An appeals court will decide whether federal regulators conducted adequate environmental studies before selling $2.7 billion in petroleum leases off Alaska's northwest coast.

Alaska Native and environmental groups on Thursday challenged a U.S. District Court decision that concluded the Bureau of Ocean Energy Management had adequately considered the environmental effects of a 2008 sale in the Chukchi Sea, home to one of two populations of polar bears in the United States, plus walrus, ice seals and endangered whales.

"This Bush-era lease sale in one of the most fragile and least understood ecosystems in the world was never a good idea," said Rebecca Noblin, Alaska director for the Center for Biological Diversity, in the announcement of the appeal.

"Four years later, all we've learned about the Chukchi Sea is how little we know," she said. "It's time the Obama administration took the blinders off and admitted that neither it nor the industry is prepared for the risks of drilling for oil in the Arctic Ocean."

Bureau of Ocean Energy Management spokeswoman Theresa Eisenman said from Washington, D.C., that the agency does not comment on pending litigation.

A subsidiary of Royal Dutch Shell was the leading bidder in the 2008 lease sale, spending $2.1 billion. The company hopes to drill its first exploratory wells on the Chukchi leases this summer, along with leases it obtained in a previous sale in the Beaufort Sea.