There has been a massive collapse of coral reefs throughout the Caribbean, according to a joint project by researchers from Simon Fraser University and the University of East Anglia in Norwich, England.
The study has found that not only are reefs dying faster and on a wider scale than previously thought, but they are quickly crumbling after they die, in a process scientists call “reef flattening.”
The scale of the collapse is massive.
“Probably the most stark finding of our result is that this isn't just a flattening in one patch, one area the size of Vancouver, or even an area the size of British Columbia… the whole Caribbean has been flattened in the past decade, mainly as a result of climate change,” said Nicholas Dulvy of SFU's department of biological sciences. “There are no detectable complex reefs [left].”
The team of international researchers looked at nearly 40 years of data compiled in 500 surveys of 200 reefs, for the first time piecing together the big picture of what has been happening throughout the Caribbean, which is famous for its thousands of beautiful reefs, including one second in size only to Australia's Great Barrier Reef.
Dr. Dulvy said wherever they looked they saw signs of rapid and devastating decline. Reefs are dying and then collapsing on themselves, filling in the nooks and crannies that provide shelter for a myriad of species.
“We've lost 80 per cent of the living coral cover in the Caribbean over the last four decades. So that's a rate of loss that's far greater than the loss of deforestation of the Amazon rain forest. In fact, we're losing coral twice as fast as we're chopping down the Amazon rain forest,” Dr. Dulvy said.
“If we take a forest analogy, we knew that the leaves were dying on the trees of the forest. What we've shown today is that pretty much as soon as the leaves die the trees fall over and you are left with this bare, flat seascape which provides very little shelter for juvenile fish or fish populations.”
Dr. Dulvy said it was known that many individual reefs were dying from disease outbreaks, the impact of hurricanes and because of climate change, which heats shallows so much that reefs become bleached by sunlight.
But it was thought the process was spotty and slow enough that reefs had a chance to regenerate before the tall branches of “stag horns” that protrude up to two metres from the reef bed collapsed.
“We thought it would take five to 10 years for it to collapse, which gave us to some degree a message of hope because if the corals can recover and recoat the skeleton, then reef growing can begin again,” he said. “What this study is showing is that reefs are collapsing pretty much as the coral is dying.”
He said the “stag horns” crumble onto the reef bed, then are broken up through wave action, filling in all the “Swiss cheese” spaces where fish and other small creatures live.
In addition to losing biological diversity, he said the process is robbing the Caribbean of thousands of natural sea breaks, which could have devastating results when rising sea levels and increasingly violent hurricanes combine.
Dr. Dulvy said reef flattening is so widespread in the Caribbean it is probably a phenomenon happening globally.
The researchers were Lorenzo Alvarez-Filip, Jennifer Gill and Andrew Watkinson, all from the University of East Anglia; Isabelle Côté and Dr. Dulvy, from SFU.
Flattening of Caribbean coral reefs: region-wide declines in architectural complexity has been published online by the peer-reviewed journal Proceedings of the Royal Society of London-B .
