Simulation of the regional climatic impact of Amazon deforestation

Abstract

THE Amazon basin contains about half of Earth's Tropical forest1. Population pressure and subsequent demands for crop production, timber and firewood have led to rapid deforestation. Quantitative estimates of the rate of deforestation from analysis of Landsat observations indicate that rates are increasing exponentially in many regions2,3, but the precise figures are not known4. Removal of the protection provided by natural cover can lead to soil erosion, disturbance of the ecosystem and reduction in species diversity5. Here we report results from a three-year simulation, using a general circulation model, in which we replace Amazon tropical forest and savannah with pasture. The simulated local climate response was dominated by a weakened hydrological cycle, with less precipitation and evaporation and an increase in surface temperature. The reductions in precipitation and evaporation were mostly caused by changes in surface roughness and albedo: decreased roughness dominated the reduction in evaporation (and the increase in temperature), whereas the increased albedo was the main cause of a decrease in the moisture flux convergence (measured as the difference between precipitation and evaporation) contributing to the decrease in precipitation.