A third of the world's polar bears could disappear in the next 40 years because of melting Arctic sea ice, say scientists.

There is a 71 per cent likelihood that polar bear numbers will be reduced by more than 30 per cent in three generations, experts have calculated.

That means the current population of some 26,000 bears could be cut to less than 9,000 over 35 to 41 years.

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

Loss of sea ice due to climate change has 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.

Scientists have divided polar bears into 19 sub-populations, two of which have already experienced population declines due to shrinking sea ice.

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

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

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

While the likelihood of a more than 30 per cent loss was high, there was little chance of populations crashing to near-extinction levels.

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