"This [one-third] is much higher that any of us thought would be the case when we started this process," Suzanne Livingstone of Old Dominion University, US, told environmentalresearchweb. "This is a higher percentage of species with the risk of extinction that any other group assessed to date, other than amphibians, which are 42% threatened. This shows that marine species are just as, or more, threatened than many terrestrial species."

Livingstone and colleagues from 33 organizations around the globe assessed 845 species of reef-building coral for the risk of extinction using the IUCN Red List categories and criteria.

"Corals are particularly under threat from climate change and increased carbon dioxide in the atmosphere – warming water temperatures producing increasing bleaching [where corals evict the symbiotic algae that live alongside them and provide nutrients] and disease, and rising pH levels leading to acidification," said Livingstone. "Localized threats such as pollution, over-fishing on reefs, siltation, coastal development also are contributing heavily to the stresses on corals, which also makes them more susceptible to bleaching and disease."

The Caribbean had the largest proportion of corals in high risk categories while the "Coral Triangle" in the Indo-Malay-Philippine Archipelago in the western Pacific had the highest proportion of species in all categories of elevated risk. The scientists say that the chronic nature of anthropogenic disturbance in many parts of the area is compounded by the effects of climate change.

"This is new research, as it looks at each reef-building coral on a global scale, and reflects the risk of extinction based on where the species are present, and due to their life history traits such as how deep they can live, and whether they are more or less resistant to bleaching events and disease, or collected for trade," said Livingstone.

Livingstone says that we need to act now to protect this important marine habitat. "Over 25% of marine species rely on coral reefs for food and shelter, and if the reefs disappear, then so do the plants and animals that are associated with them," she said. "This has serious implications for humans, especially in coastal regions, many of whom rely on coral reefs for food, livelihoods and income generation."

The team’s coral species assessments are now available on the IUCN Red List of Threatened Species website. They expect further research will be done to examine their results further and to identify the species and regions most in need of protection. "This can be done by on the ground conservation activities, for example, Conservation International uses Red List assessments on all their conservation planning and identification of 'Hotspots' and 'Key Biodiversity Areas'," said Livingstone.

"It is extremely important now to reduce the localized stresses on coral reefs so that they may have a chance of adapting to the effects of climate change, and evolve to become more resilient to warming waters and bleaching and disease," added Livingstone. "The additional stress that the localized threats put on the corals makes it extremely difficult for corals to be able to do this. It is also very important to reduce carbon dioxide levels though carbon emissions. We need to help corals through this crisis in every way we can."

The researchers reported their work in Sciencexpress.