ABC
We may be overestimating the extinction risk of individual marine species on coral reefs but this is no cause for complacency, scientists warn.
This week's issue of Current Biology reports on a new study on the distribution and abundance of over 400 tropical coral and fish species.
The study challenges the criteria used to put species on the IUCN Red List.
A key assumption used in making this list of species threatened with extinction is that a species will be at risk if it has a very small range and very small population.
"There's an assumption that those two things occur together quite often," says marine biologist Professor David Bellwood of the ARC Centre of Excellence for Coral Reef Studies at James Cook University
This "double jeopardy" concept arose from observations in terrestrial animals, says Bellwood, but there has been little evidence that it applies to marine animals.
"The original IUCN approach to listing the extinction risk of organisms was based on terrestrial systems where it appears to work reasonably well," says Bellwood.
"[But] people have tended to assume you can transfer the approach lock, stock and barrel to the sea with limited data," he says.
Bellwood and colleagues investigated the geographic ranges and abundance of species of corals and fishes in the Indian and Pacific oceans.
"What the data shows is that this double jeopardy doesn't turn up anywhere near as often as thought," says Bellwood.
The researchers found that corals and fishes that had small ranges often had huge numbers and those that had large ranges could be quite rare.
Bellwood says the findings do not support claims published in Science in 2008 that one third of corals are at risk of extinction.
"Vulnerability in the sea seems to differ in the way it occurs to on land."
But, he warns, double jeopardy could still apply to some marine animals
"If you've got a small dolphin that lives in one estuary or a couple of rivers on the side of an island, it could indeed be vulnerable," he says.
