China's most pristine grassland is being overrun by sand, experts have warned.

The grassland of the Hulun Buir Plateau, in northern Inner Mongolia Autonomous Region, has become the only one of China's major grassland areas still losing ground to desertification.

"Hulun Buir has one of China's four major sand areas," Li Jianjun, an official with the agricultural and animal husbandry bureau in Hulun Buir City, told Xinhua.

"Except for Hulun Buir, the trend of desertification has been basically contained in the other three -- Maowusu, Hunshandake and Horqin," said Li.

A survey this year showed Hulun Buir's sand area had expanded by 110,000 hectares since 1994 to reach 1.3 million hectares, reducing grassland coverage to 9.2 million hectares.

The Hulun Buir Grassland, in the northeast of Inner Mongolia and neighboring Mongolia, Russia and China's Heilongjiang Province, was among the world's most pristine grasslands, but it was damaged over the past decade by overgrazing, farming and extreme weather, like severe drought, said Li.

"Before 1994, the sand area of Hulun Buir was estimated at 533,333 hectares, but people paid little attention to the growing desertification as the grassland coverage was still large," said Zhang Dezhu, director of the Forestry Bureau in Hulun Buir.

He said anti-desertification efforts only began in earnest in 2005, resulting in the treatment of 66,666 hectares of sand area a year, and a grazing ban was partially implemented to help rehabilitate the environment.

In contrast, the treatment of the Horqin sand area from 1995 to 2004 had helped green 770,000 hectares, and stopped desertification.

However, Horqin's sand coverage was estimated at 5.9 million hectares, much larger than that of Hulun Buir.

Zhang said sandy regions were different from deserts, as sandy areas could turn green naturally with sufficient rain.

However, Hulun Buir had suffered lingering droughts in the past decade. The pasture had also degraded by the grazing of 6 million sheep and conversion to farmland, he said.

Cao Zhenghai, Party chief of the city, said the central government had earmarked 150 million yuan (22 million U.S. dollars) for anti-desertification programs in Hulun Buir this year. These were expected to restore greenery to 66,000 hectares.

He said the budget had risen from 50 million yuan a year before 2008 to 150 million yuan last year.

"Funding shortages, however, are still a major issue in desertification control, as the treatment cost has surged from 1,500 yuan per hectare to 3,500 yuan," he said.

He said the cost of labor, for example, rose from 20 yuan per worker a day in 2004 to 70 to 100 yuan this year.

Cao said the city mobilized 150,000 people to plant and cultivate shrubs last year.

"We hope to curb the growing desertificaton in Hulun Buir in three to five years," Cao said.

Inner Mongolia has 40.39 percent of its area, or 47.7 million hectares in total, covered by deserts and sand areas, according to the survey by the region's Academy of Forestry Sciences.

Yan Deren, head of the academy's Inner Mongolia Desert Research Institute, said the coverage had fallen by 6 million hectares since 2004, due to the desert control efforts.