At least a quarter of the planet’s reef-building corals face a noticeable risk of extinction, according to the first large scale review of hundreds of species.
Out of 845 known species of warm-water corals, 231 meet the criteria for listing in worrisome categories on the international IUCN Red List of Threatened Species, says marine biologist Kent Carpenter of OldDominionUniversity in Norfolk, Va.
The troubled species fall into the vulnerable, endangered or critically endangered categories on the Red List, which is maintained by the conservation group International Union for Conservation of Nature and Natural Resources.
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If the coral species keep declining, coasts could lose the storm protection and other ecological benefits healthy reefs provide, Carpenter warns. Reef breakdown would have “huge economic effects on food security for hundreds of millions of people dependent on reef fish,” Carpenter and 38 co-authors conclude in a paper to be published in Science that appeared online July 10.
“The Carpenter paper has some scary conclusions,” says marine biologist Jenny Waddell of the National Oceanic and Atmospheric Administration’s reef programs in Silver Spring, Md. She points out that the new paper’s proportion of corals in trouble exceeds the threatened portion of most other big groups of land animals except amphibians.
Carpenter says the new roll of threatened reef corals will be added to the IUCN’s list, increasing 20-fold the number of corals the group tracks.
Monitoring of marine species has lagged compared with terrestrial species, he says. Out of some 40,000 total species the IUCN had evaluated up to now, only 1,400 species live in the sea.
To catch up, the IUCN and environmental group Conservation International fund the Global Marine Species Assessment to review major groups of creatures. For a year and a half, Carpenter has led an international team of marine biologists working through the known species that build classic shallow-water reefs.
Skimpy information kept the researchers from evaluating 141 coral species. For the others, the biologists worked out trends in population growth or decline.
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Reports on shrinking areas of reefs have long indicated trouble for corals, but “we brought a new dimension,” Carpenter says. At the final tally of 231 imperiled species, “everyone’s jaw absolutely dropped.”
Two main kinds of miseries beset the corals, Carpenter says.
Climate change is taking a toll as warming sea water raises the risks of disease and coral bleaching (when corals lose their symbiotic algae and thus face nutrient shortages).
Abundant local threats also hammer corals. Sediments erode into the sea from frenetic development booms along coasts, and boats drag anchors over reefs, smashing structures that took hundreds of years to build.
“If we can control local threats, it will buy us some time,” says Andrew Baker of the University of Miami. “But ultimately corals will face some pretty tough challenges due to high temperatures and acidity.”
That worldwide process of ocean acidification is already altering surface water chemistry as those waters absorb excess carbon dioxide from the atmosphere. Though seawater is not acid now and isn’t expected to become so, the shift could disrupt ecosystems. “The new species analysis’ methods didn’t address this threat,” comments Maoz Fine of Bar-IlanUniversity in Ramat-Gan, Israel, so it “may require a category updating very soon.”
In the audit’s regional view, Caribbean reefs have the largest proportion of corals in the most threatened categories, the paper shows. “I used to dive in the Caribbean — the reefs were gorgeous,” Carpenter says. “Now, to use a technical term repeated frequently around here, they’re toast.”
Caribbean reef vulnerability also showed up in a NOAA report co-edited by Waddell and released July 7 at the International Coral Reef Symposium in Fort Lauderdale, Fla. Every three years, the NOAA reef research program presents a status report on the reef communities off the continental coast and U.S.-related islands.
The 2008 report found 69 percent of Pacific reefs in good or excellent condition but only 25 percent of Caribbean and Atlantic ones ranking that high.
Disturbing as both reports are, Carpenter calls for action, saying “there is hope.”