Northwest China's Shaanxi Province has been successful in fending off desert encroachment with afforestation near the ruins of the Great Wall.

Satellite images taken in August 2009 show the wind-and-sand zone along the ancient defence in Yulin City on the Loess Plateau has turned from yellow to green, according to the province's forestry department.

"Compared with images taken in 2000, the forest has expanded about 400 kilometers northward from Yan'an City in the heartland of the Loess Plateau," said Yulin's forestry chief Li Junzhi. "It's a result of sustained afforestation."

China began an ambitious afforestation project in 1978 to curb desert encroachment and soil erosion in the northwestern and northeastern regions. The tree-planting, which created a new forest belt running 7,000 kilometers east to west, also aimed to reduce the intensity of the sandstorms that hit Beijing-centered north China.

The wind-and-sand zone in northern Shaanxi Province, extending 500 kilometers in Yulin City, is one of China's most sparsely populated areas.

"Twenty years ago, we had sandstorm sweeping through all year," said Du Fangxiu, who grew up at the foot of the Great Wall in Dingbian County. "Sand used to fall like snow and would bury all the seedlings in spring."

For years, Du, who made little out of the infertile cropland, planted drought-enduring trees such as poplars and sand willows and selling the lumber for a living.

In response to the government call for "afforestation for ecology", Du stopped lumbering in 2000.

In return, he has been subsidized at least 1 million yuan (147,000 U.S. dollars) for growing 8,000 hectares of forest in the formerly infertile land.

The forests have also nurtured pieces of fertile cropland, where Du grows wheat, vegetables and other economic crops.

Du has written rhyming phrases on the red couplet that hangs on his front door. "Cover the infertile mountain with trees; Turn the crawling desert into oasis," it reads.

But Du is not the only "green campaigner" in Yulin City.

"Many spent heavily planting trees and are honored as the heroes who built the modern 'Great Wall of Forests'," said Li Junzhi, the forestry chief.

One of the heroes is 67-year-old Shi Guangyin, who has fought with sandstorms since he was a kid.

"I remember playing with a boy in the neighborhood one day and a sudden sandstorm swept us away," Shi said. "I shivered in the cold for days before my dad found me, about kilometers away from my home. That little boy was never found again. He was five and I was eight."

In 1984, Shi founded a company to combat sand with seven other rural families and planted trees on 200 hectares of land.

To date, his company has spent more than 10 million yuan to plant and reinforce 13,000 hectares of forests in Dingbian County.

After the sand was curbed, Shi's company began investing in ecological farms, economic crops and many other businesses that yielded better economic returns.

Shi himself was awarded "outstanding farmer" by the Food and Agriculture Organization of the United Nations in 2002.

In the past decade, Shaanxi Province spent nearly 22 billion yuan to plant 4.5 million hectares of forests, said Zhang Shenian, chief of the provincial forestry department.

"The province's forest coverage has increased to 37 percent from 30 percent in 2000," said Zhang.

Even in Yulin City, which is surrounded by encroaching desert, forest coverage has reached 30 percent.

The number of sandy days in the city was less than 10 last year, compared with nearly 30 days in the 1960s, according to figures released by the local weather bureau.

The forests have improved the living conditions of the local residents and helped protect what is left of the Great Wall from being devoured by the desert.

The Shaanxi section of the Great Wall is on the main trunk of the Wall that runs from Shanhaiguan Pass in north China's Hebei Province west to Jiayuguan Pass in Gansu Province.

The Shaanxi section of the Wall, which runs 470 km across the Loess plateau along the northern border of the province, was an important defence for Xi'an, the ancient Chinese capital.

It also served as the city wall for Yulin, a historical center for trade and a former military base.