‘Underwater bushfire’: GBR suffers worst-ever heat stress – Scuba Diver Mag

Share this post on:

The Great Barrier Reef (GBR) has been suffering through its worst-ever heat stress, with more than 80% of the reefs enduring dangerous levels of heating, according to Australia’s Climate Council.  

Scientists are grappling to quantify the amount of irreparable cumulative damage from repeated such events, says the council, which describes itself as the country’s independent, evidence-based organisation on climate science, impacts and solutions.

Basing its latest assessment on reports from the Great Barrier Reef Marine Park Authority (GBRMPA), the National Oceanic & Atmospheric Administration (NOAA) in the USA and other experts, the Climate Council says that the GBR has been subject to greater levels of heat stress than during any of the previous six mass bleaching events.

Almost half (46%) of individual reefs that make up the GBR experienced record heat stress, according to analysis of NOAA Coral Reef Watch data, while more than 60% of the individual reefs have shown “prevalent bleaching” in the latest GBRMPA assessment.

Proportion of GBR's individual reefs that endured heat stress of more than 4 Degree Heating Weeks (DHWs) - one week of water temperatures 4°C above average represents 4 DHW. Based on NOAA Coral Reef Watch data (Climate Council)
Proportion of GBR’s individual reefs that endured heat stress of more than 4 Degree Heating Weeks (DHWs) – one week of water temperatures 4°C above average represents 4 DHW. Based on NOAA Coral Reef Watch data (Climate Council)

Surveys show coral-bleaching affecting an area likened in size to the land burned during Australia’s 2019–20 bushfire season, known as Black Summer, according to Climate Council.

Also, marine scientists have reported that coral-bleaching has been occurring at greater ocean depths than previously recorded – along with centuries-old corals succumbing to the extreme heat.

‘Shadow of former glory’

“This is the latest event in a slow-unfolding disaster that is fundamentally altering the reef,” states the organisation. “Repeated mass-bleaching events started occurring in the late 1990s due to marine heatwaves driven by climate pollution. 

“Every part of the GBR has bleached at least once since then, with some areas bleaching four times, with little recovery time. As a result the GBR is fading to a shadow of its former glory.” 

“An underwater Black Summer is ravaging the treasured Great Barrier Reef right now,” commented Climate Council CEO Amanda McKenzie. “The survival of the reef – and all life that depends on it – hinges on our willingness to drastically cut climate pollution in the 2020s, which means scaling up clean energy as quickly as possible so we can phase out coal, oil and gas. 

“While the GBR fades before our eyes, the Australian government continues to wave through new coal, oil and gas projects. Our national environment law is failing the very things it’s supposed to protect.” 

‘Disaster at our doorstep’

“Marine heatwaves, fuelled by climate pollution, have dealt blow after blow to the GBR,” added research director Dr Simon Bradshaw. “We’re likely now witnessing the most widespread and severe mass bleaching event ever recorded. 

“Southernmost parts of the reef, which had been largely spared previously, have been hit particularly hard this time, with bleaching affecting many more species, extending to greater depths and affecting some of the oldest and most resilient corals.

“This is a disaster at our doorstep: a direct result of collective failure to cut climate pollution fast enough. Australia can accelerate the build out of renewable energy and move swiftly beyond fossil fuels so that we protect the places we all love and depend on before it’s too late.”

Also read: Great Barrier Reef health described as ‘very poor’ due to climate change, Best coral coverage in 36 years, Great Barrier Reef health, Scientists say new corals on Great Barrier Reef down by 89 percent

Share this post on: