Great Barrier Reef coral die-off reaches tragic, new record

Bleaching caused by warmer water is estimated to have killed about 67 percent of the coral in a previously pristine, 430-mile northern stretch of the reef.

First Look

Rising water temperatures destroyed large swathes of the Great Barrier Reef in Australia this year, marking the largest annual die-off in history, according to a new study.

The Great Barrier Reef stretches along Australia’s coastline for more than 1,400 miles, making it the most extensive reef in the world and the largest ecosystem made entirely of living organisms on the planet. Researchers at the ARC Centre of Excellence for Coral Reef Studies found that around 67 percent of corals in the reef’s hardest-hit northern section died, while only 6 percent or less suffered in the central and southern sections.

Still, experts warn that recovery on the reefs and protecting other segments could prove difficult, if not impossible, should climate change continue to cause water temperatures to rise.   

"We had bleaching here in 2002," Anne Hogget, a local researcher, told the BBC. "We thought this was bad at the time, but this has blown it completely out of the water."

The reef suffered from coral bleaching, a process in which hotter temperatures cause the coral to become distressed and dispel algae living on them, which creates the vibrant colors seen on the reef. In addition to drawing tourists from around the world, the reef also provides a habitat for underwater organisms and protects the shoreline from storms.

Because around 25 percent of the ocean's fish live in a coral reef during some stage of their lives, a declining reef habitat can cause major disruptions to the ecosystem and food chain, also impacting people who rely the sea for food and employment. "Coral reefs are therefore the most biologically diverse ecosystems of the planet, and provide a number of ecosystem services that hundreds of millions of people rely on," Greg Torda, of the Centre, told USA Today. "These include provisioning (fishing, other types of harvesting, for pharmaceuticals, for example), coastal protection, aesthetic and cultural values – to name a few. If corals are lost, so are all the services they provide to humans; and so are all the species that directly or indirectly rely on them."

Saving the reefs is likely to require officials to develop long-term sustainability plans, and the Australian government has already created a program to financially support research into the coral bleaching process. Canberra has also pledged to lower carbon emissions by 2050 and search for new ways to increase the reef’s resilience.

Still, say some climate experts, it’s important that researchers, officials, and civilians act now to prevent further damage, as procrastinating on the effort will only make the process more expensive and less effective.

Some Australian scientists say that the nation isn’t on track to meet its 2050 carbon emission goals. And researchers advocate other steps to protect the reefs such as reducing local water pollution, as Denmark and China have done, by altering land use for agriculture, which led to some local reef recovery.

Australia's reefs are "not going to disappear tomorrow, but the more we lose the harder it is to restore it," Chris Langdon, a marine biologist at the University of Miami, previously told The Christian Science Monitor. "Actions now will be less drastic than what could be required later."