The Polar Bear Future-what can we conserve?

By Dave Armstrong - 07 Dec 2016 9:40:0 GMT
The Polar Bear Future-what can we conserve?

The true nature of the polar bear is rarely seen, except by seals, although the species is also very effective as a hunter on land!

Maritime bear image; Credit: © Shutterstock

Polar bears are simply overgrown Kodiak grizzlies who were bleached by their genes. If that is your opinion, then you could wait a couple of million years for another speciation. On the other hand, it looks fairly certain that we will lose the habitat of sea-ice-laden ocean, the niche of marine mammal predation and the animal itself. The remaining bears will soon have to live almost entirely on land, as global warming will certainly continue for more than a century, even if contained.

That assumption leaves the authors of Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines searching for a projection of population size, leaving the polar bear as vulnerable according to the IUCN.

The systemic approach to these devious calculations involves working out generation length (11.5 years) and developing a standardised measurement for sea-ice-covered days in important habitats (-1.26 days per year). Then the computing of the stats began, assuming a current population of 26,000 animals in 19 sub-populations (in 4 eco-regions circling the Arctic.) Eric V. Regehr and 9 colleagues projected the figures, working in the USFWS, Anchorage, the University of Washington, Stony Brook University, all in the US; Environment and Climate Change, Edmonton, the Ontario Ministry of Natural Resources and Forestry, York University, all in Canada; and the University of Oslo, Norway. The full paper is in the Biology Letters of the Royal Society today.

Polar bears are Ursus maritimus, indicating their niche as the sea-ice. Their recent nutritional stress, owing to the loss of habitat and hence their prey (mainly seals) on the ice, is well-recorded. What seems the most important figure now is their abundance in relation to the loss of the ice. These relationships were positive in that they reflected the correlations between a decline in the sea ice for every sub-populations and their abundance. The Chukchi Sea sub-population were one example of polar bears that were showing high recruitment (loss of cubs as they drown trying to reach land has become common in many populations) and holding their population quite well. Such successful reproductive events totalled 3374, but this success was always accompanied by the dreaded sea-ice loss.

Overall, the potential for large reductions in populations exists for the next 3 projected generations. Ecoregions in NW Canada and eastern Greenland showed non-significant correlation between abundance and declining sea ice, but all other results were significant (at a significance level of 0.01.) This result leaves a high risk of extinction for the wild polar bear, at a vulnerable level in the IUCN category. These enormous bears, with the boars at 700kg (>1500lb), are the only canines to be classified as truly marine. They have now been classed as Vulnerable because of this impending loss of habitat, so we must assume the future for this feared Big Uncle is more than bleak.

One of our many previous reports on the iconic polar bear was this 2011 story on Polar bears and hot potatoes!