Characterizing patterns of global land use: An analysis of global croplands data

Human activities have shaped significantly the state of terrestrial ecosyst ems throughout the world. One of the most direct manifestations of human ac tivity within the biosphere has been the conversion of natural ecosystems t o croplands. In this study, we present an analysis of the geographic distri bution and spatial extent of permanent croplands. This analysis represents the area in permanent croplands during the early 1990s for each grid cell o n a global 5 min (similar to 10 km) resolution latitude-longitude grid. To create this data set, we have combined a satellite-derived land cover data set with a variety of national and subnational agricultural inventory data. A simple calibration algorithm was used so that the spatial land cover dat a were generally consistent with nonspatial agricultural inventory data. Th e spatial distribution of croplands represented in this analysis presents a quantitative depiction of global agricultural geography. The regions of th e world known to have intense cultivation (e.g., the North American corn be lt, the European wheat-corn belt, the Ganges floodplain, and eastern China) are clearly portrayed in this analysis. It also captures the less intensel y cultivated regions of the world, usually surrounding the regions mentione d above, and regions characterized by subsistence agriculture (e.g., Saheli an Africa). Data generated from this kind of analysis can be used within gl obal climate models and global ecosystem models to assess the importance of permanent croplands on environmental processes. In particular, these data, combined with models, could help evaluate the role of changing land cover on regional climate and carbon cycling. Future efforts will need to concent rate on other land use systems, including pastures and regions of shifting cultivation. Furthermore, land use and land cover data must be extended to include an historical dimension so as to evaluate the changing state of the biosphere over time.