A new study published in the journal Science warns that land subsidence driven by human activities poses a significant risk to China's coastal areas, leading to increased flooding and rising sea levels. The research indicates that almost half of China's urban regions, encompassing 29% of the country's population, are sinking at a rate exceeding 3 millimeters (0.12 inches) per year, affecting approximately 270 million people.

Furthermore, the study highlights that 67 million individuals are residing in areas where the land subsides faster than 10 millimeters (0.4 inches) annually. Experts attribute this alarming phenomenon primarily to excessive groundwater extraction. China's cities have been drawing water from underground aquifers at a faster pace than nature can replenish, exacerbating the problem through climate change-induced droughts. Moreover, the weight of the expanding urban centers themselves contributes to the subsidence, as the soil compresses under the accumulated sediments and the pressure exerted by heavy buildings.

While land subsidence is not unique to China, the study emphasizes that it is a global concern. For instance, in the United States, several coastal cities, including New York City, are experiencing sinking. The Netherlands has witnessed a sinking of approximately 25% of its lands below sea level, and Mexico City holds the title of the world's fastest subsiding city, with land sinking up to 50 centimeters (nearly 20 inches) per year.

The combination of land subsidence and rising sea levels is particularly worrisome along China's coasts, exposing more land, people, and property to devastating flooding. The study predicts that about a quarter of China's coastline will be below sea level due to subsidence and projected sea level rise, posing severe threats and endangering lives. Notably, Tianjin, Shanghai, and areas surrounding Guangzhou are identified as significantly vulnerable to both issues.

Nevertheless, some coastal regions in China have already implemented physical safeguards to combat the growing risk of inundation. For example, Shanghai has constructed impressive dike systems that stand several meters tall, reducing the risk of flooding resulting from land subsidence and sea level rise.

Experts acknowledge that subsidence is not solely a coastal problem but affects urban cities as well. Leonard Ohenhen, a doctoral researcher at Virginia Tech who recently conducted a study on land subsidence in the US, commends the study as "scientifically robust" and emphasizes that land subsidence is prevalent in many urban centers, often surpassing the rates observed in coastal cities.

The Chinese government has initiated several measures to address the issue, including implementing strict laws to regulate groundwater pumping and limiting withdrawals in Shanghai and its surrounding areas. Additionally, China has launched a project to transfer water from the Yangtze River in the south to the water-scarce northern regions, such as Beijing, effectively reducing the need for excessive groundwater extraction and alleviating land subsidence in the capital.

Tao Shengli, co-author of the study and a professor at Peking University, expressed confidence in the government's efforts and highlighted the importance of continued control over groundwater withdrawals in major cities and the maintenance of coastal dike systems.

As the threat of land subsidence grows, there is an urgent need for proactive measures to mitigate its consequences. The study serves as a wake-up call, prompting authorities and communities to take concrete actions to protect vulnerable areas and ensure sustainable urban development in the face of this pressing challenge.