CORAL CRISIS?: Nearly one-third of coral species, like Purites pukoensis pictured here, are threatened with extinction by climate change and other manmade problems.
Image: ©DONALD C. POTTS
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
A survey of 704 species of coral—tiny polyps with hard shells, some of which form spectacular underwater reefs—has found that nearly 33 percent of them face a greater threat of becoming extinct as the globe warms. The main culprits, according to the study published today in Science: bleaching—when corals expel the algae that normally feeds them and gives them color—as well as disease outbreaks in coral weakened by warming sea-surface temperatures.
"If we cannot manage the [carbon dioxide] in the atmosphere, there's a very good possibility that bleaching events and disease events will be occurring with greater frequency and, if that occurs, there is a good chance that some species are not going to be able to replenish themselves fast enough," says marine biologist Kent Carpenter of Old Dominion University in Norfolk, Va., who led the research. "Add ocean acidification [also caused by rising CO2 levels in the atmosphere], which is even more insidious than ocean warming, and you've got a real dire picture."
Researchers assessed the health of coral species worldwide by measuring declines in their abundance on the reefs and ocean beds they call home and then used criteria developed by the International Union for Conservation of Nature (IUCN) to determine the risk of extinction. Previous studies have found declines of as much as 80 percent in the number of coral living within particular reefs.
"Corals are the backbone of the ecosystem," Carpenter notes, and reefs harbor roughly one quarter of all known marine species—from fish to algae. "What is going to happen to that huge biodiversity that is dependent on coral reefs? We don't know, but our consensus is that it would most probably lead to a massive loss of biodiversity in the oceans."
A similar assessment of coral health in U.S. waters released this week by the National Oceanic and Atmospheric Administration (NOAA) concluded that roughly half of the coral species in these waters are struggling and continue to decline.
"Predictions are that within 50 to 100 years not only will we see decline in growth rates for corals and other shell-dependent species—they may actually begin to dissolve," says marine biologist Jenny Waddell of the NOAA Center for Coastal Monitoring and Assessment, who helped prepare the report. Climate change "is somewhat of an x-factor. We don't really know how resilient corals are."
The U.S. government did, however, take the unprecedented step in 2006 of listing two species of coral—Elkhorn (Acropora palmata) and Staghorn (Acropora cervicornis)—as threatened under the Endangered Species Act. This means that both Caribbean reef-builders face a significant risk of extinction within the next 30 years. Plans for how to deal with that threat and protect the two species are still being finalized, according to Weddell.
But not all marine biologists agree that corals are in dire straits. "Clearly lions and tigers are threatened by extinction when there are currently only a few thousand of them left. But is a coral species, whose population was reduced from maybe a billion to 300 million or even a few hundred thousand, really threatened by extinction? Personally, I very much doubt it," says marine biologist John Bruno of the University of North Carolina at Chapel Hill. "But I think the ecological function of many reef-building corals is threatened by quite drastic losses in their abundances."
Instead of focusing on saving individual coral species, Bruno argues, the overall health of the oceans could be protected by managing the protection of coral reefs to maximize their overall abundance—which would then also have the effect of maximizing the numbers of all the species that rely on them for food or habitat.
The goods news is that coral reefs can recover within decades, according to Bruno and Waddell, a process that has already started to occur at some reefs in the Caribbean and Pacific. But only if they are free of man-made pressures such as water pollution, overfishing and climate change.
And if the tiny polyps continue to be pummeled by these factors? The outlook is grim, Carpenter warns. "Whether or not [coral species] actually do go extinct depends on whether corals continue to have more frequent bleaching events and disease events because of increased sea-surface temperatures," he says. "If these events continue to become more frequent, there's a real possibility."
See what we're tweeting about
8 Comments
Add CommentIf the coral are endangered now, how did they survive the previous extreme changes in climate/temperature? Are they new creatures since the last climate swing? Or is this more politically correct climate change hysteria?
Reply | Report Abuse | Link to thisNASA's own Argo system of 3100+ buoys around the world, sampling ocean temperatures down to 3000 meters indicates that average ocean temperatures have been falling since Argo official inception in 2003. An "inconvenient truth"?
Reply | Report Abuse | Link to thisThe key statement is " face a greater threat" this does not say they will or won't be, it's actually a chicken @$%^ non-prediction prediction which allows the predictor to be correct no matter what happens. this is no better than me saying you will stub your toe if you walk in the dark, you might not today but someday you may and I'll be correct. The Scientific problem with this study is that quite probably that thru-out history 33% have probably always come into existance or gone extinct, otherwise there is no evolution or fossil record. To conclude another useless article by so called scientist promoting man made global warming, to what end?. Control of the population much like religions used to do, or is it just for financial gain?
Reply | Report Abuse | Link to thisWater in the ocean circulates as a conveyer belt, surface water warms in the tropics, travels poleward where it cools and sink then travels in the depths until it is upwelled. This circulation process is a very slow process in human terms (it takes around 1000 years). So water at the depths does NOT represent the recent history of climate. And the biggest treat to corals reefs comes from ocean acidification due to increase CO2 atm. This has never been so high, at least for the last million of years. Some corals had survived other warm periods but other hasn’t, in fact in the past reefs hasn’t been always dominated by corals.
Reply | Report Abuse | Link to thisstill dose not answer my question why are the coral reefs dieing?
Reply | Report Abuse | Link to thisReply to srchuck: NASA itself says the the data were wrong and corrected itself. Please see http://earthobservatory.nasa.gov/Features/OceanCooling/page1.php. The ocean is <b><i>not cooling</i></b>.
Reply | Report Abuse | Link to thisIt seems like this problem has been anticipated for years
Reply | Report Abuse | Link to thiswith little being done. The 1973 film "Soylent Green" with
Charlton Heston depicts similar conditions with horrible
results.
an inconvenient truth? i think not, and if you don't believe me, maybe you can check NASA.gov, heres the link. http://www.nasa.gov/topics/earth/features/mls20100519.html
Reply | Report Abuse | Link to thisand that false data? in '06 false data was showing a decline in ocean temp. later, the paper author, Josh Willis discovered the problems with the data and published a correction.