The media is reporting that there is bleaching on the Great Barrier Reef. Bushfires, cyclones, floods, droughts, heatwaves, bleaching, locust plagues, starfish plagues – this is Australia. It has always happened.
The good news is that GBRMPA have refrained from sensationalism and should be congratulated for that. In their media comment, they point out that bleached coral is not dead and often recovers.
Time will tell how much coral is ultimately affected, but we can be certain that it will be exaggerated in many quarters of the scientific community and amplified further in the media.
Will they mention that the present aerial surveys can only see surface coral which are far more likely to bleach than the deeper corals that they cannot see. The calm sunny weather that usually precedes bleaching, means that the top few meters can get a few degrees hotter than the deeper water. Corals go down to over 50 m depth.
Will they mention that, in the supposedly catastrophic 2016 bleaching event, the deeper corals hardly bleached at all, and the total amount of coral that died was much less than 10 percent? Will they remind us that corals have remarkable capacity to recover – the amount of coral can double in 5 to 10 years, so losing a few percent from bleaching is not a big deal.
Will they mention that cyclones destroy far more coral than bleaching, and that the coral reefs are just a huge pile of dead coral that has been killed over thousands of years. Coral death is part of the life cycle on a reef.
Will they admit that they must have exaggerated the bleaching in 2016, 2017 and 2020 because the amount of coral on the reef has never been higher than in 2021 (see my previous posts)? How can so much coral have died due to bleaching when we have so much coral today on the GBR?
Also, it is false to imply that all of the 3000 individual reefs bleached in all those three years. Most of the reefs had some bleaching in just one of those years, a few had some bleaching in two of the years and almost none had bleaching in three years. And most of the corals on most of the reefs did not bleach at all.
They might also point out that routine surveys of bleaching events only started in 1998, so we have little data on their frequency – and should not make too many presumptions that they are becoming worse.
The scientists might mention that bleaching is a survival mechanism for coping with periodic hot water. Corals have evolved this over eons. Bleaching occurs when the small algae (zooxanthellae) that live in the coral polyp are expunged by the coral. Corals have the ability to select the species of zooxanthellae to adapt to hotter (or colder) conditions. Zooxanthellae of a myriad of different types float around in the water and are re-selected by the coral after bleaching. They will often select a strain of zooxanthellae that makes them less susceptible to beaching in the future.
Far from being highly susceptible to rising temperatures, anthropogenic or from natural causes, their ability to change zooxanthellae during bleaching is a remarkable mechanism of adaptation which makes them far better at coping with climate change than most other organisms.
Will science institutions point out that bleaching is a totally natural response, documented by the earliest scientists on the reef, and is not a new phenomenon?
Or will they preach the normal doom science that we have heard for the last half a century? Will they bully politicians, and scare the children into believing that the Great Barrier Reef is going to end?
Whatever level of bleaching that is occurring, the coral will recover as it has always done.
This is slightly edited version of a post that first appeared on Peter Ridd’s Facebook page, here.