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Flyfishing in Saltwaters Aug Sept 2009

 

DISAPPEARING ACT

After decades of human interference, Louisiana’s marshes are in deep trouble

 

Louisiana is well known for its diverse and abundant fisheries, famous not only for its shallow-water redfish and speckled trout fishing, but for its extraordinary offshore opportunities.   All are dependent on Louisiana’s marsh.  

 

Louisiana’s 5727 square miles of coastal marshes constitutes the largest contiguous wetland system in the lower 48 states, but it is losing ground to the Gulf of Mexico at an estimated rate of 25 square miles a year.   By the year 2050, Louisiana could lose another 435,000 acres.  If nothing is done, the entire area could be gone by 2075. It is a crisis of epic proportions, and not just for anglers. 

 

The vast wetlands system is of huge ecological importance.  Such environments are perhaps the most rich and productive in the world.   When the Mississippi River collides with the Gulf of Mexico’s saltwater, tidal counterforce forces the river’s waters to slow and drop suspended sediment, to form deltaic marshland – a rich, fertile organic substrate that fuels the entire marine food chain, not just in the marsh but extending way offshore. 

 

More shrimp and crabs are found in Louisiana’s marsh than anywhere else in North America.  The marsh is a nursery not only for juvenile sport-fish, but for important baitfish like the Gulf menhaden. It is the base of a food chain that converts its rich supply of marsh plankton and detritus into sustenance for larger fish, birds, and of course humans.  As we continue to lose wetlands, that chain can only become far less productive.

 

There are serious economic implications as well.  The area is home to the largest port complex in the U.S.  It is the gateway for some 27% of the nation's oil & gas. As the wetlands and barrier islands disappear, oil and gas infrastructure as well as ports along the coast are becoming frighteningly exposed to open Gulf conditions.  Wells, pipelines, ports, roads and levees are quickly becoming vulnerable and there is heightened potential for massive oil spills.  

 

The coastal wetlands also provide hurricane protection to some 2 million citizens living in the area. Marsh and barrier islands are the natural line of defense against hurricanes and storm surges.  Scientists estimate that every 2.7 miles of wetlands absorbs almost one foot of storm surge. Thus, about 80 miles of restored coastal marsh below New Orleans would have prevented most of the flooding form Hurricanes Katrina and Rita.  And, according to estimates by U.S. Geological Survey, Katrina and Rita wiped out some 200 square miles of marsh in one fell swoop. 

 

In addition to such grand scale marsh loss, a variety of forces have been at work against Louisiana’s coastal marsh for decades.  The first is subsidence.   As the weight of overlying sediment bears down, the mud in the marsh naturally settles under its own weight, and the whole delta sinks.  For thousands of years, this sinking as well as sea-level rise was more than balanced by the constant addition of new sediment carried down by the Mississippi.   When the river flowed naturally, regular floods carried silt from the heartland into the marshes, maintaining their elevation.

 

Yet, in the last century, we've spent billions of dollars to tame the Mississippi in the name of flood control and improved navigation.  While the river’s channel, and  in some cases the river itself, used to swing back and forth during floods, breaking apart and carrying vast amounts of sediment and silt with it, it is now contained by an extensive levee system from St. Louis nearly to the Gulf.   Each pulse of floodwater used to reshape the delta.  Each time the river channel shifted, its sediment-laden water built new marsh.   Today, the constrained river carries the silt straight down the channel.   South of Venice, the river's marsh building sediment settles. Yet this is where the continental shelf ends and deep water begins.  The levees effectively force the river's sediment load to be deposited and lost in several hundred feet of water.  Thus, the rates of subsidence and erosion now greatly exceed marsh creation.  

 

Dams built on the upper river and its tributaries contribute to the problem as well.   They trap sediment, reducing the amount arriving at the mouth of the Mississippi by more than 70 percent.  Oil and gas development added greatly to the situation.   Oil companies built thousands of miles of canals to extract and transport oil and many of these channels were connected to the Gulf, thus allowing saltwater to flow into interior fresh/brackish water marsh.  Plants intolerant of high salinity died off in mass, and tidal energy and wind-generated wave action were able to erode the marsh and convert it to open water before saltwater plants could establish themselves.  

