Habitat Threats in fie Sagebrush Ecosystem · 2009-03-25 · HABITAT THREATS IN THE SAGEBRUSH ECOSYSTEM: METHODS OF REGIONAL ASSESSMENT AND APPLICATIONS IN THE GREAT BASIN Edited

Habitat Threats in fie Sagebrush Ecosystem:

Edited by Michael J. Wisdom, Mary M. Rowland, and Lowell H. Suring

Forewords by Ecologist David S. Dobkin and

Bureau of Land Management State Director Bob Abbey

Alliance Communications Group 2005

HABITAT THREATS IN THE SAGEBRUSH ECOSYSTEM:

METHODS OF REGIONAL ASSESSMENT AND

APPLICATIONS IN THE GREAT BASIN

Edited by Michael J. Wisdom, Mary M. Rowland, and

Lowell H. Suring

Forewords by Ecologist David S. Dobkin and Bureau of Land Management State Director Bob Abbey

ALLIANCE COMMUNICATIONS GROUP 2005

Contents

......................................................................................................... Authors

Preface: Threats to the Sagebrush Ecosystem-Research and Management Needs

Miclznel J. Wisdom, Mary M. Rowland, and Lowell H. Suring .......... Foreword: Seeking Ecological Sustainability for the Sagebrush Ecosystem

................................................................................... David S. Dobkin

Foreword: Science Assessment of Threats to Sagebrush Habitats and Species-A Foundation for Effective Management

Bob Abbey ............................................................................................. Part I: Methods of Regional Assessment for Sagebrush-Associated Species of Conservation Concern .................................................................

Chapter 1: Evaluating Species of Conservation Concern at Regional Scales

Michael J. Wisdom, Mary M. Rowland, Lowell H Suring, ....................... Linda Schueck, Cara W Meinke, and Steven 7: Knick

Part 11: Regional Assessment of Habitats for Species of Conservation .......................................................................... Concern in the Great Basin

....................................................................................................... Summary

Chapter 2: The Creat Basin at Risk ......................................... Mary M. Rowland and Michael J. Wisdom

Chapter 3: Vegetation Communities Lowell H. Suring, Mnry M. Rowland, Michael J. Wisdom, Linda Schueck, and Cara W. Meinke ...................................................

Chapter 4: Modeling Threats to Sagebrush and Other Shrubland Communities

Lowell H. Suring, Michael J. Wisdom, Robin J. Tuusch, Richard F. Miller, Mary M. Rowland, Linda Schueck, and

.................................................................................... Cara W. Meinke

Chapter 5: Identifying Species of Conservation Concern Lowell H. Suring, &fury M. Rowland, and Michael J. Wisdom ..........

Chapter 6: Habitats for Vertebrate Species of Conservation Concern M a v M. Rowland, Lowell H. Suring, Michael J. Wisdom,

................................................... Cara W. Meinke, and Linda Schueck

Chapter 7: Habitats for Groups of Species Michael J. Wisdom, Mary M. Rowland, Lowell H. Suring, Linda Schueck, Cara W. Meinke, Steven T. Knick, and Barbara C. Wales .................................................................................

Chapter 8: Utility of Greater Sage-Grouse as an Umbrella Species Mary M. Rowland, Michael J. Wisdom, Cara W. Meinke, and Lowell

............................................................................................... E r f , Suring

vii

xiv

Chapter 9: Assumptions and Limitations for Appropriate Use . . Michael J . Wisdom. Maly M Rowland. and Lowell H Suring ..........

Chapter 10: Conclusions and Management Implications Michael J. Wisdom. Lowell I% Suring. and Mavy M Rowland ..........

Appendix 1 : Glossary of Terms ................................................................... Appendix 2: Identifying Species of Conservation Concern in the Sagebrush Ecosystem .................................................................................... Appendix 3: Shortcut Approaches to Multi-Species Assessment ................ Appendix 4: Plant and Animal Species Mentioned in Text. Excluding

................................................................. Species of Conservation Concern

............. Appendix 5: Species of Conservation Concern in the Great Basin

Appendix 6: Habitats and Associated Risks for Species of Concern in ....................................................... the Great Basin Ecoregion and Nevada

Appendix '7: Summary Results for BLM Field Offices in Nevada .............

Authors

Steven To Knick, Research Ecologist, USGS Biological Resources Discipline, Boise, Idaho, USA.

Cara W. Meinke, Wildlife Biologist and Spatial Analyst, USGS Biological Resources Discipline, Boise, Idaho, USA.

Richard F. Miller, Professor of Rangeland Resources, Oregon State University, Corvallis, Oregon, USA.

Mary M. Rowland, Wildlife Biologist, USDA Forest Service, Pacific Northwest Research Station, La Crande, Oregon, USA.

Linda Schueck, Spatial Analyst, USGS Biological Resources Discipline, Boise, Idaho, USA.

Lowell H. Suring, Wildlife Ecologist, USDA Forest Service, Washington Office, Stationed at Rocky Mountain Research Station, Boise, Idaho, USA.

Robin J. Tausch, Supervisory Range Scientist, USPA Forest Service, Rocky Mountain Research Station, Reno, Nevada, USA.

Barbara C. Wales, Wildlife Biologist, USDA Forest Service, Pacific Northwest Research Station, La Grande, Oregon, USA.

Michael J. Wisdom, Research Wildlife Biologist, USDA Forest Service, Pacific Northwest Research Station, La Grande, Oregon, USA.

I-iabitat Threats in the Sagebrush Ecosystem: 5-74, 2005.

Chapter 1: Evaluating Species of Conservation Concern at Regional Scales

Michael J. Wisdom, Mary M. Rowland, Lowell H. Suring, Linda Schueck, Cara W. Meinke, and Steven T. Knick

Background

Federal land managers face the daunting challenge of meeting the needs of hundreds of native species whose habitats or populations are declining or rare (defined as species of conservation concern or species of concern). This is especially true for the sagebrush1 ecosystem, where hundreds of species of concern are distributed over vast areas, and where knowledge of each species' status and response to management is limited. Moreover, the large area over which sagebrush habitats and species are distributed provides an especially difficult challenge for assessment and management, given the diverse conditions and many jurisdictional boundaries and authorities. Most importantly, the many threats to continued persistence of sagebrush habitats and species, coupled with federal laws that require evaluation and mitigation of such threats, point to the need for assessment of risks posed by the threats. The challenge lies with the need for threats assessment that is rapid and geographically extensive, but detailed enough to provide meaningful information for a comprehensive set of species and their habitats.

In response to these needs, we developed methods of regional assessment

Scientific names of plants and animals are given in Appendix 4. except scientific names for species of concern, which are listed in Ap- pendix 2.

that can be used to evaluate sagebrush habitats efficiently, across large areas, and for a large and comprehensive set of species of concern that occupies the sagebrush ecosystem. We acknowledge that many other methods have been effectively used in regional assessments of single species or of general landscape conditions in the sagebrush ecosystem. However, our methods explicitly focus on multi-species assessment, owing to federal laws that require consideration of all native species of concern as part of federal land management.

We consider our methods a starting point, upon which many other complementary analyses can be done. In that context, we anticipate that methods outlined here will be improved over time with refined assessment approaches and with supporting research to enhance our regional knowledge of the status of, and threats to, species and habitats in the sagebrush ecosystem.

Status of the Sagebrush Ecosystem

The sagebrush ecosystem occupies >43 million ha of arid and semi-arid, sagebrush-dominated lands in the western United States and Canada (Knick et al. 2003) (Table 1.1; Figs 1.1, 1.2). As such, this vast area composes one of the largest ecosystems in North America (Center for Science, Economics and En- vironment 2002). Although the sagebrush ecosystem remains large, it has been substantially reduced in area and quality. Causes for loss and degradation are varied and pervasive (Knick et al.

6 PART I: ASSESSING THREATS

TABLE 1.1. Abundance of sagebrush by ecoregion within the sagebrush ecosystem, based on the 90-rn land cover map developed by Comer et al. (20021, as available from the SAGE- MAP Project [http:l/sagernap.wr.usgs.govl

Ecoregion

Percentage o f Area ctf Percentage of all sagebru\h

sagebrush" ihaf ecoregion in eco\y\tem

Black Hills Canadian Rocky Mountains Central Shortgrass Prairie Colorado Plateau Columbia Plateau Fescue-Mixed Grass Prairie Great Basin Klamath Mountains Middle Rockies-Blue Mountains Modoc Plateau and East Cascades Moj ave Desert Northern Great Plains Steppe Okanagan Sierra Nevada Southern Rocky Mountains Utah High Plateaus Utah-Wyoming-Rocky Mountains tk'est Cascades Wyoming Basins

Total

.' Sagebrush was mapped by Comer et al. (2002) as consisting of 10 cover types: (1) Wyoming and basin big sagebrush (Artenlisia rriderztutn wyorningensis, A. t. trideizt~itcz, and A. t. xericensis): (2) black sagebrush (A. nova); ( 3 ) low \agebrush (A. arbu.\cuIn ai"I7~i~cuf~t, A. a. lorzgi[oba, A. a. loizgicuulis, and A. a. thermopola); (4) low sagebrush-mountain big sagebrush (A. a. thet-r?zopola and A. t. vnseyana); ( 5 ) low sagebrush-Wyoming big sagebrush (all subspecies of low sagebrush listed except therinopola; A. t. wyomingensis): 6 ) mountain big sagebrush (A. t. vnseynnn); (7) rigid \agebrush (A. rigidu); (8) silver sagebrush (A. cnna v i ~ c i d ~ ~ l ~ ~ / b o l a n ~ f e r i and A. cana caizn): (9) threetip sagebr~tsh (A. tripartitn tripartita and A. t. rul7icolci); and (10) Wyoming big sagebrush-5quawapple (A. r. cvyon2ingensi.s \hrubland alliance). See Reid et al. (2002) for detailed de5criptions of cover types.

2003, Connelly et al. 2004). Invasion of exotic vegetation, altered fire regimes, road development and use, mining, energy development, climate change, encroachment of pinyon-juniper woodlands, intensive grazing by livestock. and conversion to agriculture, to urban use, and to non-native livestock forage all have contributed to the ecosystem's demise (Noss et al. 1995, lBusch et al. 1995, Knick 1999, Miller and Eddle- man 2000, Bachelet et al. 2001, Bunting et al. 2002).

The combination of detrimental land uses and undesirable processes has prompted scientists to identify the sage-

brush ecosystern as one of the most endangered in the United States (Noss et al. 1995), and 20% of plants and animals associated with the ecosystem may be at risk of extirpation (Center for Sci- ence, Economics and Environment 2002). Millions of ha of the ecosystem have been altered or eliminated during the past century (Hann et al. 1997, West 1999), and <IO% of the ecosystem remains unaltered by human activities (West 1999). Moreover, loss and degradation on federal lands, where most native sagebrush remains, are increasing rapidly (Hemstrom et al. 2002).

As a consequence, federal land man-

h4ETHODS OF ASSESSMENT-lVisdc1172 et al. 7

FIGURE 1.1. Sagebrush ecoregions and adjacent ecoregions of the western United States. Ecoregions are described and defined in detail by The Nature Conservancy (Groves et al. 2000). Green pixels depict existing sagebrush cover types in the ecoregions, based on the 90-m land cover map (Corner et al. 2002) developed from the vegetation classification system of Reid et al. (2002). For context, existing sagebrush cover types are overlaid on the historical range of the two recognized species of sage-grouse, greater sage-grouse and Gunnison sage-grouse, shown in blue (from Schroeder 2002).

agers are increasingly concerned about the fate of the sagebrush ecosystem and its associated species. A variety of scientific assessments have documented the many problems in the ecosystem (Hann et al. 1997, West 1999, Miller and Eddleman 2000, Connelly et al. 2004), yet efforts to halt or reverse loss and degradation have been unsuccessful at large scales (West 1999, Hemstrom et al. 2002). For example, in the Great Basin, cheatgrass and other exotic plants continue to displace extensive areas of native sagebrush following intensive grazing and large, intense wildfires (Billings 1994, Menakis et al. 2003, Bradley and Mustard 2005). In the Wy-

oming Basins and adjacent areas, pervasive energy development has fragmented sagebrush habitats over a vast area (Braun et al. 2002, Knick et al. 2003, Rowland et al. 2005). In the Co- lumbia Plateau and Snake River Plain, agricultural development has substantially reduced the percentage of land historically occupied by sagebrush (Hann et al. 1997, Connelly et al. 2004). Finally, electric transmission lines and roads are common throughout the ecosystem, causing a variety of negative effects that are difficult or impossible to fully mitigate (Connelly et al. 2004). Galls for more intensive, sustained, and extensive conservation and restoration


FIGURE 1.2. Existing sagebrush by administrative responsibility and land ownership across ecoregions of the western United States. Land ownerships listed as "Other" are given in Table 1.2.

efforts in the ecosystem are growing, coupled with the realization that such efforts require monumental spatial and temporal scales of application to be effective (Knick 1999, Bunting et al. 2002, Hemstrom et al. 2002).

Perhaps the most notable indication of problems in the sagebrush ecosystem has been the significant and continuing decline in habitats and populations of greater sage-grouse (Connelly and Braun 1997, Schroeder et al. 1999. Connelly et al. 2004). A variety of detrimental land uses pose major threats to this species' persistence (Braun 1998; Schroeder et al. 1999; Hemstrom et al. 2002; Wisdom et al. 2002a, b, c; Con- nelly et al. 2004; Rowland 2004). New guidelines were developed recently (Connelly et al. 2000) to help managers conserve and restore habitats for the

species at the stand scale, but similar guidelines do not exist for regional scales that encompass all or major portions of the species7 range. The cumulative effects of management at these large scales can greatly influence the likelihood of regional extirpation of greater sage-grouse (Raphael et al. 200 1 ). Moreover, recent research over extensive sagebrush landscapes (Rapha- el et al. 2001; Hemstrom et al. 2002; Wisdom et al. 2002a, b, c; Connelly et al. 2004) has provided new and compelling knowledge about status, trends, and risks for sage-grouse habitat that could be used for effective conservation and restoration planning across the species' range.

In addition to sage-grouse, rnany other plants and animals associated with the sagebrush ecosystem are of conser-

METHODS OF ASSESSMENT-?'ViLs~ic~m er al. 9

vation concern. Wisdom et al. (2000) identified 30 species of vertebrates in the Interior Columbia Basin that are closely associated with sagebrush habitats, and that are of concern because of declining or rare habitats or populations. Dobkin and Sauder (2004) identified 61 species of birds and small mammals having a strong affinity or a complete dependence on sagebrush, and Rich et al. (2005) described trends for 22 taxa of sagebrush-associated birds. In addition, as part of our methods described here, we identified >350 species of sagebrush-associated plants and animals of conservation concern within the historical range of greater sage- grouse (see IdentiJji Species of Coizser- vation Concern for Assessment it? the Ecoregion and Appendix 2).

Similar lists of species of concern, or species with other special status designations, have been developed by State Natural Heritage Programs and by state and federal agencies. Yet few methods have been developed and applied to efficiently assess habitats on a regional scale for individual species of concern, such as sage-grouse, in concert with regional habitat assessment of a comprehensive set of species associated with the sagebrush ecosystem. These methods are urgently needed by the USDI Bureau of Land Management (BLM), USDA Forest Service (FS), and USDI Fish and Wildlife Service (FWS) to gain regional knowledge for effective conservation and restoration strategies, owing to the high likelihood of regional extirpation for many sagebrush-associated species (Raphael et al. 2001).

Distribution and Abundance of Sagebrush at Regional Scales

We define the sagebrush ecosystem (see Glossary [Appendix I] for details) as arid and semi-arid, sagebrush-dominated lands in the western United States

and Canada that encompass the approx- imate boundaries of the historical range of greater sage-grouse and Gunnison sage-grouse (Schroeder et al. 3004) (Fig. I. 1). A cornprehensive estimate of sagebrush abundance and distribution within these boundaries recently be- came possible with the establishment of a continuous coverage map of sagebrush cover types (referred to hereaftere as the 90-m land cover map; Comer et al. 2002). Ten sagebrush cover types, spanning 19 ecoregions in the western United States, were identified in the establishment of the map (Table 1.1). These 10 cover types were those that could be mapped with a pixel (grid cell) resolution of 90-m X 90-m (Comer et al. 2002). Reid et al. (2002) describe the recently revised classification of sagebrush alliances and associations that define and support the vegetation classification system used to establish the 90- rn land cover map.

Estimates derived from the land cover map provide a cornprehensive portrayal of sagebrush abundance and distribution, particularly when estimates are summarized to large ecological spatial extents like the ecoregions delineat- ed by The Nature Conservancy (TNC) (Fig. 1 . I) . These estimates show that the distribution of sagebrush in the western United States is vast, encompassing parts of 19 ecoregions and millions of ha (Table I .I ; Figs. 1 . I , 2.1). Sage- brush, however, is concentrated in 3 ecoregions-Columbia Plateau, Great Basin, and Wyoming Basins-which together support 70% of the total area of sagebrush cover types currently present in the United States (Table I .I , Fig. 2.1). The Columbia Plateau and Great Basin Ecoregions, in particular, support >50% of all remaining sagebrush, with extensive concentrations in northern Nevada, southeastern Oregon, and southwestern Idaho (Table 1.1 ; Figs. 1.1, 2.1). Extensive and large concen-


trations of sagebrush also occur throughout Wyoming, encompassing the Wyoming Basins Ecoregion and the southern portion of the Northern Great Plains Steppe Ecoregion.

Miller and Eddleman (2000) described the ecology of the sagebrush ecosystem, with particular emphasis on the vegetation ecology within floristic provinces. Other comprehensive descriptions of the sagebrush ecosystem include West (1988) and Connelly et al. (2004).

Chapter Objectives

concern in the Great Basin Ecoregion of California, Nevada, and Utah (Chapters 2-8). Our methods and their application are designed to help guide conservation and restoration planning for sagebrush- associated species on federal lands in the sagebrush ecosystem.

