Stratégies de combat contre la dégradation de l'environnement dans les écosystèmes secs ; les réponses des Nations-Unies, de la C.E.I. ; de la Chine et du Sahel (Strategies to combat environmental degradation in dry ecosystems : answers of the United Nations, the Sahelians countries of Africa, the C.E.I., China and the Sahel)

摘要

Abstract. - Created by Aubreville in 1949 to describe the deterioration of the vegetation cover and the soil in the dry sub-humid ecosystem (Saharo-Sudanian), the word desertification was used for the first time on a worldwide scale by UNCOD (United Nations Conference on Desertification, Nairobi, 1977) and then defined as "The diminution or destruction of the biological potential of soils until the ultimate step of desert-like conditions". The conference "Environment and Development" programmed in Rio de Janeiro in August 1992 has asked UNEP to reassess the content of the word desertification. In 1990 the following definition was proposed : "Land degradation in arid, semi-arid and dry sub-humid areas resulting from adverse human impact. LAND : in this concept includes soil and local resources, land surface and vegetation or crops. DEGRADATION : implies reduction of resource potential by one or a combination of processes acting on the land. " Desertification can be defined as "Irreversible degradation of the environment in the dry ecosystems : arid, semi-arid, dry sub-humid". Resulting from the combination of human overuse, in vulnerable ecosystems and adverse climatic conditions, desertification became a complex problem simultaneously socio-economical and environmental. How Africa in its Sahelian and Sahelo-Sudanian ecosystems, the C.E. I. in the Aral Sea basin and China in its dry ecosystems have adopted different strategies for the desertification control will be analysed.