Coral bleaching on Great Barrier Reef predicted to worsen with record warm Pacific Ocean temperatures.
The global coral bleaching event – only the third such incident in recorded history – could affect 38% of the world’s coral reefs and destroy 12,000 square kilometres (4,600 square miles) of reef, the researchers said.
The disaster is being brought on by rising ocean temperatures due to climate change, combined with the effects of a natural phenomenon known as El Nino which raises global temperatures and a Pacific warm water mass known as “the blob”.
These are driving oceans to record temperatures, causing the death of corals and depleting the reef systems which support fish, protect coastlines and provide livelihoods for 500 million people.
Dr Mark Ekin from the US government’s National Oceanic and Atmospheric Administration (NOAA) said: “This is only the third time we’ve seen a global coral bleaching event.
“What really has us concerned is this event has been going on for over a year and is likely to last another year.”
The current El Nino, which is contributing to the problem, is expected to be the strongest since 1998 when the first global coral bleaching event was recorded.
Global coral bleaching events, also seen in 2010, are declared when the three major ocean basins, the Indian, Pacific and Atlantic, all see widespread bleaching episodes across multiple reefs spanning 62 miles or more.
During these events corals expel the golden-brown algae which grow within their body tissue, exposing their white skeletons to give a bleached appearance, and if ocean temperatures remain higher than normal for a number of weeks, corals can die en masse.
Professor Ove Hoegh-Guldberg, chief scientist for the XL Catlin Seaview Survey which helped gather the data on the bleaching event, at the University of Queensland, said: “Just like in 1998 and 2010, we’re observing bleaching on a global scale, which will cause massive loss of corals.
“With hundreds of millions of people relying on fisheries and reefs for sustenance, the repercussions of a global coral bleaching event could be potentially disastrous.”
Although reefs cover less than 0.1% of the world’s ocean floor, they help support around a quarter of all marine species.
The news of the bleaching comes as an assessment of the value of natural assets estimated that coral reefs were worth £6 trillion a year in protection from storms, providing fish, tourism and storing carbon emissions – almost four times the entire UK economy.