Our methods also are intended to complement and support related, ongoing work for sagebrush habitats and associated species. Examples include the Great Basin Restoration Initiative led by BLM (USPI Bureau of Land Marrage- ment 1999, 2000a); ecoregional assessments by TNC (e.g., Groves et al. 2000, 2002; Freilich et al. 2001; Nachlinger et

In response to the urgent need to con- "1. 2001; Neely et al- 2001; Noss et ale serve and restore habitats at regional 2001); recent assessments and strategies scales in the sagebrush ecosystem, our for Sage-grOuse populations and habitats

objectives were to (1) identify regional (e.g-, Neel 19997 Canadian Sage

assessment methods that can be used ef- Team 2001 , Connelly et ficiently and credibly to evaluate con- 2004- USPI Bureau of Land

ditions for a comprehensive set of spe- rnent 2004, Hagen 2005); ongoing re- ties of concern in the sagebrush ecoregional assessments in the sagebrush

gions, with emphasis on federal lands ecosystem (Rowland et al. 2005); and

and the needs of federal land managers; myriad local assessments and land use

(2) describe methods for evaluating planning activities now underway by

threats to persistence of sagebrush hab- BLM, FS, and state agencies throughout

itats and species; (3) develop methods the sagebrush ecosystem.

by which trade-offs between the needs The methods described here, and examples of their implementation provid- of individual species versus a compre- ed in our assessment chapters that fol-

hensive set of species can be addressed low (Chapters 2-8), use spatial layers systematically and defensibly at region- available from the SAGEMAP Project

for land planning; (4) dem- [http wr.usgs. gov]. The onstrate the use of regional assessment SAGEMAP Project, developed by the methods with spatia1 data currently U. S Geological Survey -Biological Re- available as continuous coverages sources ~ i ~ ~ ~ i l i ~ ~ in partnership with across all sagebrush ecoregions (Figs. the BLM, serves as a repository for spa- 1.1, 1 -2); and ( 5 ) provide guidance re- tial data that occur within and near the garding use of the methods for effective historical range of sage-grouse. Conse- multi-species planning at regional scales quently, the spatial extent of the sage- as part of ecosystem management. brush ecosystem and spatial data used

As context for our methods, we de- in our work follow that defined and pro- scribe examples of multi-species re- vided by the SAGEMAP Project. gional assessments recently completed for species of concern in other, non- EXAMPLES OF MULTI-SPECIES sagebrush ecosystems. We also illus- REGIONAL LWSE~WV~ENTS trate the application of our methods in A regional assessment, as defined a regional assessment for species of here, is a spatial or temporal analysis of

METHODS OF ASSESSMEKT-W.Y~CIIIZ et nl. 11

environmental conditions for a comprehensive set of species of conservation concern, as conducted for areas typically >200.000 ha. and often encompassing areas > I million ha. A number of multi-species regional assessments have been completed recently (Johnson et al. 1999). Four case examples that provide particularly high utility for management are described below as context for our methods.

Forest Ecosystem Management Assessment in the Pacific Northwest

This assessment (Thomas et al. 1993a, b) provided information on ecological, economic, and social systems for species of concern within the range of the northern spotted owl, excluding British Columbia. Approximately 1 0.1 million ha of federal land within Wash- ington, Oregon and California were included in the assessment, which evaluated both current conditions and future conditions projected under 10 management scenarios. The focus of the assessment was late successional and old growth forests and associated species.

Effects of management were projected for over 1,100 species and species groups including terrestrial and aquatic vertebrates, vascular plants, fungi, bryo- phytes, lichens, and 1 I functional groups of arthropods. Fourteen expert C

panels estimated these effects, engaging >70 species experts in the analysis.

Assessment of effects on arthropods was particularly challenging because of the large number of species (estimated at >7,000), the percentage of total species that have yet to be described (estimated at 20-30%), the lack of ade- quate surveys, and the lack of information on specific habitat associations. Because of the complexity involved, the experts who assessed the arthropods ag- gregated them into 11 functional groups based on their ecological roles: (I)

coarse wood chewers; (2) litter and soil dwellers; ( 3 ) understory and forest gap herbivores; (4) canopy herbivores: ( 5 ) epizootic forest species; (6) aquatic herbivores; (7) aquatic detritivores; (8) aquatic predators; (9) pollinators; (1 0) riparian herbivores; and (1 1) riparian predators.

Assessments of arthropods focused on the likelihood that habitat capable of supporting the functional groups would be maintained rather than on the status of individual species. Thus, the approach emphasized ecosystem function rather than species viability. This approach was considered necessary and appropriate because of the lack of information available on individual species, and because of the importance of arthropods to ecological functions within the late successional and old growth forests in the Pacific Northwest.

Source Habitats Assessment in the Interior Columbia Basin

Analysis of habitat trends for terrestrial vertebrates of conservation concern (Wisdom et al. 2000) was conducted as part of the Interior Columbia Basin Ecosystem Management Project (IC- BEMP). The purpose of ICBEMP was to develop an ecosystem-based strategy for all FS and BLM lands within the Interior Columbia Basin. The assessment area includes 58.7 million ha in 8 northwestern states, and 53% of the area is public land administered by the FS or BLM.

Ninety-one terrestrial vertebrate species of conservation focus were identified using several criteria. These criteria included projected trends in habitat conditions (Lehmkuhl et al. 1997), Biodi- versity Network global rankings (Mas- ter 199 I), and expert panel determina- tions. The identified species were placed into groups based on similarity of their macro-habitat associations.


Grouping was accomplished with ag- glomerative hierarchical cluster analysis (SAS Institute, Inc. 1989), using a habitat association matrix that contained 154 combinations of vegetation cover types and structural stages. The habitat associations were developed from published literature and expert knowledge. The clustering algorithm used pair wise similarities in source habitats between species. Experts reviewed the initial groups and made recommendations for refining group memberships and the number of groups to bring forward for analysis. The 91 species were subse- quently placed into 40 groups that were further combined into 1 2 "families" of groups.

The species, groups, and families were used in a hierarchical assessment of habitat trends at increasingly broader scales. Objectives of this assessment were to (1) identify broad-scale, robust patterns of habitat change that affect multiple species in a similar manner; (2) identify broad-scale management strategies that address the needs of many species efficiently, accurately, and holistically; (3) determine how well an evaluation of a group of species or a set of multiple groups of species provides for individual species within the groups; and (4) consider habitat dynamics at multiple spatial scales and across time to facilitate the design and implementation of spatially- and temporally-explicit management strategies.

The degree to which a given set of management strategies met species needs was quantified by evaluating the efficacy of the management strategies at all 3 levels: species, group, and family. For example, habitat trends at all 3 levels were estimated and discussed in terms of management implications. In addition, the correlation of habitat trend between each pair of species within each group and family was calculated to illustrate the degree to which group

trends represented the trends of individual species.

Habitat trends estimated under the hierarchical approach were used to devef- op broad-scale management strategies as part of the Supplemental Environ- mental Impact Statement for the Interior Columbia Basin Ecosystem Manage- ment Project (LTSDA Forest Service and USDI Bureau of Land Management 2000). Management strategies were developed for families or groups that were shown to have undergone the greatest reduction in habitat since pre-European settlement. The strategies were evaluated using focal species selected from the families of species.

Southern California Mountains and FoothilIs Assessment

This assessment provides detailed information about current conditions and trends for ecological systems and species in southern California (Stephenson and Calcarone 1999). The objective was to provide information to land managers for use in developing broad land management goals and priorities, while also setting the context for decisions specific to smaller geographic areas. The analysis area included 2.5 million ha in southern California, of which 64% is public land, including 1.4- million ha on 4 National Forests. The assessment used a combination of habitat-based ecological groupings and assessment of individual species. Information was compiled from published literature, field surveys, unpublished reports, mapping efforts, satellite imagery, agency files, and expert opinion. The assessment included:

Trend in the composition, structure, and extent of ecological communities in the planning area;

* The natural and human processes that are driving landscape change: Species and communities at risk and

METHODS OF ASSESSMENT-\Y~S~CIY~Z et ul. 13

the factors affecting their long-term viability; and

* Possible methods and strategies for sustaining species viability and ecological integrity.

The assessment identified 12 rare plant communities and selected 184 animals and 255 plants as "emphasis species." These species met one or more of the following criteria:

I . Listed or proposed as threatened or endangered (federal or state);

2. Former FWS Candidate (C1 or C2); 3. FS sensitive species (Region 5); 4. California Species of Special Con-

cern; 5. Riparian obligate species of concern

(as defined by California Partners in Flight);

6. Any species determined to have viability concerns at a local level;

7. Major game species; or 8. Species of particular public interest

(e.g., mountain lion).

The conservation potential and needs of the emphasis species on public lands were summarized by placing each species in 1 of 3 categories: (1) Minimal Influence (minimal ability to conserve on public lands within the assessment area); (2) Landscape Level (species best conserved through habitat or landscape- level management); or (3) Site Specific (species requires site-specific conservation attention). Of the 184 animal and 255 plant emphasis species, 28 and 23, respectively, occurred incidentally on public lands, and management of those lands was estimated to have little effect (Minimal Influence species). Of the remaining emphasis species, I 14 animals and 141 plants can be adequately addressed through landscape-scale habitat management (Landscape Level species), while 42 animals and 91 plants were recommended as needing species- specific conservation measures (Site

Specific species). Thus, through a habitat-based grouping approach, the assessment revealed where broad-scale habitat measures could be efficiently applied, and also highlighted the species needing individual conservation planning.

The Nature Conservancy Assessment of the Great Basin

This assessment provided an extensive and detailed compilation of the diversity, richness, and status of native species, natural communities, and ecological systems present within the Great Basin Ecoregion of California, Nevada, and Utah (Nachlinger et al. 2001). The goal of the assessment was "to develop a portfolio of conservation areas that fully represent the natural communities and species characteristic of the Great Basin in viable populations and landscapes within the least area possible" (Nachlinger et al. 2001 :5). The massive ecological compilation contained in the assessment is complemented with a detailed set of conservation targets and goals, identification of >350 conservation areas, or "portfolio sites," to meet targets and goals, and supporting maps of environmental quality in relation to human activities and threats.

Results were expressed at spatial extents of the ecoregion, for 6 sections of the ecoregion that differed strongly in ecological status and potential, and for individual sites. Conservation goals u7ere established for each portfolio site, based on each site's global distribution, rarity, and vulnerability to loss and degradation from human activities. More- over, the assessment contained an ex- haustive compilation of >2,800 occurrences of targeted species. These occurrences were overlaid with information about environmental quality and threats to the environment for the portfolio sites.

14 PART I: ASSESSING TI-IREATS

The portfolio sites varied in size. with 94 sites classified as "functional landscape scales" (areas large enough and of sufficient quality to contain many or most of the essential pieces of an effectively functioning landscape). The other 264 portfolio sites were classified as smaller functional sites. A comprehensive list of environmental threats was compiled and discussed in relation to the portfolio sites and at a variety of spatial extents. Results from identifying the portfolio sites, and the associated ecological basis for site selection, provide the foundation for conservation planning and land management in the Great Basin Ecoregion by The Nature Conservancy with its many federal, state, and private partners.

WHY CONDUCT MULTI-SPECIES REGIONAL ASSESSMENTS IN THE SAGEBRUSH ECOSYSTEM?

The need for regional assessment of sagebrush habitats for a comprehensive set of species of concern is based on 5 points:

1. Habitats and populations of sagebrush-associated species continue to decline across vast areas. The pros- pect of continued habitat and population declines for sagebrush-associated species across extensive areas (Knick and Rotenberry 1999, 2000; Paige and Rit- ter 1999; Wisdom et al. 2000; Dobkin and Sauder 2004), and the associated high risk of large-scale extirpation events for these species (Raphael et al. 2001), point to the urgent need for regional assessments. Regional assessments can capture these "top-down" processes that manifest over vast areas, allowing for greater management effi- ciencies.

2. The number of sagebrush-associated species of concern is daunting, and many of these species have extensive ranges compatible with regional

assessments. Hundreds of species of conservation concern are associated with sagebrush habitats (Appendix 2). illustrating the need for holistic assessment methods that can efficiently serve management needs of all species. In addition, many of these species have ranges that encompass millions of ha and span multiple states and administrative units. Habitat conditions across these wide ranges cannot be managed effectively or efficiently if conditions within each BLM Field Office or National For- est are assessed and managed indepen- dently. Evaluation of habitat at broad scales provides information to be considered in development of regional management strategies, such as the Great Basin Restoration Initiative (USDI Bureau of Land Management 1999, 2000~) . Such strategies can serve as an "umbrella," under which local land use plans can evolve in a consistent and efficient manner, while still accom- modating local needs and conditions.

3. Threats to sagebrush habitats are regional in scale. Invasion by exotic plants, ineffective suppression of undesirable wildfires, road development and use, energy development, and other detrimental processes in sagebrush habitats are not local, isolated events. In- stead, the processes that pose threats to sagebrush habitats occur across large areas, with cumulative effects that pose high risks to persistence of sagebrush- associated species. Pervasive, regional threats to habitats are best addressed at regional scales, which allow the cumulative effects of a variety of threats to be addressed consistently and holistically across large areas.

4. Regional knowledge facilitates development of consistent, efficient, and credible regional management strategies for a comprehensive set of species. If threats to sagebrush habitats are regional in scale, then regional knowledge of these threats and the un-

METHODS OF ASSESSMENTT-?V~S~OI~ et a/. 15

derlying processes is needed to develop vation and restoration of sagebrush hab- regional strategies that can address itats, described later. these problems efficiently, consistently, and credibly across large areas. The al- FOCCTS REGIONAL ternative is local plans that address local SAGEBRUSH ASSESSMENTS ON problems with local solutions, but by FEDERAL LANDS? definition are not designed to address threats to habitats consistently across Managers of federal land are unique- multiple planning areas in an ecoregion. ly positioned and responsible for In particular, there is an unmet need for aEement of habitats for sagebrush-as- regional assessments that address, in a ~ociated species for 2 main reasons: holistic manner, the conditions and l*Mo~tremainingsagebrushhab- threats associated with a comprehensive itats Occur On lands, and set of species associated with sagebrush habitat loss and degradation On these habitats. Such an approach was devel- lands are substantial and accelerat- oped recently as part of a regional hab- i"g*As stated earlier, thesagebrusheco-

itat network for sagebrush-associated system bas been characterized as criti-

species in the Interior Northwest (Wis- cally endangered (Noss et al. 1995).

dom et al. 2002~). This type of large- Nearly 70% of the ecosystem is man-

scale, multi-species approach would be aged by state or federal agencies, with

useful as part of regional assessments almost 65% under federal control

for conservation and restoration plan- (Knick et al. 2003) (Table 1.2, Fig. 1.2). The BLM and FS administer most of

ning in all sagebrush ecoregions. the sagebrush under federal manage- '* Regiona1 provides es- ment, managing 52% and *%, respec-

sential context for local land use plan- tively, of all existing sagebrush. Sub- ning. Land use plans for individual Na- stantially less area of remaining sage- tional Forests or BLM Field Offices de- brush is in private ownership (Table pend on defensible justification as to 1.3). These patterns emphasize the key

particular management issues are role of federal land management in the of interest and focus. Local needs and conservation of biological diversity in issues are obvious topics for planning the sagebrush ecosystem and adjacent within a National Forest os BLM Field ecosystems (Stein et al. 1995, Knick et Office. The addition of regional know]- a1. 2003). While historically most losses edge, however, provides essential con- of sagebrush habitat occurred on non- text for, and complements, local plan- federal lands, such losses appear to be ning issues- Neither regional knowledge accelerating on federal lands, owing to nor local knowledge is independent in a variety of detrimental processes and terms of land use planning. That is, re- land uses (Hemstrom et al. 2002, Wis- gional knowledge can identify the dom- dom et a]. 2002~) . inant spatial and temporal patterns that 2. Federal land managers have le- manifest consistently across large areas, gal responsibilities for effective man- referred to as "top-down" processes agement of habitats for sagebrush-as- (Peterson and Parker 1998). These pat- sociated species of conservation con- terns are in contrast to the finer patterns cern. Responsibilities of federal agen- unique to local areas and conditions, re- cies to conserve and restore species of fei-red to as "bottom-up" processes. conservation concern and their habitats Both sets of processes (Figs. 1.3, 1.4) are well defined in legislation and pol- must be addressed for effective conser- icy. The Federal Land Policy and Man-

I6 PART I: ASSESSING THREATS

Spatial Extent: Sire and type of

mapping boundaries

Spatial Grain: Pixel size and associated resolution for mapping

spatial extents

Subwatershed

Coarse Moderate Fine Habitat 1 Habitat 2

Habitat 3

Classified as Classified as Classified as Habitat 3 Habitat 2 Habitat I

FIGURE 1.3. Illustration of the concepts of spatial extent and spatial grain, which compose the spatial scale of a regional assessment. Spatial extent refers to the size and type of boundaries selected; in this case, hydrologic extents are used. Spatial grain refers to the size and type of mapping unit used to estimate vegetation or other environmental features. In this case, pixels are used, ranging from coarse to fine grains, which in turn affect the resolution of associated habitat estimates. See text for additional discussion of these concepts.

agement Act (FLPMA) directs the BLM to provide habitat for fish and wildlife and to protect the quality of ecological values. BLM has a variety of policies,

Multiscale Approaches

FIGURE 1.4. Illustration of "top-down" versus "bottom-up" processes in relation to ecological and administrative scales of spatial analysis and land use planning.

based on FLPMA, that are designed to conserve federal- and state-listed species and their habitats, and to develop and implement effective restoration strategies for such species (LJSDI Bu- reau of Land Management and Office of the Solicitor 200 1 ). Similarly, the Na- tional Forest Management Act (NFMA) directs the FS to ". . . provide for diversity of plant and animal communities based on the suitability and capability of the specific land area in order to meet overall multiple-use objectives . . ." Sirnilar direction is provided to the FWS in managing National Wildlife Refuges: "In administering the [Nation- al Wildlife Refuge] System, the Secre- tary shall . . . ensure that the biological

METHODS OF ASSESSMENT-Mfisdcj~n et al. 17

TABLE 1.2. Area and percentage of the sagebrush ecosystem in the western United Statei by ownership and management agency. Estimates are from the 90-m land cover map developed by Comer et a]. (2002). available from the SAGEMAP Project [http://sagemap.wr.usgs.govf

Area of \agebrush Percentage eeocystem (\q. krn) of total

Public resource landslUSD1 Bureau of Land Management Military reservationlUS Department of Defense US Department of Energy Wildlife refugesfUSD1 Fish and Wildlife Service National ForestfUSDA Forest Service National parks and monumentslUSD1 National Park Service Other federal management State managernent Native American reservations Private Other

Total

integrity, diversity, and environmental health of the System are maintained . . ." (National Wildlife Refuge System Administration Act of 1966 as amended by the National Wildlife Refuge System Improvement Act of 1997, 16 U.S.C. 668dd-668ee). The FWS also adminis- ters the U.S. Endangered Species Act, whose premise is based on preemptive management designed to prevent federal listings of species, a concept directly pertinent to conservation and restoration of habitats for species of concern in the sagebrush ecosystem (Ap- pendix 2). The U.S. Department of Defense (DOD) also has legal and policy direction to balance military activities on DOD lands with biological diversity (U.S. Department of Defense 1996, 2000).

