DEBBIE ELLIOTT, host:
Cities and towns along the Gulf Coast have seen more than their share of destruction from hurricanes this month. But the land itself has suffered, too, in part because human activity has made the land less resilient. The marshes in Louisiana are of special concern. They're not only home to wildlife; they're also the best natural defense against future storms. NPR's Christopher Joyce visited those marshes and has this report.
CHRISTOPHER JOYCE reporting:
A big part of Louisiana floats. In the Jean Lafitte National Park, what looks like dry land is actually miles and miles of vegetation, sedges, myrtle, palmetto spread out like a pizza crust floating on two feet of water. David Muth climbs over a railing along a park walkway.
Mr. DAVID MUTH (National Park Service): This is a very thin mat, so I can't really stand on it. But...
JOYCE: It's kind of like a trampoline.
Mr. MUTH: Yeah, except that won't hold me up. Thicker areas will hold you up quite well.
JOYCE: Muth, a National Park Service scientist, bounces up and down a few times, and the mat rises and falls with his weight.
(Soundbite of Muth bouncing)
JOYCE: That's what it did when Hurricane Katrina drove wind and water into the park. It flexed. Many trees did not. Water oaks and tupelos sprawl across the wooden walkway. Dead leaves are everywhere. Spiders have already spun webs from upturned tree roots. But scientists here say the damage is not fatal.
(Soundbite of motor)
JOYCE: A short boat ride away, the story is less clear. There are large patches of open water that used to be covered with marsh. Scientists also worry about saltwater pushed in from the Gulf. That can kill freshwater plants. The scientists take a few water samples, and they show normal salinity, and that's good news. But these marshes are fragile. They've shrunk over the past few decades. Muth says they've been starved and cut up.
Mr. MUTH: We've so fundamentally altered the hydrology here. There's no river sediment coming in; there's no river water coming in. There are canals everywhere that have changed the volume and intensity of the tidal movements. And, in the meantime, we're sitting here watching the park wash away, retreating 35, 40, 50 feet a year on average on this shoreline and in a storm event like this, as you saw down there, retreating much further.
JOYCE: Plants need sediment to grow in, but the levees on the Mississippi River keep the sediment from spreading out over the land, as it once did during seasonal flooding. And marshes need fresh water to keep the salinity down. Scientists at the US Geological Survey say Katrina hammered an already struggling patient.
Mr. GREG SMITH (Director, National Wetlands Research Center, USGS): My name is Greg Smith, and I'm the director of the USGS National Wetlands Research Center in Lafayette, Louisiana. We can certainly tell you that there has been a dramatic loss of wetlands, local in some areas and much more widespread in others.
JOYCE: Smith says the huge fishing industry--shrimping, crabbing and shellfishing in particular--depend on a healthy coastline; so do millions of migrating birds.
Mr. SMITH: It's just phenomenal the numbers of birds that use this coast as a staging area and a wintering area for their survival. We have estimates of up to 167,000 birds per mile of coast per hour using these habitats.
JOYCE: Smith says Katrina dumped a huge pulse of the urban pollution into these habitats, lakes, marshes and the Gulf of Mexico.
Mr. SMITH: What we have now is a real mixture, a mixture like no one has ever seen, because it's municipal, it's industrial, it's household chemicals and it's microbial. So it's an unbelievable mixture of complex dimensions that we really don't have models to describe.
JOYCE: Much of what was in that water will settle in sediments. Some will stay there; some will get picked up by fish or birds and slowly accumulate in them. Smith, who worked on the chemical assessment of the Exxon Valdez oil spill in Alaska, says this is worse. In Alaska, it was just oil that got loose. Christopher Joyce, NPR News.
ELLIOTT: You'll find more in-depth coverage of Hurricanes Rita and Katrina at our Web site, npr.org. Transcript provided by NPR, Copyright NPR.
