SOMETIMES it鈥檚 easy to spot the twist at the end of a tale. Not so with the story of coral reefs across the ages, for here it鈥檚 only on the last page that the villain turns up.
鈥淥ur results leave little option but to lay the blame on people,鈥� says Jeremy Jackson of the University of California, San Diego, who with John Pandolfi of the University of Queensland in Brisbane, Australia, has been studying the fossilised remains of coral reefs off Barbados. Humans have caused more damage in the past 30 years than the reefs have experienced at any time in the last 220,000 years, they say (Ecology Letters, vol 9, p 818).
The fossil record shows that the reefs had been dominated by a large branching species called Elkhorn coral as recently as a century ago.
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Until then the reefs had survived intact through hurricanes, climate change and geological movement. Yet now they are overwhelmed by algae and seaweed. 鈥淭he recent changes in the composition of the coral communities we studied are unprecedented,鈥� Jackson says.
There have been few other studies of a coral population beyond four decades, Jackson says. He blames overfishing, over-enrichment of nutrients such as phosphates, and surplus sediment from coastal land clearing and erosion for the greatest damage.
鈥淗uman activities have not only destroyed coral but have altered the reefs鈥� composition and diversity鈥�
He adds that these problems affect reefs worldwide. The evidence from the new study should help restoration efforts by giving a clearer picture of what the reef looked like before humans arrived, though it is not known whether the damage is reversible. Human activities have not only destroyed coral but altered the reefs鈥� composition and diversity.
Robert Buddemeier of Kansas Geological Survey says there is clear evidence that humans have caused a great deal of damage to coral reefs.
He points out, however, that a lack of evidence in the fossil record for a similar level of disruption from natural causes does not mean that it didn鈥檛 happen. 鈥淚f there were 50 to 100 years where coral reefs were greatly reduced or altered, would you find evidence of that? Only if you were very lucky or imaginative,鈥� he says.
