Shorter version published as:
Batterbury, S.P.J. & A.Warren. 2001. Desertification. in N. Smelser & P. Baltes (eds.) International Encyclopædia of the Social and Behavioral Sciences. Elsevier Press. Pp. 3526-3529.
Key words: desertification, Africa, dry lands, deserts, drought, land degradation, Sahel, Dust Bowl, UNCED, international agreements
Desertification is difficult to define in measurable terms, and many of the assertions made in its name have proved alarmist. In large measure, the problems arise because environmental damage is judged differently by different cultures at different times. For this reason, evidence for overgrazing, desert advance, climatic change, the fragility of dry ecosystems, and the effects of increasing population have all been elusive. Nonetheless, the term has an interesting history, dating from fear about the spread of the desert in the US midwest and in West Africa, which dates from the early years of the 20th century. The severe desiccation of the 1970s and 1980s revived the term, and international interest in it. “Desertification” is best seen as a portmanteau word for serious environmental problems in dry countries, many of which are among the poorest on earth. One problem is drought. Although many ecological and social systems have evolved to deal with drought, societies in rapid transition are vulnerable. Another problem is “desiccation” (the longer term drying out). There have indeed been long droughts or dry periods in recent history and they have caused havoc in many societies. Finally, there is “degradation”. One form of degradation, overgrazing, is now thought to be far less of an issue than it was twenty years ago. Soil erosion is another form of degradation, and although probably very serious in some of the drylands, not enough is known of its drivers. For all the difficulties with the term, it has a future, if only in the United Nations Convention to Combat Desertification, to which many dry countries have signed up, and which will require planning into the early 2000s.
The importance of desertification for the peoples of the world’s drylands should not be underestimated, despite considerable uncertainty about its meaning. Firstly, the term, for all its problems, envelops a set of processes, sometimes listed as drought, desiccation and degradation, that pose very real and severe challenges to drylands, and have strong knock-on effects on society. Secondly, desertification language is deeply entrenched in policy circles and in the current UN Convention to Combat Desertification (CCD), and will inevitably continue to inform the financing of development interventions in drylands.
The “Agenda 21” document of the 1992 United Nations Conference on Environment and Development (UNCED) defined desertification as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities”. The processes of degradation were said to be soil erosion, nutrient depletion, crust formation, salinization, reduction in pasture and agricultural productivity, loss of biodiversity, and reduction in vegetation cover in susceptible drylands. Of course, uncertainties abound: the circumstances fostering reversible or irreversible change; the resiliency of different semi-arid environments; the different roles of natural and anthropogenic driving forces; and the synergies among these elements.
Scientists were exercised as early as the 1920s with the ‘the advance and spread of the desert’ in Africa. It was then that France began the first studies of the process in West Africa, finding evidence of mobile sand dunes, human fossil remains in now-dry areas, and declining annual rainfall. It was concluded that the Sahara had grown, and was still growing, owing to poor land management, which had worsened under the colonial regime.
These early judgements
preceded what environmental historians are now discovering to have been a much
more traumatic event, the American ‘Dust Bowl’ of the 1930s. Sears’s Deserts on the March (1935)
evoked accusations of widespread anthropogenic degradation. He and others
believed they also had evidence of widespread environmental degradation in the
dry lands of
In dryland Africa, severe drought and famine in the 1970s, following decades of good rainfall, again revived the desertification debate, with depressing reports of desert advance appearing in scientific publications and the media. This alarm stoked the United Nations Conference on Desertification (UNCOD), held in Nairobi in 1977. UNCOD, and the National Plans of Action agreed by each participant dryland country at that meeting, still viewed people as the main agents of desertification.
Research into the links between climate, management and degradation has taught us a great deal since the 1970s. Since then, many detailed studies of human-environment interactions at the local scale have been carried out in the drylands, spurred on by advances in climatology, soil science, botany, geo-informatics, agronomy, and the social sciences.
This research, conducted by numerous scholars from the natural and social sciences, offers a longer-term view of what happens as rainfall fluctuates, or when soils are lost and gained. More generally it has examined the complexity of the linkage between resources and people in the drylands, and the role of adaptive local resource management. Above all, it is now possible to challenge notions about an equilibrium state or “carrying capacity” in these environments and from there to challenge the desertification narrative with better, if still imperfect evidence.
Yet laying the desertification discourse to rest is difficult. At least six themes remain essential elements of the desertification debate.
Advance of desert. Large-scale Saharan expansion has not been proven within the period of the historical record. Desert advance in the Sudan has been asserted since the 1930s, but Helldén (1991) found no such evidence from satellite imagery, settlement histories, sand movements, and degradation conditions around boreholes. The current view is that the Sahara expands and contracts periodically as rainfall varies. Desert advance (as in the severe drought of 1984), and localised degradation, is usually short-term (Tucker et al. 1991; Nicholson et al. 1998).
Resilience of dryland ecosystems and land-use systems. Degradation is, therefore, usually localised and ephemeral [short-lived], largely a function of the complexity of relationships that exist between humans and natural systems. Semi-arid ecosystems, far from being fragile, exist in a range of semi-permanent ‘states’ dictated by disturbance, drought, fire or insect attack; they are well adapted to these forces. Similarly many indigenous management systems redistribute nutrients, plants, grazing pressure and water to create ‘enriched’ patches in the landscape.
