The Great Barrier Reef has lost half its corals within 3 decades

[Eugene]

Source: CNN

The Great Barrier Reef has lost half its corals within 3 decades

Amy Woodyatt, CNN • Published 13th October 2020

(CNN) — Australia's Great Barrier Reef has lost 50% of its coral populations in the last three decades, with climate change a key driver of reef disturbance, a new study has found.

Researchers from the ARC Centre of Excellence for Coral Reef Studies, in Queensland, northeastern Australia, assessed coral communities and their colony size along the length of the Great Barrier Reef between 1995 and 2017, finding depletion of virtually all coral populations, they said Tuesday.

Coral reefs are some of the most vibrant marine ecosystems on the planet -- between a quarter and one third of all marine species rely on them at some point in their life cycle.

The Great Barrier Reef, the world's largest coral reef, covers nearly 133,000 square miles and is home to more than 1,500 species of fish, 411 species of hard corals and dozens of other species.

"We found the number of small, medium and large corals on the Great Barrier Reef has declined by more than 50% since the 1990s," reported co-author Terry Hughes, a distinguished professor at the ARC Centre of Excellence for Coral Reef Studies, in a statement.

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Read more: https://edition.cnn.com/travel/article/great-barrier-reef-coral-loss-intl-scli-climate-scn/index.html

[hatrack]

1. From WP Coverage Of Same Story: "I Know The Reef Is Dead. It Just Doesn't Know It Yet."

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“The decline occurred in both shallow and deeper water, and across virtually all species — but especially in branching and table-shaped corals,” Terry Hughes, a professor at the ARC Center of Excellence for Coral Reef Studies in Queensland and a co-author of the research paper, said in a statement Tuesday. “These were the worst affected by record breaking temperatures that triggered mass bleaching in 2016 and 2017.”

On some areas of the northern half of the reef, “the abundance of large colonies on the crest dropped” by up to 98 percent, according to the study, published in the journal Proceedings of the Royal Society B. By contrast, there was a slight increase on the southern slope, about 25 percent. It’s a clear sign of rapid decline.

“We expect this decline to continue” because of warming caused by humans, Hughes said. “The only effective way to improve the outcome for coral reefs is global action on greenhouse gasses. If global temperatures rise to 3 or 4 [degrees Celsius], the reef will be unrecognizable, so there is no time to lose.” “We have evidence from some parts of the reef that recruitment rates are only recovering very slowly … and are nowhere near levels prior to the bleaching events,” Andreas Dietzel, another professor at the ARC Center and a co-author of the paper, said in an email.

EDIT

Bob Richmond, a research professor and director of the Kewalo Marine Laboratory at the University of Hawaii at Manoa, called the study “a really excellent piece of work,” with the most comprehensive research on Great Barrier Reef coral populations that he’s seen. “What they’re showing is these demographic changes are occurring on a regional scale … on reef slopes that make it difficult for coral reefs to persist over time,” Richmond said. In his long experience of visiting and researching reefs around the world, “if I don’t see one-year-old, two-year-old, three-year-old corals, I know that reef is dead. It just doesn’t know it yet.”

EDIT

https://www.washingtonpost.com/climate-environment/2020/10/13/warming-has-killed-half-coral-great-barrier-reef-study-finds-it-might-never-recover/