The term desertification itself is somewhat misleading. Desertification does not refer to the spread of existing deserts, which naturally expand and shrink with fluctuations in rainfall. Rather it describes what results when people overuse or misuse dry, semi-arid and dry sub-humid lands. Climate variations, especially drought, often hasten the process. In just a few seasons, precious topsoil that has built up over centuries can blow or wash away. The Worldwatch Institute estimates that the earth's landmasses are losing as much as 24 billion [thousand million] tons of topsoil every year.

The natural and social consequences of desertification can be devastating. It may take centuries for topsoil to rebuild or forests to regrow. And if the damage is too severe, the land may not recover. In addition, when aggravated by drought, desertification can lead to widespread famine, displacement of people from their homes, and social unrest and conflict. It is a pattern repeated throughout history, as author Alan Grainger has noted in his book Desertification: "When soil fertility was not replenished or the soil was allowed to deteriorate, civilizations either declined or colonized other areas. It is no coincidence that many ruins of great temples and palaces are today found amid sandy wastelands."

But out of this catastrophe came the first global attempt -- and the first legally binding global treaty -- to stem desertification. The Convention to Combat Desertification (CCD), a United Nations treaty that came into effect in 1996, broke new ground by stressing partnership among countries rich and poor, and between national governments and the local people most affected by the problem. It represents the best hope yet for stopping the march of desertification, which already threatens some 30 percent of the land on earth.

The Disappearing Land

Desertification certainly is not new. As early as 2000 B.C., the Sumerians described land that turned to desert after all the trees were cut. In the fourth century B.C., Plato complained of land that "compared to what it was, is like the skeleton of a body wasted by disease." Today, on an increasingly crowded planet, desertification reaches most corners of the globe.

According to United Nations' statistics, the impact is staggering:

More than 250 million of the earth's inhabitants are directly affected by desertification; 135 million are in danger of being driven from their land. The livelihoods of one billion people -- nearly one-fifth of the world's population -- are at risk.

Unsustainable farming practices -- activities that deplete the land faster than it can recover -- are the main culprits behind desertification. Overcultivation, for example, exhausts the soil by robbing it of nutrients. Overgrazing by livestock destroys vegetation that protects topsoil from erosion and compacts the land so that it cannot retain moisture. Leveling forests for fuel wood or to clear land for unsuitable farming removes trees that bind the soil to land. Poorly drained irrigation turns land salty, leaving it worthless for growing crops. The United Nations likens the process to a disease on the planet with patches of degraded land erupting separately, then gradually merging to create, in effect, a new wasteland.

A woman carries branches gathered from a forest preserve in Haiti. So much land in Haiti has been cleared for fuel or farming that only one percent is still forested. (AP Photo/Daniel Morel)

A farmer in Senegal coaxes growth on still-functioning dryland. (Photo by Mike McGahuey/USAID)

Specifically, the term desertification refers to degradation in three types of ecosystems, defined as arid, semi-arid, and dry sub-humid. These are lands of limited productivity, easily altered by human activities, that circle the globe.

Although desertification is felt most acutely in the developing countries of Africa, the continent with the highest proportion of dry land affected by the process -- 74 percent -- surprisingly, is North America. More than 30 percent of the land west of the Mississippi River in the United States, as well as portions of the three prairie provinces of Canada, are showing signs of desertification.

The problem is also severe in Asia, where the U.N. estimates that more than 1.2 billion hectares already are distressed. Since the 1950s, in China alone, sand drifts and newly desertified lands have swallowed more than 6 million hectares of forests and shrub lands, 2.32 million hectares of rangeland, and 680,000 hectares of cultivated land. Some 24,000 villages, 30,000 kilometers of highways, and 50,000 kilometers of waterways are relentlessly threatened by sand and dust.

But desertification knows no national boundaries. One-quarter of the Latin America and Caribbean region, for example, is desert and drylands. Even in the cold, humid climate of Iceland, grazing and deforestation have led to severe soil erosion and creation of a 5000-square-kilometer desertified area that is perhaps the largest sandy area in the world outside of arid regions.

Global Impact

Desertification is more than a problem of localities. Desertification can harm the environment and influence weather thousands of kilometers away -- even on the other side of the world. Bare, eroded land floods easily and contributes to silting of rivers, streams, and reservoirs. Thus contaminated water and sediments carried down rivers contribute significantly to pollution of the oceans. Conversely, increasingly unsustainable attempts to irrigate parched land rob rivers of their water and in turn dramatically shrink such large lakes as the Aral Sea and Lake Chad. Giant yellow clouds of dust from storms in China can travel over 13,000 kilometers across the Pacific with the jet stream in the upper atmosphere, causing haze and air pollution alerts on the West Coast of the United States. In one two-week period in April 2001, the Earth Policy Institute tracked a yellow dust cloud that originated with a cyclone in northwestern China and southern Mongolia all the way across North America to the Atlantic Ocean.

Desertification can have a serious impact on the social and political climate as well. In many countries, poverty is the main driving force behind unsustainable farming practices that degrade the land. Poverty forces people to eke as much as possible from the land, even after they recognize signs of damage. When productivity falls, these subsistence farmers face even greater poverty or, worse yet, starvation. At the very least, they are uprooted from their homes, forced to abandon their now-worthless land. By 2020, the United Nations estimates that some 60 million people will be forced to migrate from desertified areas in sub-Saharan Africa toward northern Africa and Europe.

