Key results
This report summarises the condition of coral reefs of the Great Barrier Reef (GBR) from the Long-Term Monitoring Program (LTMP) surveys of 127 reefs conducted between August 2020 and April 2021 (reported as ‘2021’).
Over the 35 years of monitoring by AIMS, the reefs of the GBR have shown an ability to recover after disturbances.
In 2021, widespread recovery was underway, largely due to increases in fast growing Acropora corals.
Survey reefs experienced low levels of acute stressors over the past 12 months with no prolonged high temperatures or major cyclones. Numbers of outbreaks of crown-of-thorns starfish on survey reefs have generally decreased; however, there remain ongoing outbreaks on some reefs in the Southern GBR.
Overall, 59 out of 127 reefs had moderate (>10% - 30%) hard coral cover and 36 reefs had high (>30% - 50%) hard coral cover.
On the Northern GBR, region-wide hard coral cover was moderate and had continued to increase to 27% from the most recent low point in 2017.
On the Central GBR region-wide hard coral cover was moderate and had increased to 26% in 2021.
Region-wide hard coral cover on reefs in the Southern GBR was high and had increased to 39% in 2021.
In 2020, most of the surveyed reefs experienced heat stress accumulation that produced widespread coral bleaching but was below thresholds where widespread mortality is expected to occur. Consistent with this, surveys in 2021 recorded low coral mortality from the 2020 bleaching event.
In periods free from acute disturbances, most GBR coral reefs demonstrate resilience through the ability to begin recovery. However, the reefs of the GBR continue to be exposed to cumulative stressors, and the prognosis for the future disturbance regime is one of increased and longer lasting marine heatwaves and a greater proportion of severe tropical cyclones.
https://www.aims.gov.au/reef-monitoring ... -2020-2021