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Tombstone over a flooded grave in Leeville, Louisiana.

A tombstone over a flooded grave in Leeville, Louisiana.

Photograph by Tyrone Turner, National Geographic

Tim Folger

for National Geographic

Published May 17, 2013

Part of our weekly "In Focus" series—stepping back, looking closer.

When Terry Serigny was growing up in Leeville, Louisiana, in the 1950s, the Mississippi River Delta town was also known as Orange City for its many citrus groves. Today none of those groves remain. Leeville itself is vanishing, sinking into the Gulf of Mexico.

Old black-and-white photos hanging on the walls of Serigny's bait shop show wetlands, small ridged islands with trees, and oil derricks where there is now only open water. "Everything that you see here has all been washed away," he says, pointing to the photos. "There is nothing left to stop the saltwater from coming in."

The Mississippi Delta is one of the fastest disappearing land masses on Earth. It has lost nearly 1,900 square miles since the 1930s, and is still losing a swath about the size of a football field every hour.

"This land loss crisis," says the Louisiana Coastal Protection and Restoration Authority (CPRA), "is nothing short of a national emergency." And yet, as a slowly unfolding catastrophe, it gets much less national attention than acute disasters like Hurricane Katrina in 2005 or the Deepwater Horizon oil spill in 2010.

 

People sit in a nearly empty bar in Leeville, Louisiana.
Idle locals sit in a Leeville bar two months after the Gulf oil spill.

Photograph by Dan Zak, Washington Post/Getty Images

 

This week, however, the CPRA announced a list of 39 long-term coastal restoration projects that it hopes to pay for, at least in part, with money the state receives from BP to compensate it for the 2010 oil spill.

The projects are all part of a 50-year, $50 billion master plan that the authority announced last year. That plan has an incredibly ambitious—some would say impossible—goal: to stop the land loss and even reverse it, in the face of a global rise in sea level, by the second half of this century.

Land loss threatens not only the people, culture, and economy of southern Louisiana, but also unique wetland ecosystems.

"Just as we're losing species off the tops of mountains with global warming, we're losing species off the tops of our natural levees, because the whole system is becoming wetter," says Julie Whitbeck, a National Park Service ecologist who works at the Barataria Preserve, a 23,000-acre mix of forest and wetlands a 30-minute drive south of New Orleans. The preserve is losing land, especially along its western edge where it borders Lake Salvador.

On Friday and Saturday, crowds of scientists, schoolchildren, and other wildlife lovers will be descending on the preserve, which is part of Jean Lafitte National Historic Park, for a BioBlitz: a 24-hour effort to count and map some of the park's many diverse species, from insects to alligators to bald cypress trees.

 

Small plants grow in a cypress swamp in Jean Lafitte National Park.
Salvinia plants grow in a cypress swamp in Jean Lafitte National Park.

Photograph by Gerald Herbert, AP

 

The BioBlitz is an annual event, sponsored at a different park each year by the Park Service and National Geographic. As much celebration as science, this year's event will have an added edge because it's taking place in a park and a region whose future is fundamentally uncertain.

Forces of Destruction

A disastrous confluence of forces is to blame for the gradual retreat of the Louisiana coast. Some forces, like floods from hurricanes or subsidence of muddy sediments, are natural. But the most serious problems are man-made.

One hundred years ago, the region's two big rivers—the Mississippi and the Atchafalaya—dumped some 500 million tons of land-replenishing sediments onto the Delta every year. Today about half the rivers' sediment load never reaches the Delta. Instead, it settles behind thousands of dams and levees or is channeled by those levees far out into the Gulf of Mexico.

Meanwhile, navigation canals built to facilitate oil exploration and shipping allow saltwater to intrude far inland, killing freshwater plants and trees. When the plants die, the soil crumbles, and land falls into the sea.

All of these challenges might be manageable were it not for another threat, one that will only worsen year after year: the rise of sea level caused by global warming. That rise is happening because seawater expands as it warms, and because glaciers and ice sheets are melting.

 

Debris and a dead tree on Isle de Jean Charles, Louisiana.
Despite the urges of public officials, some still live on sinking Isle de Jean Charles.

