"Species are blinking out," he says. "Habitat is going away. There's a really short period, maybe 20 to 30 years, to do some really big stuff, and then the opportunity is going to be gone. We're swinging for the fences here."

When it rains in central Montana, the dirt roads turn into what the locals call "gumbo," a slick clay-mud that often is impassable. It is, mercifully, drying out as Leah LaTray steers her pickup down a track snaked with deep ruts, clods of mud winging out from the wheels. LaTray's great-grandfather, Mose LaTreille, was a cowboy of French and Native American heritage who came with the cattle to northern Montana in the 1870s. LaTray, 47, wears a long black braid over her shoulder, silver hoop earrings, vest and kerchief, and square-toed cowboy boots. Her parents lost their ranch when she was a girl; she left Montana in the 1990s to study microbiology in Seattle and then to train horses in Texas. "It took me 20 years to come back," she says, "but I did," buying 250 acres that remained in her family's hands. LaTray makes her living running cattle on her partner's property now. "If you sell your land, you sell your future," she says.