As guerrilla warfare subsides in Colombia's rural areas, biologists and other researchers who were driven out by the violence are now returning to do fieldwork. They have made a surge of discoveries, describing new species of frogs, birds, and even monkeys. But scientists aren't the only ones racing back. Gold miners, oil companies, and cattle ranchers—also excluded by the conflict—are taking advantage of the peace. Researchers are concerned about a new and unprecedented threat to biodiversity.