An ancient cave in China was covered with drawings that revealed a history of severe droughts, but the findings also unearthed some ominous future weather forecasts for the country.
Researchers have discovered that the inscriptions on the walls of Dayu Cave in the Qinling Mountains of central China describe the impacts of seven droughts between 1520 and 1920. According to a press release, these unique inscriptions, as well as a chemical analysis of cave formations, told an unsettling story of both the past and the future.
According to the cave drawings, people would come to the cave both for water and to pray for rain in times of drought. The cave inscriptions are described in the journal Scientific Reports, and one 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.”
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While the writings may sound relatively mild and matter-of-fact, the droughts certainly didn’t bring about tranquil reactions. The droughts of the 1890s led to severe starvation and social instability, triggering fierce conflict between the government and civilians. The earlier droughts, namely the one in 1528, also led to widespread starvation, and there were even reports of cannibalism. These ancient days of drought were times of strife and desperation.
However, what may be most disconcerting about the discovery is the worrisome predictions for China’s future that lay hidden in the stalagmites of Dayu Cave for all this time. Researchers analyzed the stalagmites, formed by dripping water, which contain rings that record their growth, just like trees. The scientists measured the different elemental forms (“isotopes”) of oxygen, carbon, uranium and others, comparing each ring to the recorded rainfall for the corresponding year. In recent years with lower rainfall, there were higher oxygen and carbon isotope ratios in the stalagmites.
Based on this pattern, the scientists were able to determine how much rain had fallen up to 500 years ago, long before meteorologists kept records. But they were also able to construct a model of precipitation in the region to predict future droughts. The model is consistent with a major drought in the 1990s and predicts another one to come in the late 2030s. Unfortunately, the region may be in for more serious droughts in the future.
“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,” said Dr Liangcheng Tan of the Institute of Earth Environment at the Chinese Academy of Sciences, and the paper’s lead author. “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.”
While humans today certainly have more advanced technologies to combat times of drought than our ancient ancestors in the 1500s to early 1900s, it’s not only Homo sapiens who are affected by droughts. The stunning Qinling mountains are home to many endangered species, including the treasured giant panda. The area also provides the resources needed to maintain two larger water projects, so it’s essential to explore how the region can adapt to times of drought.
Dr Sebastian Breitenbach of Cambridge’s Department of Earth Sciences, one of the paper’s co-authors, says, “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.”
