2-26 SS Climate Trout

 A retrospective examination of five western United States river basins found that even though extended droughts, dwindling water flows, and higher temperatures in rivers and streams are here to stay, management decisions in the next decade will have a powerful – perhaps controlling – effect on how Rocky Mountain trout species will fare with a more rapidly changing climate.

Modeling forecasts consistently have demonstrated that the geographic ranges of Rocky Mountain trout species will shrink by some 20 to 90 percent over the next 50 to 100 years as climate change accelerates in the region. Predicted water temperature increases in high-elevation rivers and streams, coupled with reduced water flows, are certain to add to existing stresses for Rocky Mountain trout. The researchers found that the average annual air temperature had increased across all five of these basins over the last 60 years, that spring snowmelt runoff is also occurring sooner, that streamflows in summer are lower, and that winter flooding is increasing in some areas. Clint Muhlfeld, a USGS scientist and co-author describes one of the ramifications of flooding: “Because we are seeing an increase in the frequency,  intensity and magnitude of  these fall flooding events, that is problematic for  bull trout because their nests or reds could be scoured.” Under a rapidly changing climate of the Rocky Mountains, the authors wrote, many trout populations and species will be able to adapt, but others, overwhelmed by future changes, will not survive.The authors emphasized that it is still early enough that fast-acting, proactive management decisions will minimize losses of these economically and ecologically important trout populations during this transitional century.