Fires in protected areas reveal unforeseen costs of Colombian peace.

Armed conflict, and its end, can have powerful effects on natural resources, but the influence of war and peace on highly biodiverse tropical forests remains disputed. We found a sixfold increase in fires in protected areas across biodiversity hotspots following guerrilla demobilization in Colombia, and a 52% increase in the probability of per-pixel deforestation within parks for 2018. Peace requires urgent shifts to include real-time forest monitoring, expand programmes to pay for ecosystem services at the frontier, integrate demobilized armed groups as staff of protected areas, and establish a domestic market for frontier deforestation permits.