Climate change could mean the near-extinction of polar bears by the end of the century, a new study has warned.
The gradual disappearance of their habitat due to shrinking sea ice is cutting short the time bears have for hunting seals, scientists said in a report published in Nature Climate Change on Monday.
"The bears face an ever longer fasting period before the ice refreezes and they can head back out to feed," Steven Amstrup, chief scientist of Polar Bears International who came up with the study, told AFP.
The carnivores, which live in Arctic regions where temperatures can drop as low as -40°C in winter, can fast for months, especially during the summer when ice melts every year.
But with global warming, the time period without ice is lasting longer and longer. Unable to find an alternative food source to seals, more and more hungry bears are venturing further from their usual territories, closer to inhabited areas.
According to current trends, polar bears in 12 of 13 subpopulations analysed will have been decimated within 80 years by the galloping pace of change in the Arctic, which is warming twice as fast as the planet as a whole, the study found
There was not enough data for six others to make a judgement on their fates.
"By estimating how thin and how fat polar bears can be, and modelling their energy use, we were able to calculate the threshold number of days that polar bears can fast before cub and adult survival rates begin to decline," said lead author Peter Molnar, a professor at the University of Toronto.
Females are worst-affected by the phenomenon as they go into their dens in autumn ready to give birth in mid-winter and emerge in the spring with their cubs, according to the study.
"They must then catch enough seals to store enough fat and produce enough milk to feed their cubs throughout their summer fast," said Amstrup.
By 2100, new births "will be severely compromised or impossible everywhere except perhaps in the Queen Elizabeth Island subpopulation," in Canada's Arctic Archipelago, he added.
The scenario in the study predicts the average surface temperature of the earth rising 3.3°C above the preindustrial benchmark — 1°C of warming so far has caused heatwaves and droughts among other such natural events.
Scientists paint a bleak picture if we continue down the same path and even if we could cap global warming at 2.4°C, which is 0.5°C above goals outlined in the Paris Agreement but remains ambitious, this would probably only save to delay the polar bears' demise.
"The only way to save them is to protect their habitat by halting global warming," said Amstrup.
"If somehow, by magic, sea ice could be maintained even as temperatures increase, polar bears might be fine.
"The problem is that their habitat is literally melting."