SETTING GOALS AND OBJECTIVES IN THE CONTEXT OF SPATIAL AND TEMPORAL SCALES OF ASSESSMENT

alized. An example of an over-arching goal for a regional assessment of habitats for species of concern is to gain regional knowledge about these species' habitats for effective use in improving the probability of habitat and population persistence.

When defining goals and objectives, consideration of spatial scale is essential (Maurer 2002). Spatial scale is characterized by extent, grain, and accuracy (Peterson and Parker 1998, Turner et al. 2001) (Fig. 1.3). Extent refers to the size and boundaries of the area under evaluation. For example, the spatial extent of an ecoregion follows ecological boundaries and encompasses millions of ha, in contrast to an individual patch that may occupy <1 ha. Estimates of habitat characteristics over large spatial extents often reveal different patterns than those derived from smaller spatial extents. Neither estimate is incorrect. Instead, patterns revealed at different extents are complementary and infor-

An effective regional assessment re- mative for multi-scale planning. quires clear goals and objectives; they Grain is the resolution at which spa- are critical to the process. Without ex- tial patterns are measured (Fig. 1.3). plicit goals and objectives, direction for Resolution of spatial data affects how the regional assessment will be unclear, well the true conditions are estimated and its intended benefits may not be re- for a given size and type of mapping

PART I: ASSESSING THREATS

o m m w d - o o o m a m - w a m m o * N m m r n - + m - + - * m m m - i W w c B o

pCi cs m-mr ;=? . 00_ c;fiC,C)h*ecmc?c?a'a?'?e% 3: Cvt 'a CO g C W C h v ~ b m r ' Q i x ;

r n G 0 P - i coma' rn -- q- 'a moom

METHODS OF: ASSESSMENT-Miishrn er al. 19

unit. Typical mapping units consist of pixels or polygons. Pixels are a grid of cells, such as squares or hexagons, into which the spatial extent is subdivided. By contrast, polygons consist of vector boundaries of irregular shapes that sub- divide the analysis area. Spatial grain is influenced strongly by the minimum size of pixels or polygons used to estimate habitat characteristics. For example, the resolution associated with a 30- m X 30-m pixel is substantially higher than that associated with a 1000-m X 1000-m pixel, with estimates that are lower in bias (i.e., closer to the true value) and higher in precision (i.e., produce more consistent results).

Consequently, spatial grain affects the accuracy of estimates made over a specified spatial extent, with accuracy defined as the combination of bias and precision associated with spatial estimates for a given time and place. In spatial evaluations of accuracy, measures of bias often are referred to as classification accuracy; this form of accuracy is typically expressed as the percentage of times a spatial estimate correctly identifies the true attribute. For example, 70% classification accuracy might refer to the percentage of times that a particular type of sagebrush habitat was correctly mapped, given a specified spatial grain and extent.

The pixels in Fig. 1.3 illustrate the differences in accuracy of habitat estimates resulting from differences in spatial grain. For a given spatial extent, the coarser the grain, the lower the accuracy. For example, although the spatial extent covered by the coarse pixel is dominated by Habitat 3, it contains appreciable area of Habitats I and 2. The coarse pixel is classified, however, as only one habitat type (Habitat 3), owing to Habitat 3 being the dominant type. In this instance, appreciable amounts of Habitats 1 and 2 are not classified because of the coarse spatial grain and

therefore are not included in the estimate, representing a reduction in accuracy. By contrast, if one were to use fine-grained pixels to classify the same sized area as the coarse pixel (compare habitats across the coarse, moderate, and fine pixels in Fig. 1.3), the fine pixels would classify the area as a combination of Habitats 1, 2, and 3, with Hab- itat 3 as most abundant, and Habitat I as least abundant. The result would a more accurate portrayal of the habitat types within that spatial extent of interest.

Accuracy of spatial estimates also is affected by spatial extent. For example, Hann et al. (1997) and Wisdom et al. (2000) summarized the accuracy of regional assessments based on spatial data estimated at coarse resolution (1000-m X 1000-m pixels) in the Interior Colum- bia Basin. They found that vegetation data were of acceptable accuracy to meet assessment goals when summarized at the largest spatial extents, such as the basin (58 million ha), ecological province (>I million ha), or subbasin (>200,000 ha). By contrast, vegetation data estimated for smaller spatial extents, such as for a watershed (20,000 ha) or subwatershed (8,000 ha), were not sufficiently accurate unless data were summarized for large groups of watersheds or subwatersheds.

The same concepts of extent, grain, and accuracy-as discussed above for spatial scale-apply to consideration of temporal scale. Temporal extent refers to the time period over which an assessment is done (in contrast to the area and type of boundaries that define spatial extent). Large temporal extent therefore refers to long time periods. Temporal grain refers to how frequently the estimations are made to assess conditions. Estimations made over more narrow time periods therefore represent a higher temporal grain.

As with spatial scale, specifying the

20 PART I: ASSESSIKG THREATS

temporal scale is vital in regional assessments: that is, whether past or fm- ture changes will be considered, over what time periods such changes will be estimated (temporal extent), how often changes will be estimated or projected (temporal grain), and how different methods of estimating conditions at different time periods will be reconciled (Noon and Dale 2002). Different methods used to obtain habitat estimates for each time period affect the spatial grain and accuracy at each point in time, in turn affecting the estimates of habitat change over time. As with spatial scale, the objectives of a temporal analysis determine the extent and accuracy of habitat estimates that are required.

ANALYTICAL STEPS TO MEET OBJECTIVES

Suggested Methods for Spatial Analysis in Sagebrush Ecoregions

The following steps are intended for application at large spatial extents, such as ecoregions, as well as ecological provinces, subbasins, or other large areas (>200,000 ha) nested within each ecoregion (Fig. 1.3). We consider these steps to be the minimal methods needed to conduct a regional assessment for a comprehensive set of species of concern. That is, these steps are a starting point, to which many complementary analyses-such as evaluation of habitat configuration (e.g., patch size, fragmentation, and connectivity)-can be added. Examples of additional, complementary analyses are described later (see Other Metlzods f i r Spatial and Tefnpof-al Analysis).

Our analytical steps are not necessar- ily linear or sequential. For example, the second step, Irfelztzfi Species of Conservation Concern, requires knowledge of species' ranges, which is part of step 3, Delirzeute Species Rnlzges. Step 2 requires simple knowledge of whether

the range of a given species in the ecoregion is large enough (>200,000 ha) for the species to be included in the regional assessment. By contrast, step 3 requires delineation of the specific boundaries of species' occurrence, so that habitats for each species can be assessed within its respective range. Ac- cordingly, the chronology and details of the following steps can be modified and adapted to meet the specific needs of a given regional assessment.

1. Identify the Ecoregion and As- sociated Spatial Extents-Ecoregions within the sagebrush ecosystem have been identified and mapped by TNC (Groves et al. 2000, 2002) (Tables 1.1, 1.2, 1.3; Figs. 1.1, 1.2, 2.1), as adapted from Bailey (1 995~2, b). Ecoregions are of the appropriate size, combined with their ecological boundaries, to make them ideally suited for regional assessment of sagebrush habitats.

The reasons for selecting a given ecoregion for regional assessment can be varied and complex, and should be stated clearly. Reasons might include concerns about habitat loss from specific threats, such as energy development (Braun et al. 2002, Weller et al. 2002, Rowland et al. 2005). Alternatively, interest in the status of habitats for high- profile species, such as pygmy rabbit or greater sage-grouse, may drive the selection of an ecoregion. Moreover, knowledge of habitat conditions for such high-profile species in relation to those for a larger set of sagebrush-associated species may be of keen interest in selecting an ecoregion. Finally, management opportunities may be enhanced by large amounts of sagebrush in federal owrnership (Table ! .3), which allows for management of large areas in a consistent manner, and for public par- ticipation in management improvements over such large areas.

Once the ecoregion is chosen, the associated spatial extents of interest can

METHODS OF ASSESSkIENT-1Yiirdc~~n et nl.

Species of Conservation Concern in the Sagebrush Ecosystem

Vascular Inwrtebrates Arnphtbians Reptiles Birds M a m l s Plants

Taxonomic Group

FIGURE 1.5. Percentage of species of conservation concern associated with the sagebrush ecosystem, summarized by taxonomic groups. Over 350 species of conservation concern, defined as species with rare or declining habitats or populations, were identified for the sagebrush ecosystem (Appendix 2).

be identified for further assessment. For example, ecoregions follow ecological boundaries, but management typically follows administrative boundaries, such as those of state and field offices of the BLM (Figs. 1.4, 2.3). Consequently, results can also be assessed for these large administrative extents that are nested within an ecoregion, or that overlap substantially with ecoregion boundaries. Accordingly, we assessed sagebrush habitats for the Great Basin Ecoregion, but also summarized results statewide for Nevada (Chapters 2-8), and for BLM Field Offices within Nevada (Ap- pendix 7).

Assessments can include other spatial extents beyond ecological and administrative boundaries. Hydrologic extents, such as watersheds or subbasins, often are used for assessment and management planning (Wisdom et al. 2000, 2002~). The Great I3 asin Restoration Initiative, for example, focuses on restoration planning by watershed within the Initiative's boundaries, which encompass large portions of the Great Ba- sin and Columbia Plateau Ecoregions (USDI Bureau of Land Management

1999). See Step 9, Surnrnarize Results for Species and Groups at Desired Spa- tial Extents, for additional details about summarizing results for regional assessments at a variety of large spatial extents.

2. Identify Species of Conservatiorz Concern for Assessment irz the Ecore- gion-We identified >350 species of conservation concern that occupy the sagebrush ecosystem (Fig. 1.5, Appen- dix 2). These species constitute a comprehensive master list of species that are associated with sagebrush habitats, and whose populations or habitats are considered rare or declining, based on current data. This master list can be used to identify the species of concern for regional assessment in a given sagebrush ecoregion. We suggest an inclusive approach for selecting species. An inclusive approach ensures that all potential species of concern are identified for a given assessment area. In turn, selection of a comprehensive set of species of concern ensures that a wider range of associated habitats are assessed and ultimately considered in research and management.


Consult master list of 1

FIGURE 1.6. Criteria and decision diagram for selecting species of conservation concern for multi-species assessment within an ecoregion.

*

Step 2

through fine-scale,

with macrohabitat - mapped accurately with coarse-scale spatial

NO

data?

YES

Identification of species for regional assessment involves a multi-step screening process (Fig. 1.6). We designed these steps in a manner similar to the concepts and considerations outlined recently by Coppollilo et al. (2004). Under our process, the initial steps are (I) consult the master list of species of conservation concern that exist in the sagebrush ecosystem (Appen- dix 2); and (2) identify those species on the master list that are ranked SI , S2, S3, or S4 by NatureServe (NatureServe

Step

2005) for any state in the assessment area.

Species with rankings of S I , S2, S3, or S4 are screened further by determin- ing whether their geographic ranges encompass at least 596, and at least 200,000 ha, of the assessrnent area (Fig. 1.6, Step 3). Any species whose range in the assessment area composes 5200,000 ha, or makes up (-5% of the assessment area, is dropped, owing to uncertainties about the accuracy of mapping vegetation and other environ-

Compare list to other compilations (e.g., state sensitive species lists, TMC conservation targets) for the assessment area and add sagebrush- associated species as appropriate (repeat Steps 3 and 4).

be added or dropped; list is finalized.

METHODS OF ASSESSMENT-?Viirdc)7n et ccl. 2 3

FIGURE 1.7. Examples of 4 species' ranges: (1) large, interacting; (2) large, disjunct; ( 3 ) small, isolated; and (4) small, fragmented. In these examples, the range of a species is defined as the outer boundaries of a species' occurrence, or a polygon of occurrence, for a given population. Ranges identified as large, interacting (1 large population within 1 large polygon) and large, disjunct (two large but spatially separated populations) would be suitable for regional assessment. Ranges identified as small, isolated ( I restricted population) or small, fragmented (2 or rnore restricted populations) would not be suitable for regional assessment if such ranges are 5200,000 hectares. Once the species' range is mapped, environmental conditions for the species within its range are evaluated as part of the regional assessment.

mental conditions in the small areas occupied by such species (Figs. 1.3, 1.7).

Range maps are available from a variety of sources (e.g., Opler et al. 1995, Wilson and Ruff 1999; see Chapter 5 for details) to determine whether range size is sufficient to include each species of concern in the regional assessment. (see the following section, Delineate Species Ranges, for definitions and methods for mapping a species' range.) Importantly, the availability of rnore accurate spatial data in the future will allow habitats for species with smaller ranges to be mapped adequately in re-

lation to goals and objectives of a regional assessment.

The species that remain after screening for range size are then evaluated as to whether they are associated with macro-habitats that can be accurately mapped with coarse spatial data (i.e., the 90-rn land cover map described by Comer et al. [20@2], described in detail in Chapter 3) currently used for ecoregion assessments (Step 4). Species associated with micro-habitats (defined in Appendix l), which cannot be mapped accurately with coarse spatial data, are dropped.


Species associations with macro- ver- sus micro-habitats can be evaluated by researching the species' life history and associated habitat requirements: if habitats for the species can be mapped at coarse resolution and summarized over large spatial extents, the species is suitable for regional assessment. We define coarse resolution as a 90-m X 90-m pixel size or larger, as currently used for cover type mapping across the sagebrush ecosystem. Species that respond prirnarily to micro-habitats must be evaluated at local scales, and are not suitable for regional assessment (Fig. 1.6, Step 4). For example, the availability of local roost sites, a critical re- quirement for many species of bats, cannot be detected or mapped at regional scales. Similarly, many species are local endemics, requiring knowledge of site-specific conditions in relatively small areas. Habitats for such species must be assessed at local scales that allow accurate mapping of these fine- scale features.

The fifth step is to consult sources beyond the major ones identified in our process (Chapter 5, Appendix 2), to confirm whether additional species should be considered for regional assessment (Fig. 1.6, Step 5). Examples of such lists include conservation targets identified by TNC for conservation planning within ecoregions (e.g., Nach- linger et al. 2001), and species identified as sensitive or having other designations of special status by state or federal agencies in the ecoregion.

The final step is for species experts to review and refine the list (Fig. 1.6, Step 6). This review helps ensure that all species of concern are identified, that species are correctly targeted for regional versus local assessment, and that existing knowledge about habitats and populations of each species is summarized correctly and sufficiently as part of the assessment.

3. Delineate Species Raizges- Knowledge of the geographic range of each species is needed because differences among ranges for many species can result in differences in habitat status and response to management. We define a species' range as the polygon or polygons that encompass the outer boundaries of a species' geographic occurrence within an ecoregion or other area used for regional assessment. This definition is equivalent to that provided by Gaston (2003:72), who defined a geographic range as the "outer most limits to the occurrence of a species" in his synthesis on the subject. Gaston (2003: 72) specifically referred to this definition as the spatial "extent of occurrence." Under this definition, a species' range can consist of 1 or more polygons, with each polygon presumably encompassing an interacting population (Fig. 1.7). Species with ranges com- posed of 2 or more polygons are assumed to have disjunct populations (Fig. 1.7), presumably with little or no interaction of populations across polygons.

Importantly, our definition of a species' range says nothing about the spatial structure of the population inside each polygon, except to assume that the polygon encompasses an interacting population. Our definition therefore contrasts with distribution maps of populations, often generated from documented occurrences of a species, but which nearly always are based on in- complete data that can lead to false conclusions about the patchiness of the species' range. Gaston (2003:72) referred to this latter description of geographic range, based on occurrence data, as "the area of occupancy of a species." Our definition also differs strongly from maps of predicted distribution of habitats for species, such as those produced by GAP analysis (Scott et al. 1993).

Dobkin and Sauder (2004) warned

METHODS OF ASSESSMENT-fYiscto~zz et al. 2 5

that range maps, using our definition of the outer boundaries of a species occurrence, overestimate the actual areas where a species is found: these authors noted that the true range of a species may consist of a set of isolated populations erroneously mapped as 1 range, but that in fact are a set of isolated ranges. Gaston (2003) also noted that maps of a species "area of occupancy" are smaller than the species' geographic limits, because a species typically does not occupy all areas within its range.

Gaston also noted, however, that maps of a species area of occupancy can lead to falsely concluding that a species' range is more limited than actually exists. This opposite problem was recently documented for the range of pygmy rabbit in Wyoming. where most of the state had formerly been considered unoccupied by the species. By 1981, the species was reported in Wyoming, a range extension of 240 km and 14-5 km from the closest previously recorded observations in Idaho and Utah, respectively (Campbell et al. 1982). The species has since been recorded in 4 coun- ties in southwestern Wyoming (Garber and Beauchaine 1993).

Unfortunately, for nearly all sagebrush-associated species beyond sage- grouse, exact range boundaries based on spatially explicit knowledge of population structure are either unavailable or highly uncertain. Consequently, it is not possible to map the specific spatial structure of each species' populations as part of regional assessments at the current time, beyond identification of the outer boundaries of occurrence. As a result, current range maps may oves- or under-estimate the true occurrence of species, depending on the degree to which a species' range has been sur- veyed systematically. Importantly, our use of range maps is intended to reduce the area of habitat analysis in the ecoregion to the outer boundaries of the area

where the species has been documented to occur, The result is an area analyzed for a given species that is often much smaller than the ecoregion, and that is centered geographically on the species' documented occurrences.

