Scientists have recognized a definite subpopulation of polar bears in southeastern Greenland that, in an space with little sea ice, survive by searching from ice that breaks off glaciers.
The invention suggests a approach {that a} small variety of bears would possibly survive as warming continues and extra of the ocean ice that they usually rely upon disappears. However the researchers and different polar specialists cautioned that grave dangers to the general polar bear inhabitants within the Arctic stay and can solely be lessened by chopping greenhouse gasoline emissions to curb international warming.
The subpopulation, believed to quantity a number of hundred animals, was recognized throughout a multiyear examine of what was regarded as a single inhabitants of bears alongside Greenland’s complete 1,800-mile-long east coast. By way of evaluation of satellite-tracked actions, tissue samples and different information, the bears within the southeast have been discovered to be remoted, each bodily and genetically, from the others.
“This was an entirely surprising discovering,” mentioned Kristin Laidre, a biologist on the College of Washington who has studied marine mammal ecology in Greenland for 20 years. Dr. Laidre is the lead writer of a paper on the subpopulation printed Thursday within the journal Science.
Southeastern Greenland is very distant, with slim fjords hemmed in by steep mountains. On the inland finish there are sometimes glaciers that terminate within the water; on the different finish is open ocean, with a robust south-flowing present. “These bears are very geographically remoted,” Dr. Laidre mentioned. “They’ve actually form of developed to being residents as a result of that’s the one option to dwell down there.” The researchers estimated that this subpopulation had been remoted for no less than a number of hundred years.
General, there are an estimated 26,000 polar bears across the Arctic, in 19 formally designated subpopulations. The animals dwell on the seasonal sea ice, searching their major prey, seals, because the seals bask on the ice or come up for air via respiratory holes. However the fast warming of the Arctic linked to human-caused emissions of greenhouse gases has decreased the extent and length of sea-ice cowl.
Some subpopulations, notably one within the southern Beaufort Sea off Alaska and Canada, are already declining as a result of the ice doesn’t persist lengthy sufficient for the bears to hunt sufficient meals for themselves and their offspring. Polar bear specialists say that if the world continues to heat polar bears might turn out to be practically extinct by the top of the century.
Southeastern Greenland is comparatively heat, and the fjords there have much less sea-ice cowl than many different areas with polar bears — on common, about 100 days a 12 months with sufficient ice for them to dwell and hunt on. “We all know that that’s simply too few for a polar bear to outlive,” Dr. Laidre mentioned. These are the sorts of situations that will turn out to be widespread elsewhere within the Arctic later this century.
Dr. Laidre and her colleagues discovered that the Southeastern Greenland bears hunt from sea ice whereas it’s round. However when it’s gone, the bears produce other ice to hunt from: the freshwater ice that calves off from the glaciers into the fjords, as icebergs and progressively smaller chunks, and that persists many of the 12 months
The bears hunt from this floating mixture of ice, referred to as glacial mélange, in the identical approach they hunt from the ocean ice. “It offers them an additional and unusual ice platform that bears in lots of different locations don’t have,” Dr. Laidre mentioned, permitting them to catch sufficient seals for them and their offspring to outlive and thrive.
However habitats like this are uncommon, mentioned Twila Moon, a scientist with the Nationwide Snow and Ice Information Heart in Boulder, Colo., who analyzed sea-ice and glacial-ice cowl within the fjords as a part of the analysis.
“There are restricted areas within the Arctic the place we see substantial and constant manufacturing of glacial mélange,” Dr. Moon mentioned. Along with some areas in Greenland, the Norwegian archipelago of Svalbard has glaciers that terminate within the water.
So whereas these particular situations might permit some bears to outlive as the ocean ice continues to shrink, total the animals will proceed to be threatened by local weather change.
“We predict to see giant declines of polar bears throughout the Arctic beneath present warming trajectories,” Dr. Laidre mentioned. “And this examine doesn’t change that.”
Steven Amstrup, chief scientist with the conservation group Polar Bears Worldwide, who was not concerned within the analysis, mentioned the examine was “actually totally carried out” and “factors to a really discrete group of bears.”
Whether or not it constitutes a twentieth official subpopulation is as much as a gaggle of specialists to resolve, beneath the auspices of the Worldwide Union for Conservation of Nature. “It’s not clear to me whether or not that can profit this group of bears when it comes to their safety or their total welfare as we go into the long run,” Dr. Amstrup mentioned.
He mentioned he agreed with the researchers that, as he put it, “this isn’t some form of salvation for polar bears.” For one factor, he mentioned, warming is inflicting all types of ice to retreat and disappear, together with glaciers. So the glaciers within the Greenland fjords won’t proceed to terminate within the water and produce glacial mélange ceaselessly. The examine, he mentioned, “is exhibiting a transient profit for these bears.”
“They will survive now, though the ice-free days when it comes to sea ice are too nice,” Dr. Amstrup added. “However going into the long run, that can change until we arrest the rise of worldwide greenhouse gases.”
