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Extinction Countdown

Extinction Countdown

News and research about endangered species from around the world

Coral reefs: Vital to the oceans, vital to humans

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Coral reefs are dying off at record rates, thanks to pollution, disease and global warming. Scientists worldwide are trying to come up with new ideas to conserve and protect not just the coral reefs, but also the biodiversity and human economies that depend upon  them for their survival.

Last month,  a group of 155 scientists from 26 countries issued a document dubbed  "The Monaco Declaration," calling for a reverse in the current 3 percent annual increase of carbon dioxide (CO2) emissions by 2020, noting the pollution makes its way to the oceans, where it has been steadily raising acidity levels (30 percent  since the 17th century). If CO2 emissions continue rising at their current levels, the document warns, “ocean acidification may render most regions chemically inhospitable to coral reefs by 2050.”

Acidification and warming surface waters have been blamed for the rise in coral bleaching, which is killing off coral  worldwide. Coral bleaching occurs when corals become stressed by above-average ocean water temperatures or water acidification. Once stressed, the coral expel the symbiotic algae that both feeds them and provides the corals' color. The coral turn pale or white, and quickly die. In the process, the entire ecosystem that depends upon the reefs becomes threatened. But now research published in the journal Estuarine, Coastal and Shelf Science suggests that human actions  may help  reverse some of the damage caused by coral bleaching.

"Bleaching has resulted in catastrophic loss of coral cover in some locations, and has changed the coral community structure in many others,"  says study co-author. Peter Glynn, a professor of coral reef biology and disturbance ecology  at the University of Miami Rosenstiel School of Marine and Atmospheric Science in Miami, Fla. "These dramatic fluctuations have critical impacts on the maintenance of biodiversity in the marine tropics, which is essential to the survival of many tropical and sub-tropical economies."

Glynn and co-authors Andrew Baker of U-Miami and Bernhard Riegl, associate director of the National Coral Reef Institute, examined more than 25 years of reef ecosystem recovery data and hundreds of previous coral studies. They were able to catalog not only the dangers that bleaching poses to coral reefs, but also how some reefs have shown greater ability to bounce back from bleaching damage.

"These findings illustrate how coral reefs, under the right conditions, can demonstrate resilience and recover from bleaching, even when it initially appears catastrophic"  Baker says. "What prevents them from doing so is the lethal prescription of combined, additional stressors that prevent them from recovering in-between recurrent bleaching events. If we can remove or reduce these stressors we might give reefs a fighting chance of surviving climate change."

According to their paper, actions humans can take to help damaged coral and "maintain ecosystem resilience" include "restoring healthy levels of herbivory, macroalgal cover, and coral recruitment." The latter involves finding similar coral near dying reefs and reintroducing healthy larvae to help sick reefs regenerate.

Baker  tells The Christian Science Monitor he plans to  conduct a three-year study into heat-resistant algae, in the hopes that some coral could be "inoculated" with different types of algae that  could survive in rising ocean temperatures.

Another new study published this week in the journal Current Biology, found that fish on coral reefs in the western Indian Ocean are being depleted, due to the health of the reefs and the socioeconomic health of the humans living nearby. "Moderately developed" places "have the technology to plunder their reefs, but not the institutions to protect them or the levels of development that allow for sufficient alternatives to fishing," says lead study author Joshua Cinner, a post-doctorate fellow at the ARC Centre of Excellence for Coral Reef Studies and  James Cook University in Townsville, Queensland, Australia. The paper suggests the best way to sustain these coral fisheries is to build up the development of the countries fishing them while establishing protected areas where reefs need to be rebuilt.

That research echoes the findings of a report issued late last year by the Global Coral Reef Monitoring Network and its parent organization, the International Coral Reef Initiative, a partnership among governments, international organizations, and non-government organizations to preserve coral reefs and ecosystems. The report, "Socioeconomic Conditions Along the World's Tropical Coasts: 2008," recommends developing alternative income streams for fishermen, involving local communities in decisions about their natural resources, and educating local peoples about the importance of healthy reef ecosystems.

"This study, based on case studies worldwide, shows that people's livelihoods, food security and coastal economies depend on marine resources," says Leah Karrer, senior director of Conservation International's Marine Management Area Science Program, which funded the study. "As much as 90 percent  of coastal families are dependent on fishing as a primary source of income and as much as 54 percent  of gross domestic product is from tourism."

Image: © Andrew C. Baker

The views expressed are those of the author and are not necessarily those of Scientific American.

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