1 october 2017

How many big storms before people abandon coastal cities?

For homeowners in flood zones, one big question looms: Rebuild or retreat after another “500-year storm?”

Reynard Lok, Salon, October 1, 2017

People love living near the coast. Only two of the world's top 10 biggest cities — Mexico City and Sáo Paulo — are not coastal. The rest — Tokyo, Mumbai, New York, Shanghai, Lagos, Los Angeles, Calcutta and Buenos Aires — are. Around half of the world's 7.5 billion people live within 60 miles of a coastline, with about 10 percent of the population living in coastal areas that are less than 10 meters (32 feet) above sea level.

Coastal migration has been steadily trending upward. In the U.S. alone, coastal county populations increased by 39 percent between 1970 to 2010. As the population skyrockets — from 7.5 billion today to 9.8 billion by 2050, and 11.2 billion by 2100, according to a recent United Nations report — the question for sustainability and development experts is, will the world's coasts bear the burden of all this humanity? But with the rise of both sea levels and extreme weather, perhaps a better question is, will all this humanity bear the burden of living along the world's coasts?

Growing appeal: Landlocked life

As the "500-year" hurricanes Harvey and Irma (and 2011's Irene) powerfully and tragically demonstrated, living near a coastline is an increasingly dangerous proposition. But for some coastal regions, rising seas and hurricanes aren't the only cause for alarm: the coastal lands in Virginia, North Carolina and South Carolina are sinking by up to 3mm a year, according to a new study led by researchers at the University of Florida. Could these multiple factors reverse humans' seaward migration?

Some research suggests that may be the case. A recent University of Georgia study found that rising sea levels could drive U.S. coastal residents far inland, even to landlocked states like Arizona and Wyoming, which could see significant population surges from coastal migration by 2100. Many of these places are not equipped to deal with sudden population increases. That means sea level rise isn't just a problem for coastal regions.

"We typically think about sea-level rise as being a coastal challenge or a coastal issue," said Mathew Hauer, author of the study and head of the Applied Demography program at the University of Georgia. "But if people have to move, they go somewhere."

"We're going to have more people on less land and sooner than we think," said Charles Geisler, professor emeritus of development sociology at Cornell University. “The future rise in global mean sea level probably won't be gradual. Yet few policy makers are taking stock of the significant barriers to entry that coastal climate refugees, like other refugees, will encounter when they migrate to higher ground."

Geisler is the lead author of a study published in the July issue of the journal Land Use Policy examining responses to climate change by land use planners in Florida and China. He and the study's co-author, Ben Currens, an earth and environmental scientist from the University of Kentucky, make the case for "proactive adaptation strategies extending landward from on global coastlines." By 2060, about 1.4 billion people could be climate change refugees, according to Geisler's study. That number could reach 2 billion by 2100.


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