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1/3 of corals face extinction

1/3 of corals face extinction

1/3 of corals face extinction
July 10, 2008

Nearly one-third of reef-building corals are vulnerable to extinction, according to an assessment of 845 species of coral. Rising temperatures, increased incidence of disease, and human disturbance are driving the trend.

Assessing the conservation status of corals from around the world using IUCN Red List Criteria, an international team of researchers found that 32.8 percent of reef-building corals are in categories with elevated risk of extinction. At greatest risk are corals in the Caribbean and the Coral Triangle of the Western Pacific.

“Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures,” wrote the authors.

Comparison of current Red List Categories for all reef-building coral species to hypothetical Red List Categories back-cast to pre-1998. (CR=Critically Endangered, EN=Endangered, VU=Vulnerable, NT=Near Threatened, LC=Least Concern, DD=Data Deficient).

Corals are besieged by threats at local and global scales. Local threats — which primarily result from human disturbance — include coastal development, sedimentation resulting from erosion and deforestation, sewage discharges, nutrient loading and eutrophication from agricultural run-off, coral mining and overcollection for the pet trade, over fishing, and recreational activities. On a global scale, reefs are imperiled by rising temperatures, which cause bleaching or the expulsion of symbiotic algae that provide corals with sustenance, and ocean acidification, which causes changes in reef communities by making it more difficult for some corals to form carbonate skeletons that serve as their structural basis. These synergetic effects cause physiological stress, weakening corals and leaving them susceptible to infection by pathogens, including bacteria and viruses.

The authors say the results show that the extinction risk of corals has increased dramatically over the past decade, from 13 in threatened categories before 1998 to 231 today. The number of “near-threatened” species rose from 20 to 176 over the same period. The proportion of threatened coral species is second only to amphibians — which are also susceptible to climate change — among animal groups.

The researchers warn that without immediate conservation efforts, a large proportion of coral species may go the way of the dinosaurs, resulting in significant biodiversity loss and economic impacts.

“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,” the authors conclude.

K.E. Carpenter et al. (2008). One Third of Reef-Building Corals Face Elevated Extinction Risk From Climate Change and Local Impacts. Science 10 July 2008.

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