On the rise: beavers nibble on the permafrost

In the Arctic, climate change is having a particularly strong impact. In Alaska, for example, the average temperature has risen by more than two degrees Celsius since the late nineteenth century. The winters are getting shorter and warmer. It’s no wonder that the plant world is changing, and with the flora, so is the fauna: the elk native to Alaska, a particularly impressive subspecies called moose alces gigas, until the end of the nineteenth century roamed only in the densely wooded south of Alaska. The animals, which can weigh up to ten hundredweight, can also get along in the treeless tundra. Provided that the bushes in the river meadows stick out far enough above the snow in winter to provide sufficient food. Good on foot, the moose quickly populated the newly created habitat. They have now reached the coast of the Arctic Ocean.

The American beaver (Castor canadensis) his income. The massive rodents are by no means as agile as the long-legged moose. But with the ability to reshape streams and smaller rivers according to their needs, beavers are among the so-called key species that shape an ecosystem in the long term. Unlike in this country, they are allowed to live out their talent as hydraulic engineers unhindered in Alaska. Where beavers have recently made their home, they have used cleverly placed dams to create a complex system of ponds for many streams and small rivers that meander through the arctic tundra.

Beavers are changing the landscape even more than meets the eye. Scientists working with Ken D. Tape from the University of Alaska Fairbanks and Guido Grosse from the Alfred Wegener Institute for Polar and Marine Research in Potsdam have discovered that their brisk construction activity also promotes the thawing of the permafrost. Using satellite imagery of Alaska’s arctic tundra, they identified more than 11,000 ponds created by beavers. Extrapolated to areas without usable images, there are almost thirteen thousand.

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When the Burghers began to migrate north

The evaluation showed that the beavers are spreading further and further to the west and north over time. Between the years 2000 and 2006 and 2015 and 2019 they doubled the number of their ponds there. The fact that the beavers are on the rise can also be seen on aerial photos from the years 1976 to 1984. On the other hand, recordings from the years 1949 to 1955 testify that the rodents, who are talented in hydraulic engineering, were only sporadically active in the tundra at that time. This may also have something to do with the fact that beavers were hunted intensively and drastically decimated for their valuable fur well into the 20th century. Whether they may have been native to the tundra before the boom in fur hunting and fur trading is still an open question.


The large rodents are changing the landscapes of the Arctic. Their construction activity is not without consequences for the frozen soil and the climate.
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Bild: University of Alaska Fairbanks

Many observers are so surprised and impressed by the current spread of the beavers that they report on it in detail. Photographer and co-author Seth Kantner, for example, born on the Kobuk River in 1965, has been familiar with the busy rodents since childhood. After all, beavers have always been present in the forests of his homeland. Later he was able to observe how their typical castles and dams suddenly appeared further north and west in stream valleys of the tundra: “In the mud and in the willow bushes on the bank, the golden shimmer of freshly peeled saplings catches the eye. Above, felled poplars lean against their stumps as if an army of lumberjacks had moved up the valley. The beaver has left its mark everywhere.”

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