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Long-term changes in environmental characteristics required by sage-grouse predicted under climate change Principal Investigators: Steven T. Knick, USGS Forest and Rangeland Ecosystem Science Center, Boise, ID Sara J. Oyler-McCance, USGS FORT Science Center, Denver, CO Kristine L. Preston, Center for Conservation Biology, University of California, Riverside, CA Steven E. Hanser, USGS Forest and Rangeland Ecosystem Science Center, Boise, ID Summary Sagebrush (Artemisia spp.)-dominated shrublands are one of the most widespread ecosystems in western North America but also among the most imperiled due to interactions among land use, fire, and exotic plants. Global climate change models predict an accelerated loss of sagebrush due to synergistic feedbacks among disturbance patterns and vegetation response; only 20% would remain under the most extreme scenario of >6° C increase by the end of this century (Fig. 1). Much of the current sagebrush distribution within the Great Northern Landscape Conservation Cooperative (GNLCC) would be lost. The conservation status of Greater sage-grouse (Centrocercus urophasianus), the most visible of >350 plant and wildlife species that depend on sagebrush, recently was determined to be warranted for listing but precluded by higher priorities. Because listing decisions are based partially on a long-term (>100 yr) probability of persistence, predicted habitat changes due to climate change may be sufficiently large to overwhelm current trajectories of landcover change. The GNLCC includes a large number of fringe populations of greater sage-grouse in central Oregon, Idaho, and Montana (Fig. 2). In addition, the Columbia Basin populations of sage-grouse in Washington are spatially and genetically isolated from core regions of the rangewide distribution. Dispersal among these populations may be limited because of environmental or geographical barriers. In the absence of dispersal for recolonization, stochastic events within the population, such as outbreak of West Nile virus, or long-term shifts in sagebrush distribution likely will result in local population extinctions. Our proposed study is designed to identify sage-grouse populations at risk of extinction within the GNLCC based on (1) their relative isolation from neighboring populations and core regions of the sage-grouse distribution and (2) landcover changes predicted under global climate change models. Our first year would be used to: (1) develop models of environmental variables that represent an ecological minimum required by sage-grouse, (2) model changes in sage-grouse distribution or population vulnerability relative to changes in these environmental variables predicted under climate change scenarios, and (3) conduct preliminary analyses of genetic variation within and among sage-grouse populations to determine dispersal probabilities. These products could be embedded within a larger scope of objectives to estimate influences of climate change on sage-grouse that could be funded by additional years through the LCC program or from alternate sources. These results benefit management agencies by focusing regional conservation and land management options in regions likely to sustain long-term sagebrush ecosystems. Background Sagebrush ecosystems are among the most imperiled in North America. Multiple stressors, including interactions among fire, exotic plant invasions, and human land use, have resulted in significant loss, fragmentation, and conversion of landscapes once dominated by sagebrush. In addition, the diffuse effects from global climate change leading to long-term shifts in distribution and dynamics of sagebrush communities add an overarching and potentially more significant stressor to these immediate influences. Total area covered by sagebrush is likely to decline both short- and long-term and range shifts are unlikely either across elevations or latitudes because of current vegetation or geographic barriers (Neilson et al. 2005). Greater sage-grouse recently were considered by the US Fish and Wildlife Service for listing under the Endangered Species status due to long-term population declines. Greater sagegrouse now are classified as a candidate species: listing is warranted but precluded by other priorities. Thus, identifying populations at long-term risk can lead to conservation actions that maintain sage-grouse and sagebrush and help avoid further population declines. An expert panel convened for a structured decision process for a previous listing determination in 2005 emphasized that current trends in loss or conversion of sagebrush were unlikely to cause extinction within the next 60-100 years (USDI 2005). Consequently, climate change becomes more significant as a long-term influence and was identified by one panel member as the primary long-term risk. The panel concluded that changes in sagebrush habitats due to climate change would be negative for sage-grouse. Our objectives are to determine the set of environmental factors that sage-grouse require. Using these derived habitat associations, we then will take predicted sagebrush distributions derived from global climate change models to estimate long-term vulnerability of individual sage-grouse populations within the GNLCC. Relevance to Management Approximately 70% of the current sagebrush distribution within the greater sage-grouse range is public land; the US Bureau of Land Management is responsible for managing half of the sagebrush within the United States. Less than 1% of the sagebrush is within areas protected from land cover conversion. The remaining public land is managed for multiple uses that include livestock grazing, energy development, and recreation. Global climate-change models for sagebrush regions predict more variable and severe weather events (drought, storms), increased levels of atmospheric CO2 and halocarbons, greater fire incidence, higher temperatures, wetter winter seasons, earlier onset and warmer springs coupled with longer summer periods of heat and drier soils that create stress for sagebrush. Consequently, the competitive advantage among plant species will shift from native communities to those dominated either by woodlands at higher elevations, and exotic annual grasslands through the remaining sagebrush range. Only 20% of the current sagebrush distribution would remain under the most extreme increase of 6° C by the end of this century, including very little within the GNLCC (Fig. 1). These changes in plant communities and distribution will require a fundamental shift in actions if management agencies are to continue to provide natural resources and manage wildland fire on public lands over a large portion of the western United States. In addition, restoration options increasingly may be limited because of greater frequency of disturbance and reduced ability of sagebrush communities to respond to treatments. Greater sage-grouse depend on sagebrush throughout their annual life cycle; sagebrush leaves and buds may constitute 100% of their diet during winter. Therefore, sage-grouse are tied closely to local, regional, and