Located in the Yangtze River Delta, about 160 km southwest of Shanghai, are the ruins of Liangzhucheng, where an advanced culture flourished around 5,300 years ago thanks to the engineering technology of large-scale hydraulic structures.
The walled city contained a complex system of navigable canals, dams and reservoirs that allowed for the year-round cultivation of very large tracts of land. It is one of the first examples in the history of human civilization of a highly developed community based on a water infrastructure.
And they did it all without metal.
Long undiscovered, the ruins are now considered a well-preserved record of Chinese civilization more than 5,000 years ago, and were listed as a UNESCO World Heritage Site in 2019. But the city’s advanced civilization came to an abrupt end.
“Thin clay layers were found in the preserved remains, which suggest a possible connection between the collapse of an advanced civilisation and floods on the Yangtze River, or perhaps the East China Sea. We found no evidence of a man-made cause, such as a war or other conflict,” explains Christoph Spotl of the University of Innsbruck.
The Shennong Cave (pictured) and the Jiulong Cave Droplets provide a glimpse into the period of the collapse of the Liangzhu culture, around 4,300 years ago. Photo by Zhang Haiwei
Dripstone stores the answers
Caves and their deposits, such as granite deposits, are among the most important climatic records in existence. They allow us to reconstruct the climatic conditions above the caves up to hundreds of thousands of years ago. As the cause of the sudden collapse of the Liangzhu culture is still unclear, the research team searched for suitable records to investigate possible climatic causes of this collapse.
Zhang Haiwei, a geologist at Xi’an Jiaotong University in Xi’an, collected stalagmite samples from two caves southwest of the excavation site, the Shennong Cave and the Jiulong Cave.
The stalagmite data indicates that there was a period of extremely high precipitation between 4345 and 4324 years ago. Evidence for this was provided by carbon isotope records measured at the University of Innsbruck. Precise dating was performed by uranium-thorium analysis at Xi’an Jiaotong University, with an accuracy of ±30 years.
Heavy monsoon rains probably caused such severe flooding on the Yangtze River and its tributaries that even sophisticated dams and canals could not withstand the volume of water, destroying the city of Liangzhu and forcing its people to evacuate. The extremely humid climatic conditions, as geologists have shown from the cave data, continued off and on for the next 300 years.
Citation: Haiwei Zhang, Hai Cheng, Ashish Sinha, Christoph Spötl, Yanjun Cai, et al. Climate change leads to collapse of Liangzhu and other Neolithic cultures in the Lower Yangtze River Basin. Advanced Science2021 DOI: 10.1126/sciadv.abi9275
