To save a dying swamp, Louisiana aims to restore the Mississippi River’s natural flow

GARYVILLE, La. — Louisiana has long relied on one extensive dike system to contain the Mississippi River and protect surrounding communities from flooding. But cutting off the river’s natural flow with man-made barriers has slowly killed off one of the country’s largest forested wetlands.

The 176 square miles (456 square kilometers) Maurepas Swamp just west of New Orleans lies Louisiana’s second-largest contiguous forest, a beloved nature preserve filled with water tupelos and bald cypresses, their branches adorned with wisps of Spanish moss. A popular recreational area, the swamp is also home to bald eagles, ospreys, black bears and alligators and serves as a way station for hundreds of different migratory birds.

Deprived of nutrients from the gridlocked Mississippi River, the swamp’s iconic trees die in standing water. Yet they are now about to get a life-saving boost.

State and federal authorities on Tuesday celebrated the start of an ambitious conservation project aimed at replenishing ailing trees by diverting water from the Mississippi River back to the swamp.

“This is about reconnecting a natural system, essentially restoring what it used to be,” said Brad Miller, who has led the project for the state’s Coastal Protection and Restoration Authority since 2006.

Miller compared the $330 million river diversion to watering a garden: “The swamp needs river water to be a good swamp.”

The river’s reintroduction into the Maurepas Swamp will allow up to 57 cubic meters per second (2,000 cubic feet per second) to flow from a sealed opening to be built into the levee system and routed along a 9-kilometer diversion canal. The project expects to revive about 45,000 acres (182 square kilometers) of swamp in an area where less than a third of the forest is considered healthy, according to the U.S. Geological Survey.

In addition to injecting much-needed nutrients and oxygen into the swamp, river water will leave behind thin layers of sediment deposits that mitigate the effects of land subsidence – a natural phenomenon on Louisiana’s fragile coast exacerbated by fossil fuel extraction — and climate change-induced sea level rise, says Nick Stevens, a researcher at Southeastern Louisiana University’s wetlands ecology and restoration laboratory. Healthier forests strengthen the swamp with decomposing material from branches and leaves, he added.

“All of that is completely hampered by the fact that the Mississippi River is no longer connected to it,” Stevens said. “You’re sinking all this land as a result of simply not getting nutrients.”

The declining health of the marsh has had an impact on biodiversity, said Erik Johnson, conservation director at Audubon Delta, an organization that focuses on bird ecology in the Mississippi delta. Some migratory birds, such as the yellow-throated warbler, prothonotary warbler and northern parula, have seen their populations plummet by nearly 50% in the past 20 years, Johnson said.

These birds depend on caterpillars that depend on water tupelo and bald cypress foliage. If there are fewer healthy leaves for the caterpillars to eat, there is less food for the birds.

“That causes a very rapid decline in the bird populations that depend on this one forest,” Johnson said. “The whole system has changed.”

Scientists say they expect to see an increase in canopy cover and new tree growth within a few years of the project’s expected completion in 2028.

Unlike that of the state controversial $3 billion river diversion project The Maurepas project, aimed at combating coastal land loss, has received widespread support from elected officials and local communities.

The Maurepas project is funded primarily by the Gulf Coast Ecosystem Restoration Council, a multi-state and federal program that administers settlement funds from the 2010 Deepwater Horizon oil spill that devastated the Gulf Coast.

The Maurepas project benefits from an innovative partnership with the U.S. Army Corps of Engineers, which is constructing an adjacent 19-mile levee system to protect several parishes in southeastern Louisiana. The Corps will count 36 square miles of restoration of the Maurepas Swamp to offset environmental damage caused by the new levee construction, meaning it can direct additional federal funds to the diversion program.

“For every dollar the state can save here, they have more to invest” in other coastal restoration projects, said John Ettinger, director of policy and environmental compliance at the Gulf Coast Ecosystem Restoration Council.

And conservationists say the Maurepas reintroduction project highlights the importance of coastal protection and wetland restoration, which go hand in hand in a hurricane-prone region.

“You get a healthier ecosystem on the outside of that levee, which means you have a better buffer from storm surges and it allows the levees to be more effective,” said Amanda Moore, National Wildlife Senior Director of the Federation’s Gulf Program. “This is how we should generally think about what is possible and how we can achieve more effective conservation by working together with nature.”