range-wide scales of sagebrush distribution. Although widely distributed across 11 states (and 2 Canadian provinces), the spatial structure of sage-grouse may be comprised of a small set of large core populations with numerous small populations interspersed between core regions and along the range periphery (Fig. 2). Numerous small populations of sage-grouse are scattered across the GNLCC including the Columbia Basin population that are spatially and genetically isolated from core distributions. Dispersal among these isolated smaller populations may be limited by distance, geogaphic, or environmental barriers. The long-term viability of these populations may be difficult to sustain given the loss from current habitat trends and predicted shifts in sagebrush distribution. Managers have emphasized the sage-grouse as indicators of ecosystem health. Considered an umbrella species, strategies to improve habitat make an implicit assumption that benefits will extend to other wildlife dependent on sagebrush. Therefore, it is important to understand how sagebrush and sage-grouse populations are temporally and spatially interconnected in developing conservation actions. These relationships then can be significant factors in understanding the long-term viability of sagebrush ecosystems. Methods Our primary objective will be to use global climate change models to project future locations and long-term viability of sage-grouse populations within the GNLCC. Our proposed study is based on 2 primary objectives: (1) identify the ecological minimums of environmental variables required by sage-grouse, and (2) use global climate change models to project future locations and long-term viability of sage-grouse populations. Our study area includes the sagegrouse range within the GNLCC, which spans the states of Washington, Idaho, Montana, Wyoming, and Colorado. Sage-grouse within the GNLCC occupy vastly different landscape structures ranging from those dominated by sagebrush to a predominantly agricultural matrix in Washington. Climate change models predict increasing fire and conversion to exotic annual grasslands for much of the study area leading to loss of sagebrush from lower elevations. Ecological Minimums Required by Sage-Grouse.–We propose to develop niche models for greater sage-grouse that identify important habitat relationships and delineate potentially suitable habitat throughout the species’ range within the GNLCC. This analysis will use existing data on environmental variables currently available in GIS format and assembled for previous analyses of sage-grouse and habitat relationships (Johnson et al. 2010l. Studies in Avian Biology). Number of male sage-grouse counted on leks are available from state wildlife agencies. Previous attempts to identify habitat relationships have been confounded by the wide variation in habitats used across different parts of the sage-grouse range. Models based on ecological optimums or correlational relationships often are not applicable to other regions because the new set of characteristics lies outside the inference space of the original data. Consequently, these models fail to accurately track either spatial or temporal changes in environmental conditions (Knick and Rotenberry 1997. Journal of Agricultural, Biological, and Environmental Statistics). Recent analyses to identify the relatively constant set of ecological minimums may be more appropriate for modeling sage-grouse habitats across large regions or through long-term environmental changes predicted by climate change scenarios. We will use the partitioned Mahalanobis D2 niche modeling approach (Rotenberry et al. 2006. Ecology) to identify environmental minimums associated with Greater Sage Grouse occurrence. We will need to construct separate models for populations in subregions that differ substantially in environmental attributes to identify environmental constraints that limit suitable habitat. Alternative models will be developed with different combinations of abiotic and biotic variables and will be evaluated for performance in predicting suitable habitat across regions (Preston et al. 2008. Global Change Biology). The number of subregional models that can be developed will depend on an evaluation of environmental variability and available population data. The results of this subregional modeling will be used to inform development of an overall model generalizing habitat relationships across the GNLCC range of Greater Sage Grouse. Future Sage-Grouse Distribution under Climate Change.-- Changes in distribution of sagebrush land cover under alternate global climate change models already have been mapped (Nielson et al. 2005. Transactions North American Wildlife and Natural Resource Conference; Batchelet et al. 2007. Pew Center on Global Climate Change Report); approximately 12% of the existing sagebrush is predicted to be lost with each 1° C increase. We will use the environmental relationships developed in our initial analysis used to model future sage-grouse distributions with predicted these landcover changes for the GNLCC. We propose to convene a workshop of researchers who currently are working on different components of land cover change under alternate climate change scenarios. The combined expertise that we will assemble will be used to (1) identify and develop the foundation of GIS data for the analyses, (2) create or modify the programming scripts for modeling landcover change, and (3) model the sage-grouse distribution predicted for the new set of environmental conditions. The workshop will include expertise in climate change modeling, vegetation and landscape ecology, sage-grouse biology and response to environmental change, as well as GIS technical skills. Products 1. Manuscript presenting the available data, important environmental attributes, the modeling approach, and preliminary estimates of ecological minimum levels of environmental variables required by greater sage-grouse. 2. Report by workshop participants on projected distributions of greater sage-grouse in response to landcover changes predicted under alternative climate change scenarios. Budget (FY2010) USGS GIS Specialist $7,067 Post-doc (University Coop Agreement) $30,255 Workshop (Travel/per diem) 10 participants $10,000 Subtotal $47,322 Indirect(19% USGS Appropriations) Total $8,991 $56,313 Fig. 1. A. Core areas of the current sagebrush distribution display only those regions in which >85% of the landscape was dominated by sagebrush. B. Distribution of sagebrush predicted under current climate and seven models of future scenarios (Neilson et al. 2005. Transactions North American Wildlife and Natural Resources Conference). Each cell in the map is the sum of alternate models for future climate scenarios predicting that sagebrush will remain in that location. (Miller et al. 2010. Studies in Avian Biology). Fig. 2. Location of 209 components and their importance (dPC) in maintaining connectivity across the range-wide distribution of Greater Sage-Grouse. Number and spatial arrangement of components was evaluated for a dispersal distance of 18 km. (Knick and Hanser 2010. Studies in Avian Biology).