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“Gansu is famous for its caves and the art stored inside them for centuries,” said Li Zhao, a Beijing-based researcher at Greenpeace East Asia. “Increased bouts of rainfall in the desert pose an acute risk. Spikes in humidity, flash floods and cave-ins are already happening.”
Over the past two decades, temperatures in Gansu have risen faster than the global average. At the same time, overall summer rainfall has risen even as total days of precipitation have dropped — meaning that when it rains, it often pours.
The intensifying extreme weather is already causing damage in the Mogao Caves, a UNESCO World Heritage site at Dunhuang also known as the Thousand Buddha Grottoes. UNESCO says the paintings inside the caves, which depict medieval politics, culture, religion and daily life, have “unmatched historical value.”
Beyond the risk of floods and leaks, the frequent and torrential downpours are now regularly pushing humidity in the Mogao Caves above safe thresholds for preservation, according to the report.
Water vapor levels above 60 percent of saturation cause salt to crystallize and separate on the cave walls in ways that can dislodge paint. Murals dating back as far as the 4th century are flaking away at an accelerated pace, the research found.
The Buddhist paintings and sculptures in the caves, located just beyond the end of the Great Wall of China in the far western reaches of the Gobi Desert, provide some of our best clues to the thriving exchange of goods and ideas that made up the ancient Silk Road.
For a millennium starting in the 4th century, traders and travelers met in grottoes carved into cliffs near the Dunhuang oasis, leaving behind artwork that was preserved thanks to the desert climate.
But the region’s summers are no longer so calm or dry.
In the Jinta Temple Grotto, over 300 miles from the Mogao Caves, atmospheric humidity levels reached as high as 93 percent during a severe downpour in August of last year. At these levels, decomposition, rot and erosion become difficult to avoid.
Since then, a crack has developed in the main pillar in the middle of the grotto, allowing water to seep inside at times of heavy rain.
In recent years, public awareness of extreme weather has grown rapidly in China as deadly floods and record heat waves have brought home the dangers of a changing climate.
The Chinese government has positioned itself as being proactive in tackling the problem, pledging to peak carbon dioxide emissions before 2030 and to reach “carbon neutrality” by 2060. But environmental activists remain concerned about Beijing’s slow progress in quitting coal power.
How to speed up China’s transition toward renewable energy is likely to be top of U.S. climate envoy John F. Kerry’s agenda during a three-day visit to Beijing that began Sunday.
The danger to cultural heritage from extreme weather has only just begun to seep into China’s climate debate.
Efforts to protect the Gansu grottoes have been ongoing for decades, but it is only recently that research has begun to consider how a rapidly changing climate could make conservation harder.
Gansu’s famed status as the “home of Chinese grotto art” has made it a priority for conservationists. Within Chinese history and archaeology, the murals, temples and statues have an importance comparable to the ruins of ancient Egypt or other great treasures of the ancient world.
A vast project of scanning and photographing relics is underway to allow 3D re-creations and virtual reality tours.
This long-established work makes the Dunhuang caves some of the best-prepared sites to survive a shifting climate. The use of advanced sensors and environmental controls is part of the reason it is possible for researchers such as Greenpeace to measure the effects of extreme weather.
More than almost any other place in China, aside from the Forbidden City in Beijing, the caves have benefited from decades-long collaborations between experts from around he world and the Dunhuang Academy, which manages research and conservation for sites across Gansu.
The Getty Conservation Institute, a Los Angeles-based nonprofit, has worked with local experts for decades to protect and record archaeological findings in the region. One of the most recent developments in that collaboration is the adoption of an open-source inventory platform developed by Getty, called Arches.
“Arches allows a big-picture view of that situation across all these sites, which should allow them to see things like trends in conditions and then also proactively to prioritize interventions,” said David Myers, a senior project specialist at Getty.
Because of Getty’s open-source software, the Dunhuang Academy “made changes that no one else had done” by incorporating data from monitors to measure the flow of visitors, carbon dioxide levels and humidity, Myers said.
Other historical sites across China are less prepared to respond to climate change. “There are hundreds of less-funded, less-studied sites all around China that are facing these same risks,” said Li of Greenpeace.
The discovery, classification and preservation of ancient history are of particular importance to Xi Jinping, China’s leader, who has called for the creation of “archaeology with Chinese characteristics” and sought to frame the Chinese Communist Party as the natural inheritor of ancient Chinese civilization.
China is in the process of conducting a nationwide survey to build an up-to-date database of historical artifacts over three or four years. Environmental activists and conservationists say the project is an opportunity to extend research on the threat of extreme weather and best practices for combating it at other sites.
When extreme rainfall and flooding hit northern Shanxi province in October 2021, Chinese media reported that at least 1,763 historical sites were affected, including the Yingxian wooden pagoda, the oldest of its kind in China.
Nearly 1,000 miles to the southeast of Dunhuang, carved into a cliff face at the other end of the Gansu corridor, are the grottoes of Maijishan. From afar, they appear like a giant haystack — the name literally means “hill of stacked wheat” — but the sheaflike structures no longer have the luxury of drying out in the summer sun.
High humidity was found to have caused seriously harmful bacterial and other deterioration in the walls of some of the site’s caves, according to research published last year by Northwest University in Xian. In the caves numbered 32 and 127, more than half of the murals had fallen off.
Given the huge number of cultural artifacts at risk and the unpredictable nature of climate change, sometimes the best — maybe only — option is to prepare for the worst to ensure as little ancient history as possible is lost.
“You need to take the best science and you do scenario planning. You play out how you would respond in all of them just so that you’re prepared,” Myers of the Getty Conservation Institute said.
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