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Scientists are calling for a major overhaul of the way coral reefs are managed. In particular, they are urging that more attention be paid to the type — rather than the number — of species present in reef ecosystems.

Failure to do so "could have devastating economic effects on maritime developing countries", say the researchers in a report in this week's Nature.

Coral reefs provide food and livelihood to hundreds of millions of people, mostly in developing nations. But overfishing, pollution, sedimentation, and bleaching linked to climate change are all having significant impacts on the world's reefs.

The researchers examined factors contributing to a coral reef's 'resilience', in other words its ability to withstand such human pressures. They found that herbivorous fish play an important role. By removing dead coral and feeding on algae, these fish play a central role in reef maintenance and regeneration. And they help reefs resist change towards seaweeds dominating over corals, which would have drastic impacts on local fisheries.

"It's rather like a city," explains David Bellwood, director of the Centre for Coral Reef Biodiversity at James Cook University, Australia, and lead author of the study. "If the population drops by ten per cent, the city may still function adequately. But if it loses its transport workers or garbage collectors or police or firemen or doctors, the city would collapse. The jobs people do are more important than their total numbers."

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