Great Barrier Reef’s Recovery and Vulnerability

An annual long-term monitoring report on the Great Barrier Reef's recovery and susceptibility to climate threats was just made public by the Australian Institute of Marine Science (AIMS).

In-water and airborne methods are used to survey the reefs.

Key finding

• Background: The northern and central portions of Australia's Great Barrier Reef have the highest levels of coral cover recorded during the past 36 years (GBR).
• Warning: Due to the increase in global temperatures, coral bleaching might happen quickly. There was a significant coral bleaching incident on the reef in March 2022.
• The increase in the number of hard corals is used to calculate coral cover.
• The middle part of the GBR had a 33 per cent hard coral cover, compared to 36 per cent in the northern GBR.
• In the meantime, the southern region's coral cover levels decreased from 38% in 2021 to 34% in 2022.
• Reef ecosystems are resilient and able to bounce back from disturbances like cyclones, predatory attacks, compounded heat stress, and more, as long as they don't happen frequently.
• In addition, because of their rapid growth, these corals are more vulnerable to environmental stresses like rising temperatures, cyclones, pollution, and attacks from crown-of-thorn starfish (COTs), which feed on hard corals, and so on.
• In the coming decade, global temperatures will rise by 1.5°C, the temperature at which bleaching occurs more frequently and recovery has less influence.

Causes of Recover:

• Increases in the GBR's dominant form of fast-growing Acropora corals, which are the main driver of recovery, were a major contributor.
• The lack of tropical cyclones in the past 12 months, decreased heat stress in 2020 and 2022 compared to 2016 and 2017, and a decline in COTs outbreaks are all examples of the low levels of acute stressors.

Issues Highlighted by the Report?

Climate change

• The primary danger to the reef's health is heat stress brought on by climate change, which causes coral bleaching.
• Despite numerous international measures, it is anticipated that sea temperatures would rise by 1.5°C to 2°C by the end of the century.
• According to a 2021 UN assessment, the world will warm by 1.5°C during the following ten years, a temperature at which bleaching occurs more frequently and recovery has less of an impact.

Frequent Mass bleaching

• Mass bleaching incidents have increased in frequency recently.
• When the sea surfaces heated up in 1998 due to the El Nio weather pattern, it resulted in the first major bleaching event, which led to the death of 8% of the world's coral.
• The second incident happened in 2002. But from 2014 to 2017, the bleaching episode caused the most harm and lasted the longest.
• Coral bleaching was noted on 45 of the 47 reefs that were part of AIMS' airborne surveys.
• Despite not being high enough to kill coral, the levels did have sub-lethal consequences like slowed growth and reproduction.

About coral reef (Click the link to know about Coral Reef In detail)

• Marine invertebrates or animals without spines include corals.
• They are the world's biggest living things.
• Each coral is referred to as a polyp, and hundreds of these polyps cohabit as a colony. The colony expands as the polyps multiply to make more copies of themselves.

They also come in two varieties:

• Hard corals: They form their hard, white coral exoskeletons by drawing calcium carbonate from the ocean.
• In a sense, they are the architects of reef ecosystems, and the amount of hard coral is an often used indicator of how well coral reefs are doing.
• Soft corals: They cling to them as well as earlier skeletons that their predecessors had produced.
• Over time, soft corals also add their own skeletons to the rigid framework.
• Coral reefs are eventually formed by these expanding, replicating structure

Significance

• Despite only making just 1% of the seafloor, they contribute nearly 25% of the marine biodiversity.
• Global fishing enterprises are further fueled by the marine life that coral reefs nourish.
• Additionally, through commerce in goods and services as well as tourism, coral reef systems create USD 2.7 trillion in economic value each year.

What is Australia’s Great Barrier Reef?

• It is the largest reef system in the world, spanning 2,300 km, and has about 3,000 distinct reefs.
• Additionally, it supports 4,000 distinct types of molluscs, 1,500 species of fish, and 400 different forms of coral.

Relevance:

• Prior to the Covid-19 era, the Reef supported approximately 60,000 people, including divers and tour guides, and brought in USD 4.6 billion annually from tourism

Conclusion

The forecast for the disturbance in the future predicts a rise in maritime heatwaves with longer durations as well as a persistent risk of COTs outbreaks and cyclones.

While the observed recovery is encouraging for the GBR's overall status, there is growing doubt about its ability to sustain this position.