By Jeffrey Levin

The Mogao Grottoes. The cliff face was reinforced and concrete walkways and stairways added in the 1960s. Photo: Dusan Stulik.

For well over a thousand years, China, Central Asia, and the lands to the west were connected by trade routes collectively known today as the Silk Road. Beginning with the rule of the Han emperors (207 B.C.E.-220 C.E.), caravans following the route brought silk and other commodities such as ceramics, furs, iron, and cinnamon all the way from China to places as far west as Rome. Going east on this ancient track were goods from the West favored in the East—among them woolen and linen textiles, amber, ivory, glass, and gold.

The Silk Road also served as a highway for religious thought, for along its great stretches traveled not only merchants, but missionaries and pilgrims, carrying with them the creed of Buddhism which first flowered in India. It was via the Silk Road that Buddhism reached the Chinese, powerfully influencing their art and culture.

By the close of the fifteenth century the great caravans of East-West trade were no more. The drying up of oases along the route and the geopolitical changes in Central Asia resulting from the rise of Islam contributed to the road's slow abandonment. China closed herself off from the West, and European traders sought to reach her markets by sea.

But long after the caravans had vanished, a record of the life that flourished in China in the days of the Silk Road remained in the art of the Buddhist grotto temples established along the route. Today, the value of these sites resides not only in their inspiring spirituality and artistic mastery, but also in the wealth of information they provide regarding the culture of the age that produced them.

The Mogao Grottoes. The cliff face was reinforced and concrete walkways and stairways added in the 1960s. Photo: Dusan Stulik.

Preserving these sites and others like them is a complex task. To aid in this pursuit, experts from around the world gathered in China in October 1993 for a conference organized by the Dunhuang Academy, the Getty Conservation Institute, and the Chinese National Institute of Cultural Property. Meeting at the Dunhuang Academy's facility near the spectacular Mogao Grottoes, participants shared research results on the preservation of temple grottoes that are spread throughout Asia.

"The numbers are quite stunning," observed Senake Bandaranayake, a speaker at the conference and Director of the Postgraduate Institute of Archaeology in Sri Lanka. "India has 1,200 known sites. China reports 250. In Sri Lanka there are 260 to 270." According to Dr. Bandaranayake, the evolution and typology of these rock temples—80 percent of them Buddhist in origin—have been little studied in a comparative way.

Conservation of grotto sites from across Asia was discussed in the nearly sixty papers presented to the conference's participants. But the site that received the most attention was the one a short walk from the conference itself.

The Mogao Grottoes

Flying aspara, painted in Cave 327 during the Western Xia Dynasty (1035-1227). Photo: ©Beijing Slides Publishing Company.

A World Heritage site, the Mogao Grottoes are 1,770 kilometers (1,100 miles) west of Beijing near the city of Dunhuang, an oasis at the edge of the Gobi Desert in Gansu Province. In the age of the Silk Road, Dunhuang was a major crossroads for the caravan routes that skirted along the northern and southern edges of the desolate and feared Takla Makan Desert to the west.

Situated in a landscape of barren rock mountains and vast sand dunes, the rock temples of Mogao were begun in the middle of the 4th century A.D. by a monk who, it is said, had a vision of a thousand Buddhas. Over the next ten centuries, Chinese Buddhists carved an extensive series of grottoes along the site's 1.6 kilometers (1 mile) of cliff face. Today there remain more than 490 temples containing wall paintings covering 45,000 square meters (484,200 square feet), making Mogao the site of the largest single collection of Buddhist mural art in China. The walls of the grottoes depict a remarkable array of legends, portraits, ornamental designs, historical anecdotes with Buddhist themes, and scenes of social and commercial life. According to Duan Wenjie, the present director of the Dunhuang Academy who has served on the Academy's staff since its founding fifty years ago, the mural art at Mogao "has added inestimably to our understanding of medieval life in China." The grottoes also contain more than 2,000 brightly painted clay sculptures of Buddha and other figures, the largest over 32.8 meters (108 feet) in height.

Contributing to the grottoes' survival through the centuries is Mogao's remoteness and arid climate. Still, serious problems confront the site. Mogao is on the edge of an earthquake zone, and although no caves have collapsed in six decades, certain areas of the cliff face are structurally unstable and threaten to topple. Behind the cliff is a plateau of high sand dunes extending several kilometers to the west. Sand, stones, and fine dust continually cascade down the face of the cliffs in rivulets, and every year approximately 2,000 cubic meters (70,600 cubic feet) of sand—the equivalent of seven hundred truckloads—must be manually removed.

