Desertification, drought and their consequences

FAO

http://www.fao.org/3/x5317e/x5317e01.htm

Abstract


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.

Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.