The Fragile Gulf

By Jeffrey Kluger with Cathy Booth Thomas/ Baton Rouge

If you want to get a true sense of how thoroughly Hurricane Katrina punished the Gulf Coast last week, a flyover by helicopter or Air Force One won't do it. The real picture doesn't resolve itself until you go 450 miles up, where a flock of Earth-observing satellites have been training their cameras on the Gulf of Mexico and beaming what they see back home. Researchers at Louisiana State University in Baton Rouge began studying the first portfolio of pictures taken since the hurricane hit last week, and what they saw was a shock. Entire barrier islands are missing. Coastal marshes have been shredded. A Native American encampment to the south of Port Sulphur seems to have vanished. Everywhere, dark watery splotches appear in the spots where the overloaded levees failed and burst.

"The city," says oceanographer Nan Walker, staring dourly at an image of New Orleans, "has turned to water."

New Orleans, of course, has always been more or less waterlogged. It sits in a bowl that averages 9 ft. below sea level, with Lake Pontchartrain brimming to its north, the Mississippi River running to its south and the Gulf of Mexico crashing at its door. Keeping a place like that dry would be a city planner's nightmare in the best of circumstances. But New Orleans' circumstances have never been ideal; the city was built in the center of one of the most hurricane-prone spots in the world. "New Orleans naturally wants to be a lake," says Timothy Kusky, professor of earth and atmospheric sciences at St. Louis University. Apparently, the city got its wish last week.

Which raises the inevitable question: If New Orleans is such a dangerous place, what in the world are we doing there--or, for that matter, anywhere else on the perilous Gulf Coast from Florida to Texas? Soggy soil, eroding shorelines and sudden storms make the whole region an unstable mess even without human intervention. And the more we build there, the worse we seem to make things, clawing away the natural river routes and marshlands that replenish the land and sucking out the oil and other subterranean resources that hold up the surface. Now, many experts warn, with greenhouse gases raising global temperatures, we are spawning more and deadlier hurricanes, ones that could kill a city in a single blow--if Katrina hasn't already done that to New Orleans, Gulfport and Biloxi.

But if the cities on the Gulf Coast have always been potential deathtraps, they have always been gold mines too--great natural ports on a warm-water gulf, perfectly situated to profit from the traffic moving up and down one of the world's most important shipping lanes: the Mississippi River. The port of South Louisiana moves more tonnage each year than any other in the nation. Add to that the commodities the Gulf produces, including nearly 30% of the nation's oil, 20% of its natural gas and a third of its fish and shellfish, and it is clear--as many have pointed out since last week--that even if New Orleans were completely leveled, we would have to build something in its place.

What complicates the story of the destruction--and makes the loss of life so tragic--is our role in the disaster. If it's true that human activity had a lot to do with making the region vulnerable to a hit by a hurricane like Katrina, it's also true that we knew all along the kind of environmental damage we have been doing to the Gulf. Now that we're paying the price for our recklessness, what are we going to do about it?

It was always evident that the Gulf of Mexico was a sweet spot for cyclones, but it took modern meteorology to explain just why. You need a lot of things to get a hurricane going, most important among them an existing storm with a bit of spin to it wedged between warm ocean water and a colder band of air above it. Locate all that at least 300 miles north or south of the equator--where the rotation of the Earth's slightly narrower circumference exacerbates the spin of the storm--and you have everything you need to sustain a hurricane. The Gulf has all those ingredients, and its cities and towns repeatedly suffer for it.

To survive such storms, early residents quickly learned that they would have to build carefully, particularly in low-lying New Orleans. Eighteenth century settlers established the famed French Quarter on some of the highest ground they could find, one of the reasons it remained relatively dry last week. As the Gulf, the lake and the river periodically overflowed, the growing city retreated behind an ever expanding web of soil, concrete and metal levees. Today there are 350 miles of those barricades snaking through the city and 22 massive pumping stations that are supposed to kick into action whenever the water sloshes over the walls. Having constructed that elaborate system, New Orleans was not inclined to abandon it. "The city built the levees to protect itself," says Craig Colten, L.S.U. geographer and author of the book An Unnatural Metropolis. "Now there's a huge investment in drainage."

Geology has only made things worse. Gulf land is squishy stuff, made mostly of silt deposited by eons of free-flowing rivers and periodic floods. When the high water recedes, the sedimentary layer remains, growing heavier and heavier and ultimately subsiding under its own weight. The only way to keep the land from sinking altogether is to let the soil replenish itself with each flood. Human beings have done just the opposite, walling off New Orleans and re-engineering the Mississippi River to flow around the growing metropolis, effectively choking off the silt supply.

