Syllabus: GS3/ Biodiversity and Conservation

• The US National Oceanic and Atmospheric Administration (NOAA), in collaboration with the International Coral Reef Initiative, has confirmed that the world is currently experiencing its fourth global coral bleaching event.

About the Event:

• The global bleaching-level heat stress has affected 83.7% of the planet’s coral reefs, with mass coral bleaching recorded in at least 83 countries and territories. This ongoing event is the largest of its kind to date.

Previous Bleaching Events

• The first global coral bleaching event occurred in 1998.
• The second event took place in 2010.
• The third global bleaching event, from 2014 to 2017, affected 68.2% of the world’s reef area.

Future Projections:

• Climate models predict that by 2040-2050, almost every coral reef worldwide will experience annual bleaching events.

Great Barrier Reef Status:

• The Great Barrier Reef is currently undergoing its sixth mass bleaching event. This is the second consecutive bleaching episode, following those of 2016-17, largely due to prolonged marine heatwaves, particularly in the far northern and northern regions.
• History of Bleaching in Australia
  Mass coral bleaching events in Australia have been recorded in the years: 1998, 2002, 2016, 2017, 2020, 2022, and 2024.

What are Corals?

• Corals are marine invertebrates that belong to the Cnidaria group. They are formed by polyps, which are small, soft organisms that secrete a chalk-like calcium carbonate exoskeleton for protection. Over time, these polyps create vast coral reefs made of large carbonate structures. Corals come in various colors, including red, purple, and blue, but are most commonly found in shades of brown and green due to microscopic algae called zooxanthellae.
• Coral reefs fall into three categories:
• Fringing reefs: Formed along shorelines.
• Barrier reefs: Located in open water.
• Atolls: Circular reefs formed around sunken volcanoes.

What is Coral Bleaching?

• Coral bleaching occurs when corals expel the zooxanthellae algae living within their tissues. These algae are vital to coral health as they provide energy to corals through photosynthesis. Without these algae, corals turn pale, become more vulnerable to starvation and disease, and may eventually die. While a bleached coral is not immediately dead, it can only recover if ocean temperatures return to normal. Previous global bleaching events have led to the death of 14% of the world’s remaining coral reefs.

What Triggers Coral Bleaching?

• The primary cause of coral bleaching is climate change. A rise in ocean temperatures—often as little as 2°F—can cause corals to expel their algae. However, bleaching can also occur due to extreme low tides, pollution, or excessive sunlight.

Concerns

• Coral bleaching is critical because once corals die, reefs rarely recover. With fewer corals surviving, reproduction becomes increasingly difficult, and entire reef ecosystems deteriorate. This collapse can have severe consequences for ocean health, marine life, subsistence fisheries, and tourism.

Impact of Coral Bleaching

• Wildlife: Many marine species depend on coral reefs for shelter, spawning grounds, and protection. Coral reefs also support organisms at the base of the ocean’s food chain. As these ecosystems collapse, endangered species are at an even greater risk of extinction.
• Humans: Coral reefs serve as natural barriers against waves and storm surges, protecting coastal communities. According to a 2020 estimate by the Global Coral Reef Monitoring Network, reefs contribute around $2.7 trillion annually in goods and services. Bleached corals exacerbate overfishing by disrupting food webs and reducing spawning areas for fish. Additionally, reef tourism generates billions of dollars and supports thousands of jobs.

Can Corals Recover from Bleaching?

• Corals have the potential to recover from bleaching if environmental conditions improve. However, recovery can take years or even decades, depending on the severity of the damage. If ocean temperatures cool and conditions stabilize, the algae can return, allowing the corals to gradually regain health.

The Way Ahead

• Strengthening Marine Protected Areas (MPAs) to safeguard coral ecosystems.
• Implementing coral restoration techniques, such as coral gardening and breeding resilient species to aid recovery.
• Advocating for global reductions in greenhouse gas emissions to mitigate rising temperatures and ocean acidification.
• Increasing investment in research to better understand coral resilience, bleaching triggers, and recovery, along with the development of advanced monitoring technologies.