Photograph by Bill Haber, AP

 

"For most of the last 7,000 years, sea level was rising at about one millimeter per year—that's our best guess from the data," says Harry Roberts, an oceanographer at Louisiana State University. "But since the 1990s satellite data suggest that the average global sea-level rise is now around three millimeters per year."

Global sea-level rise is modulated from place to place by local effects—and the dominant local effect in Louisiana is geologic subsidence that is no longer being compensated by new sediment. "We've tripled the rate of sea-level rise and decreased the amount of sediment," says Roberts. "We've got a major league problem here in Louisiana."

Along the Louisiana coast, sinking land and rising sea combine to create a rate of relative sea-level rise that is far higher than the global average. Measurements by NOAA, the National Oceanic and Atmospheric Administration, show increases of almost .4 inch (10 millimeters) annually. That's about three feet a century.

Turning the Tide?

Can the state stem the loss of its land? The master plan released last year by the CPRA sets a goal of gradually reversing land loss and achieving a net gain in land by 2061, something that last occurred in the 1930s.

To reach that goal the state will try to restore sediment to the delta using two different strategies. One would punch holes in the levees to divert muddy water from the Mississippi and Atchafalaya rivers into marshes, allowing the rivers to lay down sediments there much as they once did during their seasonal floods.

The second strategy would rebuild marshes with sediment dredged from riverbeds and the Gulf of Mexico, and then pumped through a statewide network of pipes into areas of open water that are still shallow enough to be reclaimed.

 

Cattails grow in newly dredged mud.
Cattails grow in newly dredged mud.

Photograph by Tyrone Turner, National Geographic

 

Both approaches have already been used to some extent, with mixed success. A recent NOAA report found no evidence that earlier river diversions had slowed the rate of wetland loss in the state—but the CPRA points out that those diversions were not designed to capture water that was laden with sediment.

Local fishermen have long complained that the sudden huge influx of freshwater into brackish marshes drives out valuable salinity-loving species such as speckled trout and oysters. The CPRA counters that the marshes in question weren't always brackish; they got that way because of the very encroachment by the sea that the CPRA is trying to push back.

Kerry St. Pé, director of the Barataria-Terrebonne National Estuary Program, says sediment diversions from the river won't work because the Mississippi no longer carries enough sediment; it's captured behind dams far upstream. "To rely on the river to recreate the delta is not going to happen," St. Pé says. He favors piping dredged sediment to the most vulnerable parts of the delta.

"We have sediment being dredged all the time for navigation on the Mississippi River," St. Pé says. "Right now they take it offshore and dump it! We need the sediment; we need elevation. And the only way to get that is to harvest sediment and to pump it to repair what's there now and to restore what we've lost.

"We know what these features were, and we can try to re-create as much of that as we can. Where there were marshlands, restore marshlands; where there were ridges and barrier islands, restore ridges and barrier islands." St. Pé says sediment pumping restored Bayou Dupont, a 450-acre marsh that had been open water.

The CPRA master plan does include $20 billion for marsh creation projects like that. But the agency and the scientists who devised the plan maintain that Louisiana will lose its battle against the sea without projects that divert sediment from the Big Muddy River. By channeling as much as 250,000 cubic feet per second through gaps in the levees, the diversions would get much more mud for the buck than dredges and pipelines.

Implacable Sea

To achieve its goal of stopping the loss and achieving a net gain in land within 50 years, Louisiana needs not just $50 billion and a lot of mud. It also needs a relatively optimistic scenario of future sea-level rise to come true.

"I think it's extremely unlikely that we'll go back to a situation of net land gain," says Torbjörn Törnqvist, a geologist and climatologist at Tulane University who, like St. Pé, worked on the master plan. "Climate change is working against us.

"Within restricted areas you could have a net gain, but for the Louisiana coast as a whole I think that's virtually impossible to achieve," he says. "Which means we're going to have to make very tough choices. There will be significant areas that will have to be abandoned. Politically that's tough, but it's inevitable."

