China’s Sinking Cities: The Rising Threat of Subsidence

In a study that was published in the journal Science, the authors discovered that more than three millimeters of sinking had occurred in 45 percent of China’s urban terrain.

TFD – Discover the escalating threat of subsidence in China’s largest cities due to urbanization and population growth. Learn about the significant risks posed by sinking land and the urgent need for measures to address this environmental challenge.

Singapore — According to a study of nationwide satellite data released on Friday, over half of China’s largest cities are experiencing “moderate to severe” levels of subsidence, placing millions of people at risk of floods, especially as sea levels rise.

In a study published in the journal Science, the scientists discovered that the weight of the built environment combined with falling water levels was causing 45% of China’s urban terrain to sink more quickly than 3 millimeters per year, and 16% more quickly than 10 mm per year.

The South China Normal University’s Ao Zurui led research team stated that “even a small portion of subsiding land in China could therefore translate into a substantial threat to urban life” given that China’s urban population already exceeds 900 million people.

Over 7.5 billion yuan ($1.04 billion) in losses are already incurred by China each year due to subsidence, and in the next century, almost 25% of coastal land may really be below sea level, increasing the risk of flooding for hundreds of millions of people.

Robert Nicholls of the University of East Anglia’s Tyndall Centre for Climate Change Research said, “It really brings home that this is for China a national problem and not a problem in just one or two places.” “And it is a microcosm of global events occurring elsewhere in the world.

Among the worst-hit was Tianjin, a metropolis in northern China with a population of almost 15 million. A “sudden geological disaster” that occurred last year forced 3,000 residents to flee, with investigators blaming both the installation of geothermal wells and water shortages for the event.

Overmining has also caused damage to several of China’s historic coal areas, forcing authorities to strengthen the soil by pouring concrete into the collapsing pits.

The issue is not specific to China. An other research that was released in February estimated that 2.4 million square miles of land worldwide were in danger. Indonesia is one of the worst-hit nations; a sizable portion of Jakarta, the nation’s capital, is currently below sea level.

According to Nicholls, Tokyo, which sank by roughly 16 feet before outlawing groundwater extraction in the 1970s, might serve as a model for other vulnerable cities.

“It’s important to consider subsidence mitigation, but it can’t be completely stopped, so adaptation and dyke construction are necessary,” he continued.

30 of the 44 significant coastal cities affected by the issue were in Asia, per a Singapore study from 2022.

According to University of Rhode Island geophysics specialist Matt Wei, “it is a problem of urbanization and population growth—larger population density, more water extracted, and more subsidence.”