Climate change will greatly affect salmon – a culturally and economically significant
resource – across all life stages, both in freshwater and saltwater, as a result of changes in the timing and volume of streamflow and ocean acidification. Projected increases in winter flooding, decreased summer and fall stream flows, and warmer summer water temperatures will further degrade freshwater and estuary salmon habitat. The duration of periods that cause thermal stress and migration barriers to salmon is projected to at least double and perhaps quadruple by the 2080s for most streams and lakes, which will increase the rates of pre-spawn mortality for Chinook salmon and steelhead trout. These changes will cause severe problems for our already stressed salmon stocks, including federally protected stocks listed under the Endangered Species Act and will likely lead to widespread violations of water quality standards adopted under the Clean Water Act. Although salmon have been able to adapt to great changes in climate and environment in the past, maintaining diversity in salmon populations will be key to the survival of the species.

Figure: Salmon life cycle and climate change. Salmon have a unique life cycle that exposes them to the effects of climate change across many seasons and habitats. The red boxes explain how projected temperature and hydrologic changes may impact salmon during various phases of their life cycle.

For more information about climate change impacts in the Pacific Northwest, visit the University of Washington's Climate Impacts Group.