Desertification is a term used to describe the gradual changes that take place over a region or area of land that ultimately result in the formation of a desert.
Although many places in the world are called deserts, scientists usually define a desert as a region or area that receives less than 10 inches (25.4 centimeters) of water from precipitation (rain, slow, sleet, or hail) during a year.
Desertification harms many people. During the late 1960s and early 1970s, desertification brought on by a severe drought (an extended period with little or no rain) in the Sahel region of Africa devastated the local agriculture of six African countries located on the southern border of the Sahara Desert.
International relief measures were unable to prevent the death of thousands of people who suffered from the resulting famine (lack of food). Millions of animals that normally relied upon eating the grass that grew in the already dry region also died. The deaths of the animals resulted in further starvation of the people living in the region.
Dry areas of North America—particularly in the southwestern and western United States—are also vulnerable to desertification. Some scientists estimate that up to nine out of ten such areas can be described as undergoing some form of desertification.
How desertification changes the environment
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As the process of desertification takes place, the land loses its ability to support agriculture. Areas that were once arid (dry), but that could still support the growth of some crops or the grazing of animals, become barren as the desertification progresses. For example, grasslands may undergo desertification to become deserts.
During desertification, an area undergoes many changes, but it does not lose its ability to support crops or animals all at once. Neither does it completely lose its ability to support life. Even a desert can support the sparse growth of vegetation that live in areas with little moisture.
As desertification proceeds, however, the land gradually loses its ability to support plants that require higher levels of water, and only plants that are able to live and thrive on less water survive.
The loss of water also changes the way the land responds to wind and occasional rains. Over time, desertification results in changes to the landscape that result in the formation of areas of high erosion (areas where soil and rock are lost or worn away by water) and the formation of dramatic land features (such as flat-topped mesas or buttes).
As desertification continues, the topsoil (uppermost layer of soil) dries and becomes lighter. It is easily blown away by the wind is and the remaining sand or soil may form dunes (hills of sand created by wind).
The wind over the region or area then shapes the dunes in very specific ways. For example, scientists can look at the pattern of dunes and tell how the winds blow throughout the year.
The loss of water over time also changes the chemistry of the land. As the land becomes drier, the concentration of salt increases in the water that does remain. If the concentration of salt become too high (a process termed salinization), the remaining water can become too salty for humans to drink or use for watering crops.
Causes of desertification
In addition to a decline in the amount of rain that falls each year, a number of other factors are important in determining whether a region or area will undergo desertification. Factors such as wind, amount of sunlight, and use of the land also influence how fast desertification takes place.
Desertification can be caused or reversed by natural forces and cycles in the climate such as rainfall and wind patterns. For example, rainshadow deserts may form in area with little precipitation because a barrier such as a mountain range causes moisture-rich winds to lose their moisture before reaching the area.
Improper use or overuse of water resources by humans can also cause desertification. If, for example, humans overuse water to water lawns, not enough water may remain available in local groundwater or aquifers support surrounding areas needing water to grow grasses that support cattle and other grazing animals.
In addition, if too many animals are introduced into an area, they can overgraze by eating too much of the available vegetation. The loss of too much natural grass and vegetation can speed up the processes of land erosion, which will speed up the process of and desertification.
Other human activities such as deforestation (the over-cutting of trees) and mining may cause desertification. The introduction of new species of plants and animals not native (naturally occurring) to a region or area—especially plants or animals that may require more water than the native species already living in the area—may result in desertification.
Under the right conditions, if the use of land is carefully regulated and special practices are started to conserve water, desertification can be greatly slowed or even reversed. In this way, water conservation helps keep lands productive.
In many dry regions, water conservation practices are new to the societies that live there and it remains the custom to simply abandon dry lands in search of areas with more water available to support crops and animals.
As the world’s population increases, however, this practice cannot continue indefinitely, and water conservation practices have become increasingly important.
Desertification can also be reversed by natural forces and cycles in the climate.