According to a recent study, water extraction and the weight of urban infrastructure and buildings are causing nearly half of China’s major cities to skink. The study, which was published in the journal Science, found that Beijing and Tianjin, among other Chinese cities, are at “moderate to severe” risk of subsidence. The study found that 45% of China’s urban land was sinking more quickly than 3 millimeters annually, and 16% more quickly than 10 millimeters annually.
In every Chinese city with a population of more than two million, scientists measured land subsidence between 2015 and 2022 for the study. The researchers discovered that some of the 82 cities they looked at are rapidly subsiding—one in six of them more than 10 mm annually. Additionally, they discovered that Beijing is sinking 45 millimeters a year close to its highways and subways, while Shanghai, the largest city in China, is still subsiding after sinking up to 3 meters over the previous century.
“The subsidence appears to be associated with a range of factors such as groundwater withdrawal and the weight of buildings,” the researchers wrote in the study, as per Live Science. “High-rise buildings are sprouting up, road systems are expanding, and groundwater is being used, all at a rapid pace,” they explained.
“In addition to the national pattern of city subsidence, we identified several natural and human factors that were associated with city subsidence,” the team wrote in the study. The natural factors include the geological setting of each city and the depth of the bedrock, which influenced the amount of weight the ground could hold up without sinking. The scientists also found a strong link between sinking cities and groundwater loss, which leaves empty pore space in the crust that becomes compacted as weight piles on above.
Other factors, according to research, include urban transportation networks, as well as hydrocarbon extraction and mining. But “the key to addressing China’s city subsidence could lie in the long-term, sustained control of groundwater extraction,” the researchers emphasised.
“Subsidence jeopardizes the structural integrity of buildings and critical infrastructure and exacerbates 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 said in a statement.
Researchers cautioned that the new findings reinforce the need for a national response even in other susceptible cities outside China.
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