004). For example, while backpackers may perceive OHV users as disruptive to their 

experience, it is less likely that OHV users will find backpackers disruptive to their experience 

(Jackson and Wong, 1982). Displacement is the most common personal coping mechanism by 

which conflict is abated (Watson et al, 1997; Graefe and Thapa, 2004). That is, if an individual 

feels negatively enough about certain recreational activities occurring in the area he/she wishes 

to use, there is a possibility that the individual will simply forgo recreating in the area altogether, 

thereby increasing the probability that area managers will gradually lose support from that user 

base (Watson and others, 1997; Graefe and Thapa, 2004). 

2.7.4 OHV Users and Their Preferences 

Overall, understanding the social effects of OHV use requires understanding the full 

array of recreational activities sought and the preferences of both OHV and non-OHV users 

alike. For example, people engaged in camping may include both OHV and non-OHV users, 

which can result in dissatisfaction among campers. In a survey of campers that included both 

OHV and non-OHV users, 66 percent indicated that having a regulated OHV riding area nearby 

would make their stay more enjoyable because it would reduce the number of riders in other 

areas and maintain a safer environment for both riders and campers (Bury and Fillmore, 1974). 

When given a choice between having (1) no motorcycle riding area but permission to ride on 

campground roads, (2) prohibition of all motorcycle riding, or (3) a nearby motorcycle area and 

no permission to ride on campground roads, 75 percent of riders and campers surveyed preferred 

the third alternative (Bury and Fillmore, 1974; riders and campers were socioeconomically 

similar). 

34 
Fisher and others (2001) reported that although 63.2 percent of motorcycle users 

surveyed did not stop to engage in any other type of recreational activity, almost 60 percent of 

ATV owners and 75 percent of 4 X 4 vehicle owners did engage in other recreational activities 

during their trips. Of those OHV users who did stop to engage in additional recreational 

activities, hiking was the most popular (>75 percent of motorcycle/4 X 4 vehicle users and 20 

percent of ATV users). Hunting was the other most common recreational activity among ATV 

users and the second most common activity among 4 X 4 vehicle users; other recreational 

activities included fishing, camping, and sightseeing (Fisher and others, 2001). 

Overall, the results of the user preference surveys discussed previously reveal a 

potentially conflicted OHV user base in that the quality of their associated recreational activities 

could be affected by OHV activities. For example, campers who wish to ride OHVs for 

additional recreation, but who feel strongly that OHV use should be restricted to designated 

areas, are likely to feel dissatisfied if other OHV users ride through the campground and/or on 

hiking trails. Similarly, if OHV use in preferred hunting or fishing areas—or other areas crucial 

to healthy populations of game and fish species—degrades habitat quality that results in 

diminished game and fish populations, then OHV riders who also hunt and fish may experience 

dissatisfaction. 

Understanding the social effects of OHV activities (and potential outcomes of OHV 

activities) also requires determining where OHV users like to go and what their preferences are 

while riding. For example, in Colorado (where user attitudes are likely relatively moderate), 

Crimmins (1999) reported that 

• 38.5 percent of OHV riders use U.S. National Forest Service land, 

• 22.4 percent use private land, 

• 18.6 percent use BLM land, 

• 6.0 percent use State land, 

• 3.4 percent use City or county land, and 

• 2.3 percent use National Recreation Areas. 

These data indicate that the use of public lands for OHV riding far outweighs that of private 

lands. Crimmins (1999) further reported OHV user preferences in terms of riding area attributes, 

which included 

• no fee for use (if on public land), 

• signs indicating all activities allowed on the trail, and 

• locations removed from other human activity. 

The least important attributes included 

• patrolling by staff of land management agencies or local OHV clubs, 

• restrooms, and 

• loading ramps (Crimmins, 1999). 

When presented with a list of priorities for uses of public funds, OHV users selected 

• purchasing right-of-ways for OHV access, 

• new OHV trail construction, 

• erosion control, and 

• OHV trail system planning and maintenance. 

The low ranking of management patrols probably indicates that users desire more flexibility 

regarding where they may ride (Crimmins, 1999). Crimmins (1999) also pointed out that 

although the availability of facilities ranked low in terms of user preferences, management 

35 
agencies nonetheless generally focus on providing facilities and generally report high user 

demand. 

In terms of OHV user preferences for trail types and features, Bury and Fillmore (1974) 

reported that variation in terrain was the most important factor. The authors’ recommendations 

for an effective OHV area included 

• riding areas established near some, but not all, campgrounds; 

• trails kept ≥600 feet (183 m) from the nearest campground; 

• trails ≤6 feet (1.83 m) wide; and 

• trails that traverse hillsides and include a variety of technical (obstacles, rugged terrain) 

and non-technical (no obstacles, smooth riding surface) features. 

Fisher and others (2001) reported that motorcycle and ATV riders in Utah preferred 

• riding off established trails (38.1 and 49.4 percent, respectively), 

• double-track trails (12.7 and 17.1 percent), 

• single-track trails (12.7 and 4.3 percent), 

• moto-cross or ATV courses (9.5 and 15.1 percent), and 

• roads (11.1 and 4.3 percent). 

The issue of traveling off established trails is a serious concern with respect to natural 

resource management (Forman and others, 2003; Petersen, 2006); however, areas closed to 

OHVs and a shortage of designated OHV areas are common complaints among users (Achana, 

2005; Fisher and others, 2001; Nelson and others, 2000). For example, in a survey commissioned 

by the Utah Department of Natural Resources to identify the most important issues affecting 

OHV use in Utah, 42.3 percent of respondents indicated that “Having enough places to ride” was 

most important; 8.4 percent indicated “Too many areas closed to OHV use;” and 5.6 percent 

indicated that “Resource management conservation” was the most important issue (Fisher and 

others, 2001). In a survey conducted by Nelson and others (2000), 44.6 percent of respondents 

selected “Do not reduce current trail/route system and OHV access” to indicate the most 

important thing that should not be changed, and 30.1 percent selected “Develop more 

trails/routes/area and connections to services” to indicate the most important thing that should be 

changed. When provided with several OHV-management statements with which to agree or 

disagree, Crimmins (1999) found that “Most trail closures have been done for good reason” 

received the highest level of disagreement. 

Similar patterns in attitudes and beliefs were revealed through a survey of 336 ATV and 

motorbike users conducted by the Idaho Department of Parks and Recreation (Achana, 2005). 

On a scale of 0-7 (from least to most serious), respondents were asked to rank 23 issues of 

concern to them. Results indicated that the most serious issues of concern (in descending order of 

seriousness; scores greater than 4) were 

• permanent closure of an area the recreator uses most, 

• temporary closure of an area the recreator uses most, 

• inattentive/careless recreators engaged in motorized recreation, 

• litter, 

• too many rules and regulations, and 

• poor communication of rules and regulations. 

Conversely, respondents felt that issues they were not were not concerned with (in ascending 

order of seriousness; scores less than 3) were 

• too few rules and regulations, 

36 
• inadequate facilities at campsites, 

• ATV impacts on water, 

• motorcycle impacts on water, 

• problems with parking availability for OHV-support vehicles, 

• lack of suitable campsites, 

• ATV impacts on wildlife, and 

• some other (unlisted) issue of concern in OHV use areas. 

Issues of concern that fell in the middle (in descending order of seriousness) were 

• inattentive/careless non-motorized recreators, 

• OHVs traveling too fast, 

• motorcycle impacts on soil, 

• motorcycle impacts on vegetation, 

• ATV impacts on vegetation, 

• hunters on OHVs off designated roadways and trails, 

• ATV impacts on soil, 

• motorcycle impacts on wildlife, and 

• noise from OHVs. 

When asked which of 16 possible factors contributed to creation of unauthorized trails in 

recreational regions of Idaho, survey respondents selected (from most to least frequently) 

• belief that OHV users should be free to go anywhere, 

• lack of enough designated places to ride, 

• avoidance of crowded designated areas, 

• lack of operator experience, 

• riding motorcycles for fun, 

• treeless terrain, 

• riding ATVs for fun, 

• using ATVs for hunting access, 

• lack of enforcement regulations, 

• using motorcycles for hunting access, 

• using ATVs for camping, 

• inadequate regulation, 

• using motorcycles for camping, 

• using motorcycles for fishing access, 

• using ATVs for fishing access, and 

• some other (unlisted) regional resource impact. 

Combined, the top three possible factors contributing to creation of unauthorized trails indicate 

that closures of OHV areas could result in at least local increases in dispersed use. Finally, when 

presented with a list of four alternatives for creating uniform OHV access requirements to all 

recreation areas, trails, and roads on Idaho public lands, 53 percent of the respondents selected 

the alternative “Open to OHVs unless posted as closed by signing,” and 33 percent selected the 

alternative “Open to OHVs unless posted as closed by signing, designation, or description.” Only 

6.1 and 1.0 percent felt that areas should be “Closed to OHVs unless open by signing, 

designation, or description” or “Closed to OHVs unless open by signing,” respectively (6.7 

percent did not respond to this question). These results are consistent with the top possible 

37 
factors contributing to creation of unauthorized trails: the belief that OHV users should be free to 

go anywhere unless posted as closed by signing, designation, or description. 

2.7.5 Economic Benefits and Costs of OHV Use 

The economic benefits resulting from OHV sales, operation and maintenance, and 

associated sales and activities have been well documented (American Motorcyclist Association, 

1978; Dave Miller Associates, 1981; Reed and Hass, 1989; Dean Runyon Associates, 2000; 

Nelson and others, 2000). OHV recreation and camping, in particular, can generate significant 

revenues for local economies through campground fees, grocery sales, eating and drinking in 

restaurants, and sales associated with operating and maintaining OHVs and support vehicles. In 

1999, camping at public campgrounds on local, State, BLM, and U.S. Forest Service lands in 

California generated $500 million; an additional $130 million was spent solely on going to and 

from the campground and/or home (Dean Runyon Associates, 2000). A study conducted in 1988 

by Reed and Hass (1989) indicated that, during a 12-month period in 1987-1988, Colorado OHV 

users spent $488.7 million on OHV purchases, operation and maintenance, support equipment 

(tow trailers, storage sheds, and so on), and travel expenses associated with OHV trips. Nelson 

and others (2000) reported that, between July 1998 and June 1999, the average Michigan OHV 

licensee spent $1,944 on non-trip related purchases, 80 percent of which was for equipment. 

When extrapolated to the estimated number of licensees in Michigan, Nelson and others (2000) 

found that this amounted to $134 million in spending on equipment; a similar extrapolation 

indicated that $40 million was spent on local trips. 

The literature search conducted for this report, as well as personal communications with 

experts working in the field of outdoor recreation socioeconomics, revealed no published studies 

on the socioeconomic costs generated by OHV use. These costs could include the degradation or 

loss of ecosystem services, the costs of restoring OHV sites, and the loss of revenues from nonmotorized recreators who seek alternate areas for recreation where motorized recreation does not 

occur. Examples of degraded or lost ecosystem services would be the diminished capacity for a 

given watershed to provide high-quality water, diminished water infiltration into aquifers, and 

flooding resulting from increased runoff where soils become compacted. Lost constituencies 

(and associated revenues) could include not only non-motorized recreators, but also hunters and 

anglers whose primary recreational foci (wildlife and fish) may have undergone population 

declines due to the effects of OHV use. At this time, however, the true benefit:cost ratio of OHV 

use remains unknown. 

2.7.6 Annotated Bibliography for Socioeconomic Implications of OHV Use 

Badaracco, R.J., 1976, ORVs—Often rough on visitors: Parks and Recreation, v. 11, no. 9, p. 

32-35, 68-75. 

This paper first reviews relevant literature on user conflict and discusses the onesidedness of conflicts between OHV and non-OHV users, as well as the spatial nature of 

conflicts that occur when non-OHV users seek solitude and quiet and OHV users seek places for 

challenge and adventure. The paper then describes the ISD (impairment, suppression, 

displacement) syndrome: impairment is the diminished enjoyment among non-OHV users when 

they come into direct or indirect contact with OHV impacts; suppression is reduced 

participation of the non-OHV group; and displacement is the abandonment of a site impacted by 

OHV activity. Land planners and managers often misinterpret displacement as disinterest in the 

abandoned activity and, in so doing, may focus management efforts and other resources on OHV 

user demands. 

38 
Bury, R.L., and Fillmore, E.R., 1974, Design of motorcycle areas near campgrounds—Effects 

on riders and non riders: College Station, Texas, Department of Recreation and Parks, Texas A 

& M University, Technical Report, 72 p. 

This document analyzes some of the psychological and sociological effects of 

constructing motorcycle riding areas adjacent to fixed-site campgrounds. It describes rider and 

camper profiles, rider and camper perceptions of riders, and camper and rider preferences and 

satisfactions with respect to the proximity and design of riding areas. 

