The Great Barrier Reef of Australia, which experienced unprecedented bleaching, last year has now been struck by another massive bleaching event.
Last year’s bleaching damaged mainly the northern part of the reef whereas the latest damage is concentrated in the middle section. The coral bleaching in consecutive years has damaged two-thirds of the world’s largest living structure. According to scientists, the back-to-back severe bleaching events will give damaged coral little time to recover.
An aerial survey conducted by the scientist with the Australian Research Council’s Centre of Excellence for Coral Reef Studies assessed 800 coral reefs across 8,000 km. Results of the survey showed that the mass bleaching events have only left the reef’s southern third unscathed.
Jon Brodie, a water quality expert who has devoted much of his life to improving water quality on the reef, said the reef was now in a “terminal stage.”
“We’ve given up. It’s been my life managing water quality, we’ve failed. Even though we’ve spent a lot of money, we’ve had no success. Last year was bad enough; this year is a disaster year. The federal government is doing nothing really, and the current programs, the water quality management is having very limited success. It’s unsuccessful,” said Brodie.
Bleaching occurs when coral reefs experience water that runs warmer than their summer maximum for over a month. The overly warm water causes corals to lose their colorful symbiotic algae that provide nutrients. If the water becomes stable soon after, corals can heal themselves, but if the condition persists, corals calcify and die.
While bleaching occurs naturally, scientists are concerned that rising sea temperatures caused by global warming magnifies the damage, leaving sensitive underwater ecosystems unable to recover.
“The bleaching is caused by record breaking temperatures driven by global warming. This year, 2017, we are seeing mass bleaching, even without the assistance of El Niño conditions," said professor Terry Hughes from James Cook University's Centre of Excellence for Coral Reef Studies.
He further added, “Clearly the reef is struggling with multiple impacts. Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events. 1°C of warming so far has already caused four events in the past 19 years.”
According to scientists, this year’s bleaching episode is likely to be the result of destructive crown-of-thorns starfish, poor water quality and the category-four cyclone Debbie, as its slow movement across the reef was likely to have caused destruction to coral along a path up to 100 km wide.
“It added to the woes of the bleaching. It came too late to stop the bleaching, and it came to the wrong place,” said Hughes.
As Australia relies on coal-fired power plants for electricity, it makes the country one of the largest carbon emitters per capita. Climate scientists have been concerned and argue that the increased carbon dioxide in the atmosphere traps heat radiating from earth, thus creating global warming. They have also been highly critical of the federal and Queensland state governments' support for the proposed Adani Carmichael coal mine in Queensland's Galilee Basin.
The proposed mine will be the largest in the country producing 60 million tons of coal a year.
“Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing," warned Hughes.