TIME IN THE ALASKAN Arctic moves slowly. Layers of permafrost inter the chilled remains of mammoths and early humans; dwarf birches and lichens grow at almost imperceptible clips; glaciers creep down mountains at annual rates measured in millimeters. Abrupt disturbance is rare: There are no hurricanes or tornadoes, and few floods and wildfires. Landscapes are static. Change, when it comes, is subtle and incremental. Besides the beavers.
Climate change has given the industrious mammals a foothold in Arctic Alaska, the vast tundra ecosystem in the northern reaches of the state. As the region has warmed, new willows have sprouted and invited beavers, who both eat the inner bark and harvest stems for dam-building material. Beavers have also benefited from more open water, as their ponds are less likely to freeze solid in balmier winters. Near the city of Kotzebue in western Alaska, beaver dam construction spiked 50-fold between 2002 and 2019. “Just about everywhere you go, you’re going to run into a beaver dam,” says Cyrus Harris, an Iñupiaq hunter and natural-resource advocate in Kotzebue.
Plenty of animals, including moose and red foxes, are moving into the fast-warming Arctic. But beavers aren’t just taking advantage of environmental change; they’re accelerating it. The indefatigable architects’ dams transform streams into chains of ponds and wetlands so immense they’re visible from space. In its 2021 Arctic Report Card, the National Oceanic and Atmospheric Administration called beavers a “new disturbance” transmogrifying the tundra “stream by stream and floodplain by floodplain.”
The Arctic isn’t the only place beavers are booming. Once nearly exterminated for their pelts, 10 to 15 million beavers inhabit North America; they thrive in ecosystems as diverse as boreal forests and southwestern deserts. Conservationists and scientists hail them as ecological champions whose ponds filter out heavy metals and other pollutants, slow wildfires, store water, and furnish habitat for birds including Hooded Mergansers and Trumpeter Swans. Today states like California, Colorado, and Washington are aggressively pursuing their restoration. “There’s been this great positive feedback loop of encouragement for working with beavers,” says Emily Fairfax, a University of Minnesota beaver researcher. “They’re a