Cordell, H.K., Betz, C.J., Green, G., and Owens, M., 2005, Off-highway vehicle recreation in 

the United States, regions, and states—A national report from the National Survey on Recreation 

and the Environment (NSRE): U.S. Forest Service, Southern Research Station, Technical Report, 

90 p. 

This report was prepared for the U.S. Forest Service’s National OHV Policy and 

Implementation Teams. The data from the NSRE were collected between the fall of 1999 and 

late 2004. The focus of this report is off-highway driving of motor vehicles. The 15 July 2004, 

U.S. Forest Service draft rule regarding management of motorized vehicle use has increased 

attention on where and how OHV recreation occurs and is offered. As public land managers are 

tasked with the responsibility of examining and implementing clear and consistent agency 

policy, understanding who the OHV recreators are has become ever more important. The 

growing use of motor vehicles is prompting the Forest Service to revise its management of this 

use so that the agency can continue to provide opportunities desired by the public, while 

sustaining National Forest System lands. 

Crimmins, T., 1999, Colorado off-highway vehicle user survey—Summary of results: Denver, 

Colorado, Colorado State Parks, Technical Report. 

This report summarizes a State Parks user survey designed to elucidate OHV rider-use 

patterns, what riders want in a recreation area, enthusiast values and beliefs, use of OHVs in 

hunting, how the state OHV fund should use the funds collected, and rider perceptions of how 

OHV funds are used, lands are allocated, and routes are managed. 

Dave Miller Associates, 1981, An economic/social assessment of snowmobiling in Maine: 

Windham, Maine, Dave Miller Associates, Technical Report, 52 p. 

This summarizes a user survey covering economics (number of trips, distance traveled, 

duration, fuel, lodging, equipment) and analyzing the statewide impacts and trends indicated by 

the responses. (No information on demographics or user perception was gathered.) 

Dean Runyan Associates, 2000, Campers in California—Travel patterns and economic impacts: 

Portland, Oregon, Dean Runyan Associates, Technical Report, 76 p. 

This document charts the distribution of camping opportunity according to type of 

environment and land ownership, tallies the results of a questionnaire distributed to people using 

public campgrounds, and develops a comprehensive profile of camping travel patterns, 

demographics, and expenditures. The report provides significant detail on a wide range of 

camping patterns, such as how many trips, how long and where, a breakdown of the activities 

pursued by campers once on site, and the ethnic and income classifications of campers. Although 

not OHV-specific, it shows where OHV recreation fits into the big picture. 

39 
Decker, D.J., Krueger, R.A., Bauer, Jr., R.A., Knuth, B.A., and Richmond, M.E., 1996, From 

clients to stakeholders—A philosophical shift for fish and wildlife management: Human 

Dimensions of Wildlife, v. 1, no. 1, p. 70-82. 

This paper begins with a call for wildlife professionals to “adopt and use the term 

stakeholder,” the development of which they review and the definition of which they indicate as 

being any citizen potentially affected by or having a vested interest in an issue, program, action, 

or decision leading to an action. The authors maintain that successful natural resource 

management in today’s society requires recognizing the array of stakeholders that demand a 

voice or involvement in decision-making about natural resource management. The authors 

describe taking a stakeholder approach to planning and decision-making in natural resource 

management by including all those who might be impacted by natural resource management 

decisions (the authors focus on fish and wildlife management, but the principle is applied 

throughout natural resource management). The process entails developing communication 

strategies for understanding and representing stakeholder concerns, attitudes, and conflicts. The 

authors maintain that today’s successful professional resource managers need to “...seek a 

widely recognized image of giving unprejudiced consideration to all significant stakeholder 

interests in management decisions.” 

Fisher, A.L., Blahna, D.J., and Bahr, R., 2001, Off-highway vehicle uses and owner 

preferences in Utah: Logan, Utah, Institute for Outdoor Recreation and Tourism, Department of 

Forest Resources, Utah State University, Report no. IORT PR2001–02, 80 p. 

This study entailed an OHV user survey to examine owner characteristics, attitudes, and 

preferences. Respondents were selected at random from Utah OHV registrations and interviewed 

by telephone. This was a very extensive questionnaire, including the verbatim responses to 

interviewers’ open-ended questions. Other questions included demographics, vehicle type used, 

where ridden, distance traveled, types of riding preferred, attitudes toward OHV program fund 

use, attitudes toward training and safety, and much more. 

Jim, C., 1989, Visitor management in recreation areas: Environmental Conservation, v. 16, no. 1, 

p. 19–32. 

This paper discusses various visitor-management measures for diminishing or precluding 

the effects of visitor impacts on natural resources in recreation areas by employing existing 

recreation-management research on visitor decisions—such as trip duration, difficulty, and 

desired environment—to suggest ways of dispersing use into patterns that do not result in 

damage to natural resources. It also examines various management scenarios: signs and maps to 

direct users into a managed pattern, restricting admission, lotteries, and various rationing/pricing 

concepts. 

Kockelman, W.J., 1983, Management Concepts, in Webb, R.H., and Wilshire, H.G., eds., 

Environmental effects of off-road vehicles—Impacts and management in arid regions: New 

York, Springer-Verlag, p. 399–446. 

Noise and motorized intrusion were the major impacts of ORVs on non-OHV users. 

Permitting OHV activity on public land is described as “inefficient” in the goal to provide for 

multiple uses because the noise, dust, and speed of just one OHV can exclude all other recreators 

from an area. The author categorizes OHV users as work-related users, recreational users, or 

40 
“bad apples.” Work-related users are natural resource managers and utility workers, among 

others. Recreators are further categorized as casual (value aesthetics more than the challenges of 

riding) or endurance riders. “Bad apples” are characterized by a complete lack of concern about 

their impacts and are likely to be noncompliant with regulations. 

Nelson, C.M., and Lynch, J.A., 2001, A usable pilot off-road vehicle project evaluation: East 

Lansing, Michigan, Department of Park, Recreation and Tourism Resources, Michigan State 

University, Technical Report, 50 p. 

This report details the results of an interagency effort to increase compliance with OHV 

rules in a Michigan State forest. An OHV-rider survey asked for respondents’ perceptions of 

signs, maps, and trail systems in the pilot area, as well as rider perceptions of any law 

enforcement contact riders may have had during the study period. The survey also queried each 

respondent’s understanding of pilot area regulations and offered the opportunity to give openended comments. There is also a detailed discussion of the participating law enforcement 

agencies’ response to the pilot project, including officer concerns, jurisdiction conflicts, 

workload distribution vs. agency priorities, and an analysis of sign survival in the pilot project 

areas. Finally, interviews with park manager/grant recipients and discussion of the results in 

terms of park administration, funding, staffing, and resource protection are provided. 

Nelson, C.M., Lynch, J.A., and Stynes, D.J., 2000, Michigan licensed off-road vehicle use and 

users 1998–99: East Lansing, Michigan, Department of Park, Recreation and Tourism 

Resources, Michigan State University, Technical Report, 49 p. 

This details a survey of randomly selected OHV owners in 1999. In addition to questions 

about demographics, expenditures, type of OHVs owned, and preferred activities, respondents 

were queried about their perceptions of specific aspects of the State OHV program. One section 

is dedicated to comparing this survey with a similar survey from 1988. 

Propst, D.B., Shomaker, J.H., and Mitchekkm, J.E., 1977, Attitudes of Idaho off-road vehicle 

users and mangers: Moscow, Idaho, College of Forestry, Wildlife and Range Sciences, 

University of Idaho, Technical Report, 30 p. 

This report provides background information on, and an introduction to OHV use in, the 

era when it was new and poorly understood, and includes one of the earliest OHV/OSV (oversnow vehicle) user surveys. It compares user and land manager responses in the same survey; 

both groups were queried about their perceptions of environmental impacts, causes of conflicts, 

uses of public money for facilities, regulation enforcement, impacts on wildlife, and reasons for 

pursuing OHV/OSV activities. 

3.0 Potential Indicators for Evaluating and Monitoring OHV Effects 

3.1 Summary 

There are numerous parameters that have the potential for serving as indicators of OHV 

effects in monitoring or research programs. Every attempt was made to provide an inclusive list 

of potential indicators of OHV effects described in the OHV effects literature (listed below). Of 

those listed, some correspond with BLM’s 17 indicators of rangeland health; others are quite 

different but could provide supplemental data for evaluating or monitoring OHV effects (for 

41 
example, erosion and/or sedimentation rates would complement assessments of rill formation 

and other surface changes) or fill indicator voids (such as those pertaining to wildlife ecology). 

 (1) Soil health and watershed condition

• Soil strength 

• Soil bulk density 

• Water infiltration rate 

• Permeability 

• Erosion and sedimentation rate 

• Sedimentation or turbidity in wetlands 

• Surface changes (for example, formation of rills, gullies, and terracettes) 

• Presence/condition of soil crusts (in some cases: depending on crust type) 

(2) Vegetation health

• Plant community composition (including species diversity, ratio of native 

to non-native or invasive species, structural diversity) 

• Abundance of individuals and/or stem density 

• Percent vegetation cover 

• Plant size 

• Growth rate 

• Biomass 

(3) Habitat condition and health of wildlife populations (direct and indirect) 

• Habitat patch size and connectivity 

• Wildlife community composition (including species diversity, ratio of 

native to non-native or invasive species) 

• Abundance, density, and distribution 

• Population sizes and trends 

• Survivorship, productivity, body mass, and roadkill rates 

• Age-class and gender structure 

• Frequency of OHVs passing through a given area 

• Road or trail type and width 

• Level (decibels), duration, and timing of traffic noise 

(4) Water quality

• Sedimentation rate 

• Levels of turbidity and suspended solids 

• Contaminants levels, including levels of petroleum-derived compounds 

from spills (aromatic hydrocarbons in particular) 

(5) Air quality

• Dust levels 

• Levels of by-products of OHV emissions (including polycyclic aromatic 

hydrocarbons, carbon monoxide, nitrogen oxides, ozone, and sulfur 

dioxide) 

(6) Socioeconomics (direct and indirect) 

• Recreator satisfaction with their recreation (or other) experiences 

• Compliance with OHV (or other) regulations 

• Knowledge regarding effects of user activities on various aspects of land 

health 

42 
• Mapping the distribution and intensity of OHV versus non-motorized 

recreation and other land uses, 

• Patterns of regulation compliance (as evidenced by creation of 

unauthorized trails, damage to vegetation, and so on) 

• Trends in local economic indicators associated with OHV and nonmotorized recreation and other land uses (for example, sales in camping 

equipment, gasoline, restaurants, lodging facilities) 

Specific research questions and management goals—as well as sensitivity to OHV effects 

and the availability of funding and personnel—will determine the potential efficacy of using any 

one indicator to evaluate or monitor OHV effects on BLM lands. Qualitative indicators may be 

most useful for rapid assessments, whereas quantitative indicators may be needed for long-term 

monitoring. Ultimately, however, implementing an OHV effects monitoring program will require 

consultation with topical experts and additional research to identify or develop appropriate and 

efficient indicators and field methods for evaluating and monitoring OHV effects (personal 

communication from D.A. Pyke to Z.H. Bowen, U.S. Geological Survey, Fort Collins, Colorado, 

August 2007). Work on developing such indicators is currently underway by rangeland ecologist, 

D.A. Pyke, U.S. Geological Survey in Corvallis, Oregon. 

3.2 BLM’s Indicators of Land Health Compared to Indicators of OHV Effects 

Described in the Literature 

In terms of the specific land health attributes assessed, there is some limited 

correspondence between several indicators of OHV effects described in the literature and some 

of BLM’s 17 qualitative assessment indicators (see Pellant and others, 2005). The area of 

greatest overlap is that of soil health and watershed condition; there is somewhat less overlap in 

the area of vegetation health (table 3.1). Attributes addressed in the literature but not by BLM’s 

17 indicators include wildlife population and habitat health, water and air quality, and 

socioeconomics. Even indicators that measure the same or similar attributes, however, may differ 

notably with respect to the scale and scope to which they are or can be applied, or the precision 

and accuracy they can provide. 

The differences between BLM’s indicators and those described in the literature do not 

imply that BLM’s indicators are inappropriate for assessing some attributes under some 

conditions. Rather, they underscore the need for a variety of indicators to meet equally variable 

needs. For example, qualitative indicators (such as those employed by the BLM) often entail 

making visual estimates, which may be suitable for rapid assessments by time-limited personnel 

operating with small budgets; qualitative measurements, however, are subject to observer bias. 

Research and monitoring studies, on the other hand, generally require quantitative indicators (or 

strict decision rules to guide data collection for qualitative parameters) that minimize observer 

bias and maximize statistical precision and accuracy to ensure defensible results and the 

detection of trends; quantitative measurements, however, can drive up the cost and time 

requirements of research and monitoring efforts. Therefore, the choice of indicators employed 

will depend on the specific goals, budgets, sites, and other factors. In some cases, BLM’s 

indicators may be suitable; other cases may require more quantitative indicators. Co-opting 

indicators from other disciplines also may be extremely useful for revealing OHV effects on land 

health. 

