Coral reefs that have lots of corals and appear healthy may, in fact, be heading toward collapse, according to a study published by the Wildlife Conservation Society and other groups.
Using data from coral reef systems across the western Indian Ocean, an international team of researchers identified how overfishing creates a series of at least eight big changes on reefs that precipitate a final collapse. This information can help managers gauge the health of a reef and tell them when to restrict fishing in order to avoid a collapse of the ecosystem and fishery.
The study appears this week in the early online edition of the Proceedings of the National Academy of Sciences. The authors of the study include: Tim R. McClanahan and Nyawira A. Muthiga of the Wildlife Conservation Society; Nicholas A.J. Graham and Joshua E. Cinner of James Cook University, Queensland, Australia; M. Aaron MacNeil of the Australian Institute of Marine Science; J. Henrich Bruggemann of Laboratoire d'Ecologie Marine, Universit de la Runion, La Runion, France; and Shaun K. Wilson of the Department of Environment and Conservation, Perth, Western Australia.
The authors say these changes are like a series of light switches, each of which make the reef more degraded and dims the chances of sustained fishery production and recovery.
"The study identifies eight changes before all of the ecological lights go off and the reef and fishery are gone" said Dr. McClanahan, the lead author on the study and the head of WCS's coral reef research and conservation program.
The study shows that in well-protected areas, there are typically 1000-1500 kilograms of reef fish of various species per hectare of coral reef. As the volume is fished down below 1000 kilograms, the early warning signslike increased seaweed growth and urchin activitybegin to appear. The researchers found that between 300-600 kilograms per hectare, there appeared to be a "window" o
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Wildlife Conservation Society