Most Great Barrier Reef coral studied this year was found to be bleached

MORE than 90 per cent of Great Barrier Reef coral surveyed this year was bleached in the fourth such mass event in seven years in the world’s largest coral reef ecosystem, Australian government scientists said.

Bleaching is caused by global warming but this is the reef’s first bleaching event during a La Nina weather pattern, which is associated with cooler Pacific Ocean temperatures. The Great Barrier Reef Marine Authority said in its annual report that 91% of the areas surveyed were affected.

Bleaching in 2016, 2017 and 2020 damaged two-thirds of the coral in the famous reef off Australia’s east coast.

Coral bleaches are a heat stress response and scientists hope most of the coral will recover.

David Wachenfeld, chief scientist at the authority, said: “The early indications are that the mortality won’t be very high. We are hoping that we will see most of the coral that is bleached recover and we will end up with an event rather more like 2020 when, yes, there was mass bleaching, but there was low mortality.”

The bleaching events in 2016 and 2017 led to “quite high levels of coral mortality”, Mr Wachenfeld said.

Simon Bradshaw, a researcher at the Climate Council, an Australiabased group that tracks climate change, said the report shows that the reef’s survival depends on steep global emission cuts within the decade.

“This is heartbreaking. This is deeply troubling,” Mr Bradshaw said. “It shows that our Barrier Reef really is in very serious trouble indeed.”

Last July, Australia garnered enough international support to defer an attempt by Unesco, the United Nations’ cultural organisation, to downgrade the reef’s World Heritage status to “in danger” because of damage caused by climate change.

But the question will be back on the World Heritage Committee’s agenda at its annual meeting next month.

The Great Barrier Reef accounts for around 10% of the world’s coral reef ecosystems and was named because of the extensive hazards it posed to 18th century seafarers.

The network of more than 2,500 reefs covers 134,000 square miles.