Behind the walled farmhouses, where fields of cotton and fennel bask in bright sunshine, the desert begins. Pale ochre sand dunes loom over rows of carefully tended crops that represent a lifetime of labor for the 21 families who live here.

As the desert closes in, this community has been told to leave, so that their fields can be replanted with native grass. Local authorities say this will revive the parched land and halt the sand dunes, and have promised new land and housing to villagers. The forced move is an admission that China's grandiose plans to turn its arid land into farms have run dry.

In recent years, China has met some success in slowing the sands by imposing curbs on grazing in Inner Mongolia and other measures.

But with China's average annual land loss of about950 square miles to desertification, according to researchers at the Chinese Academy of Sciences, in addition to vast swaths of land turned over to industry and housing, the amount of farmland available to feed a large population is being pinched.

In all, more than 10,500 residents of Minqin County in northwest Gansu Province, along the ancient Silk Road, are due to be relocated over the next three years.

It's a tactical retreat after decades of cropping that exhausted scarce water resources. What matters now, say experts, is preventing this and other marginal land from turning into vast dust bowls where nothing grows.

"Minqin is an example of what's happening all over China. If we lose villages here, we can expect to lose villages in other places," says Sun Qingwei, a researcher on desertification at the Chinese Academy of Sciences in Lanzhou, the provincial capital.

For decades, China has been trying to hold back the deserts that cover one-third of the country and produce seasonal sandstorms that scour Beijing and other northern cities. Experts say deforestation and overfarming are to blame for desertification, though global warming may become a greater factor in the future, as the Tibetan glaciers that feed China's waterways are melting.

China has more than 20 percent of the world's population and only 7 percent of its arable land. China announced Monday that rising food prices pushed the inflation rate in July to 5.6 percent, a 10-year high. Adding to the pressure on farmland is rampant environmental degradation that has poisoned waterways and soil.

Attempting to stop the sandy tide

To combat the encroaching Tengger and Badain Jaran deserts, China has planted billions of trees – to replace felled forests and as barriers against the sand. This isn't a panacea, though, say experts, as thirsty trees can exacerbate the problem by sucking up groundwater.

"Planting trees is one way, but it's not that simple. It doesn't tackle the fundamental issue" of water resources, says Wu Bo, a professor at the Chinese Academy of Forestry in Beijing. "We need to calculate how much water the trees will absorb, or else it could have a negative impact."

Villagers in Zhengxin have taken on this challenge, with limited success. When the irrigation channels began to run dry, Lu Xianglin switched from wheat to cotton and fennel on his 12 acres. He also planted trees to protect his fields from sandstorms. He says he still gets good yields using flood irrigation and earns a decent income for his family of six, who live in a walled courtyard house.

Other farmers haven't stuck it out: About 1 in 3 have left Zhengxin in the past 10 years after their wheat crops wilted. Young people who can find jobs in the towns rarely return.

Last week, Mr. Lu joined the other men in his village on a government-arranged trip to see the land that has been set aside for their relocation, nearly 40 miles to the south. The next day, he was back pruning his cotton fields, shaking his head at the plan. The prospect of uprooting his family troubles him, as does the idea of abandoning the land that fed his forefathers. He prefers to stay and keep up the fight.

"With enough water, this problem can be solved," Lu says. "We can plant trees and grass, and they will grow bigger. That will stop the desert."

Experts say that farmers in Zhengxin could switch to drip irrigation to lessen their water intake for growing crops, but warn that it may be too late to reverse the soil erosion. Elsewhere in the region, farmers have erected brick greenhouses this year as part of a plan to grow vegetables using less water. Roadside signs above the windswept plains urge farmers to "Save Water, Protect the Environment."

A legacy of flawed past policies

Elderly residents remember when there was plenty to go around. Hongyashan reservoir, which was built in the 1950s under Mao Zedong's ill-fated "Great Leap Forward" campaign, fed the frontier fields of Minqin, spurring dreams of bumper grain harvests. It was a testament to Mao's dogged belief that man must "use natural science to understand, conquer, and change nature."

But decades of unchecked development, including new upstream cropland, depleted the reservoir, so farmers began sinking wells that sapped the water table and left the soil contaminated with salt. Recent wells go nearly 1,000 feet deep in arid areas.

Today, the reservoir is an expanse of shallow water that occasionally runs dry. A neon sign carries a message from President Hu Jintao, a hydrologist who began his career in Gansu, proclaiming that Minqin must not be lost to the desert.

Heroic posters of Mao still adorn some walls here, but his vow to conquer the desert rings hollow. In Hoanghui, the first village due to move out at the end of August, residents gripe at the government compensation of RMB 3,000 (US$395) per person being offered. To force them out, authorities have turned off wells and stopped farmers from planting their spring crops.

"I have no option," says Zhao Yongfu, a wiry farmer in a baggy blue shirt. "The government tells me to move and won't listen to us."