Past time to do something

I only know the ecological science that read in the papers but this latest flap over whether or not river diversions will actually do more harm than good sounds like the same argument between oystermen and coastal scientists that has been holding up any sort of meaningful action for decades now.

LSU professor James Cowan Jr., a fisheries ecologist, said he was both amused and frustrated by the debate over the Caernarvon diversion “because it certainly wasn’t designed to be a restoration tool. It’s doing what it’s supposed to do (freshening water along the coast to increase the growth of oysters), but it’s not a good model to determine what a sediment diversion will do.”

He said the state's plan to move to sediment diversions is an attempt to “restart an interrupted delta cycle,” mimicking the way the Mississippi River built large segments of the state’s coastline before humans built levees to block spring floods and forced it to stay in its channel, rather than travel down the Atchafalaya delta.

But Cowan also warned that whether or not the diversions are built, the state’s fishers will see significant changes in the location of specific species, including oysters and fish. Even when the Mississippi delta was allowed to run free and contained more freshwater, the types of fish remained similar to today, he said.

Fishers have cited new research that suggests that releasing river water, loaded with chemical fertilizer runoff, into wetlands may only inflict more damage.

The New England study was led by Linda Deegan, an LSU alumna and now a senior scientist at the Marine Biological Laboratory at Woods Hole, Mass.* Her team meticulously added concentrated nitrogen and phosphorous to tides flowing into an unpolluted coastal salt marsh. The primary plant in that marsh – Spartina cordgrass – also dominates wetlands targeted for some river diversions south of New Orleans.

In the first few years of the project, the nutrients ignited an explosion of growth in leaves and stems, but by the fifth year the edges of the marsh began “literally falling apart,” said team member John Fleeger, a professor emeritus at Louisiana State University. The pollutants weakened the root structure and speeded decomposition of the organic soil. The combination of stunted, weakened roots and less stable soil led to increased erosion from regular tidal currents.

This argument gets even more complicated. We already understand that fertilizer runoff is a problem.  US agricultural production  is dependent upon highly explosive nitrogen rich chemicals.  These chemicals runoff into the Mississippi River which, in turn, dumps it into the Gulf. The chemical spill off is known to be the cause of a massive hypoxic "Dead Zone" which appears annually off the Louisiana coast.

Interestingly, it's even been suggested that river diversion projects will help reduce the Dead Zone by allowing the marsh to filter nutrients from the water.

Also, Louisiana, through its master plan for coastal restoration and protection, is planning a number of freshwater and sediment diversions that could put some of the river water into the marsh where plants could remove some of the nutrients in the water, he said
.
“We wanted to make sure those diversion projects were part of the solution,” Raynie said.

For the Louisiana, though, it's past time for some solution, even an imperfect one, to move from the argument to the action phase.  We'll never know which side of this debate was correct once the coast has melted away into the ocean.