干旱区生态环境知识资源中心

Economic activities in the arid steppes of Algeria are largely based on sheep husbandry using rangelands. The recent "regreening" observed in the arid and semi-arid rangelands surrounding the Sahara desert is challenging the desertification caused by the increasing grazing pressure. To the question about the reality of desertification, this work tries to answer by a diachronic and landscape approach. We compared the land cover map carried out in 2014 to the other two maps performed in 1978 and 2006. The remotely sensed changes in the landscape units show a fragmentation in the preexisting steppe landscapes with various degradation stages. Steppes of Stipa tenacissima lost 94 % of their area since 1978; those of Lygeum spartum after increasing by 4 % from 1978 to 2006, decreased by 13 % from 2006 to 2014. The L. spartum steppe had disappeared from its original places (80 % of cases) but encroached on new lands mainly at the expense of S. tenacissima (60 % of the current surface). Currently, two types of steppes dominate 80 % of the total rangelands; those of L. spartum with 35 % and of Atractylis serratuloides with 33 %. The spreading A. serratuloides steppe over 22 % of the total surface during the last 8 years is considered to be an indicator of overgrazing and one of the basic evidences that land degradation is still relevant in these rangelands in spite of their regreening mainly due to a high precipitation amount since 2007.