With AIMS’ reef surveys extending over more than 30 years, the AIMS Long-Term Monitoring Program provides an invaluable record of change in repeatedly surveyed coral reef communities over a large area of the Great Barrier Reef.
This annual summary update of trends in coral cover across the whole GBR is based on surveys of coral cover on the perimeters of reefs using manta tows. Detailed reports on the condition and trends of individual reefs are updated immediately after completion of each survey trip.
The dynamic nature of the GBR coral reefs, and the considerable variation between regions in the rates of decline and recovery of coral cover, are clearly apparent in the long-term record. For the annual updates, the GBR Marine Park is divided into three regions, each showing different trajectories of change in coral cover over time in response to the cumulative impacts of severe tropical cyclones, outbreaks of the crown-of-thorns starfish and coral bleaching.
Summary
- Coral cover on the Great Barrier Reef (GBR) has continued to decline due to the cumulative impacts of multiple, severe disturbances over the past four years, including coral bleaching, cyclones and crown-of-thorns starfish outbreaks.
- Reefs in all regions of the GBR (North, Central and South) were affected by different disturbances at different times.
- Trends in mean hard coral cover on reefs in all three regions now show a steep decline; this has not been observed in the historical record.
- This summary is based on manta tow surveys of coral reefs, mainly on the mid- and outer-shelf. The most recent surveys of 50 reefs were conducted from September 2017 to May 2018.
- The AIMS survey reefs in the Northern GBR have lost about half of their coral cover, reflecting the cumulative impacts of two severe cyclones and two episodes of severe coral bleaching over the period 2014 to 2017.
- Reefs in the Central GBR sustained significant coral loss due to coral bleaching and the continued southwards spread of the current wave of crown-of-thorns starfish outbreaks. Mean coral cover declined from 22% in 2016 to 14% in 2018.
- While some reefs in the Southern GBR continued to recover during the survey period, many of the southern Swain Reefs suffered intense crown-of-thorns starfish outbreaks. Mean coral cover on reefs in the Southern region declined for the first time in seven years, dropping from 33% in 2017 to 25% in 2018.
- Each reef is surveyed by AIMS every two years. Reef in the Northern region and in the Whitsunday area were not visited this year, which means that the impacts of Tropical Cyclone Debbie and coral bleaching in the Northern Region in 2017 are not yet fully represented in the results.
For more information: https://www.aims.gov.au/reef-monitoring/gbr-condition-summary-2017-2018