 

Non-indigenous species such as the nutria, a rat-like animal that forages on aquatic plants, by some estimates is responsible for up to 40 square miles of Louisiana marsh loss per year. According to researchers from Brown and Louisiana State universities marsh-grass-eating periwinkle snails are to blame as well.

 

What’s being done

 

Natural and historic flows of silt from the Mississippi River into the marshes needs to be restored on a grand scale if there is to be any hope of preservation.  Diversions must be designed and engineered to spread water, sediment, and nutrients into targeted areas, providing marshes with the raw materials needed to regenerate. In areas that cannot be reached by such direct diversions, spreading sediment via pipeline may prove to be a viable option. 

 

The Corps of Engineers has recently helped build such high-tech diversions to lift fresh water and sediment out of the river, over the levees, and into the surrounding marsh.   Lower tech approaches are also being developed.  The Louisiana Department of Wildlife and Fisheries and a number of partners are experimenting with breaks in the natural levees along the Mississippi. These breaks, called "crevasses," allow fresh water and sediment to flow out into the marsh. As the water slows, the sediment drops to the bottom, creating a micro-delta that quickly develops its own marsh vegetation. 

 

The coastline must also be shored up through barrier shoreline and other restoration projects that prevent further loss and keep the skeleton of the ecosystem functioning.  “Duck-wing terraces" like those funded by Ducks Unlimited along the Chenier Plain protect marshes from wave action and erosion.  Grassland and oyster reef restoration programs being employed across the coast help protect interior marshes as well, and there are numerous dredge-and-fill projects.   

 

All such initiatives have to be small enough to be feasible as well as locally acceptable.  Thus, the problem is a matter of scale. While folks are working hard to create hundreds of acres of new marsh, tens of thousands of acres are being lost. Many scientists claim that it would be near impossible to keep up with what has become an extraordinary rate of marsh loss, unless there was a massive infusion of funds and a big commitment from both state and federal agencies.   Taking the measures that would change the flow of water and sediment over a huge area would be an endeavor that would rank as one of the largest civil works programs in the nation’s history. 

 

It's been estimated that such a program will cost $14 billion, but the cost of losing the marsh to the Gulf of Mexico is far greater.  By some estimates, such a loss would add up to $37 billion in “public use value”.  This is the estimated value of what we all stand to lose in commercial fisheries,  recreational hunting and fishing,  hurricane protection, navigation and port facilities, oil production infrastructure, water-quality function and other functions the Louisiana’s marsh provides.

 

A coalition of conservation groups and government agencies called America's Wetland is trying to convince Congress to throw its weight behind the effort and to some extent they have been successful.  In 1990, Congress passed the Coastal Wetlands Planning, Protect and Restoration Act (CWPPRA) and in 2007 the Louisiana Legislature approved the Act’s master plan for coastal restoration and hurricane protection. The master-plan is the first document to completely incorporate hurricane protection projects with projects aimed at rebuilding Louisiana's rapidly eroding coastal marshlands. It reflects more than 18 months of research, stakeholder and scientific review.  It will be the guide for all coastal restoration and hurricane protection efforts in Louisiana over the next several decades.   As of 2008, there are 145 active CWPPRA projects. 

 

In 2005, the Louisiana legislature passed a Constitutional Amendment to dedicate 100% of all future Federal Outer Continental Shelf (OCS) oil and gas revenues to be "used only for the purposes of coastal protection, including conservation, coastal restoration, hurricane protection, and infrastructure directly impacted by coastal wetland losses."  After many years of discussion Congress passed, in December 2006, the Federal Revenue Sharing Bill which allows for federal revenue sharing out of OCS revenues on new leases in the Gulf of Mexico.   

 

Because there has been widespread agreement that hurricane protection and coastal restoration objectives must be pursued, the Louisiana State Government as well as the Federal Government seems to be increasing the amount of funding they are throwing at the problem each year.  Whether or not it proves to be too little, too late has yet to be determined.