Simulation of Carbon and Water Cycles in a Brazilian Watershed: The Impact of Land-Use Change

Expansion of agriculture on new lands is recognized as one of the most significant human alterations to the global environment. Although food and fiber production are essential ecosystem services (ES) to humankind, the land use change process implicates in the adoption of intensive agricultural practices directly related to the depletion of a wide range of ES at local, regional and global scales. Considering the importance of issues such as climate change, freshwater scarcity, groundwater depletion, soil erosion, etc., this paper aims to simulate the impact of land-use change on the ecosystem services related to water and carbon biogeochemical cycles. The system under study is the Taquarizinho river basin, located at the eastern region of Mato Grosso do Sul state, Brazil. Formerly occupied by Brazilian savannah (Cerrado), more than half of its total area was converted both to agriculture and pasture land since the 1960’s. In order to quantify the impact of land-use change on ES provided by Taquarizinho basin over the years, we built a model which dynamically represents run-off, canal discharge, aquifer recharge, evapotranspiration, carbon sequestration, carbon emission, and net carbon exchange in the river basin. We run the model considering the same daily emergy input however shifting land use scenarios (pristine conditions, recent land use, 100% Cerrado, 100% agriculture and 100% pasture) in order to estimate the impact of land-use change on the local ecosystem services over the time. The model outputs consider the dynamics of carbon and water flows in terms of mass (kg C or m 3 of water), emergy (seJ) and Emdollars (EM$), on a daily basis.