How Desertification Works


Drought and desertification in the Great Plains states in the 1920s forced many farmers to move from the Dust Bowl to more fertile ground.
Drought and desertification in the Great Plains states in the 1920s forced many farmers to move from the Dust Bowl to more fertile ground.
Alfred Eisenstaedt/Time & Life Pictures/­Getty Images

In the 1920s, the United States en­tered an economic recession. Farmers in Western states tried to raise profits by plowing and planting more acreage with new mechanized farming methods.

Within a decade, a massive drought hit the entire country. Strong winds swept across the Great Plains, stirring up loose topsoil that had been displaced by overplowing and overgrazing of cattle. The results were dozens of epic dust storms that swallowed whole cities in blinding black clouds. The semiarid soil of the plains, which had fed generations with its fertile soil, was now a lifeless desert known as the Dust Bowl.

Advertisement

­The Dust Bowl is a perfect example of desertification, the degradation of dryland ecosystems through a combination of natural and human causes. Droughts are an unavoidable occurrence in semi-arid regions like the Western United States, large portions of sub-Saharan Africa, Central Asia and Latin America. But over the millennia, these fragile ecosystems have discovered ways to survive.

The real problem is when human beings try to take too many resources from land that can sustain very little human life. When we talk about desertification, we're not only talking about the slow spread of existing deserts, but the creation of entirely new ones. When too many people try to plant crops, graze cattle and harvest firewood in a fragile dryland ecosystem, they tip the balance of sustainability.

The result is that new deserts are growing at a rate of 20,000 square miles (51,800 square kilometers) a year [source: Steele]. Nearly half of the world's total land mass is composed of dryland ecosystems, areas defined by low annual rainfall and high temperatures. It's estimated that 10 to 20 percent of these regions are already degraded -- unsuitable for human, animal or plant life [source: GreenFacts.org].

Dryland regions are also home to billions of the world's poorest, most marginalized populations. Desertification leads to famine, mass starvation and unprecedented human migration. As people are displaced by new deserts, they are forced into even more unstable regions, where the desertification process continues.

­Desertification is one of the world's most pressing environmental issues, but it's not irreversible. Decades after the Dust Bowl, federal conservation programs were able to restore the Great Plains to fertility. Keep reading to learn more about the causes and effects of desertification as well as the best methods for bringing it to a halt.

What Causes Desertification?

Beijing Image Gallery Workers in Beijing cover piles of sand before the 2008 Summer Olympic Games in an attempt to improve air quality. The sand blew in from desertified areas north and northwest China. See more pictures of Beijing.
China Photos/­Getty Images

­A balanced ecosystem is a healthy ecosystem. In a healthy dryland ecosystem, relatively few animals and humans attempt to survive on the limited resources of the land, which include water, fertile soil and trees. Since rainfall is infrequent in semiarid regions, the land is not built to support huge fields of crops or supply grazing land for hundreds of thousands of cattle.

The root cause of desertification is poor soil conservation leading to soil degradation. Healthy, productive soil is rich with organic matter called humus [source: Ball]. Humus is formed when decaying organic materials like dead plants and animals are transformed by micro-organisms and fungi into soil that's rich in essential nutrients like carbon, nitrogen, phosphorous and sulfur [source: International Institute for Sustainable Development].

Advertisement

Unsustainable farming methods also contribute to soil degradation. Crop rotation, heavy composting and responsible use of chemical fertilizer ensure that the soil has enough organic imput to support vibrant micro-organisms. On the other hand, overuse of chemical fertilizers, failure to employ crop rotation and irresponsible irrigation practices rob the soil of the last of its nutrients. When topsoil is depleted of humus, it's either too loose or too compacted, both of which can lead to destructive erosion.

All life depends on the quality and fertility of the soil. Plants can't grow when soil is allowed to degrade. This means no food crops for humans and no grazing crops for animals. All the rain in the world won't help infertile topsoil. It will only wash away.

Perhaps the greatest cause of soil degradation and desertification is an explosion in world population, particularly in developing countries. Throughout the 1990s, dryland regions experienced a population growth of 18.5 percent, mostly in desperately poor, developing nations [source: GreenFacts.org]. In their daily struggle to survive, these expanding populations have put a deadly strain on their environment.

Grazing animals are just as bad. Grasses are essential to anchoring arid topsoil in a dryland region. When animals are allowed to graze recklessly, they remove all of the native grasses, exposing the topsoil to destructive erosion forces like winds and sudden thunderstorms.

