A new report on two polar bear populations in Canada’s high Arctic has found that contrary to previous assumptions, their numbers appear to have stabilized. Yet the comprehensive three-year study also found that sea ice concentrations in the area have dramatically decreased, resulting in significant habitat loss and polar bears in worse physical condition.
Researchers with the Canada-Greenland Joint Commission on Polar Bear assessed the Baffin Bay and Kane Basin polar bear populations bordering sections of Nunavut and Greenland and found that both groups had numbers higher than was assumed, based on the last count conducted in 1997. Using aerial surveys, biopsies of tissue samples obtained by darting and the capture and satellite tagging of 125 bears, the research team found that the Baffin Bay bears, which were last counted at 2,074 twenty years ago, have kept relatively stable in numbers and actually increased slightly to 2,826.
Numbers for the Kane Basin group grew from just 164 in 1997 to 357. “These changes suggest the subpopulation is currently healthy and stable. This finding is contrary to a lower estimate of abundance obtained from previous modelling,” says the report, which revises the previous designation of the Kane Basin bears as a declining subpopulation.
Yet the data on sea ice concentrations showed that the length of winter ice coverage in Baffin Bay had decreased by 12 days per decade since 1979, provoking a change in habitat for the polar bears. “In the 2000s, polar bears spent significantly more time on land on Baffin Island, and arrival dates on Baffin Island in summer were one month earlier in the 2000s than in the 1990s,” the report says. “The amount of time bears spent on land has increased by 20-30 days since the 1990s.”
For the Kane Basin population a bit further north, the change was even more marked, as sea ice has gone from virtually year-round coverage to a retreat during the spring and a full melt in the summer.
Spending more time on land rather than ice has kept the bears at a distance from their prime food source, seals, resulting in bears that are thinner and who are spending less time in maternity dens, which has cut into survival rates of newborn cubs. “Body condition in the Baffin Bay polar bears declined in close association with the duration of the ice-free period,” says the report.
While the study also aimed at providing guidance on the contentious issue of quotas for polar bear hunting, the researchers declined to do so, offering instead that whereas quotas are typically based on current populations (polar bear abundance), the ongoing environmental changes should now be taken into consideration when making up quotas. “The ultimate threat to polar bears throughout their range is the reduction in sea-ice habitat, expanse, duration and quality as a consequence of climate change,” the report’s authors say. “Hence, the effective and sound management of polar bears can no longer rely solely on estimates of abundance but must also incorporate impacts of a changing environment.”
The current quota for Baffin Bay polar bears, jointly agreed upon by Canada and Greenland, is an allowable harvest of 132 per year, while for the Kane Basin group, the quota currently stands at 11 per year.