Re-engineering the Mississippi River will stem catastrophic economic and environmental losses from human development and climate change while raising billions of dollars in value, according to a report released yesterday.
The paper, titled "Answering 10 Fundamental Questions about the Mississippi River Delta," highlights the need to protect against land losses and preserve ecosystems along the Gulf Coast. Scientists and engineers from environmental advocacy groups and research institutions contributed to the report, noting that a quarter of the land on the bayou has eroded over the past 100 years, which they attributed to activities like damming the water for energy and flood control, dredging the riverbed for shipping and diverting the river for irrigation.
These actions halved the amount of sediment flowing into the delta to replenish the landscape, and if the process continues unabated, thousands of square kilometers of land will wash into the ocean, with more than $350 billion in losses over the next 20 years, according to the report. Meanwhile, sea levels are rising and weather events like hurricanes are becoming more extreme, accelerating the process and threatening to submerge cities like New Orleans.
This was described as having huge repercussions, not just for Louisiana but for the United States as a whole. "The Mississippi Delta is phenomenally important to the nation," said Sam Bentley, one of the report's co-authors and a professor specializing in sediment in the Department of Geology and Geophysics at Louisiana State University.
He explained that the region is critical for offshore oil drilling and is a transit route for close to 20 percent of America's shipping and navigation, particularly for grain from the Midwest. The waters provide one-third of seafood tonnage served in the United States, and many species spawn over the silt near the mouth of the Mississippi.
But the delta's 2 million residents have watched the sand beneath their feet washing away over the years, with no end in sight. The delta constantly gains and loses land, but losses have drastically outpaced gains.
A 2009 study by Michael Blum and Harry Roberts in Nature Geoscience found that the delta could lose up to 13,500 square kilometers of land by 2100. Many have already left the region, fearing for their homes and their jobs, in the aftermath of Hurricanes Katrina and Rita as well as the Deepwater Horizon oil spill.
'A state of environmental decline'
"[The delta is] in a state of environmental decline that threatens a large amount of commerce and ecosystem services," said Bentley, who co-authored the report. "Even if there were no climate change, even if we were in a steady state right now, the delta would continue to subside and erode into the ocean." This will raise fuel prices, hamper the economy, reduce biodiversity and threaten food security.
"By letting this system completely collapse, you lose a lot of those economically important species," said Alisha Renfro, a coastal scientist with the National Wildlife Federation. In addition, without the delta as a shield, the coast along Louisiana and Mississippi is more vulnerable to storms and saltwater intrusion.
The report calls for an all-out approach that includes mitigating the damage, restoring land and adapting to a new normal. "The situation is so dire that all the tools in the toolbox need to be used," said Angelina Freeman, a coastal scientist at the Environmental Defense Fund and a co-author.
One strategy is to mimic how the river picks up sediment upstream and deposits it on the delta. John Day, a professor emeritus in the Department of Oceanography and Coastal Sciences at LSU, said that upstream water can be routed into wetlands and then back into the river "to restart the natural function of the delta." Engineers can also construct bypasses that allow sediments to flow around obstructions like dams on the Mississippi.