The loss of sea ice linked to climate change is pushing polar bears to the brink of extinction. Even if we limited global warming now, most of the bear subgroups would still be lost.
Climate change is starving polar bears, according to a study published June 21. The research, published in the scientific journalNature Climate Change , predicts that one of the two largest land carnivores may become extinct by the end of this century.
Polar bears require sea ice to catch seals, their main food. As global warming and sea ice loss continue, its population is expected to decline considerably.
This new study is the first to put a timeline on their possible disappearance: 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.
Sufficient data are not yet available for the other sub-populations to determine their fate. Scientists estimate that fewer than 26,000 polar bears remain, distributed in 19 subpopulations from the ice landscapes of Svalbard, Norway, to the Hudson Bay in Canada and the Chukchi Sea between Alaska and Siberia.
The study considered a scenario in which the average temperature of the Earth's surface will rise 3.3 degrees Celsius above the pre-industrial benchmark. So far, one degree of warming has caused heat waves, cyclones and a series of disasters in the last five years.
The Arctic is already warming twice as fast as the planet as a whole. Even if humanity were able to limit global warming, an enormously ambitious undertaking, most subgroups would still be lost.
Polar bears on the red list
The scientists also add that the "vulnerable" status of polar bears on the International Union for Conservation of Nature (IUCN) Red List of Endangered Species does not accurately reflect their plight. The categories established by the IUCN are primarily based on threats such as poaching and invasion of habitats that can be addressed with local action on the ground.
“Think of it this way: If you were to push it off the roof of a 100-story building, would your level of risk be 'vulnerable' until it passed through the 10th floor? Or would he be ‘in danger’ until the end? "Said in a note with AFP, Polar Bears International chief scientist Dr. Steven Amstrup, who participated in the study and added:" The only way to save them is to protect their habitat by stopping global warming. "
The threat to bear survival is not rising temperatures per se, but rather the inability of predators to adapt to a rapidly changing environment that is the consequence of rising temperatures.
Declining sea ice has reduced the time bears have to hunt for food. This has forced the animals to land, further away from their food supplies, for longer periods.
Prolonged fasting and reduced lactation of puppies due to insufficient nutrients and available energy will lead to a rapid decline in reproduction and survival.
"What we have shown is that, first, we will lose the survival of the cubs, so the cubs will be born, but the females will not have enough body fat to produce milk to carry them during the ice-free season," Amstrup confided toBBC News.
No energy reserves
The new approach overlays two data sets: one is the expanding fasting period for polar bears, the period between two hunts, and the second is climate change projections that track the decline in sea ice to 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.
Scientists say their declining body weight weakens the bears' chances of surviving arctic winters without food. "Bears face an increasingly long period of fasting before the ice refreezes and they can return to feeding," Amstrup said.
While fasting, bears move as little as possible to conserve energy. However, the loss of sea ice and population decline create more problems: the bears have to expend more energy looking for a mate. This, in turn, affects survival.