A third of all the world’s polar bears are likely to be dead in 40 years, according to a new study.

There is a 71 per cent likelihood that the polar bear population will be wiped out by at least 30 per cent in three more generations, at the research claims.

The massive reduction in the population would be the result of the increased threat of global warming. That is leading the polar sea ice to melt and leaving the bears without the platforms that they need to hunt and survive.

That’s likely to cut down the polar bear population from 26,000 to about 17,300 in the next 35 to 41 years.

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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%, 50% and 80% in the space of three generations.

While the likelihood of a more than 30% loss was high, there was little chance of populations crashing to 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."