It’s official: the Great Barrier Reef is being battered by yet another major coral bleaching event. This is the fifth such event in just eight years, marking a horrendous blow for the much-loved and much-troubled reef. 

The ongoing bleaching event was confirmed on March 8 by the Australian Institute of Marine Science (AIMS) in collaboration with the Great Barrier Reef Marine Park Authority. 

The grim confirmation comes after helicopter flights over the southern Great Barrer Reef documented extensive coral bleaching in late February. The aerial surveys gathered dated on over 300 inshore, mid-shelf, and offshore reefs, in the Great Barrier Reef’s southern and central regions.

“When bleaching becomes common across many sectors of the Great Barrier Reef, including both inshore and offshore reefs, it becomes a mass bleaching event,” Dr Neal Cantin, a AIMS Senior Research Scientist who led the aerial surveys, explained in a statement.

“As the Great Barrier Reef ecosystem is so large, the size of Italy, the heat stress across it isn’t uniform. As a result, we are seeing differences between reefs with respect to the number of corals that are completely white. This pattern largely follows the pattern of accumulated heat stress seen over the past few months,” continued Cantin. 

Mass bleaching events are inextricably linked to warming ocean temperatures caused by human-made climate change.

They occur when there's a breakdown between the mutually beneficial relationship between corals and the algae that live in their tissues. The coral provides the algae with surface area for photosynthesis, while the algae provide the coral with their surplus sugar. However, the algae can become stressed and leave the coral’s tissue when they’re subject to disease, pollution, or excess heat.

Without their algae comrades, the coral lose a major source of food, making them weak and susceptible to disease. The algae are also what gives the coral their bright colors, so their absence leaves them looking pale and white, hence the term “bleaching”.

Given its link to climate change, bleaching events are a modern phenomenon. The Great Barrier Reef has seen previous mass bleaching events in 1998, 2002, 2016, 2017, 2020, and 2022. According to scientists at AIMS, the extreme temperatures seen in 2023 and so far this year meant that another bleaching event was somewhat inevitable.

“In the last northern hemisphere summer there was record breaking heat stress in the Caribbean and the Eastern Pacific, causing severe and widespread coral bleaching. This mass coral bleaching event on the Great Barrier Reef is part of a global pattern of extreme heat, caused by climate change,” explained AIMS Research Program Director Dr David Wachenfeld.

In a video posted on X, Australian environment minister Tanya Plibersek said the news highlights why their government is "working hard to reduce carbon emissions in Australia, to do our part in the global effort to reduce carbon emissions, and also to make sure we're transitioning Australia to more renewable energy.” 

However, environmental groups have accused the government of being hypocritical, claiming they are pretending to protect the reefs while simultaneously bolstering the fossil fuel industry. 

“Claims that Australia is taking the health of the Great Barrier Reef seriously ring hollow when we continue to expand and subsidise the coal and gas industry to the tune of billions every year. The Australian government can not in good faith approve climate bombs like Woodside’s Burrup Hub and say that they care about the Reef’s future,” David Ritter, Greenpeace Australia Pacific CEO, said in a statement. 

"Relentless pollution from coal, oil and gas is Australia’s number one environmental problem and it’s literally cooking the Reef. Our environmental protection laws are outdated and in desperate need of an overhaul to prevent new reef-destroying gas and coal projects," added Climate Council CEO Amanda McKenzie.