08-08-2024

Great Barrier Reef is on the brink of extinction

Earth.com staff writer

Due to warming sea temperatures and mass coral bleaching events, the Great Barrier Reef is currently facing critical threats that endanger its remarkable ecology, biodiversity and beauty, according to a new study published in journal Nature.

Study lead author Benjamin Henley is an Honorary Fellow at the University of Wollongong (UOW). Along with his team, Henley has reconstructed 400 years of summer sea surface temperatures in Coral Sea.

Bleaching on the Great Barrier Reef

The investigations revealed that extreme recent ocean heat has caused significant coral bleaching on the Great Barrier Reef. This research provides new evidence of ongoing and future impact of rising sea surface temperatures on this ecological jewel of Australia.

Recently, UNESCO’s World Heritage Committee decided not to list the Great Barrier Reef as in danger. However, Henley and his team argue that – based on their new evidence – the Reef is indeed in peril.

Focus of the study

The team combined sea surface temperature reconstructions using geochemical data from coral cores previously collected from the region.

The researchers also analyzed climate model simulations of sea surface temperatures, both with and without the influence of climate change, concluding that anthropogenic climate change is responsible for the rising temperatures.

Record heat and Great Barrier Reef bleaching

According to the experts, recent mass bleaching events coincide with five of six hottest years in the new 400-year-long record. Specifically, years 2024, 2017, and 2020 saw Coral Sea reaching 400-year highs. The warmest on record, by a large margin, was 2024.

Additional significant heat events occurred in 2016, 2004 and 2022. The repeated sequences of mass coral bleaching have had devastating effects, severely impacting Great Barrier Reef’s unparalleled ecology and biodiversity.

The death of a natural wonder

“When I plotted the 2024 data point, I had to triple check my calculations – it was off the charts – far above the previous record high in 2017. I could almost not believe it. Tragically, mass coral bleaching has occurred yet again this year,” Henley said.

“In the absence of rapid, coordinated and ambitious global action to combat climate change, we will likely witness the demise of one of Earth’s most spectacular natural wonders.”

Great Barrier Reef faces catastrophe

Professor Helen McGregor, from UOW’s Environmental Futures, and the second author of the study, stressed the need for urgent action to prevent the devastation of one of the world’s most important ecosystems.

“There is no ‘if, but or maybe’ – the ocean temperatures during these bleaching events are unprecedented in the past four centuries,” she reported.

“The Great Barrier Reef is facing catastrophe if anthropogenic climate change is not immediately addressed. The very corals that have lived for hundreds of years and that gave us the data for our study are themselves under serious threat.”

Human influence on the Reef

According to Henley, the climate model analysis confirms that human influence on the climate system is responsible for the rapid warming in recent decades.

“Without urgent intervention, our iconic Great Barrier Reef is at risk of near-annual bleaching from high ocean temperatures. The Reef’s fundamental ecological integrity and outstanding universal value are at stake,” said Henley.

According to Henley, immediate action to transition to net zero emissions is necessary. “We have many of the key solutions to stop climate change; what we need is a step change in the level of coordinated national and international action to transition to net zero.

“We can never lose hope. Every fraction of a degree of warming we avoid will lead to a better future for the human and natural systems of our planet. We hope that our study equips policymakers with more evidence to pursue deeper cuts in greenhouse gas emissions internationally.”

Bleaching on a mass scale

Coral bleaching occurs when stress causes corals to expel the algae that live in their tissue, which provide the corals with their vibrant colors. Without the algae, the coral’s white skeleton is exposed.

Environmental disturbances and declining water quality can lead to bleaching, but recent sea temperature warming has caused bleaching on a mass scale.

Although corals can recover if the stress trigger is reduced, the Great Barrier Reef has experienced five major mass coral bleaching events since 2016.

The research has broader implications for coral reef systems worldwide, highlighting the link between the long-term trajectory of extreme ocean temperatures and the ecological health and biodiversity of these critical ecosystems.