Large-scale conversion of tropical forests into pastures or annual crops will likely lead to changes in the local microclimate of those regions. Larger diumal fluctuations of surface tempera- ture and humidity deficit, increased surface runoff during rainy periods and decreased runoffduring the dry season, and decrea- sed soil moisture are to be expected. lt is likely that evapotranspiration will be reduced because of less available radiative energy at the canopy leveI since grass presents a higher albedo than forests, and also due to reduced availability of soil moisture at the rooting zone primarily during the dry season. Coupled numerical models of the global atmosphere and biosphere have been used recently to assess the effects of Amazonia deforestation on .the regional and global climate. The results of these General Circulation Model (GCM) simulations show that, if the tropical forests were replaced by degraded grass (pasture) in the model, there was a significant increase in surface temperature and a decrease in evapotranspiration, precipitation and runoff. There was also an increase in the length of the dry season which can have serious implications for the reestablishment of the tropical forests in the cleared areas.Pages: 199-21
