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Annual Summary Report of Coral Reef Condition 2024/25

Long-Term Monitoring Program
Annual Summary Report of Coral Reef Condition 2024/2025

Substantial impacts from 2024 mass coral bleaching and cyclones reduce regional coral cover to near long-term average

6th August 2025

 

Download the 2024/2025 report | 6.7MB

 

Infographic titled “AIMS Long-Term Monitoring Program Great Barrier Reef Annual Summary Report Coral Reef Condition 2024–2025.” It presents survey results from 124 reefs across the Northern, Central, and Southern Great Barrier Reef. A map shows reef survey locations from Cooktown to Rockhampton. Each region is summarised with data on hard coral cover (HCC), crown-of-thorns starfish (COTS) outbreaks, coral bleaching, and cyclone impacts.

 

Download the 2024/2025 report | 6.7MB

Executive summary

  • This report summarises the status (percentage of coral cover) of reefs in the Northern, Central and Southern Great Barrier Reef (GBR) following the 2024 mass coral bleaching event. Data were collected during manta surveys on 124 reefs by the Long-Term Monitoring Program (LTMP) between August 2024 and May 2025 (reported as ‘2025’). 
  • The 2024 mass coral bleaching event was the fifth mass coral bleaching event on the GBR since 2016 and was part of an ongoing (fourth) global event that began on Northern Hemisphere reefs in 2023 and was declared by the National Oceanic and Atmospheric Administration (NOAA) and the International Coral Reef Initiative (ICRI) in April 2024.  
  • The 2024 event had the largest spatial footprint ever recorded on the GBR, with high to extreme bleaching prevalence observed across all three regions of the GBR.  
  • To assess the impact of the 2024 bleaching event, targeted in-water surveys during and after peak bleaching were carried out in addition to LTMP manta tow surveys. Results from both sets of surveys indicate substantial coral mortality, and that decline in coral cover directly relates to coral bleaching severity and the prevalence of high to extreme coral bleaching (>30% coral cover bleached).  
  • Fast-growing Acropora corals, which facilitated the rapid recovery observed across many reefs between 2017 and 2024, were among the most severely impacted by the bleaching event. 
  • The summer of 2024 brought multiple stressors to the GBR including cyclones, flooding and crown-of-thorns starfish, but the mass coral bleaching event was the primary source of coral mortality.  
  • In 2025, hard coral cover declined substantially across the GBR, although considerable coral cover remains in all three regions. Regional declines ranged between 14% and 30% compared to 2024 levels, with some individual reefs experiencing coral declines of up to 70.8%. These declines are primarily attributed to coral mortality from the 2024 mass coral bleaching event, compounded by the cumulative impacts of two cyclones in December 2023 and January 2024, freshwater inundation and some crown-of-thorns starfish activity.  
  • In 2025, 48% of surveyed reefs underwent a decline in percentage coral cover, 42% showed no net change, and only 10% had an increase. Reefs with stable or increasing coral cover were predominantly located in the Central GBR.  
  • Of the 124 reefs surveyed, only two reefs had hard coral cover <10%. Most reefs (77) had coral cover between 10% and 30%, 33 reefs had cover between 30% and 50%, 10 reefs had coral cover between 50% and 75%, and the remaining two reefs had >75%. 
Line graph depicting coral cover percentage in the Northern Great Barrier Reef from 1985 to 2025. The y-axis ranges from 0% to 50%, and the x-axis spans the years. The blue line shows a general decline in coral cover until 2012, followed by a sharp increase after 2020. Shaded areas around the line indicate the range of uncertainty. In 2025, coral cover decreases to 30.0%, reflecting a drop from the previous peak.

 

 

  • On the Northern GBR, region-wide average hard coral cover decreased from 39.8% (34.8% – 44.2% credible intervals; CIs) in 2024 to 30.0% (26.6% – 33.8% CIs). This is a decline of 24.8% relative to 2024 levels and the largest annual decline recorded for this region since monitoring began. Despite this, coral cover remains above the long-term average of 26.6%. 
     
