A significant portion of China is at risk from land subsidence, a phenomenon where the ground sinks due to factors like groundwater withdrawal and heavy urban development. Researchers from Virginia Tech and the University of East Anglia reported that if preventative measures are not taken, the consequences could be severe. The findings appeared in a reputable scientific journal after a comprehensive analysis of satellite data and city development patterns.
The study examined satellite imagery from 82 Chinese cities, collectively home to roughly 700 million people. It found that nearly half of the urban areas studied reside in zones prone to subsidence. Projections suggest that, by 2120, the land below the water table in these cities could shrink further, potentially affecting between 55 and 128 million residents. This would threaten buildings, infrastructure, and coastal defenses, increasing flood risk in key urban centers. Hotspots identified include Beijing and Tianjin, while Shanghai among the largest cities has already experienced substantial sinking in the last century, approaching several meters in cumulative ground loss.
Coastal megacities are especially vulnerable. As land subsidence compounds sea-level rise, the risk to coastal populations grows, a pattern echoed in historic events such as the flood repercussions faced by New Orleans after Hurricane Katrina in 2005. These connections highlight how subsidence interacts with climate-related factors to magnify urban exposure to floods and high tides.
Human activity is widely cited as the primary driver of subsidence. Extracting groundwater, especially at city scales, can lead to the ground losing support and compacting. In other parts of the world, including Osaka and Tokyo, authorities implemented measures in the 1970s that slowed or halted subsidence by reducing groundwater pumping and improving land use planning. Additional contributing factors include vibrations from tunnel construction and heavy traffic, which can accelerate soil compaction in certain areas. Yet natural geological processes generally play a smaller role compared with the footprint of human activity. Evidence from Beijing shows faster subsidence in subway and major roadway corridors, underscoring how infrastructure development can shape regional ground loss.
The broader global picture indicates that land subsidence poses a challenge for cities worldwide. The researchers emphasize the need for a shift in focus from simply measuring the pace of subsidence to actively pursuing practical solutions. They urge policymakers, engineers, and scientists to collaborate on strategies that reduce groundwater extraction, strengthen building codes, improve urban water management, and protect vulnerable coastlines from flooding and saltwater intrusion. This calls for integrated planning that aligns water resources, land use, and climate resilience in urban design.
Earlier assessments noted that roughly two billion people live in regions affected by subsidence-like conditions. Current estimates continue to stress the importance of vigilance and proactive planning to minimize risks and protect urban populations as cities adapt to changing environmental conditions and accelerating development pressures.