Desertification

Author: Communications Unit ~ Desert Research Foundation of Namibia

( Article Type: Overview )

Desertification is defined as ‘land degradation in arid, semiarid and dry sub-humid areas resulting from various factors, including climatic variations and human activities’. The important point is that there is loss of productivity of the land. Land that originally could support many people with, for example, crops, pastures for livestock and wild foods, becomes more difficult to farm and less able to provide the necessary resources for people and animals.

A desertified area may look more barren and desert-like, but this is not always the case. Unfortunately, desertification is often misinterpreted as encroachment of deserts (especially of sand dunes) on previously fertile land. The true physical manifestations of desertification include deforestation, deterioration of rangelands, soil erosion, bush encroachment and salinisation of soils.

Issues
Three essential components of desertification should be noted:

• Human influence is almost always dominant, but climate – particularly potential long-term climate change – may also have an influence;
• The processes are not the result of normal rainfall variation or drought, but may be initiated or worsened by these shortterm factors;
• The processes are more or less irreversible, except possibly over a long time period and usually at considerable cost.

Human influence comprises actions such as permanent settlement in areas that were previously used on a seasonal basis, and excessive pressure on land from large numbers of livestock, which do not give any chance for recovery of favoured grasses and young trees. The most palatable grasses (which includes the perennials) diminish and do not leave a seedbank as they are grazed heavily. In addition, the physical action of the hooves of many livestock destroys grass clumps and prevents new ones from starting. Similarly, young trees do not germinate and there is no replacement of old ones.
These processes are exacerbated by years that are drier than normal, and in drought years degraded land is likely to look more barren and desert-like, especially when livestock are also in poor condition. But the process of degradation does also continue during periods of normal or good rainfall, if the causal factors persist.

It is difficult to reverse the pattern of degradation and to restore the productivity of land, especially if it has been degraded for many years. Soil that is lost by erosion takes a very long time to recover – at least hundreds of years. Once lost, the seed-bank of grasses may take years or even as long as decades to build up again. Areas that have become impenetrable because of overgrowth of invasive trees, such as bushy thorn-trees, must be physically cleared before they can be utilised by livestock. Soils that have become salinised by inappropriate irrigation methods will be infertile until the heavy salt load is eventually washed out by natural rainfall, a process that is obviously slow, especially in areas where rainfall is low already.
A failure in policies and planning to accommodate the variability of climatic conditions in tropical and subtropical dry lands is a main contributing factor. Planning for drought conditions in a systematic way, for instance, is rarely carried out, with the result that emergency measures are engaged unnecessarily. The emergency measures may even become the norm, which carries the likely impact of over-exploitation of scarce resources such as groundwater and pastures, and permanent settlement on lands, which are better suited to seasonal use.

Scope
In 1994 it was estimated that about 30% of the agriculturally usable land in Africa was degraded, and about 23% of the usable land worldwide. Strong and extreme degradation amounted to about 8% in Africa. Converting these figures into monetary terms is even more difficult than making the estimates in the first place. The total figure for Africa probably runs into hundreds of millions of dollars.

Solutions
Improved management of land that recognises natural variability of rainfall and finds alternative ways of making a living, especially in drought conditions, has had successful results. Many of the policies and laws that govern farming and land tenure are the root cause of desertification. Correction of these policies so that they promote sustainable management of natural resources is necessary for longlasting solutions. In parallel with this, the restoration of degraded land can only be sustained if it carries the support and dedication of the farmers on the ground.

Many countries in southern Africa are developing and implementing National Action Plans to try to combat desertification. The work has to be carried out on many fronts, from the level of farmers and communities, to government and even non-governmental agencies that provide them with support, up to the level of national and international policies. The International Convention to Combat Desertification, implemented by the UN and member countries that have ratified the Convention, is the main organising body.