The Great Barrier Reef has experienced its largest annual loss of hard coral cover in 39 years, with some areas experiencing a decline of over 70% in the past one year.

On August 6, 2025, the Australian Institute of Marine Science (AIMS) released its annual survey report, mentioning that the number of corals increased a lot after 2017. However, there was a significant loss mainly because of a mass bleaching event in 2024, exacerbated by Climate Change, cyclones and crown-of-thorns starfish outbreaks. According to the AIMS, the bleaching event, the fifth since 2016, had the largest spatial footprint ever recorded in the reef’s history.

Coral bleaching is characterised by corals turning pale or white. Bleached corals are not dead, but weaker and more vulnerable to disease. Coral bleaching happens when corals expel the symbiotic algae (zooxanthellae) living in their tissues, causing them to lose their vibrant colours. These algae are a primary food source and contribute to the coral’s colour. Scientists are of the opinion that corals are turning pale due to excessive temperatures. They believe that the Climate Change has a great impact on this UNESCO World Heritage Site.

Dr Mike Emslie, currently heading the long-term monitoring programme of the tropical marine research agency, stressed that the live coral cover measured in 2024 was the largest recorded in 39 years of surveys. Since then, a large part of the live corals has started turning pale. He claimed that the losses from such a high base of coral cover “cushioned the serious climate impacts on the world’s largest reef ecosystem which covers 344,000sqkm off the northeast Australian coast“. “These are substantial impacts and evidence that the increasing frequency of coral bleaching is really starting to have detrimental effects on the Great Barrier Reef,” added Dr Emslie. He told the press: “While there is still a lot of coral cover out there, these are record declines that we have seen in any one year of monitoring.“

The AIMS has divided the Great Barrier Reef, which extends 1,500km along the Queensland state coast, into three similarly-sized regions: Northern, Central and Southern. As per the report, living coral cover shrunk by almost a third in the south in a year, a quarter in the north and by 14% in the central region.

It is believed that record global heat in 2023-24 caused the coral bleaching. The bleaching event began in January 2023 and the concerned authorities in Australia declared a global crisis in April 2024. The Government of Australia started aerial surveys of 281 reefs across the Torres Strait and the entire northern Great Barrier Reef in March 2024, and found widespread coral bleaching. In a report, it mentioned that 78 of 281 reefs were bleached more than 30%. Meanwhile, the Coral Reef Watch of the US National Oceanic and Atmospheric Administration has confirmed that heat stress has hurt nearly 84% of the world’s coral reef area, including the Great Barrier Reef. So far, the heat stress has impacted at least 83 countries.

Although coral reefs often survive the mass global bleaching events, they become weaker. The UN Intergovernmental Panel on Climate Change mentioned in its 2018 report that coral reefs should be considered a “unique and threatened system” because of Climate Change as they became especially vulnerable to Global Warming beyond 1.5 degrees Celsius since pre-industrial era. It stated that the “tropical corals may be even more vulnerable to Climate Change than indicated in assessments made in 2014”. It may be noted that the world has warmed 1.3 degrees Celsius since pre-industrial times.

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Published by Koushik Das

Koushik Das (born on May 16, 1976 in Kolkata) is a career journalist. Based in the Indian capital of New Delhi, Koushik writes mainly about foreign policies and current geopolitical issues, and rarely about other topics. His own political ideas are highly influenced by Antonio Gramsci, Louis Althusser, Michel Foucault, Michael Oakeshott and others. English philosopher and political theorist Oakeshott (Dec 11, 1901-Dec 19, 1990) says that “in political activity, men sail a boundless and bottomless sea. There is neither harbour for shelter nor floor for anchorage, neither starting-place, nor appointed destination. But we have to keep afloat”. (Rationalism in Politics, 1962) As a student of Political Science, Koushik loves to share his views on issues, which have great impacts on his thought process (and also on India, South Asia and of course on the global community), with his readers through his website – Boundless Ocean of Politics. By doing so, he tries to keep himself afloat. You will find some of his articles in https://inserbia.info/today/ (https://inserbia.info/today/author/kou_das13_i/), as he has been trying to assess the global geopolitics since 2003. You can also mail him at kousdas@gmail.com View all posts by Koushik Das