erosion at Flaming Mountains in China The world's great deserts were formed by natural processes interacting over long intervals of time. During most of these times, deserts have grown and shrunk independent of human activities. Paleodeserts, large sand seas now inactive because they are stabilized by vegetation, extend well beyond the present margins of core deserts, such as the Sahara. In some regions, deserts are separated sharply from surrounding, less arid areas by mountains and other contrasting landforms that reflect basic structural differences in the regional geology. In other areas, desert fringes form a gradual transition from a dry to a more humid environment, making it more difficult to define the desert border. [Sources: “Deserts: Geology and Resources” by A.S. Walker, United States Geological Survey]
These transition zones have very fragile, delicately balanced ecosystems. Desert fringes often are a mosaic of microclimates. Small hollows support vegetation that picks up heat from the hot winds and protects the land from the prevailing winds. After rainfall the vegetated areas are distinctly cooler than the surroundings. In these marginal areas, human activity may stress the ecosystem beyond its tolerance limit, resulting in degradation of the land. By pounding the soil with their hooves, livestock compact the substrate, increase the proportion of fine material, and reduce the percolation rate of the soil, thus encouraging erosion by wind and water. Grazing and the collection of firewood reduces or eliminates plants that help to bind the soil.
Disturbances of the desert can have dire long term environmental consequences. The top soil is very fragile, like an eggshell. If it is disturbed plants have a hard time to regain growth. Sometimes they never come back.
Websites and Resources on Deserts: United States Geological Survey usgs.gov/gip/deserts ; Desert USA (good info on the world’s deserts); desertusa.com/life ; United Nations Global Desert Outlook unep.org/geo/gdoutlook ; Desert Biome article, University of California, Berkeley Desert Biome ; Blue Planet Biomes (about U.S. deserts) blueplanetbiomes.org ; Wikipedia article Wikipedia ;National Geographic online article National Geographic Oxfam Cool Planet oxfam.org.uk/coolplanet ; Sand Dunes article waynesword.palomar.edu ; United States Geological Survey usgs.gov/gip/deserts
Erosion and Salinization
Logging, overgrazing and poor land use cause erosion which in turn causes lakes and rivers to silt up, arable land to be eaten away, and flooding to increase because vegetation that catches rainwater and slows its flow into rivers is gone.
Soil erosion is common on China's crop land that is not irrigated. The Yellow River--which drains much of Northern China-- derives its name from the 1.6 billion tons of eroded, ocher-colored topsoil that it annually transports to the ocean.
Waterlogging and salinization affect 23 percent of the irrigated land in China and significantly reduce production on an estimated 15 percent of China's irrigated land. An estimated 6 million acres of land has been damaged by salt.
Desertification describes the degradation of formerly productive land. It is a complex process. It involves multiple causes, and it proceeds at varying rates in different climates. Desertification may intensify a general climatic trend toward greater aridity, or it may initiate a change in local climate. [Sources: “Deserts: Geology and Resources” by A.S. Walker, United States Geological Survey]
Desertification does not occur in linear, easily mappable patterns. Deserts advance erratically, forming patches on their borders. Areas far from natural deserts can degrade quickly to barren soil, rock, or sand through poor land management. The presence of a nearby desert has no direct relationship to desertification. Unfortunately, an area undergoing desertification is brought to public attention only after the process is well underway. Often little or no data are available to indicate the previous state of the ecosystem or the rate of degradation. Scientists still question whether desertification, as a process of global change, is permanent or how and when it can be halted or reversed.
Desertification became well known in the 1930's, when parts of the Great Plains in the United States turned into the "Dust Bowl" as a result of drought and poor practices in farming, although the term itself was not used until almost 1950. During the dust bowl period, millions of people were forced to abandon their farms and livelihoods. Greatly improved methods of agriculture and land and water management in the Great Plains have prevented that disaster from recurring, but desertification presently affects millions of people in almost every continent.
An area of Inner Mongolia before desertification
Desertification in China
About 28 percent of China is covered by desert and that amount of desert in China is getting larger every year. Deserts are being created faster in China than anywhere else in the world, with old deserts expanding and new deserts being formed. The rate of desertification nationwide is around 900 square miles a year, an area nearly the size of Rhode Island, with an area the size of New Jersey becoming desert every five years. The situation is improving though . About 3,400 square kilometers per year was lost in the 1990s. The rate slowed to 1,300 square kilometers per year in the 2002.
