Shanghai, China’s most populous city and an aspiring global financial center, is also among the world’s most vulnerable urban areas to a rise in sea levels as global warming melts polar ice.

Its location on a low-lying alluvial plain near the mouth of Asia’s longest river, the Yangtze, had already left it prone, but researchers warn that forests of skyscrapers sprouting across the ambitious metropolis could compound the threat by causing its marshy ground to sink.

“Shanghai came from the ocean, and has been facing the threat of rising sea levels,” said Wang Pingxian, a member of the prestigious China Academy of Sciences and professor of ocean geology at Tongji University in Shanghai.

“The rising sea level is a worldwide problem, caused by global warming, but Shanghai and Tianjin, among China’s coastal cities, face the biggest challenge, mainly because of land subsidence,” Wang said as part of the Reuters Global Environment Summit.

Sinking ground levels have long been a headache for Shanghai, although the culprit has traditionally been the pumping of ground water to support its rapid growth and industrialization.

The dyke along Shanghai’s riverfront Bund, which protects a mile of historic granite buildings from the waters of the Huangpu River, has been raised three times — by nearly 2 meters (about 7 feet) — over the past four decades.

Shanghai drilled its first deep well on the Bund in 1860, and as industrial development and ground water use accelerated, the city sank 1.76 meters between 1921 and 1965, or an average of about 4 centimeters a year.

As early as the 1960s, the Shanghai government began addressing the problem by pumping some of its treated water supply, which is now taken largely from the Huangpu River rather than from ground water, back below the surface.

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