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.

The Great, Belching Black Hole — Eats Gas, Burps X-rays

Was Einstein smarter than a sixth-grader? When it came to black holes, maybe not. For much of the 20^th century, astronomers and physicists were unsure about whether black holes — which were predicted by Einstein’s General Relativity Theory — even existed.  That was a fair enough doubt, since the idea of a superdense star remnant with a gravity field so powerful not even light could escape it did defy credibility. Even Einstein himself thought they were just a mathematical curiosity that couldn’t possibly exist in the real universe.

Today, every schoolchild knows better. Astronomers have found giant black holes lurking at the cores of galaxies, the Milky Way among them, and more modest black holes all over the place, including up to 60 in our home galaxy. Now, that cosmic census has expanded dramatically: using the orbiting Chandra X-Ray Observatory, astronomers have spotted 26 of the more modest variety of black hole in the Andromeda galaxy, which is not only the Milky Way’s closest neighbor, but also its near twin.

Along with nine black holes detected previously, that brings Andromeda’s total to 35. If that many are detectable, says Harvard astronomer Robin Barnard, lead author of a report on the new objects in The Astrophysical Journal, “we know there must be lots we can’t detect — maybe tens of thousands, maybe more.”

The reason: a star-size black hole like the ones Barnard and his colleagues found can be detected only if it’s gulping down gas, and that’s relatively rare. It only happens, in fact, when the black hole orbits an ordinary star and dines on its outer atmosphere. As it does, the gas heats up to millions of degrees as it tries to cram its way down the black hole’s voracious gravitational throat, and in so doing emits bursts of X-rays—sort of giant, electromagnetic burps.

In the handful of cases in which that’s happening, Chandra can easily spot a star’s digestive blast. “If you look at the central region of Andromeda in visible light,” says Barnard, “you see a huge mass of stars — billions upon billions of them.” If you look with Chandra, though you see just a few hundred bright dots — the ones emitting x-rays.

Some of those emissions are actually not produced in Andromeda, but rather, come from the giant, gas-sucking black holes at the cores of other galaxies which just happen to lie in the background, but much, much farther away. “These background galaxies are incredibly bright,” says Barnard, but they’re easy to identify because their X-ray light varies up and down relatively slowly as their gas supply waxes and wanes, a pattern different from that produced by the smaller black holes in Andromeda itself.

Other dots of X-ray brightness come from stars in Andromeda that orbit neutron stars, the dense remnants of dead stars that aren’t quite massive enough to collapse into black holes. These pull gas from companion stars as well, and while the gas merely collides with their surfaces, that impact heats it up enough to produce X-rays too. The difference, says Barnard, is that the mix of X-ray “colors,” or wavelengths, is quite different from those generated by black holes.

Once you weed out the X-rays from background galaxies and from neutron stars, says Barnard, what’s left is black holes, ranging from five to ten times the mass of the Sun. Getting a perfectly clear picture might, in theory, require the astronomers to weed out emissions from the giant black hole at Andromeda’s core too. Unlike those in the background galaxies Chandra sees, however, Andromeda’s black hole, says, Barnard, is “wimpy. It’s ten to a hundred times fainter than the small black holes we can see, even though it’s a million times more massive.” That’s because there doesn’t happen to be a lot of gas available for swallowing these days — which is the case for the Milky Way and most nearby galaxies as well, although that could change before too long, thanks to an interstellar gas cloud spotted in 2011 that’s hurtling toward our galactic center and could arrive in September or October. (Astronomers expect some x-ray fireworks, but little more.)

There’s actually one more class of black holes that physicists have speculated about: teeny tiny ones, smaller than an atom, which might have formed in the intense turbulence of the first moments of the Big Bang. These probably would long since have vanished, although there was some speculation that new ones mightemerge from the Large Hadron Collider atom-smasher in Europe.

That would have been a triumph for science — but since it could in theory have destroyed the Earth, it’s just as well that it didn’t happen.