Most polar bears could have a hard time surviving in the Arctic by 2100, study finds

A neighborhood invaded by polar bears 0:32

(CNN) - There is an animal that comes to mind for many people when they think of creatures that are threatened by climate change: the polar bear.

In recent years, images of emaciated bears desperately foraging for food have turned the Arctic apex predator into a vivid portrait of the effects of global warming.

• READ: Polar bears are getting thinner and have fewer cubs. Melting sea ice is to blame

Now, as the planet continues to heat up rapidly, a new study brings another serious warning: if humans don't cut greenhouse gas emissions, most populations of this iconic species may have a hard time surviving beyond 2100. .

Some populations have likely already crossed key thresholds that will make their survival difficult, and perhaps impossible, according to the findings of the study published Monday in the journal Nature Climate Change .

However, there is a ray of hope that some bears can be saved.

Although the number of polar bears is likely to drop dramatically in some regions, moderate cuts in heat-trapping gas emissions in the coming decades may allow them to persist in some parts of the Arctic.

Bears depend on Arctic sea ice

A polar bear cub photographed in Svalbard, Norway.

Polar bears are the largest land carnivores on Earth, but their fate is closely related to what happens to Arctic sea ice.

Bears rely on ice as a platform to catch seals - their preferred prey - because they are not skilled enough swimmers to hunt them in open water, says Péter K. Molnár, assistant professor at the University of Toronto Scarborough and one of the authors of the study.

• READ: The European hamster and the North Atlantic right whale are among the new critically endangered species

Polar bear life has always been characterized by periods of abundance and famine. In winter, when sea ice is at its greatest extent, bears try to gorge themselves on seals for energy reserves to survive the meager summer months when the ice melts and they are forced to land.

But as the region's sea ice declines as it has in recent decades, bear populations in some parts of the Arctic are forced to go increasingly without food.

"Ultimately bears need food and to have food they need ice," explains Molnár. "But for them to have ice, we need to control climate change," he adds.

The researchers' first challenge was to find out how long bears can fast in different regions before adult reproduction and survival are affected.

The study found that how long a bear can survive without food varies by region and animal condition, but that cubs are the first to feel the impact of prolonged fasting.

• READ: A heat wave in Antarctica melted 20% of an island's snow in nine days

Adult females with cubs are generally the second most vulnerable, followed by adult males, and lastly solitary females, who in some cases can fast for a staggering 255 days before their chances of survival abruptly decrease, researchers estimate. .

Then, looking to see how long bears might be forced to live without food in the future, the researchers studied projections for Arctic sea ice under two different scenarios of climate change.

Arctic sea ice has declined dramatically in recent decades, particularly during the summer.

The past 13 years, from 2007 to 2019, have been the lowest 13 years of summer sea ice in the satellite record, dating back to 1979, according to Walt Meier, senior research scientist at the National Snow and Ice Data Center .

Since the mid-1990s, the Arctic has experienced warming levels that are more than double the world average. Exceptionally high air temperatures are behind the decline in sea ice and are primarily driven by the burning of fossil fuels, Meier says.

Looking ahead, other studies have found that the Arctic may not have summer ice in the near future like 2040 or 2050.

"The question is not 'if' we will see an ice-free summer in the Arctic, it is 'when'," Meier explains.

"They are not completely condemned if we change our behavior"

By combining estimates of how long polar bears can fast with projections of Arctic sea ice, the researchers were able to estimate for the first time when polar bears in 13 different regions might face problems in the future.

Some populations, such as those in Canada's Hudson Bay, may have already crossed certain thresholds that will affect reproduction and survival.

• READ: Snow is turning green in Antarctica (and climate change will make it worse)

And the future will likely look much worse for bears without efforts to curb global warming.

Under a climate scenario with no change in human actions, where greenhouse gas emissions are not reduced, almost all Arctic polar bears - except for perhaps a few groups in the remote Queen Elizabeth Islands of Canada - They could be struggling to survive by 2100, according to the study.

However, if humans are able to achieve moderate cuts to global emissions, the chances that bears in other regions will persist beyond the end of this century increase.

The authors say that ultimately the findings show that the fate of polar bears is in our hands.

"I am well aware that the story we are telling is bleak," says Molnár. "But there is also an element of hope, that they are not completely doomed if we change our behavior," he says.

ArcticGlobal warming polar greenhouse gas emissions