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Great Barrier Reef Coral Reef Condition Report 2023–2024 Summary

Acknowledgments

  • AIMS acknowledges the Traditional Owners of the land and sea Countries.

  • Pays respects to their elders: past, present, and emerging.

  • Recognizes Aboriginal and Torres Strait Islander peoples as Australia’s first scientists.

Summary of the Report

  • The report details the condition of coral reefs across Northern, Central, and Southern Great Barrier Reef (GBR).

  • Surveys conducted from August 2023 to June 2024 by the Long-Term Monitoring Program (LTMP).

  • Total of 94 reefs surveyed.

History of Coral Monitoring

  • 38 years of monitoring by AIMS has shown cyclical patterns of hard coral cover responses to disturbances.

  • Percent hard coral cover: a standard measure of reef health used globally; reflects abundance of hard corals which are critical for reef ecosystems.

Coral Cover and Disturbances

  • Above-average sea temperatures caused the fifth mass coral bleaching event in March 2024.

  • Bleaching considered part of a global event, as declared by NOAA and ICRI.

  • Impacted by two tropical cyclones:

    • Cyclone Jasper (Category 5 in Coral Sea).

    • Cyclone Kirrily (Category 3).

  • Crown-of-thorns starfish (COTS) outbreaks noted in specific GBR regions.

Coral Survey Findings

  • 2024 coral cover results:

    • Increased hard coral cover across GBR regions but full impact of disturbances is not fully assessed yet.

    • Many surveys conducted before peak heat stress and cyclone impacts.

  • Survey summary by region:

    • Northern GBR: Average hard coral cover increased to 39.5%.

    • Central GBR: Average hard coral cover increased to 34.0%.

    • Southern GBR: Average hard coral cover increased to 39.1%.

Specific Reef Conditions

  • Of the 94 reefs surveyed:

    • 2 reefs had cover <10%; 36 between 10-30%; 35 between 30-50%; 21 between 50-75%.

  • Importance of understanding changes in coral cover in response to disturbances to predict recovery.

Research Methods

  • Manta tow surveys are the primary method for estimating coral cover (visual estimates over large areas).

  • Data reliability assessed with 95% credible intervals, indicating uncertainty in estimations.

  • Continuous improvement in data analysis and monitoring methods, utilizing statistical advancements.

Impacts of Climate Change

  • 2024 mass coral bleaching event highlighted the impact of heat stress; unprecedented heat levels recorded.

  • Aerial and in-water surveys confirmed high prevalence and severity of bleaching across GBR.

  • Significant portions of reefs exhibited varying levels of bleaching, with some experiencing extreme bleaching.

Future Projections

  • Future disturbances are expected to escalate due to climate change.

  • Necessary strategies include:

    • Reducing global greenhouse emissions.

    • Local management practices to mitigate pressures on reefs.

    • Research focus on reef recovery processes.

  • Cumulative stressors like increasing ocean temperatures and crown-of-thorns starfish will affect recovery and health of coral reefs.

Conclusion

  • Understanding long-term trends is critical to assess reef health.

  • Ongoing monitoring and improved management strategies are essential to protect and restore the GBR.

Contacts

For more information, contact Dr. Mike Emslie at aims.gov.au.