Louisiana Marshes May Be A Goner Due To Expected Sea Level Rise

Photo: Ben Depp, Sierra Magazine

A new study in the Journal of Science Advances concludes that the “drowning” of the roughly 15,000 square kilometers of remaining marshland in the Mississippi River Delta of Louisiana is “past the tipping point” and now “probably inevitable,” according to The Washington Post  The study’s authors conclude that the rate of sea-level rise in that region of the coast is now rising more rapidly than the low wetlands can withstand and so they will likely be gone within 50 years.

Why This Matters:  Louisiana has already lost one-fourth of the land in the Delta at the beginning of the last century.  This is the “sponge” that protects New Orleans from the brunt of severe storms and floods and is important for wildlife and for fishing, recreation, and tourism jobs in the region.  We have spent billions to create a channelized Mississippi River — a floating highway for barge traffic from the upper midwestern farms — and laid thousands of pipes for oil and gas in the region, but these have made the marshes sink even faster.  Indeed the study confirms that the Mississippi Delta experiences some of the highest rates of coastal wetland loss in the world.  We must either dramatically change the “plumbing” of the Mississippi River to create diversions or prepare to move everyone in that region to higher ground.

Louisiana Master Plan

The state of Louisiana is working to reverse much of the damage done by humans.  They have an elaborate plan to spend billions to try to reclaim some of the coastal wetlands using more sediment that comes down the Mississippi River by “diverting” it and allowing it to flow into the marshes more naturally.  The state is concerned about the more than 2 million people in the region. Louisiana’s working coast “annually sends more than $120 billion in goods and services to the rest of the United States and exports $36.2 billion internationally.”  And it is central to the nation’s oil and gas industry and fisheries — it supplies 90% of the nation’s outer continental shelf oil and gas, 20% of the nation’s annual waterborne commerce, and 26% (by weight) of the continental U.S. commercial fisheries landings.

How Do They Know?

The researchers spent years extracting hundreds of “sediment cores,” or thick cylinders of mud and peat, from across the Mississippi Delta. They used these samples to analyze the sediment to determine the history of the region stretching back thousands of years.  Consequently, they determined when the wetlands were created, and saw how after the last ice age much of the region was simply open water.  Donald Boesch, a professor of marine sciences at the University of Maryland who has closely studied the Louisiana wetlands, told The Post that the study is “well-documented, analyzed and reasoned,” also pointed out that the marshes have been less vulnerable in recent years than scientists expected for reasons that are not well-understood.  The authors are pessimistic that any short term slow down of wetlands loss is a sign of a change — they believe that it is inevitable that they will be submerged.

Graphic: State of Louisiana

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