According to a new study published in the journal Nature Climate Change, polar bears may face extinction by the end of the century as a result of reduced sea ice in the Arctic caused by climate change.
Although the study did not predict that all polar bears would become fully extinct by 2100, it estimated that 13 of the 19 Arctic polar bear subpopulations, representing approximately 80% of the species, are likely to die due to famine and failure. reproductive. The researchers said the estimate was “probably conservative” based on the current rate of ice loss, and predicted that some subpopulations would die out even earlier.
“There is very little chance that polar bears will persist anywhere in the world, except perhaps in the very high Arctic in a small sub-population” if global temperatures continue to rise to the current level, Peter Molnar, professor at the University of Toronto Scarborough and the study’s lead author, told The New York Times. Even if emissions are moderately reduced in accordance with the Paris Climate Agreement “unfortunately we will still lose some, especially some of the southernmost populations, due to the loss of sea ice,” he said.
Shrinking sea ice is forcing polar bears to move to land, taking them away from their food supply for extended periods, according to the study. Longer “fasting season” and declining reproduction “will jeopardize the persistence of all but a few sub-populations of the High Arctic by 2100,” the study said. “Moderate emission mitigation prolongs persistence but is unlikely to prevent the extinction of some sub-populations.”
“Previously, we knew that polar bears would eventually disappear unless we stopped the rise in greenhouse gases. But knowing when they will begin to disappear in different areas is critical to informing management and policy, and inspiring action,” Steven Amstrup, the chief scientist at Polar Bears International and co-author of the study, said in a statement. “We found that moderate emission reductions can prolong global persistence, but they are not likely to prevent the extirpation of multiple populations, emphasizing the urgency of more ambitious emission cuts.”
There are around 25,000 polar bears living in the Arctic. They mainly live on sea ice so they can hunt seals. But due to the melting of the ice, more bears are forced to land during the spring and summer. Ice during the summer months has decreased at an average rate of 13% per decade since 1980, according to the National Oceanic and Atmospheric Administration. Many parts that previously had ice throughout the year now do not have ice during the summer months.
“You need sea ice to catch your food,” said Molnar. “There is not enough food on land to sustain a population of polar bears.”
Polar bears can fast for months, but the rate of ice melt suggests that they will soon be forced to land for longer periods, meaning they will have to fast more than they are capable of.
“Terrestrial feeding is unlikely to occur at scales that change the terms for recruitment and decrease survival in more than a few years, because food that meets the energy demands of polar bears is not available on land.” said the study.
That leaves polar bears essentially hungry.
“There will be a time when you will run out of energy,” Molnar said. “Bears not only have to fast longer and need more energy to overcome this, but they also have a harder time accumulating this energy.”
The reduced energy will also affect other factors in the polar bear’s existence, such as finding a mate, causing reproduction levels to plummet. Having less energy can also affect the bears’ ability to produce milk to feed their cubs.
“What we have shown is that, first, we will lose the puppies’ survival, so the puppies will be born, but the females will not have enough body fat to produce milk to carry them through the ice-free season.” Amstrup told the BBC. “Any one of us knows that we can only go without food for so long. That is a biological reality for all species.”
The study modeled the bears’ physical conditions and calculated the amount of time they could reasonably quickly.
“By estimating how lean and fat polar bears can be, and modeling their energy use, we were able to calculate the threshold number of days that polar bears can fast before cub and / or adult survival rates begin to decline” Molnar said in a statement.
The researchers discovered that the length of the fasting season will soon exceed the bears’ physical abilities.
“By intersecting these fasting impact thresholds with the projected future number of days that sea ice will be absent, we were able to project when fasting impact thresholds will be exceeded in different parts of the Arctic,” said Cecilia Bitz, climate scientist at the University . Washington and co-author of the study.
Molnar described polar bears as the “poster child for climate change.”
“Polar bears have been considered messengers of the symptoms of climate change that will affect all life, including humans,” said Amstrup. “We know that floods, droughts, and forest fires will become more frequent and severe as the world continues to heat up, but the timing for such events is difficult to predict … Show how imminent the threat is to different bear populations. Polaris is another reminder that we must act now to avoid the worst future problems we all face. “
Andrew Derocher, a professor at the University of Alberta who studies polar bears, told The Times that the study’s findings “are very consistent with what we are seeing” when observing animals in the wild.
“The study clearly shows that polar bears will do better with less warming,” he said. “But no matter what scenario you look at, there are serious concerns about the conservation of the species.”
Another study published in the journal PLOS ONE in 2016 found that polar bears in the Beaufort Sea near Alaska and western Canada were three times more likely to land ashore during the summer than in the 1980s. Bears now they spend an average of 31 more days a year on land than three decades earlier.
That has contributed to a 40% decrease in the population of the region’s polar bear population. Bears in the Beaufort Sea also experience less weight, poorer body condition, and shorter cub survival than other similar subpopulations.
In Russia, authorities had to declare a state of emergency last year after a remote region of the village called Novaya Zemlya was invaded by dozens of hungry polar bears.
“I have been to Novaya Zemlya since 1983, but there has never been an invasion of polar bears before,” Zhiganshi Musin, head of administration for the region, told reporters. “They literally chase people and enter the entrances of residential buildings.”
“Everyone understood that this could happen,” Mikhail Stishov, coordinator of the World Wildlife Fund project on Arctic biodiversity, told a Russian news agency. “Now the bears are increasingly on the coasts due to the absence of ice for long periods. They come to the coast, where they get used to human habitation.”
