In Pre-1492 Amazon, Farmers Managed Without Fires

The reason pre-Columbian farmers kept their savanna-dominated landscapes mostly fire-free, Iriarte said, was likely to prevent the loss of nitrogen and phosphorous form the soil and to keep the ground more fertile. Instead of burning, they opted for more labor-intensive practices to battle weeds and grow maize and other crops.

“They understood how to micromanage their environment for greater productivity,” said William Woods, an geographer at the University of Kansas in Lawrence, who added that agricultural burning now accounts for 30 percent of all the carbon released into the atmosphere around the world.