Dear MEL Topic Readers,
270 million people are living on sinking land in China’s major cities,
new study finds
Land subsidence is the gradual sinking or settling of the Earth's
surface due to natural processes and human activities. The primary causes of human-caused
land subsidence include groundwater extraction, mining activities, and urban
development. If more groundwater is extracted than it is replenished, the water
table is lowered and the overlying land sinks. Also, the land sinks due to the growing weight
of cities themselves, such as roads, bridges, and buildings. A new study found
that nearly half of China’s urban areas are sinking faster than 3 millimeters a
year, and over 20% of the areas are subsiding faster than 10 millimeters per
year. When land subsidence is coupled with sea level rise in coastal cities
like Shanghai, the area could face more severe and frequent flooding. One effective
but expensive patchwork is to build physical protection like a dyke. In fact,
Shanghai’s dyke system stretches along the coast of the East China Sea,
spanning approximately 120 kilometers from the mouth of the Yangtze River in
the north to Hangzhou Bay in the south. Can other coastal cities in the world afford
to build and maintain such costly dyke systems to prevent flooding?
Read the article and learn about land sinking in major cities in China.
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