Sécheresse, désertification et albédo des sols (Drought, desertisation and soils albedo)

摘要

Abstract. - In the land degradation of the Sahel, is it possible to precise the part of the causes resulting from natural changes of the climate (droughts for example) and the part resulting from human activities ? Even at the end of the twentieth century is'nt it imprudent to attribute the whole degradation to human actions ? The notions of radiatif balance, albedo and spectral reflectance are reviewed so as to understand the hypothesis proposed in the seventies of land degradation responsible in the increase of the albedo, itself cause of the upsetting of the climate equilibrium and of increased droughts. To have a better estimate of the degree of environmental degradation and the threshold of desertification (defined at a human tide span as irreversible land degradation) since the fifties, air photographies and later on satellite imagery are analysed.