Before the environmental activist and gay rights lawyer David Buckel set himself afire in Prospect Park in Brooklyn on April 14, he wrote a letter explaining that he had chosen his “early death by fossil fuel” as an act of protest against the environmental catastrophe that we are bringing upon ourselves and the planet. It was a horrifying end, not least because in life Mr. Buckel had successfully taken on issues as seemingly intractable as the legalization of same-sex marriage. If someone so capable had given up on the environment, one woman remarked to a Times reporter, “What does that mean for the rest of us?”

I was thinking about Mr. Buckel and about despair a few nights later, over a drink with Joe Walston of the Wildlife Conservation Society. As director of that organization’s worldwide field conservation work, Mr. Walston routinely comes face-to-face with the dark forces of human overpopulation, mass extinction of species, climate change and pollution. But he is also the co-author of a paper being published this week in the journal BioScience that begins with the uplifting words of Winston Churchill to the British nation in June 1940, under the shadow of the Nazi conquest of France: “In casting up this dread balance sheet and contemplating our dangers with a disillusioned eye,” Churchill declared, “I see great reason for intense vigilance and exertion, but none whatever for panic or despair.”

Mr. Walston and his co-authors go on to argue against the increasingly common view that these are the end times for life as we know it. Instead, they suggest that what the natural world is experiencing is a bottleneck — long, painful, undoubtedly frightening and likely to get worse in the short term — but with the forces of an eventual breakthrough and environmental recovery already gathering strength around us.

Mr. Walston sipped his beer and listed what he called “the four pillars” of conservation in the modern era — a stabilized human population, increasingly concentrated in urban areas, able to escape extreme poverty, and with a shared understanding of nature and the environment — “and all four are happening right now.” He singled out the trend toward urbanization as the biggest driver of environmental progress, bigger perhaps than all the conservation efforts undertaken by governments and environmental groups alike.