Mangrove Forests in India

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Mangrove Forest in India

According to FAO, mangroves are the characteristic littoral plant formation of tropical and subtropical sheltered coastlines. Mangroves are trees and bushes growing below the high water level of spring tides which exhibits remarkable capacity for salt water tolerance.

A Mangrove is a small tree or shrub that grows along coastlines, taking root in salty sediments, often underwater.
According to Champion & Seth Classification (1968), Mangroves are included in Type Group- 4 Littoral & Swamp Forests.
They are most often found straddling the equator between 25° North and South latitude.

About 42 percent of the world’s mangroves are found in Asia, with 21 percent in Africa, 15 percent in North and Central America, 12 percent in Australia and the islands of Oceania, and 11 percent in South America.
Mangroves are flowering trees, belonging to the families Rhizophoraceae, Acanthaceae, Lythraceae, Combretaceae, and Arecaceae.
The upper trunk, including the branches and leaves, of a mangrove tree lives completely above the waterline, while the lower trunk and the large root system are partly covered by seawater.
Many species have roots diverging from stems and branches and penetrating the soil some distance away from the main stem (like banyan trees).
There are types of Mangroves:
- Red – Found along the coastlines
- Black – Major feature of such mangrove trees is their dark bark. They have access to more oxygen.
- White – Compared to Red and Black mangroves; they grow at the highest elevation.
According to India’s 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.

More than 40% of the total area of Mangroves was reported in just four countries : Indonesia (19% of the total), Brazil (9%), Nigeria (7%), Mexico (7%).
Top 3 states showing mangrove cover increase: Odisha (8 sq km), Maharashtra (4 sq km), and Karnataka (3 sq km).

features of mangroves

A speciality of mangroves is that they can survive under extreme hostile environment such as high salt and low oxygen conditions. Mangrove trees contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action. The roots filter out 90% of the salt they come into contact with in the saline and brackish water they call home. Some species of mangrove excrete salt through glands in their leaves.
Underground tissue of any plant needs oxygen for respiration. But in a mangrove environment, the oxygen in soil is limited or nil. Hence the mangrove root system absorbs oxygen from the atmosphere. Mangroves have special roots for this purpose called breathing roots or pneumatophores(blind roots). These roots have numerous pores through which oxygen enters the underground tissues.
Survival in Extreme Conditions: With their roots submerged in water, mangrove trees thrive in hot, muddy, salty conditions that would quickly kill most plants.
They require high solar radiation and have the ability to absorb fresh water from saline/brackish water.
It produces pneumatophores (blind roots) to overcome respiration problem in the anaerobic soil conditions.
Mangroves, like desert plants, store fresh water in thick succulent leaves. A waxy coating on the leaves seals in water and minimises evaporation.
Mangroves are viviparous – their seeds germinate while still attached to the parent tree. Once germinated, the seedling grows into a propagule. The mature propagule then drops into the water and gets transported to a different spot, eventually taking root in a solid ground.

Significance of Mangroves

Mangrove trees are, in fact, the only species of tree in the world that are able to deal with the salt water. That’s why mangroves are generally found growing along coastlines. In order to live there, they need to be able to tolerate salt water. So this is the unique quality that mangroves possess.

Mangrove trees also acts as a natural storm barriers along coastlines. They put their roots deep down in the soil and so help prevent storm surges and lock in coastlines, preventing erosion.
Mangroves moderate monsoonal tidal floods and reduce inundation of coastal lowlands. It prevents coastal soil erosion.
It protects coastal lands from tsunami, hurricanes and floods.
As per the study conducted in 2016, mangrove trees are one of the best trees in the world for absorbing carbon dioxide, a greenhouse gas. Sadly, it’s believed that approximately 122 million tons of carbon was released due to mangrove losses around the globe.
Mangroves trees also provide shelter for many aquatic species. There are thousands of fish species that depends directly on mangroves around the world for habitat. Many people who live near coastlines rely on these mangroves for fishing.

There are 35 different species of mangrove tree around the world. The four most common ones are black mangroves, white mangroves, buttonwood mangroves and red mangroves. Depending on the species type, mangroves can grow to be small shrubs or 40-foot trees.
Dense roots of Mangroves inhibit the flow of tidal water and encourage the deposition of nutrient-rich sediments. But once lost, mangroves are very difficult to replant due to the shifts in the very sediments the roots helped keep in place.
Mangroves are considered as the most important ecosystems in the world. Taken together, they help keep the climate stable, coastlines safe, provide food for fish, birds, and humans alike, create vital habitat for various species.
Mangroves enhance natural recycling of nutrients.
Mangrove supports numerous flora, avifauna and wild life.

It provides numerous employment opportunities to local communities and augments their livelihood.

How do mangrove forests help protect against strong cyclones?

Mangrove forests act as natural barriers against storm surge, coastal flooding and sea level rise. Their intricate root system stabilises the coastline, reducing erosion from storm surges. Together with the tree trunks, they work like speed-breakers to slow down the tides.
They protect shorelines from damaging winds and waves. A series of studies in the early 2000s discovered that mangroves with an average height of 6-10 metres could shorten a cyclone’s waves by 60%.
Mangroves also help prevent erosion by stabilising sediments with their tangled root systems.
A 2013 study of mangroves in Florida estimated that a mangrove forest could reduce the effects of a Category 5 storm to the intensity and effects of a Category 3 storm.

