I. Desertification, drought and their consequences
Back to contents - Next file
Features and factors of desertification and drought
Consequences at the local and national level
Consequences at the global level
Desertification is a global phenomenon of land degradation which reduces the natural potential of the ecosystems and renders rural populations vulnerable to food shortages, the vagaries of weather and natural disasters. Desertification control must form an integral part of the socioeconomic development programmes, taking account of the short-term needs and long-term aspirations of the populations affected by it.
To implement these programmes, a comprehensive and participatory approach is needed, for which the keywords are: integration, concertation, land use planning, decentralisation, and lasting and flexible technical and financial assistance. The effectiveness of combating desertification depends on carefully interlocking the aspirations of the affected populations with the policy concerns of governments and technical services. This excludes both top-down and paternalistic actions, as well as demagogic actions which leave the local communities alone to define and implement activities. For a good interconnection, the local community must have sound liaison persons who are able to express their points of view and represent them effectively. Programmes and projects with a participatory and integrated approach are becoming more and more numerous. The democratization and decentralization processes now beginning in a growing number of countries, the failure of classic development projects, the improved circulation of information, and the increase in the number of grass roots organizations - NGOs - are but a few of the factors that have helped this type of approach to emerge.
Features and factors of desertification and drought
1. Desertification, as defined in Chapter 12 of Agenda 21 and in the International Convention on Desertification, is the degradation of the land in arid, semi-arid and dry sub- humid areas resulting from various factors, including climatic variations and human activities. It is accompanied by a reduction in the natural potential of the land and a decrease in surface and ground water resources. But, above all, it has negative repercussions on the living conditions and economic development of the people affected by it.
2. Desertification is a worldwide phenomenon: it affects about two-thirds of the countries of the world and one-third of the earth's land surface, on which approximately one billion people live. Desertification does not concern natural deserts, and can only occur on land which is vulnerable to the desertification process.
3. The vulnerability of land to desertification is mainly due to the climate, the topography, the state of the soil, the natural vegetation, and the ways in which these resources are used.
4. Climate affects the chemical and biological deterioration of the soil and conditions water and wind erosion. The state of the soil (texture, structure and chemical and biological properties) is the major vulnerability factor, particularly in the dry sub-humid zones where the influence of climatic factors is less predominant. Natural and cultivated vegetation plays an essential role in protecting the soil, particularly trees and bushes which, due to their long life and their capacity to develop powerful root systems, guarantee effective protection against soil degradation. Their disappearance considerably increases the vulnerability of the land to desertification. Lastly, even under the same climatic conditions, topography, soils, vegetation, and cover status, and with the same population density, the vulnerability of the land to desertification could vary widely depending on the land-use system and human activities.
5. Droughts occur frequently in the areas affected by desertification, and are generally a natural feature of the climate of such regions. The relations between desertification and drought on the one hand, and human influence on the other, are unknown and complex. Occasional droughts (due to seasonal or inter-year variations in rainfall) and long-term severe droughts can both be caused or aggravated by the influence of man on the environment (the reduction in vegetation cover, the change in the Albedo effect, changes in the local climate, the greenhouse effect, etc.). Human activities can, therefore, accelerate desertification and aggravate its negative consequences on people. Furthermore, land degradation can hasten the effects of drought by reducing the chances of local people to face difficult, dry periods.
6. Climatic disturbances may be both a consequence and a cause of desertification. The destruction of the natural grass and woody vegetation cover in dry lands affects the topsoil temperature and air humidity, and thus influences the movements of atmospheric masses and rainfall. Furthermore, the destruction of soil cover encourages wind erosion.
7. Although the cycles of drought and climatic disturbances can contribute to the development of desertification, it is mainly caused by overgrazing, land clearance, over-exploitation of cultivated and natural lands, and by generally using land in a way that is inappropriate to local conditions. Human activities connected with agriculture, livestock and forestry production vary widely according to the country, type of society, land-use strategies, and the production and conservation technologies employed. In many cases, traditional and sustainable rainfed agricultural methods (food crops and alternating fallow periods) and pastoral practices are no longer suitable for present-day conditions. Strong demographic pressure has increased the demand on land resources, which is aggravated when cash-crop farming takes over lands used for subsistence farming and pastures used by nomadic peoples. However, the impact of human societies on natural resources does not depend solely on the demographic density, and the notions of "carrying capacity" and "critical threshold" must be handled with care. There are many examples to demonstrate that these criteria can vary enormously, depending on the strategies and the technologies used by the people.
8. The severeness of desertification depends on factors which vary from one region, country, or year to another. These include:
(i) the severity of the climatic conditions during the period considered (particularly in terms of annual rainfall);
(ii) population pressure and the standard of living of the people involved;
(iii) the level of the country's development, and the quality of the preventive measures taken.
Consequences at the local and national level
9. By impoverishing the natural potential of ecosystems, desertification also reduces agricultural yields and make them less predictable. It therefore has a bearing on the food security of people living in affected areas. In order to attend to their most urgent needs, the people develop a survival strategy which, in turn, aggravates desertification and impedes development.
World soil resources
10. The most immediate and frequent consequence of these survival attitudes is the increased overexploitation of accessible natural resources. This strategy is often accompanied by a breakdown in solidarity within the community and within families, which encourages individualism and exclusion. It often leads to conflicts between different ethnic groups, families and individuals.
11. Lastly, desertification considerably heightens the effects of climatic crises (droughts) and political crises (wars), regularly leading to migration, suffering and even death to hundreds of thousands of people worldwide.
