Caribbean Coral Reefs Mostly Dead, IUCN Says

By Christine Dell'Amore (National Geographic)

The Caribbean’s coral reefs have collapsed, mostly due to overfishing and climate change, according to a new report released by the International Union for Conservation of Nature (IUCN).

In the most comprehensive study yet of Caribbean coral reefs, scientists have discovered that the 50 to 60 percent coral cover present in the 1970s has plummeted to less than 10 percent.

“I’m sad to tell you it’s a dire picture,” Carl Gustaf Lundin, director of IUCN’s Global Marine and Polar Program, said at a news briefing Friday at the World Conservation Congress in Jeju Island, South Korea.

Called “Nature’s Olympics,” the conference will explore five environmental themes over five days. Today’s theme is Nature+ Climate, which focuses on how to combat global warming.

Much of the decline is caused by a massive die-off of sea urchins in the 1970s—possibly due to disease. Without these reef grazers—the “cows in the field” that keep vegetation in check—the number of algae and grasses have skyrocketed, dominating reefs and pushing corals aside, Lundin said.

What’s more, overfishing of grazer species such as parrotfish or surgeonfish is allowing more algae to take over and outcompete the coral, said Ameer Abdulla, IUCN senior advisor on Marine Biodiversity and Conservation Science.

“Coral reef communities are just like human communities—there are different roles that are fundamental to keeping the system going,” Abdulla said.

For example, if all the engineers were taken out of a human society, that would affect how the society functions. The same phenomenon is happening with the loss of the Caribbean’s grazers, he said.

Scientists also said that warmer water—often caused by hurricanes blowing through—have harmed reefs. When the water gets too hot, algae that live inside coral, called zooxanthellae—abandon their hosts, causing the coral themselves to bleach and eventually die.

Though some reefs can bounce back from such periods of warmer water, notably in the Indian Ocean, “We have heating happening with much higher frequency and for longer duration,” Lundin told National Geographic News.

For instance, some 500-to-a-thousand-year-old corals in the Indian Ocean have died due to warmer water. Corals are vital for many reasons, from boosting tourism dollars to local communities and even buffeting islands themselves from powerful storm surges, Lundin said. The good news is that there are ways to protect the remaining 10 percent of Caribbean corals.

For instance, putting in place marine protected areas can reduce the pressure of overfishing. Governments can also work with local fishers to maintain their livelihoods, for instance by raising the value of individual fish so that the fishers catch fewer animals.

The bottom line, Abdulla said, is that “the Caribbean system is one of first systems to experience collapse—it’s something that will happen across the globe if human use of coral reefs continues as it is.”