Fifth of Corals Are Dead, CO2 Destroys Ocean Habitat

One-fifth of the world’s corals have died and many remaining reefs may be lost by 2050 as carbon dioxide from cars and pollution-spewing industries make ocean water warmer and more acidic, the Global Coral Reef Monitoring Network said.

While natural disasters such as the earthquake that set off the Indian Ocean tsunami in 2004 killed some reefs instantly by forcing them out of the water, seas made warmer by heat-trapping CO2 gas is the biggest threat to corals, said the report from the International Union for Conservation of Nature. The Gland, Switzerland-based group is one of eight that manages the network.

The study was released as delegates from about 190 nations are meeting in Poland to lay the groundwork for a new treaty to fight global warming that is due to be signed a year from now in Copenhagen. The report shows that to sustain corals, CO2 emissions as well as damage from human activities must be kept to a minimum, said Clive Wilkinson, coordinator of the monitoring network.

“If nothing is done to substantially cut emissions, we could effectively lose coral reefs as we know them, with major coral extinctions,” Wilkinson said in the report.

The fate of corals is crucial to the livelihoods of millions of coastal dwellers around the world. Reefs are worth about $30 billion a year to the global economy through tourism, fisheries and coastal protection, according to the Millennium Ecosystem Assessment, a United Nations-supervised study.

Reef-Damaging Humans

Coral reefs, however, have been damaged by human activities including fishing, chemical pollution and by disasters such as the tsunami four years off Sumatra that killed about 229,000 people.

The UN Intergovernmental Panel on Climate Change says temperatures have risen by about 0.76 degrees Celsius (1.4 degrees Fahrenheit) since the 19th century due mainly to greenhouse-gas emissions from burning oil, coal and gas. Further gains of 1-2 degrees would result in the bleaching of most corals, a process that makes them more vulnerable to dying off, the UN said.

The biggest future threat to reefs is climate change, scientists and researchers say.

Losing corals would spell the “death of a nation,” Amjad Abdulla, director-general of the Maldives Environment Ministry, said last week in an interview at the UN talks in Poznan, Poland.

“Coral reefs are the natural barriers from sea-level rise and storm surges,” Abdulla said. “With the sea level rise and the bleaching of corals, we’d be homeless.”

Expelling Friends

Corals build reefs by secreting exoskeletons of calcium carbonate that accumulate over hundreds of years. The corals have a symbiotic relationship with zooxanthellae, single-celled algae that shelter in their tissues and provide the reef-building organisms with nutrition and energy, enabling faster growth.

Warmer temperatures, disease and pollution cause corals to expel the zooxanthellae. Because the algae are the source of the corals’ bright colors, when they are rejected, it is known as bleaching, and the process makes corals more likely to die.

To contact the reporter on this story: Alex Morales in Poznan, Poland, via

Alex Moreales,, 10 December 2008. Article.

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