Climate Shield Cold-Water Refuge Streams for Bull Trout

Climate change and species invasions raise fears of Bull Trout extinction from much of its historical range this century. Using crowd-sourced biological datasets and high-resolution NorWeST temperature scenarios, we delineate invasion resistant climate-refuge streams for Bull Trout populations across the northwestern U.S. This poster shows the probability of Bull Trout occurrence under two climate scenarios (1980s and 2040s) within >5,000 discrete stream habitats where summer temperatures were < 11ºC (cold enough to preclude Brown Trout and Rainbow Trout). Bull Trout probabilities were predicted from a logistic regression model developed from 512 cold-water streams (classification accuracy = 78%; AUC = 0.83). Application of the model to the universe of cold-water streams revealed ~300 with Bull Trout probabilities >0.9 in the 1980s scenario. In the 2040s scenario, the number of >0.9 refuge streams declines to ~100 but Bull Trout do not appear threatened with regional extinction in the foreseeable future. Most refuge streams occur on public lands where only a small portion currently has protected status (~15%) in Wilderness Areas or National Parks. Forecasts about refuge locations can enable their protection, be used to rally support among multiple stakeholders, and improve the odds that many populations are conserved this century.