Since 2015, professionals in stone cultural relic protection have been carrying out annual surveys and formulated a Yungang Grottoes degeneration investigation graphic standard, which includes classification, mapping, description, analysis and reporting on the levels of degeneration in the caves.

Surveys were conducted in 20 grottoes to accumulate the firsthand information needed to set a reliable basis for decision-making when it comes to the management of the grottoes, he said.

"The protection of the Yungang Grottoes has changed from rescue work to prevention and protection, and will change to research and protection in the future," Yan said.

"Current protection can be divided into internal protection, external protection and environmental protection, as well as related preventive protection and monitoring, safety protection and technology protection."

Since 2015, the academy has conducted internal protection in 20 grottoes and greatly improved the preservation of temples and painted murals.

"We have basically completed external protection of the Yungang Grottoes," he said.

"This refers to the mountain in which the caves are dug."

Now, the academy has a protection team of around 20 members, some of them local villagers.

"They have lived here since childhood, so they have a deep affection for Yungang," Yan said. "After several years of training and practice, they also have a deep understanding of the concept, technology, materials and other aspects of cultural relic protection and restoration.

"However, the conservation of the site is a large, systematic project with quite a heavy workload," he said.

"We hope more people will join the team so research capabilities can be gradually enhanced."

Peng Ke'er contributed to this story.