IAS Gyan

Daily News Analysis

Coral reefs                                                                                        

9th March, 2022 Environment

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Context: Degradation and loss of coral reefs can affect about 4.5 million people in southeast Asia and the Indian Ocean, according to the Intergovernmental Panel on Climate Change (IPCC)’s Sixth Assessment Report on Impacts, Adaptation and Vulnerability.

  • Corals occupy only 0.1% of the global sea surfaces; but more than 25% of marine biodiversity is supported by them.
  • Due to global warming and anthropogenic activities coral reefs are being bleached and are dying due to rising temperature, ocean acidification and sea level rise
  • The report added that regional long-term trends and inter-decadal variations were observed in coral growth and sea surface temperatures in the South China Sea.
  • Report pointed out that the increase in pathogen abundance (virulence) and increase in susceptibility of the host reef, has led to a rise in the severity of coral diseases. It has also led to the decline in coral reef community composition.

What are corals?

  • Corals exhibit characteristics of plants but are marine animalsthat are related to jellyfish and anemones.
  • Coral polyps are tiny, soft-bodied organisms. At their base is a hard, protective limestone skeleton called a calicle, which forms the structure of coral reefs.
  • Reefs begin when a polyp attaches itself to a rock on the seafloor, then divides, or buds, into thousands of clones.
  • The polyp calicles connect to one another, creating a colony that acts as a single organism.
  • As colonies grow over hundreds and thousands of years, they join with other colonies, and become reefs.
  • There are soft corals as well, which are non-reef-building, and resemble bushes, grasses, trees.

Why are coral reefs important?

  • Coral reefs are like underwater cities that support marine life.
  • According to the UN Environment programme, they provide at least half a billion people around the world with food security and livelihoods.
  • Coral reefs also act as ‘wave breaks’ between the sea and the coastline and minimise the impact of sea erosion.
  • In India, they are protected in the same way as the tiger or elephant, under Schedule I of the Wildlife Protection Act (WPA), 1972.


What poses a threat to coral reefs?

  • Climate change remains one of the biggest threats to corals.
  • This threat has been visible in the “bleaching” of corals.
    • Bleaching is a process during which corals, under stress from warm weather, expel the algae that give corals their brilliant colours and live in their tissues and produce their food.

  • The Great Barrier Reef off the coast of Australia, a UNESCO World Heritage site and home to one of the largest collections of coral reefs on the planet, has suffered six mass bleaching events due to warmer than normal ocean temperatures: in 1998, 2002, 2006, 2016, 2017, and now 2020.