MANGROVES

SYLLABUS:

GS 3 > Environment & Ecology   >  Mangroves

REFERENCE NEWS:

• The recently released "The State of the World's Mangroves 2024" report by the Global Mangrove Alliance (GMA) highlights critical issues and the current status of mangrove forests globally.

KEY HIGHLIGHTS OF THE REPORT:

• Southeast Asia dominates global mangrove coverage with 49,500 sq km, accounting for 33.6% of the world's total. Indonesia alone holds 21% of global mangroves.
• South Asia (in which India is located) has 9,749 sq km, making up 6.6% of the global mangrove forests.
• The report summarizes that a total area of 4,083 sq km of mangroves has been lost since 1996, combining the effects of both human activities and natural environmental changes.
• Also, the report states that between 2000 and 2020, 43% of mangrove losses were due to conversion to aquaculture, oil palm plantations, and rice cultivation.

WHAT ARE MANGROVES?

• Mangroves are salt tolerant plant communities found in tropical and sub-tropical intertidal regions of the world.
• Such areas are characterised by high rainfall (between 1000 mm to 3000 mm) and temperature (between 26-35°C). They occur worldwide in the tropics and subtropics, mainly between latitudes 25° N and 25° S.
• Mangroves are restricted mainly to the tropical areas as they cannot tolerate the extreme cold events typical of the temperate zone.

FEATURES OF MANGROVES: 

Mangroves adapt to challenging environments like waterlogged and anoxic soils through distinct features:

• Halophytes: They filter up to 90% of salt from seawater and can excrete excess salt through leaf glands.
• Water Retention: Mangroves store water in succulent leaves, with a waxy coating to reduce evaporation.
• Pneumatophores: Pencil-like roots act as snorkels for air intake, aiding survival during tidal floods.
• Prop Roots: Dense aerial roots provide stability against waves and tides.
• Lenticellated Bark: Oxygen enters through pores in the bark and roots, suitable for low-oxygen conditions.
• Viviparous: Seeds germinate while still on the tree, ready to root upon falling

MANGROVES IN INDIA:

• According to the India state of forest report, 2021, the mangrove cover in India is 4,992 sq km, which is 0.15% of the country's total geographical area.
• West Bengal leads with 2,114 sq km, followed by Gujarat with 1,177 sq km, which includes significant areas in the Gulf of Kutch and Gulf of Khambhat.

SIGNIFICANCE OF MANGROVES:

• Ecosystem services:
  • Abode of biodiversity: Mangrove forests make up one of the most productive and biologically diverse ecosystems on the planet. They are home to an array of species, making them an important biodiversity hotspot.
• Nursery for species: Mangroves serve as valuable nursery areas for fish and invertebrates. These habitats provide a rich source of food while also offering refuge from predation.
• Biological barrier: The ability to retain sediments flowing from upstream prevents contamination of downstream waterways and protects sensitive habitat like coral reefs and seagrass beds below.
• Water filtration: With their dense network of roots and surrounding vegetation, mangroves filter and trap sediments, heavy metals, and other pollutants, thereby maintaining water quality.
• Economic significance:
  • Fisheries: Mangrove forests are home to a large variety of fish, crab, shrimp, and mollusk species. This form an essential source of food and income for coastal communities around the world.
• Timber and plant products: Mangrove wood is resistant to rot and insects, making it for construction and fuel. Mangroves also provide minor forest products such as honey and resin.
• Tourism: Often located near to coral reefs and sandy beaches, the forests provide a rich environment for tourist activities like recreational tours, snorkelling and birdwatching.
• Shoreline stabilisation:
  • The dense root systems of mangrove forests trap sediments flowing down rivers and off the land. This helps stabilizes the coastline and prevents erosion from waves and storms.
• Natural barrier:
  • As risks from climate change brings about extreme weather events, mangrove forests can help lessen devastation in coastal areas.
  • For instance, a mangrove forest could reduce the effects of a Category 5 storm to the intensity and effects of a Category 3 storm.
• Carbon sinks:
  • Mangroves absorb up to four times more carbon dioxide per area than terrestrial forests, making them highly effective at mitigating climate change. Protecting and expanding these forests enhances their carbon scrubbing capabilities. For instance, the State of the World's Mangroves 2024 report said that mangroves store an average of 394 tonnes of carbon per hectare.

