In 2007, University of Nevada, Reno biologist Elizabeth Leger and a team of researchers set out to restore a commercial alfalfa field to a thriving community of desert plants. Their first step was to seed native perennial grasses, which would prevent weeds and wind erosion. But while their Nevada test site received only a few inches of rain each year, the most suitable grass seeds the team could find on the market were for varieties that had evolved in cooler, wetter climes—technically native plants, but collected from as far away as Montana and Canada. “That’s the only thing you can get,” Leger says. She and her colleagues bought the seeds, including grasses known to be drought-resistant, and hoped for the best. At first, the plants grew well—if the scientists used the former farm’s irrigation system. But within a couple years of shutting off the water as part of the restoration process—it was a desert ecosystem, after all—the grasses disappeared, leaving...