Four example ranges are shown in Fig. 1.7: (1) large, interacting; (2) large, disjunct; (3) small, isolated; and (4) small, fragmented. For broadly-distributed species with 1 interacting population, the range is depicted as 1 large polygon that encompasses areas of both used and unused habitats. For common species with disjunct populations, range maps reflect the outer extent of individual populations, and the ranges consist of 2 or more separate polygons, representing 2 or more separate populations that have less or no interaction (Fig. 1.7). Locally endemic species or species with small, scattered populations can have ranges expressed as 1 small polygon (1 small, isolated population) or a series of small populations (a set of small, fragmented populations) (Fig. 1.7).

Delineation of each species' range in a regional assessment is a key step because of the above-mentioned spatial differences in habitat conditions, and response to management, that can result from non-overlapping portions of ranges. For example, the range of greater sage-grouse has contracted substantially since historical times (Schroeder et al. 2004); this reduced range contrasts strongly with other sagebrush-associated species, such as the sage sparrow and sagebrush vole (Appendix 6), whose ranges extend over a larger area of the sagebrush ecosystem (Carroll and Gen- oways 1980, Matin and Carlson 1998). Consequently, results of a regional assessment for these 3 species could vary substantially, thus complicating shortcut management approaches like "umbrella species," as proposed for sage- grouse (e.g., Rich and Altman 2001).

26 PART I: ASSES SING THREATS

FIGURE 1.8. Overlap in ranges of 7 vertebrate species considered to be sagebrush obligates or near-obligates: greater sage-grouse, sage thrasher, sage sparrow, vesper sparrow, Brewer's sparrow, Wyoming ground squirrel, and pygmy rabbit. Overlap was summarized by mapping areas in Nevada where ranges of all 7 species overlap versus areas where pro- gressively fewer ranges overlap. Overlap of all 7 species' ranges is restricted to an area within the northern part of the state.

(see Chapter 8 and Appendix 3, Short- cut Approaches to Multi-species Assess- ment.)

An illustration of how differences in species' ranges could affect results of a regional assessment is shown in Fig. 1.8. Here, areas within Nevada are mapped according to the number of species with overlapping ranges, for 7 vertebrate species considered to be sagebrush obligates or near-obligates (greater sage-grouse, sage thrasher, sage sparrow, vesper sparsow, Brewer's sparrow, Wyoming ground squirrel, and pygmy rabbit; Table 7.2). Ranges for all 7 species overlap within a portion of northern

Nevada. but only 2-3 species have ranges that both occur and overlap within a large area of southern Nevada (Fig. 1.8). As a result, each species' response to management, as well as their habitat conditions and trends, will vary geographically.

For most vertebrate species included in a regional assessment, published range maps are available and often can be used without modification, following verification by species' experts to ensure the maps are the most accurate available. Range maps for birds are included in species accounts of The Birds of North America series (Birds of North America, Inc., [http:llwww. birdsofna. org]). Range maps for mammals include those provided by Hall (1981), Zeveloff (1988), Wilson and Ruff (1999), and mammalian species accounts (American Society of Mammalogists, [http:l/ www. science.srnith.eduldepartrnents1 BiologylVHAYSSEN/msi/defaul t . html]). Range maps for reptiles and amphibians in the western United States were recently updated by Stebbins (2003).

Ranges of plants and invertebrates are available from many local sources, such as Albee et al. (19881, Morefield (20011, Opler et al. (1995), and Utah Division of Wildlife Resources (2002). In contrast to vertebrates, however, ranges of plants and invertebrates often are based on fewer locations, and less knowledge, than the range maps derived for vertebrates (see discussion by Bon- net et al. 2002 regarding less knowledge available for plants and invertebrates). Consequently, range maps of plants and invertebrates deserve careful review and refinement by species' experts for use in a regional assessment.

Many of the range maps cited above have been compiled recently in elec- tronic formats by NatureServe (NatureServe 20051, and can be down- loaded at their web site [http:llwww.

METHODS OF ASSESSMENT-Wisdc>v?z et nl. 27

natureserve.org/explorer] . Range maps can then be clipped to the boundaries of the ecoregion under assessment. Habitat assessment for a given species is then conducted within the boundaries of the species' range, as nested within the ecoregion or smaller spatial extents inside the ecoregion.

4. Estinzate Species Habitat Re- quirements-A critical part of any multi-species assessment is to identify the habitats on which each species depends. For this purpose, we define habitat in a specific way, referred to as "source habitats." Wisdom et al. (2000, vol. 1 : 4-5) defined source habitats specifically for the purpose of regional assessments:

"Soccrce habitrlts are those characteristics of macro-vegetation tlzat contribute to stcztioncu-y or increusirzg rates qf population growth for a species irz a specified area unrl time. Source Izabitats contribute to source environments (Pullianz 1988, Pulliam and Danielsovz 1991), which r-ep- resent tlze composite of all environnzental conditions that result in statiorzary or increasirzg sates of population growth for a species irz a specified area and time. Tlze distinction between source habitats and source envir-orzrnents is important ,for un- derstaading a regional habitat evaluation and its limitations. For- example, source habitats for a bird species during the breeding season would include tlzose characteristics of ~nact-o-vegetation tlzat corz- tribute to successfit1 nesting and rearing of young, but nrould not include non-vegetative.factors, such as the eflects of pesticides orz tlzinning qf eggslzells, which also uflect production of young.

Consideration of both vegetcctive avzd rzorz-vegetatitse factors tlzat co~ztribute to populatioitz penristerzce requires an evalu- ution qf soirrce enttiroliznzents, which is he- yond tlze purpose arzd scope qf most 1-e- giorzal assessments qf habitat. As part of the process of' identjfiing and evaluating tvgetation char-acteristics tlzat contribute to stationat-J. or increasirzg population grotvth, ho~tever, we defined and identified source habitats as beirzg distinctly diferent j+or?? lzubitats tlzat are sivnply associated kt-ith species occz-lrz-ence, ~it.hich nzay or may

rzot corztrib~lte to t~iable, l o n g - t e r ~ ~ population yemistelzce. Thut is, in corztr-ctst to soitrcte habitats, tlzose habitats in bvhich species occur cun contribute to eitlzer source or sink envir-onments (P~dEliarn arzd Davzie Eson 1991). Corzseyuently, species occurrence by itself i~zrlicntes little or notli- ing about the cu/?abili~ qf the associated erzvirolzrnent to s1-1p1?ort lorzg-term per-sis- terzce of populatiorzs (Corzroy and Noo~z 1996, Ctmroy et al. 1995). Consequently, data based strictly orz species occurrerzce does not rneet objectives to iclentib those char-acteristics of macro-vegetation that szdpport lorzg-term population per-sistence, which we defined as source habitats."

For regional assessment of sagebrush-associated species, source habitats can be considered, at a minimum, to be the cover types on which each species depends or is thought to depend. This is in contrast to more typical designations of species-habitat associations, defined as habitats in which the species is observed or predicted to occur (e.g., Scott et al. 1993). These latter designations do not consider whether the habitat may be a "source" or a "sink," as discussed above.

Once source habitats are identified for each species, these habitats can be evaluated in terms of their amount, location, and configuration. We define configuration as the arrangement-specifically the patch size, fragmentation, and connectivity-of source habitats in relation to a species' requirements (Glossary, Appendix 1 ). Species responses to landscape measures of habitat configuration are not well known, however, and thus difficult to define in terms of optimal versus suboptimal conditions (e.g., Lee et al. 2002; Sondger- ath and Schroder 2002; Tischendorf and Fahrig 2000a, b). For example, specifying the minimum patch size, distance between such patches, and degree of patch fragmentation in relation to a species' requirements is challenging even for a well-studied species like greater

2 8 PART I: ASSESSING THREATS

TABLE 1.3. An example matrix of source habitats and their abundance (percent area) for greater sage-grouse and loggerhead shrike in the Great Basin Ecoregion (from Table 6.1). Cover types marked with a "X " are source habitats, defined as those characteristics of macro-vegetation that contribute to stationary or increasing rates of population growth for a species in a specified area and time. See text for details

Land cover type"

Percent area of the Great Basin

~coregion'

Sagebrush Wyoming-basin big sagebrush Black sagebrush Low sagebrush Low sagebrush-mountain big sagebrush Low sagebrush-Wyoming big sagebrush Mountain big sagebrush Silver sagebrush Threetip sagebrush

Other Agriculture Ash Alpine Aspen B arren/rock/l ava Bitterbrush Blackbrush Black greasewood Bunchgrass Chaparral Creosote-bursage Desert grassland Dunes Exotic Forbland Forest Juniper Marshlwetland Mesic shrubs Mesquite Mojave mixed shrub Moul~tain mahogany Mountain shrub Pinyon pine Pinyon-juniper Playa Rabbitbrush Riparian Salt desert scrub Saltbush S hadscale Snowlice Spiny hopsage Utah juniper Water

Source habitats

Greater Loggerhead \age-grouse \hrike

METHODS OF ASSESSMENT-Ct'iirdo~n et al. 29

TABLE 1.3. Continued

Land cover type"

Source habitats Percsnt area ctf the Great Basin Greater Loggerhead

~ c o r e g i o n ~ sage-grouse shrike

Western juniper Wet meadow Winterfat Recently burned

~ 3 e e Reid et al. (2002) for descriptions of sagebrush cover types, as developed under an international classification \ystem of mapping dominant vegetation types.

Estimates of percent area occupied by each cover type are based on the 90-rn land cover map developed by Comer et al. (2002), as available from the SAGEMAP Project [http://sagemap.wr.usgs.govJ. See text for details.

sage-grouse (Rowland and Wisdom 2002, Rowland 2004, Aldridge 2005). Consequently, we suggest that these measures of habitat configuration be used to evaluate sagebrush habitats for example species whose responses to these measures are better known, described later (see Additional Methods of Spatial and Temporal Analysis).

Identification of species requirements also includes consideration of non-vegetative factors that affect habitats or populations, or are hypothesized to have a strong effect. Such factors also can be addressed in a regional assessment as a complement to evaluation of source habitats. For example, Raphael et al. (2001) identified and modeled 3 vegetative and 2 non-vegetative factors affecting greater sage-grouse in their regional assessment: habitat quantity, as measured by the area of sagebrush habitat; 2 indices of habitat quality, indi- cating the degree to which native grasses and forbs in the understory of sagebrush were present, degraded, or absent; and 2 indices of human disturbance effects on populations. This model was validated with data independent of that used for model construction, and inter- estingly, the amount (percent area) of sagebrush habitat contributed substantially more to high model performance than did other variables, particularly non-vegetative factors (Wisdom et al. 2002b).

Identifying each species' requirements in relation to the classification system of vegetation used for mapping, for estimating the amount, location, and configuration of the species' source habitats and associated conditions, and for considering the spatial effects of non-vegetative factors that also influence habitats or populations, are key components of a regional assessment. At a minimum, the cover types that function as source habitats need to be identified, along with supporting rationale, so that habitat amount and location can be estimated and mapped. As an example, the 57 land cover types classified in the 90-111 land cover map for the sagebrush ecosystem (Chapter 3) can be used to designate source habitats for each sagebrush-associated species (Table 1.4).

In summary, the basic steps for estimating each species' requirements for regional assessment include the following. First, identify the vegetation coverage to be used, such as the 90-m land cover map described in Chapter 3 and by Comer et al. (2002) for the sagebrush ecosystem. Second, associate each species with the cover types known or considered to be source habitats, based on literature review and an evaluation by species experts with spe- cialized knowledge of each taxon. Ex- ample habitat associations are shown for sage-grouse and loggerhead shrike

TABLE 1.5. Potential threats and associated effects oil habitats and species in the sagebrush ecosystem, with example references

Potential threat Associated effects Examples Fi;xampie rcferenccs

Weather, climate Environmental- change, and ca- habitat loss or tastrophes degradation

Population-sto- cllastic events

Roads and high- Environmental- ways habitat loss

Environmental- habitat fragmentation and degradation

Population-barrier to migration or road avoidance

Population-direct ancl indirect inor- tality

Gradually increasing temperatures have contributed to drought and more severe and frequent wildfires, es- calating the spread of invasive plants si~ch as cheatgrass in sagebrush ecosystems. Drought years in close succession can lead to losses of key forbs used by sagebrush-associated species.

Catastrophic events such as floods and severe drought can lead to extirpation of small populations

Creation of roads and highways and their associated rights-of-way I-esult in direct loss of habitat

Creation of roads and highways and their associated rights-of-way fragments sagebrush habitats; roads may accelerate the spread of invasive plants

Roads may serve as movement or migration barriers to less mobile species; animals may avoid traffic or other activities associated with roads

Death or injury from collisions with vehicles, and increased mortality from poaching due to improved access

Tausch et al. 1993, Miller arid Eddie- man 2000, Smith et al. 2000, Neil- son et al. 2005

Burgman et al. 1993, A~idelnlarl ct al. 2001, Morris and Doak 2002

Forman et al. 1997, 2003; Forman 2000; Giicinski et al. 2001 ; Spel- lerberg 2002

Forman et al. 1997, 2003; Brauci 1998; Parendes and Jones 2000: Guciiiski et al. 200 1 ; Neely et al. 200 1 ; Havlick 2002; Spellerberg 2002; Gai~ies et al. 2003; Gelbard and Belnap 2003; Gelbard a11c1 Harrison 2003

Mader 1984, Bennett 199 1, Reijr~cn et al. 1997, Wisdom et al. 2000, Spellerberg 2002, Fornian et al. 2003, Gaines et al. 2003, Ingelfin- ger and Anderson 2004

Patterson 1952, Olendorff and Stod- dart 1974, Blrrmton 1989, Wisdom et al. 2000, Todd 200 1 , Havlick 2002, Forrnan et al. 2003, W o d s et al. 2004

TABLE 1 .5. Cor~tinued

Potential threat A\soeiutecl effect Examples Exa~iir,le reSereticc\

Intensive livestock Environrnei~tal- grati ng habitat ctegrada-

tion

Population-direct rnortali ty

Oil anct natural gas Environmental- tielcl develop- habitat loss and ~nent fragmentation

Population-disturbance

Environmental- habitat degradation

Fences Enviroi~mer~tal- habitat hagmen- tation

Population-direct mortality

Expansion of juni- Erivironmental- per and other habitat loss and woodland spe- degradation cies iii sagebrush co~nrnunities

Ecologically inappropriate grazing by domestic stock, especially cattle and sheep, leading to loss of native perennial grasses and forbs in the understory (changes in composition and structure), with resulting declines in forage and other habitat components for species of concern and their prey (e.g., invertebrates); trampling tnay destroy burrows used by some species such as bui-rowing owls or pygmy rabbits

Mortality froin trampling of nests

Pipelines, roads, well pads, and associated collection facilities fragment habitats; outright loss of habitat also occurs from road and well pads and other facilities constructed for field development

Disturbance and potential abandonment of habitat due to vehicular traffic, other noise (e.g., compressor stations), and related human activity at well sites

Disturbed sites (e.g., roadsides and well pads) may become infested with i~ivasive species

Construction of fences in sagebrush ecosystems can fragment habitats and interfere with animal move- rnent (e.g., pronghorn)

Animals can collide with fences or beconne entangled, leading to injury or death

Changes in climate and fire suppression have led to expansion of pinyon pine and juniper woodlands into sites previously occupied by sagebrush, especially in mo~~ntain big sagebrush and Wyoniiilg big sagebrush

Bock et al. 1993, Fleisch~~er 1994, Saab et al. 1995, Guthrey 1996, Schroeder et al. 1999, Beck arid Mitchell 2000, Miller and Ecldle- man 2000, Johnson and <)'Neil 2001, Freilich et a]. 2001, Noss et al. 2001, Hol~nes et al. 2003, % Knick et al. 2003, Thines et ill.

Iri

2004 2 0 Fleiscliner 1994, Beck and Mitchell a

2000, Holrnes et al. 2003 v1

Braun 1998, Brnun et al. 2002. N~nm 2 2002, Weller et al. 2002, Connelly g et al. 2004 V,

V,

Bowles 1995, W~I-I-ick and C'ypher E

1998, Dyer 1999, Brailri et al. E 2002, Lyon and Anderson 2003 !2

Zink et al. 1995, Parendes and Jorres -3

2000, Trorn b ~ ~ l a k and Fri ssell I 3

2000, Fornian et al. 2003, Gelbar-d g and Belnap 2003 .d %

Braun 1998, Connelly et al. 2004, w

IO, O'Gara and Yoaki~m 2004 T.

?-

Oakley and Ridcile 1974, Fit/,ne~- 1975, Call and Maser 1985, Todd 200 1 , (1' Gara and Yoaki~m 2004

Blackburn and Tuellcr 1970; Burk- hardt and Tisdale 1976; Miller and Wigand 1994; Miller and Rose 1995, 1999; Comrnorls et al. 1999; Miller and Eddlernari 2000; Miller and Tauscl~ 200 1 w -

TABLE 1.5. Continued - ---

Potential threat Associated effects Examples Example references

Invasions o f exotic Environn~ental- plants habitat loss and

degradation

Reservoirs, dams, Environmental- and other water habitat loss developments

Environn-tental- habitat degradation

Environmental- habitat loss and fraginentation

Herbicides

Power lines Environmental- habitat degradation

Population-increased rates of predation

Altered fire re- Environmental- gi~nes habitat loss


Altered fire regimes and habitat degradation (e.g., from intensive livestock grazing) have led to increases in exotic plants (e-g., cheatgrass) in sagebrush ecosystems; noxious weeds can also be acci- dentally introduced during reclamation of oil and gas well sites

Outright loss of habitat from establishment of reservoirs in sagebrush habitat

Altered stream flows and hydrological regimes may degrade or change habitat for aquatic and riparian species

Herbicides used extensively prior to the 1980s for conversion and relnovai of sagebrush, especially if native understory vegetation was in relatively good condition

Disturbance of vegetation and soils in corridors can lead to increased invasion of exotic species in these areas

Poles and towers for transmission lines may serve as additional perches or nest sites for corvids and raptors, increasing the potential for predation on sagebrush-associated species

Birds may collide with power lines, resulting in injury or death; electrocution of perching raptors and other birds also occurs

Increases in catastrophic wildfires, often related to invasions of cheatgrass, have resulted in complete re- ~noval of sagebrush cover (i.e., type conversion), especially in Wyoming big sagebrush com~nunities

Fire suppression has led to altered fire cycles in sagebrush ecosystems, resulting in changes in vegetation composition and structure, e.g. encroachinent of woodlands into sagebrush

Yensen 198 1 , Billings 1994, D' Antonio and Vitousek, 1999, Knick 1999, West 1999, D' Antonio 2000, Miller and Ed- dletl~an 2000, Booth et at. 2003, Menakis et al. 2003

Braun 1998, Schroeder et al. 1099, Nachlinger et al. 200 1

Pierson et al. 2001, 2002, 2003

Best 1972, Braun and Beck 1977, Braun 1998, Co~lnelly ct al. 2000, Miller ancJ Eddleman 2000, Con- nelly et al. 2004

Zink et al. 1995, B r a ~ ~ n 1998

Gilmer and Wiehe 1977, Knight and Kawashillla 1993, Stecnhof' et al. 1993, Braun 1998

O'Neil 1988, I-Iarnlata et al. 2001

Whisenant 1990, Billings 1994, D' Antonio and Vitousek 1 999, Knick and Rotenbery 1999, Neely et al. 2001, Menakis et al. 2003

Schroeder et al. 1999, Miller and Eddlenlan 2000, Connelly el al. 2004

TABLE 1.5. Continued -- ----

Potential threat A\sociated effect\ Examples Exarnplc referencex

Urban development

Herbivory effecth from wild ungulates

Disease transmission

Brood parasitisnt by brown-headed cowbirds

Recreation

Ertvironmental- habitat loss

Population-hulltan disturbance



Enviro~ttnental- habitat degradation

Development of urban areas and "sanchettes" surrounding urban sites results in direct loss of sagebrush habitats

Increases in human activities in urban and exurban as- eas may negatively affect populations of sagebrush- associated species by displacement or abandonment. Predation rates on wildlife in sagebrush habitats also may increase from domestic dogs and cats in urban and rural settings, as well as from increased populations of predators such as corvids, due to increased availability of food resources associated with human waste (e.g., garbage dumps, trash in campgrounds).

