Degradation of Coral Reefs: IPCC Report

In News 

• 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.

Major Highlights of the Report

• The report talks about the effects of global warming and anthropogenic activities on Asia’s coral reefs. 
• The coral occupies only 0.1 per cent of the global sea surface. But more than 25 percent of marine biodiversity is supported by them, which includes fisheries as well. They are the first that get affected by high temperatures.
• In the coral reef fisheries sector, there are about 3.35 million fishers in southeast Asia and 1.5 million fishers in the Indian Ocean.
• Regional long-term trends and inter-decadal variations were observed in coral growth and sea surface temperatures in the South China Sea.
• Along the Indian coast, a varied bleaching and recovery pattern among corals was observed during the 2016 bleaching episode. 
• Bleaching was high in Acropora (86.36 per cent), followed by Porites (65.45 per cent), while moderate to no bleaching was observed in Favites Symphyllia, Favia, Platygyra and Goniastrea.
• Relative risk has been found to be high in the province of Papua in Indonesia, the Philippines, Japan, India, northern Maldives, the Persian Gulf and the Red Sea.
• In Bangladesh, the coral reefs of St. Martin’s Island contribute $33.6 million per year to the local economy. 
• Climate change, along with other anthropogenic activities, has been identified as a threat to these habitats.
• Causes 
  • The reefs are being bleached and are dying due to changes in the beneficial microorganisms of coral, caused by environmental stress.
  • Coral growth was predicted to decline by the end of this century and human activities were one such factor that had contributed to the reduction in growth.
  • Increased seawater temperature has been found to affect the functioning of symbiotic algae of corals and its bacterial consortia, leading to coral bleaching and mortality.
• Impacts: 
  • The economic loss under different climate change scenarios was estimated to range from $27.78 million to $31.72 million annually in Nharang Bay, Vietnam. 
  • Coastal habitats of Asia are diverse and the impacts of climate change including rising temperature, ocean acidification and sea level rise has been known to affect the services and the livelihood of people depending on it.
  •  The risk of irreversible loss of many marine and coastal ecosystems increases with global warming, especially at 2 degrees Celsius (°C) or more.
  • 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.

Coral Reefs

• A coral reef is an underwater ecosystem characterised by reef-building corals. 
• Formation :
  • Coral reefs are formed over a process of thousands of years. Each coral reef is made up of colonies of tiny animals called polyps. 
  • Each polyp produces calcium carbonate, which makes up their skeleton and protects corals internal bodies; similar to how our skeleton protects our organs. 
• The coral polyps live in an endosymbiotic relationship with algae. Algae provides 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. 

Benefits 

• Coral Reefs provide an important ecosystem for life underwater, 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 are also our first line of defence against tropical storms, helping to protect all of our coastal communities.
• Coral reefs support tourism and recreation, drawing people from all over the world to see their beautiful and diverse ecosystems.
• Extracts from animals and plants living on reefs have been used to develop treatments for asthma, arthritis, cancer and heart disease.
• Coral reefs provide biodiversity: 
  • Thousands of species can be found living on one reef. 
  • The Great Barrier Reef contains over 400 coral species, 1,500 fish species, 4,000 mollusc species and six of the world’s seven sea turtle species. 
  • The Coral Triangle – a coral-rich marine region in Southeast Asia that encompasses the waters between Indonesia, Malaysia, the Philippines and Papua New Guinea – is the most biologically diverse marine ecosystem on Earth. 

Threats to Coral Reefs

• 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 that 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 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.
• Rising water temperatures: Corals thrive in relatively warm water, but when water temperatures rise too high, the zooxanthellae are forced to leave. Since these algae give the corals colour, when they leave the coral becomes white, appearing bleached.This coral bleaching can cause the reef to die.

Way Forward

• The countries could act to improve water quality at the reef, which would increase its resilience to climate change.
• Make collaborative efforts to mitigate the global effects of climate change – warming seas and increasing sea levels etc.
• The government is  backing the health of the reef and the economic future of tourism operators, hospitality providers and Queensland communities that are at the heart of the reef economy.

Source:DTE