Al Gore has been hectoring Americans to pare back their lifestyles to fight global warming. But if Mr. Gore wants us to rethink our priorities in the face of this mother of all environmental threats, surely he has convinced his fellow greens to rethink theirs, right?

Wrong. If their opposition to the Klamath hydroelectric dams in the Pacific Northwest is any indication, the greens, it appears, are just as unwilling to sacrifice their pet causes as a Texas rancher is to sacrifice his pickup truck. If anything, the radicalization of the environmental movement is the bigger obstacle to addressing global warming than the allegedly gluttonous American way of life.

But tearing down the Klamath dams, the last of which was completed in 1962, will do more harm than good at this stage. These dams provide cheap, renewable energy to 70,000 homes in Oregon and California. Replacing this energy with natural gas--the cleanest fossil-fuel source--would still pump 473,000 tons of additional carbon dioxide into the atmosphere every year. This is roughly equal to the annual emissions of 102,000 cars.

Given this alternative, one would think that environmentalists would form a human shield around the dams to protect them. Instead, they have been fighting tooth-and-nail to tear them down because the dams stand in the way of migrating salmon. Environmentalists don't even let many states, including California, count hydro as renewable.

They have rejected all attempts by PacifiCorp, the company that owns the dams, to take mitigation steps such as installing $350 million fish ladders to create a salmon pathway. Klamath Riverkeeper, a group that is part of an environmental alliance headed by Robert Kennedy Jr., has sued a fish hatchery that the California Department of Fish and Wildlife runs--and PacifiCorp is required to fund--on grounds that it releases too many algae and toxic discharges. The hatchery produces at least 25% of the chinook salmon catch every year. Closing it will cause fish populations to drop further, making the demolition of the dams even more likely.

But the end of the Klamath won't mean the end of the dam saga--it is the big prize that environmentalists are coveting to take their antidam crusade to the next level. "This would represent the largest and most ambitious dam removal project in the country, if not the world," exults Steve Rothert of American Rivers. The other dams on the hit list include the O'Shaughnessy Dam in Yosemite's Hetch Hetchy Valley that services San Francisco, Elwha River dam in Washington and the Matilija Dam in Southern California.

Large hydro dams supply about 20% of California's power (and 10% of America's). If they are destroyed, California won't just have to find some other way to fulfill its energy needs. It will have to do so while reducing its carbon footprint to meet the ambitious CO2 emission-reduction targets that Gov. Arnold Schwarzenegger has set. Mr. Schwarzenegger has committed the Golden State to cutting greenhouse gas emissions 80% below 1990 levels by 2050--a more stringent requirement than even in the Kyoto Protocol.

Bruce Hamilton, Sierra Club's deputy executive director and a longtime proponent of such a mandate, refuses to even acknowledge that there is any conflict in closing hydro dams while fighting global warming. All California needs to do to square these twin objectives, he maintains, is become more energy efficient while embracing alternative fuels. "We don't need to accept a Faustian bargain with hydropower to cut emissions," he says.

This is easier done in the fantasy world of greens than in the real world. If cost-effective technologies to boost energy efficiency actually existed, industry would adopt them automatically, global warming or not.

As for alternative fuels, they are still far from economically viable. Gilbert Metcalf, an economist at Tufts University, has calculated that wind energy costs 6.64 cents per kWh and biomass 5.95 kWh--compared to 4.37 cents for clean coal. Robert Bradley Jr., president of the Institute for Energy Research, puts these costs even higher. "Although technological advances have lowered alternative fuel prices in recent years, these fuels still by and large cost twice as much as conventional fossil fuels," he says.

But suppose these differentials disappeared. Would the Sierra Club and its eco-warriors actually embrace the fuels that Mr. Hamilton advocates? Not if their track record is any indication. Indeed, environmental groups have a history of opposing just about every energy source.

Their opposition to nuclear energy is well known. Wind power? Two years ago the Center for Biological Diversity sued California's Altamont Pass Wind Farm for obstructing and shredding migrating birds. ("Cuisinarts of the sky" is what many greens call wind farms.) Solar? Worldwatch Institute's Christopher Flavin has been decidedly lukewarm about solar farms because they involve placing acres of mirrors in pristine desert habitat. The Sierra Club and Wilderness Society once testified before Congress to keep California's Mojave Desert--one of the prime solar sites in the country--off limits to all development. Geothermal energy? They are unlikely to get enviro blessings, because some of the best sites are located on protected federal lands.

Greens, it seems, always manage to find a problem for every environmental solution--and there is deep reason for this.

With the arrival on the scene of Deep Ecologists from Europe in the 1980s, Muir's mystical preservationist side won the moral high ground. The emphasis of Deep Ecology on radical species equality made talk about solving environmental problems for human ends illicit within the American environmental community. Instead, Arne Naess, the revered founder of Deep Ecology, explicitly identified human beings as the big environmental problem. "The flourishing of nonhuman life requires a decrease in human population," his eight-point platform to save Mother Earth serenely declared.

This ideological turn, notes Ramachandra Guha, a left-leaning Indian commentator and incisive critic of Deep Ecology, has made American environmentalism irrelevant at best and dangerous at worst for the Third World, where addressing environmental issues such as soil erosion, water pollution and deforestation still remains squarely about serving human needs. By turning wilderness preservation into a moral absolute--as opposed to simply another form of land use--Deep Ecology has justified wresting crucial resources out of the hands of India's agrarian and tribal populations. "Specious nonsense about equal rights of all species cannot hide the plain fact that green imperialists . . . are dangerous," Mr. Guha has written.

Besides hurting the Third World, such radicalism had made the environmental movement incapable of responding to its own self-proclaimed challenges. Since nature can't speak for itself, the admonition to protect nature for nature's sake offers not a guide to action, but an invitation to inaction. That's because a non-anthropocentric view that treats nature as non-hierarchical collapses into incoherence when it becomes necessary to calculate trade-offs or set priorities between competing environmental goals.

Thus, even in the face of a supposedly calamitous threat like global warming, environmentalists can't bring themselves to embrace any sacrifice--of salmons or birds or desert or protected wilderness. Its strategy comes down to pure obstructionism--on full display in the Klamath dam controversy.

Yet, if environmentalists themselves are unwilling to give up anything for global warming, how can they expect sacrifices from others? If Al Gore wants to do something, he should first move out of his 6,000 square-foot Nashville mansion and then make a movie titled: "Damn the salmon."