When Dan O’Brien began ranching buffalo on the South Dakota prairie two decades ago, his mind wasn't entirely on the buffalo.

A wildlife biologist and author who’d spent most of his career helping restore populations of the once-endangered peregrine falcon, O’Brien got into the bison business because he wanted to save more birds.

“What I’d learned is it’s not about a single species. It’s about species diversity—flora and fauna,” he says. “And in the Great Plains, what’s the species that ties it all together? It’s the buffalo. I started raising buffalo to see if we could improve ground-nesting bird populations. Then one thing led to another.”

Similarly, when Yvon Chouinard launched the outdoor clothing company, Patagonia, in the 1970s, he didn’t envision