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Chinese Cave Graffiti Contains 500 Years of Climate Data

For the first time, researchers find a direct link between historical cave inscriptions and geochemical records.
This is an inscription from 1891 found in Dayu Cave. Image: L.Tan

An international team of researchers have discovered a cave that contains inscriptions detailing the crippling effects of climate change on a region.

In a study published today in the journal Scientific Reports, a team of researchers from the UK and China describe finding inscriptions on the walls of the Dayu Cave in the Qinling Mountains of central China that date back to between 1520 and 1920. The inscriptions detail the impact of droughts on the society, politics, and economy of the region, and they correlate with geochemical data gleaned from an analysis of the cave's interior. This allows the researchers to cross-reference and check their geochemical data with real records left behind by humans.


"This is the first time we have direct historical evidence [of climate change] from the same place (inside the cave) to compare the geochemical information with," Sebastian Breitenbach, a researcher at the University of Cambridge's Department of Earth Sciences, told me. "What's cool about this is that we've never seen a cave where people actually wrote that it was drier than usual, which caused cannibalism or people migrating to different places, or not trusting their political systems or leaders anymore."

The researchers used mass spectrometry (a chemistry technique that analyses the amount and type of chemicals in samples) to analyse the ratios of stable isotopes of oxygen, carbon, and other elements within the cave deposits. Climate change is known to affect all of these elements within caves, and the researchers found that higher carbon and oxygen isotope ratios corresponded with lower rainfall levels. They cross-referenced these findings with the writings discovered on the walls, and found a strong link between the two. For example, cave deposits from the late 1800s that provided evidence for drought in the region corresponded with the written records on the cave.

Inside the cave. Image: L.Tan

One such inscription states: "On May 24th, 17th year of the Emperor Guangxu period (June 30th, 1891), 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 a ceremony."

"There are examples of things like human remains, tools, and pottery being found in caves, but it's exceptional to find something like these date inscriptions," said Liangcheng Tan, the study's lead author from the Institute of Earth Environment at the Chinese Academy of Sciences, in a press statement.

The researchers believe that though this is the first discovery of cave writings detailing the impact of climate change in China, there may well be more discoveries like it in the future.

They also modelled a prediction of what the climate could look like in the region in 2030, based on their results. Breitenbach said that their models showed a likelihood of longer and more intense droughts in the coming years in the region, and said that it was therefore important to implement a strategy to deal with this environmental shift.

"The Qinling Mountains are a habitat for the panda, which is an iconic animal for the Chinese, and of course they'll want to do everything they can to save it from extinction," he said. "So it's important to understand what the climate change will be like in that region, and think of ways in which we can mitigate it, so that we can make it easier for animals and humans."