Here's how New Orleans is working to prevent coastline erosion

Brendan Causgrove's first encounter with an oyster did not go well. He choked on the plump specimen at the bottom of a hard-alcohol shot after knocking it back.

Now the manager of a smart New Orleans restaurant whose menu features 13 kinds of oysters, the 37-year-old describes them as if they were fine wine - "herbaceous", "buttery" or "briny".

His fervor also means Seaworthy is among 19 restaurants in this coastal U.S. city that have joined an oyster-shell recycling program aiming to help save the state's shrinking shoreline.

The nerve center of the push to turn good food into a good deed for the environment is a fourth-floor office suite in Mid-City, a 10-minute drive from New Orleans' French Quarter, known to some as the oyster capital of the world.

Since 2014, Deborah Abibou and her small team at the non-profit Coalition to Restore Coastal Louisiana have recycled 7.8 million pounds (3.5 million kg) of oyster shells, which they have returned to the water in the form of manmade reefs.

The aim is to stop Louisiana's shoreline crumbling away at the current rate of a football field every 100 minutes.

Early each weekday morning, a recycling truck zig zags through the city to pick up the mollusk shells from restaurants.

The shells are then left to dry in the sun for six months, to kill off any bacteria, before being put into cages that are planted on bare seafloors or riverbeds to form protective walls.

The brand new reefs offer an inviting home for oysters.

But to humans, the "living shorelines", which grow as they attract oyster larvae, serve as robust buffers that dissipate wave energy, prevent coastal erosion, and trap sediment that can build up new land, said Abibou.

Those benefits are boosting the popularity of manmade oyster reefs as a natural alternative to hard infrastructure like seawalls, which are often made with cement, said Alex Kolker, a professor at Louisiana Universities Marine Consortium.

There is no national database tracking the total mileage of oyster-shell coastal protection projects, experts say.

But Bryan DeAngelis, a program coordinator at The Nature Conservancy (TNC), said there are signs the technique is entering the mainstream.

Just in Louisiana, 6 miles (10 km) of protective oyster reefs have been set up with TNC's help, he said.

In New York City, nearly three-quarters of a mile of breakwaters seeded with oysters are in the works off the coast.

And last year, the U.S. Army Corps of Engineers created a nationwide permit that allows "living shorelines", encompassing oyster reefs.

Sacred Site

The dangers of failing to arm the coast against creeping waters are especially real for communities whose lives are tied to the disappearing land.

Authorities fear Louisiana, which has already lost more than 1,800 square miles (4,700 square km) of land since the 1930s, will cede another 2,250 square miles over the next half century.

Declaring a coastal "state of emergency" last year, the state's governor said natural and human factors had contributed to the problem, including the effects of climate change, sea-level rise, subsidence, hurricanes, storm surges and flooding.

In Pointe-aux-Chenes, a village on the frontier of solid land and marshland, where locally caught crabs, oysters and fish have fed a small native American community, the water has turned from friend to foe since eating away at a sacred site.

Ancestors of the Pointe-au-Chien Indian Tribe settled here "before America", said member Donald Dardar.

In the wetlands outside town, a 10-foot (3-m) mound stands shrouded in dense vegetation, said to be a burial or ceremonial ground, according to the 63-year-old with leathery skin and piercing green eyes.

"So we respect it, stay off of it," he said.

But the mound, where dusty pieces of broken pottery have been found, is now at risk of being washed away from one side, flanked by a canal or bayou.

Dug decades ago for transportation, the channel has widened over the years, gobbling about a quarter of the site in 10 years, said Dardar.

Two years ago, the shrimp fisherman decided to act.

"It's just part of history that I don't want to see washed away," he said.

He looked into building a wall to protect the mound and secured a government grant of nearly $70,000 for an oyster reef.

If all goes well, tribe members will hoist 8,400 bags of oyster shells, each weighing some 35 pounds, into their boats next February. Volunteers will then help plunge them into the bayou's muddy waters to form a half-a-mile barrier.

Red Tape

But not all is plain sailing. At a recent meeting, tribe members expressed frustration at red tape holding things back.

"It still bothers me big time right now because it's taking so long to get this going and protect (the site)," said Dardar.

An environmental assessment took a year to complete and some permits have still to come through, said the CRCL's Abibou.

Getting the necessary approvals to install oyster reefs has slowed down projects across the United States, said Pete Malinowski, head of the Billion Oyster Project, a non-profit that restores reefs in New York.

Rules vary by state, but initiatives often hit bureaucratic barriers because oyster reefs are regulated as a food product rather than in their new role as an ecological tool.

"That doesn't make sense because that's not why they're there: no one's eating them," Malinowski said.

"We often find ourselves with the funding, the technical expertise, the community support at a much grander scale than we're able to get permission for."

Today's changing mindset around oysters has been in the making for decades, said Matthew Booker, a professor at North Carolina State University who has written on the theme.

Recognition of their value independent of food can be traced to the 1950s, when shells started to be used in the United States as paving material and railroad ballast, as well as to make cement, he said.

"By the late 20th century some scientists realized, 'These things are buffering storms'," said Booker.

At the University of North Carolina at Chapel Hill, Antonio Rodriguez, a marine geologist, said his interest was sparked by visiting oyster reefs his predecessors had planted near campus.

Seven years on, the academic - one of the first to promote protective oyster reefs through his research - warned the measure was buying time, but as sea levels rise with climate change, more drastic action may be needed.

"What people really need to be thinking about is maybe moving away from the shoreline a little bit," he said.