43 
Table 3.1. Indicators emphasized in the literature reviewed for effects of off-highway vehicles 

(OHV) on land health compared to indicators of land health employed by the U.S. Bureau of Land 

Management (BLM) (Pellant and others, 2005). 

Land health 

category Indicators of OHV effects described in reviewed literature 

BLM 

indicatorsa

Soil strength 9,11* 

Soil bulk density 11 

Soil permeability 8,9*,11* 

Water infiltration rate 1,2,3,4,5,8*,9*, 

10*,11* 

Erosion rate 1,2,3,4,5,6,7, 

8*,10* 

Sedimentation rate 

Soils and 

watersheds 

Presence/condition of biotic and abiotic soil crusts 2,4,6,7,8* 

Plant species diversity 12*,13,16* 

Ratio of native plants to non-native and/or invasive plants 12,16 

Percent plant cover 4,13,14 

Plant size 11,13,14, 

15*,17 

Vegetation 

Plant growth rate 11*,13,14,15*,

17 

Habitat patch size and connectivity (can be expressed as ratio of road 

edge:habitat area or as native:non-native habitat) 

4,12*,16* 

Shape/scope of animal movements relative to roads 

Wildlife diversity and/or species abundance 

Ratio of native, endemic wildlife to non-native and/or invasive species 

Population size and trend 

Gender/age ratio trend 

Productivity trend 

Average body mass for a given age/gender 

Average survivorship 

Wildlife and 

habitats 

Vehicle-caused mortality rate 

Sedimentation rate or depth 

Amount of suspended solids 

Turbidity level 

Level of atmospheric deposition associated with OHV emissions Water quality 

Level of petroleum or its by-products (benzene, ethylbenzene, toluene, 

xylenes, 1,3-butadiene, lead) 

Levels of OHV emission by-products (nitrogen oxides, carbon monoxide, 

sulfur dioxide, ozone, aldehyde, PAHsb

) 

Level of suspended particulates Air quality 

Plant-absorbed level of emissions by-products a 1 = Number and extent of rills. 

2 = Presence of water flow patterns. 

3 = Number and height of erosional pedestals or terracettes. 

44 
4 = Bare ground (excluding rock, litter, lichen, moss, plant canopy). 

5 = Number of gullies and erosion associated with gullies. 

6 = Extent of wind scoured blowouts and/or depositional areas. 

7 = Amount of litter movement (description of size and distance expected to travel). 

8 = Average soil surface (top few mm) resistance to erosion. 

9 = Soil surface structure and content of soil organic matter (to include type of structure and A-horizon color and 

thickness). 

10 = Effect of plant community composition (relative proportion of different functional groups) and spatial 

distribution on infiltration and runoff. 

11 = Presence and thickness of compaction layer (usually none). 

12 = Functional/structural groups (in descending order of dominance by above-ground production or live foliar 

cover). 

13 = Amount of plant mortality and decadence (include which functional groups are expected to show mortality or 

decadence). 

14 = Average percent and depth of litter cover. 

15 = Expected annual production (this it total above-ground production, not just forage production). 

16 = Potential invasive (including noxious) species (native and non-native). 

17 = Perennial plant reproductive capability. b

Polycyclic aromatic hydrocarbons. 

Ultimately, any indicator used to evaluate or monitor OHV effects will need a

standard value (or range of values) that represents the baseline condition or a threshold 

value above (or below) which management is triggered. Ecosystem properties, however, can 

vary widely across (and within) spatial scales. Therefore, selecting an appropriate standard or 

threshold for any one indicator necessitates an evaluation of the spatial scale(s) at which the 

associated effect occurs or is likely to affect ecosystem function. For example, OHV-caused 

sedimentation in a first-order stream might have significant by very localized effects on that 

stream, but no significant effects downstream; in contrast, OHV-caused sedimentation in a firstorder stream might not have significant effects on that stream, but sedimentation in multiple 

first-order streams may result in significant cumulative downstream effects in second- and thirdorder streams. Similarly, the temporal scale at which ecosystems respond to land uses can vary 

from short-term (hours) to long-term (decades or longer); thus, it is important to consider 

temporal scale(s) as indicator standards or thresholds are established. For example, wildlife 

behaviors may exhibit immediate responses to OHV traffic by moving away from OHV routes; 

population trends, however, may take several generations to show effects of OHV disturbance, in 

which case the time required to detect trends will depend on how long it takes for generations 

turn over. Where OHV effects are not an immediate concern, one could incorporate long-term, 

annual, qualitative assessments of OHV-use areas, but where effects are of immediate concern, 

short-term, quantitative assessments may be implemented. 

Standards for a given land health indicator can be developed by ascertaining baseline 

values at control sites under a given set of conditions. Once the baseline values are established, it 

becomes important to standardize the conditions under which subsequent measurements of that 

indicator are made. For example, the freezing and thawing of soils tend to decompact soils, and 

precipitation tends to alter other soil properties; thus, it would be important to monitor soils at 

similar times of year and under similar soil-moisture conditions. 

45 
3.3 Some Potential Indicators for Evaluating and Monitoring OHV Effects 

3.3.1 Potential Indicators of OHV Effects on Soils and Watersheds 

A major effect of OHV traffic on soil health is compaction—the reduction of a soil’s 

porosity. Potentially useful indicators for monitoring soil compaction include soil strength, soil 

bulk density, and infiltration rate (or permeability). Soil strength is typically measured in terms 

of the soil surface’s resistance to a vertical force exerted by a penetrometer and is expressed as 

kg/cm2

 (see http://cropsoil.psu.edu/extension/facts/agfacts63.cfm for explanations and diagrams 

of this method). Soil bulk density is measured as the ratio of dry solid mass (after soil is overdried) to bulk volume of soil and is expressed as g/cm3

 (or Mg/m3). Infiltration or permeability

is the rate at which the water infiltrates the soil and is expressed as cm/hr. Infiltration tests can be 

conducted in the field with relatively simple equipment (for a demonstration, see 

http://www.grow.arizona.edu/Grow--GrowResources.php?ResourceId=181); however, many 

replicates are needed to obtain adequate comparisons, and it takes time for infiltration to occur.

Additional resources on the utility of devices and techniques for monitoring soil health include 

Leung and Meyer (2003) for soil compaction; O'Sullivan and Ball (1982), Hooks and Jansen 

(1986), Komatsu and others (1988), and Keener and others (1991) for soil strength; and Flint and 

Childs (1984), Isensee and Luth (1992), Miller and others (2001), and Lowery and Morrison 

(2002) for soil bulk density. McBrayer and others (1997) and Amezketa Lizarraga and others 

(2002) describe techniques used to measure infiltration rates. Overall, soil strength and bulk 

density are the most commonly used indicators of soil compaction in visitor impact studies 

(Liddle, 1997). 

Soil strength, which increases with increasing soil compaction, depends on a number of 

inherent variables, such as particle size, type of clay mineral, the size/distribution of pores, and 

aggregate stability. For example, Adams and others (1982) found that soil strength in 

undisturbed areas of the Mojave Desert ranged between 5.1 kg/cm2 at 6 percent water content 

and 21.1 kg/cm2

 at 1.8 percent water content, indicating that soil strength decreases with 

increasing moisture content. In general, a soil strength of less than 20 kg/cm2 (284.4 lb/in2) was 

indicative of undisturbed terrain, whereas trails intensely used by motorcycles had soil strengths 

(during wet conditions) that typically ranged from 20 to 60 kg/cm2 (284.4 to 853.2 lb/in2) 

(Adams and others, 1982). When soil strengths exceeded 20 kg/cm2

 (284.4 lb/in2; measured at 

about field capacity) due to compaction, Grimes and others (1975, 1978) found that root 

extension of certain plants, including alfalfa (Medicago sativa), corn (Zea mays), and cotton 

(Gossypium hirsutum), was limited. 

Soil bulk density also increases with increasing soil compaction. For example, in the 

Mojave Desert, Webb (2002) and Caldwell and others (2006) found that bulk densities of 

undisturbed surface soils ranged from 1.40 to 1.68 g/cm3; however, bulk density increased 

significantly to 1.80 g/cm3

 at high-disturbance sites (Caldwell and others, 2006). Measuring soil 

bulk density, however, is time-consuming and difficult in gravelly soils (Webb, 2002), which are 

typical of many desert sites. Thus, its practicality may vary not only from region to region, but 

from soil to soil within a region. Infiltration, on the other hand, decreases with increasing soil 

compaction. In undisturbed desert habitats, Eckert and others (1979) found soil infiltration rates 

to be 3.2 cm/hr. In the same study, infiltration rates were 15 percent lower where motorcycle (2.7 

cm/hr) and 33 percent where truck (2.1 cm/hr) traffic had occurred. 

For each of the indicators identified above, it will be crucial to consider soil type and 

water content when setting standards, as these factors clearly influence overall inherent values of 

46 
each parameter. It also is clear that variability in soil type may preclude using a single 

indicator—much less one standard—for monitoring soil health across all sites. Overall, 

monitoring soil health would entail measuring soil properties in tracked versus untracked areas 

of similar soil type and under similar conditions of soil water content. For areas previously 

unaffected by OHV activities but proposed to become OHV areas, managers may wish to collect 

predisturbance data on soil properties to serve as a baseline from which trends in soil properties 

may be assessed over time. An acceptable percent change in soil properties could be selected, 

and if soil properties were to exceed these threshold values then management actions could be 

implemented to bring the soil properties back to acceptable values. 

A possible method of monitoring surface changes in watersheds might be to establish 

permanent monitoring sites for repeat photography studies. By standing in the same spot, 

orienting the camera in the same direction, and using the same focal length for each site visit, 

sequential photographs would provide a qualitative, relatively easy means of monitoring surface 

changes due to erosion and OHV tire cuts. Helpful websites that discuss repeat photography 

(both terrestrial and aerial) include http://biology.usgs.gov/luhna/chap9.html, 

http://wwwpaztcn.wr.usgs.gov/wyoming/rpt_ground.html, and 

http://www.cpluhna.nau.edu/Tools/repeatphotog.htm. Scientists with the National Science and 

Technology Center are using close-range (terrestrial or ground-based) photogrammetry 

techniques and associated tools for producing and interpreting close-range images (less than 300 

m, as opposed to aerial photogrammetry distances of more than 300 m) that may be used to 

document soil crusts, soil erosion, vegetation, and other resources (see 

http://www.blm.gov/nstc/prodserv/ST134/pdf/Handout3CloseRange.pdf). 

3.3.2 Potential Indicators of OHV Effects on Vegetation 

Some plant responses to OHV activities are preceded by, and result from, OHV effects on 

soil properties. In other words, soil characteristics, particularly soil compaction, play important 

roles in the distribution, abundance, growth rate, reproduction, and size of plants. Furthermore, 

some plant responses are likely to lag behind changes in soil properties, and, by the time effects 

are detected in plants, site recovery could be more difficult and/or lengthy. As such, it would be 

important to implement management strategies for maintaining or improving soil condition 

before plants are affected and no longer provide enough cover to hold soils in place during 

restoration efforts. Several vegetation parameters, however, have potential value as direct 

indicators of OHV effects on plant communities. 

As mentioned in section 3.3.1, soil compaction results in reduced water infiltration. As a 

result, overall plant productivity, as measured by percent plant cover, abundance or stem 

density, growth rate, biomass, plant height and width, ratio of large:small species, and/or 

reproductive output may be diminished (Johnson and others, 1975; Vasek and others, 1975; 

Adams and others, 1982; Webb, 1983; Prose and others, 1987; Holzapfel and Schmidt, 1990; 

Lightfoot and Whitford, 1991; Brooks, 1995; Bolling and Walker, 2000). It is important to 

consider, however, the differential growth habits and responses of plant species to conditions 

generated by OHV activities; they may be favored or inhibited by OHV effects (Holzapfel and 

Schmidt, 1990; Angold, 1997). For example, the productivity of some species may increase due 

to abnormal conditions of moisture availability from runoff near compacted areas and/or where 

water roadbed materials allow increased infiltration rates (Johnson and others, 1975; Vasek and 

others, 1975; Holzapfel and Schmidt, 1990; Lightfoot and Whitford, 1991). 

To evaluate and monitor plant productivity, researchers often use transect-intercept 

methods for measuring larger- or site-scale indicators, such as percent cover, and quadrat-based 

47 
sub-sampling at random locations along transects for measuring smaller-scale (individual plants) 

indicators, such as plant size or growth rate. Repeat photography is also potentially useful for 

monitoring vegetation cover when personnel budgets are limiting, although ground-based repeat 

photography methods may be more realistic than satellite imaging in terms of staff expertise and 

funding required (see methods and URLs provided in Section 3.3.1). Satellite imagery, however, 

can be very effective for ascertaining landscape-scale changes in vegetation cover during longterm studies at selected study sites (Johansen and others, 2007). 

