Ocean warming poses a major threat to the world’s coal reefs, but with some ocean conservation effort, Caribbean reefs could become far more resilient to this stressor, a new report has found.
The report analyzed thousands of surveys of coral, seaweeds, and grazing fish and sea urchins, and found that the loss of coral grazers such as parrotfish and urchins is one of the most pressing threats facing Caribbean reefs today — so pressing that, if these grazers continue to decline, Caribbean coral reefs could completely disappear in the next 20 years. In fact, the decline of these grazers has driven more degradation of Caribbean coral than ocean warming has over the last 40 years, with 50 percent of Caribbean coral reefs declining since the 1970s.
“Even if we could somehow make climate change disappear tomorrow, these reefs would continue their decline,” Jeremy Jackson, lead author of the report and IUCN’s senior advisor on coral reefs, said in a statement. “We must immediately address the grazing problem for the reefs to stand any chance of surviving future climate shifts.”
Parrotfish are voracious grazers, spending up to 90 percent of their day eating algae off coral. Too much algae can smother coral, so grazing fish and urchins are essential to keep corals alive. Overfishing has contributed to steep declines in Caribbean parrotfish populations over the last several decades, as has pollution and local tourism. And disease led to a mass mortality event of sea urchins in 1983, causing urchin numbers to take a hit.
This decline in grazers makes coral more vulnerable to death by smothering, but according to the study, it also could impact the reefs’ ability to rebound after a hurricane. Researchers found that reefs protected from overfishing in Bermuda exhibited no loss of coral cover after four hurricanes since 1984, but overfished reefs in Belize declined by 49 percent after three hurricanes.
The data is sobering, but it points to clear ocean policies that can help protect the health of Caribbean reefs far more quickly and easily than policies that attempt to alleviate climate change. Reefs where parrotfish aren’t protected, including in Jamaica, the entire Florida Reef Tract from Miami to Key West, and the U.S. Virgin Islands. The study found that some of the healthiest coral reefs were those that have taken action to protect parrotfish, such as banning fish traps and spearfishing, or banning fishing of parrotfish and sea urchins altogether, as the report notes Barbuda is doing.
“This is the kind of aggressive management that needs to be replicated regionally if we are going to increase the resilience of Caribbean reefs,” Ayana Johnson of the Waitt Institute’s Blue Halo Initiative said in a statement.
The study highlights an idea that’s been voiced before in ocean conservation: though climate change is a major threat to ocean health, there are conservation strategies that can be undertaken now that can make a big difference in the survival chances of coral reefs and other ocean ecosystems. A report published earlier this year stressed that reefs that are managed well can recover from events like coral bleaching. It also reiterated the fact that healthy coral reefs are crucial protectors of oceanfront residents, reducing wave energy by 97 percent on average and helping protect coastal properties from storm surge and sea level rise.