In addition to allowing the unreplenished coastal marshlands to sink, that tampering eventually kills the wetlands that do survive, as salt water intrudes deeper and deeper inland, killing vegetation that helps hold the soil together. The elimination of natural flooding also causes barrier islands, which line the Gulf and protect the coast, to shrink. The Mississippi in its naturally flowing state spilled silt into an intricate delta, spreading sediment east and west and fortifying the islands. Walled and dredged all the way to the Gulf, the river now dumps that silt right over the edge of the continental shelf. Geologists report that the Chandeleur Islands--a healthy necklace of sandy barriers about 70 miles from New Orleans--appeared to have been wiped out by Katrina, leaving one more stretch of the city's coast dangerously exposed.

The Gulf's busy oil-and-gas industry doesn't help matters. Extracting those resources below the Gulf floor is like sticking a straw into the ground and sucking out all the liquid: ultimately you pull up the very material that's holding up the surrounding terrain. One study found that the greatest loss of Gulf wetlands coincided with the greatest extraction of oil and gas in the 1970s and '80s. Houston is thought to be sinking for much the same reason.

In Louisiana, the shrinkage is most dramatic. The state has lost 1 million acres of coast--11/2 times the area of Rhode Island--since 1930, nearly half of that vanished land lying between New Orleans and the Gulf. The city proper is estimated to be sinking 3 ft. per century. And while the whole world is struggling with rising sea levels, New Orleans and its environs hurt more than most. The State of Louisiana is estimated to be losing land at the alarming rate of about two acres every hour.

The forces that have caused the coast to subside are pretty well understood. What's far less clear is the possible role of global warming. That rising temperatures heat the ocean and melt ice caps is undisputed. Most climate models also predict that turning up the worldwide thermometer will lead to more extreme weather patterns--hotter hots, colder colds, harder rains. Hurricanes would seem to be especially sensitive to climate changes, since warm ocean waters are the fuel that drives the storms.

But while that is an easy argument to make, it's a hard one to prove. There were a record 33 hurricanes in the Atlantic between 1995 and 1999, and that doesn't take into account blockbusters like Katrina or 1992's Andrew. But the period from 1991 to 1994 was one of the quietest in history. And while the Pacific has seen an increase in hurricanes and typhoons in recent years, the southwestern Indian Ocean has remained stable and the northern Indian Ocean has actually seen a drop. Around the world, all that amounts to a statistical wash. "It's an unresolved issue," says atmospheric scientist Kerry Emanuel of the Massachusetts Institute of Technology, "but we do not see any increase at all in the frequency of hurricanes globally."

Emanuel and others believe that even if greenhouse heating does not spawn more hurricanes, it may make the ones that do occur more powerful. In an extensive study published this summer in the journal Nature, Emanuel surveyed roughly 4,500 storms brewed in the North Atlantic and western north Pacific since the middle of the 20th century. He found that the average power of the storms increased 50% in those 50 years. It's a change that, he has little doubt, is linked to global warming. A slightly weaker Katrina may have made all the difference to New Orleans, where the levees were made for withstanding a Category 3 storm but not the more powerful Category 4 (like Katrina when it made landfall) or Category 5 (like Katrina the day before).

As the city staggers back to its feet, fixing those broken levees will be a first priority. But such gap plugging is just triage in a woefully outdated system of ramparts that need extensive rebuilding and modernizing. The failed 17th Street levee had been strengthened not long before Katrina hit--an upgrade that obviously did not do the job. Now merely pumping the city free of the water the levees let in may take as long as nine weeks.

Just as important as fixing the artificial barriers will be replacing the natural ones: the protective wetlands that have been stripped away from the city's perimeter. In 2000, federal and state officials initiated proposals to spend $14 billion over the next 30 years for wetlands restoration along the Gulf Coast. But Congress balked at the initial outlay of $1.9 billion, and only $540 million has so far been allocated. As for measures to combat global warming, the Bush Administration has consistently resisted any legislation or global treaty that would hurt the energy industry or require sacrifices from American motorists. In the face of the lives lost last week and the billions of dollars it will cost to rebuild the devastated cities and ports, those policies seem tragically shortsighted. --With reporting by Daren Fonda/ New York and David Thigpen/ Chicago

With reporting by Daren Fonda/ New York, David Thigpen/ Chicago