13 January 2021 | Reading 15 mins.

Coastal cities: The frontline against rising seas

Robert Muggah
SecDev Group and Igarape Institute

Robert Muggah, SecDev Group and Igarape Institute

The warning signs are getting harder to ignore. Rising seas are already displacing tens of thousands of people, destroying millions of homes, and generating billions of dollars in losses. Due to competing predictions of future global temperatures, scientists are unsure exactly how fast or high sea levels will rise. But they all agree on its impacts: submergence and flooding of coastal land, saltwater intrusion into surface waters and groundwater, increased erosion and overwhelmingly negative social and economic repercussions. They are also clear that these effects will be widespread and will accelerate with time.

Even in the unlikely event that global temperatures are kept from exceeding two degrees Celsius by 2050, close to 600 coastal cities with over 800 million residents will be ravaged by rising seas and storm surges, water salinization and an unfathomable financial burden. Yet most of the world’s fastest-growing sea-side cities are not even remotely prepared to deal with rising water levels. Most coastal cities across North America and Western Europe have yet to put in place mitigation and adaptation strategies. Few cities in Africa, Asia or Latin America have published climate action plans, much less installed concrete strategies to protect and educate their populations.

Sinking cities

Some cities are more at risk than others. Sprawling megacities like Lagos, Shanghai and Mumbai are facing sea level rises well above the global average. Since many of them are built on mangroves and swamps, some of the world’s biggest cities are sinking at the same time as seawater is seeping in. This is not just because they are heavy, but because their residents are extracting vast quantities of groundwater. Consider Jakarta, a sprawling metropolis of over 9.6 million people, which has sunk by 2.5 meters (over eight feet) over the past decade. As can be seen on the map, parts of the city have disappeared under up to 3 meters (ten feet) of sea-level rise since the 1980s. And if global temperatures rise by one and a half degrees Celsius or more, entire neighborhoods are likely to be swallowed up.

Jakarta area, land projected to be below annual flood level in 2050 (shown in red). Image: Climate Central.

Miami area, land projected to be below annual flood level in 2100 (shown in red). Image: Climate Central.

Jakarta is a victim of geography. It is hemmed in by the Java sea to the north, built on swampy land and is crisscrossed with over a dozen rivers, many of them intensely polluted. Despite an abundance of water, local authorities can only meet about 40 percent of the city´s demand. Local authorities´ inability to enforce regulations preventing groundwater extraction means that illegal tapping is out of control. The northern neighborhoods, home to one of Southeast Asia’s busiest seaports, are sinking fastest. Yet despite routine flooding, luxury apartments are filling-in the coastal skyline. The building bonanza will soon go bust: 95 percent of the city is expected to be underwater by 2050. Local authorities have taken notice and are building a $40 billion sea wall with Dutch and South Korean support. The city has already relocated more than 400,000 people from threatened riverbanks and reservoirs. But the truth is that the city is unable to face-up to the factors that are causing the city to sink beneath the waves.

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This feature first appeared as “The world’s coastal cities are going under. Here’s how some are fighting back” on 16 January 2020 at www.weforum.org.