An international team of researchers have made a discovery on the walls of a cave in central China. What they found was “graffiti” on the walls that describes the effects that droughts had on the local population over the last 500 years.
The findings were published in Scientific Reports.
It’s the first time an on-site comparison of historical and geological records from one cave has been possible.
The information that was contained in the inscriptions, along with a detailed chemical analysis of stalagmites in the cave, together painted a picture of how societies were affected by droughts over time.
In a statement from the University of Cambridge, it wrote: “The inscriptions were found on the walls of Dayu Cave in the Qinling Mountains of central China, and describe the impacts of seven drought events between 1520 and 1920. The climate in the area around the cave is dominated by the summer monsoon, in which about 70% of the year’s rain falls during a few months, so when the monsoon is late or early, too short or too long, it has a major impact on the region’s ecosystem.”
“There are examples of things like human remains, tools, and pottery being found in caves, but it’s exceptional to find something like these dated inscriptions,” lead author Liangcheng Tan, from the Institute of Earth Environment at the Chinese Academy of Sciences, said.
The 2-kilometer-long (1.2-mile-long) Dayu Cave is located on the southern slope of the Qinling Mountains. “Combined with the evidence found in the physical formations in the cave, the inscriptions were a crucial way for us to confirm the link between climate and the geochemical record in the cave, and the effect that drought has on a landscape,” Tan adds.
According to IFL Science: “Slicing open cave formations called speleothems (pictured below) reveals a series of layers, a record of their yearly growth. The team removed sections of speleothems, including stalagmites, to analyze the isotopes and elements within. Climate changes and moisture levels affect the concentrations of various elements, and higher oxygen and carbon isotope ratios correspond with lower rainfall levels.
“They found that concentrations of certain elements were strongly correlated to periods of drought. Dayu Cave’s chemical profile was then cross-referenced with the inscriptions on the walls. These inscriptions describe the impacts of seven drought events that occurred between 1520 and 1920. That’s when locals went to the cave to retrieve water and to pray for rain,” IFL added.
Dr Sebastian Breitenbach of Cambridge’s Department of Earth Sciences, one of the paper’s co-authors, said: “In addition to the obvious impact of droughts, they have also been linked to the downfall of cultures—when people don’t have enough water, hardship is inevitable and conflict arises.”
“In the past decade, records found in caves and lakes have shown a possible link between climate change and the demise of several Chinese dynasties during the last 1800 years, such as the Tang, Yuan, and Ming dynasties,” he added.
According to the inscriptions in Dayu Cave, residents would come to the cave both to get water and to pray for rain in times of drought. An inscription from 1891 reads: “On May 24th, 17th year of the Emperor Guangxu period, Qing Dynasty, the local mayor, Huaizong Zhu, led more than 200 people into the cave to get water. A fortune-teller named Zhenrong Ran prayed for rain during the ceremony.”
Another inscription from 1528 reads: “Drought occurred in the 7th year of the Emperor Jiajing period, Ming Dynasty. Gui Jiang and Sishan Jiang came to Da’an town to acknowledge the Dragon Lake inside in Dayu Cave.”
While the inscriptions are business-like in tone, the droughts of the 1890s led to severe starvation and triggered local social instability, which eventually resulted in a fierce conflict between the government and civilians in 1900. The drought in 1528 also led to widespread starvation, and there were even reports of cannibalism, according to EurekAlert.
“Since the Qinling Mountains are the main recharge area of two larger water transfer projects, and the habitat for many endangered species, including the iconic giant panda, it is imperative to explore how the region can adapt to declining rain levels or drought,” said Breitenbach. “Things in the world are different from when these cave inscriptions are written, but we’re still vulnerable to these events—especially in the developing world.”
It is an amazing find, and gives a lot of insight into the history of China.