Modeling pika presence in the western US:
Subregional variation and climate change implications
Polly Buotte and Jeffrey A. Hicke, Department of Geography, University of Idaho
Photo by Nature Pics
Photo by Nature Pics
1. Introduction
Temperatures have increased during the past century and projections predict additional warming in the coming decades, with substantial implications for human and natural
ecosystems. American pikas (Ochotona princeps) may act as early indicators of climate change because of their sensitivity to temperature and because their mountain habitat is
expected to experience large changes in climate. However, climate conditions vary considerably across the range of pikas in the US. Our objectives were to evaluate the stability of pikaclimate relationships across geographic subregions in the western US, and compare the future probability of pika presence among models given climate change projections.
15
20
25
30
35
Summer maximum temperature (Deg C)
Pika presence locations and
subregional boundaries
3a. Results
1.0
0.0
0.0
-15
-10
-5
0
5
0.5
Probability of occurrence
1.0
0.5
Probability of occurrence
-20
0
Winter minimum temperature (Deg C)
100
200
300
400
Summer precipitation (mm)
500
0
500
1000
1500
Winter precipitation (mm)
 Models projected decreases in probability of pika presence for future climate projections,
although the magnitude of decrease was highly variable based on decade, emissions
scenario, and subregion
B2 Scenario
100%
80%
60%
40%
20%
0%
2020s
2080s
2050s
Relative decrease
Statistical analysis: MaxEnt framework
 One regional (Westwide) model
 Five subregional models (see map)
 Estimated future probability of pika presence at observed pika presence
locations given climate change projections
0.5
0.0
0.0
0.5
Westwide
Cascades
Great Basin
MS Rockies
N Rockies
Sierra Nevada
10
Relative decrease
Explanatory variables: PRISM1 climate data
 Maximum summer temperature
 Minimum winter temperature
 Total summer precipitation
 Total winter precipitation
Probability of occurrence
1.0
Response variable: pika presence
 One location per 1km grid cell
 Known survey year
1.0
3b. Results (cont.)
 Response curves relating pika presence to climate variables varied among subregions
Probability of occurrence
2. Data and Modeling
100%
80%
60%
40%
20%
0%
A2 Scenario
 Models performed significantly better than random
(binomial test of omission p<=0.004 for all models)
 Variable importance differed among subregions
% Importance
100
80
Sum Tmax
Win Tmin
Sum Ppt
Win Ppt
60
40
20
0
Westwide Cascades
Great
Basin
MS
Northern Sierra
Rockies Rockies Nevada
4. Conclusions
 Relationships between pika presence and climate varied across subregions of the West
 Models that do not consider such variability will likely have lower accuracy
5. Acknowledgements
Pika locations were provided by Gary Beauvais, David Hafner, Connie Millar, Mary Peacock, and natural heritage programs in
California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming for pika data and assistance.
Funding was provided by the USGS National Gap Analysis Program office, the USGS through the Western Mountain Initiative, the NSF
Idaho EPSCoR Program and the National Science Foundation under award number EPS-0447689, and the USDA Forest Service
Western Wildland Environmental Threat Assessment Center.
6. Reference
1 PRISM Climate Group, Oregon State University, http://prism.oregonstate.edu