Under court order, the Bush administration this week listed polar bears as a threatened species. In doing so, however, the Interior Department took great pains to note that the listing would do nothing to stop climate change or prevent the melting of sea ice, the very problem that is imperiling the bears. Although the Endangered Species Act clearly is not the best way to tackle climate change, its requirements to protect animals at risk can’t be ignored.

In announcing his department’s action Wednesday, Interior Secretary Dirk Kempthorne said: “While the legal standards under the ESA compel me to list the polar bear as threatened, I want to make clear that this listing will not stop global climate change or prevent any sea ice from melting.”

He added: “Any real solution requires action by all major economies for it to be effective. That is why I am taking administration and regulatory action to make certain the ESA isn’t abused to make global warming policies.”

He’s right that combating climate change requires action by all major economies, but so far the biggest economy that is missing in action when it comes to negotiating and implementing both international and national policies to reduce greenhouse gas emissions is the United States.

Worse, the Bush administration has yet to find the right federal law to regulate greenhouse gas emissions, a major contributor to climate change. Last month, President Bush ruled out the Clean Air Act and the National Environmental Policy Act. He also said the courts were the wrong venue. He was responding to an April U.S. Supreme Court decision that the Environmental Protection Agency has the authority to regulate auto emissions as a way of reducing greenhouse gas emissions.

“Decisions with far-reaching impact should not be left to unelected regulators and judges,” the president said last month. “Such decisions should be debated openly and made by the elected representatives of the people they affect. The American people deserve an honest assessment of the costs, benefits and feasibility of any proposed solution.”

He’s absolutely right. But they also deserve an honest assessment of the costs, benefits and negative consequences of the Bush administration’s largely voluntary approach to reducing emissions.

The costs for polar bears are clear and immediate. Last year, Arctic sea ice, which polar bears use for hunting, dens and transit, fell to the lowest level ever recorded, 39 percent below the average from 1979 to 2000. Some climate models predict a virtual loss of sea ice by the end of the century.

The costs for the United States and the world are more dispersed, but also potentially severe, including increased drought and flooding leading to food shortages as well as increased insect infestations and disease. A 2006 British report warned that climate change will reduce global GDP by between 5 to 20 percent each year. Reducing greenhouse gas emissions to avoid the worst impacts of climate change, the report said, can be limited to around 1 percent of global GDP each year.

Whatever rules are used, mandatory steps to lessen climate change are needed now, for polar bears and humanity.