The Great Barrier Reef Has Lost Half Its Corals – Massive Declines in Just 3 Decades

Great Barrier Reef Brown Coral

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A brand-new research study of the Great Barrier Reef reveals populations of its little, medium and big corals have all decreased in the previous 3 years.

Lead author Dr. Andy Dietzel, from the ARC Centre of Excellence for Coral Reef Studies (CoralCoE), states while there are various research studies over centuries on the modifications in the structure of populations of people — or, in the natural world, trees — there still isn’t the comparable details on the modifications in coral populations.

“We measured changes in colony sizes because population studies are important for understanding demography and the corals’ capacity to breed,” Dr. Dietzel stated.

He and his co-authors evaluated coral neighborhoods and their nest size along the length of the Great Barrier Reef in between 1995 and 2017. Their results reveal an exhaustion of coral populations.

“We found the number of small, medium, and large corals on the Great Barrier Reef has declined by more than 50 percent since the 1990s,” stated co-author Professor Terry Hughes, likewise from CoralCoE.

“The decline occurred in both shallow and deeper water, and across virtually all species — but especially in branching and table-shaped corals. These were the worst affected by record-breaking temperatures that triggered mass bleaching in 2016 and 2017,” Prof Hughes stated.

Great Barrier Reef Lost Coral

The Great Barrier Reef has actually lost half its corals in the previous 3 years. As more intricate coral structure is lost, so too are the environments for fish. Credit: Andreas Dietzel

The branching and table-shaped corals offer the structures essential for reef occupants such as fish. The loss of these corals indicates a loss of environment, which in turn decreases fish abundance and the performance of reef fisheries.

Dr. Dietzel states among the significant ramifications of coral size is its impact on survival and breeding.

“A vibrant coral population has millions of small, baby corals, as well as many large ones — the big mamas who produce most of the larvae,” he stated.

“Our results show the ability of the Great Barrier Reef to recover — its resilience — is compromised compared to the past, because there are fewer babies, and fewer large breeding adults.”

The authors of the research study state much better information on the market patterns of corals is urgently required.

“If we want to understand how coral populations are changing and whether or not they can recover between disturbances, we need more detailed demographic data: on recruitment, on reproduction and on colony size structure,” Dr Dietzel stated.

“We used to think the Great Barrier Reef is protected by its sheer size — but our results show that even the world’s largest and relatively well-protected reef system is increasingly compromised and in decline,” Prof Hughes stated.

Climate modification is driving a boost in the frequency of reef disruptions such as marine heatwaves. The research study records steeper wear and tears of coral nests in the Northern and Central Great Barrier Reef after the mass coral whitening occasions in 2016 and 2017. And the southern part of the reef was likewise exposed to record-breaking temperature levels in early 2020.

“There is no time to lose — we must sharply decrease greenhouse gas emissions ASAP,” the authors conclude.

Reference: “Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef” by Andreas Dietzel, Michael Bode, Sean R. Connolly and Terry P. Hughes, 14 October 2020, Proceedings of the Royal Society B.
DOI: 10.1098/rspb.2020.1432

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