One third of coral species face extinction

By Roger Highfield, Science Editor
Last Updated: 7:01pm BST 10/07/2008

One third of the major reef-building coral species are vulnerable to extinction, and the pace of destruction is increasing so it is conceivable that the "rainforests of the ocean" could be wiped out this century.

The warning that coral communities are faring even worse than their terrestrial counterparts, notably tropical rainforests, is given by an international team led by Prof Kent Carpenter, Director of the Global Marine Species Assessment Of Conservation International And The International Union For Conservation Of Nature, IUCN.

The loss of reefs will expose costal communities to greater storm surges
Built over millions of years, coral reefs are home to more than 25 percent of marine species, making them the most biologically diverse of marine ecosystems.
The loss of reefs could have huge economic effects on food security for around 500 million people who are dependent on reef fish for food and/or their livelihoods and tourism is also likely to suffer.
"The results of this study are very disconcerting," said Prof Carpenter, lead author of the Science article.
"When corals die off, so do the other plants and animals that depend on coral reefs for food and shelter, and this can lead to the collapse of entire ecosystems."
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"Whether corals actually go extinct this century will depend on the continued severity of climate change, extent of other environmental disturbances, and the ability of corals to adapt," the article concludes.
"Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures."
Researchers identified the main threats to corals as climate change and local stresses resulting from destructive fishing, declining water quality from pollution, and the degradation of coastal habitats.
Climate change causes rising water temperatures and more intense solar radiation, which lead to coral bleaching and disease often resulting in mass coral mortality. Bleaching happens when the water temperature rises to the point where it kills the tiny polyps that make up the coral, leaving behind the white limestone skeleton of the reef.
With colleagues, Prof Carpenter has compiled data for over 700 coral species and classified their conservation status according to the IUCN "Red List" Categories and Criteria. Their analysis indicates that, of 704 species, 231 are in the "Critically Endangered," "Endangered," or "Vulnerable" categories.
The results also indicate the extinction risk of corals has increased over the past decade. Before the massive bleaching events of 1998, which wiped out around 16 per cent of reefs, only 13 species would have been included in the three threatened categories based on the data available today. The vast majority - 671 - would have been categorised as of "least concern."
The Caribbean has the largest proportion of corals in high extinction risk categories, with notable declines of staghorn and elkhorn corals, while the Coral Triangle (Indo-Malay-Philippine Archipelago, western Pacific) has the highest proportion of species in all categories of elevated extinction risk, notably as a result of warming.
Corals in oceanic islands of the Pacific generally have the lowest proportion of threatened species and Hawaiian reefs have been spared extensive coral loss from bleaching or disease. However, it hosts several rare species may prove especially vulnerable to future threats. Corals from the genera (group of species) Favia and Porites were found to be the least threatened due to their relatively higher resistance to bleaching and disease.
Marine researchers at the International Coral Research Symposium (ICRS) in Fort Lauderdale, Florida, this week are exploring the longer term consequences of widespread loss of corals due to global warming and ocean acidification.
Chair of the Climate Change session, Prof Ove Hoegh-Guldberg of the ARC Centre of Excellence for Coral Reef Studies and University of Queensland, said: "The evidence suggests reef systems are becoming more brittle, as a result of bleaching, disease and the effects of acidifying water - and this means we are likely to see more moonscape-like areas where reefs once used to be. This will be accompanied by a switch from the spectacularly colourful fish that people normally associate with reefs to much fewer and plainer ones."
"The loss of reefs will also expose coastal communities, already facing rising sea levels, to a greater risk from storm surges and tsunamis - as reefs currently provide a protective barrier against these," he said.
"This will be accompanied by murkier, less productive waters as water quality suffers." Researchers have found evidence that the rate at which coral reefs have been deteriorating and disappearing has accelerated in the last five years.
"For the past 30 years the loss has been between 1-2 per cent of the world’s coral per year," he said. "The latest data suggests the rate is now around 2 per cent a year. This doesn’t give us much time."
Emerging evidence indicates some corals have suffered a 20 per cent reduction in their growth rates, which researchers consider to be due to the rising acidification of sea water making it harder for them to build their chalky skeletons.
"This apparent drop in calcification is bound to be a real issue for discussion at the symposium," he said.
Most disturbing of all were recent claims by some atmospheric researchers that the level of carbon dioxide has been underestimated, and may be closer to 410 parts per million, than to the 385 estimated by the Intergovernmental Panel on Climate Change (IPCC).
"If we continue on the pathway that we are on right now, we get to levels where you are looking at the total loss of reef structures worldwide. Under those conditions you just don’t have corals - no corals, and you also lose 50% of the fish and other species that live in and around corals," he said.
"We either reduce our carbon dioxide emission now or many corals will be lost forever," says Julia Marton-Lefèvre, IUCN Director General.
"Improving water quality, global education and the adequate funding of local conservation practices also are essential to protect the foundation of beautiful and valuable coral reef ecosystems."