On a dive in December 2017, marine biologist and photographer Octavio Aburto suddenly found himself surrounded by eight Caribbean reef sharks (Carcharhinus perezii). Aburto has spent enough time diving the world’s coral reefs to realize in that moment, with those incredible creatures swirling around him, just how special a place this was.

Gardens of the Queen National Park—or Jardines de la Reina, as it’s known in Spanish—is widely heralded as one of most intact marine ecosystems in the Caribbean. The vast and varied underwater wilderness lies about 100 kilometers (60 miles) offshore from Cuba’s southeastern coast and is filled with elkhorn coral (Acropora palmata) forests, towering reefs, hawksbill turtles (Eretmochelys imbricate), and goliath groupers (Epinephelus itajara) the size of small cars. Aburto, a scientist at UC San Diego’s Scripps Institution of Oceanography, has documented reef and mangrove ecosystems throughout the Americas. “What I saw in Jardines de la Reina,” he says, “it’s impressive.”

The remarkably healthy and diverse crown jewel of the Caribbean, as the archipelago of barrier reefs, keys, and mangroves is sometimes called, has been a rare bright spot in an otherwise brutal spate of bad news about sick and dying coral reefs around the world.

Given the high biodiversity of Cuba’s reefs, there’s also a lot to lose. Cuba’s coastal mangroves, wetlands, and waters host more than half of the Caribbean region’s endemic marine species and provide critical spawning sites for commercially important fish such as mutton snapper (Lutjanus analis). The island nation’s marine environments also serve as migration corridors for sharks, manatees, and other animals traveling between the Gulf of Mexico and the Atlantic Ocean. “Every coral reef species is affected by a healthy coral reef environment, and will replenish species downstream,” says Daria Siciliano, a coral expert at UC Santa Cruz’s Marine Science Institute. Cuba’s extensive reefs, she explains, harbor coral larvae and other inhabitants that may travel with the prevailing ocean currents to help “reseed” depleted populations to the north.

So as global warming, ocean acidification, pollution, overfishing, and a host of other dangers are increasingly threatening corals the world over, Cuba’s reefs stand out. It would be easy to dismiss Gardens of the Queen as a splendid freak of nature—an uncanny ecosystem protected by its distance from the mainland. But researchers have cited the relative good health of many near-shore reefs here as well, especially along Cuba’s southern shore. Among the potential contributing factors that scientists have identified, new research efforts are revealing connections between the country’s farming practices and its flourishing seas.

Some reefs have certainly fared better than others, but recent expeditions around the island’s coastline have found few signs of the large-scale coral bleaching, disease, and destruction that have ravaged reefs from the Florida Keys to Australia’s Great Barrier Reef. Understanding why so many of Cuba’s reefs have thrived while many elsewhere have not could prove pivotal in the fight to preserve the marine wonders here and around the globe.

Rainfall washed these fertilizers into drainage channels that fed streams and rivers on their way to the ocean. This nutrient pollution can trigger the explosive growth of phytoplankton and harmful algae. Among other consequences, algal overgrowth can take over reefs and rob the ocean of oxygen when the algae die and decay, creating dead zones where almost no life can persist. Though few studies focused on the health of Cuba’s reefs prior to 1990, surveys in the 90s and early 2000s documented diseased and declining corals in multiple parts of the country, particularly in and near the polluted waters of Havana Bay.

But when the Soviet bloc fell in the early 90s, it abruptly turned off the spigot for Cuba’s sugar subsidies and regular shipments of food, gasoline, farming equipment, synthetic fertilizers, and pesticides. With the U.S. trade embargo cutting off other supply routes, Cuba’s fishing and sugarcane industries collapsed. Inorganic fertilizer use plunged and agricultural production quickly followed, down more than 50 percent in just five years. In the difficult years that followed, which Cubans euphemistically call “The Special Period,” per-capita calorie intake dropped by more than a third.

Cuban farmers were forced to make do with much less. In necessarily smaller fields, oxen took the place of now-abandoned tractors and organic methods replaced the now-unavailable synthetic fertilizers and pesticides. Between 1999 and 2001, the country’s average use of inorganic fertilizer fell back to about 15 percent of its 1989 peak—with most of that earmarked for sugarcane production.

