This is a simple guide that lists out the most popular questions related to mangroves, to understand what they are and their ecological significance. Please click on a topic for detailed information.
- What are mangroves?
- What is special or unique about them?
- How are mangroves classified?
- Why are they important?
- Where are mangroves found globally?
- Where are mangroves located in India?
- Which plant and animal species do the mangroves support?
- What is the current status of mangroves in India?
- What are the threats that mangrove ecosystems face?
- Are there any policies directed at protection and conservation of mangroves?
- What are the efforts made to protect and conserve mangroves in India?
- Are there any success stories on mangrove restoration?
- What needs to be done to preserve mangroves in the future in India?
Have you noticed near the coastlines short trees or bushes with a dense tangle of roots hanging out that makes them look like they are standing on stilts? These are mangroves. Mangroves can be trees, shrubs, ferns and palms that occupy the boundary between the land and the sea. They mainly grow in or adjacent to areas between the high tide and the low tide. They get regularly covered or immersed in water at high tide and exposed to air at low tide.
The roots of mangroves are regularly exposed to saline water. At times, they are also exposed to freshwater surface runoffs and flooding. Mangroves get their nutrition from these tidal saline and freshwater resources and coastal soils and silt that get deposited from the surrounding land after an erosion.
Do you know that mangroves are remarkably adaptive to harsh conditions?
Some interesting facts
- Mangroves can cope with high amounts of salinity by excreting salt through their leaves or by storing it within their tissues.
- They have special roots that stick above the ground called breathing roots or pneumatophores that are partly exposed to the air. This helps them breathe during frequent floods or when there is low oxygen in the environment.
- Their well-developed root systems also help them to anchor firmly on sediments so that they do not get pushed around during tides and waves. In some mangrove species, roots travel some distance away from the main stem and branches and penetrate the soil to provide physical support to the plants. These are called stilt roots. These roots have numerous pores on their surface through which they can take in oxygen.
- Harsh conditions make germination of mangrove seeds difficult. Mangroves have coped with this through a unique way of reproduction known as vivipary where seeds germinate and develop into seedlings while still being attached to the parent tree! The parent tree supplies water and nutrients and the seedlings float in the water only to develop roots when they find suitable soil to establish themselves.
There are various classifications done for mangroves. One classification puts them into two categories—true mangroves and semi mangroves or mangrove associates. Semi mangroves are those species that grow at the periphery of mangrove regions.
Mangroves have also been classified based on three regional factors—(i) geophysical (sea level changes, climatic conditions and tide characteristics of the region), (ii) geomorphological (sediment characteristics, characteristics of waves, tides, rivers and the intertidal zone of the region) and (iii) biological.
Mangrove forests are also classified into overwash, fringe, riverine, basin, hammock and scrub or dwarf based on the mean sea level, hydrology, and forest characteristics of the region. More recently, a simplified classification based on where the mangrove forests are located like riverine, fringe, and basin has been proposed for mangroves.
Indian mangroves have been categorised based on coastal habitats into:
Another type of classification is based on geomorphological characters and includes:
- East coast mangrove habitats
- West coast mangrove habitats
- Andaman and Nicobar and Lakshadweep islands
Based on tidal range, Indian mangroves have also been classified into (i) swampy mangroves situated below the high tidal level and submerged by sea water twice a day and (ii) tidal mangroves submerged only during spring tide and sometimes by sea waves.
Mangrove forests not only provide food security and livelihoods to the coastal communities but also provide ecosystem services worth $1.6 billion each year. They provide feeding and breeding grounds for crabs, prawns, mollusks, fish, birds, reptiles and mammals and are important sources of firewood, timber, cattle feed, honey and medicines. They protect groundwater aquifers from mixing with seawater and play an important role in removing coastal pollution due to toxic heavy metals. They also guard against natural calamities like tsunamis, storms and floods.
Mangroves are spread over 123 countries and territories worldwide in tropical and subtropical regions. They are most extensively found in Asia, Africa and South America. South Asia has 6.8 percent of the world’s mangrove cover of which India has 45.8 percent of the total mangrove cover.
India is the third richest country for mangrove biodiversity in the world after Indonesia and Australia and has about 3.3 percent of the global mangrove forest cover. Out of eight states and union territories which support mangroves, West Bengal (2,115 sq. km), Gujarat (1,031 sq. km), Andaman and Nicobar Islands (966 sq. km), Andhra Pradesh (397 sq. km), and Odisha (215 sq. km) have the maximum areas of mangroves.
7. Which plant and animal species do the mangroves support?
India has the highest recorded biodiversity among mangrove forests. For example, the largest population of birds and crocodiles, especially albino crocodiles, is found in Baitarnika, Odisha. The world’s largest nesting site for the Olive Ridley turtles is found along the Gahirmatha coast of Odisha. Besides this, mangroves have seagrass meadows that support unique animals such as the seacow or Dugong. Many ornamental fish nesting in coral reefs are also commonly found in mangrove ecosystems in India. Mudflats associated with mangrove ecosystems in India support a large variety of migratory and residential birds.