Firewood is the fuel of choice for many people living in developing countries. This has led to unchecked clear-cutting of forests in dryland ecosystems. Trees play a crucial role in anchoring down topsoil and slowing down the force of winds. When too many trees are removed, windstorms and dust storms ensue.

Human activities also exacerbate the biggest problem of living in a dryland region: lack of rainfall. When land is cleared of plant life, either from overgrazing or logging, the bare surface of the Earth reflects more of the sun's light back into the atmosphere, creating even hotter temperatures. In semiarid regions, higher temperatures cause a higher rate of evaporation, which means even less rainfall. Also, all of the dust kicked up by cattle and the smoke created by wildfires introduces heavy particles into the atmosphere that make it more difficult for rain drops to form [source: Socioeconomic Data and Applications Center].

Even political conflicts and war contribute to desertification. When war refugees flee from invading armies, they move en masse into some of the most marginal ecosystems in the world. They bring with them their native farming grazing practices, which can be highly unsuitable for their new home.

­In the next section, we'll talk in depth about who is most affected by desertification.

Who is Affected by Desertification?

A nurse examines a malnourished child in Niger. Desertification contributes to the country's food shortages .
A nurse examines a malnourished child in Niger. Desertification contributes to the country's food shortages .
Issouf Sanogo/AFP/­Getty Images

­An overwhelming 90 percent of the people who live in dryland ecosystems -- those areas most prone to soil degradation and desertification -- are citizens of developing countries. This adds up to 2 billion people, mostly poor and marginalized, who are immediately affected by the deadly consequences of desertification [source: GreenFacts.org].

Experts estimate that more than 24,000 people die every day from starvation [source: The Hunger Site]. The worst sufferers are populations living in the dryland regions of sub-Saharan Africa and Central Asia. It's estimated than more than 70 percent of drylands in Africa, Asia and Latin America that are being used for agricultural purposes are already experiencing the effects of desertification [source: PeopleandPlanet.net]. The infant mortality rate in a dryland developing country is 10 times the rate of an industrialized nation [source: GreenFacts.org].

Advertisement

When experts talk about the causes and effects of desertification, they talk a lot about ecosystem services, the resources that an environment offers to its inhabitants. People living in marginal dryland regions depend much more heavily on their local ecosystem services than people in developing countries [source: GreenFacts.org].

In the United States, for example, much of the food we eat and fuel we use comes from other regions or even other countries. In a country like Burkina Faso in sub-Saharan Africa, everything comes from the immediate surrounding area. There is no money or infrastructure to import food and fuel. So when the local conditions worsen through soil degradation and desertification, the impact on the lives of the people is far more severe.

The only way to avoid starvation is to move to another area that hasn't been entirely degraded yet. This continuous mass migration of people into fragile regions speeds up the desertification process exponentially.

But the effects of desertification are also felt by millions of people living far from the immediate dryland zones. One effect is the mass migration of people from rural areas to already overpopulated cities. This contributes to sprawling slums that are breeding grounds for disease. It's estimated that 50 million people will be displaced by desertification in the next decade [source: PeopleandPlanet.net].

Dust storms from the Gobi desert in China create poor air conditions in Beijing, and the dust fallout from larger storms has been detected as far away as North America [source: NASA]. Dust storms have been proven to trigger allergic reactions and asthma attacks and have a particularly negative health impact on children and the elderly [source: NSW Department of Health].

The larger effects of desertification can be felt on a global level. Investigations into the cause of the global food crisis of 2008 point to desertification as one of its sources [source: UN News Centre]. Degradation of available farmland contributes to less food production and higher prices for staple crops like rice, wheat and corn. In March 2008, the price of wheat was up 130 percent from a year before and the price of soy was up 87 percent [source: BBC News]. For those countries that can't produce their own food due to soil degradation, they can no longer afford to import.

Now that we understand the scope of the desertification crisis, we'll explore what steps can be taken to stop and even reverse the deadly trend.

Can Desertification be Stopped?

Chinese students plant trees north of Beijing as part of a project to prevent desertification.
Chinese students plant trees north of Beijing as part of a project to prevent desertification.
Adrian Bradshaw/­Getty Images

­Is it possible to slow the progress of desertification or even stop it completely? Environmental experts say yes, but it will require a worldwide campaign to improve agricultural methods, regenerate plant life and conserve precious soil fertility.

The first step is to replace destructive agricultural techniques at the grassroots level. Poor farming communities in developing countries need to be taught the long-term benefits of crop rotation, the use of legumes and other cover crops to "fix" nitrogen back into the soil, sustainable irrigation methods, and techniques like terracing, which prevent water runoff and erosion in hilly, sloping landscapes [source: Ford and GreenFacts.org].

