Both northern and southern Saharan margins show obvious signs of environmental and socioeconomic crisis in the second half of the XXth century. This situation is generally indifferently designed as desertification. Nevertheless, several sites studied in these Saharan northern and southern margins, in particular wetlands (Aleg and Mâl lakes in Mauritania, River Senegal low delta between Mauritania and Senegal, oued Dadès basin in Morocco and Saharan Atlas southern Piedmont in Algeria), show modalities and rhythms of degradation process development, and local population adaptation strategies to these crises, which come to qualify these conclusions often as catastrophism. Ground survey, remote sensing and geographical information systems show that if the population has exacerbated the impact of the 1970-1980 droughts which affected all these regions, degradation processes observed, their magnitude and perennial, are linked to a disorganization of the environment management beyond which supervision has been lost by the local traditional institutions. People knew how to bring adequate answers to these ecological crises there where the social institutions in charge of resources and land management were still enough long-lived and powerful.