Climate change is melting glaciers around the world, worsening sea level rise and disrupting ocean currents and coastal ecosystems. But for some fish, there may be a small ray of hope.
Scientists used computer models to simulate how meltwater would feed new streams and lakes in western North America, and found retreating glaciers could create thousands of miles of new habitat for Pacific salmon by the turn of the century. Understanding where and when these aquatic boundaries emerge will be key to future conservation plans, the researchers reported on Dec. 7 in Nature Communication.
“It shows how climate change fundamentally transforms ecosystems; what is now under the ice is becoming a whole new river, ”said Jonathan Moore, who runs the Salmon Watersheds Lab at Simon Fraser University in British Columbia and is a co-author of the new discoveries. “We can’t just manage current salmon habitat, we also need to think about how we can manage future salmon habitat. “
Ice retreat poses a threat to salmon in some areas. “It can reduce the cooling effect that glaciers have on rivers downstream, so the rivers will warm up during the summer,” Moore said. And as glaciers shrink, less seasonal meltwater is available to feed these rivers in the summer. However, when glaciers melt at the bottom of valleys, they can create new streams. “Rivers will lengthen as glaciers retreat into the valley, and other work has shown that salmon can find and thrive in these newborn river systems,” Moore said.
He and his colleagues studied how this might play out over the next several decades in an area of 623,000 square kilometers (240,542 square miles) stretching from southern British Columbia to Alaska. About 80 percent of the glacier-covered territory in North America’s Pacific mountain ranges lies within the range of the Pacific salmon, which supports subsistence crops and fisheries worth billions of dollars. every year.
Led by Kara Pitman of Simon Fraser University, the researchers identified 315 receding glaciers upstream of existing waterways that could create habitat that salmon could reach. The team then estimated when and where these glaciers would recede under several climate change scenarios. “The next phase was to use predictions of what the land looks like under the ice…[to] imagine the future rivers in these future salmon habitats, ”says Moore.
The researchers calculated that by 2100, Pacific salmon will have access to 6,146 kilometers (3,819 miles) of new waterways. Much of this habitat will come from areas with large, low-lying glaciers near the coast, such as the Gulf of Alaska and the Copper River.
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The team also explored which parts of the aquatic system would provide suitable fish habitat for spawning and rearing young salmon, based on the expected slope of the stream’s channels. They found that approximately 1,930 kilometers (1,199 miles) of booming streams could provide ideal gently sloping conditions for salmon.
As the glacier ice clears, more of the northern landscape will become available for mining and other industries. Predicting where new salmon habitat is likely to open can allow researchers to identify areas in need of protection, the researchers concluded.
However, says Moore, it will be a complicated business. He and his team estimated how much potential habitat melting glaciers could create, but did not analyze how temperature and other environmental conditions might make the new streams more or less attractive to salmon.
Another complication is that salmon do not spend all of their time in freshwater habitats; they are also linked to the sea. “If the ocean is increasingly unsuitable because of the warming which has created new freshwater habitats, it will not result in more salmon populations”, explains Peter Westley, associate professor in the College of Fisheries and Ocean Sciences, University of Alaska. Fairbanks. Westley is co-leader of the Salmon Science Network Initiative, which funded the research, but was not directly involved in the current study. “You need both a suitable ocean and available and suitable freshwater habitats. “
Moore is keen to clarify that the research does not mean salmon will thrive as the Earth warms. Salmon face many climate-related burdens, including marine heat waves, ocean acidification, and extreme floods and droughts. “The document does not suggest that climate change is good for salmon,” Moore said. “It is possible that these local opportunities will be overshadowed by large-scale declines in salmon populations. “
And even if salmon move to new areas where glacial ice has shrunk, there will be consequences for people who depend on the fish.
“The changing distribution of salmon, while beneficial to salmon, does not address the really serious and pressing societal and cultural issues associated with the loss of salmon in some rivers,” Westley said. “It doesn’t help the person who is on their river and sees their salmon go missing because it’s too hot.”
