Coral Eaters

Great Barrier Reef ravaged by predatory starfish

Tropical storms, bleaching, and coral-devouring starfish have diminished the iconic Great Barrier Reef by about half since 1985, a long-term study shows.

Reefs are under assault from pollution, overfishing, warming waters, acidification, and construction along the coasts. The Great Barrier Reef is better off than some reefs because it is relatively well-protected and remote. But stresses such as agricultural run-off and predatory crown-of-thorns starfish are still straining the ecosystem.

The study authors evaluated 2,258 surveys of the reef taken from 1985 to 2012. Coral cover dropped by 50.7 percent during that time, with most of the losses occurring during the last 15 years. Cyclones caused 48 percent of the damage, while starfish caused 42 percent and bleaching 10 percent, the team estimates in Proceedings of the National Academy of Sciences. The southern region was the hardest-hit, while the northern part remained fairly intact.

Warmer oceans may be triggering stronger cyclones, and nutrient run-off from farms may be helping crown-of-thorns starfish to flourish, the authors suggest. If managers make an effort to control starfish outbreaks — for example, by reducing agricultural pollution — the reef could begin to recover. — Roberta Kwok | 2 October 2012

Source: De’ath, G. et al. 2012. The 27-year decline of coral cover on the Great Barrier Reef and its causes. Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1208909109.

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