All over the world, coral reefs are dying at an alarming rate. But off Cuba, they are flourishing.

Why?

The answer, according to David Guggenheim, a marine scientist and president of Ocean Doctor, a Washington-based conservation organization, is pretty straightforward: The absence of typical human behavior.

“After the Soviets pulled out [in 1991], Cuba couldn't afford fertilizers and pesticides, so they were essentially forced into organic farming — and that's had a beneficial effect on corals,” Guggenheim explains.

The result has been far less nutrient pollution in the ocean waters surrounding Cuba. Nutrients in the water do the same thing in the ocean that they do on land: They fuel the growth of plants and algae — and in the ocean those algae overgrow and ultimately kill coral reefs.

The other reason Cuba's coral reefs are so healthy is that they have fantastic environmental laws in place, Guggenheim says. Twenty-five percent of their waters are marine protected areas, compared to the worldwide average of about 1 percent. “They are very good stewards of their environment, and I have faith in them to continue that,” he adds.

Coral Reefs in the Caribbean have been hit particularly hard. Since 1970, about half of the coral cover in the region has disappeared, including almost 95 percent of the spectacular elkhorn coral. Rising ocean temperatures and pollution cause bleaching in coral, which is usually a death sentence. But even in areas around Cuba where researchers see bleaching, the coral tends to recover — a sign of how healthy the ecosystem is.

The crown jewel of the waters is Gardens of the Queen, on the south coast of Cuba, about 50 miles offshore. “Over the years I have had to endure, like many of us, the disappearance of corals,” Guggenheim says. “When I went back to Gardens of the Queen, it looked better than I remembered as a teenager in the early 70s. It looked incredibly pristine.”

Gardens of the Queen is part of a barrier reef system that extends for 30 miles. Seeing this beautiful, healthy ecosystem gave Guggenheim hope for the first time in recent years about the future of coral reefs. “If we can learn from this living laboratory how a healthy coral reef is supposed to look and function, then those are very valuable insights we can use for restoration efforts around the Caribbean,” he says.

The thawing of relations between Cuba and the United States may help scientists preserve and continue research on the corals. Cuba is still on the State Department 's list of of terrorist nations, which has made collaboration between Cuba’s under-funded researchers and their partners in the US very difficult.

“The Cuban scientists are fantastic,” Guggenheim says. “They’re very well educated and dedicated, but they've got very few resources. The University of Havana Center for Marine Research, our primary partner, has two vessels. One has been at the bottom of a river for more than 15 years…So a lot of what we've done is bring in equipment, try to charter boats and other things to let the Cubans do what they do so well, which is great science.”

But Guggenheim sees a potential downside to increased US involvement. “We've all seen the track record of the United States: we tend to mess things up that we love, and there are a lot of different interests now with their eyes on Cuba,” he says. “So one of our projects is working with the Cubans on developing good decision tools for the future — and that includes environmental economics; helping the Cubans put a price on their natural ecosystems and to look at alternatives, like sustainable eco-tourism.”

So far, the local population has been as keen an anyone to ensure this happens. “In the case of Gardens of the Queen,” Guggenheim says, “most of the former fishermen are now employees of the park — working out there guiding catch-and-release fishing, scuba diving trips, and making maybe ten times what they used to make.”

The biggest challenge may be making sure that these protected areas remain protected. Gardens of the Queen is an increasingly rare success story for corals, Guggenheim says, and it would be in everyone’s interest to keep it that way.

This story is based on an interview that aired on PRI's Science Friday with Ira Flatow.