General Studies Paper 1 (World Geography): Coral Reefs

Great Barrier Reef Australia

IAS Junior Mains Answer Writing June-Sep 2019 Schedule (Click Here)


Syllabus: General Studies Paper 1 (World Geography)


Discuss the process of formation of coral reefs. What role does the Great Barrier Reef of Australia play in maintaining the coastal ecology? Explain.



Corals reefs are one of the most diverse habitats in the ocean. It is commonly known as the rainforest of oceans. In tropical seas, many types of coral animals and marine organisms such as coral polyps, calcareous algae, shell-forming creatures and lime-secreting plants live in large colonies. Though they are very tiny creatures, their ability to secrete calcium carbonate within their tiny cells has given rise to a particular type of marine landform. The landforms are popularly known as coral reefs. The Great Barrier Reef makes up about 10 per cent of the world’s coral reef ecosystems, and is one of the best known and most complex natural systems on Earth.


Formation of Coral Reefs.

Several theories try to explain the formation of coral reefs. So far, only two have been approved as they explain the great vertical thickness of coral reefs. These two include:

  • Darwin’s Subsidence Theory
    • According to this theory, coral reefs were initially fringing reefs on slanting shores, after which they became barrier reefs when the shores sank, with a water channel between them and the land.
    • If the land is an island that sinks entirely, it results in the formation of an atoll, which means the sinking causes the thickness of the reefs.
  • Daly’s Glacial-control Theory
    • This theory states that during the last glacial period, the formation of ice caps lowered the ocean levels by 60 to 70 meters below the current ocean levels.
    • Waves then cut the shores to make flat platforms suitable for the growth of coral reefs.
    • Over time as the ice caps melted and the levels of temperatures rose, coral began to grow on those platforms and rose upwards managing to raise the ocean levels.
    • After that, all types of reefs were formed on the existing platforms.


Types of Coral Reefs:

The three main types of coral reefs include,

  • Fringing Reefs
    • Fringing reefs are found along the coastline of the islands and continents. They are the most common type of reef structure found in the ocean. Sometimes they are separated by a shallow lagoon.
    •  Fringing reefs develop on the wave cut platforms along the continents and Islands. Their outer edge grows rapidly due to the availability of oxygenated water and food supply by constant wave currents.
  • Barrier Reefs 
    • A barrier reef is separated from the coast by a much wider and deeper channel or lagoon.
    • The reef is partially submerged. Where it lies above the water level. The barrier reefs have narrow gaps at several places to allow the water from the enclosed lagoon to return to the open ocean
    • . Such gaps are very useful for shipping and provide the only entrances for ships to enter or leave the lagoon. The best-known barrier reef is the Great Barrier Reef off the coast of Queensland, Australia. It is 1200 miles (around 2000 km) long, separated from the coast by a channel 100 miles (160 km) wide in places and over 200 feet (60 m) deep.
  • Atolls
    • Atolls are similar to barrier reefs except that they are circular, enclosing a shallow lagoon without any land in the centre.
    • The encircling ring is usually broken in a few places to allow the free flow of water.
    • Some of the large atolls include Sudadiva in the Maldives, Bangaram atoll in Lakshadweep.


Role played by the Great Barrier Reef:

  • The Great Barrier Reef stands as one of the most varied ecosystems in the world, serving as a natural environment for thousands of species of marine life.
  • It protects coastlines from the damaging effects of tropical storms and waves.
  • It assists in carbon and nitrogen fixing.
  • Helps with nutrient recycling, and provides a habitat for a variety of marine organisms.
  • The Great Barrier Reef supports an extraordinary diversity of life, including many vulnerable or endangered species, some of which may be endemic to the reef system. It provides habitat for nearly 9,000 species of marine life
  • The reef’s rich biodiversity helps it to maintain a stable and healthy coral reef system.
  • The Great Barrier Reef and coral reefs like it support more species per unit area than any other marine environment. This biodiversity is crucial in discovering new medications and treatments for illnesses.
  • Coral reefs are an important factor in the ecosystem, in tourism, fisheries, and coastline protection.

However, Coral reefs are deteriorating due to human interference. Boats and recreational contact cause physical damage to the reefs. Runoff of sediments, contaminants, nutrients from agriculture, industry, sewage and land clearing in the watershed threatens the health of coral reefs. Poor water quality, increased water temperatures and increased pollution create a higher likelihood for coral disease, which is responsible for the widespread mortality of biodiversity seen in the last three decades, 



Great Barrier Reef is the largest coral reef ecosystem on our planet and home to not just corals, but countless other marine life. The enormous coral reef that graces the waters of eastern Queensland extends for 2,300 kilometres, is the planet’s largest living structure. Coral reefs are an important factor in the ecosystem, in tourism, fisheries, and coastline protection. Coral reefs offer coastline protection to nearby islands by absorbing wave energy.  However, coral reefs are under threat around the world. Due to rising ocean temperatures and pH changes, coral reefs are dying off, and are in danger of extinction. About 10% of coral reefs are now dead, and about 60% are considered at risk. By 2050, all of the world’s coral reefs are estimated to be in danger. Protection and restoration processes are now of the utmost importance.


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