Download Long-term changes in environmental characteristics required by

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).