No Garden of Eden

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 lake revealed that erosion rates were at least as high before as after the Spaniards' arrival. In fact, erosion appears to have fallen off after the conquest. The conclusion: a return to traditional farming methods is no guarantee of a return to Eden.