Rangelands are some of the most widely spread and dominant (on a land-area basis) renewable resources in the poorest agro-ecological zones of the world. Grazing has been - throughout the history of mankind - the most efficient process to convert cheap primary production to valuable animal products. The users of range resources are pure pastoralists (the nomads), semi-nomadic pastoralists and semi-sedentary pastoralists or agro-pastoralists (Khazanov, 1994). The communities which utilize range resources in the developing countries - particularly in Africa, West Asia, Central Asia, the Altiplanos and northern China - are predominantly poor and have been persistently overlooked by planners and policy-makers (Dyson-Hudson, 1982 and Abdullah, 1982 as quoted by Sidahmed, 1990). Over the last century, rangelands have been progressively stressed by overuse, the infringement of cultivation, unfavourable policies, urbanization and infrastructure development (Ginat and Khazanov, 1998; Scoones,1995; Thebaud, 1995). However, if properly managed and utilized, the world's rangelands can be a valuable, low-cost and sustainable source of high-quality animal protein and micronutrients and, as such, an important resource in the fight against hunger and malnutrition. Issues and basic problems of rangelands Figure 1: Range Degradation since 1945  Source: WRI (1994). Note: Percentages indicate the contribution of overgrazing to the total degraded area. However, the results of the long-term monitoring studies of the International Livestock Centre for Africa (ILCA) in East and West Africa (Ellis, 1992; Hiernaux, 1993) have challenged this assumption and provided evidence that climate, not livestock, is the main determinant of changes in arid and semi-arid environments and that rangelands are resilient and capable of recovery. For example, plant biomass in the Turkana region has been greatly influenced by rainfall fluctuations (Figure 2) and has progressively recovered following the lengthy drought of 1979-80. ILCA studies conclude that "the strong seasonality of rangeland production in the Sahel limits the risk of overgrazing damaging the environment to short periods and consequently confined areas." Moreover, related studies in Mauritania conclude that Sahelian vegetation appears very resilient to natural and grazing stresses because of the strong dynamism of the seed production, dispersion and germination cycle (Carrière, 1989). Figure 2: Monthly and Running Mean Normalized Difference Vegetation Index (NDVI) for Nysonyoka Territory, Turkana District Kenya  Source: Ellis (1995). The results and the impact of studies carried out by ILCA and others were discussed in two consecutive workshops supported by the World Bank, the Commonwealth Secretariat, the Overseas Development Institute and others (Behnke and Scoones, 1992; Scoones, 1995) and confirmed the conventional wisdom and traditional practices of pastorals and nomads throughout the history of these areas. Traditionally, pastorals adopted an opportunistic strategy of mobility and raised mixed species of stock with different preferences for the standing vegetation, so as to optimize the use of the limited vegetation available (Sidahmed, 1993). The core of recent interpretations that have led to so-called "rethinking range ecology" is appropriately based on the fact that degradation (or what was considered "desertification") is mainly influenced by rainfall patterns. But the management of the growing vegetation is equally important. According to Behnke (1993), the resilience of dryland vegetation is an outcome of the marked fluctuations between wet and dry seasons. Whereas growing vegetation is vulnerable to damage by grazing and trampling, dry-season vegetation is far less in demand and has its own defensive mechanisms such as the protection of living parts behind thorns or in the seeds. This has been confirmed during more than ten years of range monitoring by ILCA in Mali. The results (Hiernaux, 1993) indicate the negative influence of repeated grazing during the growing season on the replenishment of the soil seed-bank. On the other hand, minor changes have been attributed to the short-term effects of trampling, grazing and burning during the dry season. The studies identified close similarities between the changes induced by drought and those resulting from grazing pressure on the Sahelian rangelands, emphasizing the fact that it is policy approaches (limitations on livestock mobility and the fostering of seasonal dependence by providing feed inputs) that are leading to degradation. The conclusion reached by ILCA's long-term monitoring studies support the recent findings of other investigators in Sweden (Lund University, the Swedish Agency for Research Cooperation with Developing Countries), the UK (University College London), the US (Florida State University) and the World Bank (Nelson, 1988). The findings challenge the long-term claim by UNEP that the grazing areas of arid and semi-arid regions, particularly those in the desert margins