What happens when climate variations and human actions such as land clearing, urbanization and unsustainable agricultural habits mix? The combination results in an ecological crisis: land degradation. When land degrades, it can no longer properly absorb, store and recycle water, nutrients and energy. Land degradation in arid, semi-arid and dry, subhumid areas (drylands) is called desertification.
Seventy percent of drylands worldwide are degraded, and one-third of the world's land surfaces are threatened -- lands become more prone to flooding, wind damage and erosion, the quality of soil becomes poor, and productivity plummets [sources: UNCCD, UNESCO]. Areas affected by desertification are faced with not only environmental consequences but also economic effects. The World Bank estimates areas affected by desertification lose income greater than $40 billion annually [source: UNESCO].
In dryland areas, soil is fragile, vegetation is thin and the climate is merciless. Drylands cover more than 40 percent of our planet, and their susceptibility to desertification puts more than 1 billion people at risk for poverty and starvation [source: USDA].
While you may think this problem affects only areas we consider hot and arid, such as Southern Africa, desertification affects every continent except Antarctica. And the United States isn't immune to this crisis. Data from the last 30 years indicates the American Southwest is getting warmer and drier. Could the continental U.S. become a desert within the next 50 years? Let's look at how the stresses on our ecosystem -- brought on both by humans and nature -- are dramatically changing our landscape.
While deserts expand and contract naturally, it's important to understand that desertification is different from this natural cycle. Desertification is also far from being a new global crisis: Ancient empires, including Sumeria, Babylon and Rome, were dealt its debilitating effects. Unfortunately, there is no one reason we can point to as the cause of desertification, but rather a combination of climate and our own mistakes, ignorance and actions.
Desertification is triggered mainly by the overuse of land and unsustainable agricultural practices (overcropping, overgrazing, poor irrigation and deforestation) which lead to a loss of natural vegetation and healthy soil. An expanding human population and urban living area as well as the low level of priority placed on environmental protection efforts also contributes.
Currently, the most endangered regions are near the world's five main deserts, including the Sonoran Desert which lies in Northwest Mexico and the Southwest United States; the Atacama Desert in South America; the Kalahari Desert in Southern Africa; most of Australia; and the large desert mass made up by the Sahara, Arabian, Great Indian, Taklimakan, Gobi and the deserts of Iran and the former Soviet Union.
But areas not on this list are still of concern. For example, desertification is a looming crisis in Africa where almost 70 percent of the continent is arid or semi-arid land. More than 30 percent of North America is comprised of arid or semi-arid lands, with about 40 percent of the continental United States at risk for desertification [source: U.N.].
Seventeen states in the Western U.S. can be categorized as arid, semi-arid or dry subhumid based on climate and soil type; this characterizes them as vulnerable to desertification. The most severely affected areas in the U.S. are in New Mexico, Texas and on the Navajo Indian reservation in New Mexico and Arizona. Overgrazing, which has led to wind and water erosion, and poor irrigation are the leading causes of desertification in the U.S., and scientists believe it's unlikely these areas will mend naturally from the damage in the next 100 years.
With the establishment of the Soil Conservation Service after the damaging 1930s dust bowl, the U.S. recognized desertification as a national problem and the government began providing financial support and resources to put appropriate agricultural practices into place. Together, state and federal agencies and nongovernment organizations work with private ranchers, farmers and developers on technologies that help reduce soil loss, improve irrigation and draw on renewable energy sources.
Land health in the U.S. is an ongoing and considerable ecological problem. In 2007, scientists noted the disappearance of green oases that used to dot the desert landscape as well as an increase in temperature and drought in the Southwest.
For more information about climate, climate change and efforts to combat desertification, visit our resources on the following page.
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- Brill, Kenneth C. "The U.S. Commitment to Combating Desertification." U.S. Department of State. 2001. http://www.state.gov/g/oes/rls/rm/4005.htm
- Bryner, Jeanne. "Why the 1930s Dust Bowl Was So Bad." LiveScience. 2008. http://www.livescience.com/environment/080505-dust-bowl.html
- "Desertification." U.S. Geological Survey. 1997. http://pubs.usgs.gov/gip/deserts/desertification/
- "Desertification: Scientific Facts on Desertification." GreenFacts. http://www.greenfacts.org/en/desertification/
- "Did Dust Storms make 1930s Dust Bowl Drought Worse?" ScienceDaily. 2008. http://www.sciencedaily.com/releases/2008/04/080430152030.htm
- Dregne, H.E. "Desertification of Arid Lands." Center for International Earth Science Information Network. Columbia University. http://www.ciesin.org/docs/002-193/002-193.html
- Egan, Timothy. "Heat Invades Cool Heights Over Arizona Desert." The New York Times. 2008. http://www.nytimes.com/2007/03/27/us/27warming.html
- "Facts and Figures: Desertification and Drought." United Nations Educational, Scientific, and Cultural Organization (UNESCO). 2003. http://www.wateryear2003.org/en/ev.php-URL_ID=5137&URL_DO=DO_TOPIC&URL_SECTION=201.html
- Ford, Matt. "Desertification: How to stop the shifting sands." CNN. 2008. http://edition.cnn.com/2008/WORLD/asiapcf/04/25/es.desertification/index.html
- "Human Induced Land Degradation is Preventable Through Understanding and Remediation and the Underlying Causes." Natural Resources Conservation Service. U.S. Department of Agriculture. http://soils.usda.gov/use/worldsoils/landdeg/degradation.html
- "National Report on Efforts to Mitigate Desertification in the Western United States." United Nations Convention to Combat Desertification (UNCCD). 2006. http://www.unccd.int/cop/reports/otheraffected/national/2006/united_states_of_america-eng.pdf
- "The causes of desertification." United Nations Convention to Combat Desertification (UNCCD). 2008. http://www.unccd.int/publicinfo/factsheets/showFS.php?number=2
- "The Sand Lands." FOCUS. United Nations Convention to Combat Desertification (UNCCD). 2006. http://www.ausaid.gov.au/publications/focus/may06/focus_may06_15.pdf
- "The United Nations Convention to Combat Desertification: A New Response to an Age-Old Problem." United Nations. 1997. http://www.un.org/ecosocdev/geninfo/sustdev/desert.htm