Midwinter on the Caribbean island of St. Barts is a kind of second hurricane season. December’s annual landfall of billionaires and celebrities was a Cat 5, with Leonardo DiCaprio, Mike Tyson, the world’s biggest mega-yachts, and Jeff Bezos and his girlfriend canoodling in their bathing suits.

But in the midst of this glitter cyclone, two days before Christmas, a judge hurled the latest volley in a legal battle that has pitted billionaire against billionaire, and human development against fragile nature on this playground for the one percent. The court ruled that a company headed by the American hotelier Denise Dupré must stop construction of her second luxury hotel on the island, and refill a football field-size hole, intended for an underground parking garage, on a popular but environmentally precarious beach.

The ruling might signal a turning point in the hyper-development of this tropical Arcadia for the rich. The deconstruction alone will cost the developer what some parties involved estimate to be at least 50 million euros (about $57 million). The company won’t divulge the actual cost of the proposed project.

For four decades, two cultures have shared the biome of this tropical “little pebble,” as the French royals once called the island. Most of the current island natives are French-speaking descendants of a clan of Normandy peasants and enslaved people who arrived on the agriculturally inhospitable outpost in the 17th century. The original island inhabitants were Arawaks and Caribs.

The islanders’ forebears survived centuries during which power passed back and forth between pirates, England and France — and even 100 years of Swedish rule — before settling into the modern era, first as part of the French overseas department of nearby Guadeloupe, and now as a self-governing collectivité still operating under French law. Until 40 years ago, jobs were so scarce that residents went to other islands — nearby St. Thomas mainly, where a fishing village called Frenchtown was settled in the 19th century by laborers from St. Barts — for work. St. Barts itself wasn’t electrified until the 1980s.

The newer colonists — American and European celebrities and Wall Street tycoons — who, like the other non-indigenous species on the island, have proliferated without predators, are the socioeconomic descendants of the Rockefellers and the Rothschilds. The latter sailed onto this arid, minimally populated speck in the late 1950s, were charmed and built a pair of Xanadus on mountaintops overlooking azure waters.

St. Barts’ official bird? Some say the construction crane

Forty years after the island was electrified, St. Barts is the setting for a theater of conspicuous consumption. In the last five years especially, the background noise on some parts of the island is not birdsong but increasingly the clack-clack of drilling through rock, the grunt of earth-moving machines and the buzz of small prop planes delivering and retrieving tourists and their Vuitton baggage from an airport with a hair-raisingly short runway. (This reporter, from the cafe of a five-star hotel nearby, witnessed one small plane abort a landing in a terrifying maneuver. If any of the swells noticed no one reacted.)

Heavy trucks crack the asphalt of serpentine mountain roads dotted with construction sites, compounding a traffic problem that can, with its mingling of gorgeous weather, idling luxury cars and sour, but fashionable, drivers, be reminiscent of Los Angeles. Every hundred yards or so, another construction permit is glued to a temporary wall.

The pace and scale of development has brought jobs and made millionaires of local landowners, real estate developers and house flippers. It has also brought traffic, water pollution, dead reefs, housing shortages and, some scientists and locals say, pushed the island’s ecosystem to a tipping point, beyond which it cannot return.

The local government officially deems 60 percent of the island to be an unbuildable “green zone.” That zone is famously porous. Stories abound of wealthy or famous people buying green-zoned property and moving the boundary lines. Islanders joke that the real green zone is the American dollar and that St. Barts official bird is the construction crane.

Denise Dupré has a house on the island and has been visiting it for 20 years, but the American philanthropist and businesswoman who has taught at Harvard, is an obscure figure to the locals, and not active in the social scene.

Her hotel development, L’Etoile, is planned as an ultramodern multistory concrete structure, on the footprint of a smaller resort destroyed by Hurricane Irma in 2017, on a crescent of sand along St. Jean Bay. It would be situated beside and compete with a historic older luxury hotel, the Eden Rock (owned by a Brit, David Matthews, who happens to be the father-in-law of the Duchess of York’s sister, Pippa Middleton.)

