Coral Reefs Facing Severe Threat from Ocean Acidification

The Policy Team last night attended a lecture at the Royal Society delivered by J.E.N. ‘Charlie’ Veron, a world-leading expert on corals. Charlie has spent much of his career studying corals at the Great Barrier Reef, off the coast of Queensland in Australia, but has more recently devoted his life to spreading the word about the terrible threats to coral reefs posed by climate change.

Over the course of the hour’s lecture, introduced by Sir David Attenborough, and subsequent questions, the threats to corals became clear, and frighteningly so. Corals exist at the interface between the land, sea and atmosphere: a unique and vulnerable position. Corals depend on an optimum temperature to survive: in the Great Barrier Reef system this is approximately 31 degrees celcius. An increase in temperature causes the symbiotic organisms which live inside the coral, the zooxanthellae, to over-produce oxygen, killing the coral: this is observed as a ‘bleaching’ event. Charlie said that he hadn’t observed coral bleaching before 1980 but since then it has become all too common and has now been observed in every major coral system across the globe.

Charlie presented a synopsis of the likely effect on coral as the concentration of carbon dioxide in the atmosphere, and hence in the oceans which absorb huge amounts of carbon dioxide, increases with time. As the concentration of carbon dioxide in the oceans increases, chemical reactions result in the increasing prodction of hydrogen ions. These hydrogens bind with carbonate ions, which are used by corals to build calcium carbonate skeletons. Disruption of this chemical reaction means that corals are no longer able to build their skeletons and so disrupts reef building.

At 350ppm, mass coral bleaching events were observed all over the world. At today’s concentration of 387ppm, there is compounding long-term degradation of the Great Barrier Reef. 450ppm, the target for the Copenhagen negotiations in December, will cause mass-bleaching most years, and at 500ppm and above shallow water corals will disappear. If the carbon concentration was to rise as high at 800ppm, those corals remaining would be askeletal and would not be associated with reefs.

The degradation of coral reefs is a huge environmental and socioeconomical issue. Not only do reefs support hotspots of biodiversity, providing habitat for up to nine million species, but they provide natural wave-breaks, protecting coastline, and support fishing and tourism industries. The livlihoods of many coastal communities depend on the ecosystem services provided by coral reefs.

Speaking at the end of the meeting, Sir David Attenborough offered a direct challenge to the scientific community. He said we all have a duty to support politicians, providing information, to make sure that their voices are as loud and as authoritative as possible at the Copenhagen negotiations. Reducing carbon emissions is paramount, and widespread geo-engineering must form part of this.

Following the lecture, members of the scientific community signed a statement setting out the results of a workshop, held earlier in the day, in which scientific consensus was reached regarding the likely impact of ocean acidification on coral reefs and the ‘safe limits’ within which carbon emissions should be held to prevent widespread degradation of reefs before 2100.