Impact of urban sprawl on net primary productivity in the Southeastern United States

The Southeastern United States has undergone one of the highest rates of landscape changes in the country, as a result of changing demographics and land use practices over the last few decades. Here, we propose a remote sensing based methodology to estimate regional impacts of land development on ecosystem resources. As an indicator of ecosystem functioning we chose net primary productivity (NPP), which is routinely estimated from the MODerate resolution Imaging Spectroradiometer (MODIS) data. We combined a potential natural vegetation map, a current LANDSAT-based land cover map, nighttime data derived from the Defense Meteorological Satellite Program´s Operational Linescan System (DMSP/OLS) combined in a geographic information system. We compared the effects of historical and recent land cover changes on NPP. The analysis indicates that 80% of the original land cover of the region has undergone changes that resulted in an annual reduction in NPP of 9%. In 1992, urban areas amounted to only 4% of the total surface in the region, but they appear to be responsible for most of the landscape fragmentation. Estimates based on nightlights data between 1992-93 and 2000 showed developed area increased by another 0.5%, contributing to a further reduction in annual NPP. The combination of MODIS products like NPP with nighttime data could provide rapid assessment of land cover changes and their impacts on regional ecosystem resources.