A strategy and decision-support framework for conserving an isolated fisher (Pekania pennanti) population during an era of change

Background/Question/Methods

The southernmost population of fisher (Pekania pennanti), isolated in the southern Sierra Nevada, California, has been the subject of intensive research and conservation planning due to small size, diverse threats, and controversy concerning forest management actions and increasing wildfire risks. Climate change exacerbates numerous other stressors on the population and its habitat, especially via changing fire regimes. Abundant data from a regional fisher monitoring program and several intensive field studies have supported the development of spatially explicit models of fisher habitat and population characteristics over multiple scales (from regional population distribution and dynamics to sub-home range habitat conditions). Specific models have been developed to map and evaluate functional habitat categories (e.g., foraging, resting, denning, and dispersal habitats) as well as “risky” habitats (where certain mortality factors, such as predators, toxicants, and roadkill, are concentrated). Habitat changes have also been projected into the future using resource selection models built with outputs from process-based simulations of future vegetation and climate variables. We are integrating these diverse models into a spatially explicit, transparent, updateable decision-support system to inform an adaptive fisher conservation and forest management strategy that anticipates likely climate-change effects.

Results/Conclusions

Future projections of fisher distribution, using several CMIP5 future climates, paint a dire picture for this population by the year 2050, as their favored climate envelope shifts and the dense forest conditions they require decline and experience increasingly severe fire regimes. However, large uncertainties in these predictions result from the inability of existing climate models to deal with orographic effects on local temperature and precipitation in rugged, mountainous terrain; and our models do not account for the behavioral adaptability of fishers (e.g., flexible diel activity patterns, catholic food habits, and selection of climate-ameliorating microhabitats). Consequently, we identify likely climate refugia derived from physical terrain features for a range of plausible climate futures in hopes that our adaptive management strategy—guided by our decision-support framework—can help sustain the fisher population despite uncertainties about future conditions. In the meantime, immediate threats to the population, including severe wildfires that can fragment habitat, pervasive rodenticide exposure, and roadkill in important breeding habitats, must be addressed.