Climate Change
Salmon evolved into the species of today about six million years ago.1 Some species, such as the fierce-sounding saber-toothed salmon, have been extinct for millions of years. Others survived, adapting to changing climates, floods, droughts, and volcanic eruptions. Salmon are adaptable. They find new habitats and use a wide range of habitat throughout their lives. They have survived extreme weather, natural disasters, and natural climate change. The challenges salmon face now are different.
The earth’s climate is changing faster than salmon can adjust. Salmon need cool and clean water, abundant food, and access to habitats where they can reproduce, feed, grow, and travel. Climate change is threatening all these needs and making the challenges salmon face even harder.
PRESSURE: Warming Temperatures are Altering Salmon Streams
Climate change is threatening the clean, cold water in rivers that salmon need to survive. The average annual air temperature across Washington increased by 1.8 degrees Fahrenheit between 1960 and 2023,2 a trend that scientists expect to continue as carbon dioxide levels in Earth’s atmosphere continue to climb.
Glaciers are vanishing. While they do not provide a lot of water for rivers in much of Washington, seeing them shrink is a reminder that the climate is warming. Mountain snowpacks also are shrinking on average as temperatures increase. Across Washington, the amount of precipitation that falls as snow has decreased 16 percent since 1949, and average freezing levels have risen nearly nine hundred feet. This means less (and warmer) water for streams in spring and summer and higher, more damaging floods in fall and winter. The amount of water in streams in the summer, when young salmon are most at-risk, has become lower in most streams,3 and for longer. Scientists estimate that the amount of water released from melted snow declined 21 percent in the western United States from 1955 to 2016.4
As water from snowmelt decreases and the air warms, water temperatures in streams increase. Water temperatures greater than 64 degrees Fahrenheit stress salmon, and temperatures above 70 degrees can be lethal.5 Without actions to reduce water temperatures, there will be fewer salmon and fewer streams where they can survive.
Scientists estimate that by the 2080s, another 1,016 miles of Puget Sound rivers will exceed 64 degrees Fahrenheit for the entire month of August.6 In the Columbia River, climate change and reservoirs behind dams combine for deadly effect on salmon in some years. In 2015, for example, warm water killed about 380,000 adult sockeye salmon before they reached their spawning grounds; this is almost 80 percent of a large run of 480,000 fish. These events likely will become more common as temperatures increase and the amount of water in streams continues to decrease.
The changing climate also is bringing rain instead of snow to lower mountains in Washington. With more rain, the average amount of water in streams during winter will increase by 25-34 percent by the 2080s, increasing the likelihood of severe flooding.7 Severe flooding becomes catastrophic when floodplains, which are natural storage areas for flood water, are developed for businesses and houses.
As the amount of water in streams changes in amount and season, salmon are being disrupted. More intense floods can destroy redds (salmon nests), destroy logjams and other stream structures, and flush young salmon out of their calm-water habitat, reducing their chance for survival. While some young salmon will survive, many won’t be large enough to catch prey or avoid being eaten.8
The amount of snow in the mountains is decreasing. Scientists project that the average spring snowpack in Washington will decline by 56-70 percent by the 2080s.9
As temperatures warm, the point that rain turns to snow moves higher up the mountain, decreasing the snowpack. Salmon count on plentiful snowpack to melt and deliver cool, clean water in the summer and during droughts. Less snowpack means less water. Less water means warmer water. Both threaten salmon and salmon recovery.10
PRESSURE: Climate Change in the Ocean
Human activities have resulted in record-breaking levels of carbon dioxide in the atmosphere and in the oceans.11 Excess carbon dioxide is absorbed by the ocean, forming carbonic acid, which has increased the average ocean acidity level by 30 percent since the Industrial Revolution.12
Carbon dioxide in the air mixes with ocean water to create carbonic acid, making the ocean more acidic. Increased acidity damages the plankton that salmon eat, especially when salmon are young. Excess carbon dioxide also can change the way salmon use their sense of smell to find food, avoid being eaten, and find their natal streams.13
The warmer climate also impacts ocean temperatures. The average surface water temperatures off Washington’s coast have been warming during the past fifty years.14 Warmer water has fewer nutrients and less oxygen than colder water and is not as good for salmon. For example, warmer water cannot support the types of food that young salmon need to thrive, which means that fewer young salmon grow to adulthood. Salmon have demonstrated that they can adapt to a changing environment, but climate change is speeding up these changes, and when combined with damaged streams, salmon struggle to adapt.
