LAST December California approved a power line between San Diego and the Imperial Valley—a spot blessed with sun, wind and geothermal energy resources. The Sunrise Powerlink would twist around a state park, an Indian reservation and much of a forest (see map). Its builders would be banned from harming burrowing owls or rattlesnakes. It is just the sort of green infrastructure project that might be expected to delight environmentalists. Their response? An appeal and a petition to the state Supreme Court.

“Environmentalists have never been a well-mannered lot”, says Terry Tamminen, who has advised Arnold Schwarzenegger on climate change. But they seem to be becoming more ornery. A growing fear that the environment is on the brink of collapse is making many greens less willing to compromise, even with each other. And George Bush's departure from the White House has removed a common adversary.

The fiercest disputes are over electricity transmission. Many environmentalists, including Mr Schwarzenegger, argue that more power lines must be built to connect cities with potential sources of renewable energy. The governor strongly supports the Sunrise Powerlink project. The Sierra Club opposes it, along with another line that would run east from Los Angeles. Together with the Centre for Biological Diversity, the organisation is holding out for a guarantee that the line will be used to transmit electricity solely from renewable sources. Environmental groups in Nevada and the Midwest have issued similar ultimatums.

To an extent this is a dispute between pragmatism and idealism. Politicians like Mr Schwarzenegger tend to believe that energy projects should be judged on whether they improve on current practice. Activists, by contrast, prefer to measure them against an environmental ideal. “A little bit better than the status quo isn't good enough,” explains Bill Magavern, the Sierra Club's California director. He wants power to be generated close to those who will use it, and envisages a rash of solar roofs in San Diego.

A more profound difference has to do with how the problem is diagnosed. Although no big environmental group is unconcerned with global warming, they view the threat in different ways. The big divide is between those who fret about measurable changes in greenhouse-gas emissions and those who worry more about harm to natural habitats, whether caused by global warming or anything else. The first group—call them the environmental nerds—includes people like Al Gore and Mr Schwarzenegger. The second group—call them the tree-huggers—includes the Sierra Club, the Centre for Biological Diversity and other established conservation groups.

The dispute is likely to intensify in the next few months as Washington weighs in. This week Congress reached a deal on a stimulus plan that encourages the construction of yet more power lines. Barack Obama wants to create green jobs, but he needs to create jobs above all, and quickly. Environmentalists, who know how to hold up big projects better than anybody, will not be bounced so easily. A shame: after all, the greens are winning.