Desertification is caused primarily by human activities Poor land use and overgrazing are causing large areas of grasslands north of Beijing and in Inner Mongolia and Qinghai province to turn into a desert. One man who lived in a village on the eastern edge of the Qinghai-Tibet plateau that was being swallowed up by sand told the New York Times, "The pasture here used to be so green and rich. But now the grass is disappearing and the sand is coming.”
In western China the huge Taklimakan and Kumtag deserts are expanding at such a high rate they are expected to merge in the not too distant future. Two deserts in Inner Mongolia and Gansu Province are also in the process of reaching each other and merging. The Gobi grew by 52,400 square kilometers (20,000 square miles), an area half the size of Pennsylvania, between 1994 and 1999, and continues to advance at a rate of two miles a year and is now only 240 kilometers or so from Beijing.
The Chengdu plain, one of China’s primary grain-growing areas, is threatened by sands from the Ruoergai grasslands. The grasslands were a rich grazing areas until a few decades ago when cows and goats began to multiply and overgraze the land. There is danger that a dust bowl situation could develop. Already wells have dried up and emergency grain supplies have to be brought in to keep people from starving. Many people are being encouraged to move to more hospitable lands.
The grassland has been likened to the thin skin on a bun. It can be destroyed if a couple of centimeters is disturbed. One Mongolian said, “Our leaders used to say we should never cultivate the grassland.” Greenpeace argues that grass seeding and stricter land management are the best way to reclaim the land.
Causes of Desertification
Increased population and livestock pressure on marginal lands has accelerated desertification. In some areas, nomads moving to less arid areas disrupt the local ecosystem and increase the rate of erosion of the land. Nomads are trying to escape the desert, but because of their land-use practices, they are bringing the desert with them.
Causes of desertification include: 1) agricultural practices that induce salinization or waterlogging; 2) overgrazing by livestock; 3) poor mining practices; 4) overpumping of groundwater; 5) urbanization and population pressures; 5) poor fire management; 6) excessive firewood cutting; 7) poor land management. Poverty and overpopulation often fuel desertification.
It is a misconception that droughts cause desertification. Droughts are common in arid and semiarid lands. Well-managed lands can recover from drought when the rains return. Continued land abuse during droughts, however, increases land degradation. By 1973, the drought that began in 1968 in the Sahel of West Africa and the land-use practices there had caused the deaths of more than 100,000 people and 12 million cattle, as well as the disruption of social organizations from villages to the national level. Camels and other animals at a water hole in Chad
An area of Inner Mongolia after desertification
Causes of Desertification in China
The main causes of desertification are overgrazing, overplanting , overplowing and raising crops in regions too dry for crops. These problems in turn are result of population pressures on marginal land. The problem is somewhat analogous to what happens in areas that have been deforested. Once an area is degraded people move onto a new area and degrade that while the old area takes decades to recover or never does. Dr. Sing Yuqin of Beijing University told the New York Times, "Once the process gets started it tends to expand exponentially. And the people are pushed into a poverty trap from which it's hard to escape."
One of the main culprits of the desertification in the Mao era was Mao's plan to raise grain in areas where grain didn't grow well, such as Inner Mongolia. This deprived the land of grass which prevented soil being blown away by the fierce winds that ravage this region.
Some believe that desertification has been caused by climate changes. Scientist in Qinghai have recorded higher temperatures, lower rainfall and stronger winds since the 1950s. Persistent drought robs the soil of moisture and makes it easer for the soil to be picked up and carried away by wind.
Overgrazing by cashmere goats
Overgrazing, Overplanting and Desertification in China
Desertification in China is caused largely by overgrazing. Huge flocks of sheep and goats strip the land of vegetation. In Xillinggol Prefecture in Inner Mongolia, for example, the livestock population increased from 2 million in 1977 to 18 million in 2000, turning one third of the grassland area to desert. Unless something is done the entire prefecture could be uninhabitable by 2020.
Overgrazing is exacerbated by a sociological phenomena called "the tragedy of the common." People share land but raise animals for themselves and try to enrich themselves by raising as many as they can. This leads to more animals than the land can support. One grassland in Qinghai that can support 3.7 million sheep had 5.5 million sheep in 1997
Animals remove the vegetation and winds finished the job by blowing away the top soil, transforming grasslands into desert. When a herder was asked why he was grazing goats next to a sign that said “Protect vegetation, no grazing,” he said, “The lands are too infertile to grow crops — herding is the only way for us to survive.”
