What are mangroves?
Mangroves are trees that exist in very unique conditions in which most trees would not survive. They exist in tropical regions which are salty, in coastal waters where they experience constant flooding and retreating of tides. There are around 80 different species of trees which grow in low-oxygen soil. Since these mangrove forests cannot handle cold and freezing temperatures, they only exist in tropical and subtropical latitudes near the equator. There are three 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
In the entire world, mangroves are the only species of trees that can not only handle saltwater but thrive in it. These unique mangrove trees have a trick up their sleeves to deal with excess salt. They have waxy leaves which help in excreting all the excess unrequired salt!
Most mangrove forests have a thick tangle of prop roots that make the trees appear to be standing on stilts above the water. This tangle of roots allows the trees to handle the daily rise and fall of tides, which means that most mangroves get flooded at least twice per day. The roots also slow the movement of tidal waters, causing sediments to settle out of the water and build up the muddy bottom.
Types of Mangroves
Mangrove forests can be found on the saltwater coasts of 118 tropical and subtropical countries, totalling more than 137,000 square kilometres (85,000 square miles). The largest area of mangrove forests are found in Indonesia, which consist of around 23,000 square kilometres of area.
It has been estimated that around 50-110 species of mangrove trees exist which vary in several features. Mangrove trees range in height from 2 to 10 meters, some have oblong leaves whereas some have oval. However, all prefer and thrive in regions with brackish water.
Importance of mangroves
Mangroves provide a variety of ecological benefits.
1. Essential habitat
Due to their diverse features, mangroves provide a home for a diverse array of terrestrial organisms as well as various coastal species of fish which rely on mangrove grounds for being able to breed, spawn and hatch. Their underwater roots act as nursing grounds for a range of various juveniles of fish species including 1-inch gobies to 10-foot sharks.
2. Carbon Sinks
Mangroves act as important carbon sinks by absorbing and storing up to 10 times more carbon than terrestrial ecosystems. With the current threat of climate change mangroves prove to be very important habitats in the fight against climate change.
3. Natural Barriers
The thick, impenetrable roots of mangrove forests are vital to shoreline communities as natural buffers against storm surges, an increasing threat in a changing global climate with rising sea levels. They stabilise the coastline and reduce the natural erosion which is caused due to storms, waves and tides. This plays a major role in protecting coastal areas from natural disasters like Tsunamis, as the mangrove trees complex root systems dissipate sea wave energy.
4. Local livelihood
Mangroves are an important source of livelihood for local communities found in and around mangrove forests. Various activities such as honey collection, tanning, wax collection and fishing have been sustaining these communities living around mangroves for centuries.
Mangroves are under threat nearly everywhere. Because of their high salt tolerance, mangroves are often among the first species to colonize mud and sandbanks flooded by seawater, but an increase in coastal development and altered land use led to a decline in global populations. Several species are listed as vulnerable or endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.
Mangroves in Myanmar are in major threat as the rate of deforestation is four times the global average. Shrimping is the major cause of the problem. In Thailand, Mexico and Indonesia, mangroves are often cut down to make room for temporary shrimp pens. But once the pens have been removed, the accumulated bio-waste renders the water too toxic for most forms of life.
Climate change is the biggest threat being faced by the Mangroves in India. Increase in temperatures, carbon dioxide concentration, rise in sea levels and extreme weather events like cyclones and droughts, are predicted to have deleterious effects on Indian mangroves. Sea level rise is probably the greatest threat facing coastal mangroves. Recent studies have shown that larger changes in sea level can lead to mangrove ecosystem collapse.
Pollution is on the rise in highly populated coastal metro cities like Mumbai, Chennai and Calcutta which face increased pollution load resulting in the decrease in mangrove cover. Mangroves in Maharashtra are almost extinct now due to continuous human exploitation.
Mangroves of India
India has 3% of the total mangrove cover in South Asia. Mangrove Cover in India is 4975 sq. km (0.15% of the total geographical area.) According to the Forest Survey of India, 2019, Mangroves’ cover in the country increased by 54 sq. km (91.10 %) in comparison to the 2017 assessment. The significant points put across by the State Forest Report 2019: Mangrove cover is divided as:
- Very Dense – 1476 sq. km (29.66 %)
- Moderately Dense – 1479 sq. km (29.73%)
- Open Mangroves – 2020 sq. km (40.61 %)
West Bengal has 42.45% of India’s mangrove cover which is the highest in the country. The Sundarbans in West Bengal is the largest mangrove in the world and is also a UNESCO World Heritage Site and is home to over 180 species of trees and plants.
The major mangroves in India are found at:
- Sundarban Groves
- Mahanadi Mangroves
- Krishna Godavari Mangroves
- Mangroves of Gujarat
- Ratnagiri Mangroves
- Goa Mangroves
- Cauvery Deltaic Mangroves
- Krishan-Godavari Mangroves
- Andaman Nicobar Mangroves
Conservation of Mangroves in India
The State Forest Report 2019 mentions the following conservation techniques for conservation of Mangroves in India:
- The state of Gujarat uses direct seed sowing, raised bed plantations, and fishbone channel plantations to restore degraded mangroves.
- State of Andhra Pradesh has established Eco-Development Committees and Van Samrakshan Samithi to implement conservation projects in mangrove areas.
- The state of Maharashtra has been implementing restoration, protection, regeneration, and maintenance techniques to conserve mangroves.