Rising seas threaten China’s long, low, and crowded coast

By Li You

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In the 70-plus years since [the big storm of 1949], the Chinese government has tremendously improved the country’s defenses against the seas. Nowhere more so than in Shanghai, which is now surrounded by hundreds of kilometers of storm walls. But as climate change is pushing the world’s oceans ever higher, China’s current defenses will be rendered inadequate. Protecting China’s low-lying coast, home to much of the country’s population and wealth, is inevitably going to become harder and more expensive.

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Sea-level rise is only half the story, according to Gao Shu, director of the State Key Laboratory of Estuarine and Coastal Research at Shanghai’s East China Normal University. China’s coast is also at greater risk of flooding due to increasingly strong storms. From 2005 to 2015, more than 200 storm surges hit China, according to 2016 research noting that the storms’ frequency and intensity have been increasing as a result of climate change.

The potential damage from floods has also escalated. Beijing-Tianjin-Hebei, the Yangtze River Delta, and the Pearl River Delta, the country’s three major economic hubs, have a combined population of about 126 million people living on low-lying, vulnerable land. Cities from those regions, namely Guangzhou, Shenzhen, Tianjin and Shanghai, are among the top major cities projected to suffer the most — or facing the highest increases in — economic losses from flooding in 2050, according to a 2013 report co-authored by researchers at the World Bank that analyzed 136 seaport cities with populations of over 1 million and that accounted for flood defences.

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But upgrading sea walls is a costly proposition. Shanghai has invested 50 million yuan ($7.7 million) for every kilometer of its 510-kilometer sea walls. “The higher the sea wall is, the more difficult it is to maintain it,” says Gao. “The cost growth is exponential. The price for constructing a 2-meter-high sea wall, compared with that of a 1-meter-high one, is not double, but tenfold.”