LOGGERS FELLING PRIMEVAL sequoias, oil barons raising derricks like so many middle fingers on the horizon, Japanese dolphin hunters engaged in horrific bloodsport—environmentalists have rarely had any trouble identifying the bad guy.

But as America embarks on a clean-energy moon shot, scaling up massive solar and wind projects, the black-and-white ethics that have guided greens since the days of Rachel Carson appear suddenly...quaint. There's a new and widening fault line within the movement itself. On one side: environmentalists seeking to stave off a climate holocaust by fast-tracking renewable-power development. On the other: environmentalists determined to protect important habitat and sacred landscapes, no matter what.

These conflicts, playing out in town halls, courtrooms, and the U.S. Senate, pit vast solar arrays against desert tortoises in California; towering wind turbines against sage grouse in the northern Rockies; and an offshore wind farm against Native American waters near Cape Cod. They've been billed in the media as a case of Green v. Green. Which is true. But this isn't some internecine spat among the Prius set.

The fact is, alternative energy is no longer alternative. It's big business, backed by giants like Bechtel and Goldman Sachs.

This is a good thing.

If the U.S. is going to break its dependence on coal and oil, we're going to need massive renewable-energy projects and all the capitalist spirit we can marshal. And, yes, we're going to have to do some building on sensitive landscapes. Leaders of most of the big environmental groups—the Sierra Club, the Natural Resources Defense Council, and the National Wildlife Federation—get this. They know that unchecked pollution and rising global temperatures will decimate the wild world, so they're willing to sacrifice some of the public lands that they would have fought tooth and nail to protect a generation ago. Not that it's easy.

"This challenges people. Hell, it challenges me!" says Carl Zichella, director of the Sierra Club's renewable-energy program for the West. "But we can't not do it."

Yet many conservationists, especially on the local level, aren't buying in. Having spent their lives fighting developers, they refuse to let any into their backyards now, even if they're wearing green hard hats. Instead, they're resorting to the same obstructionist tactics honed over decades of fighting polluters. A manifesto from a group calling themselves People Only Wanting Energy Responsibility (POWER!) declared: "Big Solar, wind farms, hydroelectric plants, along with the necessary transmission lines are nothing less than Domestic Terrorism being perpetrated on...our Desert Southwest's premier wildlands."