Polar Bears Are Increasingly Inbreeding As Arctic Sea Ice Melts
A new study looking at populations of polar bars in the Svalbard Archipelago has found the loss of sea ice is causing an increase in inbreeding.
The findings come from small tissue samples collected from the polar bears inhabiting Svalbard’s islands in the Arctic Ocean by a team at the Norwegian Polar Institute in Tromsø, which has been collecting the samples since 1995.
Upon comparing the samples to those taken in 2016, the team found that ‘major demographic changes’ had taken place among the animals, with their genetic diversity around 10% lower in 2016 than they were in 1995.
The loss of genetic diversity, which the researchers describe as ‘alarming’, is thought to be down to melting sea ice, which has caused water barriers to remain open for increasingly long seasons. As a result, polar bears have less opportunity to migrate between subpopulations in order to mate, meaning they instead turn to inbreeding within their own habitats.
Commenting on the findings, per Sky News, the researchers wrote:
The magnitude and rate of loss of genetic diversity and gene flow that we observed is alarming considering that polar bears have historically shown relatively little genetic differentiation even on a global scale, but now are facing increasingly strong climatic selective pressure.
The study found the west coast of Spitsbergen experienced the greatest loss of sea ice in the Barents Sea region, and notably the polar bears in this area also showed the highest rate of change in genetic diversity.
The results of simulations suggested that further loss of sea ice will lead to the continued erosion of local genetic diversity in polar bears of the Svalbard Archipelago and to increased isolation between local areas, especially if there is a concurrent decrease in the number of bears.
A continued increase in inbreeding is expected to cause what is known as ‘inbreeding depression’ – the reduced survival and fertility of young polar bears conceived by related individuals.
There are currently around 20,000-30,000 polar bears left in the world and approximately 3,000 in the Svalbard archipelago and Barents Sea, but their status is classed as vulnerable, with their habitats and ability to hunt prey set to become even more restricted as a result of continued global warming.
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