Increase in Rusting Rivers Are Creating a Toxic Environment for Alaskan Salmon

This winter, the latest Arctic Report Card from the National Oceanic and Atmospheric Administration (NOAA) confirmed what many in Alaska are already seeing firsthand: the Arctic is warming faster than any other region on Earth, and the Last Frontier’s rivers are experiencing some of the most rapid, visible, and consequential change.

As reported by both NPR and The New York Times, these changes are no longer subtle. Melting permafrost is altering river chemistry, increasing acidity and releasing metals into the water, turning some streams a bright, rusty orange.

If you’re thinking that orange rivers can’t be healthy, well, you’re right. This shift in chemical makeup is reshaping Alaska’s rivers in ways that are directly impacting salmon populations long before fish ever reach the ocean.

Not just a cosmetic shift

Unlike Alaska’s stained waters, the findings from the NOAA Arctic Report Card are crystal clear. This year was both the warmest and wettest in the Arctic since 1900, per NOAA, with Arctic annual temperatures rising at more than twice the global rate of temperature change.

Meanwhile, permafrost thaw is accelerating across Alaska, altering hydrology at a regional scale. According to the University of Alaska Fairbanks, thawing permafrost is reducing cold groundwater inputs and allowing warmer, rain-driven runoff to dominate stream systems in Alaska’s interior.

For salmon, that shift matters for a couple of reasons. Salmon spend their earliest life stages in freshwater, where even small increases in temperature can reduce oxygen levels, increase stress, and lower survival rates before fish ever encounter ocean conditions. That’s not even taking the “rusting rivers” phenomenon into account; heightened permafrost thaw is releasing metals like iron, copper, and aluminum into rivers at an unprecedented rate, triggering changes in pH and causing the alarming discoloration. While these metals are naturally occurring, the faster rate of permafrost melting is causing larger runoff concentrations to seep into rivers, causing disruptions to aquatic ecosystems.

Harming fish on multiple fronts

Again, the impacts of this disturbance to native species are far-ranging and multifaceted. Beyond the direct health threat to the fish themselves, for example, the National Park Service has documented declines in aquatic insects in affected systems, weakening the base of the salmon food web.

In some cases, the impact has been swift and extreme. The New York Times noted that a 2024 ground survey in Kobuk Valley National Park found that the Akillik River changed from clear to orange over the course of a summer, causing widespread mortality of fish and aquatic fauna. Other cases haven’t been quite so stark, though in several monitored watersheds, it’s been noted that changes are persisting year after year rather than reverting once temperatures cool, suggesting long-term change rather than temporary disruption.

It’s worth noting that, thus far, the most severe shifts in river waters have been concentrated to smaller bodies of water. But if more incidences spread to larger watersheds, the impacts to salmon and other native fish species could be intense.

What this means right now

NOAA’s report card makes it clear that climate-driven change is neither going away nor slowing down, and neither are its trickle-down effects on Alaska’s salmon populations. Warmer air and warmer water are fundamentally reshaping salmon habitats from the headwaters downstream.

These are significant, measurable pressures that aren’t driven by commercial fishing activity and don’t show up in bycatch charts. Salmon are facing growing challenges in freshwater environments increasingly shaped by temperature, chemistry and watershed change. If the goal is rebuilding salmon runs, science suggests that our focus must extend beyond a single data point.

Salmon depend on cold, clean rivers long before they reach the ocean. Protecting them means following the full life cycle—and paying attention to what’s happening upstream in addition to our fisheries.

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References

Eric Niiler (2025). “Arctic Warming Is Turning Alaska’s Rivers Red With Toxic Runoff.” The New York Times. December 16, 2025. https://www.nytimes.com/2025/12/16/climate/arctic-report-card-agu.html.

National Oceanic and Atmospheric Administration (2025). Arctic Report Card 2025. December 2025. https://arctic.noaa.gov/report-card/report-card-2025/.

National Public Radio (2025). “Arctic Climate Change Is Accelerating, NOAA Report Finds.” December 16, 2025. https://www.npr.org/2025/12/16/nx-s1-5639224/arctic-climate-change-noaa-report.

National Park Service (2023). “Rusting of Wild and Scenic Rivers in Alaska.” https://www.nps.gov/articles/000/rusting-of-wsrs-in-alaska.htm.

University of Alaska Fairbanks (2025). “Rainfall and Melting Permafrost Change Interior Alaska Stream Systems.” https://www.uaf.edu/news/rainfall-and-melting-permafrost-change-interior-alaska-stream-systems.php.