Pre-columbian soil erosion, persistent ecological changes, and collapse of a subsistence agricultural economy in the semi-arid Tehuacán Valley, Mexicoʹs ‘Cradle of Maize’

The cultivation of hillslopes in pre-Columbian times caused considerable soil erosion in the landscapes of the semi-arid Tehuacán Valley, south-central Mexico. A very severe episode of erosion of cultivated uplands occurred approximately 900 years ago in one drainage basin. The magnitude of soil erosion has left behind a degraded landscape with greatly decreased agricultural productivity and locally impoverished native flora. Hillslope soils in the basins studied are highly susceptible to erosion and neither pre-Columbian nor modern agricultural practices have proven to be sustainable in these upland environments. Severe soil loss that precedes agricultural collapse and land abandonment may impair the recovery of diverse and productive ecosystems for many hundreds to thousands of years, as this is the time required for the formation of a new, substantial soil mantle