Dunhuang, China - In the cool shadows of Cave 98, Ms Li Lingzhi watched as workers in blue suits inspected the Buddhist frescoes commissioned in this Gobi Desert cliff grotto more than a millennium ago by a local ruling family.

It has taken a decade to restore the cave. Metal scaffolding still surrounds the central statue, a three-storey seated Buddha with orange robes.

"We're waiting for an expert to inspect this and then we will discuss when we can open it to the public," said Ms Li, who works on conservation for the Dunhuang Research Academy, which manages the Mogao Caves. "We're monitoring humidity and temperature now in this cave.

Such is the delicate work that goes into preserving the small, centuries-old caves, with nearly 500 of them providing a time capsule of art along the Silk Road and ranking among the world's greatest Buddhist treasures.

There are statues and figurines and frescoes of Buddha with curly hair and sharp noses, a style common in ancient Central Asian art; Tibetan-style bodhisattvas with a thousand arms drawn in the time of Mongol rule; and disciples wearing Indian dhotis. The oldest cave dates back 1,600 years.

The caves marked the western frontier of Chinese empires and the eastern one of Central Asian kingdoms. Camel caravans crossed the Hexi Corridor here laden with spices, silks and scriptures, some of which were deposited in the famous library cave.

An entire school of scholarship called "Dunhuang Studies" has sprung up in the decades since and the area has been designated a World Heritage Site by the United Nations.

But the modern era's threats to the art have been legion: sandstorms, rainwater, local tomb raiders, plundering foreign archaeologists and White Russian soldiers who once lived in the grottoes.

Scholars and preservationists now warn of an even greater looming threat: tourist hordes, even beyond the thousands of daily visitors who flood the area between May and October.

Officials in Gansu province, which includes Dunhuang, and a company in Beijing have drawn up plans for a sprawling theme park connecting the caves with a separate area of sand dunes that already exists as a tourist playground. The connecting strip of desert would be filled with faux temples, folk villages and souvenir stands.

"We hope it won't become reality," said Ms Fan Jinshi, 76, who has worked at the academy since 1963 and directed it for 17 years, until March.

"The Mogao Caves are irreplaceable and nonrenewable. Not only do the caves have to be respected, but the atmosphere around them must be protected too. The atmosphere around them is part of their integrity."

The plan, requested by Gansu officials, was completed last October by the Boya Strategy Consultation Group, a company in Beijing that develops commercial tourism sites across China. In it, Boya designers list shortcomings in the area around the caves, including a lack of hotels, live entertainment, large shopping areas and bus parking lots, according to a copy obtained by The New York Times.

It proposes building a trailer park and campground complete with a drive-in movie theatre, vineyard and wine cellar, and a "Silk Road Village" between the caves and the sand dunes with hotels, shopping malls, museums, performance halls, restaurants, bars and movie theatres.

Its authors give generous estimates of potential income. By 2017, it says, the main tourism zone will attract more than 2.13 million tourists a year, with revenue of 496 million yuan (S$107.6 million). By 2020, the revenue will grow to US$123 million (S$165.7 million).

In the eyes of Ms Fan and her colleagues, the imperatives of preservation must be placed well above tourism. Already, the number of tourists generates anxiety at the academy. After 1979, when the caves were opened to the public, 10,000 to 20,000 people visited annually.

In recent years, the crowds have sometimes reached that number in a single day in the peak season, with a total of 810,000 last year.

There is now a plan to control tourism. The academy built a new visitors' centre about 16km north of the caves. People park there and watch two films about the caves before taking buses to the site. There, guides lead groups in tours through about eight caves, with a limit of 6,000 visitors a day.

One of the films, in 3-D, is projected on the inside of a dome that brings the viewer into six caves, including one with a 26m-high sitting Buddha. "The point is to have people look at the art but without going into the caves," Ms Fan said. "This is the first place in all of China to experiment with this method."

New York Times