Global coral reef coverage falls to 25.8 percent as heatwaves shrink recovery time: report

Global coral reef coverage has declined by 9.5 percent compared with the 1980–2009 average, according to a report published Monday by the Global Coral Reef Monitoring Network. The assessment, based on more than 21 million observations from 36,886 reef sites across 124 countries and territories, found hard coral coverage fell from just over 30 percent during 2009–2020 to 25.8 percent in 2024 .

The report attributes the decline primarily to climate-driven heat stress, which triggers coral bleaching. Bleaching occurs when abnormally warm sea temperatures cause corals to expel the algae living in their tissue, turning white and entering a weakened state. If heat persists, the corals die. Four global bleaching events since 1998—1998/99, 2010/11, 2016/17, and 2023/24—each resulted in significant hard coral losses of 6.5 percent, 9.9 percent, 6.6 percent, and 8.9 percent, respectively .

Manuel González Rivero, the report’s lead author and a researcher at the Australian Institute of Marine Science, said recovery periods between bleaching events have shrunk from decades to as little as five or six years. “This creates a downward spiral that becomes harder to reverse with each new bleaching event,” González Rivero said .

The report noted that coral reefs cover less than 0.2 percent of the ocean floor but support at least a quarter of all marine species. They also provide critical benefits for food security, income, coastal protection, and tourism. The Global Coral Reef Monitoring Network, a worldwide collaboration of scientists and conservationists, has collected data on reef health since 1995 .

Between 2017 and 2019, global hard coral coverage increased by about 6 percent, demonstrating that reefs can recover if given sufficient time between heatwaves. However, the report warns that the accelerating frequency of marine heatwaves now leaves insufficient recovery windows .