While desertification has received tremendous publicity by the political and news media, there are still many things that we don't know about the degradation of productive lands and the expansion of deserts. In 1988 Ridley Nelson pointed out in an important scientific paper that the desertification problem and processes are not clearly defined. There is no consensus among researchers as to the specific causes, extent, or degree of desertification. Contrary to many popular reports, desertification is actually a subtle and complex process of deterioration that may often be reversible.
In the last 25 years, satellites have begun to provide the global monitoring necessary for improving our understanding of desertification. Landsat images of the same area, taken several years apart but during the same point in the growing season, may indicate changes in the susceptibility of land to desertification. Studies using Landsat data help demonstrate the impact of people and animals on the Earth. However, other types of remote-sensing systems, land-monitoring networks, and global data bases of field observations are needed before the process and problems of desertification will be completely understood.
Remedies for Desertification
Remedies for desertification: 1) trapping rainwater with earth mounds between rows of plants or rock walls built along hill contours; 2) shallow ditches arranged in a pattern to trap rainwater; 3) terracing and plow techniques that halt erosion; 4) planting grasses and other plants in a checkerboard pattern to prevent erosion.
At the local level, individuals and governments can help to reclaim and protect their lands. In areas of sand dunes, covering the dunes with large boulders or petroleum will interrupt the wind regime near the face of the dunes and prevent the sand from moving. Sand fences are used throughout the Middle East and the United States, in the same way snow fences are used in the north.
Oases and farmlands in windy regions can be protected by planting tree fences or grass belts. Sand that manages to pass through the grass belts can be caught in strips of trees planted as wind breaks 50 to 100 meters apart adjacent to the belts. Small plots of trees may also be scattered inside oases to stabilize the area. On a much larger scale, a "Green Wall," which will eventually stretch more than 5,700 kilometers in length, much longer than the famous Great Wall, is being planted in northeastern China to protect "sandy lands"--deserts believed to have been created by human activity.
More efficient use of existing water resources and control of salinization are other effective tools for improving arid lands. New ways are being sought to use surface-water resources such as rain water harvesting or irrigating with seasonal runoff from adjacent highlands. New way s also being sought to find and tap groundwater resources and to develop more effective ways of irrigating arid and semiarid lands. Research on the reclamation of deserts also is focusing on discovering proper crop rotation to protect the fragile soil, on understanding how sand-fixing plants can be adapted to local environments, and on how grazing lands and water resources can be developed effectively without being overused.
If we are to stop and reverse the degradation of arid and semiarid lands, we must understand how and why the rates of climate change, population growth, and food production adversely affect these environments. The most effective intervention can come only from the wise use of the best earth-science information available.
Researchers are experiments with drought-resistant crops, desert agriculture techniques and using plants, shrubs and grasses to stabilize dunes.
Trees and Straw Grids
Trees are planted to prevent erosion, stop destructive sand dunes and provide windreaks. Tree roots block wind erosion and help rain penetrate the earth. Poplars are ideal desert trees and windbreaks. They are resistant to winds, salty soils and salty groundwater.
Eucalyptus, tamarind, popular, pines and castor plants grow well in arid climates and provide windbreaks. Sometimes they grown in rows around oasis towns to prevent them from being swallowed up by dunes.
Grids of straw are used to stabilize dunes and stop sand from blowing. Arranged roughly in one-meter square checkerboards, the grids are pressed into the sand, so this the stalks stand four to six inches above the ground. This creates enough of a windbreak to slow surface sand movement, allowing plants to establish themselves The technique was devised to keep sand from blowing across railroad tracks,. This was once a serious problem, blocking tracks and slowing commerce and passenger service.
Straw grids decrease the surface wind velocity. Shrubs and trees planted within the grids are protected by the straw until they take root. In areas where some water is available for irrigation, shrubs planted on the lower one-third of a dune's windward side will stabilize the dune. This vegetation decreases the wind velocity near the base of the dune and prevents much of the sand from moving. Higher velocity winds at the top of the dune level it off and trees can be planted atop these flattened surfaces.
