Predicting climate change impacts on river ecosystems and salmonids across the Pacific Northwest: Combining vulnerability modeling, landscape genomics, and economic evaluations for conservation

Science Center Objects

Salmonids – a group of coldwater adapted fishes of enormous ecological and socio-economic value – historically inhabited a variety of freshwater habitats throughout the Pacific Northwest (PNW). Over the past century, however, populations have dramatically declined due to habitat loss, overharvest, and invasive species. Consequently, many populations are listed as threatened or endangered under the U.S. Endangered Species Act. Complicating these stressors is global warming and associated climate change. Overall, aquatic ecosystems across the PNW are predicted to experience increasingly earlier snowmelt in the spring, reduced late spring and summer flows, increased winter flooding, warmer and drier summers, increased water temperatures, and expansion of invasive species. Understanding how the effects of climate change might influence habitat for native salmonid populations is critical for effective management and recovery of these species.

Scientists at the USGS and University of Montana are using novel modeling techniques and empirical data to study how climate change may drive landscape scale impacts that affect freshwater habitats and populations of key salmonid species (bull trout, cutthroat trout, and steelhead) throughout the PNW. Results show strong linkages between climatic drivers – temperature and flow regimes – and the distribution, abundance and genetic diversity of native salmonids across the PNW. Specifically, warming temperatures and shifting flow regimes are expected to fragment stream systems and cause salmonids to retreat upstream to headwater areas, thereby decreasing fish population abundance and genetic diversity – both of which are critical for persistence in a changing landscape. Climate-change-induced periods of decreasing spring snowmelt and increases in stream temperatures are likely to decrease native biodiversity by fostering cross-breeding between invasive and native trout species. The study is also developing new frameworks for assessing the vulnerability of multiple freshwater species to climate change and other stressors in complex stream networks, which will aid managers in pro-actively implementing conservation programs to increase resiliency and adaptive capacity of aquatic species. Finally, results of this project are helping to improve the Riverscape Analysis Project (RAP; http://rap.ntsg.umt.edu), which offers a new and powerful web-based platform to aid conservation practitioners with assessing the vulnerability of species under climate change.

 

Funding: USGS Northwest Climate Science Center

 

Collaborators: University of Montana (Drs. Gordon Luikart, Brian Hand, and Alisa Wade)