Across Western North America, clearcuts scar coastal forests. In many communities, questions linger about the impacts of industrial logging on salmon. After all, competing messages about forestry and forest health have churned for more than a century.

Now, a comprehensive new study finds that though impacts can vary widely by watershed, logging at any level can carry significant risks for salmon rivers. 

 

Wilder winter rivers and warmer summer water: A new study in Ecological Solutions and Evidence found that watersheds with logging impacts had peak flows that were higher than unlogged systems by a mean 20 percent. Additionally, researchers found that summer streams were a mean 25 percent lower (and as much as 50 percent lower) in logged watersheds, and hotter by a mean 15 percent. (Illustration courtesy GreenOregon.org.)

Published in Ecological Solutions and Evidence, the study synthesizes more than 50 years of water temperature and streamflow data from watersheds ranging from California to Alaska.

And the results are telling—starting with the finding that in summer, stream flows in logged watersheds can be up to 50 percent lower than those without logging impacts.

To examine the question of how logging impacts salmon rivers, the research team—including scientists from Simon Fraser University’s Salmon Watersheds Lab and Wild Salmon Center—drew data from a previously unsynthesized trove of “paired catchment” studies that compare logged watersheds with similar, unlogged systems.