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Definition and general approach to the problem

How to define desertification
What lands and areas are prone to desertification?
What are the main causes of desertification?
What are the main consequences of desertification?

How to define desertification

Chapter 12 of Agenda 21, as approved by the United Nations Conference on Environment and Development (UNCED), defines desertification as "land degradation in arid, semi-arid and dry subhumid areas resulting from various factors, including climatic variations and human activities". This definition is simplistic, as it does not express clearly the constant interaction between climatic factors and human activities - the latter often being decisive in triggering desertification processes.

Nevertheless, it seems important to state that, in certain parts of the world, desertification processes (land degradation) operate in the absence of human activities, where such activities are negligible because of low population density.

The natural recurring drought processes, which may be caused by global climatic changes that are difficult to evaluate, may lead to land degradation, thus endangering the peoples in and around those areas, or preventing future land use. Although it might appear vain to combat such "geological" desertification, it is nonetheless essential to help local communities confront the situation and adapt to it without making it worse.

The link between desertification and human activities is thus a generally accepted concept and FAO suggests that this link be clearly defined as:

"The sum of the geological, climatic, biological and human factors which lead to the degradation of the physical, chemical and biological potential of lands in arid and semi-arid zones, and endanger biodiversity and the survival of human communities."

This definition is close to that approved by the 1977 UN Conference on Desertification, in Nairobi:

"... intensification or extension of characteristic desert conditions; the process entails a reduction in biological activity and plant biomass, in livestockcarrying potential of land, in agricultural yields and a decline or degradation in man's living conditions."

What lands and areas are prone to desertification?

FAO considers the criteria established at the Nairobi Conference as the basis for the concept of "desertification risk", assessed by measuring land vulnerability in combination with current and future demotic and agricultural pressures. To use such criteria means considering desertification processes as evolving according to changing human and climatic factors. As a consequence, each country needs to have ways of analysing these processes on the basis of globally accepted criteria

As a first measure, FAO recommends that countries some 99 according to the United Nations Environment Programme (UNEP) - with arid, semi-arid and dry subhumid lands prone to desertification be encouraged to tackle these processes, which affect nearly one thousand million human beings living on 35-40 million km2 or about 30 percent of the world's land surface.

What are the main causes of desertification?

First it is advisable to state that desertification as previously defined can only occur on land prone to desertification processes. The vulnerability to desertification of land is determined by current climate, relief, and the state of the soil and natural vegetation. Climate has a major influence through three factors rainfall, solar radiation and wind- which all affect physical and mechanical erosion phenomena and chemical and biological degradation. Relief acts mainly to exacerbate water erosion. The state of the soil, in terms of its texture, structure and chemical and biological status, is a predominant factor in dry subhumid zones, where climate has less impact; it plays a crucial role in vulnerability to desertification through human activities. The same applies to the state of the natural vegetation: the result of past and recent influences; of climatic, pedological and often, human factors. Because of their longevity and powerful root systems, trees are a primary source of protection from soil degradation and their absence, too often caused by human action, is a serious handicap.

Human activities are the main factors triggering desertification processes on vulnerable land. These activities are many and vary by country, society, landuse strategies and the technologies applied. The impact of human society does not depend solely on its density. FAO believes that the concepts of "carrying capacity" and "critical threshold" need to be considered with care, as many examples demonstrate that these criteria can evolve according to the strategies and technologies applied by local people.

Some of the human activities that can cause desertification are:

All these activities derive from two root causes. The first five are typical of poverty and underdevelopment, while the rest result from "modern" development that disregards the impact of the technologies used on land sustainability.

Factors typical of the first category include:

The second category includes factors such as:

What are the main consequences of desertification?

The consequences of desertification - the phenomenon of land degradation - depend on four factors that vary by region, country and year:

The poorer the peoples and the less developed the countries involved, the more profound will be the future effects of desertification, and the greater the potential for tragedy when natural conditions, especially climatic, become difficult.

Desertification should be viewed as a breakdown of the fragile balance that allowed plant, human and animal life to develop in arid, semi-arid and dry subhumid zones. This breakdown of the equilibrium and of the physical, chemical and biological processes that sustain it, represents the start of a process of self-destruction for all elements of the life system. Thus soil vulnerability to wind and water erosion, the lowering of the water-table, the impairment of the natural regeneration of vegetation, the chemical degeneration of soils - themselves all immediate results of desertification - worsen the situation. Desertification feeds on itself.

Consequently, the effects of desertification are extremely serious and often dramatic for the poor populations of developing countries. By limiting natural potential desertification reduces production and makes it increasingly precarious. Forced to attend to the most urgent things first, populations resort to survival strategies that unfortunately make desertification worse and prevent any development.

The most immediate and generally widespread of these survival strategies is to intensify overexploitation of the most readily available natural resources, but at the cost of enormous effort. The second strategy is to sell off everything owned, including agricultural equipment, to cope with the monetary needs of development (e.g. schooling, social services, contributions to pump maintenance), or food crises (buying food). The third strategy is increasing rural migration: this may simply involve men and young people leaving for a seasonal or longer-term job in other areas of the country, particularly the towns, or going to other countries; or the migration may take on the proportions of a population exodus in search of better living conditions.

These survival strategies are often accompanied by breakdowns in the integrity of communities and sometimes of families. When survival is difficult, people become withdrawn and sometimes strongly individualistic, which leads to ethnic, family or individual conflict.

Finally, desertification exacerbates the effects of climatic (drought) and political (war) disasters, regularly leading to the suffering and death of hundreds of thousands of people throughout the world.

All these factors weaken still further the economies of developing countries affected by desertification, particularly those countries that have no resources other than agriculture and those where almost all the territory is affected. In this respect, African countries in arid, semi-arid and dry subhumid zones are particularly prone to desertification and affected by its consequences. Their economies are powerless to break the fatal cycle of poverty that leads them to face up to emergencies by taking on more and more increasingly untenable debt. This in turn precludes any future possibility of productive investments to break the circle of underdevelopment.

However, desertification can lead to a positive change in some behaviour, especially that of women facing problems caused by the absence of men who have gone in search of work, and the aspirations of young people towards a less demanding life. This extra work and responsibility lead to two new attitudes:

While desertification has brought about a sharp reduction in agricultural equipment, it has also helped to multiply and broaden technical knowledge, especially on the environment and its conservation. Micro-projects undertaken in many places over the last 15 years have resulted in a wealth of knowledge and some practical techniques. This is a starting-point that should not be neglected. Similarly, many rural people's perception of the environment and their relationship with it is changing, or has already changed in some places. The environment is increasingly being conceived as:

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