Influence of grazing and livestock. The UN Atlas of Desertification (1992) asserted that 58% of soil erosion in dryland Africa was the result of overgrazing by livestock, lending support to Garret Hardin’s ‘tragedy of the commons’ hypothesis, that said that too many herders all using the same piece of rangeland would tend to degrade it through their own selfishness. Such figures gave way to more conservative estimates in the latest version of the Atlas (Thomas and Middleton, 1996). There is now greater confidence about the heterogeneity and patch dynamics of pastoralist grazing strategies so critical to many drylands. Less existing vegetation is not necessarily worse vegetation in terms of biodiversity. It is difficult to overgraze in a dynamic non-equilibrium system, dominated by annual grasses, where the external forces like drought are more powerful animal numbers as influences on rangeland quality.
Effects of increased population in rainfed dryland agricultural systems. No necessary Malthusian link exists between elevated population levels and resource degradation. [see earlier indv 103 lecture] . Indeed, because there is often an incentive for rural people to invest in anti-degradation measures in these circumstances, more people (and labour) may mean less erosion, and the initiation of compensatory risk management strategies.
Soil erosion and fertility decline. Although topsoil erosion does occur in drylands and soil is blown or washed away, these processes do not themselves necessarily result in degraded landscapes. Soils are often replacable or may be very deep, and can accumulate down-slope or down-wind where they may be more valuable to local people. Indigenous dryland soil conservation systems are impressive. Yet even after decades of research, soil erosion and the values placed upon it by society are very difficult to measure.
Climate Change. There are two issues here. Charney & Stone (1975) suggested that devegetation might induce regional drought —bare soils are cooler because they
reflect more solar energy and cool surfaces discourage rainfall. This hypothesis remains disputed. Current research provide
strong evidence that changes in surface characteristics, including vegetation,
affect local and regional rainfall patterns significantly. Some climatologists
however, find little evidence in this claim as registered in the coarser scale
climate record (Williams & Balling, 1996). As well, potential global
warming and the ENSO (El Niño-Southern Oscillation)
will have differential, and as yet uncertain effects
on certain drylands, with the majority of current
models suggesting increased rainfall and temperature variability in
and interventions are strongly linked. For example, when scientists pinpointed
advancing deserts, the policy response, was ‘plant green belts!’ [around the
Anti-desertification measures have been international in scope. A suite of international institutions materialised after the great Sahelian drought of the late 1960s and early 1970s. First, the United Nations Sudano-Sahelian Office (UNSO) was charged with combatting drought, later taking on desertification issues. It was later joined by the UN Environment Programme and the FAO in these roles. Scientific panels and advisors produced a “veritable sandstorm of literature” (Mortimore 1998:23) on the complexities of drylands. In general, the prognosis was gloomy: 10% of the earth’s surface was human-made desert; and the process would continue. Desertification became enshrined in international policy.
African states absorbed
some of UNCOD’s recommendations from the late 1970s,
although they were held back by poor funding. Projects were initiated, most
designed to arrest soil erosion. Some were implemented without adequate local
consultation or participation. Many, like the GERES project in
ramifications followed in the post-UNCOD, post-Sahelian
drought era. In
A broadened, perhaps softened conception of desertification suggests a new range of policies that, given sensitive application, may prove more successful because they are more trusting of dryland populations and more aware of ecological diversity. New initiatives are based on a better understanding of the three main issues in dryland management: drought, desiccation and degradation. Drought is common currency among dryland folk. It may not be welcome, but people clearly have a portfolio of coping strategies to deal with it, and reflexive management that constantly adapts to an ever-changing situation. These indigenous systems are now being supported, rather than replaced or obstructed. Desiccation is known to have been frequent in the history of human occupation of drylands. Large-scale shifts in livelihood practices occur under progressive aridity, but Sahelian drought illustrates that relief, restocking and resettlement are necessary when this happens. Degradation requires a range of responses. Rich repertoires of conserving indigenous techniques exist, some – like permeable contour bunds - already improved through hybrid experimentation between farmers and scientists. Drylands and dryland peoples and their economies are heterogeneous. Policies increasingly aim to protect this diversity, rather than erase it. Greater clarity of land tenure security is needed, and rangeland areas require special forms of collective management . In brief, livelihood security is essential to good conservation.
4. The Convention to Combat Desertification
UNCED, the Rio Conference, held in
The Convention to
Combat Desertification (CCD) came into force on
In the absence of well adapted technologies, life in drylands is harsh. That degradation of these lands follows from social and climatic processes is not in dispute. But whether degradation amounting to desertification of the magnitude assumed in the early debates, or even in the recent Convention [CCD], has been strongly challenged by the research and other communities. Nonetheless, desertification remains a powerful narrative that has captured the imagination of certain policy makers, governments, and scientists, and it has persisted with peaks and troughs of interest since the 1930s. Its power is problematic, since “the search for accuracy appears to be vulnerable to generalisation, over-simplification and distortion for political or funding purposes” (Mortimore1998:33). Desertification has certainly served specific constituencies quite well: -
Tackling the various processes that the term desertification subsumes is a major challenge, given that dryland populations suffer the impacts of droughts and desiccation, and need to exploit land, water, and timber resources in ways which often result in degradation. As an explanatory term, however, desertification has been used too broadly and too loosely, and this has been counterproductive.
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