"Over the last few years, there has been a growing awareness that air pollution from China is affecting us," said Russ Schnell, an official at the U.S. National Oceanic and Atmospheric Administration, which tracked the recent dust clouds.
"Pollution is a global problem," he added. "Nature has sent us 'a perfect storm' to reinforce the fact that we are all downwind of someone else's pollution."
Uncontrolled Land Use
Ironically, the rapid deterioration of China's cropland has resulted in part from programs aimed at increasing agricultural output. Decades of reforms have included measures that removed limits on the amount of land that farmers could cultivate and the size of herds and flocks they could maintain. As a result, the demand for land has soared.
Another factor contributing to the problem is a 1994 policy requiring that any cropland used for construction be offset by setting aside land elsewhere for agriculture.
Fast-growing coastal provinces, such as Guangdong, Shandong, Zhejiang, and Jiangsu, are losing much cropland to urban expansion. Agricultural and pastoral provinces in the northwest, such as Nei Mongolia, Gansu, Qinghai, Ningxia, and Xinjiang, initially garnered an economic windfall from the policy, but are increasingly faced with plowing ever more marginal land.
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 years.
Adding to the direct damage to soil, the northern half of China is becoming drier and sources of natural irrigation more scarce. Temperatures in the region have been hotter than average in the past 10 years, and aquifers are being depleted by overpumping.
U.S. satellites, which have monitored land use in China for three decades, show that thousands of lakes in the north have disappeared. And rapid industrial development has reduced forests and other vegetation that once provided moisture to the region.
In some areas the land has been rendered so useless that farmers have abandoned their homes and fields, which are now covered with wind-blown sand dunes. Where farming is still practiced, some reports indicate that typical yields of crops such as potato, rice, and corn have shrunk dramatically, making harvests no longer profitable.
"The big risk is that it's going to push a lot of people into cities in a major migration," said Brown.
The Chinese government has been pursuing varied approaches to make the now highly arid land productive again. One strategy is planting trees and tracts of grass in "checkerboard" patterns, which has increased vegetation coverage in some areas and reduced the buildup of sand dunes.
During the late 1970s and early '80s, a system of agricultural "shelterbelts" was implemented by reforesting large tracts of land to anchor and irrigate loose soil and help stem the flow of dust storms across China.
Government reports indicate that some progress is being made in reversing the massive loss of land. Among the successful efforts cited, the buildup of sand dunes in some provinces has been reduced by as much as 64 percent, and total forest cover nationwide increased by 14 percent in 1995 as a result of intensive planting.
Yet some people are concerned that the ever more intensive cultivation of land in the north over the past decade has outpaced what progress has been made.
"If China cannot quickly arrest the trends of deterioration, the growth of the dust bowl could acquire an irreversible momentum," Brown warned. "What is at stake is not just China's soil, but its future."
Studies by Chinese scientists and the World Bank have concluded that China has lost U.S. $2 billion to $3 billion a year over the past decade from the effects of lost land and productivity, threatening the livelihood of at least 170 million people.
"Desertification has become a bottleneck for the social and economic development and the improvement of people's living standard in some areas," Jiang Chunyun, vice premier of China's State Council, declared at a 1997 United Nations conference on desertification.
"[In] other areas most severely affected by desertification," he added, "the problem of food and shelter for local residents remains unsolved."
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