In Just 25 Years, Half of the Coral in the Great Barrier Reef has Disappeared

Coral bleaching in the Pacific Ocean. Image: THE OCEAN AGENCY / XL CATLIN SEAVIEW SURVEY

by Amy Lupica, ODP Contributing Writer

A new study has found that since 1995, half of all the coral in the Great Barrier Reef has been wiped out due to rising ocean temperatures caused by climate change.

Terry Hughes, a professor at the ARC Center of Excellence for Coral Reef Studies in Queensland and a co-author of the study explained, “The only effective way to improve the outcome for coral reefs is global action on greenhouse gasses. If global temperatures rise to 3 or 4 [degrees Celsius], the reef will be unrecognizable, so there is no time to lose.”

Why This Matters: The Great Barrier Reef is one of the most complex and biodiverse ecosystems in the world. A UNESCO World Heritage site, the reef and its accompanying islands support “1,500 species of fish, about 400 species of coral, 4,000 species of mollusk, and some 240 species of birds, plus a great diversity of sponges, anemones, marine worms, crustaceans, and other species,” many of whom are also threatened by human activity and climate change.

The Great Barrier reef is also critical to the people of Australia, who not only benefit from the tourism industry the reef attracts but also the reef’s role in reducing flooding in coastal cities

The rapid decline of coral in the Great Barrier Reef, which was designated by UNESCO in part because of its resilience, bodes poorly for reefs across the world, which provide habitats for 25% of all marine plants and animals and flood protection for 500 million coastal residents.

Growing Threats: The Great Barrier Reef, and many others, are primarily threatened by “coral bleaching” a process by which changing water temperatures, pollution, low tides, and overexposure to sunlight drives away the algae that live on the surface of the coral and provide it with food. The coral is left brittle, pale, and susceptible to disease


Like many problems caused by climate change, the rapid death of corals is a vicious cycle that experts say will be extremely difficult to reverse. As reefs die, clusters of corals grow farther apart and it becomes harder for them to reproduce, and less likely that the reef will recover

“If I don’t see one-year-old, two-year-old, three-year-old corals, I know that reef is dead. It just doesn’t know it yet,” Said Bob Richmond, a research professor and director of the Kewalo Marine Laboratory at the University of Hawaii at Manoa. 

Is There Hope? Scientists have already begun engineering potential solutions. Sydney Institute of Marine Science and the University of Sydney recently partnered to develop “marine cloud brightening” which could potentially reflect sunlight away from the reef, preventing further coral bleaching. 

Other experts, like Gabby Ahmadia, director of ocean science at the World Wildlife Fund, are hopeful for the future of coral reefs worldwide. In Indonesia, she said, some coral is developing resistance to warmer temperatures and ocean acidification, but Ahmadia knows that’s not enough. “The reality of the situation is that coral reefs are declining around the world, but the hope is we can have better local solutions to overfishing, runoffs from land and farming practices,” she said, “They are going to decline, no doubt, but we can conserve what’s left.”

Although reluctant to put a time of death on the world’s coral reefs, experts fear that if solutions aren’t implemented soon, there will be nothing to conserve at all. Ahmadia says she feels the pressure, “a lot of people say 90 percent of the coral loss will happen by 2050.” Richmond agrees, “if we don’t act meaningfully in the next five years, we will not have vital and vibrant coral reefs as a legacy for future generations.”

Graphic: Annabel Driussi for Our Daily Planet

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