Perched on a rocky coastal cliff in central California, surrounded by rolling hills and a nature reserve, the Diablo Canyon nuclear power plant has been a lightning rod for controversy for decades.  In the 1970s, the site attracted protests from tens of thousands of hippies, whose rallies against nuclear power often included impromptu musical performances from the likes of Crosby, Stills & Nash. “That was a huge time,” recalls resident Rochelle Becker, who participated in the protests and later founded an anti-nuclear group. “I was one of the people who didn’t get arrested. There were a lot of my friends who did.” She helped on the legal team for protesters who were detained, and even brought a guitar into jail for the singerJackson Browne in 1981. The plant began operations four years later.

Now, the nuclear-free vision that Ms Becker and so many others fought for is being realised: Diablo Canyon, the last nuclear plant in California, is to be shut down. In June, Pacific Gas & Electric, the utility that owns the plant, said it would close within a decade and that most of the power it supplies replaced by renewable energy.  Yet there are doubts that closing the reactor will be a victory for the environment. Diablo Canyon is one of California’s largest sources of electricity generated without significant carbon dioxide emissions, providing 9 per cent of the state’s power. At a time when almost 200 countries have committed to action on global warming, giving up that capacity looks to many like a serious mistake. Other countries that have tried to go nuclear-free, most recently Germany, have faced increased fossil fuel use and rising emissions.