The Great Buddha from Cave 130, created during the Tang Dynasty (618-906 A.D.). Photo: Guillermo Aldana.

Damage at the site extends inside to the wall paintings and sculpture. Parts of sculptures have been broken or lost, while base supports for some sculptures are sagging. Wall paintings have suffered physical abrasion, paint detachment and peeling, and color changes. The penetration of rain and snow in the thin-roofed upper caves, the presence of sand and dust throughout the grottoes, and now the likelihood of humidity and temperature stress produced by burgeoning tourism at the site all contribute to deterioration of the grottoes' artistic treasures.

Some treasures from Mogao—in particular, sculpture, paintings, and scrolls—were removed from the site early in this century by explorers and archaeologists from the West and Japan. Sir Aurel Stein, a Hungarian-born British citizen, was the first of these to reach Dunhuang, and he left the site with hundreds of thousand-year-old manuscripts in his possession. He was followed by others who acquired more manuscripts and other relics as well. Most of these items are now held by institutions in the West.

Conserving the Site

In 1988, the Getty Conservation Institute began collaborating with the People's Republic of China (PRC) in developing a conservation program for the grottoes at Mogao and for those at Yungang, near Datong in eastern China. As the Institute's Director, Miguel Angel Corzo, told the Dunhuang Conference, "at both places we have taken a broad approach based on the most severe threats to the sites." As described to the conference by Neville Agnew, the Institute's Special Projects Director, those threats at Mogao include "the wind-driven sand, the structural cracks in the rock, the very soft conglomerate rock found here, the deterioration of the roofs of the grottoes that require stabilization, and the need for enhancement of training in technical and scientific methods and materials."

Working closely with the PRC's State Bureau of Cultural Relics (SBCR), the Conservation Institute conducted an analysis of Mogao's problems, then concentrated on measures to enhance the site's survival as a whole, adhering in its activities to the principle of limited intervention. Analysis began with a program of site monitoring. Environmental data—including temperature, humidity, wind speed and direction, sunlight, and rainfall—continue being recorded by a solar-powered monitoring station installed on the cliff above the grottoes (the station was designed by Shin Maekawa, Head of Environmental Science at the Institute). Microclimate data are also being gathered by similar monitoring systems installed in two caves—one open to the public, the other closed—to assess whether the increases in humidity and carbon dioxide caused by visitors are damaging the grottoes' wall paintings and sculpture. The Institute is training Chinese scientists to analyze the data to make informed decisions on managing the numbers of visitors and their time spent within the grottoes.

Shin Maekawa of the Institute installing the environmental monitoring station at the Mogao Grottos, assisted by Chinese project team members. Photo: R. Tseng.	Li Tie Chao, a Chinese member of the project team, performs color monitoring in one of the grottoes. Photo: R. Tseng.

To better understand the grottoes' structural cracking, a program of crack monitoring was initiated in 1991. Here, too, Chinese team members were trained in several monitoring techniques, and monitoring is ongoing. Members of the Dunhuang Academy staff were also instructed in use of color monitoring equipment. Measurement of the colors in selected wall paintings was performed, and this record will provide team members with a basis for evaluating color changes of pigments over time.

To reduce sand at the Mogao site, a 3.7-kilometer (2.3-mile) windbreak composed of synthetic textiles was erected on the cliff above the caves in the fall of 1991. The fence reduced wind speed by about 50 percent, and measurements taken during the year following its installation indicated that the windbreak cut sand accumulation at the foot of the caves by over 60 percent. With the intent of establishing a natural windbreak to supplement and ultimately replace the fence, desert-adapted trees and shrubs were planted on an experimental basis in May 1992, irrigated by a drip-feed irrigation system.

To restrict the amount of sand and dust infiltrating the grottoes, the project team installed filters in doorways of selected caves. Monitoring of caves both with and without the filters indicates that the filters reduce the dust in the air by approximately 50 percent.

Conservation Institute and SBCR staff are experimenting with several techniques to prevent further damage to the thin-roofed caves in the upper levels of the cliff. The erosion is so great that some caves are now exposed to the elements. Using geosynthetic materials, the team created a prototype for reinforcing roofs and halting water leakage. In addition, several chemical consolidants are being tested for possible use to prevent erosion of the soft rock of the cliff slope.