Plant community composition or diversity—a parameter that factors relative 

proportions of each species into species richness—is a commonly used indicator health of a 

vegetation community (Davidson and Fox, 1974; Adams and others, 1982; Prose and others, 

1987; Wilcox, 1989; Tyser and Worley, 1992; Lovich and Bainbridge, 1999; Parendes and 

Jones, 2000). For example, a plant community comprising 5 individuals each of 10 species and 

150 individuals of another (200 total individuals) would be considered depauperate compared to 

a community comprising 20 individuals each of 10 species (200 total). Native species diversity is 

further compromised when non-native and/or invasive plants dominate the plant community 

(Holzapfel and Schmidt, 1990). OHVs caked with mud acquired elsewhere potentially introduce 

or disperse seeds of non-native and invasive species; thus, OHV-route margins often become 

populated with exotics and invasives that eventually may spread and outcompete native species 

at the landscape level. Therefore, an important consideration when evaluating plant species 

diversity is the presence of non-native and/or invasive species. In other words, although species 

diversity can be useful for evaluating and monitoring the impacts of OHV activities on 

vegetation, the ratio of native to non-native and invasive plant species must be taken into 

account. Monitoring transects oriented perpendicular to OHV travel routes would help identify 

range expansions beyond the linear routes. 

Similar to the precautions issued above for selecting standards of soil health, vegetation 

characteristics also vary widely according to soil type, slope, aspect, microclimate, and other 

factors. Ultimately, having baseline data before a site is disturbed, and/or having nearby 

reference sites not subjected to OHV activity would help differentiate between site-based 

variations and OHV impacts on vegetation. 

3.3.3 Potential Indicators of OHV Effects on Wildlife and Habitats: Native, Threatened, and 

Endangered Species 

The physical imprint of a road or OHV route creates barrier effects that may effectively 

alter habitat patch size and connectivity, which potentially alters or inhibits animal 

movements (Oxley and others, 1974; Mader, 1984; Swihart and Slade, 1984; Samways, 1989; 

Andrews, 1990; Baur and Baur, 1990; Forman and Alexander, 1998; Jackson and Griffen, 1998). 

Roads and trails also create edges that can alter wildlife habitat use and movements (Nicholson, 

1987; Yahner, 1988; Reed and others, 1996; von Seckendorff Hoff and Marlow, 1997; Gibbs, 

1998; Vos and Chardon, 1998), and in many instances these edge effects extend well beyond the 

road’s actual footprint into habitat interiors. Unfortunately, both direct and indirect indicators of 

animal movements and habitat or home-range use can be difficult to measure, simply because 

populations are mobile and easily affected by many factors besides OHV activity if care is not 

taken to avoid, or control for, these additional effects. Furthermore, adequate sample sizes and 

accurate measurements of animal movements generally require capture-mark-release or capturemark-resight studies, which can be costly in terms of funding for equipment and personnel time. 

Therefore, evaluating and monitoring movement responses of suitable indicator species or 

48 
functional groups to OHV activities and routes might be more efficient than trying to monitor 

many species. For example, species least likely to cross OHV routes or networks of routes 

(beetles or small mammals, for example) would be more suitable for studying barrier effects of 

OHV routes than species inhibited from crossing only multi-lane, paved highways (large 

ungulates). Ultimately, animal movement studies might be most appropriate in comprehensive, 

long-term research projects at selected study sites representative of locations and habitats being 

impacted most by OHV activities. An appropriate measure of edge effects on wildlife may entail 

studies of spatial distribution relative to distance from OHV routes, as well as density and other 

population dynamics among target indicator species that require habitat interiors. 

Traffic intensity and noise level of OHVs may be useful indirect measures of OHV 

effects on wildlife behavior and survivorship. If measured, temporal variation in animal activity 

or presence would need to be considered, as diurnal animals may be more affected by OHV 

traffic and noise than nocturnal animals if most OHV activity occurs during daylight hours 

(Ouren and Watts, 2005). Vehicle speed also may be an important parameter to measure, as it 

can affect mortality rates of animals as they attempt to navigate landscapes where OHV travel is 

significant. There are technologies available for field monitoring of noise levels and traffic 

volume and speed (see examples on the Internet at 

http://www.jhuapl.edu/ott/technologies/technology/articles/P01254.asp and 

http://www.noisemeters.com/accessories/outdoorkits.asp), although again it would be more costeffective to use them in selected study sites for targeted research questions as opposed to broadscale monitoring programs. 

Ideally, any program for monitoring OHV effects on wildlife would include assessments 

of whether/how wildlife responds to OHV-related factors. If population dynamics were 

understood before the onset of OHV activities, then monitoring any changes that occur afterward 

could be straightforward if other conditions are held relatively constant. Climate, however, 

typically makes long-term monitoring of animal population dynamics very complex, and wideranging animals may be more difficult to monitor than those with smaller or more restricted 

movements. Similar to the dynamic ways in which wildlife populations use a given area, OHV 

use in a given area is also dynamic; if the area affected and the intensity of disturbance enlarges 

considerably, wildlife may respond as well. These and other factors typically drive up the 

funding and staffing needs associated with collecting population dynamics data. Thus, to 

determine thresholds of OHV activity potentially tolerated by wildlife, it may be more realistic to 

measure long-term changes relative to gradients and changes in OHV activity. Again, careful 

selection of suitable indicator species, or functional groups, may help increase the effectiveness 

of monitoring wildlife populations (Lindenmayer, 2000; Noon, 2003, p. 51-55). 

To date, there have been few simultaneous studies of OHV use and wildlife responses to 

OHV activities, but such studies could provide more precise assessments of the relationship 

between patterns of OHV activity and wildlife responses, particularly behavioral responses to 

varying traffic patterns, intensity, and total area affected. GPS and satellite technologies could be 

employed to build Geographic Information System (GIS) data layers of OHV-associated 

variables, both static (for example, road width) and dynamic (vehicle speed and traffic volume). 

When overlaid with GPS-based telemetry data layers that map animal movements, one could 

relate changes in static and dynamic OHV variables to wildlife responses, making these 

particularly powerful tools for long-term studies aimed at evaluating OHV impacts on wildlife. 

49 
3.3.4 Potential Indicators of OHV Effects on Water Quality 

The literature on OHV impacts offered little information specific to evaluating or 

monitoring OHV effects on water or air quality. Based on studies of water quality in other 

disciplines, however, potentially useful indicators highly relevant to OHV effects would be 

sedimentation and turbidity. Sedimentation can be measured in terms of deposition rate or total 

amount of solids deposited where surface and directed flows enter aquatic systems downslope of 

OHV-use areas. A useful reference on different methods for measuring sedimentation may be 

found in Lisle and Eads (1991). Turbidity, which indicates the level of suspended solids in 

water, can be measured easily in the field with a Secchi disk (see 

http://www.noble.org/Ag/Wildlife/SecchiDisk/Index.htm). With respect to monitoring levels of 

contaminants in water from OHV emissions and fuel or other chemical spills, water samples can 

be collected and analyzed in laboratory settings; however, this can be costly, and would probably 

be more suitable for selected, long-term research sites than in broad-scale monitoring programs. 

Potentially important contaminants to test for in OHV-impacted watersheds could include 

benzene; ethylbenzene; m-, p-, and o-xylene; toluene; 1,3-butadiene; and lead (Forman and 

others, 2003: p. 205-213; Arnold and Koel, 2006). In addition, nitrogen deposition from nitrogen 

oxides can affect water quality if nitrogen loading alters the chemical balance of nutrients in 

aquatic organisms. 

Although it has already been stated that, in general, it is important to compare OHVimpacted sites with similar reference (unaffected) sites when evaluating OHV effects, an 

additional consideration with respect to water quality is to make comparisons within the same 

drainage. This is because water quality variables can change depending on the geology, adjacent 

habitat, and hydrology of the area. Thus, an appropriate technique for assessing OHV effects on 

aquatic systems might be to compare water quality at replicate sites both upstream and 

downstream of where OHV activities are occurring. 

3.3.5 Potential Indicators of OHV Effects on Air Quality 

There are several measures of air quality that can be used to assess effects of OHVs, 

including levels of fugitive dust (suspended particulates) and/or OHV emissions (including 

carbon monoxide, ozone, sulfur dioxide, aldehyde, and polycyclic aromatic hydrocarbons). 

Due to the effects of humidity, precipitation, fallout rates of different particle sizes, and wind 

speed and direction, however, measuring dust levels specific to any one site or set of OHV 

activities can be difficult. A useful technique for assessing the amount of dust associated with 

OHV use is to collect PM10 (particulate matter less than 10 microns in diameter, which can pass 

through the nose and throat and get deep into the lungs) data, as dust is a common component of 

PM10. Technological advancements continue to provide additional devices useful for monitoring 

dust and other suspended particulates (Sanders and Addo, 2000)—including satellite imagery 

(Nakata and others, 1976; Gill, 1996; Stefanov and others, 2001)—although cost becomes a 

greater factor with increasing sophistication of instruments used. Fox (1986) provides a list of 

appropriate procedures for measuring and evaluating various air-quality parameters, and the 

Environmental Protection Agency’s National Ambient Air Quality Standards include primary 

standards (those designed to protect overall public health and the health of “sensitive 

populations”) for carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone, and sulfur 

oxide levels (see http://www.epa.gov/air/criteria.html). 

50 
3.3.6 Potential Indicators for OHV Effects on Socioeconomics 

Resource planning has been known to take recreation and economic values of OHV use 

into greater consideration than biological considerations (Adams and Dove, 1989). Human 

behaviors, attitudes, and economics, however, are the ultimate drivers of OHV impacts on 

natural resources (Decker and others, 1996; Vaske and others, 2001); thus, understanding the 

socioeconomics of OHV use is crucial to the success of any program designed to address OHV 

effects, whether they impact natural resources or land users. This includes understanding the 

economic effects—both benefits and costs—of OHV management and use on OHV users, other 

land users, local businesses, land-management agencies, and ecosystem services. 

Bight and others (2003) provide a framework and guidelines for conducting social 

assessments and identifying/organizing social science data, including measurable indicators (see 

Chapter 3, p. 21) for use in natural resource planning. Indicators suitable for monitoring the 

socioeconomic implications of OHV use (human behaviors, attitudes, and economics) may be 

identified through stakeholder interviews, focus groups, and surveys (mail or telephone); 

economic assessments; and developing maps depicting areas used for different forms and 

intensities of recreation (Massachusetts Department of Environmental Management, 1995; 

Decker and others, 1996; Stokowski and LaPointe, 2000; Nelson and Lynch, 2001; Dillman, 

2007). For example, interviews can be designed to elucidate not only OHV impacts on all types 

of user experiences, but also ways in which those impacts might be mitigated. Trail openings or 

closures may affect levels of OHV user demand and satisfaction, which could be identified 

through well-designed survey questions that target OHV users (see Dillman 2007). 

Likewise, understanding the effects of OHV site development and regulation compliance 

first requires monitoring where OHV users like to go and what their preferences are when riding. 

For example, Nelson and Lynch (2001) conducted a study to determine the effectiveness of OHV 

areas, the approaches for which included a survey of licensed OHV riders, interviews with key 

stakeholders about project management, and an assessment of the signs established to identify 

designated OHV trails. Monitored over time, these indicators could be used as guidelines for 

adaptive management. Finally, identifying the economic impacts associated with OHV activities 

and regulations potentially affecting nearby communities may entail economic analyses of 

businesses and services that cater to outdoor recreators (including OHV users and non-motorized 

recreators; English and others, 2001). Economic assessments also may be used to determine the 

financial effects associated with losing ecosystem services, regulation enforcement, resource 

restoration, and other potential costs of OHV use. 

A potentially powerful tool for identifying socioeconomic effects of OHV use would be 

GIS applications (Massachusetts Department of Environmental Management, 1995; Stokowski 

and LaPointe, 2000; Kopperoinen and others, 2004). For example, areas considered by recreators 

as being most important for excluding motorized forms of recreation could be identified by users 

on a map and then used to develop time-series GIS data layers that illustrate long-term changes 

in preferences pertaining to land-management actions or other factors. Overlaid with maps that 

identify areas ecologically most suitable for OHV use, managers also could determine which 

areas are most likely to be resilient to OHV use and provide OHV user satisfaction. 

51 
4.0 Mitigation and Site-Restoration Techniques 

4.1 Summary 

Mitigation of OHV effects and restoration of OHV-impacted sites requires a range of 

approaches and techniques. Social science in particular has strong applicability for ameliorating 

the effects of OHV activities, not only in terms of their impacts on non-motorized recreators and 

other OHV users, but also in terms of their effects on natural resources, as ultimately human 

behavior is what drives OHV use and related behaviors. Important tools for managing OHV use, 

therefore, include not only interviews, surveys, and focus groups, but also strong educational 

campaigns. Once impacted by OHV use, however, ecosystems may need to be closed and rested, 

if not restored. Sites with severely compacted soils and/or bedrock exposures due to erosion may 

need restoration through importation of native soils, scarification, decompaction, stabilization, 

inoculation with microbes and mycorrhizae, and/or mulching before reseeding and/or planting 

can be done. 

