Climate change is starving polar bears endangered, according to research published Monday that predicts that major carnivores could disappear in the course of human life. In some regions they are already caught in a vicious. downward spiral, with shrinking sea ice shortening the time bears have to hunt seals, scientists reported in Nature Climate Change.
The scientists added that their body weight lowers the chances of surviving arctic winters without food.
“The bears face an increasingly long period of fasting before the ice freezes again and they can return to feed,” Steven Amstrup, who conceived of the study and is chief scientist for Polar Bears International, told AFP.
Based on current trends, the study concluded, polar bears in 12 of the 13 sub-populations analyzed will have been decimated within 80 years by the galloping rate of change in the Arctic, which is heating three times faster like the planet as a whole.
“By 2100, recruiting,” new births, “will be severely compromised or impossible everywhere, except perhaps in the Queen Elizabeth Island subpopulation,” said Amstrup in the Arctic archipelago of Canada.
That scenario predicts that the Earth’s average surface temperature will rise 3.3 degrees Celsius above the pre-industrial benchmark. Until now, a degree of warming has caused a crescendo of heat waves, droughts and thunderstorms that the seas grow and destroy.
But even if humanity were able to limit global warming to 2.4 degrees Celsius, roughly half a degree above the goals of the Paris Agreement, but equally ambitious, it would probably only delay the collapse of polar bears.
“The Arctic is warming to 3 times the world average due to human-made climate change … and as a result, the Arctic landscape is changing at an astonishing rate,” said meteorologist and climate specialist for CBS News Jeff Berardelli. “We are running out of time to limit the damage caused by climate change. There is no doubt that we will lose vital species forever. The question is how many are we willing to sacrifice? That will be determined by how quickly and boldly we act to limit climate change and habitat destruction. “
The threat is not rising temperatures per se but the inability of predators at the top of the food chain to adapt to a rapidly changing environment.
“If somehow, by magic, the sea ice could be maintained even as temperatures rise, the polar bears might be fine,” Amstrup said by email.
“The problem is that their habitat is literally melting.”
Half of Earth’s land megafauna is classified as endangered, but only polar bears are endangered primarily by climate change.
But that state may not be unique for long, and should be seen as a harbinger of how the weather will affect other animals in the coming decades, the authors cautioned.
Today there are approximately 25,000 Urus maritimus in the wild.
The challenge to their survival has long been understood, but the new study, which builds on Amstrup’s pioneering work a decade ago, is the first to put a timeline on its likely demise.
The new approach overlaps two data sets.
One is the expanding fasting period, which varies by region and can last half a year or more.
The other is a pair of projections on climate change that follow the decline in sea ice until the end of the century, based on scenarios from the UN’s IPCC climate science advisory panel.
“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 adult survival rates begin to decline,” he said. lead author Peter Molnar, professor at the University of Toronto.
A male bear, for example, in the West Hudson Bay population that is 20 percent below its normal body weight when fasting begins will only have enough stored energy to survive 125 days instead of 200 days.
Newborn puppies are even more exposed, according to the study, especially when mothers haven’t gained enough weight to provide nutritious milk.
However, offspring females have the greatest ability to withstand long periods without food.
The polar bear’s “vulnerable” status on the IUCN Red List of Endangered Species, less severe than “endangered” or “critically endangered,” does not accurately reflect its plight, the authors argue.
The categories established by the International Union for Conservation of Nature are mainly based on threats such as poaching and habitat invasion that can be tackled with local actions on the ground.
“But we cannot build a fence to protect sea ice from rising temperatures,” said Amstrup.
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