Sinking Cities: Why Rising Seas Threaten Many of The World's Great Destinations

By Terrell Johnson Published: Sep 12, 2013, 5:35 PM EDT

Since the 1920s, China's biggest city has sunk more than 6 feet thanks to a combination of pumping groundwater for drinking and the construction of dozens of densely packed skyscrapers and high-rise buildings. 

 

Little by little, the ground underneath cities from Venice to Jakarta is sinking every day. In some places, it's occurring as slowly as a millimeter or two every year, while in others, it's dropping by as much as a few inches every year.

 

The reasons why vary by location, but scientists point to a familiar script: As people move from the countryside and into urban areas, they bring pressure to extract more and more natural resources from the ground, like water and oil.

 

Meanwhile, more and bigger buildings are built – sometimes spectacularly big, like China's new Shanghai Tower whose immense weight presses down on the Earth, sometimes even causing cracks on surrounding streets.

 

While these are happening, the ground is also naturally sinking in many places, especially in coastal cities built on river deltas. Called land subsidence, this phenomenon accelerates when humans build structures like levees and dams that prevent river floods from replenishing the ground with silt and sand from upstream, and instead wash it out to sea.

And there's a fourth culprit: rising global sea levels, driven by the warming and expanding of the oceans and the melting of glaciers, polar ice, and the Greenland and West Antarctica ice sheets.

 

http://www.weather.com/news/science/environment/worlds-fastest-sinking-cities-20130910