Satellite Data Reveals Sinking of Nearly Half of China’s Major Cities
A recent study published in the journal Science indicates that nearly half of China’s large cities are experiencing sinking land, posing flood risks to millions of residents.
The research revealed that 45% of China’s urban areas are sinking at a rate exceeding 3 mm per year, with 16% sinking more than 10 mm annually.
Satellite Radar Analysis of 82 Chinese Cities Reveals Ground Disturbances
The researchers examined 82 Chinese cities with populations exceeding 2 million, utilizing satellite radar pulses to detect variations in the distance between the satellite and the ground.
They assessed the changes in city elevations from 2015 to 2022.
The study revealed that Shanghai, China’s largest city, continues to sink, having already subsided approximately 3 meters over the past century.
Cities like Beijing and Tianjin also showed significant impacts from the sinking phenomenon.
Reasons
Several factors contribute to the subsidence, but Robert Nicholls, a climate adaptation professor at the University of East Anglia who was not part of the study, told the BBC that he believes water extraction is likely the main cause.
“Many people in China reside in regions that were recently sedimented in geological terms. When groundwater is extracted or soils are drained, they often sink,” he explained.
The study also proposed that a potential solution to the problem “may involve sustained, long-term management of groundwater extraction.
In a commentary also featured in Science, Nicholls cautioned that “subsidence threatens the stability of buildings and essential infrastructure, amplifying the impacts of climate change, especially flooding in coastal cities, where it intensifies sea-level rise.”
Reuters reported that subsidence already costs China over 7.5 billion yuan, approximately $1.05 billion, annually.
However, this issue is not exclusive to China.
Global Study Highlights 6.3 Million Square Kilometers of Land at Risk of Subsidence, with Indonesia Facing Significant Impa
A separate study published in February indicated that about 6.3 million square kilometers, or roughly 2.4 million square miles, of global land is susceptible to subsidence, with Indonesia being one of the hardest-hit nations.
In the US, over 17,000 square miles across 45 states have been directly impacted by subsidence, according to the United States Geological Survey (USGS).
The USGS states that over 80% of identified subsidence cases in the US are attributable to the overuse of groundwater.
“The growing development of land and water resources risks worsening current land subsidence issues and triggering new ones,” the statement concludes.
Read the original article on: Science Alert
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