Many polar bear populations are at risk of disappearing in the short term due to climate change.
The earth is warming up, and especially in the Arctic, temperatures are rising rapidly. Among other things, it results in melting sea ice. Previous studies have already shown that this is a major problem for the polar bear, which hunts seals from that sea ice. In a new study, scientists have looked at how the disappearance of sea ice is exactly changing the future of the polar bear. And it doesn’t look good, as can be read in the journal Nature Climate Change. If global warming continues at this rate, most polar bear populations will have collapsed by the end of this century.
The diet of polar bears consists mainly of seals. And the bears can only get hold of the seals from the sea ice. As sea ice decreases much more than usual during the summer, polar bears are forced to leave the sea ice and flee to land. However, there is nothing to be gained from that. It means that polar bears eat less.
“The problem is that sea ice continues to disappear as long as the earth warms,” says researcher Péter Molnár. “This means that polar bears have to do without food for extended periods of time, and that affects their reproduction, chances of survival and the survival of healthy populations.”
The researchers determine in their study how many days in a row polar bears can do without food and at the same time manage to raise their young and stay alive themselves. They then use climate models to look at how long polar bears are unlikely to have access to sea ice and therefore food in future years. By combining these data, the researchers can determine when the polar bears’ chances of survival are really compromised and when the polar bear populations will start to collapse.
The research paints an unseeded picture. If the warming continues at the current rate, the researchers say we can expect the survival and reproductive chances of almost all polar bear populations to decrease dramatically. And most populations will disappear by the end of this century.
“While our predictions about the future of polar bears are terrible, unfortunately they are probably still too optimistic,” Molnár says. “This is when we assume, for example, that the polar bears will make optimal use of their available body energy when they fast. If not, the reality could be much worse than our predictions.”
But the predictions don’t have to become reality, the researchers also stress. In their study, they assume a situation in which warming continues. If we reduce our emissions, we can limit warming and the impact it has on polar bears. “We found that a small reduction in emissions leads to polar bears continuing to exist longer,” says researcher Steven Armstrup. “But it probably will not prevent quite a few populations from disappearing anyway, and that highlights how important it is that we are much more ambitious when it comes to reducing our emissions.” For example, polar bears in their current habitat would continue to exist if we succeeded in limiting global warming to 2 degrees Celsius. It is an ambitious climate goal that – if we act quickly – is still within reach.
The researchers looked in their study at polar bear populations that make up 80% of the total population. The polar bears that populate the Canadian Arctic Islands – and make up 20% of the global population – were excluded because there was not enough data available. However, the researchers suspect that these polar bears face the same fate as the populations studied.