Experts use advanced research to protect fragile earthen ruins and assist overseas partners, report Wang Ru and Ma Jingna in Dunhuang, Gansu.

Mural restoration is carried out in one of the Mogao Caves in Dunhuang, Gansu province. [Photo provided to China Daily]

Guo Qinglin still remembers a visit to Yumen Pass not long after he joined the Dunhuang Academy in 1999, in Dunhuang, Gansu province. He had followed senior colleagues to inspect the strategic Han Dynasty (206 BC-AD 220) fort, a vital gateway on the ancient Silk Road, and nearby sections of the Great Wall in Gansu. As he watched the crumbling fortifications, he noticed the expression on Li Zuixiong's (1941-2019) face grow increasingly grave.

"We cannot let such heritage disappear on our watch. We must accelerate research and development of conservation techniques for earthen sites," he recalls Li, then deputy director of the academy, saying.

That moment set Guo on a path from geology graduate to one of the world's leading experts in the conservation of earthen sites. Now 50, Guo is director of the academy which oversees the Mogao Caves — a UNESCO World Heritage site comprising hundreds of Buddhist caves adorned with murals and statues dating from the 4th to the 14th centuries. Over the years, he has watched the academy's conservation capabilities steadily evolve. Today, he leads his colleagues in sharing their expertise abroad, helping safeguard treasures that belong to all of humanity.

Guo's entry into the field was almost accidental. After graduating with a degree in geology from Lanzhou University in Gansu, Guo was introduced to the Dunhuang Academy by his teacher. At the time, he had only a vague sense that cultural heritage protection was something "sacred".

"I remember I told Wang Xudong, who worked as a staff member recruiting graduates from my university and later became director of the academy, that I didn't know much about cultural heritage conservation," Guo recalls. "He replied, 'That's okay. You can learn gradually'."

Conditions at the academy were tough in those days. Located on the outskirts of Dunhuang, the institution had limited amenities, and staff members could take a shuttle bus to downtown only twice a week to bathe or make phone calls. At the same time, a lack of domestic expertise in conservation prompted extensive international cooperation. Before Guo joined the academy, cooperation with institutions in Japan and the United States in the 1980s had already brought advanced conservation philosophies and techniques to Dunhuang's conservators.

"Building on that foundation, our professionals made further innovations and eventually developed three major technology systems surrounding the protection and repair of ancient murals, protection and consolidation of earthen remains, and digitization of wall paintings and painted sculptures in cave temples," Guo says.

Guo Qinglin (second from right), director of the Dunhuang Academy, checks a multi-field coupling environmental simulation laboratory. [Photo provided to China Daily]

From a team of four members in the 1960s, the academy's conservation workforce has grown to nearly 200 people.

Mural conservation offers a telling example. China had long possessed traditional techniques, but many relied on artisans' personal experience rather than scientific analysis. Through collaboration with US experts, Chinese professionals gained a deeper understanding of the causes of mural deterioration. They refined their methods through scientific research, transforming experience-based practices into science-based conservation.

The cooperation also helped improve procedures. Overseas experts introduced a value-analysis step that Chinese professionals had previously overlooked, helping establish a comprehensive workflow for cultural heritage conservation: value analysis, on-site investigation, environmental monitoring, deterioration mechanism analysis, plan formulation and final implementation.

"Later, we applied these procedures to more than 300 cultural heritage projects across 21 provinces, municipalities and autonomous regions, including the restoration of murals at the Potala Palace in Lhasa, Xizang autonomous region," says Guo. "When our methods are scientifically sound, we can largely ensure good outcomes."

Of the academy's three major technology systems, the conservation of earthen relics has posed the greatest challenge and remained a key focus for decades. Of China's 767,000 immovable cultural heritage sites, about one-third are earthen relics, many of which have been listed as World Heritage sites.

"Made of earth, such relics are relatively fragile, as they are often exposed outdoors and can easily collapse or weather, leading to their fast disappearance, along with the precious historical information they carry," Guo says. "Protection of earthen sites is a world-class challenge."

The academy's attempt to protect such sites started in 1992. Early attempts involved adding chemical consolidating materials. Later, geotechnical engineering techniques, such as grouting reinforcement, were introduced, gradually evolving into a comprehensive system. The system has been successfully applied to the Jiaohe Ruins in Turpan, Xinjiang Uygur autonomous region, since 2006, and the Xixia Imperial Tombs in Yinchuan, Ningxia Hui autonomous region, since 1999, both of which are on the World Heritage List.

Part of a mural restored in Dunhuang. [Photo provided to China Daily]

As protection techniques matured, the next frontier was understanding long-term effects of the environment. In 2020, the academy launched a multi-field coupling environmental simulation laboratory for mural and ruin protection.

The lab can simulate temperature ranges between — 30 C and 60 C and relative humidity from 10 to 90 percent, as well as various climatic conditions across all four seasons, including wind, rain, snow, and sunlight for experimental testing. This allows researchers not only to understand a site's present condition, but also to glimpse its past and future, says Guo.

With these systems now well established, the Dunhuang Academy is increasingly taking its conservation expertise abroad. "Cultural heritage is a witness to a country's history, so every nation wants to protect it," says Guo. "Having benefited from international cooperation ourselves, we feel a responsibility to share our experience with counterparts abroad, to help them safeguard their heritage, which actually belongs to all of humanity."

In 2024, the academy signed memoranda with cultural heritage institutes in Uzbekistan, Kyrgyzstan, Sri Lanka, and Cambodia, covering joint site protection, exchanges of theories and techniques, cultural exhibitions, academic activities, and professional training. In 2025, the China-Kyrgyzstan Belt and Road Joint Laboratory on Cultural Heritage Conservation was approved for construction to advance these efforts. "Local people understand their own culture best," says Guo. "We offer techniques and discuss protection ideas together. In this way, we cooperate to protect their cultural heritage."

This year, academy professionals arrived at the ruins of the ancient city of Suyab in Kyrgyzstan, a key city on the ancient Silk Road that is now recognized as a World Heritage site, to establish a comprehensive experimental platform for heritage protection.

Aisin Duishanalieva, director of the Republican Inspectorate for the Protection of Historical and Cultural Monuments of the Ministry of Culture of the Kyrgyz Republic, told Global Times earlier that the lab, built under the Belt and Road Initiative, has established systematic research capacity and will continue to develop. "Through this joint collaboration, we can study and excavate cultural relics along the Silk Road and better popularize them in our two countries," she said.

Guo says: "Our academy will remain engaged in domestic and international cooperation, protect grottoes and share their art with an increasingly open approach, and attract more scholars, especially young ones, to join us.

"We will conduct comprehensive, multidisciplinary research on Dunhuang sites in the broader context of human civilization, dig deep into their historical, artistic and scientific value, and contribute to the cultural diversity of the world," he adds.

Dunhuang Academy's protection techniques have been successfully applied to the Jiaohe Ruins in Turpan, Xinjiang Uygur autonomous region. [Photo provided to China Daily]

A distant view of the Mogao Caves. [Photo provided to China Daily]