Mapeamento automático da expansão da agricultura anual no MATOPIBA entre 2002 e 2015 utilizando a plataforma Google Earth Engine
Over the past four decades, the Cerrado (Brazilian Savanna) has suffered a land use cover change process that transformed sparsely populated areas in major agricultural production centers. The region known as MATOPIBA, which is formed by the Brazilian state of Tocantins and some parts of the states of Maranhão, Piauí and Bahia, has 91% of its area in the biome Cerrado. It current represents the latest agricultural frontier in Brazil, an area of agriculture expansion and intensification, mainly focused in grains production. The agricultural activity has expanded quickly in MATOPIBA, but 72% of this native vegetation is still preserved. Because of the economic and environmental importance of this region, it is essential to monitor its agricultural areas. In this context, the main goal of this paper was to map the expansion of annual crops in MATOPIBA region, between July 2002 and June 2015 (thirteen crop years). A methodology based on NDVI/MODIS time series analysis and decision tree classifier was applied in order to map crop areas using the Google Earth Engine. The results shown the dynamics of crop areas in MATOPIBA and highlighted the rapid process of expansion between 2002 and 2015, reaching an expansion rate of 130% in this period. Using Google Earth Engine cloud computing platform it took about two hours to perform automatic crop mapping of thirteen crop years by the complete processing (gap filling, filtering/smoothing, feature extraction and classification) of 1196 NDVI/MODIS-250m images (tiles) covering the Cerrado portion of MATOPIBA region, which extends over 665.000 km2.