     
Line graph showing coral cover percentage in the Central Great Barrier Reef from 1985 to 2025. The y-axis ranges from 0% to 50%, and the x-axis spans the years. Coral cover shows pronounced fluctuations between 2010 and 2025, with peaks around 2016 and again in 2021–2022, followed by a slight decline to 28.6% in 2025. Shaded areas around the line indicate the range of uncertainty in the data.



 

  • In 2025 on the Central GBR, region-wide average hard coral cover decreased to 28.6% (25.5% – 31.7% CIs) from a regional high in 2024 (33.2% average; 29.7% – 37.1% CIs). This is a relative decline of 13.9%; however, it is still above the long-term average of 19.8%. 


 

Line graph showing coral cover percentage in the Southern Great Barrier Reef from 1985 to 2025. The y-axis ranges from 0% to 50%, and the x-axis spans the years. Coral cover shows a fluctuating trend. After a period of elevated cover around 2021, the graph shows a decline to 26.9% in 2025. Shaded areas around the line indicate the range of uncertainty in the data.

 

 

  • On the Southern GBR, region-wide average hard coral cover decreased to 26.9% (23.1% – 30.9% CIs) from 38.9% (33.9% – 44.0% CIs) in 2024. This represents a relative decline of 30.6% of 2024 levels, the largest region-wide annual decline yet recorded, which drove regional coral cover below the long-term average of 29.3%.  

 

 

  • Crown-of-thorns starfish (COTS) were detected on 27 surveyed reefs in 2025. One reef in the Southern GBR has a severe outbreak, while three additional reefs in the Southern GBR and two in the Northern GBR have established outbreaks. 
  • Above-average water temperatures (i.e. sea-surface temperature anomalies of +1°C to +2.5°C) occurred again on the GBR during the austral summer of 2025, peaking in March. As a result, the GBR experienced its sixth mass coral bleaching event since 2016. This current event was largely constrained to the Northern GBR and reefs across the north-west of Australia. LTMP 2025 surveys in the Northern GBR were completed in December 2024, prior to the onset of this coral bleaching event. Its impact on coral cover will be captured in next year’s report. 
  • Aerial bleaching surveys conducted in March 2025 focused on regions of the GBR that exceeded 4 Degree Heating Weeks, namely the Northern GBR and parts of the Central GBR north of Townsville. Of the 162 inshore and mid-shelf reefs surveyed, 41% had medium to high bleaching prevalence (11% – 60% coral cover bleached). Low to no bleaching was observed on 99% of the offshore reefs in the Northern GBR, and only 9% of the total 258 reefs surveyed had very high bleaching prevalence (>60% coral cover bleached).  
  • These results demonstrate that the GBR is under severe cumulative pressure and that coral cover gains in recent years were reversed over the 2024 summer. This reversal was anticipated last year, as many coral species are highly vulnerable to elevated heat stress, wave damage and crown-of-thorns starfish predation, all of which continue to impact the GBR.  
  • Coral bleaching levels and mortality during this ongoing global event have been more severe in other parts of the world, such as the Caribbean, where mortality was high on almost all reefs and very little coral currently remains. The GBR had record high coral cover before the event and fared relatively better because of the level of coral cover prior to the event, its size, the variety of interconnected habitats, and the range of heat stress levels experienced by different regions. 
  • The GBR currently retains higher coral cover than many reefs globally; however, mass coral bleaching events are now occurring with increasing frequency, while recovery periods are decreasing both at the scale of individual reef systems like the GBR and at the scale of reefs globally.

Download the 2024/2025 report | 6.7MB

 

Dr Daniela Ceccarelli and Dr Mike Emslie on the 2024/2025 LTMP surveys
A graphic showing that the monitoring program in 2025 surveyed 124 reefs, performed 5270 tows covering a distance of 1054km over 126 days at sea

 

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