Higher Temperatures Compromise Great Barrier Reef Regrowth
A recent study has found that the number of new corals in the Great Barrier Reef has fallen by 89 percent, as compared to historical levels. The study, which was published on April 3 in the journal Nature, examined the ecological effects of mass coral bleaching events that occurred due to increased ocean temperatures.
The Great Barrier Reef covers an area of 348,000 square kilometers off the northeast coast of Australia and was declared a UNESCO World Heritage Site in 1981. According to UNESCO, it contains the world’s largest collection of coral reefs, with approximately 400 types of coral, 1,500 species of fish, and 4,000 types of mollusc. It is also the habitat of endangered species such as the large green turtle, making it an important site for scientific analysis.
The Great Barrier Reef has suffered over four mass coral bleaching events in the last two decades, with back-to-back occurrences in 2016 and 2017. Coral bleaching occurs when increased sea temperatures cause the expulsion of algae from inside of the coral, turning the coral white. Algae serve as the main energy source for coral, and while the algae can recolonize if the water temperatures drop, the coral will eventually die if the water temperature remains high.
Coral bleaching has been directly linked to global warming, and according to Australia’s Minister for the Environment and Energy Josh Frydenberg, climate change is the “number one threat” to the Great Barrier Reef.
According to Terry Hughes, the study's lead author and director of the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University, “The replenishment ability of the reef has been diminished… Our study shows that [corals] are pretty much struggling to cope with rapid-fire bleaching events." In a press release, Hughes stated that the basic message of the study is simple: “dead corals don’t make babies.”
The group of scientists who worked on the report have said that they would expect coral reproduction to recover over the next decade, but only in the absence of another bleaching event, which seems improbable as sea temperature levels continue to rise. Study co-author Morgan Pratchett says that “it's highly unlikely that we could escape a fifth or sixth event in the coming decade. We used to think that the Great Barrier Reef was too big to fail -- until now.”
Andrew Baird, a Professorial Research Fellow at the ARC Centre of Excellence for Coral Reef Studies who also co-authored the study, told BBC, “We've gotten to the point now where local solutions for the reef are almost pointless - the only thing that matters is action on climate change.”