Using Spatially Explicit Models to Assess Potential Effects of Climate Warming on Native Salmonids in the Northern Rockies

Climate change is rapidly altering the biodiversity of aquatic ecosystems worldwide. Trend data indicate that the Northern Rocky Mountains are experiencing earlier and more rapid snowmelt in the spring, warmer drier summers, increased winter flooding, and extensive loss of snow and ice masses. These changes are likely to shift patterns in distribution, abundance, and phenology of many salmonid species. Understanding how species and habitats are likely to respond to climate warming is, therefore, critical in developing effective conservation and adaptation strategies for freshwater systems. We developed high-resolution, spatially explicit models to predict changes in thermal and hydrological regimes for native salmonid habitats and used climate change simulations to quantify potential exceedance of critical thresholds associated with increasing air temperature trends. Model predictions suggest that a warming climate will result in a significant loss of critical habitat for migratory salmonids, including the threatened bull trout. Furthermore, these changes may provide habitat conditions that favor introduced species, such as introduced rainbow trout which hybridize with native westslope cutthroat trout.  Finally, we present a new spatially-explicit simulation framework for demogenetic (genetic and demographic) vulnerability mapping of salmonid populations in riverscapes to quantify how changes in the stream environment affect functional connectivity patterns.  Spatially-explicit models combining forecasts of habitat conditions and demogenetic impacts are promising tools to guide conservation and management actions in the face of climate change.