Great Barrier Reef Faces Record Coral Loss Amid Climate Change: AIMS survey

One third of hard coral cover was lost across the Cooktown-Lizard Island sector, marking the "largest annual decline" in 39 years, a survey by the Australian Institute of Marine Science (AIMS) revealed.

This coral mortality is likely due to multiple stressors, including mass bleaching, the impact of two cyclones and other environmental factors, according to the latest data.

Between August and October, AIMS conducted surveys of 19 reefs spanning from Lizard Island to Cardwell. The surveys found that 12 of these reefs experienced coral mortality rates of up to 72 per cent.

The tropical summer brought the impact of Tropical Cyclones Jasper and Kirrily, alongside a freshwater inundation between December 2023 and March 2024, which are believed to have contributed to the reef's deteriorating condition.

“These initial results show the vulnerability of the Reef to bleaching events, which are increasing in frequency, footprint, and intensity due to climate change. Its resilience is being severely tested,” said Manuel Gonzalez Rivero, AIMS acting research programme director.

“The 2024 mass bleaching event on the Reef, the fifth since 2016, is part of the fourth global bleaching event impacting both the northern and southern hemispheres of the Atlantic, Pacific, and Indian Oceans during 2023 and 2024. This event has been documented in more than 60 countries and territories worldwide,” Rivero added.

Read More: Scientists Discover World’s Largest Coral in Solomon Islands, Visible from Space

Rivero also stressed the broader threat to reefs globally due to climate change, “Their future relies on strong greenhouse gas emissions reduction, management of local and regional pressures, and the development of approaches to help reefs adapt to and recover from impacts, which we are already seeing.”

What is the Great Barrier Reef?

Located off the coast of Queensland, the Great Barrier Reef is a site of remarkable variety and beauty on the northeast coast of Australia. It encompasses the world’s largest collection of coral reefs, including 400 varieties of coral, 1,500 species of fish, and 4,000 types of molluscs. The Reef is one of the world's seven natural wonders and a UNESCO World Heritage Area.

Stretching about 2,300 km (1,429 miles) off the northeastern coast of Australia, it is considered one of the most species-rich habitats on Earth. The reef is home to hundreds of coral species, more than 1,600 species of fish, 133 species of sharks and rays, and 30 species of whales and dolphins, among other creatures.

What Causes Mass Bleaching on the Great Barrier Reef?

Bleaching occurs when water temperatures rise, causing the coral to expel the microscopic algae, known as zooxanthellae, that live within them. Without these algae, the corals lose their vibrant colors and turn white. Prolonged exposure to high temperatures leads to coral death. The Great Barrier Reef has been experiencing this phenomenon due to rising sea temperatures.

From an economic perspective, these recurring mass bleaching events negatively impact tourism, as vibrant corals turn white, disrupting the revenue that relies on visitors coming to see the living reef.

The latest survey also found that Acropora, a type of fast-growing coral, had the highest mortality rate. While Acropora corals grow quickly, they are among the first to bleach when temperatures rise.

Mike Emslie, head researcher, told public broadcaster ABC that the past summer was “one of the most severe events” across the Great Barrier Reef, with heat stress levels surpassing those of previous events. “These are serious impacts. These are serious losses,” he said.

 Read More: Global Coral Reefs Is Undergoing Fourth Massive Bleaching Event

Need to Commit to Stronger Emission Reduction Targets

Richard Leck, head of oceans at the World Wide Fund for Nature (WWF)-Australia, expressed that the initial surveys confirmed his “worst fears.” He warned that while the Great Barrier Reef can bounce back, its resilience has limits. “We are fast approaching a tipping point,” he said.

Leck emphasised that, given Australia’s position as one of the world’s largest gas and coal exporters, the country must commit to stronger emission reduction targets—at least 90 percent below 2005 levels by 2035—and transition away from fossil fuels.

He expressed that this is essential to safeguard the future of the Great Barrier Reef and meet global climate goals, especially in light of Australia's recent pledge to achieve carbon neutrality.