Overall coral reef cover down by 9.5% in 2020-2024: Study

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. 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. 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.Hard coral cover averaged 30.2% across the 1980–2009 reference period and 27.3% across 2020–2024. (Representative file photo)“Hard coral cover averaged 30.2% across the 1980–2009 reference period and 27.3% across 2020–2024, a relative decline of 9.5%. Between 2023 and 2024 alone, the cover fell by a relative 8.9%, the largest single-year decline on record, resulting in a single-year estimate for coral cover of 25.8% for 2024. At this level of coral cover, many reef systems would still be expected to deliver key ecological services, including carbonate production, biodiversity, fisheries, coastal protection, and cultural value, though this is not the case across all regions,” said the report, after analysing 21.1 million observations, 87,299 surveys, representing 36,886 sites across 124 countries and territories.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. 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.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.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.“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. “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. 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.Also Read: Study identifies climate-resilient reefs worldwide, calls for better protection“Coral reefs once had decades to recover after major bleaching events. Today, they’re lucky to get five or six years,” Rivero added.Experts said the recovery matters because the benefits coral reefs provide extend far beyond the reef itself. 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.“Our economies depend on nature, and the continuing decline in coral cover revealed in this report must shake us out of our persistent inertia,” said David Obura, Chair of The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).“GCRMN’s long-term monitoring tracks not just the pulse of coral reefs, but of our planet too. It shows which regions are under the greatest pressure, that actions to date have not been sufficient, and warns where reefs will be under increasing threat in years to come. We must act now to halt this decline and invest in solutions that reduce pressures and build resilience, while sustaining the monitoring that turns good intentions into effective policy,” he added.