Simon Frasier University Study Determines That Salmon Need Trees

Coho smolt
Coho smolt. Photo: Julian Gan/Simon Frasier University.

A new study by researchers at British Columbia’s Simon Fraser University concludes that the impacts of logging may take a surprisingly long time to manifest themselves, but that logging does indeed have big impacts on the well-being of fish.

The study, led by Simon Fraser’s Kyle Wilson, looks at the successes and failures of five species of salmon in the Keogh River on northern Vancouver Island.

“It’s not just the ocean that is driving declines,” Wilson explained. “The combination of marine and freshwater stressors effectively ‘squeezes’ sone salmon populations by lowering survival in both the rifer and the sea.”

The declines were found to coincide with combinations of stressful environmental changes including fluctuating ocean climate an increase in coastal seals and other competing salmon, warmer water temperatures and increased watershed logging. Lower juvenile salmon survival in rivers, impacted by watershed logging, was happening with reduced survival of adult salmon due to increased risk from predatory seals and competition with other salmon, both wild and hatchery raised.

Wilson said the study findings can help inform policies such as the Canadian government’s recent Pacific Salmon Strategy Initiative, which will allocate $647.1 million to a variety of conservation and scientific efforts to help salmon recover.

The study, published in the journal Global Change Biology, determined that increases in the cumulative area of logging activity in their study watershed was associated with 97% or greater reductions in the freshwater productivity of steelhead, coho salmon and coastal cutthroat trout.

Fisheries biologist Erik R. Schoen, at the International Arctic Research Center at the University of Alaska Fairbanks, noted in a commentary on Wilson’s research that although the analysis was specific to one British Columbia watershed that the findings have important implications for forest management and habitat conservation in the broader coastal temperate rainforests of the North Pacific.

“These rainforests have been fragmented by over a century of logging and human development, but they still contain intact watersheds with global significance for biodiversity and climate stability, concentrated in Alaska and British Columbia,” Schoen noted.

If historic logging has strongly reduced salmonid productivity throughout the temperate rainforest, as Wilson found in this study area, then new approaches to forest management could potentially yield major gains toward recovering fish populations and fisheries, he said.