- Mangroves represent littoral forest ecosystem generally consisting of evergreen forests that grow in low lying areas of tropical and subtropical regions. They grow below the high water level of spring tides and are highly productive.
- The trees vary in height from 8 to 20 m. They protect the shoreline from the adverse effect of cyclones and tsunamis.
- Mangroves occur in the tropics and subtropics between latitudes 25° N and 25° S.
- They require high solar radiation that helps to filter saline water through their roots. This explains why mangroves are confined to only tropical and subtropical coastal waters.
- They are salt-tolerant so they are also called halophytes. Leaves are thick and also contain salt-secreting glands.
- Since mangroves grow between the land and sea, they represent the best example of ecotone and are a breeding ground for many commercially important fishes.
- They contain a salt filtration system to deal with salt water immersion and wave action.
- They possess pneumatophores (blind roots) to overcome the respiration problem in the anaerobic soil
- Mangroves show Viviparity mode of reproduction which means that seeds germinate in the tree itself before falling to the ground. This is an important adaptive mechanism to overcome the problem of germination in saline water.
- They occur in a variety of configurations. Some species such as Rhizophora send arching prop roots down into the water. While other send vertical “Pneumatophores” or air roots up from the mud. Adventitious roots which emerged from the main trunk of the tree above ground level are called stilt roots.
Prop roots and pneumatophores
Important types of mangroves:
- Red mangroves: They grow along coastlines and are the hardiest among the three major mangrove plant types.
- Black mangroves: They are named so because they consist of dark bark. They usually grow at higher elevations than red mangroves. They have access to more oxygen as their roots are more exposed.
- White mangroves: They grow at higher elevations than the red and black mangroves. Generally, they do not have aerial roots. But sometimes there is unique growth of peg roots when oxygen is depleted due to flood.
Mangroves in India:
- Mangrove forests occupy approx 2 lakh square kilometres across the globe in tropical regions of almost 30 countries. India has a total mangrove cover of around 4,482 sq km which is just 3 % of the world’s mangrove area.
- The mangroves of Sundarbans are the largest single block tidal halophytic mangroves in the world. It is famous for the Royal Bengal Tiger and crocodiles. Here Mangrove areas are being cleared for agricultural use.
- The mangroves of Bhitarkanika which is in Orissa is the second largest in the Indian sub-continent and harbour high concentration of typical mangrove species. Mangrove swamps occur in intertidal mudflats on both sides of Godavari-Krishna deltaic regions of Andhra Pradesh.
- Mangroves of Pichavaram and Vedaranyam are now degraded mainly due to the construction of aquaculture ponds and salt pans.
- On the western coast of India, mangroves are mostly scrubby and degraded and are found along the intertidal region of estuaries and creeks in Maharashtra, Goa and Karnataka.
- The mangrove vegetation in the coastal region of Kerala is very sparse and thin.
- In Gujarat, mangroves are found mainly in Gulf of Kutch and the Kori creek.
- In size, they range from bushy stands of dwarf mangroves found in Gulf of Kutch to taller stands found in the Sunderbans.
- In Andaman & Nicobar Islands there are small tidal estuaries and the lagoons which support dense and diverse mangrove forest.
Importance of Mangroves:
- Mangrove forest creates unique environments which provide ecological niches for a large variety of organisms.
- They have special roots such as prop roots, pneumatophores which help them to impede water flow and thereby enhance the deposition of sediment in areas. They stabilise the coastal shores, provide a breeding ground for fishes.
- Mangroves forest moderate monsoonal floods and reduce inundation of coastal lowlands.
- They protect coastal areas from tsunami, hurricanes and floods.
- Mangroves enhance the natural recycling of nutrients.
- Mangrove supports numerous florae, avifauna and wildlife.
- They provide us woods, firewood, medicinal plants and edible plants to local people.
- They provide various employment opportunities to local communities and augments their livelihood.
- Recent studies show that mangroves store more carbon dioxide than most of the other forests.
Threats to Mangrove:
- They are facing severe threats due to urbanisation, industrialisation, discharge of domestic sewage, industrial effluents and pesticides.
