Anchorage Daily News

Polar bears will be gone from Alaska within 50 years, government scientists predicted Friday.

Shrinking sea ice will leave only a remnant surviving population of the world's polar bears in the islands of the Canadian Arctic by mid-century, according to a breathtaking new study by the U.S. Geological Survey. Two-thirds of the world's polar bears, including those along the coasts of Alaska and Russia, will have disappeared.

The loss of summer sea-ice habitat will be so profound for bear populations that regional efforts to protect them, such as restricting subsistence hunting or Arctic oil and gas development, will not be able to prevent their disappearance, the government scientists said.

Moreover, the bears' doom is irreversible, the study said. Even a dramatic effort to reduce greenhouse gas emissions would not be enough to halt the near-term warming trend and save the coastal bears. The species might manage to survive in its remnant outposts if long-term warming trends are reversed, scientists said.

"Things could be turned around so that they don't disappear completely," said Steve Amstrup, the biological study team leader for the USGS. On the other hand, Amstrup said, climate-warming models chosen for the study tended to be conservative, so the bears might disappear faster than predicted.

"As the sea ice goes, so goes the polar bear," Amstrup said.

'THREATENED' SPECIES?

The new set of USGS studies, provided to Congress Friday, were undertaken to aid Interior Secretary Dirk Kempthorne's decision whether to designate polar bears a "threatened" species under the Endangered Species Act. A decision is due by next January.

The State of Alaska, fearing consequences for subsistence hunting and oil production, has strenuously opposed a federal threatened-species listing, arguing, among other things, that bear populations have been stable and that too much uncertainty surrounds projections of global warming trends.

State Fish and Game commissioner Denby Lloyd said Friday it was too soon to analyze all the new data to see how they might affect the state's position.

The new studies were introduced in a national teleconference by USGS director Mark Myers, who knows well the potential impact of an endangered-species listing on Alaska. He was head of the state's oil and gas division under Gov. Frank Murkowski.

"The other factors are not a significant stressor to the polar bear," Myers said, responding to a question about subsistence hunting and oil development. "Loss of sea ice is the controlling factor."

ON THINNING ICE

Of the variety of stresses affecting polar bear survival, Amstrup said, 84 percent have been pegged to loss of sea ice habitat.

The picture of doom is even more dire than the one painted by environmentalists when they sued the federal government over polar bears in 2005, prompting the endangered-species review by Kempthorne.

"This is not a reason to despair or give up," said Deborah Williams, president of Alaska Conservation Solutions, an Anchorage-based organization focused on global warming. "Our generation has the ability to write a death sentence for the polar bear, or to take action to assure that the species survives."

Williams said an Endangered Species Act listing would focus new attention on greenhouse gas emissions -- especially those with a shorter life span, such as methane and soot -- and could also help protect any handful of Alaska bears trying to adapt to living on land.

The new study notes that more polar bears are likely to be seen on land as the ice melts, increasing contact with humans in the short term.

Scientists think there are 20,000 to 25,000 polar bears in the world. One-fifth or so live in Alaska and nearby on the coast of the Beaufort and Chukchi seas.

The bears are considered marine mammals because they depend on sea ice for hunting their prey: seals breathing through holes or along the edges of open-water leads.

Polar bears have been known to live as long as 30 years, Amstrup said. That means today's young bears may be part of the last generation in Alaska.

While older bears will probably scrape along, scientists expect to see cubs and young adults die off and reproduction rates decline. Already, studies have reported shrinking weight and rising mortality of cubs. There have also been reports of polar bears drowning.

In their comments Friday, Amstrup and Myers addressed several challenges raised since the U.S. Fish and Wildlife Service undertook its review last December.

BEARS WON'T SURVIVE ON LAND

Amstrup rebutted the idea that polar bears could survive by adapting to land-based hunting. He said studies have shown the bears to be very inefficient hunters of land animals, which in any case do not provide the kind of rich nutrition polar bears seek.

He said the fossil record of polar bears goes back no more than 50,000 years, meaning they would not have had to adapt in the past to any period warmer than the present. If the bears go back more than 200,000 years, however -- and there is some genetic evidence of this, Amstrup said -- then they may have found a way in the past to adapt to an even warmer spell.

Amstrup said bear population trends have sometimes been misunderstood. The numbers have trended upward since the 1960s, he said, as overhunting was stopped internationally and better data became available. But the healthy trend has now been reversed by the new and overwhelming factor of habitat loss.

Time will tell how accurate those predictions of continued warming and sea ice loss will be.

One of the new studies, looking at Beaufort Sea bear populations, examined sea ice in the years 2001-2005. If conditions remain similar to 2001-2003, relatively cold years, the bear population will grow slowly, the study said. If conditions resemble the warm years of 2004-2005, they will "decline precipitously." If conditions toggle back and forth, numbers will decline slowly.

But broadly accepted long-term projections call for the atmosphere to grow progressively warmer than it is now, researchers say. The USGS studies rejected a number of climate models, drawing from the 10 models that had proven most accurate when measured against actual shrinkage in recent years, the scientists said.

"The sea ice in 2007 already has declined below the level projected for mid-century by the four most conservative models in our ensemble," says the main USGS study.

Consensus models project a 40 percent shrinkage of summer sea ice in the Beaufort Sea by 2050 compared to the 1980s, the National Oceanic and Atmospheric Administration said this week.

By that time, the new USGS studies project, the last polar bears on earth will be hiding out in Canada's northern archipelago and along the northwest coast of Greenland.

Contact reporter Tom Kizzia at tkizzia@adn.com.

A study by the U.S. Geological Survey predicts a grim future for polar bears:

• Predicted shrinkage of polar sea ice will result in loss of roughly two-thirds of the world's polar bear populations in the next 50 years.

• Polar bears now living off Alaska coasts -- in the Chukchi and Beaufort seas -- will disappear completely.

• Curbing subsistence hunting and development in the Arctic wouldn't be enough to change the bears' fate.

• Gases already in the atmosphere will keep warming the globe, so even a halt to emissions won't save the polar bears.

U.S. Geological Survey predictions

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