Late last week, president Joko Widodo of Indonesia told the AP that he’s fast-tracking a decade-in-the-making plan for a giant seawall around Jakarta, a city that’s sinking as much as 8 inches a year in places—and as seas rise, no less. Models predict that by 2050, a third of the city could be submerged. It’s an urban existential crisis the likes of which the modern world has never seen.1

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To save itself, the city will first and foremost have to figure out how to find more sources of water to stop subsidence. But it will also have to spend a massive amount of money on the giant seawall—around $42 billion, it reckons. That’s the choice coastal cities are increasingly facing, to spend money to adapt now or suffer worse down the road. It’ll almost certainly be worth it in the long run: For every dollar spent on adaptation, you save between $4 and $10 in disaster recovery efforts.

“This is an expensive undertaking, but in some ways it's not any different from something like a high-speed rail discussion,” says Lester. “We need to make some changes in our built environment that are hugely expensive.”

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  • 1. [d]eploying a seawall is a massive political and engineering problem in anycountry, to say nothing of Indonesia’s struggles with a literal underlying crisis: Jakarta’s people are pumping too much groundwater, and consequently the land is collapsing underneath them. If Jakarta can’t find a way to hydrate its people some other way, it’ll keep sinking, pulling that new seawall down with it. It’s a glimpse of a dark future for much of human civilization, which stubbornly clings to coasts around the world.