Most of tropical reefs are no longer able to both sustain coral reef ecosystems and the livelihoods of the people who depend on them, as human pressure and the impacts of climate change increase.

That was the finding of a new study that looked at 1,800 coral reef sites spread throughout the Indian, Pacific and Atlantic ocean basins.

Only 5% of those sites have plentiful fish stocks, high fish biodiversity and grazing, and well-preserved ecosystem functions — which are key marine ecological metrics.

The study authors say location and the expected targets set by authorities implementing reef conservation are key to helping other sites achieve these multiple goals.

Most of the tropical reef sites around the world are no longer able to simultaneously sustain coral reef ecosystems and the livelihoods of the people who depend on them, as human pressure and impacts of climate change increase, a new study shows.

Only 5% of 1,800 tropical reef sites across 41 countries, states and territories on Earth had plentiful fish stocks, high fish biodiversity and grazing, and well-preserved ecosystem functions — which are key marine ecological metrics, according to the authors of the paper published April 17 in Science magazine.

These sites were geographically spread through the Indian, Pacific and Atlantic ocean basins, the study said.

“These are like the Hollywood A-listers of coral reefs,” said lead author Josh Cinner, from James Cook University in Australia. “They have it all, but they’re also rare and live in exclusive areas — remote locations with little human pressure.”

The remaining reef sites would either serve these same environmental services to a much lesser degree, or lack one of the three ecological metrics, the researchers say.

“In 30 percent of the cases, the value for parrotfish grazing was zero,” Cinner said. Reef scraping by parrotfish helps to keep algae at bay and provides habitat for baby corals to settle on.

Coral reefs worldwide are facing intense degradation due to numerous anthropogenic pressures, such as overfishing, pollution and climate change. “There is an increasing need to manage coral reefs to meet multiple goals simultaneously,” said study co-author Jessica Zamborain-Mason, a Ph.D. candidate at James Cook University.

The researchers developed a series of models to quantify how the three ecological metrics were related to key socioeconomic drivers of resource exploitation while controlling for environmental conditions and sampling techniques.

“Based on our results, only protected reefs that have low human pressure are likely to meet the most conservative target for all three goals simultaneously,” Zamborain-Mason said. “However, we show that, if one aims to achieve lower targets, management measures in locations with intermediate human pressure are likely to produce the greatest benefits.”

She said the implication was also relevant to how future socioeconomic changes, such as infrastructure development and population growth, might affect the efficacy of reef conservation.

The paper found that, while international action on climate change was crucial for ensuring a future for coral-dominated reefs, effective management was also critical to sustaining reefs and the millions of people whose livelihoods depend on them.

Ten percent of the world’s population depends on fisheries for their livelihoods — with most of them being relatively poor — and 4.3 billion people are reliant on fish for 15% of their animal protein intake, according to the Food and Agriculture Organization of the United Nations (FAO).

Cinner said that location and the expected targets set by authorities implementing reef conservation would be key to helping other sites get on the A-list.

“Local management efforts such as no fishing marine reserves can help coral reefs sustain multiple goals, but only if they are placed in the right location, which varies depending on your target,” Cinner said.

“For the existing A-listers, it is clear that high human pressure is likely to seriously degrade reefs, so coastal development initiatives need to be done as sustainably as possible, and maybe in some cases, not at all,” he said.

Citation:

Cinner, J. E., Zamborain-Mason, J., Gurney, G. G., Graham, N. A. J., MacNeil, M. A., Hoey, A. S., … Mouillot, D. (2020). Meeting fisheries, ecosystem function, and biodiversity goals in a human-dominated world. Science, 368(6488), 307-311. doi:10.1126/science.aax9412

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