Captivity could help polar bears survive global warming assault, some zoos say

Polar bears are ideally suited to life in the Arctic: Their hair is without pigment, blending in with the snow; their heavy, strongly curved claws allow them to clamber over blocks of ice and snow and grip their prey securely; and their rough pads keep them from slipping.

The one thing they cannot survive is the disintegration of the ice. They range across the sea ice far from shore to hunt fatty seals, whose blubber sustains them.

Heat-trapping greenhouse gas emissions caused by burning fossil fuel are making the Arctic warm twice as fast as lower latitudes, and Arctic summer sea ice could disappear by 2030, according to climate models.

So a group of activists, zoo officials, lawmakers and scientists have a radical proposal: Increase the number of polar bears in U.S. zoos to help maintain the species’ genetic diversity if the wild population plummets.

In a worst-case scenario, a remnant group of bears would survive in captivity.

That should be good news for the St. Louis Zoo, which designed a $20 million polar bear exhibit with a cooled saltwater pool and concrete cliffs covered in simulated ice and snow for three to five bears. Its goal was to have them there by 2017. But it doesn’t have a bear lined up, because it’s illegal to import them, captive cubs are rare and finding orphaned bears in Alaska is difficult.

The Fish and Wildlife Service could allow the importation of polar bears for public display through future legislative or regulatory changes but has shown no inclination to pursue those options.

Evolved from brown bears tens of thousands of years ago, polar bears have become an iconic species for their majestic size and ability to thrive in the harsh Arctic. Today the image of a mammoth bear clinging to a piece of ice embodies an environment under siege.

Polar bears would prefer to hunt for seals year-round, but the disappearance of sea ice has forced them onto land or far offshore where the ice remains only over deep unproductive water. “Either way, they’re food deprived,” said Steven C. Amstrup, chief scientist for the advocacy group Polar Bears International and an emeritus researcher with the U.S. Geological Survey.

Advocates of the plan to bring more into captivity, including St. Louis Zoo president and chief executive Jeffrey Bonner, say that saving a species whose habitat is disappearing is an immense challenge.

“Polar bears are simply the first species where we have to get it right,” Bonner said. When it comes to research on how to sustain an exotic species through breeding techniques, “that research is only research that can be done in zoos,” he added.

Based on current projections, federal scientists say two-thirds of the world’s polar bears could be extinct by mid-century, though a significant cut in greenhouse gas emissions could help halt that decline. There are roughly 20,000 to 25,000 polar bears worldwide, 3,500 of which live in Alaska and spend part of the year in Canada and Russia.

There are 19 sub-populations of polar bears living in Canada, the United States, Russia, Denmark and Norway, and since scientists fear ice melt could cause some of these to disappear from their historic ranges, the idea would be to preserve enough genetic diversity in captivity to allow them to be repopulated through artificial insemination of wild bears or other methods. Supporters of the plan say researchers are just beginning to experiment with assisted reproduction techniques for polar bears.