Stu Weiss and I are strolling at Edgewood Park and Preserve, a bucolic swath of greenery just south of San Francisco in San Mateo County, California. Here, Weiss and his fellow scientists from the Creekside Center for Earth Observation aid and abet the citizenry in helping to resuscitate populations of the Bay Checkerspot Butterfly and the San Mateo Thornmint, both endangered species. Weiss’s team has laid out a transect in which they are counting up thornmint stalks. Thei