Depletion of Mangroves and Causes, Their importance in maintaining coastal ecology

Mangrove forests form a unique wetland ecosystem, inhabiting the edge of land and sea, thriving in seawater. Over the past four decades, 35% of global mangrove forests have been destroyed. This degradation of mangrove forests has a knock-on effect on some of the world’s most endangered species which rely on them for habitat, such as the proboscis monkey and the Bengal tiger. 

Causes of depletion of mangroves 

The natural causes 

• Cyclones, typhoons and strong wave action, especially in the geographically vulnerable Andaman and Nicobar Islands; 

• Browsing and trampling by wildlife (e.g. deer) and livestock (goats, buffaloes and cows), which are often left to graze freely, especially in the areas close to human habitation; 

• Damage by oysters to the young leaves and plumules of Rhizophora and Ceriops plants; crabs, which attack young seedlings, girdle the root collars and eat the fleshy tissues of the propagules 

• Insect pests, such as wood borers, caterpillars (which eat the mangrove foliage and damage the wood as well) and beetles; 

Anthropogenic causes 

• Anthropogenic activities, such as construction of houses and markets causing soil erosion and soil sedimentation has led to their destruction. For example, in Sunder-bans collection of tiger prawn seeds for trade has greatly affected the other animals found in these forests. 

• Indiscriminate tree felling and lopping, mainly for fuel wood, fodder and timber, especially in the areas close to human habitation. 

• Indiscriminate conversion of mangroves on public lands for aquaculture (e.g. for prawn culture at Chorao, Goa), agriculture, mining (e.g. along the Mapusa estuary in Goa), human habitation and industrial purposes. 

• Encroachment on publicly owned mangrove forest lands, e.g. cultivation of paddy observed on government land, which involved uprooting of natural and planted seedlings; 

• Lack of interest of private landowners (village communities and individuals) in conserving and developing the mangroves on their lands. 

• Illegal large-scale collection of mangrove fruits for production of medicines, which hinders their natural regeneration. 

• Discharge of industrial pollutants into creeks, rivers and estuaries, which is a major problem in some regions of the world. 

Importance of mangroves in maintaining coastal ecology 

• Mangrove plants have (additional) special roots, such as prop roots, pneumatophores which help to impede water flow and thereby enhance the deposition of sediment in the areas (where it is already occurring), stabilize the coastal shores, provide a breeding ground for fishes. 

• Provide a safe and favorable environment for breeding, spawning, rearing of several fishes. 

• They supply woods, firewood, medicinal plants and edible plants to local people.

• Mangroves moderate monsoonal tidal floods and reduce inundation of coastal lowlands. 

• They prevent coastal soil erosion. 

• They protect coastal lands from tsunami, hurricanes and floods. 

• Mangroves enhance the natural recycling of nutrients. 

Mangrove forests play a major role with more valuable ecological services. Therefore, conservation of the same is the need of the hour not only for the coastal biodiversity but also for well-being of the mankind.