Beavers in the Arctic: Why Methane Hotspots Cluster 51% More Around Their Ponds

Beavers are rapidly expanding their range in northwest Alaska, moving past the northern edge of the boreal forest into Arctic tundra. Where they dam a stream, they flood the soil beside it — and flooding can thaw the permafrost beneath. Permafrost stores large amounts of carbon, which thawing can release as carbon dioxide or methane, and wet soils along beaver-changed streams favor methane. That matters because methane is the second most abundant greenhouse gas after carbon dioxide, and better than carbon dioxide at trapping heat.

Measuring water in an Arctic beaver pond. NPS.

Looking for methane from the air

Ground measurements of methane from beaver ponds on permafrost are scarce. So scientists from the University of Alaska Fairbanks, NASA and the National Park Service used an airborne hyperspectral imaging spectrometer (AVIRIS-NG) to map methane "hotspots" — places thought to emit a lot of it — in the lower Noatak River basin, in and around Noatak National Preserve.

What they found

• Hotspots were significantly more common around beaver ponds than around other lakes and streams, out to a distance of 60 m.
• Overall, hotspots were 51% more common around beaver ponds than around nearby water beavers had not changed.
• Dammed lake outlets showed no significant difference from undammed lakes — probably because damming changed how much land they flooded very little.

The researchers trace the extra methane to what beavers do: drowning existing vegetation, turning flowing water into still water, building up organic-rich sediment, raising the water table, creating oxygen-poor conditions and thawing permafrost.

Why it matters

The study describes this as a new kind of disturbance, driven by an ecosystem engineer, that accelerates the effects of climate change in the Arctic. As beavers keep spreading and reshaping the lowlands, the authors expect more wetlands, more permafrost thaw and further changes to the Arctic carbon cycle. Next, the team plans ground measurements of methane from beaver-affected soils to check what the aircraft saw.

Sources

Based on "Beavers and the Arctic carbon cycle," National Park Service, Arctic Inventory and Monitoring Network, summarizing Clark JA, Tape KD, Baskaran L, Elder C, Miller C, Miner K, O'Donnell JA and Jones BM (2023); a work of the United States government in the public domain; rewritten in hubnx's own words.