Localized, excessive herbivory by native ungulates can lead to degraded understories in sagebrush ecosystems (e.g., changes in species composition and structure) and reductions in sagebrush densities and canopy cover

Disturbance from oil and gas development may lead to concentrations of native ungulates on winter ranges, exacerbating disease transmission during the stress- ful winter season. In addition, man-made water sources, particularly those whose status has changed fi-om ephemeral to permanent from human activities, ]nay lead to increased transinission of mosquito- borne diseases such as West Nile virus.

Populations of some avian species (e.g., lark and vesper sparrows) in the sagebrush ecosyste~n may be affected by parasitism from brown-headed cowbirds, a species which may increase in human-altered environments, such as livestock feedlots and over- grazed pastureland

Off-road vehicle use can degrade habitats in the sagebrush ecosystein, e.g., by increasing presence of exotic annual grasses like cheatgrass

Braun 1998, Conttelly ct al. 2004

Berry et al. 1998, Millsap ancl Bear 2000, Arrowood et al. 200 1 , Neely et al. 2001, Knick et al. 2003

5 2 9

McArthur et al. 1988, Singer and Renkin 1995, wunbolt a~tct Shcr- wood 1999, Groves et al. 2000 (Appendix 20)

Naugle et al. 2004, Rowland 2004, Walker et al. 2004, U.S. Govern- ment 2005

Friedniann and Kiff 1985, Robi~~son et al. 1995, Shaf i r et al. 2003

Berry 1980, Havlick 2002, Munger et al. 2003

W TABLE 1.5. Continued .P

Potential threat Associated effects Examples Example referct~ces

Population-human disturbance

Conversion of Environmental- sagebrush to habitat loss cropland or tame past~rre for livestock

Environmental- habitat fragmentation


Mine development Environmental- habitat loss and fragmentation

Population-disturbance

Pesticides Environmental- habitat degradation

Population-mortality

Recreational activities, such as off-road vehicle use in sagebrush habitats, may affect species of concern, e.g., displacement or nest abandonment. Recreation- al shooting of small mammals also can directly affect populations.

Removal of sagebrush cover (e.g., via brush-beating, chaining, disking, or burning) and planting with crops, such as alfalfa, or with non-native perennial grasses (e.g., crested wheatgrass) for livestock forage; example affected species: greater sage-grouse, swift fox, and ferruginous hawk

Removal of sagebrush may lead to fragmentation of remaining sagebrush habitats, resulting in interfer- ence with animal movements, dispersal, or population fragmentation

Nest and egg destruction, or directly mortality of ani- ~nals, from mechanical or other methods ~ised to re- move sagebrush or to cultivate lands adjacent to sagebrush

Fragmentation and outright loss of habitat to surface mines and associated mine tailings and roads, especially coal mines

Disturbance and potential abandonment of habitat due to traffic, noise, and related human activity at mine site; example affected species: bats, greater sage- grouse

Decrease in forage base by killing of insects used as prey by sagebrush-associated species

Direct mortality of birds and other vertebrates exposed to pesticides, and indirect mortality through con- sumption of contaminated insects

Berry 1980, White and Thrtrow 1985, Braun 1987, Knight and Gtitzwiller 1995, Schroeder et al. 1999, Havlick 2002, Munger ct al. 2003

Vale 1974, Dobler 1994, Fischer et al. 1997, Braun 1998, Knick 1909. Schroeder ct al. 1999, West 1999, Miller and Eddlen~an 2000, John- son and O'Neil 200 1, Knick et al. 2003 4

Knick and Rotenberry 1995. 1097, - 2002, Johnson and O'Neil 2001, 3> Knick et al. 2003, Connelly et al. 2004 I3

Patterson 1 952 m 2 0

2 Braun 1998, Ricketts et al. 1999,

Neely et al. 2001 R 5 m

Bednarr, 1984. Brar~ri 1998

Johnson 1987, Holmcs ct ~11. 2003

Patterson 1952, Blus et al. 1989, Blus 1996

TABLE 1.5. Continued

Potential threat Associated effects Examples

Saline-soclic water

Wind energy development

Collection of speci- mens for pei-son- 31, cornmercial, or scientific uses

Groundwater deple- tion

Grazing by feral horses

Seleni~tm and other environmental contaminants

Military training

Eiivironmental- habitat degradation


Population-mortali ty

Population-loss of individuals from the wild


Environmesital- habitat degradation

Popu lation-direct threat of mortali- t Y

Environmental- habitat fragmentation

The disposal of millions of barrels of water produced during coal-bed methane extraction can lead to sali- nization of sui-rounding soils and aquatic systems into which these waters may be dumped. In addition, sodic water discharged from wells can lead to high mortality rates (up to 100%) in vegetation exposed to such discharge.

Increase of noxious weeds in areas around turbines or along roads needed to access turbines; loss of habitat frorn road construction and turbine installation. In addition, some species may avoid the area near turbines due to the association of such structures with nests or perches of avian predators such as corvids

Deaths and injuries of birds and bats frorn collisions with wind turbines

Collection of rare plants and animals, especially herptiles, may pose unknown risks to populations of these species; example species: midget faded rattle- snake

The pumping of water for coal-bed methane may lead to excessive groundwater withdrawal in the well sites

Loss of native perennial grasses and forbs in the understory

Poisoning of animals from uptake of selenium in contaminated aquifers, primarily from agricultural run- off

Training exercises in sagebrush habitats may result in loss of shrubs from both wildlife and destruction from tracked vehicles, and may lead to habitat fragmentation

Example references

Groves et al. 2000 (Appendix 20), McBeth et al. 2003

Forrnan et al. 1997, 2003; Gelbard and Belnap 2003

Erickson et al. 2001 [http:l/ www.nationalwirid.orgl

Wisdom et al. 2000, Freilich et al. 200 1. Woods et al. 2004

Groves et al. 2000 (Appendix 20), Nachlinger et al. 200 I

USDI BLM et al. 2000, Y o ~ ~ n g and Sparks 2002, Beever 2003

Lemly 1997

Knick and Rotenberry 19'37, E-lolmes and Humple 2000


(Table 1.4). Third, describe the configuration of source habitats considered to be optimal versus marginal for the species, at least for example species where these estimates are known or can be plausibly hypothesized (see Additio~zal Methods of Spatial and Temporal Anal- ysis). Last, identify non-habitat factors that also could affect species' persistence, such as population size, population isolation, inbreeding depression (e.g., Lee 2000, Nlarcot et al. 2001) or anthropogenic effects such as those associated with roads, electric transmission lines, and other land uses in the sagebrush ecosystem (Knick et al. 2003, Connelly et al. 2004).

Recently, a comprehensive method to evaluate potential effects of many or all anthropogenic features on species of concern, referred to as "human footprint" analysis (Sanderson et al. 2002), has been applied to sagebrush ecosystems (Weller et al. 2002; Chapter 12 in Connelly et al. 2004; Rowland et al. 2005; Thomson et al. 2005). However, specific effects of a wide variety of human disturbances and land uses on sagebrush-associated species are not well studied, thus complicating the challenge of how the cumulative, human footprint patterns actually affect each species. Despite this shortcoming, identification of disturbance factors that are likely to affect species of concern, and development and application of plausible evaluation methods to assess their potential effects, will allow regional assessments to be more cornprehensive in evaluating conditions for individual species of concern (see Step 7, Calculate Species-Habitat Ejcects @01'~2 Risks of all Thi-eats).

5. Identify Regional Threats arzd Poterztial Effects-Identification of regional threats and their potential effects is perhaps the most fundamental and essential component of any regional assessment for species of concern. Con-

sideration of threats to species of conservation concern has a well-established and compelling history based on the long-standing work of The World Con- servation Union (IUCN). The IUCN identifies their "redlist 'kf species that includes consideration of a cornprehensive list of threats [http://www.redlist. orgl]. The term "threats" represents the collective value judgments of society, as represented by federal laws that require federal managers to consider the effects of all potentially detrimental land uses on native species and their habitats (see earlier discussion of federal laws as well as the discussion by Connelly et al. [2004]). Our focus on identifying threats to sagebrush habitats and species comes directly from these societal values and associated laws, but our methods themselves are a clinical means of evaluating the associated effects.

That as context, a plethora of factors considered to be potential threats to the sagebrush ecosystem and its associated species have been identified (Table 1.5), but whether a given factor actually pos- es a threat in a given ecoregion is highly variable and requires careful consideration of supporting evidence. Conse- quently, the list of potential threats in Table 1.5 can be used as a starting point, from which a smaller set of factors can be identified that deserve assessment in a particular ecoregion. Stated another way, many of the potential threats in Ta- ble 1.5 may not be relevant to many re- gions, and great care must be taken in identifying and justifying which threats pose major risks in a particular region.

The importance of these potential threats will vary spatially within and across ecoregions, depending on local environments, both ecological and po- litical. For example, loss of sagebrush from cheatgrass invasion is a major threat for the Great Basin and Columbia Plateau Ecoregions (Nachlinger et al. 2001, Bradley and Mustard 2005)

METHODS OF ASSESSMEKT-W~SL~'OI?Z ef ul. 37

(Chapter 4). By contrast. energy development is a more pervasive threat in the mTyoming Basins Ecoregion (Braun et al. 2002, Knick et al. 2003, Rowland et al. 2005, Thomson et al. 2005). In addition, the significance of various threats to the sagebrush ecosystem has changed over time: some issues, such as large-scale conversion of sagebrush to cropland, have dinlinished, while others, such as invasion of exotic species, have expanded.

Beyond a simple list of potential threats, risk assessment involves "ob- taining quantitative or qualitative measures of risk levels" (Burgman et al. 1993:13). Estimating risks to habitats for species of concern is essential to in- formed decision-making. Without such estimates, management decisions may be based on unrealistic perceptions of risk. Risks that are less responsive to management actions often are perceived to be less important than those that can be addressed easily (Burgman et al. I 993).

Results from risk assessment provide information that decision-makers can use to allocate limited resources for species conservation and management. For example, one could estimate the risk of encroachment by pinyon-juniper woodlands into sagebrush based on elevation, precipitation, taxon of sagebrush, proximity to pinyon-juniper, and other factors (Fig. 4.2, Chapter 4). Sagebrush sites at high risk of invasion could be targeted for removal of nearby pinyon- juniper (Chapter 4). In addition, mapping sagebrush stands by risk would allow managers to identify areas where less attention is currently warranted, as well as areas where immediate action is needed to reduce the risk of woodland encroachment. An example of mapping this threat is provided in our regional assessment of the Great Basin (Chapter 4). Importantly, the spatial and temporal scales of management treatments must

be evaluated to ensure their effectivs- ness to reduce risk over time and space in relation to management objectives.

Risk assessment also requires consideration of vegetation resistance and resiliency in relation to disturbances irn- posed by each threat. Wisdom et al. (2005) defined resistance as the degree to which a given vegetative state can maintain itself in the face of disturbance. These authors defined resiliency as the degree to which a given vegetative state returns to its former state when changed by a disturbance. In general, sagebrush communities that are warmer and drier have low resistance and resiliency, and therefore are associated with higher risks of being displaced by a given threat (Wisdom et al. 2005). These patterns are typified by the estimated risks associated with cheatgrass displacement of sagebrush and other native shrublands (Tables 1.6, I .'7; Chapter 4). In this case, Wyoming big sagebrush communities at low eleva- tions, which are mostly at the dry and warm end of sagebrush site conditions, are at highest risk of displacement by cheatgrass (Hemstrom et al. 2002), and thus require different management strategies than those for mountain big sagebrush communities associated with sites that are wetter and colder (USDI Bu- reau of Land Management 1999,20OOn, 6, 2002, 2004).

An added complication of threats assessment is that potential effects of some threats are easily measured and mapped, while others may be difficult or impossible to evaluate at regional scales. Threats that are more easily measured and mapped at regional scales typically are processes that influence specific points on a landscape, such as roads, energy and mining development, and agricultural and urban areas. Threats more difficult to measure and map include processes that typically are diffuse and thus difficult to measure


TABLE 1.6. Risk levels defined for the probability that sagebrush and other wsceptible native cover types will be displaced by cheatgrass in the Great Basin Ecoregion during the next 30 years (from Chapter if), and the associated level of resistance to cheatgrass invasion

Risk l e ~ e l Associated effect Resiitance

Moderate

Low The probability that cheatgrass will displace existing sage- High brush or other susceptible cover types is minimal; native plants are likely to dominate the understory of these stands at the current time.

The probability that cheatgrass will displace sagebrush or 0th- Moderate er susceptible cover types is moderate, but lower than for types at high risk; either cheatgrass or native plants can dominate the understory at the current time.

High The probability that cheatgrass will displace sagebrush or oth- Low er susceptible types is very likely: cheatgrass is likely to dominate the understory (vs. native plants) at the current time.

through remote sensing methods, even when the threats may be extensive. Ex- amples of more diffuse threats include predation, off-road recreation, herbicides, and ungulate grazing. The potential to overlook potential effects of more diffuse threats is an important point to consider when conducting a threats assessment, and additional forms of data collection, beyond remote sensing and use of existing maps, may be required.

Threats to a species' persistence in the sagebrush ecosystem can be broadly categorized as environmental (indirect) or population (direct) (Fig. 1.9). Envi- ronmental effects pose indirect threats to populations by first degrading the environment on which the species depends, which in turn affects population characteristics (Fig. l .9). Environmental effects often are amenable to management, are primarily deterministic, and include such changes as habitat loss, habitat degradation, or environmental contamination (Andelman et al. 200 1, Morris and Doak 2002). Population effects often are stochastic, and come into play when small population sizes occur in response to some combination of direct and indirect threats. Population effects and the resulting problems include genetic considerations, such as inbreed-

ing depression, and demographic effects, such as Allee effects (Andelman et al. 2001, Morris and Doak 2002) (Fig. 1.9). Ultimately, managers are concerned about all threats to population persistence, which can increase the likelihood of population extirpation, or even the extinction of a species (Fig. 1.9).

Efforts to classify threats according to their potential effects (e.g., whether the threats affect populations directly, indirectly through the environment, or both; Table 1.5 and Fig. 1.9) are con- founded by the synergism of many threats, as well as the multiple ways in which single threats may be expressed in the system. For example, intensive livestock grazing can simultaneously reduce the quality of habitat for foraging by, and increase predation pressure on, greater sage-grouse (Beck and Mitchell 2000, Crawford et al. 2004). Intensive grazing can result in (1) removal of perennial grasses and forbs that support insects and other prey items; and (2) the loss of forbs that serve as key forage items in the spring (environmental effect of habitat degradation; DeLong 1993, Cregg et al. 1994). Removal of grasses may also increase predation rates on nests by decreasing nesting

METHODS OF ASSESSMENT-Wisdom et ul. 3 9

TABLE 1.7. Interpretations of the levels of risk that cheatgrass will displace existing sagebrush or other susceptible native cover types in the Great Basin Ecoregion

Understory dominance of

cheatgrass versus Resiliency after Vulnerability to Relation to restoration Risk native grasses disturbance disturbance effects threshold

Low Native grasses High Low to moderate Above Moderate Variable Variable High Above but close to

dropping below High Cheatgrass Low or very low High to very high Below

cover (a second example of habitat deg- ular assessment must be based on de- radation; Gregg et al. 1994, DeLong et fensible criteria, which are likely to in- al. 1995). clude some or all of the following:

In summary, different sets of potential threats listed in Table 1.5 pose prob- Spatial extent or pervasiveness of the lems in different ecoregions, and many threat across the ecoregion; threats are limited to a particular region. Agreement among those conducting Consequently, decisions about which the assessment about the relative im- potential threats to address in a partic- portance of the threat in the ecore-

gion and the rationale for the threat's importance, including consideration of expert views on the issue; Public opinion about the threat;

Indirect Direct Available resources to address the agricultural development poaching urbanization overharvest threat; exotlc plants . predation energy development pesticides

Timeframe required to implement effective treatments across the ecoregion; Costs versus benefits of addressing

Habitat IOSS the threat; Habitat degradation Habitat fragmentation Management opportunities provided and isolation by contiguous land ownership, such

as expansive areas of federal lands (Fig. 1 2); and Potential effects of addressing the

lnbreedlng depression, other genetlc effects threat On non-target species and other Allee effects Vulnerab~lity to demographic stochasticity, resource goals. env~ronmental vanation, and catastrophic events Any combination of these criteria

might be used to identify the dominant, regional threats for a given ecoregion. Obviously, the more criteria considered,

Increased probabrl~ty of population the better the justification for conducting a regional evaluation of a given

FIGURE 1.9. Conceptual diagram of the di- threat. Identification of regional threats rect and indirect effects of human activities on and their potential effects On

population persistence of species of conser- concern can draw substantially on vation concern. knowledge from rangeland management


step 7

Anafflcal Steps

Identrfy the threat t o s a g e b r u s h l habltats or species based on prior +-. research Fable 1 5) and an 1 Threat explrctt justifrcatton for the particular region (see text). I

d

Example 7 Example 2 r I Transmtss~on line-facilitated 2

k sagebrush or other suscepttble predat~on of sagebrush- 1 habitats in the Great Basin associated species ~n the

B i Wyomrng Basins d

i.

