Desertification: the persistent degradation of dryland ecosystems by climatic variations and human activities.

Desertification occurs in all continents except Antarctica and affects the livelihoods of millions of people by the reduction or loss of biological or economic productivity. Drylands occupy 41% of the world's land area and in 2000 were the home to about 2 billion people, roughly a third of the human population

All drylands are potentially threatened by desertification. It is thought that some 10% to 20% of drylands, or some six to twelve million square kilometres may already have been degraded. As a comparison the area of China is 9.6 million square kilometres.

Most drylands are found in developing countries and when compared to the rest of the world, inhabitants of drylands lag far behind in terms of human well-being and development indicators.

The level of poverty will vary with the level of aridity and from region to region, but populations continue to rise in spite of high infant mortality rates that can reach 54 per 1000 in some areas. Growth in health and education infrastructure, facilities and services continues to be slow

The traditionally harsh environment forced dryland populations to be flexible in their use of land. This resulted in a livelihood based on a mixture of hunting, gathering, farming and herding that was very suitable for this sort of environment.

Expanding populations have brought the need to produce more food and about 5 million square kilometres of former grassland is now used for growing crops. Much of this is on the margin of what farmers can use without some form of irrigation and droughts often lead to crop failure. Globally more than 2 million square kilometres of this rain-fed cropland has been moderately or severely degraded and each year about one per cent is abandoned to become desert.

Irrigation projects have been developed in many areas but these have often had a strong impact on inland waters, increasing salinity and causing a decline in biodiversity, leading to further desertification.

Looking to the future, the process of desertification is expected to increase. Poverty and the unsustainable use of land will continue to be the main factors driving this. Climate change is an important factor that is linked to desertification, but its impacts will vary according to the region and the management approach that is adopted

In order to stay ahead of desertification and lessen the combined effects of climatic variations and human activity, it is important for nations to improve agricultural and grazing practices in a sustainable way. There must be a fresh way of thinking. What has been called a ''culture of prevention'' must be created, involving changes of attitude in both governments and populations.

A number of actions are possible and these can include: