A study by researchers at Simon Fraser University found that retreating glaciers in the Pacific Mountains of western North America could produce more than 6,000 kilometers (~3,700 miles) of new habitat. potential of Pacific salmon by 2100.
Researchers modeled the retreat of glaciers under different climate change scenarios – essentially “peeling the ice” off 46,000 glaciers between southern British Columbia and south-central Alaska – to examine the amount of habitat salmon potential that would be created when the underlying bedrock is exposed and new streams flow over the landscape.
Desirable for salmon, in this case, means low-gradient, ocean-accessible streams with retreating glaciers at their source – 315 of the glaciers considered fit that bill.
Under a moderate climate scenario, these glaciers are expected to reveal about 6,150 km of potential new habitat for salmon in the Pacific Mountains of western North America by 2100, a distance almost equal to the length of the river. Mississippi (6,275 km).
“We expect most of the emerging salmon habitat to be in Alaska and the transboundary region on the BC-Alaska border where large coastal glaciers still exist,” the analyst says. space SFU Kara Pitman, lead author of the study. The Gulf of Alaska subregion is expected to see the most gains, a 27% increase in habitat accessible to salmon by 2100.
And once conditions stabilize in newly formed streams, salmon can colonize these areas fairly quickly.
“It’s a common misconception that all salmon return home to the streams where they were born,” says Pitman. “Most do, but some individuals will wander off – migrating into new streams to spawn and, if conditions are right, the population can increase rapidly.”
An example is Stonefly Creek in Glacier Bay, Alaska, where glacier retreat in the late 1970s revealed salmon spawning habitat in the new creek which was colonized within 10 years by pink salmon which quickly reached more than 5,000 spawners.
Climate change poses many challenges to salmon
The researchers warn that while the newly created habitat may be a ray of light for salmon in some places, overall climate change poses serious challenges to salmon populations.
“On the one hand, this amount of new salmon habitat will provide local opportunities for some salmon populations,” says Pitman. “On the other hand, climate change and other human impacts continue to threaten salmon survival – via warming rivers, changes in stream flows and poor ocean conditions.”
Climate change means we increasingly have to look to the future, she says. “We can’t just protect the current habitat of species, but we need to consider the habitats they may depend on in the future.”
Jonathan Moore, SFU biology professor and co-author of the paper, adds, “Climate change is rapidly transforming ecosystems. Here we show where and when glacial retreat will create new streams for salmon. If we are to protect the future of salmon, this information should inform environmental decision-making and habitat protection.
For more on this research, see Melting Glaciers May Produce Thousands of Miles of New Pacific Salmon Habitat.
Reference: “Retreating Glaciers Create New Habitat for Pacific Salmon in Western North America” by Kara J. Pitman, Jonathan W. Moore, Matthias Huss, Matthew R. Sloat, Diane C. Whited , Tim J. Beechie, Rich Brenner, Eran W. Hood, Alexander M. Milner, George R. Pess, Gordan H. Reeves and Daniel E. Schindler, December 7, 2021, Nature Communication.