AsianScientist (Nov. 12, 2021) – Over the past two millennia, Imperial China had witnessed successive cycles of dynastic rulers facing invasion, rebellion and other social unrest. But as it turns out, environmental stressors like volcanic eruptions also repeatedly caused these dynasties to collapse, reported an international team in Communications Earth & Environment.
When a volcano erupts, its potentially destructive consequences extend beyond spewing lava and ash that could bury towns, just like Pompeii in Ancient Rome. In the long run, climate patterns are susceptible to the volcanic emissions that blanket the air. These particles of primarily sulfur dioxide gas can scatter sunlight and reduce water evaporation leading to less rainfall.
As temperatures drop abruptly and drought takes over the landscape, such climate stress can cause agricultural damage and livestock death. However, systematically characterizing how volcanism contributes to societal collapse has proven difficult, especially since many catastrophes are one-off events lacking evidence applicable throughout history.
Given China’s extensive dynastic history, diving into this 2,000-year cycle of rising and falling societies could uncover insights into the impacts of explosive volcanism on civilizations.
Led by researchers from Zhejiang University in China and Trinity College Dublin in Ireland, an international team investigated these human-environmental dynamics using precise historical records and volcanic dating from sulfur deposits on ice cores.
Out of 68 collapse cases, 62 of them were preceded by volcanic eruptions within a 10-year timeframe. To check whether these observations were due to chance, the researchers tested different timing windows and compared the historical patterns with computer simulations of randomly distributed collapse events.
Strikingly, the number of eruptions remained higher than expected in the original timing window, showing that volcanic explosions and climatic shocks played a repeated and long-term role in the downfall of China’s dynasties. In this complex relationship, some dynasties survived for up to a decade before succumbing, while others fell very rapidly after the eruption.
When dynasties were already under a lot of unrest, such as warfare, the team found that smaller volcanic events became the ultimate or final triggers of collapse. Meanwhile, sufficiently large volcanic explosions acted as more fundamental causes of collapse even with only low pre-existing stress.
Compared to what past Chinese dynasties endured, eruptions in recent history have been smaller in scale, but future major explosions could drastically impact communities, especially marginalized populations and those reliant on agriculture.
The researchers believe their findings emphasize the need to prepare for future eruptions, especially in areas with low climate resilience arising from conflict or other stressors.
“This study highlights the inadequacy of monocausal or environmentally deterministic explanations of collapse, but also of traditional historical explanations that exclude environmental agency,” the authors wrote. “Volcanically induced climatic shock should now take a prominent place among and be integrated with the constellation of factors frequently assigned a role in these events.”
The article can be found at: Gao et al. (2021) Volcanic climate impacts can act as ultimate and proximate causes of Chinese dynastic collapse.
Source: Zhejiang University; Photo: Shutterstock.
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