Global Coral Reef Monitoring Network (GCRMN) Report


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    • Recently, Global Coral Reef Monitoring Network (GCRMN) has released a report on the status of coral reefs across the world.

    Key Highlights of the report

    • The report underlined the catastrophic consequences of global warming but said that some coral reefs can be saved by arresting greenhouse gases.
    • Rising ocean temperatures killed about 14% of the world’s coral reefs between 2009 and 2018.
      • Coral bleaching events caused by elevated sea surface temperatures” as the biggest driver of coral loss.
      • It is equivalent to more than all of the living coral in Australia.
    • Reasons for the decline: The report found that warming caused by climate change, overfishing, coastal development and declining water quality has placed coral reefs around the world under “relentless stress.”

    What are Coral Reefs?

    • A coral reef is an underwater ecosystem characterized by reef-building corals. 
    • Reefs are formed of colonies of coral polyps held together by calcium carbonate.
    • The coral polyps live in an endosymbiotic relationship with algae. 
      • Algae provide up to 90 per cent of the coral’s energy.
    • Temperature:
      • The temperature of the water should not be below 20°C. 
      • The most favourable temperature for the growth of the coral reefs is between 23°C to 25°C. 
      • The temperature should not exceed 35°C.
    • Salinity: Corals can survive only under saline conditions with an average salinity between 27% to 40%. 
    • Shallow Water: Coral reefs grow better in shallow water having a depth less than 50 m. The depth of the water should not exceed 200m.
    • Coral reefs are divided into four classes: 
      • fringing reefs, 
      • barrier reefs, 
      • atolls, and 
      • patch reefs

    Importance of Coral Reefs

    • Coral Reefs provide an important ecosystem for marine life, protect coastal areas by reducing the power of waves hitting the coast, and provide a crucial source of income for millions of people.
    • Coral reefs have an estimated global value of £6 trillion each year, due in part to their contribution to the fishing and tourism industries and the coastal protection they provide.
    • More than 500 million people worldwide depend on reefs for food, jobs and coastal defence. 
    • Extracts from animals and plants living on reefs have been used to develop treatments for asthma, arthritis, cancer and heart disease.

    Challenges to Coral Ecosystem

    • Physical damage or destruction from coastal development, dredging, quarrying, destructive fishing practices and gear, boat anchors and groundings, and recreational misuse (touching or removing corals).
    • Pollution originates on land but finds its way into coastal waters. There are many types and sources of pollution from land-based activities.
    • Overfishing can alter the food-web structure and cause cascading effects, such as reducing the numbers of grazing fish that keep corals clean of algal overgrowth. Blast fishing (i.e., using explosives to kill fish) can cause physical damage to corals as well.
    • Coral harvesting for the aquarium trade, jewellery, and curios can lead to over-harvesting of specific species, destruction of reef habitat, and reduced biodiversity.

    What is Coral Bleaching?

    • Coral bleaching occurs when environmental conditions surrounding coral change. One example is when temperatures drastically rise or fall, the coral will release symbiotic algae living inside their tissue, causing the coral to become white. 
    • Coral bleaching does not directly cause them to die but does place a higher degree of stress on the organisms.
    • The algae provide food for the coral, and the longer a coral reef is exposed to conditions that cause bleaching, the more likely it is to starve and die.


    • Maintaining the integrity and resilience of coral reef ecosystems is essential for the wellbeing of tropical coastal communities worldwide, and a critical part of the solution for achieving the Sustainable Development Goals under the 2030 Agenda for Sustainable Development.

    Source: Reuters