SYDNEY – The Great Barrier Reef, which stretches 2,300 kilometers off the northeast coast of Australia, has lost more than half of its corals since 1995 as a result of ocean warming due to climate change, according to a study published on Wednesday.
The decline in corals (small, medium and large) occurred in both shallow and deep waters throughout the Great Barrier Reef, which is home to 400 types of coral, 1,500 species of fish and 4,000 varieties of mollusks.
Branching and table-shaped corals, which make up structures important for fish and other species that inhabit the reefs, are the most affected according to the study that measured the size of the coral colonies in this area declared a World Heritage Site.
Study co-author Terry Hughes, an expert at the ARC Center of Excellence for Coral Reef Studies (CoralCoE), said in a statement from the institution that the aforementioned types of coral were “the worst affected by record-breaking temperatures that triggered mass bleaching in 2016 and 2017.”
After the two consecutive coral bleaching events that mainly damaged the northern and central areas of the reef, which with its 344,400 square kilometers is the largest in the world, another at the beginning of the year affected the southern sector of the reef system to a greater extent.
The main cause of this phenomenon is an increase in sea temperature, which causes the corals to expel zooxanthallae, microscopic algae living in their tissues that produce oxygen and provide them with food resulting from photosynthesis. This causes the coral to turn white, and although they do not necessarily die, they are under more stress and more susceptible to disease and death.
In total, the Great Barrier Reef has been affected by five mass bleaching events caused by global warming between 1998-2017, in addition to another two caused by the influx of fresh water, according to the Australian Institute of Marine Sciences.
“We used to think the Great Barrier Reef is protected by its sheer size – but our results show that even the world’s largest and relatively well-protected reef system is increasingly compromised and in decline,” Hughes said.
Andy Dietzel, from CoralCoE at James Cook University and lead author of the study published on Wednesday in the scientific journal “Proceedings of the Royal Society B,” advocated an increase in studies of corals to understand their changes.
“Our results show the ability of the Great Barrier Reef to recover – its resilience – is compromised compared to the past, because there are fewer babies, and fewer large breeding adults,” Dietzel warned, calling for greater action against climate change.
The Great Barrier Reef Marine Park Authority of Australia, the government of which promotes coal and gas as cornerstones of its economy, last year downgraded the health status of this ecosystem from “poor” to “very poor,” noting that goals to improve water quality of the government plan, which runs until 2050, have not been met.