In a December 2, 2021 Facebook post, marine physicist Peter Ridd claimed the natural wonder did not need help because all three major regions of the reef “never had more coral on them” despite a series of bleaching events.
However, his claim of record coral cover is not supported by long-term monitoring data, which shows recent levels are high but still short of all-time peaks.
Dr Ridd was dismissed from his role as professor of marine physics at James Cook University in 2018 following public comments questioning evidence of harm to the reef. The dismissal was upheld after a long-running legal battle that went to the High Court.
When contacted by AAP FactCheck, Dr Ridd said his claim was based on AIMS long-term monitoring data on coral cover at three sections of the reef.
He said in an email that it was “absolutely beyond doubt” there had never been more coral on the reef since records began, adding that his post was referring to all three regions purportedly being at their highest-ever levels of coral cover on individual bases once uncertainty margins were taken into account.
AIMS, a Commonwealth statutory authority, claims its survey is the most comprehensive available record on the reef’s condition. Its latest annual report of the findings, for 2020-2021, notes that the metric of hard coral cover – which gauges the proportion of the seafloor covered in live, hard coral – was a “simple and robust measure of reef health” although it also “reveals nothing about the diversity or composition of coral assemblages”.
The report identified that recovery had been underway across much of the reef in the last few years and 2021 was a “low disturbance year” without prolonged periods of heat stress or any cyclones of note and fewer crown-of-thorns starfish outbreaks than in previous years.
However, it also said that the northern and southern reef sections were “still below the highest recorded coral cover in the 1980s, and preliminary analyses have documented shifts in the dominant corals on some reefs”.
An AIMS spokeswoman told AAP FactCheck in an email that coral coverage on each of the three main reef regions was “close to historical highs”, but none were at their highest-ever levels since monitoring began in 1985.
The latest report said average hard coral cover had increased in all three regions compared to the previous year, to 27 per cent in the northern reef, 26 per cent in the central reef and 39 per cent in the southern reef.
Average coral cover for the central reef peaked at 28.7 per cent in 2016, the only time it was higher than the 2021 figure (see figure 4). Cover for the southern reef peaked at 42.5 per cent in 1988, one of three times it was previously higher than in 2021.
On Dr Ridd’s suggestion that coral cover was at highest-ever levels once uncertainty margins were taken into account, the AIMS spokeswoman said the data did not support this statement.
“At best, there may be an argument that it is not statistically different to the highest levels recorded, but there is little evidence to support that it is the highest it’s ever been. If anything, it is more likely that hard coral cover was lower in 2021 compared to its highest levels,” she said.
For example, the 2021 data shows the true average coral cover for the northern reef could be as low as 24.2 per cent or as high as 30.4 per cent based on the 95 per confidence interval for the data. For 1988, the 95 per cent confidence interval range is 28 per cent to 36.2 per cent cover.
The AIMS spokeswoman said coral recovery was expected during periods of low disturbances such as the most recent reporting period, however only one severe event could turn this around – and the recovery intervals for such disturbances were getting shorter.
Australian Research Council Centre of Excellence for Coral Reef Studies director Terry Hughes said coral recovery after bleaching events was analogous to fire on land, “where flammable grasses recover faster than trees”.
“A localised and patchy increase in coral cover in-between recurrent bleaching events is entirely expected,” he told AAP FactCheck in an email.
“But a temporary recovery is often driven by fast-growing branching corals that are the most vulnerable species to the inevitable next spike in sea temperatures.”
The AIMS report noted that the majority of recent reef recovery was driven by increases in fast-growing acropora corals, which rapidly increased hard coral cover but were less dense than slower-growing corals and were highly susceptible to damage from storms, bleaching or crown-of-thorns starfish.
AAP FactCheck previously debunked a claim from Dr Ridd that coral cover on the Great Barrier Reef had barely changed since the 1980s.
Long-term monitoring data of the Great Barrier Reef shows average coral cover reached near-historical highs in the reef’s three major regions in the most recent reporting period, however none had record amounts of coral as claimed by Dr Ridd.
Mostly False – The claim is mostly inaccurate but includes minor elements of truth.
First published: January 25, 2022
Editor’s note: AAP FactCheck has expanded its ability to fact-check environmental issues with the support of the Australian Conservation Foundation. AAP FactCheck retains full editorial independence in this project and continues to apply the rigorous standards required for accredited members of the International Fact-Checking Network.