4.2 Mitigation and Site-Restoration Techniques 

The OHV literature has addressed many effects of both motorized and non-motorized 

recreation on components of ecosystem health (Cole, 2004; Stokowski and LaPointe, 2000; Cline 

and others, 2007), including soils, vegetation and habitat, wildlife behavior and population 

dynamics, and the quality of water and air. Resource degradation and wildlife disturbance are not 

uniform, however. Factors influencing the extent and degree of impact include user types and 

behaviors, the environment’s resistance and resilience, and the timing, intensity, and distribution 

of use (Cole, 2004). Therefore, management and mitigation planning and implementation must 

take these factors into consideration. 

4.2.1 Understanding Land User Preferences and Conflicts 

Although addressing ecosystem degradation and user conflicts stemming from OHV use 

generally requires policy and management considerations (Vancini, 1989), there is the likelihood 

that one group or another will be dissatisfied with the outcome of any one management decision. 

Therefore, it is important to promote acceptance of, if not support for, management decisions 

prior to implementation, because those not accepted are likely to fail in the long run, regardless 

of how sound the reasoning is behind them (Shindler and others, 2004). One way to potentially 

improve policy acceptability is to identify, assess, and include all users who may be affected by 

management decisions and include them in the decision-making process; useful tools for 

accomplishing this goal include stakeholder and demographic analyses, and arranging 

stakeholder focus groups (Decker and others, 1996; National Oceanic and Atmospheric 

Administration, 2005). Basic discussions, such as defining different interpretations of OHV use 

or seeking consensus on the meaning of OHV use to disparate users, can potentially preclude 

feelings of marginalization by any given group that could lead to conflict between users and/or 

between users and managers (Stokowski and LaPointe, 2000). 

A baseline understanding of OHV users (including recreators, livestock operators, and 

energy-development operators) can further help to alleviate conflicts among different users. If 

users can be classified, even broadly, managers can maximize their efforts by using that 

information to form relevant management plans and/or communication and education 

campaigns. For example, understanding the problems that users have with each other, as well as 

their motivations for recreating, can yield more effective management that placates most, if not 

52 
all stakeholder groups, and does not lead to marginalization or displacement of any one group. 

Often, outdoor recreators of all types have fairly similar goals and reasons for participating in 

outdoor recreation (Schuett and Ostergren, 2003), including a need to “get away” from the 

pressures and commotion of everyday life, rejuvenation, and enjoyment of the natural 

environment. Even when the mechanisms by which those needs are met are not homogeneous 

among user groups, knowledge of stakeholder preferences can help to improve the management 

of OHV recreation on public lands. 

Managing the social effects of OHV activities and promoting compliance with 

regulations also require determining where OHV users like to go and what their preferences are 

when riding (Nelson and Lynch, 2001). Likewise, management must consider the levels of 

environmental dominance and technology associated with different forms of land use. Once 

again, GIS data layers could be developed to identify spatial management needs and predict 

where conflicts may occur. For instance, nature study, an activity characterized by “low 

dependence on technology and low dominance over the environment,” and OHV touring, which 

is characterized by “high dependence on technology and high levels of environmental 

dominance,” need to be segregated spatially to help prevent user conflicts. If it is found on a map 

grid that two such activities are taking place in adjacent quadrats, there is a high likelihood that 

recreators who participate in these activities will come into conflict (Bury and others, 1983). 

Maps of sites suitable for a given activity could be overlaid with user preferences for certain 

locations or landscape features to further fine-tune planning and mitigation of user conflicts. 

Finally, if recreators are made aware of their impacts and understand the implications of 

those impacts, they may be more willing to take steps that lessen those effects, thereby 

diminishing the necessary level of managerial monitoring (Vancini, 1989; Anderson and others, 

1998). Communication and education campaigns can be difficult, however, due in part to (1) 

modern-day information overload, increasing the likelihood that recreators will disregard 

information pertaining to natural resources and recreation, and (2) the fact that managers and 

designers of education campaigns rarely have a formal knowledge and understanding of 

persuasion techniques (Absher and Bright, 2004). Assuming that these factors can be surmounted 

by well-designed educational resources and manager training, education is a crucial first step in 

alleviating negative perceptions of trail closures and other regulations or management actions. 

For example, management agencies need to explain the reasons and rationale for closures so that 

they do not appear arbitrary (Crimmins, 1999). Such educational campaigns may be more 

successful if they target the many OHV users participating in some other form of outdoor 

recreation that depends on a healthy ecosystem. Hunting and fishing are two such forms of 

recreation, and if an OHV area is closed seasonally to protect elk during calving season or fish 

during spawning season, communicating this to OHV users is likely to elicit more compliance 

with the closures. When OHV users understand that their hunting and fishing activities may be at 

stake, they are more likely to respect closures. In closed areas already subjected to high levels of 

illegal riding, education would be crucial for communicating to users the reasons for the closures 

and related management actions. 

4.2.2 Mitigating OHV Use Effects 

Lands managed by BLM are placed into one of three broad types pertaining to OHV-use 

designation: “open,” “limited,” or “closed.” Within the “limited” category there can be several 

types of limitations: OHVs can be “limited to existing routes,” “limited to designated routes,” or 

“limited seasonally” (see 

http://www.blm.gov/nhp/news/releases/pages/2000/pr000110_ohv_qa.html). Indeed, trail/area 

53 
closures are among the management options available for allowing soils and vegetation to 

recover from OHV effects or to help preclude localized impacts on air and water quality. 

However, in areas where OHV effects would be notable with the first few uses and/or generate 

significant, long-lasting impacts, it would be prudent to consider whether such places are 

appropriate for OHV use in the first place (Cole and Landres, 1995; Cole, 2004). A well-placed, 

concentrated system of trails could alleviate the difficulties of enforcement that extend across a 

large territory (Major, 1987). Spatial models, including GIS data layers, developed for 

identifying areas most suitable for resisting or recovering rapidly from OHV impacts, or those 

most suited for concentrated and/or self-monitored OHV use, would be effective tools for 

establishing OHV sites in appropriate areas and avoiding the need for frequent, long-term 

closures, expensive restoration actions, and/or the high cost or enforcement monitoring. For 

example, erosion, sedimentation, and rill or gully formation are much more likely to occur in, 

and downslope of, OHV-use areas located on or at the top of a slope than in/from a flat site or 

depressional area lacking watershed outlets. The GIS data layers could, therefore, identify areas 

to exclude from development for OHV use. 

Although trail/area closures may be among the easiest management actions to implement, 

they may prove difficult to enforce, particularly under a policy of “closed unless posted open.” 

The enforcement difficulty will depend on the number of trails involved, their locations relative 

to one another, and the number of enforcement personnel available. In the absence of funding for 

adequately monitoring regulation compliance, educating the public about the effects of their 

recreational pursuits may prove more economical and yield self-monitored trail users. In areas 

affected heavily by recreational activities, however, visitor management may be required (Jim, 

1989). “Rationing” is a visitor management strategy that can be used to control the number of 

visitors over a given area where the available recreational resources are finite and/or unique. If 

the number of visitors is restricted, their quality of experience may be greater; a drawback of this 

approach is that the benefit is realized by fewer users (see Dimara and Skuras, 1998). Other 

strategies may include reserving a permit in advance, a permit lottery system, or implementing 

user fees that reflect the quality of experience (for example, it may cost more to use a high-use 

area that offers a high-quality experience than a low-use area that offers a low-quality 

experience). In many cases, these strategies could help alleviate pressures on law enforcement. 

Wildlife is affected by OHV recreation in numerous ways, including displacement caused 

by human disturbance or direct mortality caused by vehicle-animal collisions (Cole and Landres, 

1995; Knight and Cole, 1995; Miller, 1998; Stokowski and LaPointe, 2000; Cline and others, 

2007). As OHV-related landscape fragmentation increases, habitat area and required 

juxtapositions of habitat types that meet the different needs of a given species, as well as 

adequate cover from disturbance, are diminished. Because the resulting effects may be 

detrimental to individuals and/or local populations (Knight and Cole, 1995), mitigation and 

management may be required to protect wildlife. One approach for mitigating the effects of 

wildlife displacement and disturbance may be to control the spatial and/or temporal proximity of 

OHV activities to wildlife, especially during critical nesting and breeding times (Gutzwiller, 

1995). Again, GIS data layers could be very useful for identifying crucial wildlife areas and 

ensuring that they are not overlapped, fragmented, or otherwise disturbed by OHV-use areas. 

4.2.3 Restoration of OHV-Impacted Areas 

Revegetation of natural communities in arid environments is particularly difficult 

(Wallace and others, 1980) and studies evaluating revegetation have shown varying degrees of 

success (Graves and others, 1975, 1978; Kay and Graves, 1983; Grantz and others, 1998); thus, 

54 
restoration of sites significantly degraded by OHV activity may be needed before sufficient 

levels of revegetation can take place, particularly if underlying bedrock has become exposed. 

Webb and others (1978) recommend that soil be imported and stabilized to replace the displaced 

soil where bedrock has become exposed. Generally, restoring soil horizons for re-establishing 

microbial communities can be achieved by inoculating soils with native microbes and 

mycorrhizae (Belnap, 1993; Bolling and Walker, 2000). Bolling and Walker (2000) suggest that 

decompacting OHV tracks and flattening out the lateral and center berms associated with them 

may increase the probability of community redevelopment with a more natural surface shape. 

Recovery of cryptobiotic soils, however, is more complex and may require long periods of time 

(Wilshire, 1983b; Lovich and Bainbridge, 1999); ultimately, their recovery rate will depend on 

the degree of soil compaction and the nature and intensity of the initial disturbance (Bolling and 

Walker, 2000). 

To reduce the potential for erosion at restoration sites, it is important to use mulch, 

stabilization techniques, and/or establish vegetation. Rasor (1976, cited in Webb and others, 

1978) suggests that ground cover (such as wire netting) be applied across the restoration site to 

stabilize soils. Kay and Graves (1983) recommend that seeding with local seed stock begin as the 

disturbance desists. Revegetation techniques also may include container planting (Grantz and 

others, 1998), hand seeding (Lovich and Bainbridge, 1999), drill seeding (Kay, 1988), and 

establishment of visually dominant species, such as creosote bush (Larrea tridentata; Kay and 

Graves, 1983). 

5.0 Monitoring and Research Needs 

5.1 Summary 

More information is needed to help support policy making and land management as they 

pertain to the natural resources and people affected by OHV policies and management. Research 

needed to help support policy makers and land mangers includes (but is not limited to) 

• well-designed studies that incorporate planned comparisons of treatment (OHVimpacted) and control (unimpacted/reference) sites, as well as “before and after 

OHV-impact” studies; 

• studies at various spatial and temporal scales across all impacted habitat types; 

• studies on habitat fragmentation and road-edge effects caused by OHV activities; 

• studies on effects of various gradients in OHV disturbance and at varying 

distances from OHV routes; 

• studies of OHV effects on plant and animal population dynamics; 

• simultaneous evaluations of wildlife responses and OHV route-specific variables; 

• studies to improve knowledge about the physical and chemical dynamics of soil 

compaction; 

• studies evaluating the effects of erosion, sedimentation, and turbidity downslope 

of OHV-affected sites; 

• improvements in techniques for successful site restoration; 

• improvements in techniques and technologies for assessing OHV impacts over 

large areas and long time periods; 

55 
• studies that evaluate the effectiveness of various techniques to manage OHV use 

and its ecological and socioeconomic effects while simultaneously providing the 

greatest satisfaction among all land users; and 

• studies that determine the economic and sociological costs of OHV use. 

The experimental design of past studies on the ecological effects of OHVs often proved 

inadequate for providing reliable, defensible results. In particular, use of comparable treatment 

and control sites with adequate replication has been minimal. To better elucidate OHV effects on 

wildlife, habitats, and vegetation, there is a need for well-replicated research based on treatments 

and controls ranging across various spatial and temporal scales within the full range of habitat 

types represented on BLM lands. In desert ecosystems, for example, the impacts of OHV 

activities can occur at several spatial and temporal scales (Forman and others, 2003: p. 129-134; 

Matchett and others, 2004; Brooks and Lair, 2005; see discussion in section 2.1); thus, research 

conducted across the scale(s) at which OHV activities and ecosystem responses are likely to 

occur will produce the most reliable information about OHV effects on land health and users of 

the land (Brooks and Lair, 2005). There also is a need for long-term monitoring of OHV effects 

at both designated OHV sites and undesignated (rogue use) sites, as well as revegetation sites. 

