Coral Reefs: Is Climate Engineering the Key to Saving Them?

With their numbers rapidly diminishing, the fate of coral reefs has been of utmost concern to scientists around the world in recent years. And while some have said climate engineering, or geoengineering, is not the solution to climate change, a new study says it could be the key to saving the Earth's coral reefs from mass bleaching, at least.

Coral reefs are considered one of the most vulnerable ecosystems to future climate change due to rising sea surface temperatures and ocean acidification, which is caused by higher atmospheric levels of carbon dioxide (CO2). The Great Barrier Reef, for instance, one of the world's most iconic ecosystems, is even at risk of collapsing.

Mass coral bleaching, which can lead to coral deaths, is predicted to occur far more frequently over the coming decades, due to the stress exerted by higher seawater temperatures. Already, these marine organisms are experiencing extensive bleaching events - for example, those in Hawaii are seeing the most intense bleaching in decades, a sign of exhaustion and poor health for corals.

Scientists believe that, even under the most ambitious future CO2 reduction scenarios, widespread and severe coral bleaching and degradation will occur by the middle of this century.

Previous research has suggested that herbivorous and predatory fish are the answer to corals' problems, but now a team of researchers - collectively from the Carnegie Institution for Science, the University of Exeter, the Met Office Hadley Centre and the University of Queensland - proposes that a geoengineering technique called Solar Radiation Management (SRM) may reduce the future risk of global severe bleaching. (Scroll to read on...)

Geoengineering is the large-scale manipulation of the Earth's climate. In this case, the SRM method involves injecting gas into the stratosphere, forming microscopic particles which reflect some of the Sun's energy and thus help limit rising sea surface temperatures.

During the study, the researchers compared a hypothetical SRM geoengineering scenario to the most aggressive future CO2 reduction strategy considered by the Intergovernmental Panel on Climate Change (IPCC). They found that coral reefs fared much better under geoengineering despite increasing ocean acidification.

"Our work highlights the sort of climate scenarios that now need to be considered if the protection of coral reefs is a priority," Dr. Lester Kwiatkowski of the Carnegie Institution for Science, who led the research, said in a statement.

"The study shows that the benefit of SRM over a conventional CO2 reduction scenario is dependent on the sensitivity of future thermal bleaching thresholds to changes in seawater acidity," added Dr. Paul Halloran, from the Geography department of the University of Exeter. "This emphasizes the need to better characterize how warming and ocean acidification may interact to influence coral bleaching over the 21st century."

Despite the optimistic findings, some scientists believe that geoengineering is not the solution to climate change and all the problems that come with it, including ocean acidification. They contend that ocean acidification would continue anyway, and that if geoengineering techniques were ever discontinued, rapidly rising temperatures could cause cataclysmic events as a result.

Despite this warning, the research team still believes that climate engineering is our best bet at saving the world's coral reefs. Other methods of CO2 removal, they argue, could negatively impact factors such as regional crop growth or water availability.

"Coral reefs face a dire situation regardless of how intensively society decarbonizes the economy," noted co-author Peter Cox, from the University of Exeter. "In reality there is no direct choice between conventional mitigation and climate engineering but this study shows that we need to either accept that the loss of a large percentage of the world's reefs is inevitable or start thinking beyond conventional mitigation of CO2 emissions."

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