by Danielle Knight
(IPS) WASHINGTON --
was one of the largest dust storms recorded in history, stretching up to 2,000 kilometers in length and 800 kilometers in width. It began as a cyclone in northwestern China and moved eastward.
As it moved east, it was visible by satellite over eastern China, Japan, and Russia's Far East, where it closed airports, slowed traffic, obscured the sun and reduced visibility. Two weeks later, the mammoth dust storm reached North America where it blanketed parts of western Canada and the United States.
By the time the storm had dissipated over the Atlantic Ocean on Apr. 21, it had travelled across two-thirds of the globe.
This dust storm, one of about a dozen smaller tempests originating in China this year, did not surprise researchers who have been warning that the range land and cropland in the Asian country's vast northwest is rapidly degenerating.
"If China cannot quickly arrest the trends of deterioration, the growth of the dust bowl could acquire an irreversible momentum," says Lester Brown, president and founder of the Earth Policy Institute, a new Washington-based environmental think-tank.
Most news reports on the dust storm attribute the phenomenon to the drought of the last three years. But Brown says the drought is simply bringing a fast-deteriorating situation into focus.
"Human pressure on the land in northwestern China is excessive," he says. "There are simply too many people, too many cattle and sheep, and too many plows."
geographers blame part of the stress on the land on a 1994 decision by Beijing requiring that all fertile cropland that is converted and developed for construction be offset by land reclaimed elsewhere.
In a recent article in the peer reviewed journal, Land Use Policy, Hong Yang and Xiubein Li describe how this policy caused excessive plowing in the northwest, an area that was already over-grazed by livestock.
The growing coastal provinces that lost cropland to urban expansion and industrial construction were forced to pay the northwest provinces to farm more land, thus intensifying soil erosion, says the article.
"Now accelerating wind erosion of soil and the resulting land abandonment are forcing people to migrate eastward, not unlike the U.S. westward migration from the southern Great Plains to California during the Dust Bowl of the 1930s," says Brown.
While plows are working overtime, expanding livestock populations are clearing the land of vegetation that would prevent the soil from eroding, say researchers. Following economic reforms in 1978 that removed controls on the size of livestock herds and flocks, the populations of cows and sheep grew rapidly.
In Gonge Country in eastern Quinghai Province, the number of sheep that local grasslands can sustain is estimated at 3.7 million, according to Brown, who plans to travel to China in several months to lecture on soil erosion.
"But by the end of 1998, sheep numbers there had reached 5.5 million, far beyond the land's carrying capacity," he says. "The result is fast-deteriorating grassland, desertification, and the formation of sand dunes."
Chinese officials estimate that over 1500 square miles of land turn to desert each year. In response to the crisis, the government is considering planting a huge belt of trees that would separate the desert from fertile ground.
In addition to over-plowing and over-grazing, researchers say the northern half of China is literally drying out as rainfall declines and aquifers are depleted from overuse. Under China's northern plain, which produces 40 percent of the country's grain harvest, the water table is falling by 1.6 meters a year.
"As aquifer depletion and the diversion of water to cities shrink irrigation water supplies, China may be forced to import grain on a scale that could destabilise world grain markets," say Brown.
The cutting of trees in southern and eastern China is also complicating the problem, say researchers.
According to Wang Hongchang, a fellow at the Chinese Academy of Social Sciences, deforestation in southern and eastern China is reducing moisture transported inland from the South China Sea, the East China Sea, and the Yellow Sea.
Where land is forested, the water is held and evaporates to be carried further inland by rain patterns. But when tree cover is removed, the first rainfall from inland-moving air simply runs off and returns to the sea.
"As this recycling of rainfall inland is weakened by deforestation, rainfall in the interior is declining," says Brown.
Reversing soil degradation, he says, means stabilizing population and planting trees through the country to help recycle rainfall inland.
"It means converting eroded cropland back to grassland or woodland, reducing the livestock population, and planting tree shelter belts across the windswept areas of cropland, as U.S. farmers did to end dust storms in the 1930s," he says.
Brown also advocates the use of wind turbines as windbreaks in order to reduce wind speed and soil erosion.
"With the cost of wind-generated electricity now competitive with that generated from fossil fuels, constructing rows of wind turbines in strategic areas to slow the wind could greatly reduce the erosion of soil," he says.
Brown acknowledges that reversing desertification will require a huge effort.
But he warns that if the dust bowl continues to spread, "it will not only undermine the economy, but it will also trigger a massive migration of tens of millions of people eastward."
May 28, 2001 (http://www.monitor.net/monitor) All Rights Reserved. Contact email@example.com for permission to use in any format.
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