World’s coral reefs will die without drastic action on climate change: study

Coral reefs off the coast of Japan's Tsushima Island (LiveScience photo)Most of the world's coral reefs are in dire risk of dying unless climate change is drastically reduced, a new study has shown.

The study, conducted by researchers from Germany, Australia and the University of British Columbia, is the first to express the results of a survey of coral bleaching around the world in terms of temperature rises linnked to climate change.

"Our findings show that under current assumptions regarding thermal sensitivity, coral reefs might no longer be prominent coastal ecosystems if global mean temperatures actually exceed two degrees Celsius above the pre-industrial level," says Dr. Katja Frieler, lead author of the study.

Coral reefs are extremely sensitive to temperature changes. Corals are marine animals, however, they get most of their energy and nutrients from photosynthetic algae — called zooxanthellae — that live inside them. If the temperature rises too high, the symbiotic relationship between the coral and the algae breaks down, and the algae leave, causing the coral to 'bleach'. Without its primary source of food, the coral quickly dies, which upsets the entire marine ecosystem built up around the coral reef.

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According to Dr. Stuart Sandin of the University of California San Diego's Scripps Institution of Oceanography, the entire coral reef ecosystem provides benefits to us: "They provide food for a lot of people, they provide shoreline protection, they provide species that are providing us with new drugs," he said in an interview with Huffington Post.

"Every year a new species are found that provide new drugs for people. They provide income for communities that have dive tourism nearby. There are a lot of people that get a lot of benefits out of them."

Back in 1992, countries around the world made an international treaty, the United Nations Framework Convention on Climate Change (UNFCCC). They agreed that emissions of greenhouse gases must be significantly reduced and that any further rise in global temperatures should be kept to below two degrees C over pre-industrial levels — the same limit that Dr. Frieler stated would be necessary to prevent the collapse of coral ecosystems. However, a 2011 report suggested that efforts over the past decade may have been insufficient to meet the UNFCCC's goal.

"The window of opportunity to preserve the majority of coral reefs, part of the world's natural heritage, is small," says co-author of the study Malte Meinshausen, who is a senior researcher at the Potsdam Institute for Climate Impact Research and an Honorary Senior Research Fellow at the University of Melbourne.

"We close this window if we follow another decade of ballooning global greenhouse-gas emissions."

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