PRIORITIES AND PROGRESS
The climate crisis requires immediate action on two fronts: reduce greenhouse gasses that cause climate change and prepare people, communities, and salmon for a changing climate. In 2021, Governor Jay Inslee signed the Climate Commitment Act into law, committing to reduce Washington’s greenhouse gas emissions by 95 percent by 2050.15 Even with actions taken in Washington, temperatures likely will continue to rise unless similar action happens around the world. So, Washington must take steps to mitigate and adapt to the new reality, for people and for salmon.
Climate Resiliency
Several Washington State grant programs focus on reducing the effects of climate change on salmon. The Salmon Recovery Funding Board applicants to address climate resiliency in their grant applications. The innovative Floodplains by Design grant program supports floodplain reconnection and streambank protection, which can reduce the impacts of climate change. The Washington Legislature recently dedicated funding to improve riparian habitat (forests along waterways) throughout the state, which helps to maintain cool, clean water on which salmon depend.
The Washington Legislature supported programs in the 2023-2025 biennium to increase climate resilience by investing nearly $80 million to build community resilience, providing $120 million for water supply and drought response in the Columbia River basin, and accelerating streamflow restoration with $45 million in new investments.
In some watersheds, hydropower dams can benefit salmon by keeping water cool in summer and preventing damaging floods in the fall and winter. Federal and state agencies responsible for protecting salmon negotiate management of dams to keep salmon safe. In other areas, where dams slow flow and allow water to warm, dam removals may provide relief for overheated salmon.
Climate change is threatening the clean, cold water in rivers that salmon need to survive.
Climate Change Affects Salmon at all Life Stages
Salmon are affected by climate change throughout their lives. In the winter, less snow in the mountains, earlier snow melt, and heavier rain increase the number and severity of floods. Strong floods hit salmon hardest when they are young by scouring riverbeds and riverbanks and stirring up sediment that can bury and suffocate salmon eggs in gravel. The strong floods also can flush young fish downstream before they are ready, leading to more deaths. In the summer, less water and warmer water in streams harms both young and adult salmon. Young salmon that spend a year or more in freshwater must find cooler water, avoid getting trapped in isolated pools, and avoid predators. For adults returning to spawn, the warm waters can hinder migration upstream, increase disease, increase
vulnerability to predation, and kill them directly if they get trapped in warm water.
Banner photograph by Angela-Schwart, Unsplash
River photography of the Nisqually River eroding the banks under a road
Ocean photograph by Alice Rubin, Recreation and Conservation Office
1Waples, Pess, and Beechie (2008) Evolutionary history of Pacific salmon in dynamic environments. Evolutionary Applications. Vol 1. 189-20
2Office of the Washington State Climatologist. (2024) PNW Temperature, Precipitation, and SWE Trend Analysis Tool. https://climate.washington.edu/climate-data/trendanalysisapp/ Accessed on September 25, 2024.
3Shedd, J. (2020) Unpublished analysis of 60-day low-flow data from 47 U.S. Geological Survey gages. Washington Department of Ecology, March 23, 2020.
4Mote, P.W., Li, S., Lettenmaier, D.P., Xiao, M., and Engel, R. (2018) Dramatic declines in snowpack in the western US Climate and Atmospheric Science (1).