Forest landscape restoration is a process which holds great promise globally for combating deforestation, desertification and global warming. It involves replanting of native vegetation and restricting grazing and over use to rejuvenate land to support local agriculture. The new vegetation also reduces flooding by anchoring the region’s soil and acts as a large carbon sink by sucking in carbon dioxide.
Landscape restoration is a slow, complex and painstaking process. Paul Mozur wrote in the New York Times, “It can take decades for vegetation to fully return, and strict attention must be paid to mundane matters like grazing and over-planting.... Because ecosystems vary based on geography, and lasting success depends on the support of local residents, the process is pesteringly cross-disciplinary. Any forest landscape restoration project requires the know-how of engineers, ecologists and soil scientists, plus an understanding of local economics and politics.”
It is becoming harder to deny the importance of forest landscape restoration in combating climate change. A new study by the World Resources Institute shows that about 1 billion hectares of land could be restored across the globe. Rough estimates indicate that carbon sequestration through this process could eliminate 50 percent more carbon from the atmosphere than a proactive cessation of deforestation could.
Combating Desertification in China
Planting of the Green Belt
To combat desertification, the government has encouraged the planting of drought-resistant trees in erosion-prone areas and helped people to obtain technology that helps them collect and store rainwater. In some places farmers are paid to plant trees rather than raise crops. Pines and poplars provide shields from encroaching dunes. On the Loess Plateau erosion has been reduced, with funding from the World Bank, by terracing the landscape.
In what has been described as the world's most ambitious reforestation project, the Chinese are planting a line of trees and shrubs, paralleling the Great Wall of China, to protect farmland in northern China from Gobi Desert sand blown by the fierce Mongolian winds. Stretching from Xinjiang to Heolongjang, this "Green Wall" will eventually cover strip of land 4,000 miles in length.
Using a technique introduced by the Soviets in 1962, the Chinese have made progress slowing down sand dune migration by putting plants inside "small checkerboards" made of straw bales to protect the plants long enough for them to take hold permanently while stabilizing the dunes and stopping sand from blowing. Arranged roughly in one-meter square checkerboards, the grids are pressed into the sand so that the stalks stand four to six inches above the ground. This creates enough of a windbreak to slow surface sand movement so the plants can establish themselves The technique was devised to keep sand from blowing across railroad tracks — at one time a serious problem that blocked tracks and slowed commerce and passenger service.
In places where overgrazing is a problem fences have been put up and herders have been given plots of land to encourage them to take good care of the land. To reduce the number of animals the government is encouraging herders to cut the size of their flocks by 40 percent, relocate and stall-feed their animals. But herders are not so keen on these ideas. Animals have traditionally been a source of wealth and a kind of insurance for hard times.
The Institute of Desert Research in Shapotou, a town on the Yellow River, is facility that is devoted to solving problems related to desertification. Spread out over one square mile, it employs 19 full time researchers who conduct experiments with drought-resistant crops; desert agriculture techniques; the use of plants, shrubs and grasses to stabilize dunes; petroleum-based dune stabilizing sprays; and Israeli-style drip irrigation.
Beijing insists its efforts are paying off, and says that China’s deserts are shrinking at a rate of 1,200 square kilometers a years, compared to increasing a rate of 3,500 square kilometers in the late 1990s. No everyone accepts these figures.
Migration and Resettlement Because of Desertification in China
Desertification is causing millions of rural Chinese to abandon unproductive land in Gansu, Inner Mongolia and Ningxia Provinces and migrate eastward. A study by the Asian Development Bank found 4,000 villages at risk of being swallowed up by drifting sand.
Already a migration on the scale of the Dust Bowl in the United States in the 1930 is taking place in China. The only problem is that in China there is no California to escape to. Many of those driven off land degraded by desertification have ended up in eastern cities as migrant workers.
In parts of the Ningxia Province, significant rain has not fallen for years and farming is impossible. Tens of thousands of people from villages mostly in poor southern Ningxia have been resettled to 215,000 acres of newly irrigated land near the Yellow River in north central China. The exodus took place between 1998 and 2000 and cost about $325 million. About 70 percent of those affected are Huis. Planners had originally hoped to resettle a million people (20 percent of Ningxia's total population) but there was enough money available to handle that many people.
Text Sources: "Deserts Geology and Resources" by A.S. Walkers, USGS Online publication; Rick Gore, National Geographic, November 1979 [┵]; New York Times, Washington Post, Los Angeles Times, Daily Yomiuri, Times of London, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
Last updated March 2011