With only about one-sixth of the original coral cover left, most Caribbean coral reefs may disappear in the next 20 years, according to a report.
The study indicates that global warming alone isn’t to blame for a precipitous decline in coral area—the main problem is a loss of grazing fish, which eat the algae on the reefs.
“The rate at which the Caribbean corals have been declining is truly alarming,” said Carl Gustaf Lundin, Director of Global Marine and Polar Programme for the International Union for Conservation of Nature, which contributed to the report. But “the fate of Caribbean corals is not beyond our control and there are some very concrete steps that we can take to help them recover.”
“Even if we could somehow make climate change disappear tomorrow, these reefs would continue their decline,” added Jeremy Jackson, lead author of the report and the union’s senior advisor on coral reefs. “We must immediately address the grazing problem for the reefs to stand any chance of surviving future climate shifts.”
Caribbean corals have declined by more than 50 percent since the 1970s, the study found, but restoring parrotfish populations and improving other management strategies, such as protection from overfishing and excessive coastal pollution, could help the reefs recover.
The report is the result of the work of 90 experts over three years. It contains the analysis of more than 35,000 surveys conducted at 90 Caribbean locations since 1970, including studies of corals, seaweeds, grazing sea urchins and fish.
The report, Status and Trends of Caribbean Coral Reefs: 1970-2012, from the Global Coral Reef Monitoring Network, the International Union and the United Nations Environment Programme, was released July 2 in Gland, Switzerland.
Climate change has long been thought to be the main culprit in coral degradation. While it does pose a serious threat by making oceans more acidic and causing coral “bleaching,” the report says that the loss of parrotfish and sea urchin – the area’s two main “grazers” – has been a worse problem.
An unidentified disease led to a mass death of the sea urchin in 1983 and extreme fishing throughout the 20th century has brought the parrotfish population to the brink of extinction in some regions, the report added. The loss of these species breaks the delicate balance of coral ecosystems and allows algae, on which they feed, to smother the reefs.
Reefs protected from overfishing, as well as other threats such as excessive coastal pollution, tourism and coastal development, are more resilient to pressures from climate change, according to the authors.