5Mauger, G.S., Casola, J.H., Morgan, H.A., Strauch, R.L., Jones, B., Curry, B., Busch Isaksen, T.M, Whitely Binder, L., Krosby, M.B., and Snover, A.K. (2015). State of Knowledge: Climate Change in Puget Sound. Report prepared for the Puget Sound Partnership and the National Oceanic and Atmospheric Administration. Climate Impacts Group, University of Washington, Seattle. http://cses.washington.edu/picea/mauger/ps-sok/PS-SoK_2015.pdf Accessed December 12, 2022.
6Mauger, G.S., Casola, J.H., Morgan, H.A., Strauch, R.L., Jones, B., Curry, B., Busch Isaksen, T.M, Whitely Binder, L., Krosby, M.B., and Snover, A.K. (2015). State of Knowledge: Climate Change in Puget Sound. Report prepared for the Puget Sound Partnership and the National Oceanic and Atmospheric Administration. Climate Impacts Group, University of Washington, Seattle. http://cses.washington.edu/picea/mauger/ps-sok/PS-SoK_2015.pdf Accessed December 12, 2022.
7Snover, A.K., Mauger, G.S., Whitely Binder, L.C., Krosby, M., and Tohver, I. (2013) Climate Change Impacts and Adaptation in Washington State: Technical Summaries for Decision Makers. Climate Impacts Group, prepared for the Washington State Department of Ecology by University of Washington Climate Impacts Group.
8Crozier, L., Mcclure, M., Beechie, T., Bograd, S., Boughton, D., Carr, M., Cooney, T., Dunham, J., Greene, C., Haltuch, M., Hazen, E., Holzer, D., Huff, D., Johnson, R., Jordan, C., Kaplan, I., Lindleyid, S., Mantua, N., Moyle, P., and Willis-Norton, E. (2019). Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem. PLoS ONE 14(7).
9Snover, A.K., Mauger, G.S., Whitely Binder, L.C., Krosby, M., and Tohver, I. (2013) Climate Change Impacts and Adaptation in Washington State: Technical Summaries for Decision Makers. Climate Impacts Group, prepared for the Washington State Department of Ecology by University of Washington Climate Impacts Group.
10Crozier, L., Mcclure, M., Beechie, T., Bograd, S., Boughton, D., Carr, M., Cooney, T., Dunham, J., Greene, C., Haltuch, M., Hazen, E., Holzer, D., Huff, D., Johnson, R., Jordan, C., Kaplan, I., Lindleyid, S., Mantua, N., Moyle, P., and Willis-Norton, E. (2019). Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem. PLoS ONE 14(7).
11Lan, X., Tans, P. and Thoning, K.W. (2022) Trends in globally-averaged CO2 determined from National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory measurements. Version 2022-12 NOAA/GML https://gml.noaa.gov/ccgg/trends/ Accessed December 13, 2022.
12Washington State Blue Ribbon Panel on Ocean Acidification (2012). Ocean Acidification: From Knowledge to Action, Washington State’s Strategic Response. Publication no. 12-01-015. H. Adelsman and L. Whitely Binder (eds). Washington Department of Ecology, Olympia, WA. https://fortress.wa.gov/ecy/publications/documents/1201015.pdf Accessed on November 9, 2020.
13Williams, C.R., Dittman, A.H., McElhany, P., Shallin Busch, D., Maher, M.T., Bammler, T.K., MacDonald, J.W., and Gallagher, E.P. (2019). Elevated CO2 impairs olfactory-mediated neural and behavioral responses and gene expression in ocean-phase coho salmon (Oncorhynchus kisutch). Global Change Biology 25(3).
14Jacox, M., Alexander, M., Mantua, N., Scott, J., Hervieux, G., Webb, R., and Werner, F. (2018). Forcing of Multiyear Extreme Ocean Temperatures that Impacted California Current Living Marine Resources in 2016. Bulletin of the American Meteorological Society. 99(1).
15Climate Commitment Act (Engrossed Second Substitute Senate Bill 5126), Chapter 316, Laws of 2021. https://lawfilesext.leg.wa.gov/biennium/2021-22/Pdf/Bills/Session%20Laws/Senate/5126-S2.SL.pdf?q=20221212174607 Accessed December 12, 2022.