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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."

The problem is that herbivorous fish are increasingly targeted both by subsistence and commercial fisheries. Demand in China, Taiwan and Singapore for live reef fish has recently risen – as have prices, which can reach US$250 per kilogramme. This trade has had major impacts on reefs in the Indian and Pacific oceans.

"In recent years, the live fish trade has brought commercialised fishing to increasingly remote locations, and has added an additional threat," Bellwood told SciDev.Net. "The trend is made particularly dangerous by the fact that there are few feedbacks between the economics of the live fish trade and the ecological impact of exploitation."

In many developing countries, reef degradation means less income and a reduction in available protein for coastal fishing communities. Lack of funds limits the ability of such countries to address these problems, says Bellwood. "It is in these areas that the challenges are the greatest but where we have, perhaps, most to gain. It is also in these areas where local stewardship of reef resilience may be the most effective."

The scientists recommend that reef management move away from focusing on totally protected areas within 'hotspots' of high species diversity, warning that small-scale, local successes in such no-fishing areas may not be enough to halt the decline of reefs as a whole.

Calling for active management of critical 'functional groups' of species — such as herbivorous fish — to be conducted at a regional scale, they urge reef governance systems to be more inclusive and proactive. And they say that economic incentives preventing exploitation of critical groups are needed before — not after — stocks collapse.

"It is not simply a case of excluding people from reef areas," says Bellwood. "We view people as part of the reef ecosystem. We just need to learn how to tread lightly."

Link to full review paper in Nature

Reference: Nature 429, 827 (2004)

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