Chinese and American scientists are using a fence to control sand from eroding ancient grottoes in northwest China.

A joint research group built a 4.7-km long fence outside the Mogao Grottoes. It reduced the amount of sand hitting the caves by 60 percent.

The experiment was published in the latest issue of Science.

A UNESCO World Heritage site, the 1,600-year-old Buddhist caves, near Dunhuang in the land-locked Gansu Province, are on the hillside of sandy mountains known as the Mingsha Mountains.

Qu Jianjun, a principal investigator at the Chinese Academy of Sciences (CAS) Cold and Arid Regions Environment and Engineering Research Institute said Wednesday, researchers began the project by planting trees between the grottoes and the mountains. They also set up a nylon fence above the caves to stop sand from coming down the cliff.

When that wasn't enough, Qu, who led the research team, said scientists covered up large blocks of sand on the ground using nylon and rocks.

The U.S. Getty Conservation Institute and the local Dunhuang Academy collaborated on the project.

Scientists have been working together since the mid 1990s to save the grottoes. Their original focus was natural landscaping, however, now they use advanced technologies to protect paintings in the caves, Qu said.

The Mogao Grottoes have suffered damage for several centuries.

Dozens of Buddha sculptures were stolen or destroyed 600 years ago.

The worst damage to the caves occurred around 1900, Qu said, when an armed tsarist Russia squad hid in the caves. Soldiers destroyed murals by scribbling on walls. Smoke from their cooking also covered several paintings.

Mother nature is also to blame for damaging the grottoes.

All five tiers of the caves were dug on the west bank of the Daquan River, which was fed by glaciers. When those glaciers melted, water entered the lower caves destroying murals. In the 1960s a dam was built on the upper reaches of the river to protect the grottoes.

The Chinese government allocated US$38 million in 2008 to protect artwork in the caves.

(Xinhua News Agency October 15, 2008)