The graph below shows the different kinds of plants and animal species that occupy Indian mangrove forests.
According to the recent Forest Survey of India, Dehradun report, there has been an increase in the mangrove cover in the country. At the state level, the mangrove cover has shown a decrease in the states of Andhra Pradesh and Andaman and Nicobar Islands while they have increased in the states of Gujarat, Maharashtra, Tamil Nadu, Odisha, Goa, Karnataka, Kerala, Daman and Diu and Puducherry.
One-third of the world’s mangrove forests have been lost over the last 50 years! The greatest threat has been from shrimp aquaculture ponds. These have led to mangrove area losses between 20 to 50 percent. A 25 percent decline in mangroves is projected by 2025 due to the shrimp industry in developing countries.
Besides this, aggressive urbanisation leading to the conversion of landscapes for urban infrastructure projects like dams, ports, road constructions, activities such as agriculture and salt farming, growth in tourism, mining, refineries, oil pipeline passages etc is taking a toll on mangrove ecosystems. At the same time, changes in hydrology, increasing salinity, pollution and over-exploitation of coastal areas, siltation, cattle grazing etc are also posing a threat to mangroves.
The National Policy 2006 recognises mangroves as important coastal environmental resources that need protection. The National Environment Policy highlights the need to mainstream sustainable management of mangroves into the forestry sector and adopt a comprehensive approach to Integrated Coastal Zone Management.
For example, mangroves located near notified forest areas are covered under the Forest (conservation) Act, 1980, which encourages the judicial use of resources while the National Forest Policy of 1988 encourages community participation in management, protection and regeneration of mangroves.
The National Conservation Strategy and Policy Statement on Environment and Development (1992), National Forest Policy and National Wildlife Action Plan highlight the importance of conservation and sustainable use of mangroves.
India formulated a national plan for conservation of mangroves following a Ramsar Convention in 1971. The National Mangrove Committee was also set up then to promote scientific assessment and evaluation of mangrove habitats.
The Government of India has designated special Marine and Coastal Protected Areas to protect marine ecosystems, especially mangroves. Marine ecosystems in Islands are considered as Category II (MoEF, GoI, 2008) and aim at preserving biodiversity, genetic diversity and conserve and maintain the ecological processes.
The Ministry of Environment, Forest and Climate Change (MoEFCC, then MoEF) put restrictions on the expansion of shrimp farming in February 1991. The Coastal Regulation Zone (CRZ) noti?cation under the Environmental Act, 1986, has declared all coastal stretches of seas, bays, and estuaries up to 500 m from the high tide line on the landward side as CRZ. The state governments have prepared and enforced the coastal zone management plans in 1991 following the Supreme Court order.
However, ineffective implementation of policies and laws and inadequate mechanisms to protect mangroves from the current threat of climate change hinders progress.
Community-based management efforts in conserving mangroves by involving scientific bodies and the forest department are also being practised in states like Tamil Nadu, Orissa, West Bengal and Gujarat.
A number of positive examples in India demonstrate best practices of conservation and management of mangroves. These include:
- Canal Bank planting with “Fish Bone” design for mangrove restoration in Tamil Nadu and Andhra Pradesh
Mangroves in Andhra Pradesh and Tamil Nadu face the risk of degradation due to high salinity of dry soil and a lack of regular tidal flushing. M.S. Swaminathan Foundation and the forest department have come up with this unique technique based on the formation of canals that was implemented between 1986 and 2002 that led to an increase in mangrove cover. It ensures that the high saline soil continues to remain moist due to regular tidal waves, leaches out salts and becomes suitable for mangrove restoration.
- Maharashtra Mangrove Conservation Model
The Government of Maharashtra constituted the “Mangrove Cell” in 2012 and the “Mumbai Mangrove Conservation Unit” in 2013 to protect mangroves in and near Mumbai and changed the status of mangrove forests on government land from “protected forests” to “reserved forests”. As a result, 15,088 hectares of mangrove forests have now been classified as “reserved forests” in seven districts of Maharashtra.
- Kannur Mangrove Mission
Under the initiative, “Mission Mangrove Kannur” was taken up by the district collector, Kannur (Kerala) in 2014, along with the forest department to survey, notify and save mangroves of the district.
- Participatory mangrove management in the states of Tamil Nadu, Odisha, Andhra Pradesh, West Bengal and Gujarat
Under this initiative, the M. S. Swaminathan Research Foundation undertook the Joint Mangrove Management (JMM) programme for restoration and conservation of mangroves through the participation of local people along with the forest departments from 2001 to 2006.
Read more about the efforts here
- Economic valuation and restoration of ecosystem services of the mangroves
- Provision of alternative livelihoods to mangrove ecosystem-dependent communities to prevent their further deterioration
- More community involvement in the efforts to preserve mangroves
Read more about it here