An aerial survey of the northern Great Barrier Reef has shown that 95 per cent of the reefs are now severely bleached — far worse than previously thought.
Professor Terry Hughes, a coral reef expert based at James Cook University in Townsville who led the survey team, said the situation is now critical.
“This will change the Great Barrier Reef forever,” Professor Hughes told 7.30.
“We’re seeing huge levels of bleaching in the northern thousand-kilometre stretch of the Great Barrier Reef.”
Of the 520 reefs he surveyed, only four showed no evidence of bleaching.
From Cairns to the Torres Strait, the once colourful ribbons of reef are a ghostly white.
“It’s too early to tell precisely how many of the bleached coral will die, but judging from the extreme level even the most robust corals are snow white, I’d expect to see about half of those corals die in the coming month or so,” Professor Hughes said.
Coral bleaching is caused by abnormally high sea temperatures that kill the tiny marine algae essential to coral health.
This is the third global coral bleaching since 1998, and scientists have found no evidence of these disasters before the late 20th century.
“We have coral cores that provide 400 years of annual growth,” explains Dr Neal Cantin from the Australian Institute of Marine Science.
“We don’t see the signatures of bleaching in reduced growth following a bleaching event until the recent 1998/2000 events.”
“There’s good and bad news — the bottom three quarters of the reef is in strong condition,” he said at the time.
“[But] as we head north of Lizard Island it becomes increasingly prone to bleaching.”
The northern part of the Great Barrier Reef is the most pristine part of the marine park — and that is one possible glimmer of hope.
“On the bright side, it’s more likely that these pristine reefs in the northern section will be better able to bounce back afterwards,” Professor Hughes said.