Beavers take advantage of global warming to migrate north

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Beavers take advantage of global warming to migrate north





© Provided by The Canadian Press



MONTREAL – Beavers seem to be taking advantage of global warming to migrate north and occupy territories that were previously inaccessible to them.

Researchers at the University of Alaska at Fairbanks have scanned 12 years of high-resolution satellite imagery to examine the presence of rodents in a 100 square kilometer area in northwestern Alaska. They notably mapped the dams and calculated the increase in the surface area of ​​water.

According to what they write in the scientific journal Environmental Research Letters, the number of beavers in the region has increased from two in 2002 to 98 in 2019.

During the same period, the area covered by ponds and lakes would have increased from 5.94 square kilometers to 6.43 square kilometers, and beavers would be responsible for 66% of this increase, according to the researchers.

“The North is changing a lot,” said Professor Najat Bhiry, of the geography department of Université Laval. Arctic and subarctic regions are warming three times faster than the rest of the world.

“This warming has encouraged the migration of several species to the north, because (…) conditions are more favorable for certain species which are more used to living in the south.”

The phenomenon is not unique to Alaska. The Inuit community of Umiujaq, with whom Ms. Bhiry collaborates regularly, describes an increase in Nunavik in the number of beavers, their dams and the ponds that form.

Contribute to global warming

Researchers at the University of Alaska raise the possibility that beavers may be (partially) responsible for the phenomenon from which they benefit since the water that accumulates behind their dams would melt the permafrost, allowing the microbes to decompose. previously inaccessible material – and causing two powerful greenhouse gases, carbon dioxide and methane, to be released into the atmosphere.

“It’s (a plausible) phenomenon, but it’s an assumption they made,” said Bhiry. It is completely logical, but it must be verified. And to verify it, you have to take measurements on the spot. ”

And if it is an “interesting ecological phenomenon (…) that is worth mentioning”, reacted Professor Michel Allard, from the Center d’études nordiques de l’Université Laval . But he believes it is important to take a step back from the situation.

“I think it is an exaggeration to say that it could be a big contribution to climate change, because the regions affected by this kind of phenomenon are very scarce,” he said.

Indeed, underlines Professor Allard, a simple climate a little more lenient will not be enough to attract beavers: they also need tree species that they like and soils suitable for the construction of their dams.

“The (American) study is silent on this,” he said. There is no field work. Everything is done by analyzing aerial photos or satellite images. We don’t know the nature of the soil. We do not know what vegetation is there. They do not even give the name of a species of tree.

“The least informed observer who analyzes aerial photos can see beaver (dams) in his work area at any time. It’s so easy. ”

Not just beavers

Beavers are obviously not the only ones taking advantage of global warming to migrate a little further north.

“It’s the same with moose,” said Ms. Bhiry. The boundary was further south, and it is further north. The environment will be shared between muskox, caribou and moose, so the dynamics will be quite different. Nunavik is big, but there are some places that attract more animals. ”

Global warming is also contributing to what is called “greening of the North”, the appearance of shrubs where there was practically nothing before.

The herbivores in search of food will therefore invade territories where they would otherwise never have ventured.

The appearance of these shrubs will also contribute to the thawing of the soil, notes Professor Allard, since the increase in the density of the shrubs will generally increase the increase in snow and prevent the ground from refreezing.

The shrubs are currently progressing north and multiplying, and eventually they will make way for the first trees.

“This ecological change promotes the degradation of permafrost, but at the same time provides a habitat that is more favorable to the beaver,” he concluded. There is a cyclical aspect that is important, so that in the end, unraveling the pure impact of beaver action from the impact of climate change is not so simple. ”

Jean-Benoit Legault, The Canadian Press

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