Research from scientists at Indiana University and Louisiana State University reveals new information about the role humans have played in large-scale land loss in the Mississippi River Delta — crucial information in determining solutions to the crisis.
The study compares the impacts of different human actions on land loss and explains historical trends. Until now, scientists have been unsure about which human-related factors are the most consequential, and why the most rapid land loss in Barataria Basin, a key part of the Mississippi River Delta occurred between the 1960s and 1990s and has since slowed down.
It is tempting to link the land loss crisis to dam building in the Mississippi River Basin — after all, dams have reduced the sediment in the Mississippi River substantially, says Doug Edmonds, the Malcolm and Sylvia Boyce Chair in the IU Bloomington College of Arts and Sciences' Department of Earth and Atmospheric Sciences. Building levees and extracting subsurface resources have created more land loss and, according to their research, building dams has had a smaller effect.
The current Mississippi River Delta formed over the past 7,000 years through sediment deposition from the river near the Gulf Coast. But due to human efforts to harness the river and protect communities, the delta is no longer accumulating sediment. As a result, coastal Louisiana has lost about 1,900 square miles of land since the 1930s, according to the Louisiana Coastal Protection and Restoration Authority.
There is no one cause of the crisis, Edmonds said. But many researchers believe it is the result of different human interventions in the delta, including dam building, flood control levee installation and subsurface resource extraction.
The study found that only about 20% of the land loss is due to dam building, while levee building and extracting subsurface resources like oil and gas each account for about 40% of the Mississippi River Delta land loss. The study also suggests that the most rapid land loss and the recent deceleration might be related to the reduction of subsurface resource extraction.
To conduct their study, researchers re-created the land loss for an area in the Mississippi River Delta called the Barataria Basin. They used a model that describes the sediment budget, which is the balance between sediment flowing in and out of a coastal system. Using that model, they quantified the impact that building dams and levees and extracting subsurface resources had on land loss.
The researchers say this study emphasizes the importance of doing a broad systems analysis of complex problems, so there is increased confidence in the solutions being proposed to reverse land loss and protect our land and people.