I 4 Ellmination of susceptible cover

Step 2 1 types for species that depend on /I these types as hab~tats. li

+ Low, moderate, or high probability that cheatgrass will eliminate susceptible cover types at a given site.

1 I

I/

Establish spatial rules by which Susceptible cover types at the risk levels will be mapped. warmer sites are at higher levels 1 of risk. I

Step Repeat steps 1-5 with new relation to mapped patterns of research information, as needed. risk.

Establishment of a population /I

The probability, from 0.0 to 1.0, 1 of a population sink for a susceptible species at a given distance to a transmission line. 1

probability of a population increases with increasing

roximity to a transmission line.

20% of area has a probability of >0.90, 50% has a probability of 0.50 to 0.90, and 30% has a

Collect field data to estimate population fitness of susceptible species in relation to distance

FIGURE 1.10. Analytical steps for assessing effects of threats on habitats and populations of species of concern in the sagebrush ecosystem.

specialists, wildlife biologists, endangered species specialists, and other resource professionals working in the assessment area, along with published literature. At a minimum, the list of dominant threats and potential effects should be reviewed and refined by local and regional experts to derive a list like that shown in Table 1.5, customized for the ecoregion.

6. Estitnate a n d Map the Risks Posed by each Threat-Once the regional threats are identified and their potential effects described, the risks posed by each threat can be estimated and mapped to evaluate the spatial effects on habitats or populations of species of concern. While Table 1.5 can be used as a master list to identify possible threats and to describe their general effects, specific risks may be difficult to quantify (Burgrnan et al. 1993). Gon-

sequently, we developed a set of analytical steps as a framework for assessment of threats, as outlined in Fig. 1.10. We use 2 examples to illustrate the steps: (1) cheatgrass displacement of sagebrush and other shrubland habitats (Fig. I . 1 1); and (2) electric transmission lines as such lines facilitate avian predation of susceptible species of concern (Fig. 1.12).

First, identify the threat that will be assessed, including the supporting criteria and rationale (see earlier discussion and criteria). Second, define the specific effect or effects of the threat that will be evaluated. An effect could be habitat loss, population decline, or any combination of negative impacts to habitats or populations of species of concern (Fig. 1.9). In the cheatgrass example, the effect is the elimination of sagebrush and other shrubland habitats

METHODS O F ASSESSMENT-W~.SCECIIT~ er a/ . 3 1

Cheatgrass Risk a None

Low Moderate High

&##&! Water n BLM Field

Office Boundaries

0 50 100 200 - Kilometers

FIGURE 1.1 1. Case example of threat posed by cheatgrass displacement of sagebrush and other susceptible cover types in BLM Field Offices in Nevada during the next 30 years (see analysis and results in Appendix 7). Categories of risk of cheatgrass displacement are defined as none, low, moderate, and high, as described in Chapter 4.. In this example, levels of risk of displacement of sagebrush and other susceptible cover types are not mapped explicitly in relation to any species' habitats. Instead, risk to all cover types is shown. Results would vary by species of concern in relation to each species' range and habitat associations (Chapter 6).

from invasion and subsequent dominance by cheatgrass (Chapter 4). In the example for transmission lines, the potential effect is a declining rate of population growth (i.e., a population sink, see Glossary) for species susceptible to increased predation by raptors and corvids that use the towers along the lines as perches or nesting platforms (Gilmer and Wiehe 1977, Knight and Kawashi- ma 1993, Steenhof et al. 1993) (Fig. 1.12).

Third, define the risk levels associated with varying likelihood of the effect occurring; that is, describe the way in which the likelihood of an effect will be expressed and interpreted. Risk levels typically are defined as probabilities, ranging from 0.0 to 1 .O, where 0.0 represents a 0% chance of the effect occurring, and 1.0 equals 100% chance (Burgman et al. 1993). Alternatively, categories of risk can be defined, such as low, moderate, and high, with ex-

42 PART I: ASSES SING THREATS

Transmission Line

Predation Level High

Moderate

Low

4 * 0.0 1.00 0.0

Probability of a Population Sink

FIGURE 1.12. Conceptual example of threat posed by an existing or proposed electric transmission line in the sagebrush ecosystem, based on use of these lines by avian predators. Levels of risk are expressed as probabilities, frorn 0.0 to 1.0, that a species susceptible to being preyed upon by an avian predator will experience a declining rate of population growth, or a population "sink," based on the distance from a line and associated predation effect. Probabilities decline with increasing distance frorn the transmission line (see text for details).

plicit descriptions of the meaning and interpretations of each. For the cheatgrass evaluation, we defined varying levels of risk that native vegetation will be displaced by cheatgrass (Tables 1.5, 4.5; Fig. 1.11). Note that these definitions also identify the time period over which the associated habitat loss may occur in association with the risk level. For evaluation of transmission lines, the probability of a population sink for a species susceptible to a high rate of avian predation might range from 0.0 to 1.0 in relation to distance from the line (Fig. 3.12).

Fourth, develop a spatial rule set for mapping each risk level in a geographic information system (GIs); in the case of cheatgrass displacement of native vegetation in the Great Basin, a rule set based on elevation, aspect, slope, and landform was used (Table 4.5). For transmission lines, the probability of a population sink might approach 1.0 at distances close to the line, but fall to 0.0

at a distance far from the line (Fig. 1.12). Rules for assigning specific probabilities by distance could be based on probability ''decay functions, ' "hich project a diminishing level of avian predator activity with increasing distance from transmission lines and other linear features (see Chapter 12 in Con- nelly et al. 2004).

Fifth, map and summarize the amount of habitat within each risk level, and interpret the results for management. In the cheatgrass example, 34% of sagebrush and other native vegetation in Nevada was mapped at high risk, and the remaining 66% was mapped as low or moderate risk (Fig. 1.1 1, Chapter 4). Likewise, the percent area with a high probability (e.g., >0.90) of a population sink for species susceptible to avian predation, versus lower probabilities, can be summarized by distance from transmission lines (Fig. 1.12).

These spatial summaries can be used to interpret and describe the potential implications for management, particularly in relation to time, area, and resources needed to mitigate various risk levels. Example interpretations and implications for the threat posed by cheatgrass are shown in Table 1.7. Example implications from results of the transmission line evaluation might include 2 major points: ( I ) efforts to improve habitat conditions in close proximity to a transmission line may not be effective if such areas have a high probability of being a population sink because of the line; and (2) placement of new transmission lines would have least impact on susceptible, sagebrush-associated species if the lines are located in existing powerline corridors or other areas of extensive human development. Al- ternatively, placement of new lines would have most deleterious impact if placed directly in large blocks of sagebrush and other native shrublands that

METHODS OF ASSESSMENT-Wi.sdo~n et ul. 33

otherwise have lower levels of human disturbance.

Finally, evaluate the predicted risk patterns through peer review and subsequent research. Adaptive management is an effective means of evaluation (Walters 1986). Adaptive management uses the following process: ( I ) managers identify knowledge gaps that are deemed critical to more effective management (in this case, more accurate maps of risk for improved management and mitigation of pervasive threats); (2) managers and scientists jointly develop testable hypotheses to address the knowledge gaps (in this case, the initial risk maps provide testable hypotheses); (3) scientists design and implement studies to test the hypotheses (such as collecting field data to evaluate the plausibility of each risk map for each threat and effect); (4) managers and scientists interpret and disseminate results from the studies for management use, including improvements in the models and resultant predictions (e.g., changing the spatial rules and resulting maps of risk based on new information about likelihood of a threat's effect); ( 5 ) managers and scientists identify additional knowledge gaps and hypotheses for testing, based on study results and en- suing questions that arise from the results (such as follow-on research to address unexpected results or important issues of high scientific uncertainty not resolved in prior research); and (6) the cycle is repeated 1 or more times, if desired, using knowledge gained from earlier phases of study.

Without adaptive management, the risk patterns mapped for each threat will be only as strong as the empirical data upon which they are initially based. For most potential threats in the sagebrush ecosystem (Table 1.5), the general effects may be documented, but the specific effects on particular habitats and species typically are not. In the cheat-

grass example, the loss of sagebrush from cheatgrass invasion may have been documented, but the resultant effects on populations of sagebrush-associated species are less clear. Species responses are complicated by time lags in population responses to habitat change (Knick and Rotenberry 2000) as well as imprecise knowledge about the actual responses. In the example of transmission lines, avian predators are known to benefit from the presence of the lines, but the specific effects on most prey species have not been studied. This problem is true even for well-studied species like greater sage-grouse, for which only anecdotal evidence exists about population effects from predation along transmission lines (see summaries by Rocklage et al. [2001], Rowland and Wisdom [2002]).

As part of the threats assessment, it is important to identify ecological thresholds, if any, in relation to levels of risk. For example, areas of sagebrush at moderate risk to displacement by cheatgrass are considered to be slightly above the threshold for displacement; once the threshold is crossed, conversion to cheatgrass may be permanent (Chapter 4). By contrast, areas of sagebrush at low risk are considered to be well above this threshold, while areas at high risk have likely passed through the conversion threshold (Table 1.7, Chap- ter 4). These patterns suggest that resources available for reducing the risk of cheatgrass displacement are best di- rected toward mitigating the threat to areas at moderate risk.

Estimation of spatially pervasive threats can be used as the foundation for more specific evafuations of habitat conditions and threats for single and multiple species of concern, as applied to individual species ranges and habitats, as well as to the collective range of all species across all habitats. Our assessment for the Great Basin provides


additional examples of how threats and associated risks can be evaluated for individual species and for groups of species (Chapters 6, 7).

7. Calculate Species- Habitat Effects frotn Risks of all Threats-The process of identifying regional threats and associated risks can be used to map and calculate the current amount and location of habitats for each species, within its range, by the type of threat and the risk levels posed by each threat. This process involves the following steps. First, map the source habitats for the species within its range, and calculate the area occupied by these habitats. Sec- ond, for a given threat and associated effect, overlay the varying risk levels that index or specify the probabilities of the effect occurring in relation to the species' source habitats. And third, calculate the area of source habitats associated with each of these risk levels.

This analysis is straightforward when addressing a single threat, as illustrated for habitats of greater sage-grouse and sagebrush vole in relation to the risk that cheatgrass will eliminate these habitats in the Great Basin (Fig. 1.13). The process becomes more complex, however, when multiple threats and associated risks are considered. In this case, the combination of multiple threats to a species' habitat may be difficult to summarize and interpret, owing to complexities of many categories of combined risks and the potential interactions among threats. For example, 3 levels of risk from cheatgrass invasion and 3 levels from pinyon-juniper displacement combine to form 9 categories of collective risk to sagebrush habitats (Chapter 4).

Another example is the combined effects of energy development and transmission lines. To evaluate effects of energy development, levels of risk might be based on varying distances of sagebrush habitats to development (Fig.

1.14). We define the area of development as the energy site itself-such as a group of well pads. compressor and pumping stations, and pipelines-and the associated network of roads used to access the site. Other anthropogenic features may also be present in association with the energy developrnent, such as electric transmission lines and pipelines that typically parallel the road system. Such features along the road system would be evaluated as part of the road access that serves the energy development sites.

In our example in Fig. 1.14, the specific effect being evaluated is the probability that a species' habitat will become unsuitable in response to energy development. Unsuitable habitat is assumed to have a low probability of occurrence for a specified species. Areas of habitat within and closest to the development boundaries are classified as being at high risk of being lost or degraded to the point of being unsuitable for the species. This high risk is associated with energy developrnent that converts habitat to energy sites and roads; increases fragmentation of remaining habitats; facilitates exotic plant invasions; establishes movement barriers or avoidance zones for native fauna; and contributes to a myriad of other un- desired human disturbance effects related to road use and access (Braun et al. 2002, Weller et al. 2002, Lyon and An- derson 2003, Connelly et al. 2004, In- gelfinger and Anderson 2004, Rowland et al. 2005, Thomson et al. 2005).

In our example, areas at increasing distance from the energy development boundaries are defined as moderate or low risk of being lost or degraded to the point of being unsuitable (Fig. 1.14). These risk levels by distance from development would vary by the species being evaluated, according to differences in home range, dispersal characteristics, and the species' response to hab-

METHODS OF ASSESSMENT-Wisd[m et at. 45

a State Boundaries

0 75 150

FIGURE 1.13. Habitat abundance and risk of habitat loss from cheatgrass, for sagebrush vole (A) and greater sage-grouse (B), in the Great Basin Ecoregion (see analysis described in Chap- ter 6 and additional results in Appendix 6). White areas are outside the species' range or contain no habitat.

itat fragmentation and disturbance (e.g., Ingelfinger and Anderson 2004). Many of the resulting habitats at moderate or low risk also may become unsuitable for some species because of their increased isolation and smaller patch sizes following the energy development (Fig. 1.14). Methods for estimating such risks

include (1) defining and mapping the development boundaries; and (2) estimating the degree to which habitat becomes non-functional by distance from site and by species. Weller et al. (2002) conducted a generic, landscape analysis of this type for oil and gas field developments that could be refined by the ex-


FIGURE 1.14. Conceptual example of threat posed by energy development in the sagebrush ecosystem, using an oblique photo of an area of intensive coal-bed methane production (top). Levels of risk are based on habitat area in relation to the nearest development, defined as the energy site itself and the associated network of roads. Habitat within the development boundaries is classified as being at high risk of loss or degradation to the point of being unsuitable, owing to habitat conversion to energy sites and roads, to habitat fragmentation, to facilitation of exotic plant invasions. and other human-associated factors of disturbance (bottom). In this conceptual example, habitat outside the development boundaries, but within specified distances from the boundaries are defined as moderate or low risk of being lost or degraded to the point of being unsuitable (bottom). These distance estimates would vary by the species being evaluated. according to differences in home range, dispersal characteristics, and response to habitat fragmentation and disturbance.

METHODS OF ASSES SMENT- Wisdom et al. 37

I I

Risk /I High

Moderate

I

Collective Risk V e r y High

intermediate

FIGURE 1.15. Conceptual example of the risks posed by energy development (panel A, adapted from Fig. 1.14), additional transmission lines (panel B, per concepts in Fig. 1.12), and the collective risk posed by combinations of both threats (C) for a sagebrush landscape. See Table 1.8 for explanation of risk levels.

pected responses of individual species or groups of species.

Estimating the combined effects of energy development wth transmission lines complicates the effects analysis substantially, as illustrated in Fig. 1.15. Here, the risks associated with energy development, shown earlier in Fig. 1.14, a re considered together with those for transmission lines that existed in the area before energy development (Fig. 1.15A, B). The transmission lines are located in areas both close to and far from the energy development sites (compare Fig. 1.15 A versus B). The result is that each of the 3 risk levels associated with transmission lines (per analysis shown earlier in Fig. 1.12)

overlap each of the 3 risk levels associated with energy development, resulting in 9 combinations of risk from the 2 threats (Table 1.8).

Such joint effects from 2 or more threats may be difficult to interpret with so many combinations of potential effects. Consequently, we suggest the following process be considered: (1) map and sun~rnarize the amount of habitat in the assessment area for every combination of risk levels from the 2 threats; (2) group the combinations of risk levels from the 2 threats according to their associated implications for management; and (3) interpret the findings for each group in terms of management op- tions and guidelines. Each group of risk levels can be thought of as the "collective risk" for each joint effect of the 2 threats.

For the combinations of risk levels associated with energy development and transmission lines, the areas at high risk from both threats, or from either threat, could be considered unsuitable for the affected species, and characterized as very high or high collective risk (Table 1.8, Fig. 1.15C). That is, these areas would have a low probability of species' occurrence and a high probability that these areas function as population sinks. By contrast, areas at low risk from both threats would likely be suitable for the affected species, corn- mensurate with the background habitat conditions present. Areas characterized by any combination of low and moderate risk from the 2 threats would then be considered intertnediate in their collective risk and their associated suitability for affected species and the probability of these species' occurrence (Fig. 1.15C).

Management implications from these 4 groups of collective risk-very high, high, intermediate, and low (Table 1.8)-include the following: (1) areas at very high or high risk would be difficult


TABLE 1.8, Combined risk levels from potential effects of 2 threats, energy development and electric transmission lines, and the groupings of these combined risks for management, referred to as groups of "collective risk," with example management implications for each group

Combined risk CoIIective leveI"rl risk Example implication5

--

High-High High-Moderate Moderate-High Low-High High-Low

Moderate-Moderate Moderate-Low Low-Moderate

Low-Low

Very High High High High High

Intermediate Intermediate Intermediate

Low

Habitats are unsuitable for the affected species and restoration is difficult. These areas are the best locations for additional roads, energy development, and transmission lines because detrimentai effects to species have already been realized and are difficult to reverse.

Habitat suitability is uncertain, and these areas may benefit from management to partially mitigate effects, such as through obliteration of access roads to energy development, and redesign of transmission lines and platforms to discourage use by avian predators.

Habitat is most suitable and most sensitive to any degree of energy development, road construction, or placement of transmission lines, with an expected increase in risk from low to high with any such developments.

.'The first risk level refers to that associated with energy development and the second refers to transmission lines. For example, a combined risk level of moderate-high ret'ers to a moderate level of risk associated with energy development, combined with a high risk associated wrth transmission lines.

to restore as suitable for the affected species; these areas would continue to serve as the best locations for additional roads, energy development, and transmission lines because the detrimental effects to species have already been realized and are difficult to reverse; (2) areas at low risk are most sensitive to any energy development or placement of transmission lines, with an expected increase from low to high risk; and (3) areas at intermediate risk may benefit from management to partially mitigate effects of the energy developinent and transmission lines, such as through road closures and obliterations and redesign of transmission lines and platforrns to discourage use by avian predators.

