A decade ago, the U.S. mandated the use of vegetable oil in biofuels, leading to industrial-scale deforestation — and a huge spike in carbon emissions.

The fields outside Kotawaringin village in Central Kalimantan, on the island of Borneo, looked as if they had just been cleared by armies. None of the old growth remained — only charred stumps poking up from murky, dark pools of water. In places, smoke still curled from land that days ago had been covered with lush jungle. Villagers had burned it all down, clearing the way for a lucrative crop whose cultivation now dominates the entire island: the oil-palm tree.

The dirt road was ruler straight, but deep holes and errant boulders tossed our tiny Toyota back and forth. Trucks coughed out black smoke, their beds brimming over with seven-ton loads of palm fruit rocking back and forth on tires as tall as people.