China’s double crisis: Shanghai is sinking as sea levels reach their highest in 4,000 years

Global sea levels are rising faster than at any time in the past 4,000 years, while Shanghai is simultaneously sinking — a combination that could endanger China’s financial hub and the world’s supply chains, according to a new international study published in Nature.

China’s twofold threat

The study, conducted by researchers from the United Kingdom, China, and the United States, found that China faces a dual threat from rising seas and land subsidence. Many of the country’s major economic centres — including Shanghai, Shenzhen, and Hong Kong — lie in low-lying river deltas, areas ideal for development but highly vulnerable to flooding.

These cities are built on thick, soft sediment and are therefore prone to natural subsidence, which is further accelerated by human activities such as groundwater extraction.

Fastest sea level rise in millennia

The researchers concluded that the average global sea level rise since 1900 has been greater than in any previous century for at least 4,000 years, with an average increase of 1.5 millimetres per year. The main causes are thermal expansion from warming oceans and melting ice sheets and glaciers.

“Our analysis shows that around 94% of modern city subsidence is caused by human activity, with local subsidence rates often exceeding the global sea level rise,” the scientists said.

Shanghai sinking faster than the sea rises

Shanghai, located in the Yangtze River Delta, first recorded land subsidence in 1921. In the 1960s, groundwater extraction peaked at 200 million tonnes annually, causing the city to sink as much as 105 millimetres per year.

Lin Yucheng, a postdoctoral researcher at Rutgers University and co-author of the study, said some parts of Shanghai have sunk more than one metre in the past century due to excessive groundwater use — several times faster than the current global sea level rise.

“Even a few centimetres of sea level rise greatly increases flood risk in delta regions. These areas are not only critical domestically but are also major global manufacturing hubs. If coastal flooding increases, global supply chains will be at risk,” Lin said.

Climate and economic impact

China suffers average economic losses of US$1.5 billion per year from rising sea levels and land subsidence linked to climate change and groundwater depletion. Between 2001 and 2020, Shanghai alone incurred over US$3 billion in damages.

To counter the problem, the city has begun tightening controls on groundwater extraction. Similar risks are being faced by New York, Jakarta, and Manila, all situated on low-lying coastal plains.

“Deltas have always been attractive for agriculture, fisheries, and urban development,” Lin noted. “But their flat, soft terrain means that continued sea level rise and human-induced subsidence could cause them to sink much faster.”

Ongoing mitigation efforts

A separate study by researchers in Shanghai and the Netherlands found that in the past 30 years, severe subsidence has expanded from Shanghai’s central districts to its eastern and southern coastal industrial zones. However, groundwater management and recharge programmes have significantly reduced subsidence rates.

The researchers have also developed risk maps to help authorities identify vulnerable areas and prepare for future sea level increases.

Experts emphasise that even small increases in sea level can have major consequences, underscoring the urgent need for coastal engineering, water management, and urban planning to safeguard both China’s economy and global trade stability.