Fourth Mass Coral Reef Bleaching Event

08 Mar 2024 Fourth Mass Coral Reef Bleaching Event

This article covers ‘Daily Current Affairs’ and the topic details of the “Fourth Mass Coral Reef Bleaching Event”.This topic is relevant in the “Environment” section of the UPSC CSE exam.

Why in the News?

According to the United States NOAA, the world is on the cusp of a fourth global coral bleaching catastrophe, which could kill large areas of tropical reefs, including regions of Australia’s Great Barrier Reef.

Key Findings of the National Oceanic and Atmospheric Administration

• Threat of Fourth Mass Bleaching Event: The National Oceanic and Atmospheric Administration (NOAA) warns that the world is on the verge of experiencing a fourth mass coral bleaching event.
• Criteria for Global Event:  For an event to be classified as global, widespread coral bleaching must be observed across three major ocean basins: the Atlantic, Pacific, and Indian.
• Devastating Past Event: The last global mass bleaching event, spanning 2014 to 2017, caused significant damage, with the Great Barrier Reef losing nearly a third of its coral.  Preliminary data suggests that roughly 15% of the world’s reefs experienced significant coral die-offs during that period.
• 2023 Poised to Be Worse:  Early indications suggest that 2023 may be even more detrimental to coral reefs.  For instance, the Caribbean region reported its worst coral bleaching ever following the recent Northern Hemisphere summer.
• El Niño and Climate Change:  Coral bleaching is frequently linked to El Niño, a natural climate phenomenon causing warmer ocean temperatures.  However, climate change adds another layer of concern.  The world recently experienced its first 12-month period with an average temperature exceeding 1.5 degrees Celsius above pre-industrial levels, a threshold believed to be a tipping point for widespread coral death.  Scientists estimate that a 1.5°C increase could lead to the loss of 90% of the world’s coral reefs.

History of Mass Coral Bleaching Events

Coral reefs around the world have faced large-scale bleaching events with significant consequences. Here’s a look at some of the major incidents:

• 1998: First Mass Bleaching:  This event, triggered by El Niño-induced warming in the Pacific Ocean, caused the first widespread coral bleaching observed globally. An estimated 8% of the world’s coral reefs died during this event.
• 2002: Second Mass Bleaching: While details about the 2002 event are scarcer, it serves as a reminder that mass coral bleaching remained a threat in the early 21st century.
• 2014-2017: Third Mass Bleaching: This extended bleaching episode, considered the most severe on record, impacted reefs across a vast geographic area. Regions affected included Guam (Western Pacific), the North and South Pacific Ocean, and the Indian Ocean. The Great Barrier Reef suffered immensely, losing nearly a third of its coral during this period.

About Coral and Coral Reefs

• Corals are marine invertebrates belonging to the phylum Cnidaria, typically forming colonies of polyps that secrete a calcium carbonate skeleton. These organisms often exhibit a symbiotic relationship with photosynthetic algae called zooxanthellae, which reside within their tissues and contribute to the vibrant colours seen in coral reefs.
• Coral reefs, on the other hand, are diverse ecosystems composed of coral colonies, associated marine life, and a complex structure of calcium carbonate. These reefs thrive in warm, shallow waters, providing habitat and sustenance for a myriad of marine species. Coral reefs play a crucial role in marine biodiversity, supporting numerous ecological functions and serving as vital resources for coastal communities.

Significance of Coral Reefs

Coral reefs are more than just beautiful underwater formations. They are essential for the health of our oceans and the planet. 

• Underwater Rainforests:  Teeming with life, coral reefs are often referred to as the “rainforests of the sea” due to their incredible biodiversity. They provide habitat for a vast array of marine species, from fish and invertebrates to sea turtles and sharks.
• Economic Powerhouses:  Healthy reefs aren’t just ecologically important. They also contribute significantly to the global economy. Fisheries that rely on healthy coral reef ecosystems support millions of people worldwide and generate billions of dollars in revenue. Additionally, tourism thrives in areas with vibrant coral reefs, attracting scuba divers, snorkelers, and nature enthusiasts.
• Coastal Guardians:  Coral reefs act as natural barriers, protecting coastlines from the full force of waves, storms, and hurricanes. By absorbing wave energy, they shield beaches and coastal infrastructure from erosion, saving billions of dollars in potential damage.

Understanding Coral Bleaching

Coral reefs are under threat from a phenomenon called coral bleaching. This occurs when corals become stressed by changes in their environment, such as rising water temperatures. This stress disrupts the vital relationship between coral polyps and the algae living within them (zooxanthellae). As a defence mechanism, the coral expels the algae, losing its vibrant colours and turning stark white. 

Some of the causes of Coral Bleaching are:

• Environmental Shifts: Changes in water temperature, light, and nutrients can all stress corals. It disrupts their symbiotic relationship with algae and leading to bleaching.
• Climate Change: Rising global temperatures, a hallmark of climate change, are a major driver of coral bleaching by creating a stressful environment for coral.
• Ocean Acidification:  The ocean’s absorption of excess carbon dioxide makes it more acidic, hindering coral’s ability to maintain its symbiotic partnership and increasing bleach risk.
• Pollution:  Pollution from agriculture, industry, and waste disposal disrupts the delicate balance within coral and contributes to bleaching.
• Sunlight Exposure:  Excessive sunlight, especially during low tides, combined with high temperatures, can intensify stress and increase bleaching risk.
• Water Quality Fluctuations:  Changes in water salinity and nutrient levels can disrupt the coral-algae balance, contributing to bleaching.
• Disease:  Coral diseases, often worsened by environmental stressors, weaken corals and make them more susceptible to bleaching.

Download Yojna daily current affairs eng med 8th March 2024

Prelims practise questions

Q1. Consider the following statements:

1. The majority of the global coral reefs are situated in tropical waters.
2. Australia, Indonesia, and the Philippines collectively harbour over one-third of the world’s coral reefs.
3. Coral reefs accommodate a greater diversity of animal species compared to tropical rainforests.

Which of the provided statements is/are correct?

(a) Only 1 and 2

(b) Only 3

(c) Only 1 and 3

(d) All of the above

Answer: D

Mains practise question

Q1. Analyse the role of coral reefs in providing shoreline protection. How do coral structures act as natural barriers against coastal erosion and storm damage?

Himanshu Mishra

I am a content developer and have done my Post Graduation in Political Science. I have given 2 UPSC mains, 1 IB ACIO interview and have cleared UGC NET JRF too.