Back in August 1973, a biologist found a humble fish called the snail darter in the Little Tennessee River. At the time, it was believed that this species would be pushed to extinction if the Tennessee Valley Authority finished its Tellico Dam.

The snail darter became a celebrity, as environmentalists used the Endangered Species Act to halt the project. It took six years and an act of Congress to complete the dam.

The pattern is familiar. Someone discovers a rare species in a local area. It is declared endangered, and then local projects are blocked.

If things go the right way this month, the local nature of this issue might change. An endangered species could have an effect on economic activity everywhere in the U.S., not just in a single locale. U.S. District Judge Claudia Wilken recently ordered the Interior Department to decide by May 15 whether polar bears should be listed under provisions of the act. There is a strong chance that the polar bear will be declared “threatened.” If so, then everything about the economics of endangered species will be turned on its head.

Why is the polar bear in trouble? The main risk is that global warming will melt ice in the Arctic. Polar bears, biologists believe, need ice to live. Take away the ice, and no more polar bears.

If the polar bear is to be declared threatened, it must be because the Interior Department accepts the forecasts of continued global warming, and a significant reduction in Arctic ice.

There are two reasons why that decision, if it is made, will be momentous.

Geographic Reach
The first is the possible wide geographic reach of the global warming argument. The snail darter almost killed a single dam. The polar bear could, in theory at least, stop everything.

Suppose someone wants to build a coal-burning power plant in Florida. Environmentalists might challenge the construction because the plant will emit greenhouse gases leading to global warming and an increased threat to polar bears.

The second impact of this ruling is that it will likely end all Arctic exploration for oil and gas, at least in the U.S. Given surging world demand for oil, increased supply is the only thing standing between us and $200-a-barrel oil.

Costly Restrictions
These restrictions will have a large cost. “The U.S. Geological Survey and the Norwegian company StatoilHydro estimate that the Arctic holds as much as one-quarter of the world’s remaining undiscovered oil and gas deposits,” Scott Borgerson, an international affairs fellow at the Council on Foreign Relations, wrote in the March/April issue of Foreign Affairs.

Many biologists believe that global warming is a serious threat to the polar bear. If that leads to the polar bear being listed as threatened this week, then the world you live in will have fundamentally changed.