Research shows that 1/3 of Chinese city population is at high risk of city siking

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Scientists from the University of East Anglia (UEA) and Virginia Tech emphasize addressing land subsidence as a significant urban hazard, particularly in climate change and sea-level rise. Their commentary in Science highlights a new research paper that uses satellite data to map land movement across 82 cities in China, revealing that 45% of these urban areas are experiencing subsidence, with 16% sinking at rates of 10 mm per year or more.

This study, covering cities with a combined population of nearly 700 million, estimates that around 270 million urban residents are affected by subsidence, and about 70 million are experiencing rapid sinking. Major cities such as Beijing and Tianjin and coastal cities like Shanghai are notably impacted. Shanghai has subsided by up to 3 meters over the past century and continues to sink, potentially leading to a tripling of urban areas below sea level by 2120 if current trends continue.

The primary cause of subsidence in these cities is groundwater withdrawal, which lowers the water table and exacerbates sinking. Other factors include geological conditions, building weight, and traffic vibrations. Examples from Osaka and Tokyo show that halting groundwater extraction can significantly reduce subsidence, indicating a viable mitigation strategy.

The scientists argue that while measuring subsidence is a crucial first step, effective solutions require comprehensive models that account for human activities, climate change, and their evolving impacts. They call for transitioning from merely measuring subsidence to understanding its implications and developing strategies with city planners to address these issues. They also emphasize that subsidence is a global problem, not confined to China, and needs broader attention in urban planning and climate adaptation strategies.