Loss of Mangrove Cover on Katchal Island | 12 Aug 2022

Why in News?

Recently, a study by the National Aeronautics and Space Administration (NASA), highlighted the loss of mangrove cover on Katchal island, part of India’s Nicobar archipelago.

• It showed the extent to which mangroves had been lost globally over the past two decades.

What are Mangroves?

• About:
  • Mangroves are tropical plants that are adapted to lose, wet soils, salt water, and being periodically submerged by tides.
• Features:
  • Saline environment: They can survive under extreme hostile environments such as high salt and low oxygen conditions.
  • Low oxygen: Underground tissue of any plant needs oxygen for respiration. But in a mangrove environment, the oxygen in soil is limited or nil.
    • For the purpose of breathing, they develop special roots called pneumatophores.
  • Survival in Extreme Conditions: With their roots submerged in water, mangrove trees thrive in hot, muddy, salty conditions that would quickly kill most plants.
  • Viviparous: Their seeds germinate while still attached to the parent tree. Once germinated, the seedling grows into a propagule.
    • A propagule is a vegetative structure that can become detached from a plant and give rise to a new plant. Examples include a bud, sucker, or spore.
• Significance:
  • Mangroves trap and cycle various organic materials, chemical elements, and important nutrients in the coastal ecosystem.
  • They provide one of the basic food chain resources for marine organisms.
  • They provide physical habitat and nursery grounds for a wide variety of marine organisms, many of which have important recreational or commercial value.
  • Mangroves also, serve as storm buffers by reducing wind and wave action in shallow shoreline areas.
• Area Covered
  • Global Mangrove Cover:
    • The total mangrove cover in the world is one 1,50,000 sq kms.
    • Asia has the largest number of mangroves worldwide.
      • South Asia comprises 6.8% of the world's mangrove cover.
  • Indian Mangrove Cover:
    • India's contribution is 45.8% total mangrove cover in South Asia.
    • According to the Indian State Forest Report 2021, Mangrove cover in India is 4992 sq. Km which is 0.15% of country’s total geographical area.
    • Largest Mangrove Forest: Sundarbans in West Bengal are the largest mangrove forest regions in the world. It is listed as a UNESCO World Heritage Site.
      • The forest is home to the Royal Bengal tiger, Gangetic dolphins and Estuarine crocodiles.
    • Bhitarkanika Mangroves: The second largest mangrove forest in India is Bhitarkanika in Odisha created by the two river deltas of River Brahmani and Baitarani.
      • It is one of the most significant Ramsar wetlands in India.
    • Godavari-Krishna Mangroves, Andhra Pradesh: The Godavari-Krishna mangroves extend from Odisha to Tamil Nadu.

What are the Key Highlights of the Study?

• The study shows the real extent of tidal wetlands lost between 1992 and 2019 on Katchal Island in the Nicobar Islands in the eastern Indian Ocean.
• The mangroves had the highest ratio of loss to gain among the three types of tidal wetlands it studied. 
  • The other two were tidal flats and marshes.
• Mangroves showed an estimated net decrease of 3,700 square kilometers between 1999 and 2019.
  • Despite the losses, there have been gains of 2,100 square kilometers indicating the considerable dynamism of these systems.
• Reasons for loss:
  • Natural cause:
    • There was an earthquake with a magnitude of 9.2 during the Tsunami of 2004, during which the islands experienced up to 3 meters (10 feet) of land subsidence. 
      • This submerged many mangrove ecosystems, resulting in a loss of more than 90% of mangrove extent in some areas.
  • Other Factors:
    • Sea level rise, shoreline erosion, storms, altered sediment flow, and subsidence.
• Human Induce:
  • Some 27% of the losses and gains were directly caused by human activity.
    • They alter wetlands through development, water diversion projects, or by converting the land to agriculture or aquaculture.
• Present Status:
  • It's very difficult that the earlier mangrove cover will ever come back but there has been a rise in their numbers in other places since they propagate themselves through propagules.

Way Forward

• Conservation needs to be linked with a broader perspective with active community involvement, environmental security, and reducing any risks from natural calamities.
  • Such measures need to be adopted more holistically in view of anticipatory adaptation measures which hold the clue for successful and effective management. 

Source: DTE