Exxon used to encourage motorists to "put a tiger in your tank." Well, soon polar bears could force drivers to shell out even more money for gasoline.

Environmental groups are pushing to list the polar bear as a threatened species under the Endangered Species Act, and the Bush administration is considering their demands.

It might make sense if the polar bear were endangered. But the worldwide population of these bears has more than doubled since 1965, to an estimated 20,000-25,000 today. By all accounts, the bears are thriving.

So what's behind the push to "save" the bears? A desire to ban energy exploration in much of Alaska.

Once a species is listed, its "critical habitat" is broadly defined to include vast areas. The government then drafts a "recovery plan" that often contains onerous restrictions on economic activity inside the habitat and, in some cases, even outside it, trumping property rights in the process. Plus, environmental groups can sue to force the Interior Department to include additional restrictions.

The first victim of a polar bear listing would be new oil and natural gas production throughout Alaska and in its surrounding waters. The listing would end any chances of opening up a small part of the Arctic National Wildlife Refuge, estimated to contain 10 billion barrels of oil -- enough to offset nearly 15 years worth of current imports from Saudi Arabia.

That's a problem, because Alaska is America's last best frontier for domestic oil and natural gas. Closing off these potential resources would jack up energy prices for decades to come and make us even more dependent on imports.

The fact that extensive oil drilling has been under way for decades in Prudhoe Bay and elsewhere in Alaska without harm to polar bears and other Arctic wildlife is something that should sway federal bureaucrats, but probably wouldn't.

It gets worse. The rationale for listing the polar bears as endangered is that carbon dioxide from fossil fuel use contributes to global warming and thus harms the bears. Having them listed as a threatened species could give the government authority to shut down new power plants, factories or just about any fossil energy-producing or energy-using entity in the U.S.

That scenario may seem far-fetched, but it's precisely the kind of sweeping controls environmental activists have long hoped to achieve through climate-change legislation. So far lawmakers -- wisely -- have been unwilling to pass laws banning carbon dioxide. Yet polar bear protections would give environmentalists a way to use courts to force a regulatory end-run around congressional and White House inaction.

Ironically, being listed might hurt polar bears. Alaska's economy depends on energy production; without it, the state's successful environmental programs, including those that have helped boost bear numbers, wouldn't be well funded.

If radical environmentalists want to push their agenda at the cost of ever-higher gasoline prices, they should at least do so honestly. Misusing the Endangered Species Act is wrong.

Ben Lieberman is a senior policy analyst in the Roe Institute for Economic Policy Studies at The Heritage Foundation.