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Great wall of trees keeps China’s deserts at bay
by Fred Pearce
CHINA is holding back the desert, for now. The Great Green Wall – a massive belt of trees being planted across China’s arid north in what might be the largest ecological engineering project on the planet – seems to work, according to a new study.
“Vegetation has improved and dust storms have decreased significantly in the Great Green Wall region, compared with other areas,” says Minghong Tan of the Institute of Geographical Sciences and Natural Resource Research in Beijing. But whether planting trees is a long-term solution remains disputed.
The Gobi and Taklamakan deserts of northern China are Asia’s biggest dust bowls. Storms generated there regularly shroud Beijing in dust, which can also fall as far away as Greenland. In an effort to tame the deserts, in 1978 China began planting the wall, which is officially called the Three-North Shelterbelt Forest Programme. It is due for completion in 2050 and will eventually contain more than 100 billion trees in a 4500-kilometre belt, covering more than a tenth of the country. But opinion is divided about its success and advisability, and it has met with widespread scepticism among Western geographers.
Some credit a rise in rainfall for the decrease in dust storms across northern China over the past three decades. But Tan and co-author Xiubin Li say that their analysis of rainfall data, satellite images and an index of dust storms shows conclusively that the Green Wall is the main cause of the improvement (Land Use Policy, doi.org/xk2).
Away from the wall, vegetation cover and dust storms have risen and fallen with precipitation. But nearer to the trees, vegetation increased and dust storms diminished between 1981 and 1998, the end of the study period. Tan says the improvement has since continued. “In most places in the study area, greenness continued to increase between 2000 and 2010,” he says. “In North China as a whole, we think the environment is getting well.”