Recent news of recovery in the Great Barrier Reef brings hope, but climate change-induced ocean warming is still causing massive bleaching of coral

“Greenpeace Wrong — The Great Barrier Reef Is Thriving!” reads the headline for an article posted by Dr. Jay Lehr and Tom Harris on the conservative website, “America Out Loud.” The article cites a recent report by the Australian Institute of Marine Science (AIMS), which says that some parts of the Great Barrier Reef are at their highest in 36 years. Indeed, this is very good news for the world’s largest coral ecosystem. The Institute said that coral in the Great Barrier Reef is resilient and has recovered from past disturbances. However, when factoring in the loss of coral since 2014, the increase measures a modest rise of 3%. The Great Barrier Reef has suffered four bleaching events since 2016. Rising global temperatures due to the buildup of greenhouse gasses in the Earth’s atmosphere continue to pose a threat to the reef, scientists say.  The report explicitly says, “These gains can be lost quickly with another large-scale disturbance that causes extensive mortality.” This can hardly be described as “doing exceptionally well.” Therefore, the claim that the GBR is “thriving” is mostly false.

Luisa Marcelinol, Research Assistant Professor of Civil and Environmental Engineering at Northwestern University explains…

It is very good news that the coral cover in most areas of the Great Barrier Reef (GBR) is increasing over the past couple of years (between 33 and 36% of hard coral cover over the north, central and south GBR) but since 2014 and due to intense heatwaves and a severe cyclone during 2014- 2017, GBR coral cover dropped to 10% (Northern GBR) to 25% (Southern GBR). In other words, the increased coral cover – albeit a positive trend – is dwarfed by the loss of coral cover over the bleaching events of the past 6 years. As an example, let me show what the numbers mean. Throughout the Northern GBR coral cover dropped down to 10% of its pre-bleaching baseline. Then it partially rebounded by 33-36%. This means that the coral cover went up from 10% to 13%, a net increase in only 3%.

A PNAS paper in 2012 by researchers at the Australian Institute of Marine Sciences (AIMS) who have been monitoring the GBR coral cover for the past few decades, described a tremendous loss of coral cover, from 28% to 14% between 1985 and 2012 because of severe tropical cyclones, coral bleaching episodes, and predation by crown-of-thorns starfish (COTS) outbreaks. The recent news of recovery in the GBR brings hope to conservation groups, park managers, scientists, and the public at large. It shows that because the last couple of years have been relatively mild regarding cyclones, heatwaves, and COTS outbreaks some coral species have been able to rebound, which speaks to the resilience of the reef. It remains to be seen if only some species have rebounded, and if there is loss of diversity, which may reduce future resilience, or if most species have rebounded. But we should not be dismissing the severe effect that climate change-induced ocean warming is bringing to coral reefs in the GBR and throughout the world; in the last 6 years, heatwaves have caused massive coral bleaching and unprecedented loss of coral cover throughout the tropics. Future projections of ocean warming assuming business-as-usual carbon dioxide emissions are expected to bring more intense and frequent heat waves and cyclones, which will lead to massive bleaching and death of corals every year and little to no time to recover from stress. If we do not take climate action, coral reefs will likely be lost.