of the Sahara (Pearce, 1992), are subject to irreversible degradation. These reviews and others have raised concerns about the quality and the relevance of the research conducted by UNEP on desertification in the Sahel. These concerns relate to the absence of evidence of good data or reliable scientific standards. For example, the satellite pictures examined by Ulf Hellden and his colleagues1 at Lund University in Sweden (e.g. Hellden, 1998), as well as polar-orbiting meteorological satellites analysed by Tucker and colleagues at the NASA Laboratory for Terrestrial Physics, indicate that the desert in the Sahara moves back and forth between its northern and southern boundary. According to the studies, these oscillations or north-south/south-north shifts are rainfall related. Furthermore, Nelson (1988) reported an astonishing recovery by what were considered irreversibly degraded areas in Ethiopia after rainfalls following the successive droughts of the 1980s. Several ecologists have attributed degradation around water points to livestock concentrations. However, this is a one-sided judgment because it excludes the benefits of the manure deposited in the circle around the water points as the animals come and go. Andrew Warren, a geographer at University College London, and Hellden, at Lund University, Sweden, have not found any evidence of desertification around water points in Sudan. A review of the surroundings of 77 water points in central Sudan and 20 on the desert fringe of Senegal was unable to establish a relationship between degradation and animal concentrations around the wells. This and other examples by Warren were brought to the attention of the UN in 1991. According to Warren "even the view that cattle watering points act as centres or poles of desertification is now questioned." Resilience is not only a feature of grazing lands in the arid and semi-arid tropics, but also in continental and temperate dryland areas. For example, a November 1992 IFAD environmental assessment mission to the Hainan Tibetan region of Qinghai Province could not find evidence allowing any firm conclusions regarding the claim that overgrazing is the cause of the degradation of robust and resilient summer and winter grazing areas. According to the mission, species diversity has been kept intact, and regeneration would be possible, in spite of the increasing yak and sheep populations. As in the case of long droughts in the tropics, periodic very cold winters cause heavy losses in the animal population, leading to a reduction in grazing pressure and a regeneration of the vegetative cover. 1/ Since the end of the 1970s, a team of geographers at Lund University in Sweden have been studying desertification in the Sudan. The studies have combined remote-sensing techniques, extensive field observations, national statistics and spatial modelling. In total, several hundred thousand square kilometers have been repeatedly observed by means of the study of historical reports, rainfall observations, old maps, aerial photos and high and low-resolution satellite data, combined with repeated field surveys. The team has not been able to verify the commonly accepted paradigm of desertification and land degradation in Africa. The team found that the importance of climatic impact on the productivity of the environment and the resilience of arid and semi-arid ecosystems have been seriously overlooked. According to Hellden (1998), local populations and environmental refugees of the Sahel region of Africa may be facing a climatic change rather than the effect of man-made desertification. If so, a new strategy for sustainable development is urgently needed. The team also found that the potential of using National Oceanic Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer(AVHRR) based-based normalized difference vegetation index-data for green-plant biomass-monitoring and early warning in the Sahel environment may be limited.
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Because
livestock is the major user of primary production in arid and semi-arid
regions, degradation has always been attributed to this subsector (Sidahmed
and Yazman, 1994). The United Nations Environment Programme (UNEP) singled
out human impact and, specifically, livestock grazing as the cause of
the irreversible degradation which has prevailed during the past two decades
(Pearce, 1992). According to the World Resources Institute (WRI, 1992)
"overgrazing is the most pervasive cause of soil degradation . .
. . In Africa and Australia, overgrazing causes 49 and 80 percent, respectively,
of soil degradation, mainly in semi-arid and arid regions." Although
the share of responsibility on the part of other influences (the introduction
of exotic species, fuel-wood harvesting, suppression of the natural fire
cycle, wildlife degradation and the conversion of rangelands to croplands
or human settlements, etc.) has been emphasized in subsequent UNEP publications
(WRI, 1994), overgrazing has always been considered the most important
factor (