Climate change will trigger decline in polar bear population: Study

London, May 26 : A University of Alberta, Edmonton, Canada, study has concluded that climate change will trigger a dramatic and sudden decline in the number of polar bears.

"Some populations are expected to go extinct with climate warming, while others are expected to persist, albeit at a reduced population size," the BBC quoted Dr. Peter Molnar, the lead author of the study, as saying.

Dr. Molnar's research is based on what is known of polar bear physiology, behaviour and ecology, and predicts pregnancy rates will fall and fewer bears will survive fasting during longer ice-free seasons.

Details of the research are published in the journal Biological Conservation.

Until now, most studies measuring polar bear survival have relied on a method called "mark and recapture".

Information that scientists have gathered on polar bear populations varies greatly. For example, datasets span up to four decades in the best studied populations in Western Hudson Bay and Southern Beaufort Sea, but are almost non-existent for bears in some parts of Russia.

Even more difficult is measuring how survival and reproduction might change under future climatic conditions.

"So we've looked at the underlying mechanisms of polar bear ecology to assist our understanding of what will happen in a warming world," Dr. Molnar told the BBC.

Dr. Molnar, Professor Andrew Derocher and colleagues from the University of Alberta and York University, Toronto focused on the physiology, behaviour and ecology of polar bears, and how these might change as temperatures increase.

"We developed a model for the mating ecology of polar bears. The model estimates how many females in a population will be able to find a mate during the mating season, and thus get impregnated."

Male polar bears find females by wandering across ice, sniffing bear tracks they come across. If a female has made the tracks in mating condition, the male follows the tracks to her.

The researchers modelled how this behaviour would change as warming temperatures fragment sea ice. They also modelled the impact on the bears' survival.

By developing a physiological model that estimates how fast a bear uses up its fat and protein stores, the researchers could estimate how long it takes a bear to die of starvation.

"In both cases, the expected changes in reproduction and survival were non-linear," explains Dr. Molnar.

"That is, as the climate warms, we may not see any substantial effect on polar bear reproduction and survival for a while, up until some threshold is passed, at which point reproduction and survival will decline dramatically and very rapidly," he said.

The US Endangered Species Act lists the polar bear as "Threatened".

The new study by Dr Molnar's team offers a way to improve these predictions, and suggests the potential for even faster declines than those found by the US assessment.

--ANI