File photo taken in October 2016 shows coral bleaching at the Great Barrier Reef in Australia, a World Heritage Site.
CNN  — 

Australia’s Great Barrier Reef is suffering another mass bleaching event, the reef’s managers confirmed Friday, the result of soaring ocean temperatures caused by the global climate crisis and amplified by El Niño.

This is the seventh mass bleaching event to hit the vast, ecologically important but fragile site and the fifth in only eight years.

Aerial surveys conducted by the Great Barrier Reef Marine Park Authority and Australian Institute of Marine Science spanned two-thirds of the marine park and confirmed “a widespread, often called mass, coral bleaching event is unfolding across the Great Barrier Reef.”

The unfolding bleaching event follows similar reports from coral reefs around the world during the past 12 months, the reef’s managers said.

Covering nearly 133,000 square miles (345,000 square kilometers), the Great Barrier Reef is the world’s largest coral reef, home to more than 1,500 species of fish and 411 species of hard corals. It contributes billions of dollars to the Australian economy each year and is promoted heavily to foreign tourists as one of the country’s – and the world’s – greatest natural wonders.

But warming ocean temperatures are fueling destructive bleaching of the reef, as the world burns planet-heating fossil fuels. Ocean temperatures are also becoming even hotter under the current El Niño — a natural climate pattern that brings warmer-than-average sea-surface temperatures — which is one of the strongest on record.

“Climate change is the biggest risk not just to the Great Barrier Reef in Australia but also to coral reefs around the world,” said Australia’s Environment Minister Tanya Plibersek in a video statement. “We know that we need to give our beautiful reef the best chance of survival for the planet and animals that call it home, for the 64,000 people whose livelihoods depend on reef tourism.”

The team conducted aerial surveys on more than 300 inshore, mid-shelf and offshore reefs, and found “prevalent shallow water coral bleaching” on most reefs surveyed. In-water surveys, which can assess the severity and depth of coral bleaching, were ongoing, the authority said.

Bleaching occurs when stressed coral ejects algae from within its tissue, depriving it of a food source. If the water temperature remains higher than normal for too long, coral can starve and die, turning white as its carbonate skeleton is exposed.

But scientists say corals can recover if ocean temperatures stabilize.

“The Reef has demonstrated its capacity to recover from previous coral bleaching events, severe tropical cyclones, and crown-of-thorns starfish outbreaks,” the authority said.

Severe mass bleaching at the Great Barrier Reef had previously been observed in 1998, 2002, 2016, 2017, 2020 and 2022.

The 2022 event was the first during a La Niña event, El Niño’s counterpart, which tends to have a cooling influence – raised serious concerns about the reef’s outlook.

A ‘wake-up call’

In a statement, the Australian Marine Conservation Society (AMCS) said the government of Australian Prime Minister Anthony Albanese must dramatically cut greenhouse gas emissions and stop approving new fossil fuel projects.

“It’s devastating,” said AMCS Great Barrier Reef campaign manager Dr. Lissa Schindler. “This is a huge wake-up call for Australia and the global community that we need to do much more to address climate change, which is driving the marine heatwaves that lead to coral bleaching.”

The Australian government has been under pressure to prove that it’s doing enough to save the reef.

It has pledged one billion Australian dollars ($660 million) spread over 10 years to support new climate adaptation technology, investment in water quality programs, and protection for key reef species.

While the extra funding was welcomed, the government has been called out by global climate experts, among others, for not doing enough to transition Australia away from fossil fuels and reduce emissions in line with keeping global warming to 1.5°C – a critical threshold for coral reefs.

Sunrise over the Great Barrier Reef at Lady Elliot island on October 10, 2019.

By continuing on the current pathway, “we risk losing the Great Barrier Reef and the $6 billion sustainable tourism industry,” said Schindler. “Our children and grandchildren may never experience the Reef that we know and love.”

Greenpeace Australia Pacific CEO David Ritter said the confirmation of a mass bleaching event was a “devastating blow.”

“We know that the climate crisis is driving deadly marine heatwaves and devastating our marine ecosystems, but the frequency and scale at which these mass bleaching events are now occurring is frightening — every summer we’re holding our breath,” he said in a statement.

“Claims that Australia is taking the health of the Great Barrier Reef seriously ring hollow when we continue to expand and subsidize the coal and gas industry to the tune of billions every year.”

According to the Australia Institute’s Coal Mine Tracker, the Labor government has approved four new coal mines or expansions since coming to power in May 2022.

Fears for global mass bleaching event

Last year, the warmest year since global records began in 1850, according to the US National Oceanic and Atmospheric Administration’s (NOAA) annual climate report, saw ocean temperatures surge to 100 degrees Fahrenheit (37 degrees Celsius) in some regions and the bleaching of entire reefs.

With water temperatures climbing to unprecedented heights, NOAA last month added three new levels to its alert system to account for increasingly severe coral bleaching and higher mortality rates.

Alert Level 5, the new highest level classified as “near complete mortality,” means greater than 80% of corals in the highlighted area are at risk of dying due to high, long-lasting water temperatures.

This week, the NOAA said the world was on the verge of a fourth global mass coral bleaching event that could see the entirety of the Southern Hemisphere bleached, according to a report by Reuters.

“We are literally sitting on the cusp of the worst bleaching event in the history of the planet,” ecologist Derek Manzello, the coordinator of NOAA’s Coral Reef Watch, reportedly said.

On Wednesday, the NOAA’s Coral program said coral bleaching was expected to continue “on multiple, major reef areas in the central equatorial and southwestern Pacific and western Indian Oceans due to ongoing marine heatwaves.”