Global Warming Can Make Polar Bears Extinct by 2100

Climate change is literally starving polar bears into extinction, according to a study published on June 21. The research published in the science journal Nature Climate Change, predicts that these carnivores can be extinct by the end of this century.

Polar bears require sea ice for capturing seals, their primary food. But as global warming and sea ice loss continue, their population is expected to heavily fall. And this new study is the first to put a timeline on their likely demise. It concludes that polar bears in 12 subpopulations of the Arctic, almost 80 percent of the total population, will be decimated in less than 80 years. Enough data for the other subpopulations isn’t available yet to determine their fate. Scientists estimate that there are fewer than 26,000 polar bears left, spread out across 19 subpopulations from the icescapes of Svalbard, Norway, to Hudson Bay in Canada to the Chukchi Sea between Alaska and Siberia.

The threat to their survival is not directly rising temperatures, but the predators' inability to adapt to a rapidly shifting environment that is the consequence of these rising temperatures. Shrinking sea ice has cut short the time bears have for hunting food. This has forced the animals onto land—further away from their food supplies—for longer periods. And so, prolonged fasting and reduced nursing of cubs due to insufficient nutrients and energy available would lead to rapid declines in reproduction and survival. "What we've shown is that, first, we'll lose the survival of cubs, so cubs will be born but the females won't have enough body fat to produce milk to bring them along through the ice-free season,” Dr Steven Amstrup, chief scientist of Polar Bears International, who was also involved in the study, told BBC News.

The new approach overlays two sets of data: one is the expanding fasting period of polar bears i.e. the period between two hunts, and the second is climate change projections tracking the decline of sea ice until the end of the century. By estimating how thin and fat polar bears can be, as well as their energy use, they calculated the number of days polar bears can fast before survival rates begin to decline.

The scientists say that their dwindling bodyweight undermines their chances of surviving Arctic winters without food. "The bears face an ever longer fasting period before the ice refreezes and they can head back out to feed," Amstrup told AFP. While fasting, bears move as little as possible to conserve energy. But sea-ice loss and population declines create subsequently more problems—having to expend more energy searching for a mate—which, in turn, further affects survival.

That scenario foresees the earth's average surface temperature rising 3.3 degrees Celsius above the preindustrial benchmark. One degree of warming so far has triggered heatwaves, cyclones, and a host of disasters in the past five years itself. And the Arctic is already warming twice as fast as the planet as a whole. But even if humanity were able to cap global warming—a hugely ambitious venture—most of the subgroups would still be lost.

The scientists also add that the polar bears' ‘vulnerable’ status on the International Union for the Conservation of Nature (IUCN) Red List of endangered species does not accurately reflect their plight. Categories established by the IUCN are based mainly on threats such as poaching and habitat encroachment that can be addressed with local action on the ground.

"Think of it this way: If I were to push you off of the roof of a 100-story building, would your risk level be 'vulnerable' until you pass by the 10th floor?," added Armstrup to AFP. "Or would you be 'endangered' all the way down? The only way to save them is to protect their habitat by halting global warming."

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