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India: Scientific management of mangroves is need of the hour

40 per cent of mangrove forests in West Coast of India have been converted into farmlands and housing colonies over the last three decades

Mangroves are salt-tolerant vegetation that grows in intertidal regions of rivers and estuaries. They are referred to as ‘tidal forests’ and belong to the category of ‘tropical wetland rainforest ecosystem’.

Mangrove forests occupy around 2,00,000 square kilometres across the globe in tropical regions of 30 countries. India has a total mangrove cover of 4,482 sq km.

A mangrove ecosystem is the interface between terrestrial forests and aquatic marine ecosystems. The ecosystem includes diversified habitats like mangrove-dominant forests, litter-laden forest floors, mudflats, coral reefs and contiguous water courses such as river estuaries, bays, inter-tidal waters, channels and backwaters.

Mangroves are trees and shrub species that grow at the interface between land and sea in tropical and subtropical regions of the world, where the plants exist in conditions of salinity, tidal water flow and muddy soil.

The structural complexities of mangrove vegetation create unique environments which provide ecological niches for a wide variety of organisms. Mangroves serve as breeding, feeding and nursery grounds for most of the commercial fishes and crustaceans on which thousands of people depend for their livelihood.

Mangroves give protection to the coastline and minimise disasters due to cyclones and tsunami. Recent studies have shown that mangroves store more carbon dioxide than most other forests.

Mangroves are an intermediate vegetation between land and sea that grow in oxygen deficient waterlogged soils which have Hydrogen Sulfide (H2S). They perform important ecological functions like nutrient cycling, hydrological regime, coastal protection, fish-fauna production, etc.

Mangroves act as shock absorbers. They reduce high tides and waves and help prevent soil erosion. They also provide livelihood opportunities to coastal communities.

Sundarbans in the Gangetic delta with an area of 2.12 lakh hectares (ha) supports 26 plant species of mangrove with a maximum height of more than 10 metres. Pichavaram in Tamil Nadu with an area of 1,100 ha supports 12 plant species growing to a height of 5 metres.

Muthupet is the biggest mangrove forest in Tamil Nadu with an extent of 11,885.91 ha with poor species diversity due to lack of fresh water supply. But mangroves are being destroyed and facing severe threats due to urbanisation, industrialisation, and discharge of domestic sewage, industrial effluents and pesticides. Saltpans and aquaculture also pose major threat to the mangroves.

As a result, mangroves get depleted to the tune of 2-8 per cent annually at global level; 40 per cent of mangrove forests in West Coast of India have been converted into farmlands and housing colonies over the last three decades.

Some of the mangrove species like Bruguiera cylindrica and Sonneratia acida are at the verge of extinction. Due to shrimp farming, about 35,000 ha of mangroves have been lost in India.

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