5 CITIES THAT ARE VULNERABLE TO RISING SEAS
Recent climate projections have put some new cities in the crosshairs
the thwaites glacier is about the size of a u.s. swing state and holds enough ice to raise sea levels by about 10 feet. This alone is scary enough to justify its nickname, the Doomsday Glacier, but there’s more. The Thwaites sits along a 75-mile stretch of shoreline in Antarctica that serves to partially shield the vast West Antarctic Ice Sheet from the warm ocean waters. The WAIS has enough ice to raise the seas by 200 feet.
Forty years ago, the Thwaites was thought to be shedding 40 billion tons of water each year. Scientists recently upped that figure to 250 billion tons. To their alarm, a river of warm water appears to be flowing beneath the glacier, which can only hasten the day when it collapses into the sea—it could be a century from now, or a few decades. No one really knows.
We haven’t even talked about Greenland yet. Another underground river of warm water was recently discovered under the Nioghalvfjerdsfjorden Glacier, which is expected to add between a foot-and-a-half and 5 feet to ocean levels in the next 200 years.
These projections carry some uncertainty, but one thing seems pretty clear: the next century will be tough for coastal city dwellers. Sea levels are rising about 3 millimeters each year. By the end of the century, the oceans could rise at least 2 feet over 2005 levels, according to a 2018 study in the Proceedings of the National Academies of Science. Michael Mann, a climate scientist, told NBC News that unless emissions of greenhouse gases are abated, by the end of the century more than 650 million people will be living on land that is under water all or much of the time.
Cities will take the brunt of the impact. The last big survey by the World Bank of cities around the world that are vulnerable to climate change was published in 2013, based on satellite data captured in 2005. It found that hundreds of coastal cities around the world will be at heightened risk of flooding in the next few decades. In the years since the study was published, risk calculations have changed for the worse, says Stephane Hallegatte, lead economist at the World Bank’s global facility for disaster reduction and recovery and an author of the report.
One change is that cities in Africa have grown quicker than expected. That means that any list of vulnerable cities would now have to include new names, like Lagos in Nigeria and Dar es Salaam in Tanzania. A dangerous combination of rising seas and poverty make these cities increasingly vulnerable. Many of the cities on the original 2013 list have improved their prospects greatly by taking steps to protect themselves against flooding. These include Guangzhou and Shanghai in China, Manila in the Philippines, Can Tho in Vietnam and New Orleans in the U.S.
Some cities in the developed world haven’t adequately addressed the rising threat. In particular, Miami and New York are vulnerable to storm surges that bedevil the east coast of the U.S., and neither has implemented adequate protections. They would do well to take a page from London, Amsterdam and Rotterdam, which have invested in dykes, barriers and drainage systems.
The worsening outlook on sea-level rise is prompting a change in how people think about flooding and plan for it. “People realize that it’s just not possible to prevent all floods, so you have to learn to live with the water and accept that it will sometimes have an impact,” says Hallegatte. “We cannot live behind taller and taller walls, because at one point, the consequences of one of those walls failing becomes too big.”
The Netherlands is at the forefront of new living-with-water techniques. They are building spaces in their cities for flood water to collect—areas of low density that are relatively easy to evacuate—to protect areas of high population density. They are using the dynamics of the river deltas to distribute sand in such a way that maintains protective dunes. Such quasi-natural systems are both less expensive to build and fail more gracefully than a big wall. “It’s what we call nature-based solutions,” he says. “Instead of trying to use concrete to just protect everything, you try to use natural mechanisms.”
“We see people from all continents, all income levels, asking the same question: how to manage increased flooding over the next 10 or 20 years,” says Hallegatte. Here are five cities that have grown relatively more vulnerable in the last few years.