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From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.

One big concern as Hurricane Gustav tosses wind and water at the Gulf Coast is the state of the coastal wetlands. As with Katrina and Rita, the power of this hurricane has been amplified by the loss of those wetlands. And coastal oceanographer Robert Twilley of Louisiana State University joins us from Lafayette to talk about that. Thanks for being with us.

Professor ROBERT TWILLEY (Coastal Oceanographer, Louisiana State University): Thank you.

BLOCK: And if you look, Robert, at the most severe land loss that you've been seeing over time in coastal Louisiana, how is it matching up with the point where this storm came ashore in Terrebonne Parish?

Prof. TWILLEY: Without a doubt, the storm, you know, rolled in right in the bull's eye, if you will, of where we've probably seen some of the most dramatic wetland loss in the entire state.

BLOCK: And when you say the most dramatic wetland loss, how much are we talking about?

Prof. TWILLEY: Oh, a million, you know, acres over the last hundred years, and then there's something like 17 square miles per year, say, over the last decade. So it's been quite dramatic. Values going anywhere from, you know, a football field every 30 to 40 minutes.

BLOCK: What are the main factors behind that erosion and loss of wetlands?

Prof. TWILLEY: Well, this is the Mississippi River delta. It relies on the river. It is the source of freshwater and sediment and silt that built this delta over 6,000 years. Particularly since 1928, we've leveed that river. We simply divert that freshwater and silt out into the Gulf of Mexico. And instead of having these natural flooding events that deliver that sediment into the flood plain, nourish the wetlands, you know, so they can grow and keep up with sea level rise, we've limited that resource.

BLOCK: There is another issue here, and you and I talked about this just about this time three years ago after Katrina, and that is shipping channels that have been dredged through these wetlands for oil and gas exploration, giving companies easy access to the Gulf. Why don't you explain how those channels affect wetlands over the long term and would help make a storm like this one worse?

Prof. TWILLEY: The channels are critical for transportation relative to the economic activities of this working coast; they give business and economic activity access. Well, during a storm like this, it also brings an access to interior parts of the state and the interior part of the wetlands to storm surge and to salt.

BLOCK: Are there moves to put to shut some of these channels down?

Prof. TWILLEY: You bet. Most notorious is MRGO or Morganza to the Gulf Outlet - that, after Hurricane Katrina, has been de-authorized and will be shut down. And there are other channels, one right in the bull's eye, actually, here, of this storm, that there have been plans on the books to try to redesign a feature such as a lock, and that's the Houma Navigation Canal, that runs right up into Houma. There have been plans to put a lock on that system to protect Houma and the citizens from storm surge and saltwater intrusion. [POST-BROADCAST CORRECTION: MRGO stands for Mississippi River Gulf Outlet.]

BLOCK: Mr. Twilley, are there, do you think, communities that if you look at a map right now of Southern Louisiana, you would see an outpost at the very fringe of land hanging into the Gulf, a town like Cocodrie where Gustav came ashore today, that won't be there some time from now? If you were to look at a map maybe 10, 15 years from now, that town just won't exist?

Prof. TWILLEY: Well, you know, business as usual in this state and in a place like Cocodrie is going to have tremendous consequences and in fact, it's going to require people to really consider retreat. You know, without a very strong restoration program, particularly in the area that Gustav came ashore, and with some elements integrated with protection, then these are communities that are threatened, without a doubt.

BLOCK: Well, Robert Twilley, thanks for talking with us. Appreciate it.

Prof. TWILLEY: Thank you.

BLOCK: Robert Twilley is director of LSU's Coastal Sustainability Initiative. He spoke with us from Lafayette, Louisiana.

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