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Determining Extinction Risks of Chinook Salmon Due to Climate Change

We conduct Population Viability Analysis of cumulative climate impacts across the life cycle of Chinook salmon.

We use population dynamic models to calculate the cumulative effects that influence Chinook salmon extinction risk. These statistical models integrate multiple climate-related impacts that affect salmon throughout their life cycle. 

a circle with arrows showing the life cycle of salmon and which life stage is susceptible to climate drivers such as summer temperatures, upwellings, dams, and river flow
Credit: NOAA Fisheries


Known as life cycle models, these simulations rely on detailed studies of individual life stages and projections of future climates. They help quantify the potential impacts of climate change and specific proposed mitigation actions such as dam operations or habitat restoration changes. This information supports decisions on the risk imposed by federal actions through environmental impact statements under the National Environmental Policy Act and biological opinions under the Endangered Species Act.  

Our models project that Snake River spring/summer Chinook salmon populations will decline dramatically in the coming decades. This decline is due primarily to rising sea surface temperatures and changes in river and stream temperatures and flows. Consistent with these projections, we have already seen record-low returns of salmon species across the West Coast in response to the marine heat wave of 2014-2016.

graphs showing decline in creek rivers
Credit: NOAA Fisheries



eight graphs showing the number of spawners in 8 populations over time, from 2020 to 2089, for Camas Creek, Loon Creek, Sulphur Creek, Valley Creek, Big Creek, Marsh Creek, Bear Valley Creek, and Secesh River. On average, the number of spawners stays constant over time but when climate change forcing is imposed, all populations rapidly decline below the quasi-extinction threshold.
This graphic shows the simulated number of spawners in eight populations over time, from 2020 to 2089. When the climate is assumed to be stable with historical levels of variability, individual simulations show variability but, on average, stay constant over time (blue line and polygon). However, when climate change forcing is imposed, either under the RCP 4.5 (light orange) or RCP 8.5 (dark orange) emissions scenarios, all populations rapidly decline below the quasi-extinction threshold. Credit: NOAA Fisheries
graphic showing that percentage of spawning Chinook adults declines rapidly in the marine stage as oceans warm, possibly due to prey decline, competition, or predation.
This graphic shows how much adult abundance changed from the 2020s to the 2060s across many simulations (the boxes show the interquartile range of results and whiskers show the more extreme results) and scenarios (climate change imposed at only the life stage indicated on the x-axis). The portion of the box that is red shows how many simulations resulted in population declines vs. population increases (blue). Credit: NOAA Fisheries

We projected the most dire effects for the marine life stage. Our current work focuses on the interspecific dynamics that affect marine survival. We build a set of conceptual, statistical, intermediate complexity, and ecosystem end-to-end models to fully capture our understanding of these relationships. The models explore how climate will alter the marine environment and management tools to mitigate these effects on salmon.  

More Information

Pacific Salmon Climate Impact Research in the Pacific Northwest

Last updated by Northwest Fisheries Science Center on June 30, 2021