What are the other benefits of Mangrove Forests to the environment?

Water Purification: Mangroves improve the water quality by absorbing nutrients from runoff that might otherwise cause harmful algal blooms offshore. Both coral reefs and seagrass beds rely on the water purifying ability of mangrove forests to keep the water clear and healthy.
Storing Blue Carbon: Mangroves make up less than 2% of marine environments but account for 10-15% of carbon burial. Once the leaves and older trees die they fall to the seafloor and take the stored carbon with them to be buried in the soil. This buried carbon is known as “blue carbon” because it is stored underwater in coastal ecosystems like mangrove forests, seagrass beds and salt marshes.
Supporting Biodiversity: The mangrove ecosystem also supports an incredible diversity of creatures including some species unique to mangrove forests. They provide habitat and refuge to a wide array of wildlife such as birds, fish, invertebrates, mammals and plants.
Many people living in and around mangroves depend on them for their livelihood. The trees are a source of wood for construction and fuel. The ecosystem provides local fishermen with a rich supply of fish, crabs and shellfish. The ecosystem also supports tourism.

Important Wetlands In India

Mangrove Cover Assessment 2021

SUNDARBANS MANGROVE FOREST, WEST BENGAL

Sundarbans in West Bengal are the largest mangrove regions in the world.

A UNESCO World Heritage Site, Sundarbans is densely populated by mangroves and is home to the Royal Bengal Tigers.
The forest is also home to more than 180 species of trees and plants.
Besides, Gangetic dolphins and estuarine crocodiles are also its popular residents.

Pichavaram Mangrove Forest, Tamil Nadu

Counted among the largest mangrove forests in India, Pichavaram mangrove is situated close to Chidambaram in Tamil Nadu.
The whole region is exquisitely scenic and houses a large number Aquatic birds.
Separated from the sea by a vast stretch of the sandbar, this forest attracts many adventure-seeking travelers because of its backwaters of the Vellar and Coleroon rivers.
Mangroves of Pichavaram and Vedaranyam are degraded mainly due to construction of aquaculture ponds and salt pans.

Godavari – Krishna Mangrove Forest, Andhra Pradesh

Mangrove swamps occur in profusion in the intertidal mudflats on both side of the creeks in the Godavari Krishna deltaic regions of Andhra Pradesh.
The forest is under protection for Calimere Wildlife and Pulicat Lake Bird Sanctuary and is home to some rare animal species and aquatic birds.

Flamingoes and egrets are an annual visitor here.

Bhitarkanika Mangrove Forest, Odisha

The forest is created by the two river deltas of River Brahmani and Baitarani.
It is one of the most significant Ramsar wetlands in India.

Baratang Island Mangrove Forest, Andamans

Baratang Island Mangroves are situated around 100 kilometers away from the capital of Andaman and Nicobar Islands, Port Blair.
With a total mangrove cover in the Andaman archipelago standing at 616 square kilometers, it is a part of the North and Middle Andaman administrative district.
Around 65 percent of the forest features in the category of very dense mangroves.
In the form of pristine beaches, vast mangrove creeks, and mud volcanoes, Baratang is endowed with abundant natural beauty.

Gulf Of Kutch Mangroves

In Gujarat (north-west coast) mangroves Avicennia marine, Avicennia officinalis and Rhizophora mucronata are found mainly in Gulf of Kachchh and the Kori creek.

Mangroves are of scrubby type with stunted growth, forming narrow, discontinuous patches on soft clayey mud.
The condition of the mangroves is improving especially in the Kori creek region, which is a paleodelta of the Indus river.
In size, mangroves range from bushy stands of dwarf mangroves found in Gulf of Kuchchh, to taller stands found in the Sunderbans.
The second-largest mangrove forest in India, the mangrove forest in Gujarat covers approximately 1,175 square kilometers of land.

What are the threats to mangroves?

They are destroyed for conversion of area for agricultural purpose, fuel, fodder and, salinization, minig, oil spills, aquacultural (shrimp farming), use of chemical pesticides & fertilizers, industrial purposes.
Scientists estimate that at least one third of all mangrove forests has been lost during the last few decades. Coastal development, including construction of shrimp farms, hotels, and other structures, is the primary threat to mangroves.
Mangrove forests are cleared to make room for agricultural land and human settlements.
Mangrove trees are used for firewood, construction wood, charcoal production, and animal fodder. In some parts of the world, there has been overharvesting which is no longer sustainable.
Overfishing, pollution, and rising sea levels are the other threats to mangrove forests and their ecosystem.

Biosphere Reserves Of India

Conservation of Mangroves

Mangrove conservation efforts are largely aimed at preventing destruction of mangrove ecosystems, and increasing coverage.
A key issue is not just destruction but degradation of mangrove ecosystems, through pollution, siltation, changes in salinity or loss of biodiversity.
The Sundarbans mangroves, located in the Bay of Bengal (partly in India and partly in Bangladesh), were the first mangroves in the world to be put under scientific management. The area’s first management plan was implemented in 1892.
Appreciating the importance of Mangroves, the Government of India set up a National Mangroves Committee in 1976 to advise the Government on issues related to the conservation and development of Mangroves in the country.

Source : ISFR 2021

Also refer :

Mangrove Forest in India

features of mangroves

Significance of Mangroves