Unstable oasis for some polar bears found, but not for species

Unstable oasis for some polar bears found, but not for species

With polar bear species fighting for survival because of the disappearing Arctic sea ice, a distinct new group of Greenland bears appears to have stumbled upon an ice oasis that could allow a small, remote population to “hold on”.

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

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

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

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

“We project large declines in polar bears across the Arctic and this study does not 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 Arctic polar bears can sustain themselves as a species, where they can persist.”

Freshwater ice will continue to come out of the ice sheet for centuries, giving limited hope that this is “a place where polar bears can continue to survive”, but it is separate from a general trend of summer sea ice loss by cause of heat emissions. trapping gases from burning coal, oil and natural gas, said deputy principal scientist at the National Snow and Ice Data Center, 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 icebergs called bergy bits, Moon said.

This polar bear population is at the southeastern tip of the giant island, where there are no cities. For years, scientists have imagined that these bears were part of the same population in northeast Greenland, just wandering up and down the massive coastline. But they don’t, said Laidre. An unusual configuration of winds, currents and geographic features around 64 degrees north makes it nearly impossible for bears to move north of that point, the current sending them south quickly, she said.

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

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

Genetic tests that Laidre and colleagues have done have shown 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 infrequent and one-way with no bears going north and breeding with that population.

In general, these bears are slimmer than other Arctic bears, with females weighing around 185 kilograms, compared to 199 to 255 kilograms in other parts of the North American Arctic, Laidre said. And they also tend to have fewer offspring, which could be because they’re too isolated and don’t have as many mating opportunities, she said.

As this group had not been studied before, Laidre said it is impossible to say whether the polar bear population in southeastern Greenland has 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’re not reproducing as much as other individuals,” Shapiro said. “They are not as healthy as other individuals who are in a better habitat. So maybe it’s an oasis, but it’s not a happy oasis. It’s a kind of oasis of the kind I’m struggling to survive, but only succeeding.

Longtime polar bear scientist Steve Amstrup of Polar Bear International, who was not part of the study, said he fears people will misinterpret this research to mean that polar bears can adapt to climate change, when it comes to a small group that is prolonging its ability to persist, adding that it “does not offer salvation”. While this group is distinct, he said he feared that drawing attention to it “could actually lessen the natural isolation they currently enjoy.”

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

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Follow Seth Borenstein on Twitter at @borenbears

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