University of California, Los Angeles, Pasadena, United States
Deforestation in tropical Africa is driven by a variety of socio-economic and environmental factors, and has resulted in land cover changes that threaten biodiversity, water and energy resources, and contributes to trace-gas emissions. Several conservation and development studies have concluded that the deforestation in Africa is closely tied to demographic conditions such that the greatest loss of rain forests has occurred in countries with higher population growth. However, lack of reliable data and survey information in some countries, has made the estimation of areas of intact forest and/or 2 under land use change and their relation to economic indicators surprisingly difficult to establish. Consequently, the extent and rate of deforestation in Africa are less well known than other regions of tropics. In this study, we use high resolution satellite imagery to map areas of forest clearing and general land cover types for the entire Central African tropical region. Images acquired by JERS-1 SAR (Synthetic Aperture Radar) instrument during its global rain forest mapping (GRFM) phase are the main source of data for this study. By using a combination of radar backscatter and texture analysis, and a SAR-specific classifier, we have developed a classifier to segment the JERS-1 images into five general categories of forest, nonforest, savanna, floodplain vegetation, and open water. Approximately 4000 high resolution (12.5 m) images for two periods of dry and wet seasons have been processed and delivered to the NASA/Jet Propulsion Laboratory and the European Commission Joint Research Center in Italy for generating a geocoded 100 m resolution mosaic of image data and a land cover map. The thematic interpretation of JERS-1 data and the validation of the land cover map are supported by available Landsat TM images acquired by NASA pathfinder project, ERS-1 mosaic of Africa generated by ESA TREES (Tropical Ecosystem Environment Monitoring by Satellites) project, and vegetation maps and field data provided by collaborators from national institutions in the region. JERS-1 100 m mosaic image and the derived land cover product will be integrated in the Landsat Pathfinder program in order to generate a complete forest cover map for the 1990s period.