The developers planned a hotel with 50 rooms, a swimming pool and a beachside underground parking garage. In December 2019, the government granted the permit, against the advice of environmentalists and some of its own elected officials.

Arguments over the construction permit went to court several times before the company broke ground in March 2021. Eden Rock Hotel, co-owned by Mr. Matthews and the German luxury hotel company Oetker Collection, joined the environmentalists in opposing it. The Russian oligarch and island homeowner Roman Abramovich is not a party to the lawsuit, but is deeply involved in the island’s environmental restoration. He built a soccer field for the community and paid to restore a salt pond that environmentalists then accused the L’Etoile developers of polluting with cement runoff. (The company denies this.)

The two sides in the lawsuit faced off against each other in four emergency court hearings in 2020 and 2021. The judge, while asking for modifications pertaining to the project’s building height, allowed construction to begin in March 2021. In July 2021 the judge suspended the company’s modified construction permit pending further legal hearings, but the company continued construction under the original permit.

A group of young people calling themselves Ouanalao’s Guardians (Ouanalao was the Arawak name for the island) had circulated a change.org petition against the project and got 2,200 signatures. Another petition by an island environmental organization, St. Barts Essentiel (SBE), collected signatures of about 2,700 of the 10,000 islanders, demanding the project be scaled back. But the construction work continued throughout 2021, with machines blasting away at the foundation hole.

William von Mueffling, a New York hedge fund manager and a longtime island resident is a supporter of the environmentalists and critical of the developers. The L’Etoile project “clearly did not appeal to the vast majority of people on the island who have enough challenges with housing, traffic and water pollution,” he said. “SBE keeps the island honest. It is unfortunate that a nonprofit has to do the enforcement work of the collectivité, but that is the reality.”

Two days before Christmas 2021, the court definitively canceled all iterations of the project’s construction permit, on the grounds that the foundation hole posed a risk to the safety of employees and guests in the event of a hurricane-related flood.

Ms. Dupré’s group had already developed another hotel that it operates — the austere, five-star Le Barthélemy Hotel & Spa, on a beach called Grand Cul de Sac, which has had its own environmental issues. Le Barthélemy received two notices, in 2019 and 2021, from the government about chemical and biological waste leaking into the water.

Government inspectors have recorded E. coli levels 800 percent higher than the legal limit. “I kite surf at the lagoon almost everyday, and my worst fear is not getting in an accident but falling into the polluted lagoon,” said Patrick Ubbeda, a local restaurant owner.

In one of two formal notices to the hotel signed by the island’s president, Bruno Magras, and obtained by The New York Times, the government accused the company of ignoring a 2019 request to deal with the pollution problem. A Dupré spokesman, Alex Stanton, denied that the company ignored the notices and said the hotel will have a new filtration system this year.

The Dupré companies started the projects as the island was dealing with new concerns about sustainability. A 2016 Wildlife Conservation Society report stated that the island’s environment is “rapidly degrading” because of land-based pollution draining into the sea and destroying marine habitats, urbanization and overfishing. A year later, Hurricane Irma devastated the island, worsening an already dire housing shortage for workers.

That tension may explain some of the animosity toward Ms. Dupré and her husband, Mark Nunnelly (a former managing partner at Bain Capital, former chief executive of Domino’s Pizza and an investor in an outsourcing concern, a call center and other ventures). Someone scrawled “Get Out Dupré Pig” in red on the white construction wall — a highly unusual act of vandalism on the mostly crime-free island. One of the English-language island online forums has a chat titled “Death to Domino’s Pizza” in reference to the hotel project.

“In one corner you have this billionaire business firm and in the other a bunch of local people saying please don’t damage our marine life,” said a Youngstown, Ohio, attorney, Eddie Czopur, who has been staying on St. Jean Bay during the winter season for years. “It was like a ‘Rocky’ story, that the locals won.”

