Interior Secretary Gale Norton (search) signed off on a plan Thursday for opening most of an 8.8 million-acre swath of Alaska's North Slope to oil and gas development. Some of the drilling could occur in areas important for migratory birds, whales and wildlife.

The Interior Department's Bureau of Land Management will use the plan to manage a northwest portion of the government's 23.5 million-acre National Petroleum Reserve-Alaska (search). Geologists believe the reserve may contain 6 billion to 13 billion barrels of oil.

It is located just west of the Arctic National Wildlife Refuge (search), where President Bush wants to open a 1.5 million-acre coastal plain to drilling as one of his top energy priorities. The Senate, in debating a massive energy bill, has rejected drilling there.

Environmentalists said the management plan threatens the health of Arctic tundra, ponds and lakes that are home to wildlife and migratory birds and provide a vital subsistence hunting and fishing ground for native Alaskans.

"It makes no sense to industrialize this incomparable wilderness area when there's only about six month's worth of economically recoverable oil ... and it would take at least 10 years to get it to market," said Charles Clusen, director of the Alaska lands project for the Natural Resources Defense Council (search), an environmental group.

The plan makes 7.23 million acres available for energy leasing, but will defer leasing the other 1.57 million acres for a decade to see if more environmental studies are needed, Interior Department officials said.

All energy leases will be subject to strict environmental standards, the officials said, while other provisions are meant to protect water quality, vegetation, wetlands, fish and wildlife habitats and subsistence uses.

The Interior Department proposed the management plan in January 2003. With few changes, the plan includes creation of a 102,000-acre Kasegaluk Lagoon Special Area (search) fenced off from leasing. It is considered particularly sensitive, as it is home to beluga whales, spotted seals and the black brandt, a migratory wild goose.

The plan designates special study areas of more than a half-million acres each for the Pacific black brandt and caribou. It also requires habitat studies for eiders, a bird whose existence is imperiled, and yellow-billed loons, and sets restrictions to minimize loss of foraging habitat for raptors around the Colville River Special Area (search).

Norton said oil and gas from the North Slope will help increase domestic energy production and stabilize prices in the long term.

"This plan will help produce energy in an environmentally responsible manner with the best available technology, while protecting the important biological, subsistence and cultural values found in this area," she said.

The reserve was set aside in the 1920s for potential energy development.

Environmentalists said the management plan rewards Bush administration friends in the oil and gas industry.

"This decision certainly gives big oil and gas plenty to be thankful for," said Eleanor Huffines, regional director in Alaska for The Wilderness Society.

BLM can now modify or waive environmental safeguards on a case-by-case basis for economic reasons, environmentalists said.

The bureau expects to hold a lease sale for oil and gas development on selected tracts next June. The Clinton administration had opened much of the eastern section of the reserve to oil and gas exploration in 1998, with tight restrictions and some areas fenced off.