When Congress takes up the knotty issue of climate change this fall, lawmakers will wrestle with the complexities of a cap-and-trade system — the most widely touted approach to fight global warming.

It may be simpler — and more effective — to look to the polar bear instead.

The Bush administration is entering the final weeks of a yearlong examination into whether the bear deserves protection under the Endangered Species Act. And environmentalists and industry groups squaring off in the debate agree that the decision could impact climate policy as much as any legislation emerging on Capitol Hill.

The stakes are high because if the Fish and Wildlife Service — the Department of Interior office examining the status of the polar bear — decides to designate the animal as endangered, the agency is required by law to formulate a recovery plan.

And unlike every endangered listing to date, in which species have been threatened by pollution or habitat destruction in their own backyard, many experts believe that global warming is responsible for melting the Arctic ice that serves as the bears’ hunting platform.

“The environmentalists are trying to get a backdoor climate change act by listing the polar bear,” said Darrell Henry, a lobbyist for the Western Business Roundtable and the Partnership for America, both of which are opposed to federal regulation of the environment.

Kassie Siegel, director of the climate, air, energy program at the Joshua, Calif.-based Center for Biological Diversity, countered: “It’s not a backdoor. It’s a front door, because the number one threat to polar bears is greenhouse gas emissions.”

On Friday, the U.S. Geological Society released a study noting that further loss of sea ice in the Arctic could mean a loss of two-thirds of the world’s polar bears within 50 years.

Interior Secretary Dirk Kempthorne, in announcing the polar bear review last year, said his department was not going to weigh in on the cause of the ice melt or what to do about it. But activists on both sides of the issue agree that position will be difficult, if not impossible, to maintain if the administration decides to protect the bear.

The analysis behind the proposed listing pointed to evidence that the buildup of heat-trapping gasses is likely accelerating the Arctic ice melt.

The question for observers is the extent to which the government can be compelled to act to contain the phenomenon.

“Once you make this leap, anything that happens that adds to global climate change could be subject to Fish and Wildlife Service approval,” Henry said. “So even expanding a highway in L.A. — because it would increase auto traffic, and therefore, auto emissions —could be forced before the service due to the listing of the polar bear.”

Environmental advocates said because the listing would take the endangered species law into uncharted territory, it is not clear how wide its impact would be.

“This exact situation has never been consulted before, so it’s an open question about what happens to proposals for major greenhouse gas emitters,” said Andrew Wetzler, director of the Endangered Species Project for the Natural Resources Defense Council. “But since the principal threat identified was climate change, and the recovery plan has to be concrete, theoretically, the plan is going to have to address climate change.”

After Interior announced the proposed listing late last year, it opened a 90-day comment period. Environmental groups ran print and television ads and rallied their grass roots, helping to generate more than 500,000 comments to the department— an outpouring Wetzler called “orders of magnitude greater” than for any previous species.

For environmental advocates, it hammered home the potency of the animal as a symbol for what they believe is the urgency of the climate crisis.

There are 19 polar bear populations in the Arctic, with the worldwide population standing between 20,000 and 25,000. The most closely watched population, in Canada’s western Hudson Bay, dropped 22 percent from 1987 to 2004 according to the Fish and Wildlife Service.

Environmental groups point to scientific evidence that that drop-off will become dramatically steeper toward the end of the century, as continued warming produces iceless Arctic summers.

Industry groups also have weighed in. The National Association of Manufacturers, the American Forest & Paper Association and the Alaska Oil & Gas Association, among others, all have lodged comments with Interior.

Beyond the potential economic impact of listing the polar bear, business groups contend the numbers behind the environmentalists’ claims of a shrinking polar bear population are just estimates. In fact, they say recent restrictions on hunting polar bears for sport have left their populations are at historic highs.

Since the comment period closed this spring, both sides have had little to do but watch and wait. So the degree to which industry has been monitoring the issue is difficult to determine.

At the beginning of the year, Peabody Energy, the largest coal producer in the world, hired the law and lobbying firm Crowell & Moring to represent them. The firm reported work on “climate change,” “alternative fuels,” and “Listing of the Polar Bears under the Endangered Species Act” on a lobbying disclosure report they filed in August.

But when contacted by Roll Call, a Peabody spokesman said the company was not lobbying either Interior or Congress on the issue and that listing the issue on the lobbying form had been a mistake.

Chet Thompson, a Crowell & Moring lobbyist working for Peabody, called the filing the result of an administrative mix-up. A few days later, the firm filed an amended lobbying report that dropped the mention of the polar bear listing.

Meanwhile, activists on both sides of the issue said they expect to ramp up publicity campaigns on the polar bear this winter as the Bush administration nears its decision.

The Partnership for America, a grass-roots group opposing the listing, in the spring named former House Resources Chairman Richard Pombo (R-Calif.) as its national chairman. And while a one-year lobbying ban on former lawmakers prevents Pombo from talking to his former colleagues about the subject until January 2008, Henry said the California Republican is well-versed on the issue and can serve as a national spokesman for business in the debate.