Great Barrier Reef Has Lost Half Its Corals

Misbar's investigation found that the claims on social media are true. In a study published in the Proceedings of the Royal Society Journal, researchers documented major shifts in the colony size structure of coral populations along the length of the Great Barrier Reef relative to 1995/1996 baselines. 

The Great Barrier Reef contains the world’s largest collection of coral reefs, with 400 types of coral, 1,500 species of fish and 4,000 types of mollusc. It also holds great scientific interest as the home of species threatened with extinction according to the United Nations Educational, Scientific, and Cultural Organization. 

From the recently released study, it appears larger species, such as branching and table-shaped corals, have been affected hardest — almost disappearing from the far northern reaches of the reef. In a statement given by study co-author Terry Hughes, reported in CBS News, "They're typically depleted by (up to) 80 or 90 percent compared to 25 years ago." Professor Hughes explained in the Sydney Morning Herald, “The loss of big corals is important because they make all the babies - they’re responsible for a huge proportion of the breeding that’s done every year by adult corals.” The authors reported in their study that in addition to losing larger species, coral colony abundances on reef crests and slopes have declined sharply across all colony size classes and in all coral taxa compared to historical baselines.

Corals rely on algae to provide the bulk of their energy and much of their vibrant colour. When exposed to sustained abnormal heat - measured in so-called degree-heating days - corals begin to expel the algae, leading to mass bleaching. The Sydney Morning Herald reported the southern part of the reef was exposed to record-breaking temperatures and extensive bleaching in early 2020. The authors of the study warn: “There is no time to lose - we must sharply decrease greenhouse gas emissions ASAP.” 

Researchers have documented that half of the Great Barrier Reef’s corals have died over the last 25 years.