Canberra, Australia - The Great Barrier Reef Marine Authority said in its annual report released late Tuesday that more than 91% of Great Barrier Reef coral surveyed this year was bleached. This is the fourth such mass event in seven years in the world’s largest coral reef ecosystem, Australian government scientists said.
Bleaching, a heat stress response, is caused by global warming, but this is the reef’s first bleaching event during a La Niña weather pattern, which is associated with cooler Pacific Ocean temperatures and the main driver behind the wet weather across Australia during what is autumn in the southern hemisphere.
Coral reefs provide an important ecosystem for life underwater, protect coastal areas by reducing the power of waves hitting the coast, and provide a crucial source of income for millions of people.
When corals are stressed by marine warm waters, they will expel their algal partner in a process called coral bleaching. The corals turn a stark white, and if stressed for too long, they will die.
Bleaching in 2016, 2017 led to “quite high levels of coral mortality. Coupled with the response in 2020, it has damaged two-thirds of the coral in the famed reef off Australia’s eastern coast.
Simon Bradshaw, a researcher at the Climate Council, an Australia-based group that tracks climate change, said the report demonstrated the reef’s survival depended on steep global emission cuts within the decade.
Last December, the first month of the Southern Hemisphere summer, was the hottest December the reef had experienced since 1900.
The latest bleaching is an unwelcome reminder of the differences in climate change policy among Australian politicians.
The conservative government seeking reelection on May 21 has less ambitious emission reduction targets than the center-left opposition is promising.
Prime Minister Scott Morrison’s Liberal Party aims to reduce Australia’s emissions by 26% to 28% below 2005 levels by 2030.
The opposition Labor Party has promised to reduce emissions by 43% by the end of the decade.
Morrison was widely criticized at the U.N. climate conference last November for failing to set a more ambitious target.
-AP