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

GARYVILLE, La. (AP) — Louisiana has long relied on a vast levee system to rein in the Mississippi River and protect surrounding communities from flooding. But cutting off the natural flow of the river with man made barriers has been slowly killing one of the nation’s largest forested wetlands.

The 176 square mile (456 square kilometers) Maurepas Swamp just to the west of New Orleans holds Louisiana’s second largest contiguous forest, a beloved state wildlife refuge filled with water tupelo and bald cypress trees, their branches adorned by wisps of Spanish moss. A beloved recreation site, the swamp also houses bald eagles, ospreys, black bears and alligators and serves as a waystation for hundreds of different migratory birds.

Deprived of nutrients from the stanched Mississippi River, the swamp’s iconic trees are dying in stagnant water. Yet they’re now set to receive a life-saving boost.

State and federal authorities on Tuesday celebrated breaking ground on an ambitious conservation project intended to replenish the ailing trees by diverting water from the Mississippi back into the swamp.

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

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

The River Reintroduction into Maurepas Swamp will allow for a maximum of 2000 cubic feet per second (57 cubic meters per second) to flow out of a gated opening to be built in the levee system and routed along a 5.5 miles (9 kilometers) diversion channel. The project expects to revitalize around 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.

Besides injecting much-needed nutrients and oxygen into the swamp, river water will leave thin layers of sediment deposits that mitigate the effect of subsidence — a natural phenomenon on Louisiana’s fragile coast exacerbated by fossil fuel extraction — and climate change-induced sea level rise, said Nick Stevens, a researcher at Southeastern Louisiana University’s wetlands ecology and restoration lab. Healthier forests bolster the swamp with decomposing matter from branches and leaves, he added.

“All of that is completely hindered by not having the Mississippi River attached to it anymore,” Stevens said. “You’ve got all this land sinking as a result of just not getting nutrients.”

The swamp’s diminishing health has had ripple effects on biodiversity, says Erik Johnson, director of conservation science at Audubon Delta, an organization focused on bird ecology in the Mississippi River delta. Some migratory birds like the yellow throated warbler, prothonotary warbler and the northern parula have had their populations plummet by nearly 50% in the past two decades, Johnson said.

These birds rely on caterpillars who are dependent on water tupelo and bald cypress foliage. When there’s less healthy leaves for the caterpillars to gorge on, there’s less food for the birds.

“That’s driving a really rapid decline in these bird populations that depend on this one forest,” Johnson said. “The whole system has shifted.”

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

Unlike the state’s controversial $3 billion river diversion project intended to combat coastal land loss, the Maurepas project has received widespread support from elected officials and local communities.

The Maurepas project is primarily funded by the Gulf Coast Ecosystem Restoration Council, a multi-state and federal program managing 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 building an adjacent 18.5 miles (30 kilometers) levee system to protect several southeast Louisiana parishes. The Corps will count 9,000 acres (36 square kilometers) of Maurepas Swamp restoration towards offsetting environmental damage caused by the new levee construction, meaning it can direct additional federal funds towards 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 with Gulf Coast Ecosystem Restoration Council.

And conservationists say the Maurepas reintroduction project highlights the importance of coastal protection and wetlands restoration going hand in hand in a hurricane-prone region.

“You’re going to have a healthier ecosystem on the outside of that levee, which means you’re going to have a better buffer for storm surge and it’s going to allow the levees to be more effective,” said Amanda Moore, National Wildlife Federation’s Gulf Program senior director. “This is how we need to be thinking at large about what’s possible and how we can how we can do more effective conservation by working with nature.”