Shanghai and Shenzhen are at risk of sinking due to land subsidence and rising sea levels.

Scientists warn that rapid sea level rise combined with land subsidence is posing a dual threat to China's key coastal cities.

Shanghai streets flooded after heavy rain on July 21, 2023 - Photo: AFP

According to the South China Morning Post on October 17, a new study published in Nature magazine warned that China is facing a "double threat": the phenomenon of land subsidence and the fastest sea level rise in the past 4,000 years, which could cause serious flooding in economic centers such as Shanghai, Shenzhen and Hong Kong.

The research team, including scientists from the UK, the US and China, said China's major cities are concentrated in coastal deltas, which are favorable for economic development but are very vulnerable to climate change.

These areas are formed from thick, soft sediments, causing the ground to naturally tend to sink.

“It is highly likely that the average rate of global sea-level rise since 1900 has exceeded any century-long period in at least the past 4,000 years,” the team said. According to the data, the average rate of sea-level rise is currently about 1.5mm/year.

Scientists say 94% of the current rapid urban subsidence phenomenon is caused by humans, mainly due to excessive groundwater exploitation, causing the land to sink faster than normal.

Shanghai discovered subsidence as early as 1921. By the 1960s, when groundwater extraction reached 200 million tons/year, the ground level was lowering by up to 10.5cm per year.

Meanwhile, climate change causes the ocean to absorb heat and expand, combined with melting ice in Greenland and Antarctica, causing global sea levels to rise.

According to Mr. Lin Yucheng - a researcher at Rutgers University (USA), some areas of Shanghai have sunk more than 1 meter in the past century due to excessive groundwater exploitation, many times faster than the current rate of sea level rise.

He warned that even a rise in sea levels of just a few centimeters would increase the risk of flooding in delta regions, home to many industrial zones and global manufacturing centers.

"If a natural disaster happens here, the international supply chain will be seriously affected," he said.

Although Shanghai has slowed its subsidence rate thanks to strict management of groundwater exploitation, other cities such as Jakarta, Manila and New York also face similar risks because of their low-lying coastal locations.

Another study published in June also found that severe subsidence in Shanghai has spread to industrial and coastal areas over the past 30 years, but the rate of subsidence has slowed thanks to groundwater pumping. China is estimated to lose about $1.5 billion a year due to subsidence, with Shanghai alone losing more than $3 billion between 2001 and 2020.

HA DAO

Source: https://tuoitre.vn/thuong-hai-tham-quyen-doi-mat-nguy-co-chim-vi-dat-lun-va-nuoc-bien-dang-20251018105338648.htm