Its northern reaches suffered an unprecedented two successive years of severe bleaching in 2016 and 2017, prompting the government agency overseeing the reef to downgrade its long-term outlook to "very poor".
In August previous year, the Great Barrier Reef Marine Park Authority's five-yearly report downgraded its reef outlook from "poor" to "very poor" noting widespread habitat loss and degradation affecting fish, turtles and seabirds.
"The inshore section between Cairns and Townsville is certainly severely bleached".
The Australian Research Council Centre of Excellence for Coral Reef Studies is conducting aerial surveys, and its director Terry Hughes has been posting updates throughout the week. In the case of the Great Barrier Reef, warmer waters in the area cause destructive and widespread coral bleaching. If a coral is bleached, it doesn't mean it is dead, and if it is only a mild or moderate level of bleaching, it will often recover. "Climate change remains the single greatest challenge to the reef", said the agency. The crisis placed renewed pressure on Prime Minister Scott Morrison's pro-coal conservative government to take more extensive action to tackle climate change, including punishing greenhouse-gas polluters.
The Great Barrier Reef has endured mass bleaching events in 1998, 2002, 2016, 2017 and now in 2020. But repeated bleaching events that are widespread and of great severity pose a real threat to ecosystems like the Great Barrier Reef, making it hard for them to recover before the next wave hits.
Earlier this month, David Wachenfeld, chief scientist at the Great Barrier Reef Marine Park Authority, said ocean temperatures over the next month will be crucial to how the reef recovers from heat-induced bleaching.
"We don't yet know how many corals may die as a result of this event", Dr Heron said.
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