Mangrove Forests of Coastal India

Introduction

Mangroves refer to a congregation of salt-tolerant (halophytes) plants (trees and shrubs) in the coastal intertidal region with slow-moving water and low oxygen soil. These plants grow luxuriantly in the places where freshwater mixes with saline water (seawater)and where sediment is composed of accumulated mud deposits.

Mangroves provide an array of ecosystem services such as phytoremediation (removal of nutrients, and heavy metals), stabilizing the coastline, and reducing erosion from storm surges, currents, waves, and tides. Mangroves vegetation aid as a green wall, a natural infrastructure, and protects human habitations by preventing erosion and absorbing storm surge impacts during extreme weather events such as cyclones and tsunami. Mangroves contain a complex salt filtration (filter Na⁺ ions) system and a complex root system to cope with salt water immersion and wave action. The intricate root system provides habitat and protects fish and other organisms from predators. The dense tangle of prop roots or stilt roots helps in respiration. Stilt roots allow the trees to handle the daily rise and fall of tides and moderate the movement of tidal waters, causing sediments to settle out of the water and build up the muddy bottom.

Mangrove forests are productive ecosystems that sequester and store carbons, which helps mitigate climate changes. Studies in the west coast of Karnataka reveal that mangrove forests with native diverse species have two to three times the net carbon sequestering capability compared to tropical forests, making mangrove ecosystems a vital player in combat climate change.

As leaves drop into the water with lower oxygen levels, these leaves serve as a primary food source for various animals like worms, shrimp, fish and crabs, which help transport carbon to deeper water, and eventually, carbon remains trapped indefinitely. Mangroves ecosystems adapt and are resilient to extreme weather changes and consequences of rising sea levels with global warming. This necessitates the restoration of degraded mangrove patches involving local stakeholders with regular monitoring to ensure that growing conditions are apt for the species.

The current issue of Sahyadri e-news (Issue LXXIX) authored by Prof. Kathiresan presents Mangrove forests of coastal India. India has the richest mangrove biodiversity globally and harbors 54% of true mangroves, that is 43 out of 80 global species and 85 species of mangrove associates. Sundarbans with humid and wet conditions have high biodiversity, and the Andaman & Nicobar Islands have India's third-largest mangrove forest, occupying 12.3% of the total cover, and are located in low energy tidal coast in humid and wet conditions with rich biodiversity. Though the mangrove cover is increasing due to the conservation efforts, a large area of mangroves is still poor, with less than 40% canopy density. This emphasizes the need for integrated approaches for managing mangrove forests prudently involving local people to counter the growing threat of climate change.