Exeter scientist warns: the carbon crisis is lethal for coral reefs

In a paper published in leading academic journal Science, 17 eminent marine scientists from seven countries reveal that world leaders face a race against time in preparing coral reefs and the coastal communities dependent upon them for the inevitable impact of rising levels of CO₂ in the Earth’s atmosphere.

On the eve of the International Year of the Reef 2008 the scientists warn that most coral reefs will not survive the rapid increases in global temperatures and atmospheric CO₂ that are forecast this century by the Inter-governmental Panel on Climate Change (IPCC), which released its report a few weeks ago, unless drastic action is taken to curb CO₂ emissions.

The scientists, who are leading members of the international Coral Reef Targeted Research and Capacity Building for Management Program (CRTR), argue that rising global CO₂ emissions represent an ‘irreducible risk’ that will rapidly outstrip the capacity of local coastal managers and policy-makers to maintain the health of these critical ecosystems, if CO₂ emissions are allowed to continue unchecked.

"This crisis is on our doorstep, not decades away,” says Professor Peter Mumby of the University of Exeter’s School of Biosciences, the only UK author on the paper. “Unless we act now, coral reefs are likely to dwindle into insignificance; they’ll be reduced to seaweed beds, rubble and only a few scattered corals. The livelihoods of many millions of people living along the coasts of tropical developing countries will be among the first major casualties of rising levels of carbon in the atmosphere.”

Coral reefs are delicate ecosystems occupying a unique niche in the world’s environment. According to the report, an increase in ocean surface water temperatures of just 1°C will subject coral reefs to stresses that lead quickly to mass bleaching. If temperatures increase further, the corals that build reefs will die in great numbers. The problem is intensified by ocean acidification, which is also caused by increased CO₂. This decreases the ability of corals to produce calcium carbonate (chalk), which is the material that reefs are made of.

Professor Peter Mumby continues: "Coral reefs are the largest living structures on Earth and are home to the highest biodiversity on the planet. The environment that has enabled coral reefs to thrive for hundreds of thousands of years is changing so fast that compensatory biological responses are lagging behind.”

The concentration of CO₂ in the Earth’s atmosphere is 380 parts per million (ppm), which is 80ppm higher than where it has been for the past 740,000 years, if not 20 million years. Increasing atmospheric CO₂ has already brought about a +0.74°C rise in temperature. If current CO₂ emission trends continue, then even the most conservative estimates predict CO₂ concentrations exceeding 500ppm and global temperature increases of 2°C or more by the end of the century.

As world leaders gather for the last day of the United Nations Framework Convention for Climate Change (UNFCCC) meeting in Bali today, the CRTR scientists argue that the issue of global CO₂ emissions demands leadership at the international level, including a collective agreement on carbon emission reductions.

Although action is vital in curbing CO₂­ emissions, this does not negate the need for improved coral reef conservation at local scales. “Better conservation, such as enforcement of fisheries regulations, is essential in order to buy time for coral reefs. If we can reduce local stresses and simultaneously curb CO₂ emissions to within 450 ppm as argued by the 2007 Bali Declaration by Scientists, then coral reefs and the food and housing security of millions of people could yet be saved”, Professor Mumby concluded.

The CRTR is a leading international coral reef research initiative that provides a coordinated approach to credible, factual and scientifically-proven knowledge for improved coral reef management. The CRTR Program is a partnership between the Global Environment Facility, the World Bank, The University of Queensland (Australia), the United States National Oceanic and Atmospheric Administration (NOAA) and approximately 40 research institutes and other third-parties around the world.