期刊名称：Science et changements planétaires / Sécheresse
印刷版ISSN：1147-7806
电子版ISSN：1777-5922
出版年度：2006
卷号：17
期号：1
页码：19-30
出版社：John Libbey Eurotext
摘要：Figures See all figures Authors Ahmed Aïdoud , Édouard Le Floc’h , Henry Noël Le Houérou rue des Poiriers, 35160 Breteil, 216, Fount del Mazet, 34830 Clapiers, 327, rue A.L. de Jussieu, 34090 Montpellier Key words: arid zone, ecology, livestock, pastoralism, vegetation, desertization, steppe Page(s) : 19-30 Published in: 2006 The steppes of Northern Africa, located between the annual isohyets of 100 and 400mm, cover some 630,000 km 2 between the Atlantic Ocean and the Red Sea. They are made of a low and sparse vegetation of perennial of sub-shrubs and, occasionally, a perennial grass (esparto). The natural land use has been for centuries the nomadic grazing of sheep, goats and dromedaries, together with the shifting cultivation of cereals. This land use model worked out throughout the historical times until the mid-XXth century in a globally stable society. At present, the main fact is the shrinking of the steppe areas and their occasionally extreme degradation. The consequence is that pastoral production from these rangelands has been characterised by a significant decline over the past five decades. Particularly quick and intense shifts took place under the growing pressure of population growth, which trebled over the past half-century in the five North African countries and increased ninefold over the century. This population growth generated the expansion of cultivated land and a shift in land management practices which are exacerbated by the impact of more or less severe periodic droughts. It is, however, difficult to distinguish the long term trends from the temporary impact of interannual fluctuations that are revertible. The confusion between these two concepts fuels the debate. This debate is unclear because of the scant and often unreliable baseline data sources on preexisting situations and for long-term evolutions follow-up. Such data sources (vegetation description, functioning analyses, historical statistical figures, etc.) are on the increase. They lead to a more reliable assessment of the biodiversity and potential productivity of these ecosystems, under the prevalent interannual climatic variability. The objective of the present chapter is to indicate the main lines of the present situation in the steppe environments, of their biodiversity, productivity and dynamics but also of livestock performance and of the overall impact of the incurring changes on geographic space, environment and people. We also identify possible remedies to the situation: exclosures, deferred grazing, restoration operations, rehabilitation, agroforestry and sylvopastoralism, etc. If the sometimes anarchic utilization of steppe resources leads to profound changes in the environment, one should not, however, overgeneralize the established facts of progressing desertization. Some types of steppe keep a good enough level of resilience that makes their rehabilitation feasible under a rational management. It proves it is important to consider a hierarchical approach involving specialists from the various disciplines concerned (ecology, hydrology, agronomy, pastoralism, livestock husbandry, socio-economy, etc.).