Monitoring and research approaches that take advantage, and push the advancement, of 

existing and emerging technologies are needed to fully represent the scale and diversity of OHV 

impacts likely affecting plant and animal populations and communities, and to ascertain indicator 

thresholds as they pertain to BLM’s land health standards. Current technologies, including 

satellite imagery, GPS, and GIS, among others, would be extremely useful in broadening the 

scope of OHV-impact research from site-based effects to ecosystems and landscapes. 

Technology also provides opportunities for better assessing OHV effects on wildlife, vegetation, 

and other natural resources. Finally, multiple assessments and the simultaneous recording of 

independent and dependent variables would improve overall results and better inform 

management decisions. 

5.2 Monitoring and Research Needs 

Remaining questions about effects of OHVs on ecosystems and people are numerous and 

varied. Information regarding management approaches for sustaining or restoring resources—

from the level of single OHV routes to entire landscapes—to pre-disturbance conditions while 

still providing for quality OHV experiences is especially sparse. Therefore, the need for solid, 

well-designed research for supporting management decisions cannot be understated. Based on 

major unresolved issues and questions raised in the OHV impacts literature, current research 

needs include (but are not limited to) 

• well-designed research capable of producing scientifically sound results by 

incorporating planned comparisons of treatment (OHV-impacted) and control 

(unimpacted/reference) sites, as well as studies that take advantage of 

opportunities to compare “before and after OHV-impacts” at sites that may be 

slated for—but are not yet impacted by—OHV use; 

• studies to evaluate OHV effects on natural resource attributes at various spatial 

and temporal scales, particularly those appropriate for evaluating and 

understanding effects occurring at watershed, landscape, and plant and animal 

population levels; 

• studies to improve the overall understanding of habitat fragmentation and roadedge effects caused by OHV activities in OHV-impacted habitat types; 

56 
• studies that evaluate effects of OHV activities at various gradients in OHV 

disturbance levels and at varying distances from OHV routes; 

• studies to evaluate how OHV activities and habitat fragmentation affect plant and 

animal population dynamics; 

• simultaneous evaluations of wildlife responses (from individual- to populationlevel scales) and route-specific variables, including route type and width, and the 

intensity, noise levels, and speed of traffic; 

• studies to improve the understanding of the physical and chemical dynamics, as 

well as the consequences, of soil compaction, sedimentation, and turbidity 

downslope of OHV-affected sites; 

• improvements in techniques and technologies for assessing OHV impacts over 

large areas and long periods of time; 

• improvements in techniques for successful site restoration; 

• studies to determine the economic value of ecosystem goods and services 

provided by natural resources on or in BLM (and affected) lands and waters; and 

• studies to determine the costs of OHV use, including degradation or loss of 

ecosystem goods and services, loss of supportive constituencies, 

managing/enforcing regulations of OHV use, and restoring OHV-impacted sites. 

5.2.1 Scientifically Rigorous Research Projects 

Several studies discussed in this document compared areas impacted (treatment) to areas 

unimpacted (control) by OHVs. Many studies, however, did not compare treatment and control 

sites, or the control and treatment sites differed with regard to some major factor (for example, 

other recreation activities, livestock grazing, logging, or energy-development activities) that 

could have masked true differences pertaining to OHV effects. In other words, controls in 

research and monitoring programs provide the necessary frame of reference for identifying true 

effects of the variable(s) of interest; in turn, identifying true effects will better inform 

management actions. Therefore, among the greatest research needs pertaining to OHV effects on 

natural resources are scientifically defensible studies based on planned comparisons of OHVimpacted and unimpacted sites that are otherwise similar in terms of soils, topographies, climatic 

patterns, plant and animal communities, non-motorized activities, and other potentially 

confounding factors. This is particularly important for developing appropriate threshold indicator 

values for sustaining current resource conditions or triggering management actions. 

An additional approach to research that can provide informative results is to conduct 

before-and-after comparisons of sites previously unimpacted by OHV use but slated for future 

OHV use. Although year-to-year variations in climate and plant or animal population cycles can 

introduce too much variation in ecological before-and-after data to provide statistically 

meaningful results, this research approach can provide valuable information when conditions are 

reasonably similar during each phase of the project. Thus, it would be prudent to take advantage 

of such opportunities as they come up. 

Technologies and tools that could prove very useful in study design and site selection 

pertaining to OHV effects include satellite imaging and GIS. Although they are still advancing 

rapidly in terms of their capabilities and utilities, they are nonetheless already very helpful in 

studies ranging from the site to the landscape scale. Satellite imagery can help locate sites with 

differing extents of OHV activity, and, when rendered into GIS database layers, they can provide 

opportunities for repeating imagery over time and evaluating landscape-scale changes. U.S. 

57 
Geological Survey scientists, for example, are currently using these tools and technologies to 

study the effects of energy-development activities in sage-steppe systems on BLM lands in 

Wyoming (C. Aldridge, pers. comm.). 

5.2.2 OHV Effects at Various Spatial and Temporal Scales, Across Habitat Types 

Past studies regarding OHV impacts on natural resources have focused primarily on 

effects at the single route or site level; thus, the overall understanding of landscape-, watershed-, 

and population-scale effects, including habitat/population fragmentation, is inadequate for 

managing OHV effects at larger spatial and longer temporal (Boyle and Samson, 1985) scales. 

Most of what is known pertains to very localized and short-term effects on sub-populations. 

Even then, past studies evaluating changes in animal densities of sub-populations may have 

violated basic assumptions of closed-population status. That is, studies that “failed to detect 

OHV effects on animal densities” may have been confounded by the immigration of new 

individuals after original individuals experienced poor survivorship due to direct or indirect 

effects of OHV activities. Mark-recapture studies that take advantage of radio-marking 

technologies, both in and away from the affected site, can help evaluate the extent to which 

assumptions of closed versus open populations are upheld or violated. 

Research is also needed to better understand the edge effects of roads on different 

habitats and populations of different species or taxonomic groups. Here again, scale is important. 

Many past studies have evaluated the effects of traffic in immediately adjacent habitats (road 

rights-of-way, for example), whereas the effects may be realized well into the habitat interior 

quite far from travel routes. Thus, study designs that incorporate gradients of distance away from 

OHV routes or route networks would be crucial. 

5.2.3 Research Regarding Effects of OHVs on Animal Populations 

Many prior studies of OHV impacts on wildlife have focused on indirect indicators of 

animal population health, such as distribution and behavior, at the expense of more direct 

indicators, such as population trend/size, gender and age ratios, and productivity. In part, this is 

because such data can be significantly more difficult and expensive to collect than behavioral 

and distribution data. Studies that address possible changes in plant and animal genetics in 

ecosystems fragmented by OHV roads and trails also are needed. For species that naturally occur 

at low densities, such as the desert tortoise, bighorn sheep (Ovis canadensis), and mountain lion, 

this is particularly important, as isolation of their populations could more easily lead to localized 

extinctions. 

Understanding direct effects of OHV activities on wildlife populations would be further 

enhanced by research that evaluates wildlife population dynamics in different habitat types (Bury 

and others, 1977), at different spatial and temporal scales, and under different conditions (levels) 

of OHV use. Likewise, research programs that incorporate representative and disparate 

taxonomic groups would help identify ecosystem-level effects. For example, a given habitatfragmentation factor (a network of OHV routes) might not have any significant impact on large 

ungulates, but it might lead to complete loss of genetic diversity among flightless invertebrates. 

In conjunction with this type of research, it would be important to identify which specific 

environmental and anthropogenic factors promote or limit the exchange of individuals across 

OHV-impacted habitat types or landscapes. 

Few past studies have employed multiple-assessment or simultaneous survey methods to 

detect rare or sensitive species that may not be detected through standard monitoring techniques, 

resulting in biases towards more common and easily detected species and an incomplete 

58 
understanding of the community at risk. For example, multiple survey techniques can be used to 

determine whether changes in species composition are due to changes in detectability across 

habitat types, times of day or season, geographical area, and abundance. For detecting reptiles 

and amphibians, researchers could combine noosing, pitfall sampling, night surveys, and road 

driving surveys. For mammal studies, track, scat, and camera surveys might enhance species 

detections. Many avian-ecology researchers now use combinations of road driving, point 

sampling, and mist netting, in addition to double-observer methods, for improving overall survey 

results. 

Studies of OHV effects on wildlife also could be improved through simultaneous 

recording of independent and dependent variables. For example, many studies relating effects of 

OHVs on animal populations also lack any measurements of static and dynamic road- and OHVrelated variables—such as width and traffic intensity/noise levels (Andrews, 1990)—that may 

strongly influence species behavior, distribution, abundance, survivorship, and productivity. 

Given the importance of relationships between these independent and dependent variables, 

employing long-term monitoring that incorporates their simultaneous measurement would be 

very helpful (see Andrews, 1990). This type of information would be particularly useful for 

identifying indicator thresholds that might trigger area closures, re-routing of OHV routes, and/or 

implementing a restoration project. A variety of technologies and tools now available would be 

useful in these endeavors, including satellite telemetry, Global Positioning Systems (GPS), 

infrared photography, pneumatic vehicle counters, and so on. 

Finally, there are a number of specific questions that researchers could ask with respect to 

OHV effects on animal populations. For example, the discussion in section 2.3.3 regarding edge 

effects of OHV routes raises the question of whether high densities of animals in roadside 

habitats represent favorable conditions for native fauna or dominance by invasive or non-native 

organisms and, if the former, whether these habitats are population sources or sinks (see Van 

Horne, 1983). 

5.2.4 Research to Determine Socioeconomic Costs Associated with OHV Use 

The literature search conducted for this report yielded no published studies of the 

economic costs associated with OHV use. Costs could include the degradation or loss of crucial 

ecosystem goods and services (such as a decline in water quality due to accelerated 

sedimentation and increased turbidity in wetlands caused by OHV traffic, or the loss of livestock 

and wildlife forage due to soil compaction caused by OHV traffic), the loss of economic and 

political support from both OHV users and non-motorized constituencies whose recreation 

experiences (or other land uses) are degraded by OHV effects, and the costs of managing OHV 

recreation and restoring sites impacted by OHV traffic. Although the costs of OHV effects may 

be challenging to assess, there are efforts underway to first identify the economic values of 

ecosystem goods and services and factor them into economic analyses of human activities. For 

example, Ducks Unlimited Canada and The Nature Conservancy have co-published a report that 

calls for the immediate acceleration of “efforts to measure, protect, and enhance the natural 

capital of Canada,” including the need to “invest in science to measure, value, and monitor 

ecological goods and services, and develop economic instruments that recognize and protect 

natural capital, rather than continue to reward its destruction” (Olewiler, 2004). A companion 

report details the values of goods and services provided by wetlands (Gabor and others, 2004). 

Similar efforts to place a value on the goods and services provided by lands affected by OHV 

activities would provide the necessary basis for balancing economic equations of OHV use. 

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5.2.5 Research to Improve Site Restoration 

The success of site restoration ultimately depends on the ability to return soils, including 

abiotic crusts and desert pavement, vegetation, and biotic crusts to their original condition. 

Therefore, research is needed to study the mechanisms behind, and mitigation that could 

diminish, changes in soils. Adams and others (1982) called for research on the disproportionate 

hardening of only slightly compacted desert soil and whether soil hardening is caused by 

chemical cementation or by a greater number of interstitial water bonds remaining between soil 

particles after drying. Webb and others (1978) called for studies that explore the amount of time 

required for soils to respond to revegetation of OHV sites and develop ways of mitigating 

changes in soil properties during OHV use. More recently, Bolling and Walker (2000) expressed 

the need for long-term monitoring and analysis of soil microbial populations. Answers to these 

and other important questions that elucidate the ways in which systems recover from the effects 

of OHVs are crucial to the possibility of long-term OHV use without incurring irreparable 

damage to ecosystems. 

6.0 Conclusion 

It is apparent from the literature identified and discussed herein that the effects of OHV 

activities on ecosystems are diverse and potentially profound, if poorly understood. Studies have 

revealed a variety of effects on soil properties, watersheds, and vegetation resulting from one to 

multiple passes by OHV vehicles. Likewise, research has shown a variety of OHV effects on 

both OHV users and non-motorized recreators. Considerably less is known about impacts to 

wildlife or air and water quality. Whereas the results of past OHV-effects research have been 

reasonably consistent in demonstrating the nature of OHV effects in the immediate vicinity of 

single trails and OHV sites, there is a need for stronger emphasis on the cumulative effects—

both spatial and temporal—of OHV use. For example, the effects of a single OHV route on a 

watershed may be greater when it is part of a route network than when it is the only route within 

the watershed. Furthermore, a network of OHV routes is likely to accommodate more users than 

a single route. Therefore, route density is an important consideration when evaluating and 

monitoring OHV effects across a given landscape. 

The Council on Environmental Quality’s (CEQ) regulations for implementing the 

National Environmental Policy Act define a cumulative impact as “...the impact on the 

environment that results from the incremental impact of the action when added to other past, 

present, and reasonably foreseeable future actions regardless of what agency (Federal or nonFederal) or person undertakes such other actions” (Council on Environmental Quality, 1997). In 

other words, cumulative impacts can result from what may appear on small spatial or temporal 

scales to be minor, but which become collectively significant when such actions take place over 

large areas and long periods of time. Moreover, one effect may interact with other effects to 

generate additional effects that are not apparent when evaluating effects individually. 