- Saltpans and aquaculture also pose threat to mangroves.
- Nearly 40% of mangrove forests in the Western Coast of India are converted into farmlands and housing colonies in the last three decades.
- Some of the major mangrove species like Bruguiera cylindrica and Sonneratia acida are at the verge of extinction.
- According to a research conducted by the Indian Institute of Science, “India has lost 40% of its mangrove area in the last century mainly due to agriculture, aquaculture, tourism, urban development and overexploitation”.
- There is an urgent need to restore degraded mangroves with the help of governmental action as well as the participation of local communities.
Ways to Conserve Mangroves:
- Suitable sites need to be identified for planting mangrove species. Mangrove nursery banks must be developed for propagation purposes.
- Environmental monitoring in the existing mangrove areas should be done systematically and periodically.
- Potential areas should be identified for implementing the management action plan for mangroves, especially in cyclone-prone areas.
- Various threats to the mangrove resources and their root causes need to be identified so that earnest measures should be taken to eliminate those causes.
- The participation of the local community should be made compulsory for conservation and management purposes.
- Holistic survey of mangroves along the coast is to be taken up to prepare biodiversity atlas for mangroves.
- Coastal industries and private owners should be encouraged to actively participate in protecting and developing mangrove biodiversity.
- The forest officials should be trained on taxonomy, biology and ecology of mangrove species.
Various Effort in India and around the world to conserve Mangrove:
- In 1976 amendment to the Indian Constitution which add Fundamental Duties in which one duty of every citizen of India to protect and improve the natural environment including forests, lakes, rivers and wildlife.
- Government of India set up the National Mangrove Committee to advise about mangrove conservation and development.
- The National Forest Policy, 1988 lists effective conservation and management of natural forest ecosystems which include the mangrove ecosystem as a priority area for forestry research.
- The Indian Forest Act, 1927 and the Wildlife (Protection) Act, 1972 provide protection to flora and fauna. Although they do not specifically mention mangroves but can also apply to the conservation of the flora and fauna of mangrove ecosystems
- The Environment Protection Act, 1986 play a crucial role in the conservation and management of mangrove ecosystems. It declares a Coastal Regulation Zone in which industrial and other activities are restricted in order to protect the coastal environment.
- Many Mangroves sites are protected under the Ramsar Convention at the global level including India.
- The IUCN and The Nature Conservancy have laid down a global scientific map for the purpose of mangrove restoration.
- Mangroves for the Future (MFF) is an initiative by IUCN and the United Nations Development Programme (UNDP). It is also running mangrove restoration and sustainable development projects with gender integration as a core strategy in several Asian countries.
- Strict legislation to protect mangroves is in place in many countries. For example Indonesia
- The organization Global Mangrove Alliance (GMA) is supporting a target of increasing mangrove coverage by 20 percent over current extent by 2030.
- The organizations like the Global Mangrove Watch are working tirelessly towards mangroves conservation.
- Wetlands International also have a reasonable experience in allying with various stakeholders in mangroves conservation. It collaborates with few other organizations the IUCN and the Global Mangrove Alliance (GMA) to work towards mangrove conservation.
- There is a need to work together to address the serious threats to mangrove forests and enable stakeholders like governments, NGOs and coastal communities to sustainably manage them. We need to understand the preciousness of these coastal ecosystems in letter and spirit and work accordingly towards its conservation.
- Periodical monitoring of the mangrove forest is very much necessary to assess the current status. The impact of environmental and human interference on marine flora and fauna needs to be assessed more frequently.
- The traditional rights of coastal communities should also be recognised on a priority basis.
Practice Question for Prelims:
The 2004 Tsunami made people realize that mangroves can serve as a reliable safety hedge against coastal calamities. How do mangroves function as a safety hedge?
- The mangrove swamps separate the human settlements from the sea by a wide zone in which people neither live nor venture out
- The mangroves provide both food and medicines that people are in need of after any natural disaster
- The mangrove trees are tall with dense canopies and serve as an excellent shelter during a cyclone or tsunami
- The mangrove trees do not get uprooted by storms and tides because of their extensive roots.