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…