Polar bear numbers could drop by a third in 40 years, research says

Polar bear numbers could drop by a third in the next 40 years because of melting Arctic sea ice, according to scientists.

Experts have calculated there is a 71% likelihood that polar bear numbers will be reduced by more than 30% in three generations.

This means the current population of some 26,000 bears could be cut to around 17,300 over 35 to 41 years.

The findings are consistent with the animals being listed as "vulnerable" on the International Union for Conservation of Nature (IUCN) red list of threatened and endangered species.

The loss of sea ice caused by climate change is having a direct impact on the ability of polar bears to feed and survive.

The bears need platforms of ice to reach their prey of ringed and bearded seals. Some sea ice lies over more productive hunting areas than others.

Polar bears have been divided into 19 sub-populations by scientists, two of which have already experienced population declines because of shrinking sea ice.

Others have displayed signs of "nutritional stress" or are currently said to be "stable" or "productive", according to the authors of the study.

The researchers looked at polar bear generational length and sea ice projections based on satellite data and computer simulations.

They calculated the probability that reductions in the mean global population size of polar bears will be greater than 30%, 50% and 80% in the space of three generations.

While the chances of a more than 30% loss were high, there was little likelihood of numbers hitting near-extinction levels.

Writing in the Royal Society journal Biology Letters, the team, led by Dr Eric Regehr from the US Fish and Wildlife Service, concluded: "Our findings support the potential for large declines in polar bear numbers owing to sea ice loss."

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