MANCHAC — In the distance, a few wading birds drifted over the tree stumps in the Maurepas swamp; others perched in the bleached and broken boughs of a few dead cypresses. In places, the swamp and sky meet at the horizon, an open landscape devoid of the tall tupelos that once thrived here.

Conservation groups want to see the trees tower over the marshes once again. They have implored the state to fast track several environmental projects across south Louisiana, three of which would redirect water into the Maurepas Swamp. Some parts of the wetlands remain relatively healthy, but in many places the marshes have struggled, such as the land bridge that divides Lakes Maurepas and Pontchartrain, where environmentalists took members of the media on a tour this week.

Deb Visco Abibou pulled out a satellite map. She showed where loggers etched tracks across the earth as they dragged the hardwoods out.

"It scarred the wetlands permanently, as you can see," said Abibou, of the Coalition to Restore Coastal Louisiana.

The loggers left decades ago, but the trees have yet to come back.

The area has spent years cut off from the leveed Mississippi River and subjected to saltwater intrusion from infrastructure like the now-closed Mississippi River Gulf Outlet. With the closure of the MRGO, the water is getting less salty, and volunteers have begun to replant the cypresses. But more fresh water throughout the swamp would help support reforestation, environmentalists said.

Of the 124 total projects in the state's coastal master plan that was updated earlier this year, 79 are identified as restoration projects. Since the update, the five conservation groups involved — the National Audubon Society, the Environmental Defense Fund, the National Wildlife Federation, the Coalition to Restore Coastal Louisiana and the Lake Pontchartrain Basin Foundation — have combed through the plan and identified the projects they believe will have the largest-scale impact and can be implemented in the next five years, when the plan will again be reviewed.

Environmentalists praised the state's plan, which is "robust" and strongly backed by science, said Steve Cochran, associate vice president for coastal protection for the Environmental Defense Fund. His group just wants to make sure officials pursue the issues that will be sustainable and have the biggest effect as quickly as possible, especially now that projects can be funded with money from the Deepwater Horizon oil spill settlement.

"We don't have the luxury to go slow. We've got to move," he said.

A report the environmentalists issued Monday states that coastal land loss "poses a growing threat to some of the nation's most productive wildlife habitat, critical energy infrastructure, largest ports, busiest shipping corridors, leading commercial seafood producers, vibrant tourism economy, and other important business sectors. ... Without swift, decisive action and bold, large-scale restoration efforts, our coastal land loss crisis will only worsen."

Many of the projects they're championing are along the Gulf, but the scientists said it's also important to look inland. With so much coastal land being swallowed up due to subsidence and sea level rise, authorities also need to think of ways to protect the Mississippi River basin "from the top down," said Natalie Peyronnin, of the Environmental Defense Fund. That includes the Maurepas Swamp.

The swamp spreads across parts of five parishes: Ascension, Livingston, St. James, Tangipahoa and St. John the Baptist. Although it lies inland of the Gulf of Mexico, environmentalists say it's a vital part of the overall coastal system. They also point out that without intervention, sea level rise will eventually cause the gulf to spill over into Lake Pontchartrain, then rush through Lake Maurepas and absorb the wetlands, which would make French Settlement a nearly coastal community.

The Maurepas Swamp is a valuable natural habitat — about one quarter of the bird species native to the United States and Canada can be found there at some point during the year, said Erik Johnson of the Audubon Society. The swamp is home to creatures from bald eagles to the prothonotary warbler, which Johnson affectionately calls the "swamp canary" due to its bright yellow coloring and use to track the health of the ecosystem, like the proverbial canary in a coal mine.

But the swamps are important for the human denizens of Louisiana as well, said Lake Pontchartrain coastal sustainability program director John Lopez.

Wetland trees and brush dampen storm surges, the water that hurricanes heave from the Gulf onto land. Under the right conditions, even a Category 3 storm could wash out parts of the Baton Rouge suburbs. The Maurepas Swamp could help lessen the impact of storm surges from the New Orleans area to the capital region, the report issued by the conservation groups states.

The five conservation groups involved are urging the state to prioritize three projects that will help save those marshes.

One diversion would bring Mississippi River water up from the Garyville area, using the existing Hope Canal to deliver fresh water to the swamp. That project has gotten some support in the form of $14 million from the Gulf Coast Ecosystem Restoration Council to perform design and engineering work.

National Wildlife Foundation scientist Alisha Renfro estimated the entire project would likely cost about $180 million, but that when it's completed the diversion will be able to help 70 square miles of wetlands.

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"These diversions can do a lot of good without much water," she said.

The conservation groups also want the state to use some of its funding, like from the Deepwater Horizon settlement, to bring river water in from the west via the proposed Union Freshwater Diversion, which would split from the Mississippi near Burnside.

To the east, the state should prioritize the Manchac Landbridge Diversion, which would re-route water up from the river into the swamps that divide lakes Pontchartrain and Maurepas, where the wetland trees have been depleted, their report states. Redirecting river water will help encourage the new trees that volunteers have been planting the past few years, the scientists said.

Others would help restore sediment near the Chandeleur Sound and the Barataria Basin, build ridges in Terrebonne Parish, create marshes south of Abbeville and protect oyster reefs off the coast.

The full report is available online at mississippiriverdelta.org/files/2017/11/MRD_PriorityProjectReport.pdf

Follow Steve Hardy on Twitter, @SteveRHardy.