China's cities are sinking, putting tens of millions at risk

Nearly half of the major cities in China are sinking, a new study finds. Subsidence exacerbates flooding related to sea level rise from climate change. Parts of Shanghai have subsided up to 9 feet in the last century. (Johannes Eisele/AFP via Getty Images)

Major cities across China are sinking, putting a substantial portion of the country's rapidly urbanizing population in harm's way in the coming decades, according to a sweeping new analysis by Chinese scientists.

Subsidence is the technical term for when land sinks relative to its surroundings, and it's a major threat for cities around the world. It accelerates local sea level rise from climate change, because the land is getting lower as the ocean gets higher. Urban subsidence can also affect inland cities by damaging buildings and roads, and causing drainage issues when water is trapped in sinking areas.