The concept of cumulative impacts as they relate to OHV activity, therefore, must be 

applied in a landscape context, as these impacts are not site-specific and may affect adjacent or 

even more remote habitats and landscapes. For example, dust created from OHV activities can be 

dispersed to areas far away from habitats directly impacted by OHV activities. Likewise, erosion 

of soils during heavy rain events may increase sedimentation far downstream of areas directly 

subjected to OHV activities, and edge or corridor effects of OHV routes may promote 

widespread dispersal of non-native and invasive species. Thus, there is a need for greater 

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monitoring and research emphasis on the effects of OHV activities not only in the areas directly 

subjected to those activities, but across impacted habitat types, watersheds, and landscapes. 

Overall, monitoring of cumulative impacts is needed at a scale larger than the physical imprint of 

the OHV-use area. By the same token, economic analyses of OHV use are needed to account for 

not only the immediate and apparent economic benefits, but also the long-term, large-scale, and 

ongoing costs associated with OHV use. Without factoring these variables into models of 

economic impacts, true cost:benefit ratios of OHV use will remain unknown. 

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202 
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on natural terrain at seven sites in the San Francisco Bay area: Environmental Geology, v. 2, 

no. 5, p. 295–319. 

Wilshire, H.G., Shipley, Susan, and Nakata, J.K., 1978, Impacts of off-road vehicles on 

vegetation: Transactions of the North American Wildlife and Natural Resources Conference, 

v. 43, p. 131–139. 

Wolcott, T.G., and Wolcott, D.L., 1984, Impact of off-road vehicles on macroinvertebrates of a 

mid-Atlantic beach: Biological Conservation, v. 29, no. 3, p. 217–240. 

210 
211 

Appendix 2. Search Methods and Results of Off-Highway Vehicle 

Effects Literature and Internet Resources 

2.1 Methods 

2.1.1 Literature Search 

From May 10–26, 2006, a comprehensive literature search was conducted to encapsulate 

the current knowledge on effects of off-highway vehicle (OHV) activities as it pertains to natural 

resource attributes addressed by the Bureau of Land Management’s (BLM) land health standards 

(U.S. Bureau of Land Management, 2001; Pellant and others, 2005). The search was conducted 

through 33 electronic literature databases available at Colorado State University’s (CSU) library 

(table 2.1) and search engines available on the Internet. The databases searched encompassed all 

major, and some minor, sources of relevant literature, including professional, peer-reviewed 

journal papers and technical reports/articles published in magazines representing the industrial 

sector and non-governmental conservation organizations. 

Search terms used included “OHV,” “off-highway vehicle,” “ORV,” or “off-road 

vehicle” combined with terms representing the BLM’s land health standards, including soil 

health and watershed condition, nutrient cycling, wildlife health and habitat quality for native 

plants and animals (especially for species of special status), water quality, and air quality (table 

2.1). In addition, searches were conducted on the socioeconomics of OHV use. Within each 

database searched, all search terms were applied to the 26 topic areas (see footnote 1 associated 

with table 2.1) listed in CSU’s library database subject list. Relevant citations also were gleaned 

from highly relevant reports and journal articles. All relevant citations identified were grouped 

by land-health categories to build extensive bibliographies for each land-health category. If a 

given citation was relevant to more than one land-health category, it was listed in each of the 

related bibliographies. 

2.1.2 Internet Search 

Specific goals of the Internet search were to (1) identify websites and other Internet 

resources provided by the BLM and U.S. Forest Service (FS) regions 2 (time constraints limited 

this search to Colorado), 3, and 4; (2) classify OHV-related Internet websites by focus/intent and 

resource type; and (3) report on highly relevant websites. Two primary products were 

subsequently developed: (1) a thesaurus (table 2.2) of search topics and terms related to OHV 

effects, and (2) a list of significant BLM and FS resources and corresponding Internet websites. 

The thesaurus was developed to identify Internet-based resources regarding OHVs and the types 

of OHV effects. All possible combinations of search terms were used, but any one search string 

depended on the search engine used. Although FirstGov is a good search engine for finding 

government publications and reports, it limits search results to 100. In contrast, Google returns 

up to 1000 results, and its filter may be used to constrain searches to a specific type of website 

(for example, “.gov”); however, Google is unable to employ multiple exclusion criteria to 

exclude irrelevant websites (for example, it cannot specify “NOT FS” and NOT BLM”) whereas 

FirstGov does handle multiple exclusion criteria. In other words, Google was searched with an 

OHV term combined with an impact term while limiting any one search to “BLM,” “EPA” (U.S. 

Environmental Protection Agency), “FS” (U.S. Forest Service), “NPS” (U.S. National Park 

Service), or “USGS” (U.S. Geological Survey) sites. Then FirstGov was searched with the same 
Table 2.1. Search terms used and publication years included when using search engines and 33 electronic literat

Colorado State University’s library to assemble an extensive bibliography of literature on effects of off-highway ve

Search term 

Database searched (for publications years)1 

Air 

quality Benefits 

Domestic 

livestock 

grazing Erosion Noise 

Soil 

impacts 

Travel and 

transportation 

management 

Visual 

impacts 

Vegetati

impact

AGRICOLA EBSCO 

(1970-2006) X X X X X 

AGRICOLA National 

Agricultural Library (1970-2006) X X X X X 

Agricultural and 

Environmental Biotechnology Abstracts (1993-2006) X X X X X X 

Agricultural Sciences (in 

Cambridge Scientific Abstracts) (compilation of multiple databases2) X X X X X 

Animal Behavior 

Abstracts (1982-2006) X X X 

Applied Science and 

Technology Abstracts (1983-2006) X X X X X X 

ASFA 1: Biological 

Sciences and Living Resources (1971-2006) X X 

212 
213 

Search term 

Database searched (for publications years)1 

Air 

quality Benefits 

Domestic 

livestock 

grazing Erosion Noise 

Soil 

impacts 

Travel and 

transportation 

management 

Visual 

impacts 

Vegetati

impact

ASFA 2: Ocean Technology, Policy & Non-Living Resources (1971-2006) X X X X X ASFA 3: Aquatic 

Pollution and Environmental Quality (1990-2006) X X X X X X 

BioEngineering 

Abstracts (1993-2006) X X X 

Biological Abstracts 

(1969-2006) X X 

Biological Sciences 

(1982-2006) X X 

Biological Sciences (in 

Cambridge Scientific Abstracts) (compilation of multiple databases2) X X 

Biology Digest (1989-

2006) X 

Biotechnology and 

Bioengineering Abstracts (1982-2006) X X X 

CAB Abstracts Archive 

(1900-1973) 

Ecology Abstracts 

(1969-2006) X X X 
214 

Search term 

Database searched (for publications years)1 

Air 

quality Benefits 

Domestic 

livestock 

grazing Erosion Noise 

Soil 

impacts 

Travel and 

transportation 

management 

Visual 

impacts 

Vegetati

impact

EIS: Digests of 

environmental impact statements (1985-2006) X 

Engineering Index 

(1884-2006) X X X 

Environmental 

Engineering Abstracts (1990-2006) X X X 

Environmental Sciences 

& Pollution Management (compilation of multiple databases2) X X X X X 

Forest Service database 

(dates not indicated) X X X X X 

Geobase (1980-2006) X X Human Population & 

Natural Resource Management (1995-2006) X X 

Plant Management 

Network (compilation of multiple databases2) X 

Plant Science (1994-

2006) X 

Pollution Abstracts 

(1981-2006) X X X 
215 

Search term 

Database searched (for publications years)1 

Air 

quality Benefits 

Domestic 

livestock 

grazing Erosion Noise 

Soil 

impacts 

Travel and 

transportation 

management 

Visual 

impacts 

Vegetati

impact

Pollution Management & 

Environmental Sciences (in Cambridge Scientific Abstracts) (compilation of multiple databases2) X X X 

Threatened and 

Endangered Species System (dates not indicated) X 

Toxicology Abstracts 

(1981-2006) X X 

Water Resources 

Abstracts (1967-2006) 

Wildlife & Ecology 

Studies Worldwide (1935-2006) 

Zoological Record 

(1978-2006) 

1Topic areas searched in databases included biology, botany, civil engineering, construction management, earth resources, ecology, eng

environmental health, fishery, fisheries, forestry, forest science, geology, hydrology, life sciences, natural resource recreation, tourism, 

sciences, plant science, plant pathology, rangeland ecosystem science, soil and crop sciences, toxicology, water resources, weed sciencebiology, zoology. 

2Dates vary by database.
Table 2.2. Search topics and their associated search terms used in searching the Internet 

for publications and documents pertaining to off-highway vehicle effects and policies. 

Search topic Search term(s) 

OHV 

Off-road vehicle 

Off-highway vehicle 

Off-road vehicles 

Air quality Air quality 

Benefits Benefits 

Domestic livestock grazing Domestic livestock grazing 

Erosion Erosion 

Human dimension Human dimension 

Human dimensions 

Noise Noise 

Soil impact Soil impact 

Soil impacts 

Transportation management Transportation management 

Travel Travel 

Vegetation impact Vegetation impact 

Vegetation impacts 

Visual impact Visual impact 

Visual impacts 

Water quality Water quality 

Wildlife impact Wildlife impact Wildlife impacts 

terms while excluding “BLM,” “EPA,” “FS,” “NPS,” “USGS,” and “.com” domains, which 

captured websites representing individual States, military agencies, and other non-commercial 

entities. 

After the Internet searches were conducted, each website identified were reviewed 

(limited to 2 minutes per website) and assigned a relevance-class code (relevance to OHV effects 

and policies; table 2.3). Websites classified as H (highly relevant), R (relevant), or S (slightly 

relevant) were further categorized by focus area (table 2.4). All BLM and FS regions 2 

(Colorado only), 3, and 4 websites were included in the results tallies; websites containing news 

releases, specific flora assessments, and BLM Resource Advisory Council meetings were 

omitted. Highly relevant websites were selected for presentation. 

2.2 Results 

2.2.1 Literature Resources 

The literature search, and additional sources uncovered outside of the formal search, 

yielded approximately 700 citations, a number of which overlap in terms of their relevance to 

categories of land health (table 2.5). 

216 
Table 2.3. Relevance class codes and definitions pertaining to Internet websites found to contain 

information regarding off-highway vehicle effects and policies. 

Relevance class Definition 

H Highly relevant—high-quality resources related directly to OHV impacts; 

generally included number of OHV trail miles and visitor days, or reasons why 

OHVs excluded from specific locations; includes OHV strategy/plan documents 

or public communication sites on OHV recreation areas 

R Relevant—targeted mention of OHV but not as specific or detailed as a highly 

relevant site 

S Slightly relevant—mention of OHV but with few supporting statements or details

U Unrelated—no or minimal OHV content 

Z Unable to access, page would not load, URL has changed, page loads but is 

empty of content 

ZDup Content duplicate of previous entry 

Table 2.4. Focus areas and definitions of Internet websites found to contain information regarding 

off-highway vehicle effects and policies. 

Focus area Definition 

Administration Information sourced from the Federal level 

Citizen input Site contains or informs about public comments on OHV use 

EIS Site contains a draft or final environmental impact statement (EIS) or 

environmental assessment (EA)—attempt was to keep this category to sites related 

to actions up through completion of a management plan although there is some 

overlap with the next category due to title ambiguity 

Impact Site focus was measurement of impact 

Legal Response to appeals regarding travel management plans or EIS documents 

Manual Site containing a handbook or manual 

Management plan Sites with completed management plans or actions stemming from implementation 

of a management plan; includes monitoring, revision of plans, assessment for 

roadless areas, and road analyses 

Monitoring Usually annual reports of monitoring activity prescribed by a management plan 

Press Site with information in the form of a press release or media announcement 

Road guide Sites intended to provide public information about OHV and recreation site use; 

includes descriptions, trail maps, event calendars, safety, licensing and regulation, 

and closure information 

217 
Table 2.5. Number of relevant publications found, and publication dates included, in a literature 

search on effects of off-highway vehicle activity as they pertain to the U.S. Bureau of Land 

Management’s land health standards. 

Land health category No. citations Years included 

Soils 314 1959-2006 

Air quality 104 1970-2006 

Water quality 218 1959-2005 

Vegetation 326 1962-2006 

Wildlife 387 1970-2006 

Land users 211 1967-2006 

2.2.2 Internet Resources 

The Internet search yielded nearly 30,000 State and Federal government websites, of 

which 8,693 were unique (a single HTML page or .pdf file); 23 percent (n = 1,998) were BLM 

websites, 55 percent (n = 4,817) were FS websites, and 7 percent (n = 568) were NPS websites 

(table 2.6). FS regions 2 (Colorado only), 3, and 4 together represented 12 percent of the 

websites. Of the 8,693 unique sites, 2,495 were visited and reviewed (29 percent) using the 

methods described above. All search term combinations returned at least 100 results, and some 

returned as many as 3,700 (table 2.6). 