THREATS TO MANGROVES:

• Change in Land-use: 
  • The area of mangrove forest continues to shrink due to activities such as shrimp aquaculture and salt farms, which involve clearing, dredging, and diking. The removal of mangroves allows strong waves to erode vital sediments, impeding seedling growth and nutrient retention.
  • For instance, according to the "State of the World’s Mangroves, 2024" report, shrimp aquaculture has severely impacted mangroves since the 1980s, causing significant losses in areas like Kerala and Eastern India, as well as countries like Indonesia and Brazil. 
• Irresponsible tourism:
  • Unregulated tourism has taken its toll on the environmental integrity of the mangroves. Creation of walkways and tourist amenities and littering is changing the physical characteristics of mangrove forests.
• Pollution:
  • Municipal wastes and agricultural runoff containing pesticides, antibiotics and other pollutants are making its way into water supplies. Another major threat is from thermal pollution and oil spills, as they smother mangrove roots and suffocate the trees.
• River diversion:
  • Dams and irrigation reduce the amount of water reaching mangrove forests, changing the salinity level of water in the forest.
  • For example, the construction of Farakka Barrage in 1975 has altered fresh water flow around the delta, thereby altering the ecology of Sundarbans.
• Lumber industry:
  • Chopping down mangroves for charcoal and timber is an important cottage industry. While harvesting has taken place for centuries, in some parts of the world it is no longer sustainable, threatening the future of the forests.
• Invasive species:
  • Plantation of fast-growing non-native mangrove species has been used as a tool for mangrove restoration in several countries. However, the fast-growth ability has made some species invasive and gradually replacing co-occurring native mangroves. For example, the red mangrove (Rhizophora mangle), native to South Florida, was introduced in Hawai'i to stabilize shorelines but turned invasive, altering local ecosystems and biodiversity.
• Climate change:
  • Mangroves need freshwater to maintain the estuarine conditions they thrive in. But as sea-levels rise, the swamps become more saline, threatening some tree species go extinct.
  • According to the "State of the World’s Mangroves, 2024" report, mangroves in the Lakshadweep archipelago and along the Tamil Nadu coast face critical endangerment mainly due to rising sea levels influenced by global warming.
• Natural threats:
  • Powerful storms and hurricanes may also severely damage mangrove habitats. Winds, waves, and flooding may be destructive enough to clear entire mangrove islands.
• Shortcomings in legislations and enforcement:
  • Forest law enforcement in India appears weak, and penalties devised by various legal instruments such as the Forest Act 1927 are ineffective. Also, since the CRZ is only a notification, it could not be enforced strictly.

WAY FORWARD:

• Scientific Management: Implement restoration and rehabilitation practices for degraded mangrove areas, especially in climate-vulnerable coastal zones.
• Socio-economic Studies: Conduct studies to recognize and protect the traditional rights of mangrove-dependent coastal communities.
• Mapping and Planning: Conduct floristic surveys along coasts to create a biodiversity atlas and identify areas for mangrove management action plans.
• Encourage People’s Participation: Make local community involvement mandatory in mangrove conservation on both public and private lands.
• Encourage Private Players: Motivate coastal industries and private landowners to participate in mangrove conservation, offering incentives for sustainable management.
• Promote Awareness: Increase public awareness about mangrove importance through exhibitions, seminars, and nature camps, and by establishing mangrove parks.
• Ensure Minimum Flow: Enforce norms for hydel projects to release minimum water downstream to support mangrove ecosystems.
• Research Support: Foster research and international collaboration to address mangrove management issues and develop scientific conservation strategies.
• Alternative Livelihood: Promote alternative income sources like dairy farming, beekeeping, ecotourism, and agro-forestry in mangrove-dependent communities.

PRACTICE QUESTION:

Q. Discuss the causes of depletion of mangroves and explain their importance in maintaining coastal ecology. (10 marks, 150 words, GS 1, UPSC CSE 2019)