They discover a new population of polar bears better adapted to climate change

A polar bear from southeastern Greenland on a glacier, or freshwater ice, at 61 degrees north in September 2016. / Laidre et al./Science

Science | biology

The use of fresh ice that breaks off from the Greenland glaciers serves as a platform to hunt throughout the year.

Elena Martin Lopez

Of all the creatures threatened by a warming Arctic, whose temperature is rising at an alarming rate and more than twice as fast as the rest of the planet, polar bears are particularly vulnerable, relying on (less and less persistent) sea ice to keep them warm. hunt and feed. Now, a team of scientists has discovered an undocumented population of these animals in southeastern Greenland, isolated and genetically distinct, whose limited access to sea ice (frozen ocean) has led them to take advantage of glacial ice (made up of fresh water). to hunt. This performance provides a hopeful perspective on the resilience of this group of bears in the face of climate change.

Here's the explanation: Polar bears use sea ice to hunt seals, but bears in southeastern Greenland don't have access to sea ice for eight months of the year. In order not to starve, they had to find a solution, and they found it in the glacial ice, which allows them to live and hunt all year round without having to migrate to other places in search of food, as the polar bears of the Arctic do during the summer months. The finding may shed light on the future of the species in future climate scenarios, as current sea ice conditions in southeastern Greenland are similar to those predicted to be in the High Arctic by the end of this century. the researchers.

The study, published Thursday in the journal Science, combines 37 years of current and traditional knowledge about the habitat, movement, genetics and demography of Greenland's polar bears, along with indigenous ecological knowledge of the island. The southeastern part had been little studied for its unpredictable weather, jagged mountains, and heavy snowfall, although isolated populations of polar bears were known to inhabit it from historical records and traditional knowledge. "What we didn't know was that they were so special," says the study's lead author, Kristin Laidre, a polar scientist at the University of Washington Physics Laboratory, because these bears have not only developed a different way of feeding, but their genetics it is also very different from the rest of the 19 documented polar bear populations.

The blue lines show that polar bears from northeast Greenland travel across a large area of ​​the island in search of sea ice to hunt, while those from the southeast have more limited movements within their home fjords or neighboring fjords.

Small strands and fewer puppies

The researchers believe that part of the reason the population is so isolated is that the environment where these bears live is hemmed in on all sides, between the mountains and the massive Greenland ice sheet and the open waters of the Denmark Strait. which has been able to influence the size of this group of bears (only a few hundred). Perhaps this has also influenced their body measurements -adult females are smaller than in most regions-, and their offspring -they have fewer cubs, which may reflect the challenge of finding a mate in the complex landscape of fjords and mountains-.

The fact that these polar bears can survive in such habitat suggests that sea-ending glaciers, and especially those that regularly dump ice into the ocean, could become small-scale climate refugia as surface sea ice dwindles. of the ocean, something that had not been taken into account until now and that has implications for the conservation of the species. Even so, “this habitat is not found in most of the Arctic where polar bears live, but is mainly concentrated in Greenland and the island of Svalbard. So we need to be careful about extrapolating our findings," says Laidre, who cautions that longer-term follow-up is needed to learn the future viability of bears in southeastern Greenland and to understand what happens to polar bear subpopulations as they grow. they are becoming increasingly separated from the rest of the Arctic due to shrinking sea ice.

The fieldwork required a daily four-hour helicopter ride from a Greenland coastal community or other bases to reach the bears' habitat. /

Laidre et al./Science

“The loss of sea ice in the Arctic remains the main threat to all polar bears. This study does not change that. Sea ice continues to decline in the Arctic, and that will reduce the survival of most polar bears. The most recent projections are a 30% global decline in polar bears over the next 3 generations (about 35 years) under current warming trends. Glacial ice may help a small number of polar bears survive for longer periods under climate warming and may be important for the persistence of the species (meaning preventing extinction), but it is not available to the vast majority of polar bears. most polar bears. Monitoring these new bears can perhaps tell us a bit more about the future of the species," says Laidre.

-But the glaciers are also melting… what will happen in that case?

-Glacial ice is also changing with global warming. We don't know the future and how long the bears in southeastern Greenland will endure this –acknowledges the researcher.

The International Union for Conservation of Nature, which helps monitor protected species, will be responsible for determining whether the bears of southeastern Greenland are recognized internationally as a separate population, the 20th in the world.

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