The lack of capital and chemicals led, by default, to lower-impact agricultural methods at many of Cuba’s state-owned sugarcane plantations and other farms, explains Margarita Fernandez, executive director of the Vermont Caribbean Institute, a non-profit that works to support sustainable agroecology and organic farming principles. University of Vermont conservation biologist Joe Roman also works in Cuba and says, “Basically, what people in Vermont want to do electively, they did by force.”

But the small-scale organic farming model that was initially adopted out of sheer necessity became integral to the local ethos. It has since been championed by farmers, politicians, and scientists, and has won plaudits from agronomists around the world. Despite the continuing debate over food security here, many experts say the shift in Cuban agriculture is working. Among other gains, per-capita calorie levels have almost doubled from their low point in 1993.

In the painful but ultimately fruitful transition to organic farming, Cuba also became a grand experiment for how a shift away from industrial agriculture can impact both terrestrial and marine environments. On the long and narrow island, Roman says, “Every decision you make on land affects the ocean as well.”

A report on the status and trends of Caribbean coral reefs from 1970 to 2012 suggested that threats from both land and sea have wiped out more than half of the region’s corals since 1970. In Cuba, though, the decline in the extent of live corals covering its reefs began to reverse course in the mid-90s. Although data are limited, the apparent recovery roughly coincided with an uptick in the biomass of parrotfish and grouper—two key indicators of reef health; parrotfish, for example, graze on and help prevent the overgrowth of the corals’ algae competitors. Subsequently, the average percentage of each reef covered by algae began to drop.

Given the delicate state of many Caribbean reefs, any conservation failures in Cuba have the potential to send economic ripples throughout the region, says Jorge Angulo-Valdés, head of the Marine Conservation Group at the University of Havana’s Center for Marine Research. The hard part, he concedes, will be determining how best to continue increasing Cuba’s food security while minimizing collateral damage to the environment. “We still need to make a living,” he says. “Our people still need to have food.”

Gardens of the Queen offers one model for a path forward—one that bolsters local economies while fostering a lighter environmental footprint. The popular park provides jobs to scuba, snorkeling, and recreational fishing tour operators; suppliers; and nearby hoteliers. The industry, in turn, pays for regular patrols to prevent illegal commercial fishing. By giving residents an economic stake in the park, “people see the advantages they are getting by protecting nature,” Angulo-Valdés says.

In the meantime, scientists are learning more about the consequences of adding nitrogen to coral ecosystems. Researchers at Stanford University used a similar core-sampling method on four corals off Bali, Indonesia to track nitrogen runoff associated with sewage and the island’s debut of synthetic fertilizers nearly 50 years ago. Their study suggests that the corals had captured historical records of the ocean water quality and that increasing chemical fertilizer use in the island’s rice paddies had contributed to the degradation of some near-shore reefs.

In 2013, Australian scientists used a different method to calculate phosphorus levels in a 60-year core taken from a coral on the Great Barrier Reef. Phosphorus content in the coral skeleton increased eight-fold between 1949 and 2008. The rise coincided with heightened sugarcane production and fertilizer use along a nearby river, suggesting that the core had captured an annual record of the phosphorus runoff.

Siciliano’s sampling location, near several tributaries that discharge into the gulf, should help her team gauge the impact of similar runoff in Cuba, revealing insights about changing nitrogen loads over time. Definitively answering how lower-impact farming methods may have reduced the island’s flow of chemical fertilizer into the marine environment and improved the health of these ecosystems will require more analysis of corals from other strategic locations, she emphasizes. Stronger U.S.-Cuba relations, though, could help address the need for follow-up collaborations on land and at sea—and this has potential to improve the management and restoration of coral reefs throughout the Caribbean, and beyond.

Cuba’s natural laboratories may provide a rare glimpse of how restricting pollution from agricultural runoff can help corals rebound. With the mounting threats buffeting reefs around the world, they’ll need all the help they can get.