Destruction of the world’s coral reefs began long before the pollution and global warming of modern times, but it can still be traced back to man.
An extensive investigation of the histories of corals in 14 regions of the world from 40,000 years ago has revealed that the decline started when humans began hunting and fishing in the sea.
Although the dramatic loss of some corals and "bleaching" observed on many reefs has been worsened by global warming and pollution, their demise began many hundreds or even thousand of years ago.
A team of marine biologists from Australia and America have compiled an extensive historical record of coral health from the Atlantic Ocean, the Caribbean, the Red Sea and Australia’s Great Barrier Reef. They found that the "trajectories" of a coral’s decline closely followed one another despite being in different parts of the world.
Yet for each reef, the start of the coral destruction could be matched with the arrival of early humans in that region, said Karen Bjorndal, professor of zoology at the University of Florida in Gainesville and an author of the study published in Science.
"What really struck us was the universality of the decline trajectories. It didn’t matter if we were looking at the Red Sea, Australia or the Caribbean. As soon as human exploitation began, whether in the 1600s in Bermuda or tens of thousands of years ago in the Red Sea, the same scenarios were put into play," she said.
The researchers trawled through historical documents, archaeological archives and fishing records in an attempt to gauge the point when each coral was in its perfectly natural and pristine state.
The scientists found that the slow decline of a coral habitat followed a definite pattern: first, people fished or hunted large predators and herbivores such as sharks, turtles and sea mammals, which are slow to rebuild their numbers.
Next to go are the smaller animals and fishes and they are followed by the "architectural" organisms such as seagrasses and corals themselves, which provide the physical habitat on which the delicate ecology of a reef ultimately depends.
Professor Bjorndal said that it was a surprise to find that the green turtle was hunted to such an extent by the indigenous Bahamians that the species was seriously depleted long before the first European colonists arrived.