Status of Coral Reefs of the World:2020

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Status of Coral Reefs of the World: 2020 was prepared by the Global Coral Reef Monitoring Network, along with the Australian government.

Major Findings 

• Resiliency: Coral reefs have suffered terribly in the past three decades. Yet, they are resilient and would be able to withstand challenges posed by a warming world.
• Shocking aspects: There were many shocking aspects noted in the report as well.
  • For instance, the 1998 coral bleaching event killed eight per cent of the world’s coral.
  • Subsequent events between 2009 and 2018 killed 14 per cent of the world’s coral.
  • Since 2010, almost all regions had exhibited a decline in average coral cover.

• Causes: Most declines in global coral cover were associated with either rapid increase in sea surface temperature (SST) anomaly or sustained high SST anomaly.

• There were 20 per cent more algae on the world’s coral reefs in 2019 than in 2010. 
  • The increase in the number of algae was associated with declines in the amount of hard coral.

• Suggestions 
  • Reducing local pressures on coral reefs to maintain their resilience would be critical in the years to come. 
  • Monitoring data collected in the field is also essential to understand the status of the trends in coral reef conditions.
  • Ongoing investment in the development of methodological approaches, new technologies, capability and capacity that expands geographic coverage and enhances the quality, accessibility and interoperability of data is essential.

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. 

Significance

• 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 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.
• Coral reefs provide the 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. 

Challenges for 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 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.

The threat of Coral Bleaching

• Coral bleaching occurs when coral polyps expel algae that live inside their tissues. 
• When corals face stress by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae zooxanthellae living in their tissues, causing them to turn completely white. 
• This phenomenon is called coral bleaching.
• Reasons:
  • The leading cause of coral bleaching is climate change. 
  • A warming planet means a warming ocean, and a change in water temperature – as little as 2 degrees Fahrenheit – can cause coral to drive out algae. 
  • Coral may bleach for other reasons, like extremely low tides, pollution, or too much sunlight.

Image Courtesy: thestar

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.

Source: DTE