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According to Australia’s ABC News, the Great Barrier Reef is experiencing heat stress. The article at ABC News was written by distinguished professor Terry Hughes at James Cook University. It was originally published in The Conversation.
The ongoing overheating of the ocean has triggered an episode of mass coral bleaching for the fifth time in the past eight summers: 2016, 2017, 2020, 2022, and now 2024. These five recent events are joined by coral bleaching in 1998 and 2002, thus tallying seven such events in the past 26 years.
Coral bleaching on the Great Barrier Reef was infrequent and localized before 1998. Bleaching has increased in frequency, severity, and spatial scale during the past four decades. The cause, as you probably know, is anthropogenic climate change. Carbon dioxide emissions cause carbon dioxide to enter the ocean, thus acidifying the ocean, reducing carbon sequestration, and diminishing biological diversity.
The Great Barrier Reef is an enormous living organism. According to the article in ABC News, it consists of more than 3,000 individual coral reefs. It’s about the same size as Japan or Italy, extending along the coast for more than 2,300 km (more than 1,400 miles).
An article published in Earth.Org on 6 March 2024 addresses the issue of coral bleaching. Titled Record Ocean Temperatures Push Coral Reefs to Brink of Fourth Mass Bleaching Event, the article indicates that the entire Southern Hemisphere likely will experience coral bleaching this year. This information came from the US National Oceanic and Atmospheric Administration’s Coral Reef Watch. An ecologist affiliated with NOAA’s Coral Reef Watch said it was likely the entire Southern Hemisphere would experience bleaching this year.
The article at Earth.Org refers to a peer-reviewed paper in the renowned journal Science. Published 7 December 2023, the article in Science is titled Coral reefs in peril in a record-breaking year. The subhead: “Climate change and its impacts on coral reefs have reached uncharted territory.” The article in Science described unusual events in the upper ocean, including “unprecedented changes in conditions, ecosystems, and communities.” The Abstract indicates that “unprecedented mass coral bleaching and mortality will likely occur across the Indo-Pacific throughout 2024. These trends will worsen unless greenhouse gas (GHG) emissions decrease, with coral-dominated ecosystems likely to face substantial losses, leading to long-term damage to ecosystems and people across Earth’s tropical regions.”
According to a peer-reviewed paper in Global Change Biology, the damage from coral bleaching exceeds that caused by a severe cyclone. This peer-reviewed paper was published on 14 August 2021. Written by four scholars, it is titled The spatial footprint and patchiness of large-scale disturbances on coral reefs. The Abstract of the peer-reviewed paper includes the following information: “Ecosystems have always been shaped by disturbances, but many of these events are becoming larger, more severe and more frequent. The recovery capacity of depleted populations depends on the frequency of disturbances, the spatial distribution of mortality and the scale of dispersal. Here, we show that four mass coral bleaching events on the Great Barrier Reef (in 1998, 2002, 2016 and 2017) each had markedly larger disturbance footprints and were less patchy than a severe category 5 tropical cyclone (Cyclone Yasi, 2011). Severely bleached reefs in 2016 and 2017 were isolated from the nearest lightly affected reefs by up to 146 and 200 km, respectively. In contrast, reefs damaged by Cyclone Yasi were on average 20 km away from relatively undisturbed reefs, well within the estimated range of larval dispersal for most corals. …. Our findings illustrate that the spatial footprint of the recent mass bleaching events poses an unprecedented threat to the resilience of coral species in human history, a threat that is even larger than the amount of mortality suggests.”
The word unprecedented keeps coming up in the articles I read. Yes, we are in unprecedented times. However, let’s not confuse unprecedented with unexpected. After all, we’ve been collectively destroying a perfectly good planet for a long time.
Returning to the story in ABC News: “Three of the seven mass bleaching events so far on the Great Barrier Reef coincided with El Niño conditions (1998, 2016 and this summer), and the remaining four did not. Increasingly, climate-driven coral bleaching and death is happening regardless of whether we are in an El Niño or La Niña phase. Average tropical sea surface temperatures are already warmer today under La Niña conditions than they were during El Niño events only three or four decades ago.”
Well, that’s inconvenient. After all, coral reefs play an important role as carbon sinks. By capturing calcium carbonate, coral reefs sequester 70 to 90 million tonnes of carbon each year.
According to the article in ABC News, “The Great Barrier Reef is now a chequerboard of reefs with different recent histories of coral bleaching. Reefs that bleached in 2017 or 2016 have had only five or six years to recover before being hit again this summer – assuming they escaped bleaching during the 2020 and 2022 episodes.
Clearly, the gap between consecutive heat extremes is shrinking – we are vanishingly unlikely to see another 14-year reprieve like 2002 to 2016 again in our lifetimes, until global temperatures stabilise.”
Wait, what? Until global temperatures stabilize? You mean, never?
Ironically, the corals that are now prevalent on many reefs are young colonies of fast-growing, heat-sensitive species of branching and table-shaped corals – analogous to the rapid recovery of flammable grasses after a forest fire. These species can restore coral cover quickly, but they also make the Great Barrier Reef more vulnerable to future heatwaves.
Attempts to restore depleted coral cover through coral gardening, assisted migration (by harvesting larvae) and assisted evolution (rearing corals in an aquarium) are prohibitively expensive and unworkable at any meaningful scale. In Florida, coral nurseries suffered mass deaths due to record sea temperatures last summer.
The only long-term way to protect corals on the Great Barrier Reef and elsewhere is to rapidly reduce global greenhouse emissions.”
As you know, there is no ongoing attempt to reduce global greenhouse gas emissions at a relevant scale. Considering the aerosol masking effect and its importance is maintaining a relatively stable climate, I cannot imagine any of the world’s governments leading the effort to reduce greenhouse gas emissions.
If you are seeking yet another reason humans are headed for extinction in the near term, look no further than our collective behavior with respect to coral reefs. We have long known the importance of coral reefs in harboring biodiversity and sequestering carbon. As with most other phenomena that would require some sacrifice to address the problem, we cannot be bothered. Our self-absorption precludes making small sacrifices to preserve life on Earth. On the other hand, we’ll do almost anything for a few dollars more.
The Great Barrier Reef looks like it has been "Carpet Bombed."
https://www.theguardian.com/environment/2024/may/01/great-barrier-reef-coral-bleaching-crisis?fbclid=IwZXh0bgNhZW0CMTEAAR3qoLX_LrVkLDGTVbHJbpFtcSJxsP-Nd16uC-nqDbg9fsdfzU1tesFxVAs_aem_AcjNrpTA1T535ejZHhLiWAi2WnWw4uThQqEFb4O9bahqggoPxJ8aZn6b5BF7_pRhnw34U5DrAuZOTDWRfsAnz3M9
"Every single one of the sites we went to, the bleaching was unbelievably severe. It's the worst I've seen and I can't get my head around it."
https://www.canberratimes.com.au/story/8588873/scientists-despair-as-even-deep-corals-cook/?fbclid=IwAR27sT0JNi9ux2COkWqgza44oVl9gVW1cD0MNdzvLLrnU3Ux59VlbBJnPrA