Blaming Caribbean coral reef destruction on global warming is leaving them vulnerable to overfishing, tourism, and the Panama Canal.
Coral cover has more than halved since the 1970s and the reefs could be entirely dead within 20 years, warned the report, Status and Trends of Caribbean Coral Reefs: 1970-2012.
Although global warming is expected to add to the problems faced by corals in the future, particularly by raising acidity in the oceans, making it harder for them to build their exoskeletons, more immediate threats are doing greater damage.
“The threats of climate change and ocean acidification loom increasingly ominously for the future, but local stressors including an explosion in tourism, overfishing, and the resulting increase in macroalgae [seaweed] have been the major drivers of the catastrophic decline of Caribbean corals,” says the report, edited by Jeremy Jackson, Mary Donovan, Katie Cramer and Vivian Lam.
A sea fan coral from the Caribbean Sea. (Credit NOOA)
Gustaf Lundin, the director of the global marine programme at the International Union for Conservation of Nature – which commissioned the review of 35,000 studies by 90 experts – told The Times that that climate change had become a “convenient truth”, a reference to former US vice president Al Gore’s Academy Award-winning documentary, An Inconvenient Truth.
“Some countries have said: ‘There is nothing we can do. If there isn’t global action on climate change, it’s all doomed’,” he said. “They have basically thrown in the towel. That’s a great mistake. There are always things you can do locally that enhance the resilience of the reefs and their ability to recover.”
The report says the consequences of global warming “pale in comparison to the introduction of the unidentified pathogen that caused the die-off of Diadema antillarum”.
D antillarum, a sea urchin, grazes on large seaweeds, preventing them from smothering the coral. A mysterious disease first noticed near the Caribbean end of the Panama Canal all but wiped it out in 1983-84.
Because the Caribbean has been isolated for millions of years, its species are particularly vulnerable to new diseases introduced from the Pacific through the canal. The report compared them to “Native Americans after their first contact with Europeans”.
The other creature that controls seaweed growth is the parrotfish, Scarus frenatus, which has been over-fished in recent decades. “The consequences have been catastrophic for coral reefs,” says the report. “Overfishing caused steep reductions in herbivores, especially large parrotfishes, which are the most effective grazers on Caribbean reefs.”
The other big threat to corals comes from humans, both residents and tourists. In some cases human populations along the coast can reach as high as 25,000 per km2. The researchers found an inverse relationship between the number of people and the amount of live coral.
The exceptions were Grand Cayman and Bermuda. “The exceptional situation at Bermuda most likely reflects progressive environmental regulations in place since the 1990s and the infrastructure required to make them work.
“Otherwise, the harmful environmental costs of runaway tourism seem to be inevitable.”