But Ms. Dupré and Mr. Nunnelly are hardly the only superrich who have been accused of making plans that seem to ignore island scale or Caribbean aesthetic. Islanders have watched as tycoons have increasingly competed to see who can anchor the biggest yacht in the harbor, or build the biggest villa.

The local government recently restricted the size of new villas to under 150 square meters (a little over 1,600 square feet). But at least 50 previously issued construction permits are still in the pipeline — meaning new mega mansions will surely be erected. The once- crystalline waters around the island have turned cloudy as construction-runoff sediment damages reefs and drives off sea animals. One marine biologist who works on the island told me she cried after returning to a diving site once teeming with turtles and sharks and finding it barren.

Ms. Dupré and her husband declined to comment for this article, referring questions to Mr. Stanton, a spokesman for Ms. Dupré and her company, SAS St. Jean Beach Real Estate. He said the company will appeal the ruling against the L’Etoile permit to a higher court in France in March, but that adjudication will take at least 15 months. Ms. Dupré still hopes to build a hotel, but will fill in the hole as ordered once the collectivité grants permission, he said.

“She has a deep background in hotel management, and Denise and the family have had a special affection for the island for more than 20 years,” Mr. Stanton said. “She and the St. Barts team she worked with feel they were very attentive to bringing a peaceful, beautiful thing to this beach, and will continue to engage in constructive dialogue with the community about the project.”

Who will protect the island?

This little island conflict begs a bigger question: If arguably some of the world’s wealthiest and most sophisticated people can’t or won’t protect the air, water, coral reefs and sea turtles around their own playground, how can anyone reasonably expect humanity to protect the planet?

President Bruno Magras, whose first job was pumping gas on St. Thomas, has been managing the island for 27 years, since before it became independent of Guadeloupe. A canny, charming and sometimes belligerent character, he presided over a three-decade economic transformation unlike any in the Caribbean. In the 1990s he founded and owned a local airline, St Barth Commuter, until transferring ownership to his children in 2017.

Mr. Magras, known for his pro-business stance, did not try to stop the L’Etoile development.

In February, he announced he was not going to run for a sixth term.

Running to replace him is Hélène Bernier, the face and voice of the SBE. A taxi driver like her father, in her 40s, Ms. Bernier represents a new generation of islanders. She shares twin toddler daughters with her ex-wife, and has positioned herself as protector of the island as Conseillere Territorial — a kind of island member of Parliament — since 2017. “I have the island in my blood, and in that of my two children,” she said.

For her activism, Ms. Bernier said she has faced harassment, a few death threats and bribery attempts. She said that one local landowner offered her a million euros to agree not to challenge a green zone exemption on a possible 20 million euro land sale. “I thought about it, because that is a lot of money,” she said. “But I said no, because I don’t think I could have got up in the morning and looked at myself.”

Ms. Bernier’s passion and breezy charm — her go-to word is the French endearment cou-cou — have not convinced everyone that she has the shrewdness to manage big egos and vast money, and save coral and turtles at the same time. “To curb the appetite of big developers, all you have to do is change the rules on the island,” she said. “All you have to do is draft a code, gather the territorial council and have it voted on!”

For Mr. Magras, it was never that simple. During an interview in his tiny office at the airport, Mr. Magras, the consummate tropical leader, sporting shirt sleeves and a pencil mustache, touted the economic miracle he presided over. He agrees the ecosystem can only take so much development, but he is concerned developers with valid permits could sue if the island government tries to step in. His power is ultimately hampered, he said wryly, by democracy.

“As long as we are in a democracy and people want to sell their land, we cannot prevent them from selling.”

Nina Burleigh is a journalist and author, most recently, of Virus: Vaccinations, the CDC and the Hijacking of America’s Response to the Pandemic.

Follow New York Times Travel on Instagram, Twitter and Facebook. And sign up for our weekly Travel Dispatch newsletter to receive expert tips on traveling smarter and inspiration for your next vacation. Dreaming up a future getaway or just armchair traveling? Check out our 52 Places list for 2022.