Corals in the Great Barrier Reef are disappearing. They have more than halved in the last 25 years, according to a new study that has led scientists to warn, once again, that this reef, the largest living species on Earth and that it is visible from space , it will become unrecognizable if we do not drastically reduce greenhouse gas emissions. There will be no going back and we will lose the one that was designated a World Heritage Site in 1981 by UNESCO.
A team of researchers from the ARC Center of Excellence for Coral Reef Studies based in Townsville, Australia, assessed coral communities and size between 1995 and 2017 and found that the number of small, medium and large corals had fallen by more than 50%, especially in the latter, a really worrying finding.
Terry Hughes, a co-author of the paper and a James Cook University professor, concluded that mass bleaching events triggered by record water temperatures between 2016 and 2017 had the most significant impact on coral depletion in these nearly three decades. Bleaching occurs when corals under stress shed algae, known as zooxanthellae, which give them color.
Acidification and warming of the oceans
The analysis was carried out in the 2,300 kilometers long of the Great Barrier Reef, discovering a disturbing loss at almost every level:
“A vibrant coral population has millions of tiny baby corals, as well as many large, large mums that produce the most larvae,” explains Andy Dietzel of the ARC Center of Excellence for Coral Reef Studies. “Our results show that the resilience of the Great Barrier Reef is compromised compared to the past, because there are fewer suckers and fewer large breeding adults.”
The loss of the largest and therefore oldest corals could have a cascading effect on the entire reef system , as the largest colonies in a population disproportionately impact the next generation’s reproduction and genes , apart from offering a greater habitat and food for fish and other forms of life on the reef (remember that it is home to dolphins, turtles, sharks, stars, sea, mollusks …)
“The global decline in large and old corals implies a loss of critical habitat, food, and carbon storage,” the authors write. “We used to think that the Great Barrier Reef was protected because of its large size, but our results show that even the largest and relatively well-protected reef system in the world is increasingly compromised and in decline, ” they argue.
Could the Great Barrier Reef recover?
Yes, but only if conditions return to normal , something that can take several decades. And we have to bear in mind that we live in a world that is constantly warming by our actions, so any climate action we carry out will take time to see its fruits. It may be too late to get a full recovery of the corals by that time.
Global temperatures have already risen by around 1 ° C since pre-industrial times. The UN has warned that if that increase reaches 1.5 ° C, 90% of the world’s corals will disappear forever.
” There is no time to lose , we must drastically reduce greenhouse gas emissions as soon as possible,” the scientists conclude.
Referencia: Andreas Dietzel et al, Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef, Proceedings of the Royal Society B: Biological Sciences (2020). DOI: 10.1098/rspb.2020.1432
