Australia is home to many iconic attractions such as the Daintree rainforest or the gold coast, but none are as well known as the great barrier reef. “The Great Barrier Reef is the world's most extensive coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometers over an area of approximately 344,400 square kilometers.” It is located right off the coast of Queensland, and it is dying.
Before and after of reef (before is on the right)
Scientists have recently discovered an never seen before depletion in coral on the reef, making the Australian government issue its highest response level. According to a study released Wednesday in the journal Nature, “baby coral in Australia's Great Barrier Reef has declined by 89% due to mass bleaching in 2016 and 2017.” “Bleaching occurs when corals are stressed by unusual environmental changes, such as increased sea temperature. They respond by getting rid of the symbiotic algae living in their tissue, causing the coral to turn white.” Without the algae, the coral loses its primary source of food which it can't survive without. Extensive coral bleaching during back-to-back summers was particularly lethal to the coral because it did not have enough time to fully recover before being hit again. The study measured the number of surviving adult corals in the Great Barrier Reef after the recent heat stress, as well as how many new corals it was able to make in 2018. Deadly bleaching events caused tremendous damage to the reefs ecosystem, and it is struggling to recover. Not only have ocean heat waves led to a big decrease in new coral, but also a change in the types of coral species being produced. Researchers looked at adult and baby coral from 47 locations in different years from 1996 to 2016 and then returned in 2018 to collect the same data. They found that “most of the northern region's coral has not been able to recover following mass bleaching events, leading to a decline in new coral as well.”
"Dead corals don't make babies," the study's lead author, Professor Terry Hughes, director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University, said in a press release.
According to the study, the biggest decline in regrowing came from the reef's most dominant species of adult coral, called Acropora, which supports thousands of other species. It had a 93% drop compared to previous years. Scientists say the change will likely reduce the diversity of the reef which will make it more susceptible to future bleaching. "Our study shows that reef resilience is now severely compromised by global warming," said co-author Professor Andrew Baird.
The United Nations Educational, Scientific and Cultural Organization put the Great Barrier Reef on its list of “World Heritage sites in 1981.” In recent years it has registered official "concern" about the reef's condition but stopped short of declaring it "in danger."
"There's only one way to fix this problem," said Hughes, "and that's to tackle the root cause of global heating by reducing net greenhouse gas emissions to zero as quickly as possible." We need to stop climate change to help great things like the reef.