Why Some Coral Reefs Are Thriving

Not all of the world’s reefs are in bad shape—and a few of the healthiest are managed by humans.

Tane Sinclair-Taylor

In 1990, Jerry Sternin from the global charity Save the Children traveled to Vietnam to fight malnutrition. His strategy was simple. He looked for ‘bright spots’—mothers whose children were bigger and healthier than average, even though they were just as poor and disadvantaged as their neighbors. And he asked: what were they doing differently?

Sternin found that these mothers, rather than feeding their children twice a day, divided the same amount of food into four smaller portions. They also supplemented that food with ingredients that were traditionally ignored, like shrimp, crabs, and sweet potato greens. When Sternin encouraged an entire village to do the same, he cut childhood malnutrition by 65 percent. His program would eventually expand to 2.2 million Vietnamese people across 265 villages.

When Joshua Cinner first heard this story in 2012, he immediately thought of applying the same approach to coral reefs. The planet’s reefs, home to a quarter of its marine species, are in bad shape. Beset by rising temperatures, acidifying waters, hurricanes, disease, and more, their growth rates have plummeted by 40 percent since the 1970s, and lush underwater wonderlands have turned into spectral bleached barrens. Just this year, the iconic Great Barrier Reef has witnessed the worst bleaching event in recorded history.

Amid the gloom and tears, Cinner and his colleagues went searching for bright spots. Mimicking Sternin, they looked for reefs that house more fish than expected, relative to other reefs facing comparable pressures. And their surprising results are upending traditional assumptions about what makes a healthy reef.

Contrary to what you might think, the bright spots weren’t all remote reefs, where humans were absent or fishing was banned. Instead, most were home to lots of people, who rely heavily on the corals and who frequently fished. They weren’t leaving the corals and fish alone; instead, they had developed social norms and institutions that allowed them to manage the reefs responsibly.

“Reefs are hugely threatened. I saw my own field site melt down and completely die,” says Julia Baum from the University of Victoria. “The danger is that we lose hope, or we feel like there’s nothing to be done. That’s why this study is so important. It shows that the end state of people relying on and using coral reefs doesn’t have to be reef degradation.”

“It’s really nice when you can shine a powerful analytical light on what’s going well,” says Nancy Knowlton, a self-described ocean optimist based at the Smithsonian Institution. “We want to start talking about things that are going well in conservation.”

Cinner, a social scientist by training, began by asking his marine biologist colleagues for their data. “I asked 30 reef scientists to give me their life’s work, and if you’ve ever met a scientist, you know that can be like pulling teeth,” he says. “But my dad’s a dentist, so I’m okay with that.”

He ended up with data on 2,514 reefs from 46 nations. His team then created a mathematical model that predicts how many fish a site should have given 18 factors, including water depth, population size and growth, tourism, fishing, whether the reefs were protected, and more. Finally, they identified 15 bright spots and 35 dark spots, which departed substantially from those predictions. These were not the reefs in best or worst condition, but the ones that most defy expectations.

The results were surprising. “The Great Barrier Reef is widely heralded as the most wisely managed coral reef in the world, but it performed exactly as well as we expected it too,” says Sinner. “The Caribbean is widely considered the basket case of the world’s coral reefs, and had a few dark spots but performed largely as we expected.”

Some remote sites like parts of the north-west Hawaiian islands, which have long been textbook examples of how pristine reefs can be when fishing is rare, emerged as dark spots. Meanwhile, most of the 15 bright spots were in fished and populated areas, and near both rich and poor countries.

“Conservationists typically look for the highest absolute biomass and the places that are most untouched. These are the gems, so let’s stop people from going there,” says Cinner. “We looked for places that had more fish than they should, given the condition. Some had biomass below the global mean, so they weren’t pristine, but they were doing better than they should be.”

To work out why the bright spots and dark spots were defying the odds, Cinner’s team surveyed reef scientists and other experts who knew the places well. They found that dark spots were more likely to have had a recent history of environmental shocks like cyclones or bleaching events. Local people were also more likely to use technologies that allow people to fish more intensively, like freezers and destructive nets.

By contrast, people in the bright spots were dependent on the reefs, were engaged in managing them, and did so via taboos and institutions. Consider Karkar Island at Papua New Guinea. The local people practice marine tenure—a system of oceanic property rights, where villages can exclude their neighbors from accessing their particular plot of sea. They also rotate their harvests, closing off patches of reefs for months or years. (They do so to give the fish time to lose their fear of humans; coincidentally, the practice also allows fish to recover.)

The preliminary analyses suggest that policy-makers might serve reefs best by helping people live with them sustainably, whether by instilling systems like property rights or getting people more invested in their local reefs. “There’s been a narrative about local involvement but it’s often very token,” says Cinner. “Our research says that’s not enough. Locals need more than just buying into something that an NGO wants to do. I think there are opportunities for conservation organizations to invest in things that allow for communities to creatively confront their own challenges.”

Such efforts stand in stark contrast to the predominant tactic for saving the seas: establishing large marine protected areas, where fishing and other human activities are restricted. “A lot of countries are going about that by marking out large areas of ocean in areas with no people,” says Baum. “It’s politically easy, as opposed to having to do a lot of really complex marine spatial planning.”

Cinner compares this approach to walking into a flood apartment and trying to put the pretty and expensive things higher, so they don’t get wet. “But we can’t just put an extra floor on the planet,” he says. “So we need to do two things.” One: waterproof as much as you can. Two: plug the leak, which means reducing carbon emissions. If the world continues to warm, “the outlook for reefs and the millions of people who depend on them is very grim,” says Cinner. “We’re never going to climate-proof reefs by protecting fish, but this can facilitate recovery.”

And we can do that not by protecting places that needed little protection, but by learning from areas that faced down their problems and won. We don’t get to live in an ideal world. We have to live in this one, and this one is full of people.

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