Environment & Ecology > Biodiversity > Biogeography
- The Sundarbans mangrove ecosystem has been categorized as an ‘endangered ecosystem’ by a team of researchers using the IUCN’s Red List of Ecosystems framework.
WHAT ARE MANGROVES:
- Mangroves are a group of trees and shrubs that live in the coastal intertidal zone.
- 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 are adapted to surviving in waterlogged and anoxic soil, including slow-moving and brackish water due to some of its distinct features.
- Halophytes: Mangrove species survive by filtering out as much as 90% of the salt found in seawater as it enters their roots. Some species excrete salt through glands in their leaves.
- Water retention capacity: Mangroves store fresh water in thick succulent leaves. A waxy coating on the leaves of some mangrove species seals in water and minimizes evaporation.
- Pneumatophores: Some mangroves grow pencil-like roots that stick up out of the ground like snorkels and take in oxygen from the air. These roots allow mangroves to cope with daily flooding by the tides.
- Prop roots: Many mangrove trees have dense intertwined aerial roots that descend from their trunks and branches that stabilize and support them from battering waves and shifting tides.
- Lenticellated bark: Besides the root, oxygen enters a mangrove through lenticels, thousands of cell-sized breathing pores in the bark and roots. This helps them adapt to the low oxygen conditions.
- Viviparous: Seed pods germinate while on the tree, so they are ready to take root when they drop.
MANGROVES IN INDIA:
- According to the India state of forest report, 2019, the mangrove cover in India is 4,975 sq km, which is 0.15% of the country's total geographical area.
- Among the states and UTs, West Bengal has the highest percentage of area under total Mangrove cover followed by Gujarat and Andaman Nicobar Islands.
- Mangrove areas of the country are represented in the Sunderbans Tiger Reserve, Bhitarkanika, Coringa, Nelapattu, Point Calimere Wildlife Sanctuaries, Pirotan National Park and other areas.
- The Sundarbans is the largest contiguous mangrove forest in the world. Its name derives from the dominant mangrove species sundari (Heritiera fomes).
- It spans from the Hooghly River in India's state of West Bengal to the Baleswar River in Bangladesh, covering the deltas of the Ganges, Brahmaputra and Meghna rivers.
- Four protected areas in the Sundarbans are enlisted as UNESCO World Heritage Sites, viz. Sundarbans National Park, Sundarbans West, Sundarbans South and Sundarbans East Wildlife Sanctuaries.
- The area is known for its wide range of fauna, including 260 bird species, the Bengal tiger and other threatened species such as the estuarine crocodile and the Indian python.
SIGNIFICANCE OF MANGROVES:
- Ecosystem services:
- Rich biodiversity: Mangrove forests make up one of the most productive and biologically diverse ecosystems on the planet. They are home to an incredible array of species, making them an important biodiversity hotspot.
- Water filtration: Mangroves are essential to maintaining water quality. With their dense network of roots and surrounding vegetation, they filter and trap sediments, heavy metals, and other pollutants.
- 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.
- Economic significance:
- Fisheries: Mangrove forests are home to a large variety of fish, crab, shrimp, and mollusk species. These fisheries form an essential source of food for thousands of coastal communities around the world.
- Timber and plant products: The trees are a reliable source of wood for construction and fuel. Mangrove wood is resistant to rot and insects, making it extremely valuable. 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: Dense mangrove forests lessen the power of waves before they hit coastal areas. A mangrove forest could reduce the effects of a Category 5 storm to the intensity and effects of a Category 3 storm. As risks from climate change brings about extreme weather events, mangrove forests can help lessen devastation in coastal areas.
- Carbon sinks: Mangroves have the ability to absorb up to four times more carbon dioxide by area than upland terrestrial forests, making them among the planet's best carbon scrubbers. By protecting existing mangrove forests and allowing them to spread from their original habitats, we can mitigate the effects of climate change.
EXISTING PROTECTION MEASURES:
In the international level, there is neither any specific Convention, nor any other mechanism which deals with the protection of mangroves. However, from the existing international documents, an indirect obligation of the States to protect and preserve mangroves could be inferred.
- Ramsar Convention: Officially called the ‘The Convention on Wetlands of International Importance especially as Waterfowl Habitat’, Ramsar convention is an intergovernmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources.