Finding Solutions

The good news is that desertification need not be permanent or inevitable. Solutions range from the simple and traditional, such as rotating crops or terracing sloped fields, to high-tech satellite monitoring of vulnerable areas.

"The difficulty is in maintaining people's economic productivity while you are halting or reversing the desertification process," says Franklin Moore, director of the Office of Environment and Science Policy for the U.S. Agency for International Development (USAID). "Generally, solutions must be accompanied by helping people find another means of economic pursuit."

Indeed, the realization that the people most affected by the problem need to be part of the solution is at the core of the current effort to curb desertification. Horrified by the tragic drought and famine in the Sahel, the international community first tackled the problem on a global level at a U.N.-sponsored Conference on Desertification in Nairobi, Kenya, in 1977. A Plan of Action to Combat Desertification emerged from that conference but soon stalled for lack of government and financial support.

The next major step came in 1992, when world leaders attended the United Nations Conference on Environment and Development, or Earth Summit, in Rio de Janeiro. The "Earth Summit" called on the United Nations to draft a legally binding convention to address desertification. After 13 months of negotiations, the United Nations Convention to Combat Desertification was adopted in Paris on June 17, 1994, and went into force in December 1996. So far, 191 countries, including the United States, have ratified or acceded to this historic accord.

Part of the solution: Chinese workers plant trees on a terraced slope near Beijing, China. (AP Photo/Xinhua, Wang Chengxuan)

Its stated aim is "to combat desertification and mitigate the effects of drought� particularly in Africa, through effective action at all levels, supported by international cooperation and partnership arrangements . . . ." The Convention divides participants into groups -- developed and developing nations, and "affected" and "not affected" nations. Affected developed nations include the United States, Canada, Australia, and some European countries. Affected developing nations -- those needing assistance to deal with desertification -- include most African nations, as well as China, India, Mexico, Brazil, Chile, Argentina, Mongolia, and the states of Central Asia.

Signing on to the Convention obligates developed nations actively to support and help fund efforts of developing countries, particularly those in Africa. It also obligates affected countries to develop and implement national action programs, paying special attention to the socioeconomic factors that contribute to desertification. Most developed countries already have mechanisms in place to deal with the problem. The United States, for example, tackles the issue at the state level and through the Department of Agriculture's Natural Resources Conservation Service and the Department of the Interior's Bureau of Land Management, which oversees more than 80 million hectares of public lands in the Western regions of the United States.

Ground-breaking Accord

However, the heart of the Convention is its democratic, "bottom-up" approach that stresses partnership rather than assistance. Its first principle stresses that people who bear the brunt of desertification, and who best understand the ecosystems in which they live, must be involved in decisions about how to restore damaged land and prevent further degradation. The Convention highlights "the important role played by women," who in developing countries do much of the work on the land and are often most affected by desertification -- but who may have little voice, even in their own communities.

Unlike previous attempts to combat desertification, the Convention emphasizes the need to go beyond immediate causes, such as overgrazing and deforestation, and tackle the underlying poverty that compels people to act against their own long-term interests.

In addition to providing for local participation, National Action Programs must include long-term strategies for sustainable development, give particular attention to protecting lands not yet degraded, and devise early drought-warning systems. The Convention also specifies voluntary actions, such as developing alternative forms of livelihood "that could provide incomes in drought prone areas."

With some 60 National Action Programs and 10 regional and sub-regional programs in place as of 2004, the tough job of implementing them lies ahead. A Committee for the Review of the Implementation of the Convention oversees progress and fosters the exchange of information and innovative solutions among affected countries.

In addition, as they struggle with desertification, countries need to heed the call to develop parallel national strategies for implementing the CCD and two other closely linked conventions that also grew out of the 1992 Earth Summit -- the Convention on Biological Diversity (CBD) and the United Nations Framework Convention on Climate Change (UNFCCC). Desertification directly threatens the rich diversity of plant and animal life found in dryland ecosystems. Some of the most important global food crops, such as barley and sorghum, originate in dry areas. Dry lands also supply a third of all plant-derived medications, as well as valuable resins, waxes, oils, and other commercial products. The CBD has a program for dry and sub-humid lands that sets out key activities countries can take to protect the biodiversity of these regions.

The connection between desertification and climate change is not yet clear. The practices that lead to desertification, especially widespread burning of trees for fuel and to clear land, can add to the greenhouse gases that contribute to global climate change. On the other hand, reforestation to reclaim degraded land may help to offset climate change through carbon sequestration. Although scientists are not yet sure how such rising levels of greenhouse gases will in turn affect the rate of desertification, they are projected to aggravate the process in certain arid, semi-arid, and dry sub-humid areas. Decreases in rainfall in these areas may result in decreases in soil fertility, agricultural livestock, and forest and rangeland production. Potential increases in the frequency and severity of droughts are likely to exacerbate desertification.

The Convention has focused global attention on the need to combat desertification, as has the U.N.'s designation of June 17 as World Day to Combat Desertification and Drought. Now in its ninth year, the day has generated attention from national leaders, the Pope, and officials of the United Nations. In a message marking the World Day to Combat Desertification 2003, U.N. Secretary General Kofi Annan noted that "fighting desertification must be an integral part of our wider efforts to eradicate poverty and ensure long-term food security." He called on all nations to "recommit ourselves to the goals of the Convention, and to achieving sustainable development for all, including the dryland rural areas where the world's poorest people live."