Almost half of China’s big cities are sinking

The risk of flooding also increases considerably with rising sea levels, which is largely caused by climate change. The study was published in the journal Science Friday, and is based on nationwide satellite data from China.

According to the study, 45 percent of China’s urban areas are sinking by more than 3 millimeters a year, while 16 percent are sinking by more than 10 millimeters a year, according to Reuters. China’s capital Beijing and the metropolis Shanghai are among the cities affected.

Rising sea levels also pose a major risk to the metropolis of Hong Kong.

The development is not only driven by declining levels of groundwater, but also the tremendous weight of the infrastructure in the cities. Chinese cities are also far larger than European cities.

Threat of flooding

A total of over 900 million people live in the Chinese cities, so even a small subsidence in the land area can pose a significant threat to city life, according to the researchers at South China Normal University.

The fact that the cities are sinking is already costing China over 7.5 billion yuan annually, corresponding to over 11.4 billion Norwegian kroner.

In the next century, there is a risk that almost a quarter of the Chinese coastal areas will actually be lower than sea level, which drastically increases the risk of flooding.

– It makes it clear that this is a national problem for China, and not a problem that only applies to one or two places, says researcher Robert Nicholls at the University of East Anglia.

Geological disaster

The northern Chinese city of Tianjin, home to more than 15 million people, has been identified as the place hardest hit by the subsidence.

Last year, 3,000 residents were evacuated from the city following a “sudden geological disaster”, which investigators believed was caused by a lack of groundwater and the construction of geothermal wells.

Many of China’s old coal districts are also suffering from over-mining, and the authorities have often had to inject concrete into the crumbling shafts to reinforce the surrounding lands.

Not just in China

The fact that land areas are shrinking is not just a problem in China. A separate study published in February shows that around 6.3 million square kilometers of land across the globe are at risk.

Indonesia is among those hardest hit, and large parts of the Indonesian capital Jakarta are already below sea level. In the last 25 years, parts of the city have sunk by more than 4.8 metres, according to the report Bloomberg.

The big city of New York in the USA is also on the list of declining cities.

However, of 44 coastal cities suffering from the problem, 30 were in Asia, according to a study from Singapore in 2022. Overpopulation and large urban development are pointed to as some of the biggest risk factors.