A comprehensive study published in the journal Science has uncovered alarming trends of land subsidence in China’s major cities, with Beijing sinking at a rate of 45 millimeters annually. The research highlights the significant risks posed by water extraction and the increasing weight of urban infrastructure, contributing to a “moderate to severe” risk of subsidence in many urban areas across the country.
The study, conducted over the period from 2015 to 2022, examined land subsidence in every Chinese city with a population exceeding 2 million. Of the 82 cities analyzed, nearly half were found to be sinking faster than 3 millimeters per year, with 16% experiencing subsidence rates exceeding 10 millimeters per year. Notably, Beijing, along with other major cities like Tianjin, faces particularly acute risks of subsidence.
Researchers attribute the subsidence phenomenon to a combination of factors, including groundwater withdrawal and the weight of burgeoning urban structures. The proliferation of high-rise buildings, expansion of road systems, and intensive groundwater usage have collectively contributed to the destabilization of urban land.
Natural factors, such as the geological composition and depth of bedrock, also play a significant role in exacerbating subsidence risks. Groundwater loss, which results in the compaction of empty pore spaces in the earth’s crust, further compounds the problem, particularly in areas where weight is concentrated.
Urban transportation networks, hydrocarbon extraction, and mining activities have additionally been identified as contributing factors to land subsidence. However, researchers underscored that sustained control of groundwater extraction could be pivotal in addressing the underlying causes of subsidence.
The implications of subsidence extend beyond structural concerns, posing significant challenges to critical infrastructure and exacerbating the impacts of climate change, particularly in coastal cities vulnerable to flooding. Robert Nicholls, a climate adaptation expert at the University of East Anglia, emphasized the urgent need for a national response to mitigate the risks associated with subsidence.
As the study’s findings underscore the widespread nature of the subsidence problem, researchers cautioned that proactive measures are essential not only within China but also in other susceptible cities globally. The study serves as a clarion call for concerted efforts to address the multifaceted challenges posed by land subsidence and safeguard against its potentially devastating consequences.
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