In the case of the combined risks of sagebrush displacement by cheatgrass and pinyon-juniper, the following management implications are noteworthy: ( I ) areas at high risk of displacement by cheatgrass, but also at high risk of dis-

placement by pinyon-juniper, may be difficult or impossible to maintain as sagebrush habitats, considering the management challenges posed by the combined risks; (2) areas at low risk of displacement by both cheatgrass and pinyon-juniper are most resilient to disturbance regimes of fire, grazing, and recreation; these areas therefore have a high probability of responding in a positive or neutral manner to a variety of management activities, excluding land use changes that eliminate habitat through conversion to urban, agricultural, mining, or energy development; and (3) areas at moderate risk to both cheatgrass and pinyon-juniper displacement are likely to be sensitive to fire, grazing, and other land management disturbances; that is, such disturbances in these areas rnay increase the vulnerability of sagebrush habitats to invasion and displacement by cheatgrass and pinyon-juniper. Consequently, areas at moderate

METHODS OF ASSESSMEET-Wisdom et tzl. 39

risk may demand the most management attention, and are likely to respond positively to appropriate improvements (Chapter 4).

One method of evaluating multiple anthropogenic effects in regional assessments is "human footprint" analysis (Sanderson et al. 2002, GLOBIO 2002). A closely related concept and method is "ecological footprint'' analysis (Wackernagel and Rees 1996, Wel- ler et al. 2002). Under human footprint analysis. all major land uses, or indices to such uses, that may pose threats- such as to species or their habitats-are mapped. Typically, the potential effect of each land use or anthropogenic fea- ture is assigned a score or other index, based on a relative scale. For example, Sanderson et al. (2002) ranked the effects of different land uses on a scale of 0 to 10, with 0 having lowest or no effect, and 10 having highest effect.

The areas potentially influenced by each land use are then estimated by distance from each use, using empirical data or hypothesized relations. All areas influenced by each land use are then assigned the human footprint score associated with the use. The composite of all scores from all land uses for a given area is then summarized, such as by av- eraging the scores across land uses to portray the cumulative effects. Many variations on how the scores are assigned to each land use, and how the composite scores are computed, are possible, and many other applications of ecological footprint analysis have been conducted (Deustch et al. 2000). Foot- print summaries also can be done in a variety of other ways, such as simply computing the percent area or other response variable that is influenced by each land use, and by the composite of all land uses, as opposed to assigning scores. Recent applications of human footprint analyis in sagebrush ecosystems were conducted by Weller et al.

(2002), Leu et al. (2003), Rowland et al. (2005), and Thomson et al. (2005).

Human footprint analysis provides at least 3 major advantages in regional assessments: (1) it provides a comprehensive analysis of threats; (2) it is relatively easy to map and compute results; and (3) the scoring process provides clear discrimination among areas that are strongly versus weakly affected by human land uses that pose threats to native species and habitats. However, there are disadvantages as well: (1) the areas of influence surrounding each fea- ture or land use are difficult to estimate because of the many knowledge voids about effects by distance; (2) the specific effects on species and habitats often are unknown; (3) the scoring process often is based on hypothesized rather than empirical relations, and represents a ranking of effects rather than actual effects; and (4) the synergies or interactions among multiple threats are typically not considered. Nevertheless, these same disadvantages pose problems for many analyses of multiple threats, thus making human footprint analysis an appealing approach because of its conceptual and computational simplicity. In particular, future applications of human footprint analysis could be improved substantially by considering the synergies and interactions among multiple threats, and by describ- ing or targeting the effects on specified sets of species and habitats. For example, potential effects of global climate change may eliminate up to 80% of the remaining sagebrush in large areas of the sagebrush ecosystem (Neilson et al. 2005), possibly overwhelming the effects of other threats in such areas.

Regardless of the method used to evaluate effects of multiple threats, management designed to mitigate un- desired levels of risk from multiple threats requires substantial experience, collective judgment, and supporting ra-

5 0 PART 1: ASSESSING THREATS

tionale. As described above, the process of calculating habitat area for a given species can be done in a variety of ways in relation to the combination of threats to the species' habitats. The most appropriate process is one that is both ecologically sound and has the most straightforward management implications, particularly in relation to preven- tion of threshold effects. That is, an appropriate summary of habitat area in relation to multiple threats would be a summary that portrays the various combinations of habitat threats in a manner that allows managers to design practices that prevent thresholds from being crossed, from which restoration of habitats may be impractical or infeasible.

The following summary points can aid decisions about how best to combine and map different levels of risks from multiple threats for species' habitats:

Describe the potential cumulative effects of risk from multiple threats, or "collective risk," in a clear and defensible manner. Identify the most severe and the most benign of the potential effects from the multiple threats, to illustrate the range of possible effects. Contrast these extremes with intermediate levels of collective risk to illustrate more plausible effects. Describe potential synergies among multiple threats, and explain how these synergies might be reduced or avoided with appropriate manage- men t. Develop a clinical list of all mitigating actions, their effectiveness, and their costs. Describe trade-offs of resource inputs needed to mitigate the collective risks, versus the benefits of achieving the mitigation. Identify species and associated habitats that may be at greatest risk from the multiple threats. Refine the miti-

gating actions and trade-off analyses based on consideration of these species and their habitats.

8. Form Species Groups to Gener- alize Results Across Species-Regional assessment of vast areas such as an ecoregion typically calls for evaluation of 50 or more species of conservation concern (e.g., Wisdom et al. 2000), and can include hundreds or even thousands of species (e.g., Thomas et al. 1993n, b; Marcot et al. 1998; Groves et al. 2000, 2002; Nachlinger et al. 2001). For land managers, individual attention to 50 or more species can be impractical. To address these inefficiencies, various "shortcut" methods have been proposed to eliminate or reduce the number of individual species that are explicitly considered in an assessment and in subsequent management. Among the more popular shortcuts are (1) umbrella species; (2) surrogate species; (3) focal species; (4) landscape indicators; and ( 5 ) species groups. See Appendix 3 for detailed descriptions of these and other approaches.

In contrast to shortcut methods that use single species or landscape indicators, the use of species groups, as defined by Wisdom et al. (2000), is an explicit attempt to address the needs of both single and multiple species in a hierarchical fashion (Fig. 1.16). In the most optimistic sense, use of species groups, in combination with individual species, may enable managers to (1) address either single- or multi-species needs, depending on objectives; (2) identify regional habitat patterns that affect multiple species similarly: ( 3 ) address the needs of many species efficiently and holistically with the use of regional strategies for the groups; (4) determine how well the regional strategies for groups of species meet the needs of individual species within the groups; and (5) summarize results for

METHODS OF ASSESSMENT-l.llisdc>i?z et ul. 5 1

Families of Groups

Groups of Species

Individual Species FIGURE 1.16. Conceptual framework of using species groups to assess and manage species of conservation concern in an ecoregion (Chapter 7). In this process, information on all individual species of concern is retained and considered for management, but the information is summarized at varying levels (groups of species and "families of groups") for efficient consideration in management. Howev- er, any management direction set for groups of species can be checked as to its effect on individual species.

species and groups at multiple spatial extents to maximize flexibility in the design and implernentation of regional strategies. In the most pessimistic sense, use of species groups may not reflect robust patterns among species, may fail to account for key requirements of individual species, and rnay provide a false sense of confidence for managers unwilling to consider the unique needs of individual species.

Consequently, we recommend the use of species groups in regional assessments in the sagebrush ecosystem, but with the caveat that assumptions about how well the species groups represent the needs of all individual species of concern be tested as part of management implernentation in partnership

with research (Appendix 3). Depending on objectives, species can be grouped by various criteria, such as commonal- ity among habitat associations, life-history traits, or threats to persistence (An- delman et al. 2001, Wisdom et al. 2001) (Chapter 7, Appendix 3). Using the conceptual approach in Fig. 1.16, each species is placed in 1 of 4 example groups (Fig. 1.17), based on the degree to which the species is associated with sagebrush cover types (e.g., nearly ex- clusively, or more broadly with a combination of sagebrush and other cover types).

Placing species in the 4 example groups (Fig. 1.17) can be accomplished in several ways, ranging from simple rule sets to formal analyses such as hierarchical cluster analysis (Wisdom et al. 2000, 2001). The following process is one means of placing species in the 4 example groups, based on a simple rule set to establish the initial groups and cluster analysis to finalize the groups. The rules are based on the degree of a species' dependence on sagebrush versus non-sagebrush cover types. For example, if >75% of the cover types identified as source habitats for a species are sagebrush types, the species is considered a "sagebrush obligate" (Fig. 1.17). By contrast, if 25- 75% of the source habitats for the species are sagebrush types, and the re- mainder dominated by either grasslands or by woodlands, the species is placed in the appropriate group: sagebrush- grassland or sagebrush-woodland (Fig. 1.17). Species not placed using the above rules fall into the category of "sagebrush generalists. "

An alternative rule set is one based on the amount of each cover type used as source habitat by each species in the analysis area, rather than on the number of cover types. For example, if 80% of the cover types identified as habitat for a species are sagebrush cover types, and


Sagebrush-Associated Species

Nearly

i Use Sagebrush

Grasslands

I and Pinyon-

I Use Sagebrush and Many Other

Habitats I Sagebrush Sagebrush- Sagebrush- Sagebrush Obligate Grassland VVoodland Generalist Group Group Group Group

FIGURE 1.17. A conceptual approach for grouping species for assessment at the scale of an ecoregion, based on varying combinations of each species' association with sagebrush in relation to other habitats (see application for the Great Basin in Chapter 7).

20% woodland, but the actual habitat present for the species in the ecoregion is 10% sagebrush and 90% woodland, it may be difficult to justify placing the species in the sagebrush obligate group. Instead, the species may fit more appro- priately in the sagebrush-woodland group (Fig. 1.16). An adaptation of these rules for placing species into groups in the Great Basin is described and illustrated in Chapter 7.

Cluster analysis can provide further insight about similarities in habitat associations among the species (SAS In- stitute, Inc. 1989; Wisdom et al. 2000). Hierarchical cluster analysis allows ex- amination of how each species is joined into groups based on similarities with other species' habitats. Each species constitutes a "group" at one end of a hierarchical tree, until all species are joined together to form 1 inclusive group at the other end. Alternatively, the number of desired groups can be specified. Species membership in each group, while varying the numbers of groups, can be examined in relation to

knowledge of similarities among species' habitats. A statistician or quantitative ecologist is best qualified to conduct the cluster analysis and can assist in interpreting its meaning.

Results of the cluster analysis can be used to adjust membership of species in the groups, and to adjust the number of groups. Species membership in the modified groups can be reviewed by species experts, along with supporting rationale for why species were placed in each group. This process can iterate many times until agreement is reached about the appropriate membership of species in the groups, and about the desired number of groups needed to meet objectives.

In general, land managers want to minimize the number of groups to be dealt with in land use decisions, but ecologists are likewise reluctant to include too many diverse species in the same group. One solution is to establish multiple levels of grouping for regional assessment. ranging from evaluation of individual species, to groups of species,

METHODS OF ASSESSMENT-Wisdot7z et al. 5 3

and to "families of groups" (Wisdom et al, 2000) (Fig. 1-16). In this way, managers can use results for the "families of groups" to establish regional habitat strategies, and ecologists can check the efficacy of the approach for individual species and groups of species within each "family" (Wisdom et al. 2000) .

Other variations on the use of species groups also can be considered (Andel- man et al. 2001, Wisdom et al. 2001). An example is the concept of identifying and managing species of concern according to their sensitivity to human disturbances (Hansen and Urban 1992; Fleishman et al. 2000, 2001; Rowland et al. 2005). Under such an approach, Hansen and Urban (1992) assigned sensitivity scores from 1 (least sensitive) to 3 (most sensitive) in relation to life-history traits of selected birds. Species with more restrictive habitat associations, larger home ranges, extensive migratory patterns, and longer life spans were presumed to be more sensitive to human disturbances, and thus received higher scores. The sensitivity scores for each species' set of life-history traits were then summed, providing an overall ranking of the species' sensitivity to disturbance relative to other species being evaluated.

Fleishman et al. (2000, 2001) used the sensitivity index as 1 of 3 variables to evaluate the utility of species as potential "umbrellas" for other, related taxa in conservation planning. Rowland et al. (2005) further developed the index to evalutate potential sensitivity to human disturbance of 40 species of concern in the Wyoming Basins, deriving sensitivity indices for birds, mamma'is, and reptiles.

By extension, species could be grouped by categories of their sensitivity scores. If a key objective of a regional assessment is to better under- stand the spectrum of potential respons-

es of species to human disturbances, such a process would be an efficient means of grouping species and assessing the associated env~ronmental conditions and threats.

9. Surntnarize Results for Species and Groups a t Desired S p a ~ a l Ex- teats-Results of regional assessments can be summarized across all sagebrush ecoregions, for each sagebrush ecoregion, and for a variety of large spatial extents (areas >200,000 ha) within each ecoregion (Fig. 1.3). Spatial extents within an ecoregion can include hydrological, ecological, and administrative boundaries (Fig. 1.4).

Example hydrological extents include watersheds (fifth hydrologic unit code, with a mean area >200,000 ha for multiple watersheds) or subbasins (fourth hydrologic unit code, with a mean area of approximately 200,000 ha per subbasin). Ecological extents include ecological provinces, such as the 14 provinces established by West et al. (1998) and Miller et al. (1999) in the Columbia Plateau and Great Basin Ecoregions (mean area of approximately 5 million ha per province), or the 13 Ecological Reporting Units developed by Hann et al. (1997) for the Interior Columbia Ba- sin (mean area of approximately 2.4 million ha per Reporting Unit). The Na- ture Conservancy's portfolio sites for conservation (Groves et al. 2000, Nach- linger et al. 2001) are another example of useful ecological extents at which results of regional assessments can be summarized.

Administrative extents include the national level, encompassing all areas managed by BLM and FS across all sagebrush ecoregions, as well as intermediate and finer administrative extents, ranging from BLM State Offices or FS Regional Offices to field units of both agencies (Fig. 1.4). Findings summarized to administrative extents can be crudely cross-referenced to summaries


Habitat Condition

Interior Columbia

FIGURE 1.18. Habitat network characterized for sagebrush-associated species in the Interior Columbia Basin (fi-om Wisdom et al. 2002~). Watersheds in Condition 1 contain habitats that have undergone little change since the historical period. Watersheds in Condition 2 are characterized by habitats of moderate resiliency and quality. Watersheds in Condition 3 contain habitats of relatively low abundance or low resiliency and quality. Watersheds with extirpated habitats are defined as those containing habitat historically but no habitat currently. Watersheds with rare habitats are defined as those containing >O% but <I% of habitat area.

made at hydrological and ecological extents, and vice versa; this can be accomplished by selecting administrative, hydrological, and ecological extents that are similar in size and boundaries. Note, however, that different results should be expected from results summarized for different types of spatial extents, owing to differences in size and boundaries.

Summarizing results for individual specles and for species groups at the desired spatial extents is 1 of the final steps in a regional assessment. Wisdom et al. (2002~) summarized habitat conditions for groups of species for each watershed in the Interior Columbia Ba- sin (Fig. 1.18). Each watershed was

characterized as 1 of 3 conditions for each species group. Watersheds in Con- dition 1 contained habitats that have undergone little change in quality or abundance since the historical period. By contrast, watersheds in Condition 2 or 3 contained habitats that have changed from historical conditions, but in different ways. Watersheds in Condition 2 had habitats of high abundance but moderate resiliency and quality. Water- sheds in Condition 3 contained habitats of low abundance or low resiliency and quality, and contained large spatial gaps where habitat had been lost (Fig. 1.18).

This map of habitat conditions for groups of species is referred to as a

METHODS O F ASSESSMENT-IVi.rdon7 ei al. 55

"habitat netwrork" (Wisdom et al. 2002~) . This network, or mosaic, of habitat conditions for each species group appears to have high utility for regional planning (USDA Forest Ser- vice and USDI Bureau of Land Man- agement 2000). For example, information about the network could be used by managers as guidance to maintain habitats in a relatively unchanged state from historical conditions (Condition I), to improve habitats where quality and resiliency have declined (Condi- tions 2 and 3), to restore habitats in areas of extirpation or low abundance (Condition 3), and to improve connectivity where spatial gaps have developed (Condition 3). See Hobbs (2002) for a detailed discussion regarding the use of habitat networks for conservation planning.

A similar network could be characterized at desired spatial extents for groups of sagebrush-associated species within an ecoregion. For example, for a given species group, each watershed in an ecoregion could be characterized as 1 of 4- conditions: (I) habitats are of high abundance and generally at low risk of being lost to regional threats; (2) habitats are of high abundance but mostly at moderate or high risk of being lost; (3) habitats are of low or moderate abundance and mostly at moderate or high risk of being lost; and (4) habitats are of low or moderate abundance but generally at low risk of being lost. Wa- tersheds in Condition 1 may require little or no management change. By contrast, watersheds in Conditions 2 and 3 may require careful management attention to reduce the risks of habitat loss. Moreover, watersheds in Conditions 3 and 4 may need attention in terms of increasing the abundance of habitats. Regional strategies could be developed for watersheds in each condition to identify the appropriate conservation and restoration prescriptions needed to

meet management goals for the species group. In turn, spatial priorities for al- locating limited resources for conservation and restoration could be mapped for each watershed based on the conditions.

10. List Major Assutnptions, Limi- tations, and Guidelines for Manage- meat-Regional assessments have sometimes been criticized as being too coarse to reflect ecological patterns and processes that affect species of concern, and consequently, as having little management utility. While particular criticisms are warranted for any assessment, regional or local, criticisms of regional assessments as being "too coarse" often lack context regarding the objectives the assessment is intended to serve. For example, results from regional assessments may not be too coarse to meet evaluation objectives for large spatial extents such as an ecoregion or ecological province (see discussion by Groves et al. 2000, 2002). Alternatively, the same assessment data may indeed be too coarse for use in a local area <200,000 ha in size, which often represents the area encompassed by local management projects.

These points suggest that all assessments, regardless of scale, require an explicit listing of assumptions, limitations, and guidelines for appropriate management use as a fundamental step in the process. The assumptions, limitations, and guidelines listed in Chapter 9 apply to management use of results from regional assessments of sagebrush habitats. Example points from Chapter 9 are summarized below. These points are not comprehensive, and many others can be added to reflect the specific qual- ities of a given regional assessment for species of concern.

