More than 2500 square kilometres of reclaimed land has been added to coastal cities in the 21st century, increasing the areas threatened by sea level rise.
People have been building new land for centuries, from the Netherlands to the San Francisco Bay Area. But the pace has picked up in the new millennium.
Hundreds of coastal cities have added land since the year 2000, from sea walls in Shanghai, China, that have captured river sediment to build new neighbourhoods, to artificial islands like the Palm Jumeirah in Dubai, United Arab Emirates, built using barges spraying dredged-up sand.
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at the University of Southampton in the UK and his colleagues analysed satellite images of 135 of the most populous coastal cities to estimate how much land has been reclaimed this century.
They counted the change in area covered by surface water in images captured between 2000 and 2020, excluding changes to tidal wetlands and marshes. Sengupta says the method also captured natural changes, but the pace and shape of the new land showed that most of it was added by people. 鈥淲e humans are building some very interesting shapes,鈥� he says.
Nearly all the new construction was in east Asia, South-East Asia and the Middle East. Around 10 square kilometres was added both in West Africa and western Europe. Seventy per cent of this additional land would be vulnerable to flooding related to sea level rise by the end of the century under a moderate emissions scenario, the researchers found. Sengupta says some of the new land is also at risk of sinking.
at the University of Plymouth in the UK says she is very concerned about sea level rise and storm surge in these areas. 鈥淲e should be investing in future-proofing existing low-lying urban areas rather than reclaiming land and creating more problems down the track,鈥� she says.
at the Global Climate Forum, a research organisation in Germany, says reclaimed land, if raised high enough or if built with defensive infrastructure, can serve to protect other areas of cities from sea level rise. However, he says the threat of flooding such valuable real estate poses risks to the financial stability of governments that have backed the projects. 鈥淭hat鈥檚 the tension that exists for coastal development everywhere,鈥� he says.
While much of the added land has expanded ports and residential and industrial areas, Sengupta argues that many locations are expanding to attract investment and to boost 鈥減restige鈥� rather than to address growing populations.
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