Trembling Oasis for some polar bears found, but not species

Science posted Thursday, June 16. Credit: Kristin Laidre via AP” width=”800″ height=”530″/>

An adult female polar bear, left, and two year-old cubs walk on the ice of a snow-covered freshwater glacier in southeast Greenland in March 2015. With limited sea ice, these Southeast Greenland’s polar bears use freshwater icebergs from the shrinking ice of Greenland. sheet as a makeshift hunting ground, according to a study in a newspaper Science released Thursday, June 16. Credit: Kristin Laidre via AP

As polar bear species fight for survival from disappearing Arctic sea ice, a distinct new group of Greenland bears appear to have stumbled upon an oasis of ice that could allow a small, remote population to ” hang on”.

But it’s far from “a life raft” for endangered species that have long been a symbol of climate change, scientists have said.

A team of scientists has tracked a group of a few hundred polar bears in southeastern Greenland that they believe are genetically distinct and geographically separated from others in a way that had not previously been considered. But what is really distinct is that these bears manage to survive despite having only 100 days a year when there is sea ice to hunt seals. Elsewhere in the world, polar bears need at least 180 days, usually more, of sea ice to use them as a hunting base. When there is no sea ice, bears often do not eat for months.

With limited sea ice, which is frozen sea water, these southeastern Greenland polar bears use freshwater icebergs from the shrinking Greenland ice sheet as makeshift hunting grounds, according to a study published in the Thursday newspaper. Science. However, scientists don’t know if they are thriving because they are smaller and have fewer cubs than other polar bear populations.

“These polar bears are adapted to live in an environment that looks like the future,” said the study’s lead author, Kristin Laidre, a polar bear biologist at the University of Washington who for nine years has tracked , glued and tested fully white bears. from a helicopter flying over the backdrop of white snow and ice. “But most Arctic bears don’t have glacial ice. They don’t have access to it. So it can’t be taken out of context, like it’s like a life raft for the bears. in the Arctic Greenland is unique.

“We predict a significant decline in polar bears in the Arctic and this study does not change that very important message,” Laidre said. “What this study does is show that we find this isolated group living in this unique location… We’re looking at where in the Arctic polar bears as a species may hang, where they might persist.”

Freshwater ice will continue to peel away from the ice sheet for centuries, giving limited hope that this is “a place where polar bears may continue to survive”, but that’s distinct from a trend. general to the loss of sea ice in summer due to heat emissions. trapping gases from burning coal, oil and natural gas, said Twila Moon, deputy principal scientist of the National Snow and Ice Data Center, co-author of the study.

These bears hunt on fresh glacial ice that has more peaks and valleys than flatter sea ice, often in house- or car-sized bergs called bergy bits, Moon said.

This population of polar bears is found at the southeastern tip of the giant island, where there are no towns. For years, scientists thought these bears were part of the same population in northeast Greenland, just wandering along the massive coastline. But they don’t, Laidre said. An unusual pattern of winds, currents and geographic features around 64 degrees north make it almost impossible for bears to move north of that point, the current quickly sending them south, she said.

Oasis tremblante pour certains ours polaires trouvés, mais pas pour les espèces

Three adult polar bears walk in southeast Greenland in April 2015 on sea ice for the limited time it is available. With limited sea ice, these southeastern Greenland polar bears are using freshwater icebergs from the shrinking Greenland ice sheet as makeshift hunting grounds, according to a study published in the journal Science released Thursday, June 16. Credit: Kristin Laidre via AP

While most bears travel 25 miles (40 kilometers) in four days, bears in southeast Greenland travel about 6 miles (10 kilometers) at the same time, according to the study.

“They stay in one place for years and years,” Laidre said.

Genetic testing by Laidre and her colleagues showed they are more different from neighboring populations than any other pair of polar bear populations on Earth, said study co-author Beth Shapiro, an evolutionary geneticist at the University of California at Santa Cruz.

Occasionally, a bear from elsewhere will breed with the southeast bear, but Shapiro said it’s infrequent and one-way with no bears heading north and breeding with that population.

In general, these bears are slimmer than other Arctic bears, with females weighing around 400 pounds (185 kilograms), compared to 440 to 560 pounds (199 to 255 kilograms) elsewhere in the North American Arctic, a Laidre said. And they also tend to have fewer cubs, which could be because they’re so isolated and don’t have as many mating opportunities, she said.

Because this group hadn’t been studied before, Laidre said it’s impossible to say whether the polar bear population in southeast Greenland just adapted to be smaller and have fewer cubs. or if these are indicators of a stressed population and not a good sign of survival. . Shapiro and others don’t think it looks good.

“They don’t breed as much as other individuals,” Shapiro said. “They’re not as healthy as other individuals who live in better habitat. So maybe it’s kind of an oasis, but it’s not a happy oasis. oasis.”

Longtime polar bear scientist Steve Amstrup of Polar Bear International, who was not part of the study, said he was concerned people would mistake this research to mean polar bears can adapt to the climate change, while it is a small group that is prolonging their ability to persist, adding that it “does not offer salvation”. Although this group is distinct, he said he fears drawing attention to him “would actually lessen the natural isolation he currently enjoys”.

It shows “we can still really have some surprises,” Moon said. “And I’m constantly reminded that there’s never a time when we throw in the towel.”

A recently documented polar bear population in southeast Greenland sheds light on the future of the species in a warming Arctic

More information:
Kristin L. Laidre, Glacial Ice Supports a Distinct and Undocumented Subpopulation of Polar Bears Persisting Under Late 21st-Century Sea Ice Conditions, Science (2022). DOI: 10.1126/science.abk2793.

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