Some 60 to 70 percent of the marijuana consumed in the United States comes from California—and a lot of it is grown outdoors in the so-called “Emerald Triangle” region north of San Francisco. Jennifer Carah, an ecologist at The Nature Conservancy, says illegal pot farms in the region are repeating many of the environmental sins of the logging era, like clear-cutting and road building, which contribute to erosion that chokes streams and rivers. The growers also pump streams dry and widely apply pesticides and herbicides, which Carah and her colleagues say is contributing to the decline of already rare species like Pacific fishers (Pekania pennanti) and coho salmon (Oncorhynchus kisutch).