Cut greenhouse gases to save coral reefs

Ocean acidification is a threat to corals caused by global warming.

Ocean acidification is a threat to corals caused by global warming.

To keep coral reefs from being eaten away by increasingly acidic oceans, humans need to limit the amount of climate-warming greenhouse gases in the atmosphere, a panel of marine scientists said.

"The most logical and critical action to address the impacts of ocean acidification on coral reefs is to stabilise atmospheric carbon dioxide concentration," the scientists reported in a document called the Honolulu Declaration, for release at a US conference on coral reefs in Hawaii.

Ocean acidification is another threat to corals caused by global warming, along with rising sea levels, higher sea surface temperatures and coral bleaching, the scientists added.

Coral reefs are a "sentinel ecosystem," a sign that the environment is changing, said one of the experts, Billy Causey of the US National Marine Sanctuary Programme.

"Although ocean acidification is affecting the health of our oceans, the same thing - increased carbon dioxide in the atmosphere - is going to in fact be affecting terrestrial environments also," stated Dr Causey.

Coral reefs offer economic and environmental benefits to millions of people, including coastal protection from waves and storms and as sources of food, pharmaceuticals, jobs and revenue, the declaration said.

But corals are increasingly threatened by warming sea surface temperatures as well as ocean acidification.

Oceans are getting more acidic because they have been absorbing some 525 billion tons of the greenhouse gas carbon dioxide over the last two centuries, about one-third of all human-generated carbon dioxide for that period.

The carbon dioxide combines with sea water to form carbonic acid.

Marine researchers have long recognised acidification in deep ocean water far from land, but a study published this year in the journal Science found this same damaging phenomenon on the Pacific North American continental shelf from Mexico to Canada, and quite likely elsewhere around the globe.

The water became so corrosive that it started dissolving the shells and skeletons of starfish, clams and corals.

Stabilising carbon dioxide emissions was the Honolulu Declaration's top long-term recommendation. The key short-term recommendation was to nurture coral reefs that seem to have natural resilience against acidification.

This could be adopted immediately by managers of protected marine areas, Dr Causey remarked.

The Honolulu Declaration will be presented to the United Nations and to other global, regional and national fora.


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