“Everything had gotten worse,” Kingsnorth said. “You look at every trend that environmentalists like me have been trying to stop for 50 years, and every single thing had gotten worse. And I thought: I can’t do this anymore. I can’t sit here saying: ‘Yes, comrades, we must act! We only need one more push, and we’ll save the world!’ I don’t believe it. I don’t believe it! So what do I do?”

The first thing that Kingsnorth did was draft a manifesto. Also called “Uncivilization,” it was an intense, brooding document that vilified progress. “There is a fall coming,” it announced. “After a quarter-century of complacency, in which we were invited to believe in bubbles that would never burst, prices that would never fall . . . Hubris has been introduced to Nemesis.”

The initial print run of “Uncivilization” was only 500 copies. Yet the manifesto gained widespread attention. The philosopher John Gray reviewed it in The New Statesman. Professors included it on their reading lists. An events space in Wales invited Kingsnorth and Dougald Hine, Dark Mountain’s co-founder, to put on a festival; 400 people showed up. Doug Tompkins, the billionaire who started the outdoor-apparel company the North Face, and his wife, Kristine Tompkins, the former C.E.O. of Patagonia, offered financing and invited Kingsnorth and his family to spend two months on land they own in southern Chile.

There were others, however, who saw Kingsnorth’s new work as a betrayal. With waters rising, deserts spreading and resource wars looming, how could his message be anything but reckless — even callous? He and his sympathizers were branded “doomers,” “nihilists” and (Kingsnorth’s favorite epithet) “crazy collapsitarians.” One critic, a sustainability advocate, published an essay in The Ecologist — a magazine Kingsnorth once helped run — comparing Dark Mountaineers to the complacent characters in the Douglas Adams novel “The Restaurant at the End of the Universe”: “Diners [who] enjoyed watching the obliteration of life, the universe and everything whilst enjoying a nice steak.”

Kingsnorth regards such charges with equanimity, countering that the only hope he has abandoned is false hope. The great value of Dark Mountain, he has claimed, is that it gives people license to do the same. “Whenever I hear the word ‘hope’ these days, I reach for my whiskey bottle,” he told an interviewer in 2012. “It seems to me to be such a futile thing. What does it mean? What are we hoping for? And why are we reduced to something so desperate? Surely we only hope when we are powerless?”

Instead of trying to “save the earth,” Kingsnorth says, people should start talking about what is actually possible. Kingsnorth has admitted to an ex-activist’s cynicism about politics as well as to a worrying ambivalence about whether he even wants civilization, as it now operates, to prevail. But he insists that he isn’t opposed to political action, mass or otherwise, and that his indignations about environmental decline and industrial capitalism are, if anything, stronger than ever. Still, much of his recent writing has been devoted to fulminating against how environmentalism, in its crisis phase, draws adherents. Movements like Bill McKibben’s 350.org, for instance, might engage people, Kingsnorth told me, but they have no chance of stopping climate change. “I just wish there was a way to be more honest about that,” he went on, “because actually what McKibben’s doing, and what all these movements are doing, is selling people a false premise. They’re saying, ‘If we take these actions, we will be able to achieve this goal.’ And if you can’t, and you know that, then you’re lying to people. And those people . . . they’re going to feel despair.”

Whatever the merits of this diagnosis (“Look, I’m no Pollyanna,” McKibben says. “I wrote the original book about the climate for a general audience, and it carried the cheerful title ‘The End of Nature’ ”), it has proved influential. The author and activist Naomi Klein, who has known Kingsnorth for many years, says Dark Mountain has given people a forum in which to be honest about their sense of dread and loss. “Faced with ecological collapse, which is not a foregone result, but obviously a possible one, there has to be a space in which we can grieve,” Klein told me. “And then we can actually change.”