Photo: Pablo Cozzaglio Agence France-Presse
The beavers could be (partially) responsible for the phenomenon of which they are enjoying since the water that accumulates behind their dam would melt the permafrost, which releases greenhouse gases.
The beavers seem to take advantage of the warming climate to migrate north and occupy the territories that were previously inaccessible.
Researchers from the University of Alaska at Fairbanks have worked on 12 years of satellite images of high resolution to examine the presence of rodents in an area of 100 square kilometres in the north-west of Alaska. In particular, they have mapped the dams and calculated the increase of the surface area of water.
According to what they write in the scientific journal Environmental Research Letters, the number of beavers in the region would be increased from two in 2002 to 98 in 2019.
During the same period, the area covered by ponds and lakes would be passed of 5.94 square kilometers to 6.43 per square kilometers, and the beavers would be responsible for 66 % of this increase, according to the researchers.
“The North is changing a lot,” said professor Najat Bhiry from the department of geography of Laval University. The subarctic and arctic 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 […] the conditions are more favourable to certain species that are more accustomed to live in the south. “
The phenomenon would not be unique to Alaska. The inuit community of Umiujaq, with which Ms. Bhiry regularly contributes, described as well an increase in Nunavik, the number of beavers, their dams and ponds that form.
Contribute to the global warming
The researchers from the University of Alaska raised the possibility that beavers can be (partially) responsible for the phenomenon of which they are enjoying since the water that accumulates behind their dam would melt the permafrost allowing the microbes to decompose the material previously inaccessible — and resulting in the release into the atmosphere of two powerful greenhouse gas, carbon dioxide and methane.
“It is [a phenomenon] plausible, but it is an assumption that they have issued, said Ms. Bhiry. It is quite logical, but it is necessary to check. And for the check, it is necessary to make measurements on the spot. “
And if it is an “ecological phenomenon interesting […] that worth to be mentioned”), has responded to professor Michel Allard, Centre d’études nordiques of Université Laval. But it is important, according to him, taking a bit of 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 phenomenon-there are very scarce “, he said.
In fact, says the professor Allard, a simple climate a little milder, will not be sufficient to attract the beavers : they are also in need of tree species of their choice and soils conducive to the construction of their dams.
“The study [american] is silent on it, he noted. There is no field work at all. Everything is done by the analysis of aerial photos or satellite images. We do not know the nature of the soil. It is not known what vegetation is there. They do not even the name of a tree species.
“The less informed observer that analysis of aerial photos can see in his area of work no matter when [dam] beaver. It is so easy. “
Not only are the beavers
The beavers are obviously not the only ones to benefit from the warming climate to migrate a bit more towards the north.
“It’s the same thing for the moose, said Ms. Bhiry. The limit was further south, and it is more and more to the north. The environment will be shared between the musk ox, the caribou and the moose, so the dynamics will be quite different. The Nunavik is great, but there are certain places that attract more animals. “
The warming climate also contributes to what is called the ” greening of the North “, namely, the appearance of shrubs where there was virtually nothing before.
The herbivores in search of food will, therefore, in the jurisdictions where they would otherwise have never ventured.
The appearance of these shrubs will also contribute to the thawing of the soil, ” remarked the professor Allard, as the increase of the density of the shrubs will generally increase the increase of the snow and to keep the soil from regeler.
The shrubs are progressing currently to the north and multiply, and eventually they will be up to the first trees.
“This environmental change then 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 which is important, so that in the end, unravel the sheer impact of the action of the beavers of the impact of climate change is not so simple. “