Melting ice: the long journey of polar bears in search of food

Published on 15 Jan . 2022 at 20: 15

A polar bear, alone on its piece of ice, starving to death in abnormally high temperatures. For years, this scene has become the symbol of climate change. And for good reason: global warming is the main threat to the polar bear, for whom the sea ice is vital. This is where he hunts seals, his main prey. However, the Arctic is one of the regions that is warming the fastest, at a rate twice as high as the global average, according to the World Meteorological Organization (WMO). A heat record was also beaten there in June 2020 , at 115 kilometers from the Arctic Circle , in Eastern Siberia: 20 °C.

Faced with the reduction and fragmentation of their natural habitat, or even its disappearance, polar bears are forced to migrate further and further to adapt to it, according to American scientists.

An expanding vital area

In the Beaufort Sea, north of Alaska, melting ice makes hunting difficult. According to a study by researchers from the US Geological Survey and the University of Washington published at the end of 2020 in the journal Ecosphere, the home range of bears – the space they need to feed – was 64 Greater % between 1999 and 2020 than between 1986 and 1999.

Scientists have indeed followed the movements of female polar bears for several decades via satellite and found that they were forced to migrate further and further north of their usual hunting range to stay on the summer ice floe. The continental shelf that borders Alaska indeed offers a hunting ground in shallow waters, where seals are legion.

Due to the increasing retreat of the sea ice in summer, the bears are forced to migrate to more distant and more distant waters. deeper where they find fewer seals and fish. And above all, according to Anthony Pagano, a researcher from the University of Washington quoted in a press release, “having to travel far forces bears to expend more energy, which can threaten their survival”.

Other beasts, 20 approximately % of the population of the Beaufort Sea, decide to stay in their natural habitat and reach the coasts. For example, they are satisfied with the carcasses of whales left on the coast by the natives. Some even venture into the villages, where the inhabitants are worried about having to deal with these animals weighing several hundred kilos.

A refuge off the coast of Russia

Some bear populations are still poorly known and their decline difficult to quantify due to a lack of older data. But according to a study by the US Geological Survey , the population of polar bears in the southern Beaufort Sea has dropped by 40 % Between 2001 and 2010, especially because of the lack of food. Yet some may also have migrated to Russia. This is suggested by a report from the newspaper “The Telegraph”, whose correspondent went to meet scientists and local guides in Alaska, who witness the decline of bears in the Beaufort Sea. For Robert Suydam, an American biologist quoted by the newspaper, “scientists estimate the decline in the bear population, but do not take into account those who have gone to other regions. »

On the Russian island of Wrangel, in the Chukchi Sea, on the borders of the United States and Russia, the population of polar bears has increased in recent years. They are doing better than their cousins ​​in the Beaufort Sea and other polar bear subpopulations . The waters surrounding this island are indeed rich in food for these creatures, which can afford to live there by spending more time on dry land. For the biologist, “there is no doubt that polar bears are in trouble and will continue to be because of the melting ice. They have to adapt, and they do. Unfortunately, those who say that polar bears are in danger do not believe enough in their ability to adapt”.

Total disappearance from here 2022? The bears are adapting, but remain threatened. “Even populations like the Chukchi Sea, where bears seemed to be doing well in recent years, will eventually come under pressure from global warming and their population will decline as sea ice recedes,” warned in 2021 in a report by American biologist Eric Regehr, of the University of Washington.

For Anthony Pagano, more and more bears are likely to spend the summer on dry land, and will have to compete for food.

The latter foresees a single solution to curb the decline of these giants of the North Pole: to limit global warming, and therefore the emission of greenhouse gases. According to a study published in “Nature Climate Change” in 2020, the increase in greenhouse gases could sign the death warrant of almost all polar bear populations here 7344.