CANBERRA, Australia (AP) – More than 90% of the corals of the Great Barrier Reef studied this year were bleached in the fourth such event in seven years in the world’s largest coral reef ecosystem, Australian government scientists said.
Bleaching is caused by global warming, but this is the first discoloration of the reef during La Niña weather, which is due to lower Pacific temperatures, the Great Barrier Reef report said in its annual report, published late Tuesday, which found 91% affected surveyed areas.
Bleaching in 2016, 2017 and 2020 damaged two-thirds of the corals on the famous reef off the east coast of Australia.
Coral is bleached as a response to heat stress, and scientists hope most of the coral will recover from the current event, said David Wachenfeld, chief scientist of the management that manages the reef ecosystem.
“The first signs that the death rate will not be very high,” Wachenfeld said on Wednesday.
“We hope to see that most of the bleached corals are recovering, and eventually we will have an event more like 2020, when, yes, there was massive bleaching but there was low mortality,” Wachenfeld added.
Bleaching events in 2016 and 2017 led to “fairly high coral mortality rates,” Wachenfeld said.
Simon Bradshaw, a researcher at the Climate Council, an Australian group that monitors climate change, said the report shows that reef survival depends on dramatic global emission reductions over a decade.
“It’s heartbreaking. It’s very exciting, “said Bradshaw.” It shows that our Barrier Reef is really in very serious trouble. “
Last December, the first month of summer in the southern hemisphere, was the hottest December the reef has experienced since 1900. The “sea heat” entered in late February, the report said.
A United Nations delegation visited the reef in March to assess whether to downgrade the reef to the World Heritage List due to devastating climate change.
Last July, Australia received sufficient international support to postpone an attempt by UNESCO, the UN’s cultural organization, to downgrade the reef’s World Heritage status to “endangered” due to the damage caused by climate change.
But the issue will again be on the agenda of the World Heritage Committee at its next annual meeting.
The Great Barrier Reef makes up about 10% of the world’s coral reef ecosystems and got its name because of the great danger it created for 18th century sailors. The network of more than 2,500 reefs covers 348,000 square kilometers (134,000 square miles).
Coral consists of tiny animals called polyps that feed on microscopic algae that live inside reefs and are sensitive to changes in water temperature.
Algae provide reefs with their kaleidoscope of colors and produce sugar through photosynthesis, which provides corals with most of their nutrients.
Rising ocean temperatures turn algae-producing chemicals into toxins. Coral turns white as it effectively spits out poisonous algae.
Heat stress for several weeks can lead to the death of corals from starvation.
The latest bleaching is an unwanted reminder of the differences in climate change policy among Australian politicians.
The Conservative government, which is seeking re-election on May 21, has less ambitious emission reduction targets than the center-left opposition has promised.
Prime Minister Scott Morrison’s Liberal Party aims to reduce emissions in Australia by 26% to 28% below 2005 levels by 2030.
The opposition Labor Party has promised to cut emissions by 43% by the end of the decade.
At the UN climate conference last November, Morrison was widely criticized for failing to set a more ambitious goal.
Greenpeace Australia Pacific said in a statement that the scale of the latest bleaching was “another accusation by the Morrison government that failed to protect the reef and exacerbated the problem by supporting fossil fuels.”