Coral Loss on Great Barrier Reef – 2024 Update

Recent assessments indicate alarming coral loss on the Great Barrier Reef due to extreme weather conditions. The Australian Institute of Marine Science (AIMS) reported important declines in coral cover following severe cyclones and unprecedented heat stress during the summer of 2023-2024. This situation marks the ongoing challenges faced by coral ecosystems globally.

Coral Cover Decline

Surveys conducted between August and October 2024 revealed that coral cover decreased on 12 out of 19 reefs surveyed. The loss ranged from 11 to 72 per cent compared to pre-summer levels. Notably, the Cooktown-Lizard Island sector experienced a decline from 31.4 per cent to 19.3 per cent, marking a record annual drop over 39 years of monitoring.

Coral Bleaching

Coral bleaching occurs when corals expel algae due to stress, turning them white. Prolonged bleaching can lead to coral death. The recent assessments indicate that nearly 77 per cent of global reefs have faced bleaching stress over the past 20 months, with the Great Barrier Reef experiencing its fifth mass bleaching event.

Impact of Cyclones and Heat Stress

Tropical Cyclones Jasper and Kirrily contributed to severe damage by increasing wave heights and causing further stress to the corals. AIMS noted that heat stress levels reached critical points, leading to important mortality rates among coral species, particularly the fast-growing Acropora.

Variability in Coral Species Response

The impact of bleaching varied among coral species. Acropora species showed the highest mortality rates, while branching Acropora and massive corals like Porites were less affected. This variability illustrates the differing resilience levels among coral types in response to environmental stressors.

Future Assessments and Expectations

Authorities plan to conduct further surveys on additional reefs, aiming to complete a full assessment by mid-2025. The findings tell the vulnerability of coral ecosystems and the urgent need for conservation efforts to protect these vital marine habitats.

Questions for UPSC:

1. Examine the factors contributing to coral bleaching and its global implications.
2. Critically discuss the impact of climate change on marine biodiversity, specifically coral reefs.
3. Analyse the role of extreme weather events in shaping marine ecosystems. Point out the long-term consequences.
4. Estimate the effectiveness of current conservation strategies for coral reefs in the context of increasing climate change threats.

Answer Hints:

1. Examine the factors contributing to coral bleaching and its global implications.

1. Coral bleaching is primarily caused by elevated sea temperatures, leading to the expulsion of symbiotic algae (zooxanthellae) from coral tissues.
2. Pollution, including nutrient runoff and sedimentation, exacerbates stress on coral reefs, making them more susceptible to bleaching.
3. Ocean acidification, resulting from increased CO2 levels, affects coral calcification processes, further threatening their survival.
4. Global implications include loss of biodiversity, disruption of marine ecosystems, and negative impacts on fisheries and tourism industries.
5. The ongoing global bleaching crisis marks the urgent need for international cooperation and effective climate action to mitigate these factors.

2. Critically discuss the impact of climate change on marine biodiversity, specifically coral reefs.

1. Climate change leads to rising ocean temperatures, which is a primary driver of coral bleaching and mortality.
2. Increased frequency of extreme weather events, like cyclones, causes physical damage to coral structures and ecosystems.
3. Changes in ocean chemistry, such as acidification, impair coral growth and reproduction, threatening their long-term viability.
4. Loss of coral reefs affects the entire marine food web, as they provide habitat and shelter for numerous marine species.
5. As coral reefs decline, there are important socio-economic consequences, including reduced livelihoods for communities dependent on fishing and tourism.

3. Analyse the role of extreme weather events in shaping marine ecosystems. Point out the long-term consequences.

1. Extreme weather events, such as cyclones and heatwaves, can cause immediate and severe physical damage to coral reefs, leading to habitat loss.
2. These events disrupt the ecological balance, affecting species composition and abundance in marine ecosystems.
3. Long-term consequences include decreased biodiversity, altered food webs, and diminished ecosystem services provided by healthy reefs.
4. Repeated disturbances can hinder coral recovery, making ecosystems more vulnerable to future stressors and potentially leading to ecosystem collapse.
5. The cumulative effects of extreme weather can exacerbate the impacts of climate change, creating a cycle of degradation in marine environments.

4. Estimate the effectiveness of current conservation strategies for coral reefs in the context of increasing climate change threats.

1. Current conservation strategies focus on marine protected areas (MPAs), which can help mitigate local stressors but may not be sufficient against global climate threats.
2. Efforts to reduce pollution and manage fisheries are crucial, yet they must be coupled with broader climate action to be effective.
3. Restoration projects, such as coral gardening and artificial reefs, show promise but are resource-intensive and may not keep pace with climate change impacts.
4. Community engagement and education are vital for encouraging stewardship, yet their effectiveness can be limited by socio-economic challenges.
5. Overall, while current strategies provide some benefits, a more integrated approach addressing both local and global threats is essential for long-term coral reef resilience.