A half-century of restoration efforts have bred the world's last 15 whooping cranes to create one, and only one, viable flock of 267 wild birds. But now, that progress may be reversed in the name of another environmental cause: renewable energy.

The wind whipping across the United States' Great Plains has been billed as the clean energy the nation needs to fight global warming. But for the whooping crane, those plains are irreplaceable habitat, and the turbines and power lines filling them are death traps.

Meanwhile, T. Boone Pickens, an oil magnate reborn as a green-energy activist, has purchased 667 turbines -- 2.5 for every wild whooping crane in the world -- to build a 1,000 megawatt wind farm in the Texas panhandle. Plans for wind farms entail the flyway the cranes travel during biannual migrations between the Gulf of Mexico and Canada's northwest.

"It's the scale of these projects that scares me," said Tom Stehn, the U.S. Fish and Wildlife Service's national whooping crane coordinator who has worked on restoration efforts for 26 years.