Impacts of Land-Use and Land-Cover Change over South America: a modeling study

Abstract:

Changes in patterns of land use and land cover have great influence on hydrology, climate and biogeochemical cycles. In this work the influences caused by changes in patterns of land cover and land use in Brazil on the behavior of the water balance over South America were evaluated. To fulfill this objective numerical experiments were carried out with the regional model ETA for the period between 1979 and 2008, in which three different conditions of land use and land cover in Brazil was used: 1) Potential Experiment, which are not included the anthropogenic changes in vegetation cover; 2) Control Experiment, in which the map of land use and land cover used the conditions of the 90s; 3) New Experiment, which represents the current conditions of land use and land cover. The results show clearly that the constant changes in patterns of land cover and land use in Brazil cause an increase in precipitation and moisture convergence, and reduced evapotranspiration over the Amazon Region. In other words, it can be stated that with the advance of changes in patterns of land use and land cover, Amazon further intensified their behavior as a sink of moisture, mainly due to increased precipitation and significant reduction in evapotranspiration, noting also that reduction of moisture available in the atmosphere was not offset by increased moisture convergence. The results on the La Plata Basin shows that initially (CONTROL) there is an increase in precipitation and evapotranspiration over the region and reduction in moisture convergence, which is later (NEW) modified to a pattern of reduction in precipitation and evapotranspiration followed by an increase in moisture convergence. These changes in the patterns of land use and land cover of the 90s make the area potentially source of moisture to the atmosphere, even with the reduction in moisture convergence, but reversing their behavior to sink moisture by inserting current vegetation cover modifications, mainly due to reduced precipitation and evapotranspiration over the basin. Thus, we can conclude that the constant changes in the land use and land cover in Brazil have direct influence on the continent water balance, influencing directly the availability of moisture to the atmosphere and moisture transport between the tropics and extratropics.