Synopsis Desertification" is defined as land degradation in arid, semi-arid and dry sub-humid areas resulting from various and human activities. It is occuring in all regions of the world. More than 25% of the earth's land surface is threatened by desertification. Over 900 million people in more than 100 countries are at risk. Ninety of these countries are in the developing world. In the past, the problem was seen as strictly a regional one, primarily affecting the dryland areas in parts of Africa, Asia and Latin America. However, studies have shown that land degradation is becoming increasingly widespread. Fore example, a 1985 estimate by Environment Canada suggested that Canada was losing a billion dollar worth of agricultural production per year because of land degradation. The present volumes are based on multi disciplinary aspects of research into the practical problems of desert development and solutions of the management and use of arid lands and desertification. Everyone is concerned with arid land problems, including geographers, environmental scientists, climatologists and earth scientists. These volumes aim at an understanding of what is commonly called "desertification" a term which is proposed to be replaced by "land degradation". Each level of technology, excessive or insufficient, creates its own mismanagement.