Why global warming may actually be good news for salmon

By Georgia Lambert via SWNS

Glaciers melting due to global warming could be good news for salmon, producing thousands of miles of new waterways for them.

By the year 2100, the retreating glaciers in the Pacific mountains of western North America could produce around 6,150 kilometres/ 3820 miles of new Pacific salmon habitat.

Scientists looked at ice from 46,000 glaciers between southern British Columbia and south-central Alaska, to see how much potential salmon habitat would be created when the bedrock is exposed and new streams flow over the melting landscape.

By modelling the glacier 'retreat' under different climate scenarios, Canadian researchers found that under a moderate temperature increase, the glaciers could reveal a potential Pacific salmon habitat over six thousand kilometres, which is nearly as long as the Mississippi River.

If low-gradient streams and the glaciers retreat at their headwaters, this habitat will be desirable for salmon, and the team of researchers was able to pinpoint 315 of the existing glaciers that met these criteria.

The international team was led by researchers at Simon Fraser University in Canada and the University of Birmingham (UOB) in the UK.

Dr. Kara Pitman, a spatial analyst at Simon Fraser, was the study's lead author.

She said: "We predict that most of the emerging salmon habitat will occur in Alaska and the transboundary region, at the British Columbia‒Alaska border, where large coastal glaciers still exist.

"The Gulf of Alaska sub-region is predicted to see the most gains, a 27 percent increase in salmon-accessible habitat by 2100.

“Once conditions stabilize in the newly-formed streams, salmon can colonise these areas quite quickly.

"It’s a common misconception that all salmon return home to the streams they were born in. Most do, but some individuals will stray—migrating into new streams to spawn and, if conditions are favourable, the population can increase rapidly.”

Professor Alexander Milner from the UOB has spent over three decades researching the glacial retreat and salmon populations in southeast Alaska.

He said: “Colonisation by salmon can occur relatively quickly after glacial retreat creates favourable spawning habitat in the new stream."

The professor worked on Stonefly Creek in Glacier Bay, where the glacier retreat revealed a new stream in the late 1970s.

The co-author added: "For example, Stonefly Creek was colonised within 10 years by pink salmon that grew rapidly to more than 5,000 spawners. Other species also colonised including Coho and Sockeye salmon, especially where a lake is associated with the stream."

While the newly created habitat is a positive for salmon in some locations, the researchers have warned that climate change still poses grave threats to other salmon habitats.

Dr Pitman said: "On one hand, this amount of new salmon habitat will provide local opportunities for some salmon populations.

“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 need to look to the future. We can’t just protect current-day habitat for species but need to consider what habitats they might rely on in the future.”