Last year, the Great Barrier Reef was hit by the worst coral bleaching ever. Scientists have now anxiously confirmed that the reef is facing massive bleaching for a second year in a row. Climate change is the number one threat facing this natural wonder, as Barbara Barkhausen reports from Sydney.
Just a few months ago the coral shimmered brightly in all their colourful glory. Now huge areas are again ghostly pale.
Warmer than normal sea temperatures are currently bleaching the Great Barrier Reef for the second consecutive year, as was announced by the Great Barrier Reef Marine Park Authority after it conducted an extensive aerial survey between Cairns and Townsville.
Bleaching causes serious damages
2016 had been the worst year for the Great Barrier Reef until now. Never before had so many corals died as they did last year.
With surface sea temperatures at least one degree higher than normal, 93 per cent of the coral had bleached. In some regions, the creatures were able to recover, but countless died, included some coral that were 50 to 100 years old.
The worst affected zone was in the north of the reef, a region that had survived the earlier bleaching in 1998 and 2002 relatively unscathed. But in 2016, around 67 per cent of the coral died over a 700-kilometre stretch.
The northern tip of the reef fared somewhat better, where only 26 per cent of the creatures failed to recover.
Reef is important economic factor
The Great Barrier Reef is one of Australia’s main attractions. It brings AUD 5 billion each year to the economy, and around 70,000 jobs are closely linked to the reef.
In total, the world cultural heritage consists of nearly 3,000 individual reefs, making it the world’s largest single structure made by living organisms. It is even visible from outer space.
But more important: the reef is home to 1,500 fish species and 400 types of coral.
When bleaching occurs, the coral turn white because their symbiosis with a type of algae – which provides the cnidarians with energy and lends them their bright colours – is interrupted.
If the water remains too warm for too long, the coral cannot recover and die.
Climate change is the greatest threat
A 2012 study showed that around 50 per cent of all coral died in the past 30 years. Previous coral bleaching events took a heavy toll on the reef, which had already been weakened by agricultural run-off, the expansion and operation of coal ports, storms and crown-of-thorns starfish, which feed on coral.
In April 2016, a further study conducted by leading Australian climate and reef experts showed that coral bleaching on the Great Barrier Reef has become 175 times more likely due to climate change.
Should greenhouse gases continue to rise in the atmosphere, the scientists pessimistically predict that bleaching will occur every two years by 2030.
The reef is currently bleaching for the second time in a row, though the extent of this year’s bleaching is still unknown.
Over the coming weeks, the leading coral expert Terry Hughes plans to conduct aerial surveys of the same 1,150 reefs that he observed last year during the mass bleaching. “I’m already afraid now,” the scientist wrote on Twitter.