Millions at risk as nearly half of China’s major cities are sinking, study warns.

A new study has found that nearly half of China’s major cities are sinking, with Beijing sinking 45 millimetres annually. The research, published in the journal Science, revealed that Chinese cities, including Beijing and Tianjin, are facing a “moderate to severe” risk of subsidence. The study examined 82 cities and found that 45% of China’s urban land was sinking faster than 3 millimetres per year, with 16% at a rate of over 10 millimetres per year. Some cities were found to be subsiding rapidly, with one in six exceeding 10mm per year.

Factors contributing to this subsidence include groundwater withdrawal and the weight of buildings. Rapid urban development, including the construction of high-rise buildings and expansive road systems, has also had an impact. The researchers emphasized the need for sustained control of groundwater extraction to address the issue. The study also identified natural factors such as the geological setting of each city and the depth of the bedrock as contributing to subsidence.

Groundwater loss was found to be strongly linked to sinking cities, leading to compacted crust as weight piles on above. The consequences of city subsidence are significant, jeopardizing the structural integrity of buildings and critical infrastructure. It also exacerbates the impacts of climate change, particularly in coastal cities where it reinforces sea-level rise. In light of these findings, researchers emphasized the need for a national response to address city subsidence, and emphasized that the issue is not limited to China, cautioning that other susceptible cities outside of China also need to be considered.