Reef-building corals face extinction

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Scientists from 11 countries have conducted the first comprehensive global assessment of reef-building corals and have found that a third of them are threatened with extinction.

The results of the assessment are published in a recent issue of the journal Science by a team of 39 coral experts led by Kent Carpenter, which applied International Union for Conservation of Nature Red List Criteria and Categories to 845 coral species worldwide.

The authors found that of the 704 coral species that could be assigned conservation status, 32.8% (231 species) are in categories with elevated risk of extinction (141 species has insufficient data to complete a Red List assessment).

In the study, the main threats to corals were identified as rising sea temperatures and ocean acidification resulting from climate change and localized anthropogenic stresses resulting from increased coastal development, sedimentation resulting from poor land-use and watershed management, sewage discharges, nutrient loading and eutrophication from agro-chemicals, coral mining, and overfishing.

The Acroporidae (staghorn coral), Euphylliidae (hammer, torch, frogspawn, bubble, elegance and fox corals) and Dendrophylliidae (sun, cup and pagoda corals) were found to be the most extinction-prone, with about half the species listed in the threatened category; the Meandrinidae (maze corals) and the Oculinidae (galaxy corals) are similarly threatened with about 40% of the species listed as vulnerable.

The scientists conclude: ur analysis indicates that the extinction risk for many corals is now much greater than it was before recent massive bleaching events. Whether corals actually go extinct this century will depend on the continued severity of climate change, the extent of other environmental disturbances, and the ability of corals to adapt.

If bleaching events become very frequent, many species may be unable to reestablish breeding populations before subsequent bleaching causes potentially irreversible declines, perhaps mimicking conditions that led to previous coral extinctions.

If corals cannot adapt, the cascading effects of the functional loss of reef ecosystems will threaten the geologic structure of reefs and their coastal protection function and have huge economic effects on food security for hundreds of millions of people dependent on reef fish.

Our consensus view is that the loss of reef ecosystems would lead to large-scale loss of global biodiversity.

For more information, see the paper: Carpenter, KE et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science 321, pp. 560"563.