WHEN SPANISH CONQUISTADORES ARRIVED IN MEXIco in the 16th century, they found a veritable Eden and quickly despoiled it. The Spaniards' introduction of the plow accelerated soil erosion; in contrast, indigenous farmers' low-tech methods kept the land in pristine shape. Or so environmentalists, who are urging a return to traditional farming techniques in many areas of the world, like to think.
A new report in Nature suggests that such thinking is a myth. British scientists studied the pattern of soil erosion in the Patzcuaro basin, an area of southwestern Mexico that was a center of pre-Hispanic civilization. Sediment samples from the...