Land degradation

The expansion of agriculture over the past three decades involved the cultivation of marginal areas, or clearance of important natural habitats such as forests and wetlands. Such conversion is a major driving force behind land degradation. In the Western Indian Ocean islands, for example, competition for land is so intense that coastal wetlands have deliberately been destroyed, and inland swamps have been drained and used as construction sites (UNEP 1999b). Many African rural communities survive by moving their cattle and crops as subsiding floodwaters expose enriched bottomlands and floodplains. More than 1.5 million people in Mali, Mauritania, Senegal and Sudan depend on this resource, as do vast numbers of wild herbivores (Maltby 1986). Draining wetlands for agriculture therefore threatens not only habitats and biodiversity but also the livelihoods of pastoralists and wildlife.

Loss of natural habitats has reduced vegetation cover and exposed soils to wind and water erosion. Wind and water erosion is extensive in many parts of Africa with about 25 per cent of the land prone to water erosion and about 22 per cent to wind erosion (Reich and others 2001).

Soil erosion also causes increased rates of siltation of dams and rivers, and increased risk of flooding in rivers and estuaries. In Sudan, for example, the total capacity of the Roseires reservoir - which generates 80 per cent of the country's electricity - has fallen by 40 per cent in 30 years due to siltation of the Blue Nile (Conway 2001).

Soil erosion reduces the productivity of land, requiring farmers to apply more and more fertilizers and other chemicals that help check falling productivity. However, many small-scale farmers cannot afford to buy these inputs and so get low yields.

Desertification vulnerability: Africa

Desertification vulnerability map of Africa locates the 46 per cent of the area at risk, of which 55 per cent is at high or very high risk Source: Reich and others 2001

As a result of the increasing recognition of soil nutrient depletion, a soil fertility initiative for sub- Saharan Africa (where the problem is particularly widespread) was established in 1996 (New Agriculturalist 2001). The objective is to strengthen action by the participating agencies to improve productivity and increase farm incomes through a combination of policy reform and technology adaptation. National soil fertility action plans are currently being prepared in 23 sub-Saharan countries. Organic farming systems offer considerable scope for addressing soil fertility problems as well as raising farm incomes.

Policies on land management have generally failed to address the root causes of land degradation which stem from colonial imbalances in land distribution, lack of incentives for conservation, insecure tenure and the failure to provide for diversified rural production systems (Moyo 1998). The United Nations Convention to Combat Desertification (UNCCD) points out that land degradation is intricately linked to poverty and that addressing this problem requires the participation of the resource users and, where appropriate, providing them with alternative livelihood options. Many African nations have signed and ratified the convention, and 15 countries submitted national action programmes in 2000. The Maghreb Arab Union, Southern African Development Community, the Economic Community of West African States and the Permanent Interstate Committee for Drought Control in the Sahel also submitted sub-regional plans. This has served to raise public awareness about issues of environment and resource sustainability, but the resources required to enforce these plans have frequently been inadequate (UNCCD 2001). A recent study estimated that desertification processes affect 46 per cent of Africa, and 55 per cent of that area is at high or very high risk. The worst affected areas are along desert margins (see map), and in total about 485 million people are affected (Reich and others 2001).

The success of land conservation programmes depends on several factors, and is closely linked with socio-economic conditions. Improving the distribution of wealth, access to resources and economic opportunities are key factors (SARIPS 2000). Peace and political stability are vital to improving resource and food security, as shown by the low per capita food production of countries where there is conflict, and resource security is necessary to implement and sustain conservation programmes. Improving extension services and access to appropriate and affordable technology, rural credit schemes and marketing assistance, and breaking down trade barriers are other essential requirements for sustainable agricultural development.