Photo: Pixabay/Kanenori

Among the world’s ecosystems most vulnerable to climate change are coral reefs. “Coral reefs are very much the rainforests of the oceans,” observes the Knowledge Project. “Not only are they diverse communities, but the coral skeletons — like trees — potentially contain long-term records of climate which can be interpreted in terms of temperature, salinity, and anthropogenic impact,” it explains.

“However, while coral reefs can be compared to rainforests, they are also the canaries of the sea, being very sensitive to small changes in the chemical and physical condition of their environment. Modern coral reefs — whether deep or shallow — are under attack from a wide range of local and globally distributed anthropogenic factors,” the science educational website adds.

Coral reefs cover less than 0.1% of the world’s oceans, yet they are home to a third of marine species. They also serve an important role in protecting coasts from storm flooding as they can break waves and diminish their destructive power. Without reefs coasts would be far more subject to devastating floods.

In addition, reefs generate plenty of income for local economies, their economic benefits reaching a total tally of $10 trillion a year, according to estimates. In annual tourism revenues alone reefs contribute $36 billion.

Yet reefs everywhere are under attack from a variety of man-made stresses, climate change among them, and they are facing an existential crisis, according to the International Coral Reef Society, an international team of researchers representing thousands of coral scientists worldwide.

“The model projections show that up to 30% of coral reefs will persist through this century if we limit global warming to 1.5 degrees Celsius,” says Andréa Grottoli, a professor of earth sciences at Ohio State University, who was an author of a new paper detailing the risks coral reefs face.

“But if we are to limit warming to 1.5 degrees, we have to do it now. The science and the models show that we have only a few years left to reduce carbon dioxide emissions that put us on that path. It has to happen this decade, or we won’t make that target,” Grottoli explains.

To save embattled reefs, three strategies will need to be adopted worldwide, Grottoli and his colleagues say: 1) addressing climate change, 2) improving local environmental conditions and 3) restoring damaged reefs if necessary. Failing that, more and more reefs could well experience heat-induced mass bleaching episodes, which could endanger not only the health of fragile corals but the health of entire ecosystems that depend on them.

“From a coral reef perspective, we go from 30% of reefs surviving to only a few percent surviving if we don’t act now,” Grottoli says. “We are already faced with a grand challenge in trying to restore the reefs. Once we do eventually reduce carbon dioxide emissions and the planet is no longer warming at an accelerated rate, trying to restore from just a few percent is much more difficult.”

The experts are calling on politicans and other decision makers worldwide to enact polices that can ensure the continued survival of reefs, including meaningful climate change mitigation efforts and biodiversity restoration projects in collaboration with local communities that live near those reefs.

The latter is of great importance as water pollution, mass tourism and unsustainable fishing practices, too, pose grave risks to coral reefs and the myriad of marine creatures that inhabit them.

“As bad as climate change has been for the last decades, we also have lost vast amounts of coral reefs through overfishing, pollution and other local actions, and we need to tackle both of those fronts simultaneously,” says Nancy Knowlton, the Sant Chair for Marine Science Emerita at the Smithsonian Institution’s National Museum of Natural History.

“Climate change is important but it’s important that these other things aren’t neglected. There’s no time for arguing about which is most important; we need to do all of them,” Knowlton stresses.

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