At first light, workers hefting huge Stihl chain saws roar into action, cutting down trees that may be 1,200 years old. Red macaws and brilliant-feathered toucans take off, heading deeper into the rainforest. The chain saw crews also set fires, making way for more pits.

This gaping cavity is one of thousands being gouged today in the state of Madre de Dios at the base of the Andes—a region that is among the most biodiverse and, until recently, pristine environments in the world. All told, the Amazon River basin holds perhaps a quarter of the world’s terrestrial species; its trees are the engine of perhaps 15 percent of photosynthesis occurring on landmasses; and countless species, including plants and insects, have yet to be identified.