The Reid Park Zoo in Tucson, Ariz., hopes to mate Kobe, right, and Boris. Kobe was born at the Roger Williams Park Zoo. Roger Williams’ polar bear display, which closed in 2005, is expected to reopen in 2010.

PHOTO COURTESY OF LESLIE WATERS, REID PARK ZOO

PROVIDENCE — As sea ice in the Arctic Circle melts, the plight of the polar bear has attracted worldwide attention, turning the animal into one of the most powerful symbols of the threat of global warming.

Environmentalists are pushing to list the polar bear as a threatened species under the Endangered Species Act, the first animal that could be included solely because of global warming.

At the Roger Williams Park Zoo, officials support the campaign, which comes at a time when the zoo is creating a new polar bear exhibit that will be the centerpiece of an estimated $13.6-million renovation. The zoo expects to open the exhibit in early 2010.

Tim French, the zoo’s deputy director for animal programs, said many generations of zoo visitors have loved polar bears.

The zoo’s previous polar bear exhibit, which closed in 2005, lasted for 25 years — housing eight bears at different times, including two, Triton and Kobe, who were born at the zoo. The exhibit’s last bear, Trixie, the mother of both Triton and Kobe, died in May 2005 from complications after being sedated to prepare her for a move to a zoo in Indianapolis. Triton, 9, is at the Indianapolis zoo; Kobe, 6, is at a zoo in Tucson, Ariz.; and their father, Norton, 19, is at the Detroit zoo.

French believes the zoo’s planned exhibit will provide a new vehicle to talk about the bears, climate change and what individuals can do to help fight global warming.

“We historically focus more on the altruistic part of conservation, we should really do this because it’s the right thing to do,” French said. “But we need to do a better job helping people to see conservation is for our own benefit as much as anything else.”

The new polar bear display will be nine times larger than the old one. New features will include a cub den for breeding, a digging pit to simulate Arctic tundra, and a large saltwater pool with a glass divider to let polar bears and harbor seals safely swim side by side.

Some of the polar bears’ neighbors will include endangered species that have rebounded, such as bald eagles, bison and red wolves.

The exhibit, which will likely house two or three bears, will be part of the revamped North American Trail, a 3.5-acre display highlighting native animals such as the Arctic fox, harbor seals, pronghorn and snowy owls. Work is already under way to install utilities and build two pedestrian bridges.

Putting the polar bears in the center of the North American Trail shifts the focus on the species whose future is in question, said Jack Mulvena, the zoo director. “The message there is if we put our minds to it, we can make an impact,” said Mulvena, who added that the zoo plans to donate toward helping wild polar bears in the future.

THERE ARE AN ESTIMATED 20,000 to 25,000 wild polar bears on the globe, spread across Canada, Greenland, Norway, Russia and the United States.

Out of the world’s 19 polar bear populations, 5 are declining, 5 are stable and 2 are increasing, according to the polar bear specialist group of the World Conservation Union, an environmental organization. There is insufficient data to determine the progress of the six other populations and the data for one is unknown.

Global warming, many scientists say, poses several problems for polar bears, including earlier melting of sea ice in the spring and delayed freezing in the fall. Polar bears depend on sea ice to hunt for seals, mate and build cub dens.

In 2005 and 2006, winter sea ice decreased by 6 percent, compared with the average 1.5 to 2 percent per decade, according to satellite observations by the National Aeronautics and Space Administration. The NASA study also noted that, at the same time, summer sea ice continues to retreat at an average 10 percent per decade.

While the fate of the polar bear is unknown, there have been noticeable declines and malnutrition in the western Hudson Bay population in Canada, said Bruce Woods, a spokesman for the U.S. Fish and Wildlife Service, Alaska Region. The number of polar bears dropped from 1,194 in 1987 to 935 in 2004, according to a report by the U.S. Fish and Wildlife Service.

In Alaska, the polar bear population is about 4,700, Woods said. There have been some lower weights recorded in Alaska cubs and adult bears, mirroring the earlier situation in western Hudson Bay a few years ago.

Other problems facing polar bears include the possibility of being stranded on ice floes or land, and contamination. Scientists have observed polar bears that have high levels of pesticides and PCBs in their fat tissues, which hinders development and reproduction.

The U.S. Fish and Wildlife Service is reviewing a petition to consider the polar bear threatened, a designation given to a species that could be lost in roughly three generations, or about 45 years. If the polar bear is added to the list, the service will develop a recovery plan to help them rebound. Polar bears are already protected from human taking and importation by the Marine Mammal Protection Act of 1972.

Three public hearings have been held in Alaska and Washington, D.C., on the proposal and the public comment period ends on April 9, Woods said. The scientific review will continue after that and a decision should be made by Jan. 9.

WHEN THE ROGER WILLIAMS PARK ZOO exhibit opens in three years, the zoo plans to have a breeding pair of polar bears.

The ideal population would be one male and two female bears. The zoo does not know where the bears will come from, but will start searching in 2009, said French, the deputy director of animal programs.

If the polar bear does gain threatened-species protection, French said, it probably would not affect the zoo’s polar bear exhibit. The designation might even increase the captive polar bear population because there would be greater efforts to help injured or orphaned wild bears, he said.

What the impact of climate change means to the relationship between polar bears and zoos is unclear.

In the United States, there are 80 bears in 35 institutions. Most polar bears in zoos are born in captivity, with some rescued from the wild.

There may be more orphans in the future because of global warming, said Randi Meyerson, the coordinator of the polar bear species survival plan for the Bear Taxon Advisory Group. The advisory group, which is part of the American Zoological and Aquarium Association, makes recommendation about the placement of bears and when captive bears should breed.

Polar bears have been bred in captivity for more than 50 years, said Meyerson, who also works as the mammal curator at the Toledo Zoo. Detailed records are kept on each bear and breeding is done very selectively, because many zoos do not have enough money or space to maintain a bear. None of the zoo bears is released into the wild.

If the number of wild orphans increases, Meyerson said the Taxon group “may end up doing like grizzlies and black bears: stop breeding and use resources to rescue and create a genetic reservoir, a ‘living sperm bank.’ ”

To learn more about polar bear conservation issues, visit the U.S. Fish and Wildlife Service Web site http://alaska.fws.gov/fisheries/mmm/polarbear/issues.htm. To learn more about polar bears, visit the Roger Williams Park Zoo at www.rogerwilliamsparkzoo.org or the Bear Taxon Advisory Group at www.bearden.org.

Michelle J. Lee is a fellow with the Metcalf Institute of Marine and Environmental Reporting.

mlee@projo.com