Possibility of worldwide coral bleaching by 2056, new model maps show

26 Feb
In a new article in Nature Climate Change scientists from NOAA's Cooperative Institute for Marine and Atmospheric Studies show maps that illustrate how rising sea temperatures are likely to affect all coral reefs, including those in Polynesia, in the form of annual coral bleaching events under various different emission scenarios. Their results emphasize that without significant reductions in emissions most coral reefs on the planet are at risk for bleaching within the next several decades. Credit: Thomas Vignaud

In a new article in Nature Climate Change scientists from NOAA’s Cooperative Institute for Marine and Atmospheric Studies show maps that illustrate how rising sea temperatures are likely to affect all coral reefs, including those in Polynesia, in the form of annual coral bleaching events under various different emission scenarios. Their results emphasize that without significant reductions in emissions most coral reefs on the planet are at risk for bleaching within the next several decades. Credit: Thomas Vignaud

Many coastal areas who have or once had pristine coral reefs, rely on ecotourism for part of their income. But, once the reefs start to die out, the fish move away and the once sought-after snorkeling spot becomes a skeletal reef for the history books.

Coral reefs aren’t only beneficial economically, they also act as important carbon sinks, and homes and food for marine life. Their value cannot be measured with a price tag since they are a crucial part of the Earth’s ecosystem.

A study published today in Nature Climate Change by University of Miami Rosenstiel School of Marine & Atmospheric Science scientists shows how different levels of carbon emissions can cause coral bleaching. The study used recent data from the  Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) to create climate models. Although some types of coral bleaching can be a localized seasonal event, coral bleaching in mass quantities is caused by water temperatures that are too warm. This is because the algae, or zooxanthellae, that live inside the coral skeleton and give it its color cannot tolerate the temperatures and become expelled from the coral. If too many zooxanthellae become expelled, the corals become malnourished and die.

The climate models showed that if current carbon emissions stay on the path they are currently on, then 74 percent of the worlds coral reefs may experience detrimental bleaching events.

Ruben van Hooidonk, Ph.D., from the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) at the University of Miami and NOAA’s Atlantic Oceanographic and Meteorological Laboratory said that some reefs need more urgent attention.

“Coral reefs in parts of the western Indian Ocean, French Polynesia and the southern Great Barrier Reef, have been identified as temporary refugia from rising sea surface temperatures,” Hooidonk said. “These locations are not projected to experience bleaching events annually until five or more years later than the median year of 2040, with one reef location in the Austral Islands of French Polynesia protected from the onset of annual coral bleaching conditions until 2056.”

Jeffrey Maynard, Ph.D., from the Centre de Recherches Insulaires et Observatoire de l’Environnement (CRIOBE) in Moorea, French Polynesia, says that there is still a little time to try to lower emissions, but it is running out.

“Our projections indicate that nearly all coral reef locations would experience annual bleaching later than 2040 under scenarios with lower greenhouse gas emissions.”  Maynard said. “For 394 reef locations (of 1707 used in the study) this amounts to at least two more decades in which some reefs might conceivably be able to improve their capacity to adapt to the projected changes.”

As history has shown, reducing carbon emissions takes a worldwide effort, which can of course be problematic. This study can perhaps serve as yet another wake up call to planet earth and the humans on it that climate change is real and action needs to be taken. . . fast.

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The study was funded by the Pacific Islands Climate Change Cooperative based in Hawaii, the U.S. National Research Council and CNRS.

AOML, a federal research laboratory, is part of NOAA’s Office of Oceanic and Atmospheric Research, located in Miami, Fla. AOML’s research spans hurricanes, coastal ecosystems, oceans and human health, climate studies, global carbon systems, and ocean observations. For more information, please visit http:/www.aoml.noaa.gov

CIMAS is a research institute based at the University of Miami, within the Rosenstiel School of Marine & Atmospheric Science. It serves as a mechanism to bring together the research resources of nine major public and private research universities in Florida and the U.S. Caribbean with those of NOAA in order to develop a Center of Excellence that is relevant to understanding the Earth’s oceans and atmosphere within the context of NOAA’s mission.  For more information, please visit http://cimas.rsmas.miami.edu/

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