HomeTechnologyUnstable oasis found for some polar bears, but not species

Unstable oasis found for some polar bears, but not species


With the polar bear species in a struggle for survival due to the disappearance of Arctic sea ice, a distinct new group of Greenland bears appears to have stumbled upon an icy oasis that could allow a small, remote population to “hang on.”

But it is far from the “lifeboat” for endangered species that has long been a symbol of climate change, scientists said.

A team of scientists tracked down a group of a few hundred polar bears in southeastern Greenland showing that they are genetically distinct and geographically separate from others, something that had not been considered before. But what is really different is that these bears manage to survive despite only having 100 days a year when there is sea ice to hunt seals. In other parts of the world, polar bears need at least 180 days, usually more, of sea ice to use as a hunting base. When there is no sea ice, bears often don’t eat for months.

With limited sea ice, which is frozen ocean water, these southeastern Greenland polar bears use freshwater icebergs spawned by the shrinking Greenland Ice Sheet as makeshift hunting grounds, according to a study published in the journal Science on Thursday. . However, scientists aren’t sure if they are thriving because they are smaller and have fewer cubs than other polar bear populations.

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“These polar bears are adapted to living in an environment that looks like the future,” said study lead author Kristin Laidre, a University of Washington polar bear biologist who spent nine years tracking, collaring and testing polar bears. completely white bears usually. from a helicopter flying over the white snow and ice background. “But most Arctic bears don’t have glacial ice. They don’t have access to this. So it can’t be taken out of context as if this is somehow like a life raft for polar bears in the Arctic. It is not. Greenland is unique.”

“We project large declines in polar bears in the Arctic, and this study doesn’t change that very important message,” Laidre said. “What this study does is show that we found this isolated group living in this unique place… We’re looking at where in the Arctic polar bears might hold out as a species, where they might persist.”

Freshwater ice will continue to break off the ice sheet for centuries, giving limited hope that this is “a place where polar bears could continue to survive,” but it is separate from a general trend of summer sea ice loss due to heat emissions. trapping gases from burning coal, oil and natural gas, said National Snow and Ice Data Center Deputy Principal Scientist Twila Moon, a co-author of the study.

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

This population of polar bears is located on 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 roaming the huge coastline. But they don’t, Laidre said. An unusual configuration of winds, currents and geographic features around 64 degrees north makes it almost impossible for bears to move north of that point, the current sending them rapidly south, she said.

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

“They just stay in the same place for years and years,” Laidre said.

Genetic tests by Laidre and her colleagues showed that 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 Santa Cruz.

Occasionally, a bear from elsewhere will breed with the southeastern bear, but Shapiro said it’s rare and only one-way, since no bear heads north and breeds 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) in other parts of the North American Arctic, Laidre said. And they also tend to have fewer pups, which could be because they’re too 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 know if the polar bear population of southeastern Greenland has simply 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 reproduce as much as other individuals,” Shapiro said. “They are not as healthy as other individuals that are in a better habitat. So maybe it’s kind of an oasis, but it’s not a happy oasis. It is a kind of oasis in which it is difficult for me to get ahead, but I am achieving it”.

Steve Amstrup, a longtime polar bear scientist with Polar Bear International, who was not part of the study, said he worries that people will misunderstand this research to mean polar bears can adapt to climate change, when it’s a small group that is prolonging their ability to persist, adding that this “offers no salvation.” While this group is different, he said he fears drawing attention to them “may actually lessen the natural isolation they currently enjoy.”

This shows “we can still have surprises,” Moon said. “And I am constantly reminded that there is never a point where we throw in the towel.”

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Follow Seth Borenstein on Twitter at @borenbears

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