Víctor López stands amid brown, lifeless-looking young palm trees, the ground at his feet still charred from a fire that swept through 10 hectares (25 acres) of plantation four days earlier. The fire, set by mistake when a neighbor lit a match to destroy a wasp nest, raced out of control. Farmers with backpack water tanks and shovels kept the flames out of a stand of mature oil palms. But while the young trees will recover—some are already sprouting green shoots again—the fire set back palm oil production in this western Amazon community by at least three years. “People set fires and say it’s an accident,” says López, who heads a local association of small-scale oil-palm producers. “It’s not an accident. It’s caused by man.”

In the western Amazon Basin, drought and deforestation have triggered two “once-in-a-century” fire seasons in the past six years, upending the notion the rainforest would not burn. Scientists are scrambling to understand how fire is related to human migration, land-use change, biodiversity loss and climate.

Fire conference