It's all but certain that sea level will continue to rise for generations to come; if we don't control the heat-trapping gases that cause global warming, disaster awaits all the world's coastal cities.

"We're setting ourselves up for melting large parts of Greenland and West Antarctica," says Törnqvist. "It may take a number of centuries for this to play out, but when those things start to happen, it's going to be game over here in New Orleans. But don't forget, it's going to be game over in New York City as well, and every other coastal city in the world."

At Jean Lafitte, park officials recognize that their park might not be around in 2100. "In the meantime, how do we best manage?" Whitbeck asks. "What do we want the landscape to be while we're subsiding?"

St. Pé, however, whose family has lived on the delta for more than 200 years, bristles at the very notion of retreating. An entire culture is at stake, he says; the bayou culture, with its food and music, is the source of everything that draws people to New Orleans and the rest of the delta.

"We can't leave; we have no choice," says St. Pé. "It's much more than moving people out of here. It's all the infrastructure, all the industries, all the refineries. You'd have to move all of that, and that's not going to happen.

"It's easy for someone in some other place to talk about having a mass exodus from the area. But that's not going to happen. I say as soon as they move everyone off the San Andreas fault, and everyone in the Midwest out of tornado alley, then we can talk about moving us out of here too."

20 comments
Bellz Webster
Bellz Webster

50 billion won't save it. If this has been happening for that long a period of time, its just going to keep on happening. It would be better to move back to a much safer point and work on preparing that area for the years to come.

Chris McLindon
Chris McLindon

$50 billion would be better used to get people out of harms way.  Development should have never taken place in the coastal marshes to begin with.  We can wait for the inevitable change of course in the Mississippi and bemoan the "catastrophe" or we can begin to bring it about ourselves and move toward the natural restoration of the coastal marsh system with no controls on the River.  This will take decades, but the sooner we start the better.

Jeff G.
Jeff G.

The $50Billion would eventually sink along with the bayou and the delta upon which it sits. Deltas sink in accordance with the governing geologic process, and independent of climate change. There is no stopping it. Might as well spend another couple of $ Trillion on stopping continental drift or liberating Gondwanaland.

Cobra Choppergirl
Cobra Choppergirl

Just blow up the dams.   You don't need 50 billion to do that.  Get rid of the shipping lanes.  Let nature return to natural.   You have nobody to blame but yourselves.  

You want it back the way it was, then blow up all the things you did to subvert that, let them fall into decay, and let it go back to the way it was, and it will slowly heal itself.

Wallace Bradley
Wallace Bradley

We cannot stop the loss of the delta unless we allow the rivers to flow as they did before we forced them to our will. We will not do that. We will not stop the activity of man nor the cycle of nature that is giving us global warming. The sea will continue to rise, the land to subside, the rivers to run in the way we have made them & this place is doomed. Dumping 50 billion dollars into the sea will have no positive effect & will be wasted rather than put to use for something that would benefit people. We must learn that there are things we simply cannot do & cut our losses. We should focus on improvements to our country & our people that will have long lasting & positive effects. Education, healthcare, infrastructure, security, or the river will return to it's natural state & the delta recover because we will no longer exist.

Bruce Williams
Bruce Williams

Surprising that there is no mention of another major factor,  land subsidence from the extraction of oil over the last century.  

Wilf Tarquin
Wilf Tarquin

When you dam a river the delta sinks/gets washed away. This is not news, it's been known for decades.

craig hill
craig hill

Death is hard for the survivors to go thru, but when it's murder, as the death of the delta so happens to be, conscious killing, it goes beyond mere mourning, to anger.  Inasmuch as the representatives of the corporations responsible are also supposedly our representatives, we know where to go for vengeance: Remove these people at the polls and replace them with better.  Let's try representation by some actual humans for a change. 

Gregory S.
Gregory S.

It is ironic that the refineries are in large part responsible for the rising CO2 levels that are causing the rise in sea levels that will eventually sink the city. It is true that river diversions and sediment dredging will solve the current problems caused by short-sightedness, but not the big one that is slowly unfolding. It is only a matter of time (decades) before the city and federal government are forced to choose between abandoning the city or building enormously expensive towering sea walls to try to save it. I doubt that that such a project would be affordable and the fate of New Orleans is to  only exist in history books.

