Chinese cities are experiencing rapid growth with towering skyscrapers and massive buildings emerging in every corner. However, a new study has revealed an unpleasant surprise for the Chinese. The recent research indicates that Chinese cities are sinking, with estimates showing that 16% of major cities in the country are losing more than 10 mm in elevation annually. Nearly half of them lose more than 3 mm per year, according to a new study published in the journal Science. Although these numbers may seem small, they accumulate quickly; within 100 years, a quarter of China's urban coastal land could be below sea level due to a combination of subsidence and rising sea levels, according to the study.
**The Weight of Buildings**
The study also found that the subsidence in these cities is partly due to the enormous weight of buildings and infrastructure. Pumping water from groundwater aquifers beneath the cities plays a role as well, along with oil drilling and coal extraction, all activities that leave empty space underground where soil and rock can compact or collapse.
The new study relied on radar measurements from satellites assessing how the Earth's surface in 82 major cities, representing three-quarters of the urban population in China, moved up or down between 2015 and 2022. Researchers compared these measurements with data on potential contributing factors such as the weight of buildings in these cities and changes in groundwater levels beneath them. They also integrated subsidence measurements with sea level rise projections to determine which cities might end up below sea level.
One of the warnings related to these results is that they assumed a constant rate of subsidence over the next hundred years, but these rates could change with human activity. Currently, about 6% of land in coastal cities in China is at a relative level below sea level. The study found that if the global average sea level rises by 0.87 meters, or just under 3 feet, by 2120 (the higher of the two common scenarios considered by researchers), this percentage could rise to 26%.
