It’s a Twelfth Night tradition almost as dear to New Orleanians as getting the season’s first king cake: dragging the Christmas tree to the curb so it can be used to rebuild Louisiana’s eroding wetlands.

The annual rite is probably the most hands-on way most of us get involved with coastal restoration. But does it really do any good? The answer: Sometimes. And: it depends.

Since the late 1980s, millions of trees have been tossed in the bayous, swamps and saltwater marshes of south Louisiana. The hope is that they will serve as a bulwark against waves and storms, and help restore wetlands lost to erosion and the sinking of the land, a process called subsidence.

These and other factors are causing Louisiana to lose an average of a football field of wetlands every 100 minutes, according to the U.S. Geological Survey.

A volunteer throws Christmas trees into Goose Bayou in Lafitte during Jefferson Parish's annual Christmas tree recycling program in 2014. (Times-Picayune | New Orleans Advocate file photo) ▲

No comprehensive studies have tested the effectiveness of Louisiana’s Christmas tree defense, but there’s plenty of circumstantial evidence that it’s doing a lot of good, many people involved in coastal restoration say.

Shelley Stiaes, manager of the Bayou Sauvage National Wildlife Refuge in New Orleans East, is a firm believer in the restorative power of Christmas trees.

“I know they work because I’ve seen the topography of the refuge change over the last 20 years,” she said. “You don’t see as much open water and you have more vegetation growing. That all helps in a storm situation."

At 25,000 acres, Bayou Sauvage is the largest urban refuge in the country, according to the U.S. Fish and Wildlife Service. It soaks up floodwater and can absorb some of the impact from hurricanes headed for New Orleans.

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Each January, between 5,000 and 10,000 trees are airlifted by Louisiana Air National Guard helicopters to select spots in the refuge.

Stiaes said portions of a 6,000-acre lagoon and 1,900-acre marsh have been restored partly thanks to the trees.

But what works in Bayou Sauvage might not work in most places on the Louisiana coast, especially the areas that are unraveling the fastest, said Paul Kemp, an LSU coastal scientist and one of the few people who has studied how well Christmas trees protect Louisiana wetlands.

A Black Hawk helicopter with the Louisiana Army National Guard's 1-244th Assault Battalion airlifts bundles of repurposed Christmas trees to Bayou Sauvage in New Orleans East in March 2019. Advocate staff photo by MAX BECHERER ▲

He and other scientists collected data at two small Christmas tree restoration sites: a wetland on the south shore of Lake Pontchartrain and a wave-damaged marsh near Leeville in Lafourche Parish.

He admits the study, published in 1997, is far from definitive, but it indicated Christmas trees don't work very well unless they're placed in shallow water with few waves and plenty of suspended silt and other sediment. That’s a pretty uncommon combination.

“It’s only effective where there’s a lot of sediment moving around but not much wave action,” Kemp said. “Those places are relatively rare.”

He also found that the trees are most helpful in spots that are already building land, such as river outflows, where sediment-rich freshwater is spilling across tidal areas. Adding some Christmas trees can help quicken the land-forming process there, he said.

The trees do this by combing out sediment flowing through slow-moving water. The sediment settles and eventually piles high enough to support plants. The plants’ roots firm up the soil and new land is born.

The idea of piling Christmas trees in wetlands came from an LSU graduate student named Roelof Boumans. In Boumans’ home country, the Netherlands, the Dutch have long built small barriers with brush and trees to slow wetland erosion. Boumans, Kemp and other LSU scientists tried a few experiments in 1987.

By 1990, the state Department of Natural Resources was funding tree recycling for wetland restoration in 16 of Louisiana's 19 coastal parishes. However, DNR no longer provides funding, leaving it up to parish governments and nonprofit groups to support their own programs.

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Jefferson Parish’s program is particularly robust. Over the past 30 years, with the help of volunteer boaters, the parish has plopped more than 850,000 trees in the marshes of the Barataria Basin.

Even if not all of those trees are effective, at least they’re not clogging up landfills, advocates note. Americans toss out about 15 million Christmas trees each year, according to the National Environmental Education Foundation. Most end up in the dump.

However, other parts of the country also recycle trees. In New York, they’re chopped into mulch for playgrounds and trails. In Wisconsin, they're dropped into lakes to boost fish habitat. Ohio crams them into stream banks to stem erosion. Massachusetts builds beach dunes with them.

U. S. Fish & Wildlife Service staff and other crews stand on piles of Christmas trees that were just dropped off by a Louisiana National Guard helicopter in the Bayou Sauvage area east of New Orleans on Wednesday, March 14, 2018. (Photo by Chris Granger, NOLA.com | The Times-Picayune) Photo by Chris Granger NOLA.com | The Times-Picayune ▲

Putting thousands of Christmas trees in natural places could have a hidden downside, however. Tree farms, where most Christmas trees are grown, rely heavily on pesticide sprays. A few of the more common bug and fungus killers used at tree farms are some of the worst still allowed in the U.S., according to Nathan Donley, an environmental scientist with the Center for Biological Diversity.

That may not be good for the farm workers, soil and waterways of Oregon and North Carolina, the two biggest producers of Christmas trees, but it’s unclear what it means for Louisiana. Donley said there’s no solid science showing how much of the chemicals remain once the trees reach your home and then the wetlands.

Based on most tree farm practices, horticulturist Rick Bates of Penn State University thinks there's probably little to fear.

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“Any fungicides or insecticides a grower would use are applied much earlier in the growing season … and would have biodegraded long before harvest,” he said.

Even if Christmas trees aren't oozing pesticides, are they really doing much good when many trees end up doing little or nothing to halt erosion?

Kemp said even a "feel-good" tree recycling program has value in educating the public.

“It’s one of the few ways the public gets involved in restoration,” he said. “There’s a lot of excitement around it each year, particularly for kids."

Stiaes, the manager of Bayou Sauvage, is convinced it does both: helps to restore her refuge and to involve the public.

“It is a ‘feel-good’ project,” she said. “It feels good to protect the environment and the city of New Orleans."

Tree pickups and drop-offs

New Orleans area waste management companies offered post-holiday tree pickups this past week, with the last pickups in most places having been on Saturday.

St. Bernard Parish still has two drop-off spots: the Paris Road Transfer Station at 5120 Paris Ave. in Chalmette and the E.J. Gore Station at 7715 E. Judge Perez Drive in Violet.

St. Tammany residents can bring trees to the St. Tammany Parish Fairgrounds, 1515 N. Florida St. in Covington, and the Old Levee Board Property, 61134 Military Road in Slidell.