In what may be his highest-impact leading role yet, the actor Leonardo DiCaprio, the Oscar-nominated “Wolf of Wall Street,” is planning to heal an island.

A well-known environmental activist, Mr. DiCaprio bought Blackadore Caye, 104 acres of wild, unpopulated land off the coast of Belize, with a partner soon after he set foot in the country a decade ago. “It was like heaven on earth,” he said, speaking by telephone from Los Angeles. “And almost immediately, I found this opportunity to purchase an island there.”

Now Mr. DiCaprio has joined with Paul Scialla, the chief executive of Delos, a New York City-based developer, to create an eco-conscious resort there. When it opens to guests in 2018, “Blackadore Caye, a Restorative Island” will feature the trappings of many luxury resorts, with sprawling villas, infinity pools and stunning sunset views.

But the “Restorative” in the title refers not just to the impact the island might have on visitors, but to the island itself. Blackadore Caye has suffered from overfishing, an eroding coastline and the deforestation of its mangrove trees, and the partners mean to put it back to rights.

Blackadore Caye is a 45-minute boat ride from Philip S. W. Goldson International Airport in Belize City and a 15-minute boat ride from San Pedro, the nearest big town. The island has been used for hundreds of years, according to Juan Rovalo, a biologist who leads a team of scientists studying the caye.

It was a popular spot for fishermen, who would stop on their way to markets in Mexicoand cut mangrove, using the wood for fires to smoke their catch and the conch that they took from the reef, littering the island with thousands of empty shells. More recently, he said, the island’s once plentiful palm trees have been uprooted and used to landscape the grounds of hotels in San Pedro.

The villas for guests on Blackadore Caye will be built atop a massive platform that stretches in an arc over the water, with artificial reefs and fish shelters underneath. A nursery on the island will grow indigenous marine grass to support a manatee conservation area, and mangrove trees will be replanted, replacing invasive species. A team of designers, scientists, engineers and landscape architects, some of whom have spent more than 18 months studying Blackadore Caye, will monitor the resort’s impact on its surroundings.

“The main focus is to do something that will change the world,” Mr. DiCaprio said. “I couldn’t have gone to Belize and built on an island and done something like this, if it weren’t for the idea that it could be groundbreaking in the environmental movement.”

An avid scuba diver, Mr. DiCaprio first visited Belize in 2005 to swim its barrier reef. “As soon as I got there, I fell in love,” Mr. DiCaprio said. “Belize is truly unique. It has the second largest coral reef system in the world, and it has some of the most biodiverse marine life, like the manatee population and almost every species of fish you can imagine. Then there are the Mayan temples and the culture.”

He soon purchased Blackadore Caye for $1.75 million with Jeff Gram, the owner of Cayo Espanto Island Resort, a luxury vacation spot on another private island in Belize, where prices in April for two guests ranged from about $1,695 to $2,295 a night, according to its website. Mr. Gram said he would bring his experience in owning and operating island resorts to the new venture. “As for Blackadore,” he said, “I believe that it will be an incredible private island that will set the mark for all future island developments.”

Mr. DiCaprio said it had taken him 10 years to find the right development partner; a deal with Four Seasons Hotels fell through. “My goal was always the fact that I wanted to create something not just environmental, but restorative,” he said. “A showcase for what is possible.”

Restorative Islands L.L.C., which is owned by Mr. Scialla, will build the resort at Blackadore Caye, and Restorative Hospitality, a division of Delos, will be its operator.

Founded by Mr. Scialla when he was a partner at Goldman Sachs, Delos is best known for its health-centric development at 66 East 11th Street. The five-unit condominium, where a penthouse is on the market for $39.8 million, has several features designed to encourage good health, including vitamin C-infused showers, kitchens outfitted with juicing stations and lighting designed to promote sound sleep.

Mr. DiCaprio serves on the Delos advisory board, along with Deepak Chopra, the self-improvement guru; Richard A. Gephardt, the former United States representative from Missouri; and doctors at the Mayo Clinic and the Cleveland Clinic.

“The idea at Blackadore Caye is to push the envelope for what sustainability means — moving the idea beyond environmental awareness into restoration,” Mr. Scialla said. “We don’t want to just do less harm or even have zero impact, but to actually help heal the island, to make it better than before.”

Mr. DiCaprio, who sits on the boards of several nonprofits, including the World Wildlife Fund, was an early investor in Delos. He also owns an apartment at 66 East 11th Street, which he rents out.

“We are pushing each other the whole way to test the boundaries of what is possible,” said Mr. DiCaprio of his partnership with Mr. Scialla and the lead architect and designer, Jason F. McLennan. “With the onset of climate change, there are huge challenges, so we want the structure to not only enhance and improve the environment, but to be a model for the future. That includes restoring the island, creating conservation areas where we can hold research conferences, and regenerating the entire ecosystem to bring it back to its original form and beyond.”

The ecotourism market is large and growing, with eight billion ecotourist visits a year worldwide, according to the Center for Responsible Travel. Ecotourism is travel that minimizes negative impact on a location and seeks to preserve its natural resources.

blackadore-caye-rendering A rendering of the resort. Credit McLennan Design 

Belize, which is slightly smaller than Massachusetts and has just 341,000 people, according to the World Factbook, a website and publication of the Central Intelligence Agency, is highly dependent on eco-tourism. Coral reef and mangrove-associated tourism contributed as much as $196 million to its national economy, or roughly 15 percent of its gross domestic product in 2007, according to a study by the World Resources Institute.

Yet Belize has not enjoyed the same environmental protections as, say, Costa Rica, which was one of the first countries to capitalize on ecotourism.

“I think Belize, in the past, it hasn’t been as stringent and we have seen an adverse impact, especially near the coast,” said Nadia Bood, who is the head of the World Wildlife Fund’s Belize office. Belize is hoping to reverse this trend and in 2013, developed a strict zoning plan for its coastline that is under review and, according to Ms. Bood, should pass into law later this year.

But while ecotourism is a hot topic, it is unclear if it actually works.

“No hotel can be truly sustainable because you have to fly to get there,” said Jan H. Katz, a senior lecturer at the Cornell School of Hotel Administration. “If you really care about sustainability, instead of enlarging your carbon footprint by flying to a remote island and then creating the garbage that they need to compost, just give money to a conservation program.” What people are buying, Ms. Katz said, is the status of staying at an exclusive eco-resort.

Mr. DiCaprio and Mr. Scialla look at it another way. Visits to Blackadore Caye, they say, will help reverse some of the environmental damage the island has already suffered. While Blackadore Caye is not occupied — the scientists studying there must camp and pack in their own food — it has been affected by human activity.

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