With global warming, Arctic sea ice is melting at an accelerated rate, endangering the survival of polar bears. But the latest study found that there is an isolated subpopulation of polar bears in southeastern Greenland that has mastered methods of hunting without relying on sea ice, suggesting that some polar bears are able to adapt to climate change. So, can polar bears avoid the doom of extinction from global warming?
Written by | Bianca Nogrady
Compile the | kapok
Edit | Poplar/spruce
Image source | nature/pixabay
Polar bears are one of the most cited and representative potential victims of climate warming. Because most polar bears rely on solid sea ice as a hunting platform, and the current sea ice in the Arctic Ocean is accelerating its melting, this trend will continue, and polar bears will face the threat of starvation. It is estimated that polar bears are likely to be endangered by the end of the century.
Kristin Laidre, an animal ecologist at the University of Washington, led a team into a fjord in southeastern Greenland, and after 7 years of observation and tracking, they found an isolated subpopulation of polar bears that are much less dependent on sea ice, bringing a glimmer of life to the polar bear's unoppotent situation. The study was published June 16 in the journal Science.
Sea ice cover is only about 100 days a year
Greenland's glaciers are melting at an accelerated rate
This subpopulation lives in a fjord in southeastern Greenland, bordered by mountains and ice sheets to the west and oceans to the east. Due to the low latitude of the region, only about 100 days of sea ice are covered throughout the year, and the ice-free period of more than 250 days far exceeds the fasting period of polar bears.
The vast majority of polar bears in the Arctic rely on sea ice to catch seals in the Arctic Ocean, but scientists have found that this subpopulation of southeastern Greenland has hunting platforms throughout the year, using scattered freshwater ice blocks (snow-ice mixtures) that fall from glaciers to ambush seals. So they won't go hungry for most of the year without sea ice.
Satellite tracking data shows that these polar bears don't go far when they go out hunting. When team members venture out of the fjord, their ice platforms are sometimes trapped by rapids off the east coast of Greenland. Ryder, the paper's lead author, said: "Whenever this happens, they jump into the current from a besieged ice platform, swim to shore, and walk home. ”
Of the 27 polar bears the team tracked, female polar bears were only 10 kilometers apart on average in 4 days, while female polar bears living in northeastern Greenland (with higher sea ice coverage) were nearly 40 kilometers old in 4 days.
But that doesn't mean this subpopulation is lazier. About half of their hunting members need to travel 190 kilometers to return to their homes in the fjord. But they know how to make the most of the melting sea ice, and will drift along a fast ocean current along a fast ocean current along the large pieces of ice floes to save energy.
Isolated from the outside world for more than 200 years
The presence of this isolated population suggests that some polar bears may survive global warming
This subpopulation has about 300 polar bears, and the team examined their DNA and found that the population had been isolated from other polar bear populations off the east coast of Greenland for at least 200 years. Scientists propose to divide them into the 20th subpopulation of polar bears in the world.
Not only does this group of polar bears have unique hunting skills, but they are also smaller and the female polar bears fewer cubs. Further research is needed to determine the specific number of this population.
The area is surrounded by ice sheets, mountains and rapids in the east, and the fjord is flanked by steep cliffs, so the habitat is isolated, and the polar bears that live here are genetically different from those in other regions. Elizabeth Peacock, a polar bear biologist at Emory University in the United States, said the newly discovered population in southeastern Greenland is the most genetically unique population of polar bears on record.
The presence of this subpopulation in the context of low sea ice cover suggests that even as the Arctic sea ice line recedes northward every year, polar bears still have a chance to survive. As Ryder puts it, "This small group of genetically distinct bears can reveal how polar bears as a species survive in the ice-free Arctic." ”
Sea ice conditions in the fjords of southeastern Greenland are similar to those in the Arctic after the melting glaciers of the late 21st century, so such an environment could be the last refuge for polar bears. The protection of this new population is essential.
New skills bring new hope?
Polar bears usually use sea ice to hunt, but a newly discovered subpopulation has found another strategy
The discovery of a new subspecies of the polar bear is indeed exciting to researchers. After all, the new skill of preying on seals with freshwater ice offers new hope for how polar bears can adapt to climate change. Does this mean that polar bears can escape the doom of extinction?
Beth Shapiro, a geneticist at the University of California, co-author of the paper, said, "Genetically speaking, they are the most isolated population of polar bears on Earth, and the population is small, slow to reproduce, and small in size." It is difficult to determine whether this subpopulation survived because of different genes or different responses to different climates and habitats. ”
Although this study shows that polar bears are more adaptable to changes in their environment than we thought, this new skill is hardly a "lifesaver" for a long-endangered species.
For example, mammoths became extinct about 3,900 years ago, but according to archaeological data, on Wrangel Island, 140 kilometers off the coast of Siberia, there are still some mammoths that survived for thousands of years, but they also became extinct later.
The newly discovered subpopulation of polar bears may also be no different from the last mammoths, because they are also at risk because of their small size, low birth rate, isolation from the outside world and inbreeding. Perhaps reducing carbon emissions quickly is the surest way to save polar bears.
[Science of the Singularity is the copyright partner of Science Illustrated, a classic European popular science magazine, focusing on reporting exciting cutting-edge technological advances and allowing readers to see the future in advance.] 】
Resources
[1]https://www.nature.com/articles/d41586-022-01691-2
[2]https://www.science.org/doi/10.1126/science.abk2793
[3] Laidre, K. L. et al. SCIENCE, 16 Jun 2022, Vol 376, Issue 6599, pp. 1333-1338