Why Louisiana Is Sinking

BY Rebecca Jacobson  May 30, 2012 at 4:13 PM EST

On the NewsHour this week, we will be covering how rising sea levels are threatening people who live on the fragile Louisiana Delta. Hari Sreenivasan spoke with Torbjörn Törnqvist, a coastal geoscientist at Tulane University who studies the evolution of low-lying coastal wetlands, about the dilemma in Louisiana.

Video clips in the interview are courtesy “Turning the Tide,” a Louisiana Public Broadcasting documentary about the critical situation facing the Gulf Coast.

Törnqvist said over the past 100 years, the sea level rise associated with climate change has crept up on the Gulf Coast. But rising oceans aren’t the only reason the Delta is disappearing. Man-made levees, diversions along the Mississippi River and oil drilling along the coast have contributed to rapid subsidence, sinking the marshlands without new silt to replace it. He said the problem has increased to a rate where the delta loses roughly a football field worth of land every half hour to an hour.

HARI SREENIVASAN: When it comes to sea level rise and subsidence, these are massive shifts that have been happening for quite some time. And is there a climate connection to it at all?

TORBJÖRN TÖRNQVIST: The thousand-year period prior to the industrial revolution, the rates of sea-level rise along the Gulf Coast, this larger area from the Florida Panhandle to East Texas, was about five times lower than it has been in the last century. And there is no doubt that that is a direct implication of climate change, because it actually reflects what we see worldwide. And if we go forward, we know that sea-level (rise) will continue to accelerate. The only thing there is uncertainty about is how large that continued acceleration will be. But I think the important thing we know now is that, even in the past century, accelerated sea-level rise has already contributed to the loss of these wetlands. It’s not been the major factor, but going forward, it will become an increasingly important factor, and ultimately it could very well become the single most important factor.

HARI SREENIVASAN: So when we look at the Southern Louisiana coastline, in somewhat simple terms, what’s happening to it?

TORBJÖRN TÖRNQVIST: One hundred years ago, things started changing very, very fast. And the initial reason for that was that we built levees along the Mississippi River for flood control. And we obviously needed that, but it had one really negative unintended consequence, and that was that that sediment did not make it to the Delta anymore. And as a result, the, the sinking, and rising sea level continued, and as a result we started literally losing land that simply drowned. And that rate of land loss has, over time, increased to rates on the order of, say, a football field every 30 to 60 minutes.

HARI SREENIVASAN: So are you concerned in the terms that so much of Louisiana is so low that these incremental, I mean an eighth of an inch or whatever it is, is pretty hard for most Americans to get theirs heads around, “So what if an eighth of an inch on a coast, you guys have tons of marshes, so we lose some marshes.” How significant could that impact be in Louisiana?

TORBJÖRN TÖRNQVIST: The real challenges we’re going to face are ultimately not going to be this very gradual rise of sea level. What’s going to happen is we’re going to become more and more vulnerable to big events, and in our case, large hurricanes. So you have to think about it this way, that imagine a similar hurricane to Katrina, but with sea level around this region that is one or two feet higher than it was during Katrina. The impact will be even much worse than Hurricane Katrina itself. And I think that’s, that’s basically a principle that applies not just here, it applies around the world,

HARI SREENIVASAN: The coastal communities that we met yesterday, should they pack up and leave? Is it an inevitability that their land will be covered with water in a period of a few years or decades?

TORBJÖRN TÖRNQVIST: People tend to view New Orleans and the surrounding delta as some kind of unique area that is extremely vulnerable and that was maybe never meant to last. But whatever happens here is simply a predictor of what’s going to happen in other low-lying coastal areas later this century. And then we start talking about cities like, you know, Miami, New York City, Manhattan, that are also very vulnerable. They are not at the stage where we are right now, but they will get there.

HARI SREENIVASAN: Our series primarily focuses on communities and how they’re adapting. When you look at these kind of statistics, when you look at these sort of trend lines, and conservative as well as less-optimal projections in the master plan, how does Louisiana get through this?

TORBJÖRN TÖRNQVIST: Louisiana is now moving to the point that it recognizes that there is no way we can save the coast, even as it is today. You know, we don’t even talk anymore about restoring what we had, say a century ago. But even what we have today is not, it’s not going to be possible to keep, keep it the way it is. So we’re going to have to make very difficult choices and focus on trying to restore certain portions of the coast, which inevitably will go on the expense of other portions of the coast. And that’s, that’s a very difficult political problem. But it is one that has to be addressed, and it has to be addressed very soon. Because the longer we wait, the less we will be able to do.

Tune in to Friday’s broadcast to see our report on coastal erosion in Louisiana.