Robert Galin
Robert Galin

Bill Haber, AP cutline: The "urges" of public officials? Do you mean urgings?

Eric MacLaurin
Eric MacLaurin

I think they need to create specific areas that are dyked and flooded with silted water from the bottom of the river using a long pipe laid along the bottom of the river.  The dyked area should be big enough to allow the sediment to settle before clear water is allowed to flow naturally (via the new dykes and layout) back into the river.

You could divert the entire flow of the river several times if you keep returning it to the main channel.  Significant percentages of the extra nutrient load would also be kept from the gulf.  Constantly removing sediment from the bottom of the river in key locations could also eliminate the need for dredging.


David Eckel
David Eckel

Global warming related sea level rise seems to get most of the attention these days, including in this article.  Geologic subsidence was referenced but may not make the impression it should on most readers.  Large areas of the gulf coast are undergoing subsidence as a consequence (the theory goes) of ground water being pumped out to irrigate crops, cows and people.  Southeast of Houston for example you can see "christmas trees" (the valve complexes) atop oil and gas wells drilled decades ago hanging sometimes ten to 15 feet in the air.  When installed they were at ground level, meaning the surrounding land has sunk that much in ~80 years.  They're anchored miles down so they aren't getting pushed up.

I don't know if that makes any difference in the decision whether to try and defend against a relentless gulf by spending huge amounts of money, or to bite the bullet and move out of the way. I am sympathetic to the plight of the lowlands, but it does occur to me that the decision about what to do is often influenced to a great degree by whose money is being spent.

garret graves
garret graves

Sediment diversions are working today in Louisiana.  See Wax Lake Outlet, Atchafalaya River delta, and West Bay diversion.  In the weeks that Bonnet Carre diversion was opened in 2011, an estimated 9 million cubic yards of sediment was deposited there.  These aren't experiments, they are working today.  We're going to save this place and are well on our way already. Just need BP to clean up their oil and "make it right" rather than continuing to run from their responsibilities.  

Sacrificing the fishing isn't an option.  We can restore the wetlands and create more fish habitat.  see the Master Plan: www.coastal.LA.gov

Dietrich Bartelt
Dietrich Bartelt

@Wallace Bradley Hello Wallace, you are right: using water as drinking water, irrigation water or for hydro power generation, including building a dam, has an impact on the river as an ecosystem. To keep the river in balance and to allow natural development of the river, there is a need to compensate that impact. There are ways to do that without harming nature, allowing the use of water and that are affordable.

Chris McLindon
Chris McLindon

@Bruce Williams The engine of subsidence has been running for 50 million years in south Louisiana.  Sediments once deposited at the surface are now 6 miles deep.  Sedimentation by the River has always been able to keep pace with subsidence until it was stented by levees.  The marshes of Plaquemines and St. Bernard are following a natural pattern of deterioration.  What is not happening is the building of new marsh in the Atchafalaya Bay.  This is a case of sediment starvation.

Wilf Tarquin
Wilf Tarquin

@Gregory S. It's got nothing to do with rising sea levels (the sea has so far risen about half an inch), and everything to do with dams.

When you dam a river you stop the sediment. When you stop the flow of sediment, the river delta sinks below the sea. That's all there's to it.

Chris McLindon
Chris McLindon

@Eric MacLaurin You can' dig your way out of a hole, and you cant engineer your way out of this problem.  We need to work toward getting people out of the way so that all controls on the River are removed.

Dietrich Bartelt
Dietrich Bartelt

@Gregory S. The delta sinks, only, if the impact of using water along the river is not compensated. If you do the compensation (continuous sediment transfer instead of taking it out or holding it back) than you can save the delta from sinking and dieing.

Gregory S.
Gregory S.

@Wilf Tarquin @Gregory S. 

The point of my post was to differentiate between the short term and long term problems. The outlook is optimistic in the short term with current measures, but pessimistic in the long term.

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