COS 121-8
Using climate-driven population models to assess species risk under climate change scenarios

Thursday, August 14, 2014: 4:00 PM
314, Sacramento Convention Center
Ian A. Pfingsten, Institute for Applied Ecology, Corvallis, OR
Thomas N. Kaye, Institute for Applied Ecology, Corvallis, OR

Oregon’s flora and fauna face a no-analog future climate in which environments are changing faster than many species have ever experienced. Drier and hotter growing seasons are projected for many of Oregon’s native species, of which rare plants and their dependents may be at most risk from this rapid climatic shift. We assessed the potential impact of changing climates on seven rare Oregon natives (Tygh Valley milkvetch, Snake River goldenweed, Green’s mariposa lily, shaggy horkelia, Bradshaw’s lomatium, Cook’s lomatium, and Fender’s blue butterfly) by identifying which aspects of the climate appear to affect the rate of growth, survival and fertility of each species. Our climate drivers consisted of precipitation and evapotranspiration (water loss through evaporation and plant transpiration) summed over combinations of wet and dry seasons and growing and dormant seasons from the year monitored or the year prior. We then projected these species’ population sizes using Climate-Driven Population Models (either count-based, matrix, or integral projection models) into two possible futures: 1.) a future climate from GCM forecasts and 2.) an historic climate from randomly-selected years in the observation period. We used stochastic population growth rates and elasticity analysis to quantify the effects of climate change on populations.


We found that growing season evapotranspiration, which increases with temperature, strongly correlated with many species’ population changes. Currently declining population sizes are projected to decrease even faster with increasing evapotranspiration; while populations that are expected to increase under historic climates are projected to decrease with higher evapotranspiration. For Snake River goldenweed (Pyrrocoma radiata), wet growing season evapotranspiration was negatively associated with plant growth and survival, but positively associated with plant fertility. Of particular importance in the rangeland habitat the species occupies, the populations seem to fare better under climate change when excluded from large mammal herbivory, suggesting an interaction between climate change and disturbance. Although precipitation was a strong correlate with population growth for some species, it was not projected to change much given the average forecasts of our area. Therefore population sizes exhibited minor difference under historic and future climates when precipitation affected vital rates with high elasticities – usually growth and fertility. Unfortunately for these rare species, evapotranspiration is forecasted to increase as future temperatures rise, and that may push some species to extinction faster than predicted under historic climates. Species we assessed as most sensitive to climate change included the goldenweed, mariposa lily, and Fender’s blue butterfly.