Sprawling crisis

The human pressure on natural ecosystems and protected areas is steadily increasing. Urban growth is undeniably and irreversibly converting natural habitats as it is constantly expanding with population growth. In this study we analyze the urban expansion of mega city Calcutta over four time-steps (1975, 1990, 2000, 2010) as an example of expansion over time and threat to the surrounding environment. Landsat and TerraSAR-X satellite data are selected to provide a long time-series. Various methods for information extraction, from multi-spectral optical techniques as well as radar data processing were developed to derive urban footprints semi-automatically. Urban growth rates per time-step (in hectares) were quantified, and spatial metrics were calculated to characterize the pattern of urban expansion by spatial configuration, direction and dimension. The results outline the increasing vulnerability of natural areas to the expansion of urban areas. The study showed that earth observation data, methods and products can significantly contribute to better