From his Cessna a mile above the southern Amazon, John Carter looks down on the destruction of the world's greatest ecological jewel. He watches men converting rain forest into cattle pastures and soybean fields with bulldozers and chains. He sees fires wiping out such gigantic swaths of jungle that scientists now debate the "savannization" of the Amazon. Brazil just announced that deforestation is on track to double this year; Carter, a Texas cowboy with all the subtlety of a chainsaw, says it's going to get worse fast. "It gives me goose bumps," says Carter, who founded a nonprofit to promote sustainable ranching on the Amazon frontier. "It's like witnessing a rape." ....

"You can't protect it. There's too much money to be made tearing it down," he says. "Out here on the frontier, you really see the market at work."

This land rush is being accelerated by an unlikely source: biofuels. An explosion in demand for farm-grown fuels has raised global crop prices to record highs, which is spurring a dramatic expansion of Brazilian agriculture, which is invading the Amazon at an increasingly alarming rate.

Propelled by mounting anxieties over soaring oil costs and climate change, biofuels have become the vanguard of the green-tech revolution, the trendy way for politicians and corporations to show they're serious about finding alternative sources of energy and in the process slowing global warming. The U.S. quintupled its production of ethanol--ethyl alcohol, a fuel distilled from plant matter--in the past decade, and Washington has just mandated another fivefold increase in renewable fuels over the next decade.