Millions at Risk as Nearly Half of Major Chinese Cities Are Sinking, Study Warns

A new study has found that nearly half of China’s major cities, including Beijing and Tianjin, are sinking due to water extraction and the increasing weight of urban buildings and infrastructure. The research, published in the journal Science, revealed that 45% of China’s urban land is sinking at a rate faster than 3 millimetres per year, with 16% subsiding at a rate of over 10 millimetres per year. The study, which examined 82 cities, highlighted that some cities are subsiding rapidly, with one in six exceeding 10mm per year. Beijing was identified as sinking 45 millimetres annually near its subways and highways.

The researchers attributed the subsidence to factors such as groundwater withdrawal and the weight of buildings, as rapid urban development has led to high-rise buildings, expanding road systems, and a swift increase in groundwater usage. The scientists also identified natural factors, such as the geological setting of each city and the depth of the bedrock, as influencing the amount of weight the ground could hold up without sinking. Furthermore, they found a strong link between sinking cities and groundwater loss, which results in compacted empty pore space in the crust as weight accumulates above. The researchers emphasized the need for long-term, sustained control of groundwater extraction to address China’s city subsidence.

They also highlighted the potential consequences of subsidence, including jeopardizing the structural integrity of buildings and critical infrastructure, as well as exacerbating the impacts of climate change in terms of flooding, particularly in coastal cities where it reinforces sea-level rise. Robert Nicholls, a professor of climate adaptation at the University of East Anglia in the UK, underscored the importance of a national response to address the issue. He cautioned that the findings reinforce the need for action even in other susceptible cities outside China.