Desertification

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Desertification

Introduction

When vegetation is lost from a dryland area, surface soil blows away leaving bare, dry, unprotected layers that harden and becomes less infertile. This type of land degradation is known as desertification. Up to 20% of the world’s drylands (excluding areas that are already deserts) have now undergone some degree of desertification with around one billion people at risk of its effects. The term does not refer to the expansion of existing desert.

The two main causes of desertification are climate variation and human exploitation of vulnerable drylands. Desertification has many adverse effects, both economic and ecological. Loss of crops and water supplies lead to hardship, famine, and disease, while habitat loss causes loss of biodiversity. The best way to combat desertification is to try to use drylands in a more sustainable and appropriate manner, so that these fragile ecosystems are conserved.

Historical Background and Scientific Foundations

The United Nations defines desertification as the persistent degradation of land in arid, semi-arid, and dry sub-humid areas, all of which have limited water supplies. Such drylands are especially vulnerable to both climatic variation and human activity, which are the leading causes of desertification. Population growth and the resulting increased demand for food lead to cultivation of less than ideal land, such as the dryland areas. Meanwhile, although the relationships between global warming and desertification is complex increased temperature will, on the whole, encourage drought.

Loss of vegetation is the key underlying cause of desertification. Plants hold moisture in the soil and provide a natural windbreak. Without them, the soil is blown away and becomes increasingly drier and unable to support plant life, including crops, forage for livestock, and wood.

Drought tends to lead to vegetation loss and desertification, because the plants do not receive enough water. A switch from nomadic to sedentary, and increasingly intensive, farming tends to encourage overgrazing, which occurs whenever there are more livestock than the land can support without degradation. Deforestation, through logging activities or clearing land for cash crops or other export activities, also causes desertification through loss of trees. Inappropriate irrigation schemes may cause increased salinity of the soil, which also leads to extensive degradation.

There are many underlying human factors underlying the causes of desertification. Increased populations will naturally put more pressure on drylands to yield food, which can lead to overgrazing and overplanting. But underpopulation can be a problem too, in some areas. For instance, many hillside terraces in Yemen have become neglected and are at risk, because there are not enough people left to care for the land, following extensive migration to neighboring oil-rich countries. War or natural disaster can also deplete an area of those who might look after its land.

Ignorance about how to look after drylands to keep them fertile also plays a part in desertification. For instance, during the famous Dust Bowl drought in mid-America in the 1930s, many farmers used ploughs that were better suited to more temperate latitudes, resulting in extensive desertification. The choice of policies and technologies can be vital in keeping drylands productive.

Impacts and Issues

The United Nations says that 250 million people are directly affected by desertification and another one billion people in over one hundred countries are at risk. These include many of the world’s poorest. A 2007 report from the UN suggested that if urgent action against desertification is not taken, 50 million people in sub-Saharan Africa and central Asia could be displaced within the next ten years. People in drylands, the majority of which are in developing countries, are more dependent on the surrounding systems for basic needs such as water, food, and wood for building than are those in ecosystems elsewhere. Africa is the place worst affected by desertification, but there are many others. For instance, the Soviet Union created a large area of desertification in Central Asia through overfarming. Northern China, Australia, northeastern Brazil, and the Caribbean islands have also experienced desertification through overgrazing and deforestation.

The impact of desertification on a population includes crop damage, damage to water supplies, habitat loss, loss of biodiversity, displacement of the local population, poverty, famine, and disease. Sometimes people affected by desertification will make the problem worse by trying to plant or graze neighboring dry areas. If they migrate, instead, to cities or other countries, social unrest and political instability often result.

In 1977 the United Nations Conference on Desertification set up a Plan of Action in recognition of the problem. But by 1991, little had been achieved, except for some local successes. At the time of the United Nations Conference on Environment and

WORDS TO KNOW

DRYLAND: Land where freshwater supplies are limited.

OVERGRAZING: The grazing of land over extended periods of time or without sufficient recovery periods, to the detriment of vegetation and soil quality.

SOIL: Unconsolidated materials above bedrock.

Development, held in Rio de Janeiro in 1992, a new, integrated approach to the problem of desertification was proposed. The United Nations Convention to Combat Desertification was adopted in 1994, and it has now been signed by 191 countries around the world.

The convention’s work covers different geographical locations, namely Africa, Asia, Latin America and the Caribbean, northern Mediterranean, and central and eastern Europe. Projects are carried out at a national and regional level, bringing together government, non-governmental organizations, and the local community. The work has to recognize the complex political and economic factors that sometimes drive desertification; progress is stepwise, with the aim of promoting sustainable practices in those places at risk.

IN CONTEXT: GLOBAL EFFORTS TO COMBAT DESERTIFICATION

The first major international plan to prevent desertification and facilitate water conservation work by national governments and international conservation agencies was formulated by the United Nations in 1977 as the U.N. Plan of Action to Combat Desertification. Conference participants noted that issues of desertification, soil and freshwater salination, water shortages, agricultural land degradation, and political and economic turmoil often compound each other.

In June 1994, the Convention to Combat Desertification was adopted. Nearly 180 signatory parties met two years later at the first Conference of the Parties.

Local and national conditions vary, and the most appropriate solution will depend upon location. But there are three basic approaches to tackling desertification. Prevention is the most cost-effective of these. Where the earliest signs of desertification are noted, the local community and government should work together on introducing alternative farming methods or even alternatives to farming or cash crops to generate income in that area. It may also be possible to stop, or even reverse, desertification already underway by rehabilitating or restoring the land. Tree planting is one possible strategy and this is being done in China and elsewhere. However, trees need water to grow and care has to be taken not to deplete already precious supplies.

Desertification is likely to increase in the future because the underlying factors driving it are so complex and can only be tackled step by step. It is related to biodiversity loss and climate change in ways that are not yet fully understood. Loss of biodiversity in a dryland, particularly when it involves plants, can alter water regulation and local climate. This, in turn, may make desertification worse. The relationship between climat change and desertification is complex. Although warmer temperatures encourage drier conditions, increased carbon dioxide in the atmosphere may actually encourage plant growth. Desertification is one of the largest environmental challenges we face. Unless it is seriously addressed, it will be impossible to alleviate poverty among those who go without life’s basic needs.

BIBLIOGRAPHY

Books

Cunningham, W.P., and A. Cunningham. Environmental Science: A Global Concern. New York: McGraw-Hill International Edition, 2008.

Kaufmann R., and C. Cleveland. Environmental Science. New York: McGraw-Hill International Edition, 2008.

Web Sites

Green Facts. “Desertification: Scientific Facts on Desertification.” January 23, 2008. http://www.greenfacts.org/en/desertification/index.htm (accessed February 27, 2008).

Oasis. “What Is Desertification?” http://www.oasisglobal.net/what_is.htm (accessed February 26, 2008).

United Nations. “Rethinking Policies to Cope with Desertification.” June 28, 2007. http://news.bbc.co.uk/2/shared/bsp/hi/pdfs/28_06_07unreportdesert.pdf (accessed February 27, 2008).

United Nations Convention to Combat Desertification. “Explanatory Leaflet.” http://www.unccd.int/convention/text/leaflet.php (accessed February 26, 2008).

Susan Aldridge

Environmental Science: In Context