Of the unique websites identified, only 13% (n = 335) were classified as highly relevant; 

15 percent were relevant, 22 percent were slightly relevant, and 50 percent were unrelated/not 

available (figure 2.1). Forty-seven percent of those classified as highly relevant were BLM sites, 

and 53 percent were FS sites. The majority of highly relevant sites (68 percent) were dedicated to 

environmental impact statements (EIS) or management plans (figure 2.2). Only two percent of 

the highly relevant sites focused on measuring or monitoring the effects of OHV activities. When 

all sites were considered, a slightly higher percentage of sites (approximately 5 percent) included 

monitoring or impact assessment (figure 2.3). 

Key similarities between highly relevant BLM and FS websites (figures 2.4 and 2.5) 

included equal emphasis on road guides (about 12 percent of sites) and little emphasis on 

monitoring and impacts (0 and 1 percent for BLM, respectively; 1 and 1 percent for FS, 

respectively). The BLM sites had slightly greater emphasis on EISs and management plans (73 

percent) than did FS sites (65 percent). Interestingly, 10 percent of the FS sites concerned legal 

issues—primarily appeals to decisions—whereas no material of this type was found on BLM 

websites. This may be due to an agency decision of what type of material is posted to the Internet 

or it may be a result of a difference in EIS/management plan implementation status between the 

two agencies. Table 2.8 presents examples of five highly ranked web sites (if available) from 

BLM and/or FS Region 2 for each of the focus areas. 

218 
Table 2.6. Search results, by topic, for all Internet websites pertaining to off-highway vehicle 

effects and policies (n = 22,990).

Search topic Results 

Air quality 3,040 

Benefits 3,081 

Domestic livestock grazing 373 

Erosion 3,228 

Human dimension(s) 241 

Noise 2,650 

Soil impact(s) 461 

Transportation management 453 

Travel 3,726 

Vegetation impact(s) 155 

Visual impact(s) 1,392 

U: n = 1,068; 43%

%

3%

5%

S: n = 550; 22%

R: n = 364; 1

H: n = 335; 1

Z: n = 175; 7

Figure 2.1. Breakdown of unique Internet websites (n = 2,495) classified as “highly relevant” (H), 

“relevant” (R), “slightly relevant” (S), and “unrelated/unavailable” (U, Z) to off-highway vehicle effects and 

policies. 

219 
220 

Figure 2.2. Focus areas of Internet websites (n = 333) classified as highly relevant to off-highway vehicle 

effects and policies. 

Figure 2.3. Focus areas for all Internet websites (n = 1,230) classified as highly relevant, relevant, and 

somewhat relevant to off-highway vehicle effects and policies. 

Citizen input: n = 80; 7%

Management plan: n = 501; 40%

Environmental impact 

statement: n = 383; 31%

Road guide: 

n = 147; 12% Press: n = 36; 3%

Monitoring: n = 31; 3%

Administration: n = 26; 2%

Legal, manual, impact, other: n = 26; 2%

Other: n = 

83; 7%

Press: n = 17; 5%

Environmental impact statement: n = 139; 41%

Management 

plan: n = 93; 27%

Road guide: n = 40; 12%

Legal: n = 

17; 5%

Citizen input: n = 15; 5%

Administration: n = 5; 2%

Manual: n = 3; 1%

Impact: n = 2; 1%

Other: n = 

12; 4%

Monitoring: n = 2; 1%
221 

Figure 2.4. Focus areas of U.S. Bureau of Land Management Internet websites (n = 155) classified as 

highly relevant, relevant to off-highway vehicle effects and policies. 

Administration: n = 3; 2%

Road guide: n = 18; 12% Citizen input: n = 9; 6%

Environmental impact statement: n = 61; 38%

Impacts: n = 1; 1%

Legal: n = n/a; 0%

Manual: n = 3; 2%

Management plan: n = 54; 35%

Monitoring: n = n/a; 0%

Press: n = 6; 4%
Road guide, 22, 13% 

Monitoring, 2, 1% 

Press, 10, 6% 

Management plan, 

39, 22% 

Manual, n/a, 0% 

Legal, 17, 10% Impacts, 1, 1%

Citizen input, 6, 3%

Administration, 2, 1%

Environmental impact statement, 77, 43%

Figure 2.5. Focus areas of U.S. Forest Service (regions 2 [Colorado only], 3, and 4 only) Internet websites (n 

= 176) classified as highly relevant to off-highway vehicle effects and policies. 

The large percentage of highly relevant websites assigned to the EIS and management 

plan categories indicate that OHV impact is an important topic to both the BLM and FS. The 

relatively small number of agency sites that address assessment or monitoring of OHV effects 

suggests that assessment or monitoring of OHV effects may be important topics for future 

website development. EISs and management plans do not focus on providing quantitative 

measures for determining the suitability of OHV trails (aside from the problem of trail 

redundancy for a given area); a trail-management plan of “fewer but better” seemed to be the 

approach in most plans, although a few plans specified that areas with a high degree of slope are 

unsuitable for trails. Almost no plans addressed OHV-related dust or noise problems, although 

some addressed areas of significant erosion by moving trails. 

Overall, there appear to be more FS than BLM websites dealing with OHV management 

and related issues, including monitoring and the legal response to approved plans. Although road 

management plans are being developed for many land units by both the BLM and FS, only a few 

of these plans include OHV travel as an aspect of road management. The BLM, however, has 

produced a nation-wide OHV strategy, and Montana, Wyoming, and Idaho also have prepared 

state OHV management strategies. In general, policy appears to be taking the form of 

management plan implementation (such as closing areas due to muddy conditions or fire risk 

rather than making specific policy statements). 

222 
223 

Table 2.7. Internet websites classified as highly relevant, by focus area and source, pertaining to off-highway vehpolicies. 

Focus/ source1 Title and URL Administration 

BLM BLM National Management Strategy for Motorized Off-Highway Vehicle Use 

http://www.fs.fed.us/recreation/programs/ohv/blm_strategies.pdf

FS-R2 Recreation, Wilderness, and Related Resource Management WO Amendment 2300-94-3 

http://www.fs.fed.us/cdt/admin.htm

Environmental impact statement 

BLM Environmental Assessment EA No.: AZ-020-04-0115 for the Arizona Association of Four-Wheel Drive C

Jamboree http://www.blm.gov/ca/publish/etc/medialib/blm/az/pdfs/nepa/library/4wd.Par.7790.File.dat/ASA4WDC-EA.pdf

BLM Environmental Assessment: DARPA Grand Challenge 

http://www.blm.gov/ca/pdfs/barstow_pdfs/darpa/chapter_3_affected_environment.pdf

BLM Final environmental impact statement for the Imperial Sand Dunes Recreation Area Management Plan an

Amendment to the California Desert Conservation Plan 1980 http://www.blm.gov/ca/pdfs/elcentro_pdfs/FinalEISandRAMP/FinalEIS.pdf

BLM Red Rock 4-Wheelers Jeep Safari and Fall Campout 5-Year Permit Renewal 

http://www.blm.gov/ut/st/en/info/newsroom/2006/01/blm_renews_jeep_safari.html

FS-R2 Decision Notice and Finding of No Significant Impact for the Clear/Crazy Designated Motorized Trail Sy

River Ranger District, Bighorn National Forest http://www.fs.fed.us/r2/bighorn/projects/projectfiles/clearcrazy/clear_crazy_fonsi_032005.pdf

FS-R2 Scoping Document for the Hunt Mountain Travel Management Plan, Medicine Wheel/Paintrock Ranger 

Bighorn National Forest http://www.fs.fed.us/r2/bighorn/projects/projectfiles/hunt_mtn_carea/scoping_carea.pdf

FS-R3 Munds Park Roads and Trails Project: Environmental Assessment 

http://www.fs.fed.us/r3/coconino/nepa/2004/munds-drft-ea-final-9_24_04.pdf
224 

Focus/ source1 Title and URL Impact 

BLM Air Quality Baseline and Analysis Report, Price Field Office, Price, Utah 

http://www.blm.gov/utah/price/pricermp/documents/Baseline_and_Analysis_Report.pdf

FS-R2 Anthropogenic Influences Used in Conducting Multiple Scale Aquatic, Riparian, and Wetland Ecological 

for the USDA Forest Service – Rocky Mountain Region, Report 2 http://www.fs.fed.us/r2/projects/scp/arw/protocols/anthropogenicinfluencesusedinconductingmultiplescal

Wildlands Resource website that provides publications on PHV effects, restoration, enforcement, policy, and other r

materials http://www.wildlandscpr.org/resources

Legal 

FS-R2 Recommendation Memorandum for Uncompagre Travel Management Plan, July 13, 2000 

http://www.fs.fed.us/r2/projects/nepa/appeal-decisions/2000/gmug/uncompahgre_travel_39.htm

FS-R2 Recommendation Memorandum for Gunnison Interim Travel Restrictions, July 13, 2001 

http://www.fs.fed.us/r2/projects/nepa/appeal-decisions/2001/gmug/gunntrvl_16.htm

FS-R2 Recommendation Memorandum for Uncompahgre Travel Management Plan, June 18, 2002 

http://www.fs.fed.us/r2/projects/nepa/appeal-decisions/2002/gmug/tvl_mgmt_23.htm

FS-R2 Recommendation Memorandum for Uncompahgre Travel Management Plan, June 19, 2002 

http://www.fs.fed.us/r2/projects/nepa/appeal-decisions/2002/gmug/tvl_mgmt_24.htm

FS-R2 Recommendation Memorandum for Radial Mountain Travel Management Environmental Assessment, Se

http://www.fs.fed.us/r2/projects/nepa/appeal-decisions/2001/mbr/radial_mtn_25.htm

Manual 

BLM Western Oregon Plan Revisions: Proposed Planning Criteria and State Director Guidance 

http://www.blm.gov/or/plans/wopr/files/PlanningCriteriaDocument.pdf

BLM Interpreting Indicators of Rangeland Health 

http://www.blm.gov/nstc/library/pdf/1734-6rev05.pdf

BLM Biological Soil Crusts: Ecology and Management 

http://www.blm.gov/nstc/library/pdf/CrustManual.pdf

Management plan 

FS-R2 U.S. Forest Service, Travel Management: New Rule 

http://www.fs.fed.us/r2/recreation/travel_mgmt/
225 

Focus/ source1 Title and URL 

FS-R2 Decision Notice & Finding of No Significant Impact, Grand Mesa Travel Management, December 1, 200

Mesa Counties, Colorado http://www.fs.fed.us/r2/gmug/policy/gm_travel/fonsi_dec2003.pdf

FS-R2 Roads Analysis Report: Medicine Bow National Forest 

http://www.fs.fed.us/r2/mbr/projects/roads/adobepdf/medbow/mbnf_rds_analysis_final.pdf

FS-R2 Roads Analysis Report: Routt National Forest 

http://www.fs.fed.us/r2/mbr/projects/roads/adobepdf/routt/routt_rap_final.pdf

FS-R2 Travel Management Rule, Implementation Safety, Rocky Mountain Region 

http://www.fs.fed.us/r2/recreation/travel_mgmt/references/Final_TravelMgmtStrategy.pdf

Monitoring

FS-R2 Forest Plan Monitoring and Evaluation Reports, Arapaho and Roosevelt National Forests and Pawnee Na

http://www.fs.fed.us/r2/arnf/projects/forest-planning/monitoring/

OHV road guide

BLM Killpecker Sand Dunes Open Play Area, BLM Wyoming Rock Springs Field Office, Wyoming 

http://www.wy.blm.gov/rsfo/rec/dunes.htm

BLM Dunes OHV Area, Farmington Field Office, New Mexico 

http://www.nm.blm.gov/recreation/farmington/dunes_ohv_area.htm

BLM Lark Canyon, El Centro Field Office, California 

http://www.ca.blm.gov/elcentro/larkcany.html

FS-R2 OHV, Pike & San Isabel National Forests, Cimarron & Comanche National Grasslands, South Park Rang

Colorado http://www.fs.fed.us/r2/psicc/sopa/roads.shtml

FS-R2 Rampart Range Motorized Recreation Area, Pike & San Isabel National Forests, Cimarron & Comanche 

Grasslands, South Platte Ranger District, Colorado http://www.fs.fed.us/r2/psicc/spl/spl_ohv.shtml

FS-R2 OHV, Arapaho & Roosevelt National Forests, Sulphur Ranger District, Colorado 

http://www.fs.fed.us/r2/arnf/recreation/ohv/srd/stillwaterpass-grandlake.shtml

1 BLM = U.S. Bureau of Land Management; FS = U.S. Forest Service; R = region (Region 2 limited to Color