Population Plus Climate: Why Coastal Cities Will Face Increased Risks From Floods

Living in New York, it’s easy to forget that the ocean is right on our doorsteps. This isn’t Miami with its beaches or Venice with its canals or New Orleans with its history of storms and floods. New York has always been a supremely self-involved city—this famous magazine cover pretty much sums it up—and though Manhattan is an island, it’s one that has its eyes turned inward, not out toward the water that rings it.

Hurricane Sandy ended that illusion last year. The storm surge flooded tunnels, subway lines and apartment buildings; swamped power lines and transformers caused a blackout over much of Manhattan that lasted for days. Altogether Sandy cost the city of New York some $19 billion in public and private losses, nearly all of it due to the water. Sandy wasn’t even that powerful a storm, its winds barely ranking as a category 1 when it made landfall along the East Coast last October. What it had was something any New Yorker who’s hunted for apartments could appreciate—location, location, location—hitting the biggest city in America and flooding it with all that forgotten coastal water.

For coastal cities like New York, Hurricane Sandy was a coming attraction for what is likely to be a very wet and destructive future. According to leaked drafts of the forthcoming new report from the Intergovernmental Panel on Climate Change (IPCC), scientists believe that sea level could rise by more than three feet by the end of the century is carbon emissions keep growing at a runaway pace. And a new study published in the journal Nature Climate Change laid out the enormous flood losses that major coastal cities could face in the future. Average global flood losses could rise from approximately $6 billion per year in 2005 to $60 to $63 billion per year by 2050, thanks to population and economic growth along the coasts and the multiplying effect of climate change-driven sea level rise. As Robert Nicholls, a professor of coastal engineering at the University of Southampton in Britain and a co-author of the study, put it in a statement: “There is a pressing need to start planning how to manage flood risk now.”

The Nature Climate Change study looked at both present and projected future flood losses in the 136 largest coastal cities in the world, looking at their financial risks both in absolute terms—taking into account protections like sea walls and dikes—and as a percentage of the city’s GDP. The cities ranked as most at risk today range from Guangzhou in southern China to Mumbai in India to, yes, New York City. What those cities tend to have in common is high wealth and population levels and relatively little flooding protection. (By contrast, Dutch cities like Amsterdam or Rotterdam—which are extremely flood-prone geographically—aren’t found on the list because the Netherlands government has invested heavily in coastal protection.) Three American cities—Miami, New York and New Orleans—are responsible for 31% of the total losses across the 136 cities surveyed in 2005. When it comes to losses as a percentage of total city GDP—which gives the very richest cities like New York an advantage—Guangzhou, New Orleans and Guayaquil in Ecuador are most at risk.

The situation changes a bit in 2050. The study assumed that climate change will lead sea levels to rise 0.65 to 1.3 ft. by 2050, with some cities facing additional sea level rise because of local subsidence—literally, the earth sinking. Developing cities like Guangzhou, Mumbai and Shenzhen face the biggest risks, though Miami and New York rank highest among cities in developed nations. If no improvements are made in flood defenses, the study estimates that the world could be facing as much as $1 trillion or more per year in losses. Now, that number is the worst of the worst case, assuming that cities do absolutely nothing to protect themselves from sea level rise, suffer major floods and then pay to immediately rebuild everything they lost. But even assuming improvements in coastal defenses, potential losses will increase significantly, thanks to the risk of bigger floods and more immediately, a huge increase in the number of people and the value of property along the coasts.

That second bit is important. It’s vital for governments to gain a better understanding of flooding risks from global warming—and sea level rises of the sort apparently projected by the IPCC will endanger major world cities. But the most immediate threat is the sheer increase in people—and their property—put in harm’s way in coastal cities. In the U.S. 87 million people now live along the coast, up from 47 million people in 1960, and globally six of the world’s 10 largest cities are on the coast. Of the $60 to $63 billion in flood risk the Nature Climate Change study estimates the world’s cities will face by 2050, $52 billion is due to economic and population growth—the rest is due to sea level rise and land use change.

That doesn’t mean that climate change-amplified floods and storms don’t present a danger to coastal cities—or that we don’t need to worry about reducing carbon emissions. But the numbers don’t lie—the single biggest increase in the risk from flooding comes from putting people and property in places where floods have always been likely to happen. As Sandy showed, coastal cities are at risk from major flooding right now if a storm should hit at the wrong place at the wrong time. It’s location, location, location—which is why it’s so important to spend money now to improve coastal defenses. We don’t have to wait for climate change to come.

Hello, My Name Is Dolphin: The Mammal That Never Forgets

In his Hitchhiker’s Guide to the Galaxy books, the late, great British satirist Douglas Adams wrote that dolphins are the second most intelligent creatures on earth — before humans and after mice, which spend their time running complex lab experiments on scientists. The mice might not quite live up to their No. 1 billing, but the more we learn about the cognitive abilities of dolphins, the more they indeed seem to have the No. 2 spot locked up. Not only do dolphins have impressive memories for tasks, the ability to use tools and elaborate social structures, but they also have their own names, distinctive identifying whistles that they develop themselves. Now a study in Proceedings of the Royal Society B reports that dolphins can recognize the whistles of others they shared a tank with as long as 20 years ago, the most enduring social memories ever observed outside of humans.

The study, undertaken by Jason Bruck, then a graduate student at the University of Chicago, used 43 dolphins ranging from 4 months to 47 years old that are cycled among various institutions as part of a captive breeding program. Some of them had lived together for only three months; others had shared a tank for more than 18 years before being separated. Bruck first obtained recordings of each dolphin’s name whistle. Then he set up an underwater speaker in the dolphins’ tanks that played whistles from strangers and from former tankmates. The difference in the dolphins’ reactions was unmistakable.

“When they hear a dolphin they know, they often quickly approach the speaker playing the recording,” Bruck said in a prepared statement. “At times they will hover around, whistle at it, try to get it to whistle back.” They paid far less attention to a stranger’s whistle-name.

Moreover, it didn’t matter how long the animals had been separated — a dolphin could recognize the call of a companion it had last seen decades ago just as easily as one it last saw six months ago. Nor did it matter how short or long the animals had been housed together; they responded with the same recognition to a long-term friend or a more fleeting acquaintance. In the most impressive case, a dolphin named Bailey recognized the whistle of Allie, her tankmate 20 years and six months ago. “This shows us an animal operating cognitively at a level that’s very consistent with human social memory,” Bruck said.

Wild dolphins have a life expectancy that ranges from 20 to 50 years (though such superannuated adults are rare), and they live in ever shifting pods, with individuals constantly splitting off and reuniting with the group. Bruck suggests that animals with such a social structure may benefit from a long memory for one another, perhaps supporting a connection between complex social behavior and the evolution of memory. But it may also be that a prodigious memory for names is just part of the larger, fascinating package of dolphin intelligence, included for no particular evolutionary reason — another element of the hidden depths of a mammalian cousin that we continue to explore.