Australia's coral reefs have declined for 40 years, mirroring global trend, new report finds

Coral cover on Australian reefs has declined over the past 40 years, mirroring a global trend. The Status of the World's Coral Reefs: 2025 report, from the Global Coral Reef Monitoring Network (GCRMN), finds global average hard coral cover in 2020-24 was 9.5% lower than in 1980-2009. The report is GCRMN's seventh, covering 10 regions, four of which declined. Climate change-driven heat stress has become a growing cause of coral loss over the past decade.

Dr. Manuel Gonzalez Rivero of AIMS (the institute whose scientists monitor Australia's coral reefs), who coordinates GCRMN globally, said coral cover rose a relative 6% between 2017 and 2019 after the third Global Coral Bleaching Event, but that gain was reversed by the fourth. Disturbances that once struck reefs about once a decade now recur every five to six years, cutting recovery time. Modelling suggests the decline will continue at the current rate; emissions cuts and local management could help, he said.

In Australia, coral cover fell from 30.2% in 1980-2009 to 26.8% in 2020-24, a 10.9% relative decline, said Dr. Mike Emslie of AIMS, who leads Great Barrier Reef monitoring. Scott Reef recovered after the 2016 bleaching event, while the Southern Great Barrier Reef and Pilbara saw major declines. Losses from the 2024 and 2025 mass bleaching events are not yet in the report.

AIMS coral scientist Dr. Emma Kennedy said cyclones and crown-of-thorns starfish outbreaks were once the main causes of decline, but mass bleaching has grown more prominent over the past decade. Great Barrier Reef coral cover has swung between very low and very high levels over the past 15 years, AIMS monitoring found.

Australia's reefs cover at least 43,000 square kilometres (16,600 square miles), two-thirds the size of Tasmania, the largest coral reef extent of any nation. Its three coral reef World Heritage Areas are the Great Barrier Reef, Ningaloo Coast and Lord Howe Island group; about 2 million Australians benefit from the reefs through tourism, fishing and science.