When author John McPhee kayaked the Salmon River in Alaska in 1975, he described it as the “clearest, purest water I have ever seen.” But today this National Wild and Scenic River is murky brown, and many of its tributaries have turned bright orange or acidic. Throughout the western Brooks Range, several dozen streams have been “rusting,” most of them in national parks. How has one of America's most remote, pristine areas become threatened by ecological collapse?
The answer lies in the frozen ground beneath the rivers, scientists believe. This permafrost is thawing, allowing water to reach minerals or microbes below the soil for the first time in thousands of years. The result is the release of iron and potential toxins. Scientific American will join the researchers as they hike and packraft more than 100 miles to sample the Salmon River watershed and try to understand this process.
Permafrost thaw has been damaging roads, pipelines, and buildings and forcing Alaska villages to relocate. But the unexpected rusting of rivers could potentially poison whole ecosystems in the U.S. and other northern countries. The Salmon River gets its name from large runs of chum salmon, and other orange streams are important spawning grounds for Dolly Varden, both of which are vital for subsistence fishing. If water quality worsens, it could leave Alaska Native villages downstream hungry and with limited sources of drinking water. This reporting will also contribute to coverage of permafrost thaw impacts in New Scientist and regional radio station KOTZ.