Indigenous groups in the Brazilian Amazon are locked in a battle to protect their forest from land grabbers, illegal loggers, and a political class determined to open the rainforest to agriculture and mining. It’s a bloody conflict with global stakes. Scientists warn that rising deforestation has pushed the world’s largest remaining tropical forest dangerously close to a tipping point that, once crossed, would send global warming into hyperdrive. The forest is flipping from a powerful “carbon sink” to a net source of carbon in the atmosphere. The property and legal rights of indigenous peoples that have been invoked to reverse that trend are conflicting with incentives to clear land and grow food for the global market.