12. These consequences, in turn, weaken the economies of the developing countries affected by desertification, particularly when they have no other resources than their agriculture. This is particularly true in the case of African countries in the dry zones: their economies are unable to offset the increasingly serious effects of desertification, and they have to deal with emergency situations created by drought and desertification. The increasing debt burden also reduces their possibility of making productive investment in order to break the spiral of underdevelopment.
LES DEUX FACES DE LA DESERTIFICATION
Selon qu'on privilegie les dimensions physiques (climat, sols...) ou humaines (environnement economique et evolution des societes) de la desertification, on mettra en avant des faisceaux de cause, et de solutions, radicalement differents.
Ainsi, interpreter la desertification comme un phenomene climatique conduit a stinterroger sur les causes des secheresses puis sur le role des evolutions globales ou regionales du climat, enfin sur les causes anthropiques de ces evolutions. La desertification n'apparaitra que comme un épiphénomène des changements climatiques globaux.
Symétriquement, si l' on est attentif aux mutations des sociétés et des économies, les crises répétées que traversent les zones sèches apparaitront comme un résumé frappant des situations, des contradictions et des impasses rencontrées dans bien des pays en développement. Des lors, la question de la desertification risque de se diluer dans la problématique du développement durable.
On peut analyser ainsi l'échec de la première conférence des Nations unies sur la desertification, a Nairobi, en 1977. En affirmant avoir pour objectif immédiat de "prévenir et d'arrêter l'avancée du désert et, la ou il est possible, remettre en état les terres désertifiées pour les rendre a la production", en privilégiant les aménagements hydrauliques, les mesures de conservation des sols ou de réhahilitation des parcours de pâturage, en créant des "ceintures vertes" , son Plan d'action commettait une erreur de perspective en identifiant la desertification a l"'avancee du désert", en négligeant de nombreux aspects socio-économiques et en mettant trop l'accent sur la restauration des zones désertifiées au détriment de la gestion des zones sèches.
Il s'agit donc de faire reconnaître la desertification comme un phénomène complexe et spécifique, bien que non isole, ou l'action de l'homme le dispute aux causes climatiques.
Extrait du Courrier de la Planete
No.20. dec janv. 1994-95
Countries affected by drought in Africa.
13. But desertification can also lead to some changes in certain behaviour patterns. These include, in particular, the attitude of the women who have to cope with the problems caused by the absence of the men, who have left to seek work elsewhere. The extra burden of work and responsibility which the women have to bear have two consequences:
(i) women are now demanding greater rights to the land, particularly the land they manage themselves. Women are gradually gaining the approval of their communities and are forcing land title rules to change. The combat against desertification should not ignore or under-estimate this new power relationship;
(ii) women are becoming increasingly aware of the need to space childbirth. In many places in the world, however, they frequently come up against cultural and religious taboos, the disapproval of the men, and reluctance on the part of their governments to support them.
14. While the survival attitudes caused by desertification have often led to a decline in traditional agricultural know-how, they have conversely encouraged the development of consciousness, particularly relating to the environment and its conservation. The microprojects that have been implemented in many places over the past 15 years have made it possible to build up a store of knowledge allowing for the implementation of new approaches. At the same time, in many regions, the rural people's perception of their environment and the priority they give to a better relationship with it have changed. Increasingly, rural people are realizing that:
(i) the fragile environment on which they depend for their survival is being neglected or over-exploited, and it is now necessary to rehabilitate it and manage it sustainably; and
(ii) the environment belongs primarily to them, and they must take the responsibility for the land and organize themselves (in groups, cooperatives, village development associations and other local associations).
15. Greater awareness at the highest level of governments has made possible the adoption of the United Nations Convention to Combat Desertification and the commitment by the Heads of State of most countries in the world to enter a partnership contract to effectively combat desertification by taking a participatory approach.
Consequences at the global level
16. Desertification also has consequences at the global level, primarily because of the influence on carbon exchange. The large amount of carbon stored in the vegetation in the dry zones, averaging about 30 tonnes per hectare, decreases when the vegetation is depleted or disappears. Carbon-rich soils, frequently found in dry zones, store a substantial amount of this element (nearly half the total quantity of carbon is stored in the organic matter in the soil, much more than is found in the world's vegetation): the destruction of these soils has a very powerful effect on the carbon cycle and boosts the greenhouse effect as a result of the release of carbon.
17. Another consequence of desertification at both local and global levels is the reduction in biodiversity, as it contributes to the destruction of the habitats of animal and vegetal species and micro-organisms. It furthers the genetic erosion of plant varieties and species living in fragile ecosystems. It is extremely difficult to assess this loss because of our incomplete knowledge of the features, location and economic importance of the biodiversity of dry zones. A substantial part of this is still largely unknown to scientists, although local populations are very familiar with it. Reducing biodiversity directly affects the food and health of the local people who rely on a large number of animal and plant species. It is also a loss to the whole of mankind. Since many genetic strains of cultivated plants which form the basis of the food and health of the world's population originate in dry zones, their disappearance can jeopardize the possibility of combating specific diseases or epidemics.
The twelve megacentres of cultivated plants
18. Lastly, desertification directly reduces the world's fresh water reserves. It has a direct impact on river flow and the level of ground water tables. The reduction of river flow rates and the lowering of ground water levels leads to the silting up of estuaries, the encroachment of salt water into water tables, and the pollution of water by suspended particles and salinization, which, in turn, decreases the biodiversity of fresh and brackish water, reduces fish interferes with the operation of reservoirs and irrigation canals, increases coastal erosion and adversely affects human and animal health. Lastly, desertification leads to the accelerated and often uncontrolled exploitation of underground fossil water reserves, and their gradual depletion.