Inbreeding occurs in polar bears as their habitat melts

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Inbreeding occurs in polar bears as their habitat melts

The genetic diversity of polar bears is declining due to the effects of climate change, according to a new study.

The research found that there has been up to 10 percent loss of genetic diversity in polar bear populations on the Svalbard Archipelago, Norway, since 1996. In this region, which has been affected by a reduction fast sea ice in the Arctic barents sea, polar bears have turned to inbreeding, due to a limited number of mates.

“Our study is the first to assess the microevolutionary and ecological processes governing the degree and distribution of genetic variation in polar bears in the Svalbard region,” lead author Dr Simo N. Maduna from the Norwegian Bioeconomics Research Institute.

“This has given us the much needed baseline information on the levels of genetic diversity in polar bears during a period of rapid sea ice loss,” he said.

As climate change continues to affect ecosystems across the world, the Arctic has been hit hardest as rates of warming have been higher at the poles. The most significant impact of this increased polar warming is the seasonal sea ice loss, which has serious consequences for all ice-dependent species, such as Adélie penguins, Baltic ringed seals and polar bears.

The loss of sea ice affects the breeding and feeding habits of polar bears. On the Svalbard Archipelago, the study explains, it was habitat fragmentation caused by the loss of sea ice in the Arctic Barents Sea that led to an increase in inbreeding among the local population of polar bears, in the last two generations in particular.

“It was amazing to find such compelling evidence of the loss of genetic diversity and gene flow in just about 20 years. It is clear that the continued decline in the extent of the sea ice is a climate-induced environmental factor of decline in local genetic diversity and exchange between localities, ”Maduna said.

Getty Images: Polar bear in the Norwegian archipelago of Svalbard.  Credit: Patrick J. Endres / Getty Images

Getty Images: Polar bear in the Norwegian archipelago of Svalbard. Credit: Patrick J. Endres / Getty Images

Polar bear in the Norwegian archipelago of Svalbard. (Credit: Patrick J. Endres / Getty Images)

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The research, published by the Royal Society, noted that the resulting decrease in genetic diversity could constitute “an additional level of adversity” for polar bears, reducing their ability to adapt and respond to “anthropogenic pressures. , disease outbreaks and environmental changes. “

Polar bears also depend on the pack ice to hunt their main prey, seals. According to Polar Bears International, polar bears are a “highly specialized” predator of ice seals, specially adapted for tracking seals on ice, where they are stealthy and fast. Although they consume other food sources – including birds, eggs, and small mammals – these species do not provide enough calories to maintain polar bear population levels.

As a result, some researchers have started to report incidents of cannibalism among starving Arctic polar bears. Although cannibalism in polar bears is not uncommon, the principal scientist of the Russian Academy of Sciences Ilya Mordvintsev has noted a recent increase in these cases of intraspecific predation.

Their dependence on a fragmented habitat, melting sea ice, has put polar bears at risk. Divided into 19 distinct populations across the Arctic, polar bears can number as few as 16,000 globally, and most groups, including Svalbard bears, are listed as vulnerable or threatened.

The Canadian population of polar bears on the western shores of Hudson Bay is particularly vulnerable, their numbers having declined by a third since the 1990s, largely due to the reduction in the extent of the ice in sea ​​on the bay.

These urgent threats will carry a “high risk of extinction”, according to the study. The researchers noted that further loss of sea ice would result in “continued erosion of local genetic diversity” and “increased isolation” between groups of polar bears. They call for more “genetic surveillance” and the development of “adaptive management strategies” for ice-dependent species like polar bears.

“We hope that our findings will contribute to policy development and the revision of management plans for the conservation of the genetic diversity of this iconic species,” said Maduna.


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