Polar bears have long been the models for the consequences of climate change. A new study now suggests that the arctic species may starve by the end of the century.
As sea ice continues to disappear due to warming temperatures, polar bears are finding it increasingly difficult to find the food they need to survive, according to the University of Toronto study published Monday in the scientific journal Nature Climate Change.
There are an estimated 22,000 to 31,000 polar bears in the wild, according to the World Wildlife Fund, although exact numbers are difficult to determine due to their remote habitat. The species is classified as vulnerable.
Polar bears depend on sea ice to hunt seals, their main source of food, according to the new study. But the spread of ice has diminished as climate change speeds up temperatures at the poles, keeping them in land where seals are more difficult to catch.
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While bears can fast for months on end, their survival depends on how much energy they have managed to reserve by eating ahead, how much energy they expend during the fast, and how long a period of fasting, according to the study.
Researchers admit that it’s unclear exactly how long bears can withstand the fast before it affects their ability to reproduce or their individual mortality.
But in at least two regional groups of polar bears, prolonged fasting periods have already been shown to negatively affect their body condition, reproduction rates and the size of their populations, according to the study.
This trend is expected to be seen in arctic polar bear groups as ice loss continues.
The adaptive capacity of the species is also in doubt. At the end of the last Ice Age, polar bears failed to move and survive on land and instead migrated further north. “Foods that meet the energy needs of polar bears are largely unavailable on earth,” the study said.
The Arctic was expected to warm twice as much as the global average in 2020 compared to pre-industrial temperatures, according to the World Meteorological Organization.
This contributed to some of the lowest sea ice levels on record. In September, after the summer melt season, sea ice declined more than 50% from the 1979 to 2019 average, the organization reported.
This is already having disastrous consequences. In Siberia, a prolonged heat wave that began in January sparked forest fires that burned more than 2.8 million acres in late June.
An analysis conducted by the UK Met office and published last week found that the prolonged heat wave was 600 times more likely due to man-made climate change.
Polar bears, along with the rest of the Arctic environment, are not hopeless, however.
“Ultimately, aggressive mitigation of greenhouse gas emissions will be necessary to save polar bears from extinction,” the recent study says.