Impact of Holocene environmental change on the evolutionary ecology of an Arctic top predator

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https://www.science.org/doi/10.1126/sciadv.adf3326

By MICHAEL V. WESTBURY et al, Science Advances. 

Excerpt: The Arctic is among the most climatically sensitive environments on Earth, and the disappearance of multiyear sea ice in the Arctic Ocean is predicted within decades. As apex predators, polar bears are sentinel species for addressing the impact of environmental variability on Arctic marine ecosystems. ...we investigate how Holocene environmental changes affected polar bears around Greenland. We uncover reductions in effective population size coinciding with increases in annual mean sea surface temperature, reduction in sea ice cover, declines in suitable habitat, and shifts in suitable habitat northward. ...[over the past 11,000 years...Whenever temperatures rise, polar bear populations crash. For example, about 4500 years ago, sea surface temperatures climbed by 0.2°C, sea ice cover shrank by about 3%, and polar bear populations dropped by about 20%. Several thousand years before that, when water temps rose 0.5°C, their populations plummeted about 40%. “We see a disturbing connection between population decline and environmental changes,” says study co-author Michael Westbury. “The relationship is not linear.” In the next century, sea surface temperatures are expected to rise as much as 2 to 5°C—an order of magnitude more of a temperature increase than the animals faced before. “It doesn’t look good for the polar bear,” says co-author Eline Lorenzen....

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