Much ado about the causes of wetland loss in Louisiana

You might remember that last summer, the levee board responsible for protecting much of metro New Orleans filed a landmark lawsuit against some 90 oil and gas companies. The Southeast Louisiana Flood Production Authority - East (SLFPAE), formed after Hurricane Katrina in 2005, claimed that the canals these companies carved across coastal wetlands to set up drilling operations were significant drivers of wetland loss in the area historically, losses which could have mitigated storm surges. Pointing to industry, government, and academic reports alike they claim that the companies have not fulfilled their responsibility to fill in the canals and restore exploration and drilling sites. 

Wednesday, in a must-view PowerPoint presentation to the state's Coastal Planning and Restoration Authority (CPRA), SLFPAE made a pretty compelling defense of their case. What they did was zoom in on one particular case - the Delacroix area in St. Bernard parish - where canals have led to saltwater intrusion, erosion, and ultimately the conversion of marsh and swamp land into open water. I've gathered the slide by slide time series they presented into a handy GIF to illustrate their argument:

Wetland loss between 1956 and 2008 in the Delacroix, LA area. Canals that were dredged in order to move oil equipment are drawn in red arrows. Source: SLFPAE presentation.

You can see the same result when we focus in on just the past fifteen years With Google Earth imagery, I created another GIF that spans every other year or so from 1998 to the present.

Wetland loss between 1998 and the present in Delacroix. Source: Google Earth.

CPRA's chairman, Garrett Graves, however, is not so convinced by SLFPAE's argument. He thinks that going after the hydrocarbon industry is misguided. Instead, CPRA intends to sue the Army Corps of Engineers to get that agency to own up to the role that the Mississippi River Gulf Outlet (MRGO) shipping channel played in altering hydrological regimes in the wetland complex east of New Orleans and in shuttling Katrina's storm surge straight into the city. The meeting yesterday was just the most recent and most visible skirmish in a war of words between CPRA and SLFPAE over whether the SLFPAE lawsuit is legitimate and whether CPRA's approach would be more effective.

At first glance, it seems like SLFPAE and CPRA's disagreement is mainly over what they see as the causes of wetland loss in the area. SLFPAE points at oil/gas companies and their extensive network of canals; CPRA the corps and MRGO. But this is not just a debate about who's to blame. As SLFPAE's lawyers pointed out in their presentation, Graves himself has repeatedly acknowledged the part played by the hydrocarbon industry's canals. Everyone agrees, to a significant extent, that the problem has multiple drivers, whether they're as prominent as MRGO or as ubiquitous as oil/gas canals. The two institutions primarily disagree about what's the most politically and economically beneficial line of attack to solve the problem. SLFPAE says getting oil money can more than pay the bills on the state's ambitious $50 billion dollar master plan for coastal restoration; Graves seems to think that would result in less money going to communities for restoration. Obviously, the choice of who to blame has meaningful consequences for what gets fixed, but it'd be a mistake to think that one side doesn't get the ecological reasoning of the other.

Speaking of who to blame, take another look at the second GIF. If you didn't already notice it, much of the conversion of the Delacroix wetlands into open water happens between 2004 and 2005 (the pic that year was taken in October). Of course, as the first GIF demonstarted, wetlands loss had been occurring there for decades by then. But Katrina appears to have been the coup de grace. Research has shown how hurricanes and other weather events lead to wetland loss: the wetlands in Louisiana east of the Mississippi River lost up to 25% of their land area after Katrina. The presence of canals undoubtedly exacerbated Katrina's effect here, but the storm itself nevertheless has had a singular and lasting effect on the landscape. 

The easy thing to do is wonder whether all the money the state plans to spend to rebuild barrier islands and wetlands will just be washed away by the very storms they are meant to mitigate. The tougher and more important question to ask is whether decision-makers and conservationists realize this and are prepared to engage in a continual investment to redesign a landscape shaped by climate change.