Record coral kill-off on Great Barrier Reef raises alarm

A MASS bleaching event on the Great Barrier Reef this year killed more corals than ever before, scientists said yesterday, sounding the alarm over the delicate ecosystem.

The 2,300-kilometre long reef – the world’s biggest – suffered its most severe bleaching in recorded history, due to warming sea temperatures during March and April, with the northern third bearing the brunt.

Follow-up under water sur veys, backing earlier aerial studies, have revealed a 700-kilometre stretch of reefs in the less-accessible north lost two-thirds of shallow-water corals in the past eight to nine months.

“Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef,” said Terry Hughes, head of the Centre of Excellence for Coral Reef Studies at James Cook University. Further south over the vast central and southern regions, including major tourist areas around Cairns and the Whitsunday Islands, there was a much lower toll.

Bleaching occurs when abnormal environmental conditions, such as warmer sea temperatures, cause corals to expel tiny photosynthetic algae, draining them of their colour.

Algae are vital to the coral, which uses the organic products of photosynthesis to help it grow. The loss of algae makes the host vulnerable to disease and means it will eventually die. But coral can recover if the water temperature drops and the algae are able to recolonise them.

Environmentalists blame the burning of fossil fuels for global warming and repeated calls yesterday for Australia to abandon coal mining to help prevent further bleaching disasters.

“This is the devastating price we are paying for the Australian government propping up the coal industry,” said Greenpeace Australia reef campaigner Shani Tager. “A credible plan to protect the reef must address climate change and start with a ban on new coal mines.”

Canberra insists it is doing more than ever to safeguard the reef, which is also under pressure from farming run-off, development and the coral-eating crown-of-thorns starfish, committing more than A$2 billion (US$1.5 billion) over the next decade.

Scientists estimate the northern region, which teems with marine life, will take at least 10-15 years to regain lost corals, but are concerned that a fourth major bleaching event may occur before that, hampering the recovery.

The reef studies centre warned earlier this year that if greenhouse gas levels keep rising, similar events would be the new normal, occurring every two years by the mid-2030s. Given reefs need so long to recover, it said “we are likely to lose large parts of the Great Barrier Reef in just a couple of decades”.