EFEITOS DA EXPANS?O URBANA NA CONSERVA??O DE FLORESTAS EM UMA áREA DE MANANCIAL METROPOLITANO

摘要

The clearing of native vegetation in water source areas and its effects on water supply availability have become a major concern in large metropolises. This study examined the spatial and temporal changes in land use and cover and their effects on the conservation of Atlantic Forest in a water source area in the Metropolitan Region of S?o Paulo that is the second most densely populated territory in Brazil, the municipality of Diadema. Historical maps and trend scenarios were developed by applying the Markov chain in association with cellular automata. Forest conservation was assessed based on a set of landscape metrics of resource availability, fragment isolation, and trends of forest fragmentation. Our findings revealed an increase in urban growth of 37% in the last five decades directly associated to the clearing of 50% of forests in intermediate/advanced stages and 40% in early stages. The main drivers of landscape change were human-modified fields (41%) and net roads (54%). Optimal resource availability was drastically reduced (75%) while isolation increased (361.5%) among existing forest fragments. Therefore, future trends indicate that, without changes in the management of the area, deforestation may occur rapidly and continuously until 10% of forest remains, leading to potential adverse effects on water availability and quality of the Billings Reservoir and the local biodiversity.