Recent coral recovery in the Great Barrier Reef has paused

The hard coral recovery of the Great Barrier Reef, a critical barometer of the reef’s health, remains largely stable but shows small declines in certain regions, according to the latest annual report by the Australian Institute of Marine Science (AIMS).

The findings shed light on the delicate equilibrium of recovery and loss within the reef system and raise concerns about the fragility of recent gains.

Published on Wednesday, August 9, the AIMS’ Annual Summary Report on Coral Reef Condition for 2022/23 provides an extensive view of the changes in coral cover across the Great Barrier Reef. Although some areas of the reef exhibited a continuation of recovery, this progress was offset by coral loss in other regions, leading to minimal change in overall coral cover.

Coral recovery is a mixed bag

The report reveals a mixed picture. Last year’s analysis marked a historical high for coral cover in the Northern and Central regions since AIMS started its monitoring 37 years ago.

However, the recent data indicate a pause in that recovery, partially attributed to the 2022 mass coral bleaching event. Coral-eating crown-of-thorns starfish and a January 2022 cyclone contributed to the loss in the Northern region.

In the Southern region, crown-of-thorns starfish outbreaks and coral disease kept coral cover comparable to last year, with bleaching playing a less significant role.

Great Barrier Reef recovery is a delicate situation

Dr. David Wachenfeld, AIMS Research Program Director, emphasized the precarious nature of the reef’s recovery. He stated, “The 2022 coral bleaching event was not as severe as the 2016 or 2017 events but caused enough mortality to pause recent regional gains in hard coral cover. The heat stress during the bleaching event also likely had sub-lethal effects, including reductions in coral growth and reproduction.”

Dr. Wachenfeld also cautioned against complacency, highlighting that the reef’s ecosystem remains under threat. “Conditions were relatively mild over the 2023 summer with low levels of coral bleaching and no cyclones crossing the Reef. However, we are only one large scale disturbance away from a rapid reversal of recent recovery. The Reef remains a wonderful, complex and beautiful system, but it is at increased risk with climate change driving more frequent and severe bleaching events, putting increasing pressure on the ecosystem’s resilience.”

The report outlines the following coral cover percentages for 2022/23:

• Northern region (north of Cooktown): 35.7%, down from 36.5% last year
  
• Central region (Cooktown to Proserpine): 30.8%, down from 32.6%
  
• Southern region (south of Proserpine): 33.8%, down from 33.9%

AIMS Long Term Monitoring Program

The survey, conducted between August 2022 and May 2023, covered reef slopes on the perimeters of 111 reefs under AIMS Long Term Monitoring Program (LTMP), offering a valuable 37-year-long dataset on the Great Barrier Reef.

AIMS Long-Term Monitoring Program leader Dr. Mike Emslie described the primary forces behind the recent recovery as fast-growing branching and plate corals, known as Acropora, although other corals also contributed.

Emslie said, “Acropora are highly abundant, responsible for most of the ups and downs in hard coral cover, and have been going through a rapid growth phase in recent years. But other corals on the Reef have also contributed to this recovery.”

Concerns were also raised about the increasing frequency of mass coral bleaching events on the Great Barrier Reef, with four since 2016. Dr. Emslie noted the anomaly of the 2022 bleaching event occurring during a La Niña year, typically characterized by cooler temperatures.

He stated, “If there were no disturbances, we would expect the recent increases in coral cover to continue this year. However, this pause indicates that a mass bleaching event, even if less severe, with low mortality, is still enough to put the brakes on this coral recovery. This means the Reef is still at risk of decline from more frequent disturbances. AIMS is working to understand the effect of this climatic instability through monitoring and research.”

Call for global action on coral recovery

The report concludes with a call for global action, as Dr. Wachenfeld added, “The best hope for the future of the Great Barrier Reef and all coral reefs globally requires reduction in greenhouse gas emissions to stabilize temperatures, best practice management of local pressures, and the development of interventions to help boost climate tolerance and resilience for coral reefs.”

AIMS’ exhaustive survey methods included manta tow surveys, allowing scientists to efficiently assess large reef areas, and detailed investigations on 73 reefs, offering deeper insights into the corals, fishes, crown of thorns starfish, coral diseases, and bleaching.

The monitoring team spent 120 days at sea, traveling 1016km around the perimeter of the 111 reefs surveyed. The new survey season begins in late August and will continue until May 2024.

The efforts of the AIMS LTMP team play a vital role in the Reef 2050 Integrated Monitoring and Reporting Program, providing essential insights and nuanced understanding of the Great Barrier Reef’s current status.

As the world’s largest coral reef system grapples with the challenges posed by climate change and local disturbances, continuous monitoring and informed policymaking remain crucial to its survival and flourishing.

More about the Great Barrier Reef

The Great Barrier Reef is one of the most famous coral reef systems in the world and is located in the Coral Sea, off the coast of Queensland, Australia. Here’s an overview of the essential information about this remarkable ecosystem:

Size and structure

The Great Barrier Reef is the world’s largest coral reef system, comprising over 2,900 individual reefs and 900 islands, stretching over 2,300 kilometers (1,400 miles). It covers an area of approximately 344,400 square kilometers (133,000 square miles).

Great Barrier Reef Biological diversity

It’s one of the most diverse ecosystems on the planet, home to thousands of species. This includes over 1,500 species of fish, 400 species of coral, 4,000 species of mollusk, 240 species of birds, and a wide variety of other marine life like sharks, dolphins, and turtles.

Economic importance

The Great Barrier Reef contributes significantly to the Australian economy through tourism, fishing, and scientific research. Tourism related to the reef generates billions of dollars annually.

Environmental threats

The reef faces several threats, including climate change, pollution, overfishing, and coastal development. Climate change leads to ocean acidification and rising sea temperatures, which cause coral bleaching. Runoff from agricultural land can lead to water pollution.

Great Barrier Reef Coral bleaching

Coral bleaching is a significant concern for the reef. When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.

Protection and conservation efforts

The Great Barrier Reef Marine Park was established in 1975 to regulate the use of the reef and protect its delicate ecosystems. Additionally, the reef was designated as a UNESCO World Heritage Site in 1981.

Research and monitoring

Various organizations are involved in the continuous monitoring and research of the reef to understand its health and the effects of human activity.

Cultural importance

The area is also significant for the indigenous people of the region, including the Torres Strait Islanders and the Aboriginal Australian groups, who have cultural connections to the reef.

Geological features

The Great Barrier Reef is not a single reef but a complex system of interlinked reefs. The formation began as early as 500,000 years ago, and the current structure was formed around 6,000 to 8,000 years ago at the end of the last Ice Age.

Tourism and recreation

It’s a major destination for divers and snorkelers from around the world who want to experience its unique underwater beauty. Various recreational activities like diving, snorkeling, boating, and fishing are popular.

The Great Barrier Reef is a globally significant ecosystem known for its size, diversity, and beauty. However, it is facing severe threats from human activities and climate change, making conservation and responsible management vital to its future health and survival.