- Agenda 21 of Rio declaration: It says about the protection of the oceans, all kinds of seas, including enclosed and semi-enclosed seas, and coastal areas and the protection, rational use and development of their living resources.
- Red List of Ecosystems (RLE) Framework of IUCN:
- RLE is a global framework for monitoring and documenting the status of ecosystems.
- It was developed by the International Union for Conservation of Nature (IUCN) for biodiversity risk assessment.
- Its main objectives are to support conservation, resource use and management decisions by evaluating all the world's ecosystems by 2025.
- Article 48A of the Indian constitution puts an obligation on the part of the state to protect and improve the environment.
- Indian Forest Act, 1927: Several mangrove forests have been declared as reserved forests and protected forests based on the provision of the 1927 act.
- Marine Protected Areas (MPAs) under WPA: Some mangrove forests are protected under the Marine Protected Areas. The MPAs are notified under Wildlife (Protection) Act, 1972 (WPA) either as National Parks or as Wildlife Sanctuary.
- Forest Conservation Act, 1980: It provides effective protection to the forest resources. This act mandates prior approval from the Central Government for using forest land for the non-forest purpose.
- Environment (Protection) Act, 1986 (EPA): It gives indirect protection to the mangroves. It empowers the Central government to make various notifications and rules to regulate environmental pollution.
- Coastal Regulation Zone (CRZ) notification: It aims to maintain a balance between development needs and protection of natural resources. CRZ prohibit or regulate certain activities which are harmful for both coastal communities and their environment. It also protects the livelihoods of millions of people through the sustainable management.
- State government efforts: There are several state laws and initiatives that extend protection to mangroves. Eg: The Maharashtra Private Forest Act 1975 and Mission Mangrove campaign.
THREATS TO MANGROVES:
- Change in land-use: Acres of mangrove forest continue to shrink in the face of infrastructure development, urbanisation and agricultural land conversion. Coastal development for tourist developments, shrimp aquaculture, and salt farms leads to clearing of mangroves, dredging, and diking.
- Irresponsible tourism: Mass 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: Mangroves face pollution when municipal wastes and agricultural runoff containing pesticides, antibiotics and other pollutants makes 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 eg: the construction of Farakka Barrage in 1975 has altered fresh water flow around the delta, thereby altering the ecology of Sundarbans.
- Destruction of coral reefs: Coral reefs provide the first barrier against currents and strong waves. When they are destroyed, the strong waves and currents reach the coast and wash away the fine sediment in which the mangroves grow. This can also prevent seedlings from taking root and wash away nutrients essential for mangrove ecosystems.
- 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.
- 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.
- Natural causes: Powerful storms and hurricanes may also severely damage mangrove habitats. Winds, waves, and flooding may be destructive enough to clear entire mangrove islands.
- Weak 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.
- Scientific management: Scientific management practices are essential for conservation and sustainable management of mangrove forests. Governments need to take efforts for the restoration and rehabilitation of degraded mangrove areas, particularly in climate-vulnerable coastal areas.
- Socioeconomic studies: The traditional rights of coastal communities should be recognized while formulating and implementing regulations and conservation measures. For this, socioeconomic studies on the mangrove-dependent people need to be taken up.
- Mapping and planning: Floristic survey of mangroves along the coast is to be taken up to prepare biodiversity atlas for mangroves. Based on this, potential areas are to be identified for implementing the management action plan for mangroves.
- Encourage people’s participation: The participation of the local community should be made compulsory for conservation and management. People’s involvement in mangrove management on public and private lands can greatly aid conservation efforts.
- Encourage private players: Coastal industries and private owners need to be persuaded to actively participate in protecting and developing mangrove biodiversity. Also, incentives for sustainable management of mangroves on private and village community land may be encouraged.
- Promote awareness: Programmes to raise people’s awareness of the importance of mangroves through measures such as exhibitions, seminars, nature camps, and establishment of mangrove parks.
- Ensure minimum flow: every hydel project is under an obligation to release minimum water downstream. However, states should ensure that these norms are followed.
- Research support: Research and international collaboration on problems related to appropriate management of the mangrove ecosystem is vital for the development of scientific conservation plans.
- Alternative livelihood and income generation options like dairy farming, bee keeping, ecotourism and agro-forestry should be encouraged in mangrove-dependent communities.
Q. Discuss the significance of mangroves with special mention of its role in addressing climate change?