than 6,000 hectares of arable land turn The second half of the twentieth century will pass into history as an epoch that saw great irreversibly into desert (Tolba, 1992). During the last 30 years, human activity acceleration in technological development, the birth of electronics, the first space flights, and has created new deserts in Africa and Asia covering areas as large as Saudi Arabia. evolutionary developments in information sci­ ence, transportation and materials technol­ Intensive exploitation of the land has led to accelerated erosion of the best soils, and the ogies. Rapid industrial development spurred a significant increase in gross product on process is intensifying in parts of India, China, Russia, Ukraine and the United States. Without a global scale. Between 1950 and 1990 the global population doubled, but gross product urgent remedial action these trends could lead to complete impoverishment of these areas in increased fivefold and its value sevenfold (Brown, 1991). the decades ahead (Brown, 1984).