Mississippi River Delta Is In Jeopardy – Undoing Decades of Flood Protection Could Save It

Restoring coastal Louisiana requires balancing wetland restoration, flood control, sediment delivery, nutrient management, hypoxia mitigation, and the health of coastal Fisheries. For example, the Mississippi River Sediment Delivery System-Bayou Dupont project, before (top) and after (bottom). (Credit: USGS National Wetlands Research Center, Lafayette, Louisiana)

The Mississippi River Bayou Dupont diversion project     Credit: USGS National Wetlands Research Center

By Julia Fine, ODP Contributing Writer

A new study released earlier this summer found that the “marshes in the Mississippi River delta have hit a tipping point.”  The study, which looked at “marsh records that stretch much of the Holocene,” showed that the Mississippi River Delta will be destroyed this century because of rising sea levels unless we reduce greenhouse-gas emissions worldwide and keep global temperatures closer to where they are now. The state of Louisiana has a Coastal Master Plan to build major sediment diversions to help keep the wetlands above water. These diversions will “undo” levees and channelization that were built to provide flood protection without any consideration for the health of the wetlands.  

Why This Matters: Coastal marshes are “among the most valuable ecosystems on the planet” due to their vital contributions to storm protection, nutrient cycling, and more. While the study paints a grim picture of the future of the Delta, the lead author told Nola.com, “It’s important to highlight the fact that it still depends on our actions…If we take appropriate actions and we can keep that rate of sea-level rise at least a little bit in check, it’s likely the wetlands are still going to drown eventually, but maybe over centuries.”  The planned river diversions are “revolutionary” – now scientists believe we must flood the Delta to have a chance to save it. And farmers all along the Mississippi River must change their practices too, for it to have a chance.

Historicizing Climate Change

The study examined the 8,500-year rate of sea-level rise that has already induced the drowning of wetland on Louisiana’s coast. Based on these records, it found that “at rates of relative sea-level rise– meaning the combination of rising water and ground subsidence– of 6 to 9 millimeters a year, the Gulf’s marshes would disappear underwater within a half-century,” Yale E360 noted. While recent rates of sea-level rise have been measured at about 3.58 millimeters per year, subsidence is not included in that measure, and this rising will only accelerate due to human-induced climate change. 

Saying No to Inaction

While the study concluded we are past the tipping point, the lead author Torbjörn Törnqvist told Nola.com that this cannot paralyze us into inaction. One important step towards that would be to build on and execute Louisiana’s 2023 Coastal Master Plan, which builds on a previous plan of the same name. This plan involves the “collective efforts of project investments [to] reduce storm surge-based flood risk to communities, provide habitats to support an array of commercial and recreational activities, and support infrastructure critical to the working coast.” Coupled with the reduction of greenhouse gases globally, this could help lengthen the life of the marshlands there. However, many have argued that “the master plan does not go far enough in addressing existential issues like the future of New Orleans,” suggesting more radical measures must be taken. 

Larger Implications

But the study doesn’t only implicate the Mississippi River Delta. What is suggests is much more ominous. The findings, as the authors note, “raise the question whether coastal marshes elsewhere may be more vulnerable than commonly recognized.” This is yet another demonstration of the need to take concerted, unified action on climate change lest these important ecosystems be destroyed.  And the health of the Delta is ultimately dependent upon changing farming practices all along the Mississippi River.  

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