From the Chinese standpoint, the benefits of these efforts extend beyond the site itself. "Through our cooperation with the Getty Conservation Institute, our scientific and research personnel have greatly improved the quality of their day-to-day work," remarked Huang Kezhong, Deputy Director of the Chinese National Institute of Cultural Property, at the close of the first day of the conference. "Such cooperation has helped introduce advanced equipment and technology from abroad, and opened up our vision."

The Dunhuang Conference

Some Dunhuang conference participants visiting areas above the grottoes where chemical consolidants are being tested for use in erosion protection. Photo: Neville Agnew.	A portion of the synthetic textile fence erected on the cliff above the caves, designed to reduce sand accumulation at the site. Photo: Guillermo Aldana.

Much of what has been learned from the Mogao and the Yungang projects was shared with the participants at the Dunhuang Conference. But conference speakers provided a perspective on the conservation of grotto sites that encompassed more than the specific problems of these two sites, emphasizing among other things the importance of careful site management.

"Physical conservation goes hand in hand with good management," stated Sharon Sullivan, Director of the Australian Heritage Commission, in one of the conference's four keynote addresses. "The establishment of a viable ongoing management framework and management plan to achieve certain specified ends is in fact an essential prerequisite to any significant decisions about physical conservation which involve intervention in the fabric."

Rapidly increasing tourism is a major challenge for site managers in Asia. "We are at overload levels at many of our most important sites ," Robertson Collins of the ICOMOS Committee on Cultural Tourism told conference participants. "The number of visitors to the Buddhist sites, both religious and secular, has grown far beyond the carrying capacity envisioned by the original builders—and frequently way beyond the budgets of the conservation departments that now manage those sites." He noted with some irony that the stage has been reached where "we need tourists to get the money to protect our sites from tourism." Site managers, he observed, typically have regarded those in tourism development with alarm. With better communication between both sides, he suggested, tourism could become an ally of site conservation by fostering more political support for those responsible for site custodianship.

Sculpture of a Buddha in Cave 328, dating from the Tang Dynasty (618-906). Photo: ©Dunhuang Arts Photograph Company.

Mogao itself offered an example of the significance of tourist revenue in supporting economic development. Ma Wenzhi, head of Gansu Province's Cultural Department, remarked that "because of the tourist attraction of [the Mogao Grottoes] the economy in this area has been developing the fastest of all the areas within Gansu province, and people here enjoy the highest salaries."

As several at the conference emphasized, consideration of the economic potential of a site must be tempered with a recognition of a site's preservation needs. The temptation to exploit a site can ultimately lead to site damage if public access is provided without carefully considered safeguards.

"Don't be seduced by the economic benefits of tourism by allowing access too soon," cautioned Jeffrey Cody of Cornell University's Department of City and Regional Planning in his address to the conference. "Careful planning can save money and better protect a site for the future."

Another of the keynote speakers addressed the problem of communication within an increasingly diverse profession. Sharon Cather of the Conservation of Wall Paintings Department at London's Courtauld Institute of Art observed that "in doing preventative conservation we start cutting across other professional expertise...I think that's very clear from the range of contributions that we have at this conference—we have people in geotechnical studies, we have chemists, art historians, and site managers." A conference like the one at Dunhuang is important, she said, because "one of the ways we can learn to communicate better is if we have at least some basic understanding of what our colleagues are doing in other fields of expertise."

"Perhaps the main value in this conference is to see that people everywhere have the same kinds of problems," remarked Senake Bandaranayake of Sri Lanka during one of the conference breaks. It also, he said, helps propagate "emerging philosophical trends in conservation that jog one into rethinking the conscious or unconscious philosophy behind one's work."

The Buddhist grottoes of China, particularly those of the Silk Road, are the physical remains of an ancient time when an abundance of goods regularly passed back and forth between East and West. But as the grottoes themselves eloquently declare with their art, the Silk Road was more than a commercial link. The rock temples at Mogao and elsewhere are a testament to the power of the spiritual beliefs that also traveled the Silk Road and produced the remarkable Buddhist murals and sculpture that adorn the spaces of these historic sites. It therefore seems utterly fitting that conservation professionals from East and West gathered at Dunhuang, a Silk Road crossroads, to trade ideas on how best to preserve the heritage left to us from that earlier and culturally rich era of exchange.

Jeffrey Levin is the Editor of Conservation, The GCI Newsletter.