Coral bleaching at the Great Barrier Reef in 2016 (Credit: Getty Images)

The Great Barrier Reef is in a ruinous state due to warming sea levels caused by global warming, which in turn led to five mass coral bleaching events, three of which occurred in the last five years. Scientists say nearly the entire coral reef system has been bleached, and only 2% of it has been spared.

The first mass bleaching occurred in 1998, and over 20 years later, a study published on Friday found that only 1.7% of individual reefs had survived bleaching.

The first bleaching event took place during the 1998 ENSO, and four years later, the second one occurred. Following a 14-year hiatus, three events of the such came back to back, ravaging the ecosystem throughout 2016, 2017, and 2020.

Sattelite imagery shows that both the intensity of thermal stress and the areal coverage have increased from one event to the next.

The scientists behind the study asserted that their results are only indicative "rather than precise estimates of larval supply loss." However, there being a diversity of local impacts is crucial for targeting reef management, the study said.

Reef experts hope areas that have suffered less under global warming will act as a 'refuge' for corals and enable them to survive, which will see them dispersing their larvae onto bleached reefs.

According to the study, an obstacle to that natural process could be that areas that could have previously served as 'refuges' had already experienced bleaching at least once. However, continued analysis of future events would help resolve which candidate areas would warm less than expected, therefore aiding their sustainability.

The Current Biology research also underscored that bleaching events must be seen as a series of ailments rather than solo disasters in order to determine their process of recovery over time.

What is coral bleaching?

Coral bleaching is when the delicate corals are damaged due to warming water temperatures, which causes them to lose their unique colors, rendering them white. The white color is by the corals themselves expelling the algae living in their tissues.

Bleaching does not kill the corals; however, it does subject them to more stress, which could lead to their death. And although they could recover, extended periods of warming could jeopardize that and subject them to mortality as well.

What are coral reefs?

Coral reefs are biodiversity hubs that house fish, protect coastal communities, and generate billions of dollars for fisheries and tourism.

Action being taken

The Australian government had lobbied against a UN recommendation to include the Great Barrier Reef on its "in danger" sites list. Canberra said although climate change is the biggest threat to the reef, the appropriate means to tackle the bleaching was the COP.

Australia has since refused to set stronger climate goals for 2030 - a date by which the UN wants the entire world to halve its carbon emissions. Morrison's government has cited "promoting growth in new technologies" as the crutch that would help the Oceanian country, which is a major exporter of iron ore, coal, and petroleum, reach net zero emissions by 2050.