Population of polar bears found in an area believed to be uninhabitable for them

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The loss of Arctic sea ice due to climate change seriously threatens the survival of polar bears, which are distributed throughout the circumpolar region. Climate models suggest that many parts of the Arctic may remain ice-free for more than five months by 2050. This would lead to prolonged fasting among bear populations, increased hunger and damage their reproduction. However, a recently discovered subpopulation of polar bears brings new hope for the future of the species.

Polar bears have been protected since 1973 by an international agreement between the Arctic nations, namely Russia, the United States, Denmark, Norway and Canada. This was one of the first international wildlife agreements. The bear populations were in rapid decline at the time due to sports hunting. Today, this mammal is threatened by climate change, which is causing the massive melting of the Arctic sea ice. It entered the Red List of the International Union for Conservation of Nature (IUCN) in 2015 as a vulnerable species.

Most polar bears rely on sea ice to hunt seals, so current and expected reductions in the presence and persistence of this ice are likely to have major consequences for their survival. But against all odds, a team of scientists discovered an unprecedented subpopulation of polar bears established in southeastern Greenland, where sea ice is even smaller. This minor dependence on sea ice suggests that the animal was able to adapt to this environment.

A completely isolated 20th subpopulation of polar bears

Currently, 19 polar bear subpopulation units are recognized by the IUCN Polar Bear Specialist Group. Their exact abundance is particularly difficult to determine, as these animals often occur at low densities in remote habitats. But according to the latest estimates, there are about 26,000 polar bears. A few people are now adding this list: While exploring southeast Greenland, a team led by the University of Washington’s Polar Science Center discovered a new subpopulation, very different from the others.

We knew there were bears in the area based on historical records and aboriginal knowledge. We just did not know how special they were said Dr. Kristin Laidre, lead author of the study, reports this finding. Despite having very limited access to the sea ice, this subpopulation has managed to survive.

The sea ice conditions in this region of the globe are actually similar to predictions for the Arctic Circle: the annual “ice-free” period exceeds the estimated fasting threshold for the species by more than 100 days, the team says in Science. But the bears seem to have adapted to this environment and manage to hunt all year round thanks to Greenland’s freshwater glaciers, which regularly calve ice in the sea.

The remote region of south-eastern Greenland had so far been little studied due to its unpredictable climate, steep terrain and heavy snowfall. Researchers collected data for seven years to study this population. They found that this group of polar bears was genetically very different from all the others. ” This is the most genetically isolated population of polar bears on the planet said Beth Shapiro, a geneticist at the University of California, Santa Cruz and co-author of the study.

A “refuge” that will not be able to save the whole species

Researchers estimate that a few hundred bears make up this subpopulation. Measurements show that adult females are smaller than in other regions and also have fewer young – no doubt due to the difficulty of finding a mate in this isolated region. The conservation of this new subpopulation is crucial to conserving the species’ genetic diversity and evolutionary potential, the researchers emphasize.

This group has lived separately from the others for at least several hundred years. This isolation is due to the geolocation of this subpopulation, surrounded by steep mountains, the Strait of Denmark and the coastal current of Greenland. In addition, unlike other populations of polar bears, the individuals of this group move a little: they stay on their fjord or climb up the mountains to reach the nearby fjords. Half of the 27 bears tracked by satellite ‘floated by accident’ on small ice patches averaging 190 kilometers to the south, the team reports, but ended up leaving their ‘vessel’ to return to their fjord.

Satellite tracking shows that polar bear populations in southeastern and northeastern Greenland have very different behaviors. The blue lines show that the bears in the northeast cross a large sea ice to hunt, while the red lines show that the bears in the southeast have more limited movements, inside their eastern fjords, origin or neighboring fjords. © Laidre et al.

The glaciers in south-eastern Greenland are quite unique, and the regular supply of ice depends on a combination of several factors: the shape of the fjords, the high production of glaciers and the very large reservoir of ice available in the Greenland ice sheet. Similar glaciers are found on other parts of the coast of Greenland and on Svalbard – an archipelago located north of Norway.

The discovery of this population suggests that sea-terminated glaciers, although their availability is limited, could serve as a refuge for polar bears. ” But we must be careful about extrapolating our results, because the glacier ice that allows bears in southeastern Greenland to survive is not available in most of the Arctic. Laidre warns. The specialist insists that there are simply not enough such habitats to accommodate the 26,000 polar bears that are currently endangered.

Source: K. Laidre et al., Science

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