Article

Although constituting one of the essential activities, practised by people everywhere in mediterranean arid and semi-arid zones, pastoralism - i.e. livestock and range management- is usually associated in complex ways with other soci al practices such as dryland plough farrning, brush clearing and fuelwood harvesting, etc. As a result, it is difficult or impossible to analyse the effects of pasloralist practices in isolation. Moreover, lo have any sense at all, such studies have to be carried out over ecologically significant periods of times. This article assembles data and conclusions from several different studi es carri ed out in various North African rangelands, and seeks lo provide insight into the consequences of pastoralism in these areas on biodiversity, in various aspects or hierarchicallevels ranging from whole ecosystems right down to infra-specific populations. Arising in the course of a long, presumed 'co-evolution' wilh man and his livestock, the native vegetation of these steppic zones actually responds just as poorly to extensification of pastoral pressure as lo an intensification thereof. By focussing on maximizing biodiversity of native taxa, intelligent pastoral management scheme - incorporating close attention to animai load and grazing pressure, lenght of grazing peri od, etc., - allow maintaining high levels of pasture productivity over long periods of time.