Results from a regional assessment will vary with the type of spatial extent used in the evaluation. Selection


of ecological, hydrological, adn~inis- trative, or other boundary types, as well as the size of the assessment area that is chosen, must be based on explicit rationale that supports the assessment goals. The number and type of species of concern identified for regional assessment will vary by the criteria and methods used for their selection. We outlined criteria and methods that are inclusive because (1) this ensures that all potential species of concern are identified; and (2) a more comprehensive set of species of concern ensures that a wider range of associated habitats can be assessed and considered in management. Current range maps do not depict the spatial structure of populations within each species' range. Current maps can thus over- or under-estimate boundaries of the actual range. As a result, the amount and area of habitats used by a species may likewise be over-or under-estimated in regional assessments. Additional research is needed to improve estimates of species' ranges. The cover types associated with each species, identified here as "source habitats," are assumed to contribute to persistent populations, but other, additional factors beyond abundance and configuration of these habitats also influence whether a population is growing, declining, or stationary. When the effects of non-vegetative factors on species of concern are known or can be estimated in a plausible manner, this information provides an important, complementary component to evaluation of source habitats. When coarse pixel or polygon sizes are used to rnap cover types, such as a 90-m X 90-rn pixel size used for the land cover rnap encompassing the sagebrush ecosystem (Comer et al.

2002), the resulting habitat estimates (e-g., amount, fragmentation, connectivity) are based on the dominant plant species present in the overstory of each pixel or polygon. As such, these estimates do not reflect the quality of understory vegetation that may render some cover types unsuitable as habitat. Future availability of continuous coverage, higher-resolution maps, such as those based on a I-m X I-m pixel size, and that encompass the entire sagebrush ecosystem, will help address this current problem. Habitat estimates and associated threats are likely to be positively correlated with trends in populations of the associated species, but the specific level of correlation will vary with other factors not considered in an assessment. Habitat estimates of amount, fragmentation, connectivity, and patch size, using a coarse-pixel resolution such as the 90-rn land cover map currently available for the sagebrush ecosystem, are of sufficient accuracy to meet regional assessment goals when results are summarized to spatial extents of the ecoregion, ecological province, subbasin, or other large areas generally >200,000 ha (Hann et al. 199'7, Wisdom et al. 20026,~) (Fig. 1.3). These estimates will be less accurate when summarized at smaller spatial extents, and are not designed for use in more local analyses.

0 Cover types that occur in small or linear patches often are underesti- mated in relation to their true spatial extent. Consequently, linear features such as narrow riparian strips and smaller streams cannot always be mapped accurately at the 90-rn X 90- m pixel size used for the current land cover map. Species that depend primarily on habitats associated with

METHODS OF ASSESShIENT-Wisdo~n et nl. 5 7

such linear features should not be included in regional assessments.

0 Higher uncertainty is associated with habitat and threat estimates for plants and invertebrates versus vertebrates, owing to less research conducted to date on plants and invertebrates (Bonnet et al. 2002). Higher uncertainty also is associated with habitat and threat estimates for reptiles and amphibians than for birds or mammals, owing to less research conducted to date on herptiles (Wisdom et al. 2002d). Specific effects of each threat on individual species typically are not well known. New research is needed to evaluate many of these potential effects on individual species. However, general effects of many threats have been documented for the more common sagebrush habitats used by many species, thus providing a stron- ger basis and inference space for multi-species assessments, as outlined here, as opposed to single-species or focal-species assessments. Some threats are not easily measured and mapped at regional scales, even when they are pervasive on landscapes. Threats more difficult to measure and map include processes that typically are diffuse and thus difficult to measure through remote sensing methods, even when their effects are widespread. Examples include effects of ungulate grazing, predation, off- road recreation, and herbicides. Ad- ditional forms of data collection are needed-beyond remote sensing methods-when conducting a threats assessment for these types of threats. The combined effects s f multiple threats, especially the potential syn- ergy among threats, are not well known. This is particularly true for cumulative effects analysis such as human footprint evaluations. New research is needed to improve knowl-

edge of such cumulative effects on sagebrush habitats and species. Management use of results from an assessrnent of species groups is a coarse-filter approach that can be effective as regional context for local planning, analysis, and implementation. Coarse-filter management assumes that managing an appropriate amount and arrangement of all rep- resentative land areas and habitats will provide for the needs of all associated species in a group (Appen- dix 3). Coarse-filter approaches, such as those based on regional assessment of species groups, need to be evaluated in relation to results for individual species (Fig. 1.16). Regional strategies based on an assessment of species groups can then be improved through a number of iterations of the strategy's development that improve the effectiveness of the coarse-filter approach on individual species in the groups. New research is required to validate key patterns and processes identified in a regional assessment that have strong management implications, but may lack empirical certainty. If validation research is not implemented to address the major sources of uncertainty associated with major results of a regional assessment, the credi- bility of the assessment and its management uses could be seriously questioned. Results from regional assessments provide regional context for designing local conservation and restoration practices, but are not a substitute for local analysis and local management decisions. Likewise, the effectiveness of addressing regional threats and regional habitat problems depends on effectively addressing these problems through a combination of regional and local management plans.


Additional Methods for Spatial and Accordingly, we suggest that frag- Temporal Analysis mentation, connectivity, and patch size

The 10 analytical steps described earlier are not comprehensive. Instead, these steps should be considered an essential starting point, or foundation, for a regional assessment. These steps can be augmented in a variety of ways with other analyses that add detail and depth to the regional assessment in relation to the targeted species.

The following sections identify additional, complementary means by which regional assessments can be used to evaluate conditions for species of concern. These methods are challenging to use, however, in that they require empirical data that are currently lacking for many species. Consequently, it is important to identify the major assumptions on which such analyses are based, both for testing in research and for un- derstanding their implications in management.

Fragrzentntion, conrzectivity, and patch size ana l~ses

Fragmentation, connectivity, and patch size are important concepts of landscape and population ecology that have direct relevance to regional assessments. Unfortunately, these terms are used in myriad ways and often poorly defined by users, leading to rnisinterpre- tation and loss of utility (Tischendorf and Fahrig 2000a, h; Haila 2002; Vil- lard 2002). For example, each term can be defined in relation to habitats, populations, or both. kforeover, each term can be used generically as a landscape metric, or applied specifically to a particular species or set of species at different scales (Tischendorf and Fahrig 2000a, 6; Fahrig 2002: McGarigal and Cushman 2002). Consequently, formal definitions for use in regional assessments are needed to avoid misinterpre- tation.

be defined and used in regional assessments to evaluate the configuration of habitats relative to each species9 needs, or to groups of species that respond similarly to measures of configuration. Simply applying these concepts on a landscape, without consideration of how species actually respond to these measures, can produce highly mislead- ing results (Vos et al. 2001). That is, populations of species may be fragmented, connected, or arranged in patches in different ways in response to these landscape metrics, and thus inter- pretation is species-specific or specific to a group of species whose responses to these metrics are similar (Sondgerath and Schroder 2002, Cehring and Swi- hart 2003). That as context, the components of habitat configuration can be thought of as the amount of habitat edge relative to area (fragmentation), habitat arrangement relative to a species' capability to move across the arrangement (connectivity), and size of individual habitats used by a species (patch size). Such measures are useful for regional assessments because they depict the "patterning" of habitats across large spatial extents that can affect species in a variety of ways (Knick and Rotenber- ry 1995, 2002; Donovan and Flather 2002). Definitions for use of these terms to evaluate habitat configuration in regional assessments follow:

Fr-agmentation: The degree to which habitats are subdivided into smaller and more isolated patches, where subdivisions are measured by the relation between the length of habitat edge and the size of habitat patches in relation to a species' use of this measure. Long length of habitat edge relative to small size of habitat patches denotes high fragmentation, while short length of edge relative to large

size of patches indicates low frag- tial extents, the mean or median size mentation. Many variations of this of habitat patches present may be a basic definition are described and useful summary, in tandem with a quantified by McGarigal and Marks display of the frequency distribution (1 995). of patch sizes. Connectiviq: Landscape connectivity is "the degree to which the landscape facilitates or impedes movement among resource patches" (Taylor et al. 1993). Landscape connectivity can be thought of as the degree to which habitats for a species are continuous or interrupted across a spatial extent, where habitats defined as continuous are within a prescribed distance over which a species can successfully conduct key activities (e.g., effective dispersal distance of seeds or juveniles, mean distances moved for foraging, nesting, and brood-rearing), and habitats defined as interrupted are outside the prescribed distance. As an example, Raphael et al. (2001) defined habitats as being "connected" if patches were within the mean dispersal distance for juveniles of greater sage-grouse and other sagebrush-associated species; habitat connectivity was then summarized as the percentage of habitat area that was connected for the species, as measured over millions of ha in each species' range. See Tischendorf and Fah- rig (2000a, 0) for a thorough overview of connectivity measures and concepts, and the many problems associated with its application. Patch Size: The area constituting a separate piece of habitat for a species, where the piece is defined as the pixels of habitat adjacent to one another (pixels touching one another on any side or corner), or the piece is defined by some alternative rule set designed specifically for a species in terms of its selection for, and probability of occupancy of such patches (Knick and Rotenberry 2002, Lee et al. 2002). For watersheds or larger spa-

While the conceptual basis for using these measures of habitat configuration is straightforward, their operational use is not. The following points should be considered if measures of habitat configuration are included in a regional assessment:

Effects of change in habitat configuration are not well documented for most species of concern (Tischendorf and Fahrig 2000a, 6; McGarigal and Cushman 2002). Different species respond in different and sometimes contradictory ways in relation to a given spatial configuration of habitats (Haila 1997). Different landscape models, assumptions, metrics, and scales are required to assess configuration effects on different species of concern, assuming effects are known (Vos et al. 2001, Gehring and Swihart 2003). For sagebrush-associated species, in particular, effects of habitat configuration are not well known. Consequently, we suggest that analyses of habitat configuration be done for example species for which empirical data exist. A gradient of example species could be selected that are known to vary in their response to patch size occupancy, dispersal distances and rates, home range size, and other life-history traits that affect their responses to habitat configuration. Results of fragmentation, patch size, and connectivity analyses will vary with pixel resolution and spatial extent. Use of coarse pixels (Fig. 1.3) results in a "smoothing " o f habitats into fewer patches with larger patch sizes and higher connectivity. Use of fine pixels results in more discrete


mapping of habitats into smaller, less well-connected patches. The appropriate pixel resolution is that most compatible with the specieskcology. For example, a coarse pixel resolution is more appropriate for an animal species that moves over large areas and selects habitats with less discrimination than an endemic plant species with stringent, site-specific requirements. Similarly, use of small spatial extents for a wide-ranging species is likely to be inaccurate, whereas large spatial extents may dilute or obscure meaningful patterns associated with species that occupy small areas. Ap- propriate scaling of the analysis to match the species' life history patterns is essential (Keitt et al. 1997, Vos et al. 2001, Gehring and Swihart 2003). Measures of habitat configuration are nearly always correlated with measures of habitat abundance (Haila 2002). For example, increased habitat fragmentation invariably reflects de- creased habitat abundance. Further- more, simple measures of habitat abundance typically account for substantially more variation in predicting species' extinction and other population responses than measures of habitat configuration (Fahrig 1997, 2002; With 1997; McIntyre and Wiens 1999). Measures of habitat configuration therefore are complementary but secondary to analyses of habitat abundance.

Coutside~-ntion of nolz-ltegetative fnctors aflkcting species of concern

Wisdom et al. (2000) defined source habitats as characteristics of macro-vegetation that contribute to stationary or positive rates of population growth for a given species. This definition implic- itly acknowledges that factors beyond macro-vegetation can. affect population

persistence (Fig. 1.9). Consequently, effective management of habitats must proceed in tandem with management of other factors that affect persistence, Knowledge about effects of non-vegetative factors therefore is an important, co~nplementary component to proper management of vegetation identified as source habitats.

Examples of non-vegetative factors that affect species' persistence include (1 ) ovel--hunting, over-trapping, poaching, excessive collection for the pet or medicinal trades, or other forms of non- sustainable take; (2) high rates of predation, particularly when changes in habitat predispose species to increased predation; (3 ) roads or other human disturbances that act as barriers to dispersal, cause avoidance, or disrupt life cycles; (4) indiscriminate, excessive use of pesticides or other chemicals; and ( 5 ) anomalies of severe weather or other catastrophes. These examples are not inclusive, but illustrate the diversity of factors that may override the effects of beneficial management of habitat.

Lee (2000) and Marcot et al. (2001) developed the use of Bayesian Net- works to integrate the effects of all such variables, biotic and abiotic, which affect species of concern. Raphael et al. (2001) used Bayesian Networks to develop landscape models for a variety of sagebrush-associated species of concern. This form of model performed well as a tool to evaluate landscapes for environmental quality and estimate the probability of regional extirpation for greater sage-grouse (Wisdom et al. 2002b).

Change detection studies

Monitoring how species and habitats change over time, such as done in "change detection" studies, is an irn- portant tool for helping guide and refine management over time. In particular,

METHODS OF ASSESSMENT-Wish2 et nl. 6 1

specification of the desired temporal scale is an important consideration for regional assessments. That is, deciding whether to estimate changes in habitats over time, selecting the proper time periods for estimating such changes (temporal extent), and ensuring that potential biases associated with different methods of estimating conditions at different time periods are reconciled (Noon and Dale 2002). Importantly, using different methods to estimate habitats for each time period will affect the spatial grain and accuracy, in turn affecting estimates of habitat change over time. As with spatial scale, the objectives of a temporal analysis determine requirements for extent and accuracy.

By definition, any analysis of risks posed by threats to species or their habitats (e.g., Figs. 1.11, 1.12, 1.14, 1.15) is a temporal analysis. That is, identifying sagebrush cover types as being at varying levels of risk from a given threat explicitly assumes that such effects will occur at some point in the future, or are occurring at the current time. The time point of analysis needs to be specified (e.g., Table 1.6, Fig. I. 1 I), as risks change with different periods of time over which they are estimated.

The following points may be helpful in considering the use of change detection studies as part of a regional assessment:

Resources needed for change detection studies are substantial: variables of interest must be estimated at multiple points in time, and consistent methods used to analyze differences over time. Evaluations conducted over short time periods may reveal little change in habitat conditions, incorrectly suggesting that change has been minimal. Or, evaluations over short time periods may capture effects of an in-

frequent but large episodic event, falsely suggesting that change has been substantial. By contrast, changes measured over multiple time points, spanning longer time periods, are more likely to reveal past dynamics of habitat change that are easier to interpret.

Different methods often must be used to estimate conditions at different time periods. In general, estimates become increasingly coarse in resolution as one goes farther back in time. By contrast, estimates made closer to the present often rely on the same or similar methods of estimating conditions. Differences in methods used for different time points must be accounted for in the analyses and subsequent inferences.

USING RESULTS IN LAND USE PLANNING

Regional assessments are essential in establishing regional management strategies as context for efficient and credible development and implementation of local land use plans (USDI Bureau of Land Management 2005). At the same time, regional management strategies can be refined with feedback from local planning. The interaction of regional management strategies with local planning fits the concept of "top-down" and "bottom-up" processes (Fig. 1.4). Both processes are essential in dealing with land use issues that are simultaneously regional and local in scale (Groves et al. 2000, 2002).

For example, an ecoregion map of risks to sagebrush habitats and species from transmission lines could be invalu- able in setting regional management strategies (Fig. 1.14). Based on the regional assessment, the regional strategy could focus on management practices designed to mitigate or reduce the high risk of habitats becoming unsuitable from transmission line development.


Such strategies might call for rerouting some proposed transmission lines that pose pervasive effects that are deemed unacceptable to managers.

Alternatively, effective management of sagebrush habitats in relation to transmission line development requires local knowledge of the best management practices deemed to be effective for mitigation. In that way, local management strategies and associated goals, standards, and guidelines are critical for meeting goals of a regional strategy. Moreover, local knowledge can be used to "inform" the regional management strategy about areas where the regional strategy may be more effective than in other areas. Again, this illustrates the adaptive nature of combining "top- down" and bottom-up processes in land management.

Another complementary aspect of regional (top-down) versus local (bottom- up) management strategies is the need to consider species whose habitats can be included in a regional assessment, versus those species' habitats that can be assessed only within local areas. Many species of concern are local endemics, requiring local assessment with the use of fine-scale spatial data or field surveys. Overlaying the results of these local assessments with results for regional assessments is an important part of integrating the needs of local endemics versus species whose needs are assessed over larger areas. Typically, consideration of results from local assessments will allow managers to establish management strategies for small areas, or for specific conditions related to the needs of local endemics. Simultaneous- ly, managers can consider the broad conditions and risks depicted by regional assessments as a complement to local assessments.

Another benefit from regional assessments is the opportunity to project future outcomes and effects of land man-

agement on species of concern. One example is the effects analysis of the risk of species extirpation based on the land management alternatives proposed by the FS and BLM in the Interior Colum- bia Basin (Marcot et al. 2001, Raphael et al. 2001). Projections of future outcomes can be compared against goals for future management, to determine whether the goals will be met under the land management alternatives (USDA Forest Service and USDI Bureau of Land Management 2000).

Finally, results from regional assess- rnents can be used to develop adaptive management plans in relation to strategies, goals, and expected outcomes from future management. In the scientific world, adaptive management calls for management activities to be developed and implemented as experimental treatments, to be tested through large- scale research experiments (Holling 1978, Walters 1986). Such experimental approaches are particularly helpful when the risks posed from various threats are high, and the scientific certainty about how best to manage the risks is low (Walters 1986). Such is the case for management of sagebrush habitats, where conservation and restoration management is a relatively new field, fraught with challenges of addressing the vast spatial and temporal scales needed to achieve effective re- cover y (Hernstrom et al. 2002). More- over, the high degree of technological uncertainty about the effectiveness of sagebrush restoration complicates the challenges of scale even further (West 1999, McIver and Starr 2001). Regional assessments play a key role under such conditions. as a means of synthesizing the best available scientific information available about species of concern and their habitats, summarized in a manner that can be efficiently and credibly dealt with as part of a research-management partnership.

METHODS OF ASSESSMENT-Wisdom et al. 63

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