Land Management--Use It or Lose It

New research suggests that lack of upkeep was the primary cause of soil erosion in Mexico at the time of the European Conquest. Previous analyses have blamed the high indigenous population prior to European contact and the subsequent introduction of European domesticated animals, plants, and technology for the soil erosion leading to present-day degraded landscapes in Mexico. In an article published this week in PNAS, Christopher Fisher of Kent State University, Helen Pollard of Michigan State University and colleagues present archaeological and geological data offering new insight into the cause of large-scale erosion events within the Lake Patzcuaro Basin in Mexico over a 2000-year period. A recent drop in water level allowed researchers to analyze sediment and patterns of ancient settlement on and around the former lake bed. The researchers found that erosion was greatest during periods of low population density, whereas landscape stability was associated with periods of high population density. These results suggest that prior to the European Conquest of Mexico, native populations had developed land management practices, like terracing, that stabilized the landscape, but also made the landscape more susceptible to degradation. Thus, when European-introduced disease decimated native populations, the loss of labor dedicated to the management of human-engineered environments resulted in widespread land degradation. These findings not only challenge previous assumptions about the source of land degradation in this region, but also suggest that aspects of native land-use practices may be useful in modern conservation efforts.

"A reexamination of human-induced environmental change within the Lake Patzcuaro Basin, Michoacan, Mexico" by Christopher T. Fisher, Helen P. Pollard, Isabel Israde, Victor Garduno, and Subir K. Banerjee