Great Barrier Reef Suffers Largest Ever Coral Loss in 2024 Due to Marine Heatwave: Report

In 2024, the Great Barrier Reef experienced its most devastating coral bleaching event on record, resulting in significant losses of hard coral cover across multiple regions. This catastrophic decline was attributed to a global mass coral bleaching event that impacted numerous countries, characterized by unusually high water temperatures and an El Niño weather pattern.

According to the Australian Institute of Marine Science (AIMS), the reef lost between 25% and 33% of its hard coral cover during this period. In certain areas, particularly those hardest hit, losses approached 70%. The report found that the bleaching event covered the largest area ever recorded on the Great Barrier Reef, with declines in both the north and south regions being the most significant since monitoring began 39 years prior.

During visits to the Great Barrier Reef in 2024 and Ningaloo Reef in 2025, scientists observed widespread bleaching, likening it to “wildfires underwater.” The loss of coral across the 2,300-kilometer (1,400-mile) ecosystem is particularly disheartening given its recent growth and recovery from previous bleaching events. However, the fast-growing corals that contributed to this recovery were found to be highly vulnerable and were among those most severely impacted by the 2024 event.

The report warned that continued bleaching could potentially push the Great Barrier Reef past a point of no return. Covering nearly 133,000 square miles (345,000 square kilometers), the reef is home to over 1,500 species of fish and 411 species of hard corals. It contributes billions of dollars annually to the Australian economy, primarily through tourism, and is renowned globally as one of the world’s greatest natural wonders.

However, its future is increasingly uncertain, with activists and scientists warning for over a decade about the reef’s vulnerability. The Great Barrier Reef has previously experienced severe mass bleaching in 1998, 2002, 2016, 2017, 2020, and 2022. Corals can recover from bleaching if temperatures return to normal, but they will perish if the water remains abnormally warm.

In early 2025, water temperatures once again spiked during Australia’s summer, reaching their peak in March and causing additional bleaching. The full impact of this event has yet to be measured and is not included in the current report.

Oceans now store 90% of the excess heat from global warming, with each of the last eight years setting a new record for the amount of heat stored in the ocean. The destruction of marine ecosystems could lead to the extinction of approximately one-quarter of all species that rely on reefs for survival, according to scientists. Additionally, reefs play a crucial role in protecting coastlines by mitigating the effects of floods, cyclones, and sea level rise.

Following the release of the report, the non-profit Queensland Conservation Council called the bleaching event a “call to action.” The council, representing dozens of environment groups in Queensland, urged state and national leaders to take action by reducing emissions and shutting down coal power stations. While Australia is transitioning to renewable energy like other developed nations, critics argue that this transition is not happening quickly enough.

The report concluded that the future coral reefs may look very different from those of the past, emphasizing the need for more research into reef adaptation and protection as the world continues to work towards reducing greenhouse gas emissions.