China's Sinking Cities: Researchers Warn Of A Looming Threat, Say Half Of Major Cities Are Drowning

In a recent study published in the journal Science, researchers revealed that nearly half of China's major cities are grappling with varying degrees of subsidence, posing a significant threat to millions of residents. The findings shed light on the alarming consequences of declining water tables and the cumulative weight of urban infrastructure. Led by Ao Zurui from the South China Normal University, the study underscores the urgent need for attention to this widespread issue.

The study identified that 45% of China's urban areas are experiencing subsidence exceeding 3 millimetres per year, with a staggering 16% sinking at rates surpassing 10 mm annually. This phenomenon, attributed to both dwindling water resources and the sheer mass of constructed environments, has dire implications for the safety and stability of these cities. With China's urban population already surpassing 900 million, even a fraction of subsiding land poses a significant threat to urban life.

The economic toll of subsidence is substantial, with annual losses already exceeding 7.5 billion Yuan ($1.04 billion). Moreover, projections indicate that within the next century, nearly a quarter of coastal land could dip below sea levels, exposing hundreds of millions to heightened flood risks. Robert Nicholls from the University of East Anglia emphasizes that this issue transcends regional boundaries, mirroring global trends in urban development and environmental degradation.

Among the worst-affected cities is Tianjin, home to over 15 million people, where rapid subsidence has led to alarming incidents. Last year, 3,000 residents were evacuated following a sudden geological disaster attributed to water depletion and geothermal well construction. Additionally, regions with a history of coal mining face compounded challenges, as over-mining has destabilized the land, necessitating interventions such as injecting concrete to reinforce compromised areas.

The repercussions of subsidence extend beyond China, with a separate study highlighting the global extent of the issue. Approximately 6.3 million square kilometres (2.4 million square miles) of land worldwide are at risk, with countries like Indonesia grappling with similar challenges. In Jakarta, significant portions of the capital now sit below sea level.

While mitigation efforts are imperative, experts emphasize the importance of adaptation strategies. Drawing lessons from Tokyo's experience, where strict regulations on groundwater extraction halted subsidence, Robert Nicholls advocates for a multifaceted approach that combines mitigation and adaptation measures. With 30 out of 44 major coastal cities facing subsidence issues in Asia alone, the urgency to address this problem cannot be overstated.

Matt Wei, a geophysics expert at the University of Rhode Island, highlights the underlying factors driving subsidence-urbanization, population growth, and excessive water extraction. Addressing these root causes demands a concerted effort to promote sustainable urban development and prudent resource management practices.

*Inputs from Reuters*