The Downside of Density: Shanghai is Sinking

China Daily reports that Shanghai, China is sinking due to too much high rise construction. From the story:

A diminishing water table, combined with a growing number of skyscrapers, is causing large areas of China to sink, increasing flood risk and endangering the rail network, according to a survey released recently by the China Geological Survey.
The government has already launched a number of measures to combat the problem and a plan of action was approved by the State Council in February.
Research shows the most vulnerable spots are in the North China Plain, the Yangtze River Delta and the Fenwei Basin, covering a combined total area of 79,000 square kilometers - more than 100 times the size of Singapore.
More than 50 cities in these areas are now at least 20 centimeters lower than they were in the 1970s, the survey said.

The sinking cities may threaten transportation links:

The situation may become worse with the construction of high-speed rail, Wu Aimin, director of the geological survey and technology department at the China Geological Environment Monitoring Institute, told the Economic Herald.
As China enters a boom period for high-speed rail construction, authorities should monitor subsidence near railways, such as the high-speed rail linking Beijing and Shanghai.
"If the ground sinks, even by a few millimeters, it will threaten the safety of high-speed rail," Wu was quoted as saying.

As if the Chinese high speed rail program didn't have enough problems. All of the skyscrapers come with a cost:

There are about 65 buildings higher than 200 meters in Shanghai, while Tokyo has 45, according to Emporis, one of the world's leading providers of building statistics.
A study released by the China Geological Survey in 2008 showed that total economic losses due to land subsidence reached nearly 333 billion yuan ($53 billion) from 1956 to 2008 in the North China Plain.

This is an unexpected downside of density.