After New York and Tokyo, why Chinese cities are now sinking

Sinking cities are no longer an anomaly. In the United States, major cities like New York and Miami are at risk. In India, the Himalayan city of Joshimath was evacuated as it slowly sank. And now, Chinese cities are facing a similar fate. In less than a century, one-tenth of the Chinese population residing in coastal cities could be living below sea level.

From mining to groundwater extraction to climate change, a variety of factors are responsible. Here’s a deep dive explaining the situation in China (and other parts of the world), its causes, and whether mitigation is possible.

Chinese cities: A sinking ship

A study of nationwide satellite data, published in the Science journal, found that 16 per cent of the mapped area of China’s major cities is sinking faster than 10 millimetres every year. Around 45 per cent of the mapped area is sinking over 3 mm annually.

Regional capital cities like Fuzhou, Hefei, and Xi’an are among the affected areas. Even the national capital, Beijing, is not an exception.

It is a dire situation. According to the study, within a few decades, as much as one-fourth of China’s coastal land could go below sea level.

Population density compounds the threat

The lives of hundreds of millions of people who live in China’s coastal areas would be in danger. Relocating these people would come with extremely high costs. It would also exponentially increase the burden on inland areas or other regions where these people are settled.

China has already seen this play out in Tianjin, one of the worst-hit “sinking cities” in the country. This northern city is home to over 15 million people. In 2023, 3,000 residents, most of whom lived in high-rise apartments, were evacuated after land collapses

China has already seen this play out in Tianjin, one of the worst-hit “sinking cities” in the country. This northern city is home to over 15 million people. In 2023, 3,000 residents, most of whom lived in high-rise apartments, were evacuated after land collapses created large cracks on nearby streets, Reuters reported. Investigators said that water depletion as well as the construction of geothermal wells caused the “sudden geological disaster”.

The factors causing the sinking

Several factors are behind these sinking of China’s coastal cities.

Subsidence: Subsidence is when the ground sinks because underground material, such as rocks, water, oil, mineral resources, or natural gases is removed. In China, declining water tables (due to over-extraction of groundwater), as well as overmining have been largely responsible for subsidence. China currently faces over 7.5 billion yuan ($1.04 billion) in annual losses due to subsidence.

Climate change : Rising temperatures have led to the melting of the polar ice caps. Consequently, sea levels have been increasing. Coastal lands in China and other parts of the world are slowly succumbing to the rising waters. Subsidence and climate change together are expected to cause up to 26 per cent of China’s coastal lands to drop below sea level by year 2120, the study said.

Weight of urban development: Many Chinese cities are extensively urbanised. The sheer weight of the built environment is contributing to the sinking of cities, too. This might explain why heavily urbanised cities, such as Beijing, are gradually slipping below sea level.

A similar plight globally

It’s not just Chinese cities. Sinking cities are an increasingly common issue the world over. By 2040, approximately one-fifth of the world’s population is expected to reside in areas prone to sinking.

In the low-lying Netherlands in Europe, around 25 per cent of the land has already subsided and gone below sea level.

In the United States, 45 states are directly affected by subsidence. Around 44,000 square kilometres of land across these states are sinking. Over 80 per cent of these cases relate to groundwater extraction

The problem appears to be especially pronounced in Asia. The Indonesian capital, Jakarta, is now the world’s fastest sinking city. In 2022, a Singapore study cited by Nature revealed that out of the 44 major coastal cities suffering from subsidence and sinking, 30 were in Asia.

The way forward

The death knell is not yet to be sounded on the sinking cities of the world. There are ways to reign in the damage. Not just ways, there are examples of this, too.

Tokyo is a success story of sorts in this regard. The Japanese city, in the 1960s, was sinking at the rate of 240 mm per year. Then, the government enacted laws that restricted groundwater pumping. By the 2000s, the sinking had dropped to 10 mm annually.

China itself has an example to follow. Shanghai, one of the largest cities in the country, sank 2.6 metres between 1921 and 1965. Following a series of environmental regulations being enacted, this sinking was reduced to a rate of 5 mm per year.

There is still hope then.