Great Barrier Reef in critical condition

Australian scientists estimate that mass coral bleaching has killed off around 35 per cent of corals on the northern and central Great Barrier Reef. That figure will likely rise as some of the remaining corals fail to recover.

Coral reef scientists have found that mass coral bleaching is having a devastating effect on the northern and central Great Barrier Reef. Around 35 per cent of the corals are now dead or dying, said Professor Terry Hughes, director of the ARC Centre of Excellence for Coral Reef Studies at the James Cook University.

“This year is the third time in 18 years that the Great Barrier Reef has experienced mass bleaching due to global warming, and the current event is much more extreme than we’ve measured before,” explained Hughes. “We’re rapidly running out of time to reduce greenhouse gas emissions.”

Aerial and underwater surveys revealed that the impact of global warming changes dramatically from north to south along the 2300-kilometre length of the reef. But even on the reefs south of Cairns, where more than 95 per cent of the corals have survived, the coral bleaching is likely to slow down their reproduction and growth rates.

According tothe scientists, the reefs in the south were less affected because water temperatures there are closer to normal summer conditions. Warmer waters in the north, in contrast, is causing the corals to expel tiny photosynthetic algae, called zooxanthellae, which in turn causes the corals to turn white and bleach.

The scientists warn that the reef is struggling to cope with three bleaching events in just 18 years and is no longer as resilient as it once was. “Many coastal reefs in particular are now severely degraded,” said Professor John Pandolfi of the University of Queensland.

As Reuters reports, the latest findings are a major blow to the world heritage site, which attracts around USD 3.59 billion in tourism each year.


Image credit: Sarah Depper, flickr/Creative Commons

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