Advertisement

Planting millions of trees in strategic locations could do wonders for halting the expansion of current deserts and preventing the creation of new ones. The Chinese government is currently planting a nearly 3,000-mile-long (4,828-kilometer-long) belt of trees along the edge of the Gobi desert to put the brakes on dust storms and prevent dune migration. A similar "green wall" is being considered along the frontier of the Sahara [source: Ford]. On a smaller scale, simply planting trees around fields will cut winds that contribute to erosion of topsoil.

The most effective solutions to desertification are surprisingly low-tech. Researchers at a German university have developed a rehabilitation technique that relies on recycled coffee sacks. The sacks are filled with compost, seeds and a material that acts like a sponge, soaking up and holding rainwater for extended periods of time. The sacks can be dropped across the surface of a degraded dryland. Over time, as the sacks decompose and become drenched with rainwater, the seeds take root and spread out, fed by the rich compost [source: Deutsche Welle].

Some experts are finding that traditional agriculture and land management techniques are much more in tune with the fragile dryland habitat than modern methods. In Spain, for example, a British company has been successfully renovating 1,000-year-old Moorish irrigation systems [source: Ford].

There's also a consensus that dryland communities need to develop alternative livelihoods besides subsistence farming and grazing. A recent report co-authored by researchers at the United Nations University found that communities in Pakistan found success using a technique called arid aquaculture. With this method, communities can breed certain kinds of fish and even grow certain vegetables in very salty (briny) ponds [source: United Nations University]. The report also recommended the development of dryland tourist destinations and the production of soaps and other handicrafts based on native herbs, oils and wools.

To learn more about important environmental issues and green science, follow the links on the next page.

Related HowStuffWorks Articles

More Great Links

Sources

  • Ball, Liz. Horticulture Update. "Humus: It's the Dirt." July/August 2001http://aggie-horticulture.tamu.edu/extension/newsletters/hortupdate/julaug01/art3jul.html­
  • BBC News. "The Cost of Food: Facts & Figures." Oct. 16, 2008http://news.bbc.co.uk/2/hi/7284196.stm
  • Business Mirror Online. "Combating desertification is key to tackling global food crisis." Nov. 9, 2008.http://businessmirror.com.ph/index.php?option=com_content&view=article&catid=44:science&id=1664:combating-desertification-is-key-to-tackling-global-food-crisis
  • Deutsche Welle. "Coffee Sacks Stop Desertification"http://www.dw-world.de/dw/article/0,2144,1920523,00.html
  • Ford, Matt. CNN. "Desertification: How to stop the shifting sands." April 27, 2008.http://edition.cnn.com/2008/WORLD/asiapcf/04/25/es.desertification/index.html
  • GreenFacts.org. "Scientific Facts on Desertification."http://www.greenfacts.org/en/desertification/index.htm
  • The Hunger Site. "About The Hunger Site"http://www.thehungersite.com/clickToGive/home.faces?siteId=1
  • International Institute of Sustainable Development. "On the Great Plains: Degradation of Prairie Soil Resources."http://www.iisd.org/agri/GPsoil.htm
  • NASA. "The Pacific Dust Express." May 17, 2001http://science.nasa.gov/headlines/y2001/ast17may_1.htm
  • New South Wales Department of Health. "NSW Health Factsheet: Dust Storms." Nov. 1, 2003http://www.health.nsw.gov.au/factsheets/environmental/dust_storms.html
  • PeopleandPlanet.net. "Desertification and degraded land."http://www.peopleandplanet.net/doc.php?id=348
  • SocioeconomicData and Applications Center (SEDAC) at Columbia University. "The Causes of Land Degradation and Desertification."http://sedac.ciesin.columbia.edu/tg/guide_glue.jsp?rd=lu&ds=4.1
  • Steele, Giselle V. E: The Environmental Magazine. "Drowning in sand: environmental effects of desertification." January-February 1997.http://findarticles.com/p/articles/mi_m1594/is_n1_v8/ai_19192501
  • UN News Centre. "Global food crisis could have been avoided - UN development experts." May 6, 2008http://www.un.org/apps/news/story.asp?NewsID=26578&Cr=food&Cr1=crisis
  • United Nations University. "'Arid aquaculture' among livelihoods promoted to relieve worsening pressure on world's drylands." Nov. 11, 2008http://www.eurekalert.org/pub_releases/2008-11/unu-aa110308.php­