The world’s coral reefs are running out of time to recover between increasingly frequent marine heatwaves and global bleaching events, driven by human-induced climate change, a new global study – the ‘Status of Coral Reefs of the World: 2025’ said on Monday. Overall, a 9.5% relative decline in hard coral cover has been observed when comparing modern averages (2020–2024) with the reference period (1980–2009), it said.
Released by the Global Coral Reef Monitoring Network (GCRMN), the report which looked at more than 40 years of global data, said every major global bleaching event since 1998 has driven a sharp decline in global hard coral cover, creating a “staircase of decline” as recovery windows shrink.
Global hard coral cover is measured in percentages to show what portion of the ocean floor’s hard substrate is actively covered by living hard coral tissue. “Climate change is driving more frequent and severe marine heatwaves, but local pressures such as poor water quality, overfishing and coastal development are making reefs even less able to withstand them. So we have to do two things at once: reduce emissions at the global level and implement science-based conservation measures at the local level. The study further adds while recovery is still possible after a bleaching event, the window for recovery is shrinking.
Because the benefits coral reefs provide extend far beyond the reef itself, experts said the recovery matters. Interestingly, the western Indian Ocean recorded the largest recovery in hard coral cover, going up by 31% in the 2020-2024 window, in comparison to the 1980-2009 period. This was followed by an increase in hard coral cover by 16.2% in south Asia. The biggest decline was recorded in the ROPME sea area (-48.7%), followed by -43.3% in the Caribbean and -18.3% across the Pacific region. Recovery intervals have shrunk from approximately 10 years to 5–6 years in many regions, with no return to reference-period cover at any point since 2010, it noted. There was a 6% relative recovery in global hard coral cover following the third global bleaching event, it adds. Even though coral reefs cover less than 0.2% of the ocean floor, they support at least 25% of all marine species and underpin food security, livelihoods, coastal protection, tourism and cultural heritage of close to one billion people worldwide.
“After decades of studying coral reefs, what concerns me most isn’t the current loss of hard coral cover; it’s that we’re steadily eroding the conditions they need to recover,” said Manuel González Rivero, lead author of the report.
During the first global coral bleaching event between 1998 and 1999), there was a roughly 6.5% decline in hard coral cover . The second global coral bleaching event (2010–2011) led to a rough 9.9% decline; the third global coral bleaching event (2016–2017) led to a 6.6% decline and the latest and fourth global coral bleaching event (2023–2024) has led to a 8.9% decline, the study says.
The study flagged four major global coral bleaching events in total, each of which led to a substantial drop in hard coral cover, with the reefs only partially recovering before the next marine heatwave strikes.
