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 News :. Bigger is best for coral reefs
Size really does matter when it comes to conserving the diversity of coral reefs, a new study shows.

The survey of corals and fish in all the Indo-Pacific reefs has highlighted the need to protect coral habitats on a large-scale.

Coral reefs are the most diverse of all marine ecosystems with estimates of reef species ranging from 600,000 to more than 9 million species worldwide. But the most pronounced diversity exists in the western Pacific and Indian oceans and decreases with distance in all directions.

David Bellwood and Terry Hughes from
James Cook University tried to understand this pattern by analysing the numbers of coral and fish species associated with 113 reef communities stretching from the Red Sea to the Gulf of California.

They looked at the relationship between diversity and latitude, longitude, reef type (offshore versus continental) and the availability of suitable habitat within 600 kilometres. By far the best predictor of biodiversity at these sites was the size of the surrounding reef.

"Finding an area rich in diversity and putting a fence around it is one approach to conservation that's been tried on land," Dr Bellwood told ABC Science Online. "But this "ark mentality" doesn't work in the sea. You need large areas."

Many marine parks around the world were only tens or hundreds of square kilometres in size, but this may not be big enough, he said.

Even Australia's Great Barrier Reef, although massive was vulnerable because environmental damage could limit its effective size.

The research has shown that this can affect diversity in very predictable ways, with the ratio of different types of organisms staying fairly constant at any given spot.

"We can say how many fishes and what kinds of fishes will be left. And if the area is small enough the whole system can collapse."
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