Inspectors have been dispatched to aid a probe into a massive deforestation case in Dunhuang, Gansu province, the National Forestry and Grassland Administration said on Thursday.

Nearly 1,000 hectares of forest that was created to fend off sand and desert in the city were illegally logged in the past decade and replaced by grape farms, the Economic Information Daily reported on Wednesday morning.

Based on two satellite remote sensing images provided by authorities, the report said the forest area under the supervision of the Yangguan forest station plummeted from 1,333 hectares in 2000 to 333 hectares in 2017.

Surveys conducted by the Economic Information Daily earlier this month showed three-quarters of the station's area is now covered by grape farms.

The administration dispatched inspectors from its branch inspection office in the neighboring province of Shaanxi on Wednesday, it announced on its Sina Weibo microblog.

"The inspectors will help to solve problems related to the case. And the administration will give no tolerance to any illegal activities," it said.

The forest, on the edge of Kumtag Desert, played a significant role in preventing sandstorms, conserving water and soil, and safeguarding agriculture.

Plans to create the forest began in 1963. After decades of continuous effort, it had 4 million trees by 2000, helping to prevent further expansion of China's sixth-largest desert.

Deforestation increases the threat to Dunhuang, a city with 198,000 residents. Only about 70 kilometers from the forest, it was an important link on the ancient Silk Road.

Yangguan was the site of one of the two passes on the Silk Road that separated the core land controlled by ancient Chinese dynasties from western regions.

The report said grape farms had been expanding in the area controlled by the forest station since 2000 and had become a supporting business for the station.

However, as a plant that demands lots of water, grapes are not a preferred choice for desertification control.

According to the Gansu Sand Control Research Center, grapes need four to 12 times as much water as other plants that are more commonly used for combating desertification, such as salix, honey tree and hedysarum.

Si Jianhua, a researcher from the Northwest Institute of Eco-environment and Resources, said planting grapes would make the ecosystem in the region more fragile and increase the risk of desert expansion.

According to the report, Wei Haidong, who is in charge of the forest station, said grape farms in the area only covered 247 hectares in 2006 and "have not expanded in past years".

On Wednesday afternoon, a special work team was established by Dunhuang's city government to look into the case.

"We've paid a great deal of attention to the report, and we will conduct an investigation in accordance with the law and reveal the result in a timely manner," the administration said.