China’s insatiable cities

(Ecns.cn)--China's rapidly-expanding cities are damaging the environment and eating up precious farmland, says the National Natural Science Foundation of China and the National High-tech R&D Program.

Their latest report shows that from 1990 to 2000 the country's developed area grew from 12,200 square kilometers to 21,800 square kilometers. That figure reached 40,500 in 2010, an increase of 85.5 percent.

"China's urban sprawl is striking. It has hit a record high in terms of speed and scale," says Professor Gong Peng of the Center for Earth System Science, Tsinghua University.

Farmland in suburban areas is the first to be affected, adds Wang Lei, a researcher at the Institute of Remote Sensing Applications.

China has set a "red line" that supposedly guarantees that the country's amount of arable land will never fall below 1.8 billion mu (297 million hectares). Nevertheless, during the past two decades more and more such land has been absorbed, says Wang.

The report goes on to show that 53.4 percent of newly urbanized areas were built on farmland between 1990 and 2000. The proportion rose to 68.7 in 2010, an equivalent of 19 million mu.

"Such changes make cities more vulnerable to natural disasters," says Gong Peng.

Data show that China's cities have been sinking. Ningbo, in Zhejiang Province, sunk to 4.82 meters above mean sea level in 2010, 3.17 meters lower than it was in the 1990s. Tianjin also subsided from an elevation of 5.95 meters in 1990 to 3.26 meters in 2010.

"Coastal cities are easily affected by extreme weather as they extend rapidly into low-lying areas," adds Wang Lei.

South China's young city of Shenzhen is a particularly striking example of problem sprawl. The city has undergone unprecedented growth, transforming from a fishing village into a surging metropolis in only about two decades.

Data from the Shenzhen Statistics Bureau show that the city's urbanized area increased from 470.68 square kilometers in 2001 to 703.47 square kilometers in 2005, jumping by more than 58 square kilometers each year.

Such low-density spatial expansion has generated long commutes and traffic congestion: per capita consumption of petrol in Shenzhen more than doubled from 2001 to 2005, contributing to auto-related air pollution, according to the article "Urban sprawl: A case study of Shenzhen, China" by Qi Lei and Lu Bin.

Meanwhile, larger urban spaces haven't always boosted economic growth.

"Many new urban areas have been developed into industrial parks and high-tech development zones. But 60 percent of them are unsuccessful, and most are wasted," says Wu Bihu, director of the Center for Recreation and Tourism Research at Peking University.