Mangroves
Introduction.
40% of the world’s mangroves are spread in Asia. And the highest loss of mangroves over the last decade is also reported from this region. When considering Sri Lanka, the mangrove system covers an area of 6000-7000ha along the coastline of Sri Lanka. Sri Lanka’s largest mangrove system is in Puttlam Lagoon-Dutch Bay-Portugal Bay complex covering an area of 3385ha. Majority from the rest of mangrove system are spread in Batticaloa and Trincomalee districts. The mangrove forests in Benthota area are highly threatened because of the rapid growth of tourism.
Even with the economic and ecological value of mangroves they have been destroyed for commercial, industrial and household purposes. It is because of the lack of knowledge about the ecological role of the mangroves among the responsible communities. At present because of the lack of attention for conservation and sustainable management of mangroves this eco-system has been destroyed due to indiscriminate clearing and reclamation for industrial, urban, tourist resorts, roads, aquaculture ponds and fishing ports development. Department of Wildlife Conservation and the Coast Conservation Department are operative public institutes for the conservation of mangrove eco-system.
This eco-system is frequently expose to high salinities, high light intensities, low oxygen and strong winds. Although this eco-system exposed to harsh environmental conditions it is one of the most productive wetland eco-system in Sri Lanka. To survive in these harsh conditions and to provide shelters for other mangrove associate organisms these mangroves have developed unique adaptations.
Some of those adaptations are as follows;
Mangroves are rich and diverse natural resource.it has a unique biodiversity. Mangrove system does a major role in maintaining a link between marine and terrestrial eco-systems. This link contributes to maintain the stability of coastal eco-systems like coral reefs, sea grass beds, etc.
This eco-system plays a major role in fisheries industry of coastal areas and lagoons. The waste produce by mangroves are added as nutrients to lagoon water and those nutrients are carried to the coast by tidal waves. Marine microbes use these nutrients as food for them and it is the first step of marine food chain. The shallow intertidal zone around these wetlands provide safe grounds for juvenile fish, crabs, shrimps and molluscs.
Mangroves provide habitats for hundreds of migratory birds. In addition to that monkeys, leopards, water monitors, sea turtles and mudskipper fish use these wetlands.
This unique eco-system is a home to more than 20 true mangrove species of Sri Lanka. The major genera that represent these species are Avicennia, Rhizopora, Bruguiera and Sonneratia. According to the abundance and distribution of mangroves they can be categorized as very common, common and rare.
Very common mangrove species of Sri Lanka are;
Among the mangrove species, species belong to common category are;
Five species of mangrove associated crabs and shrimps have been identified. The mud lobster (Thalassina anomala) is unique to mangrove environment. This lobster can be seen very easily in mangrove system. Birds are the most attractive vertebrates associated with this eco-system. Most common short term residence birds are herons, egrets, cormorants, teals, waders, kingfishers and terns.
The water monitor (Varanus salvator) are most common reptiles associated with mangroves. Estuarine crocodile and mugger crocodile also can be seen in mangrove system in Sri Lanka. Other associated reptiles are Common Bronzeback (Dendrilaphis tristis), Checkered Keelback (Xenochrophis piscator) and common garden Lizard (Calotes calotes).
Mangrove associated mammals are Purple Faced Leaf Monkey (Trachypithecus vetulus), Sri Lanka Golden Palm Cat (Paradoxurus zeylonensis) and Sri Lanka Slender Loris (Loris tardigradus). Mangrove associated carnivorous mammals are Fishing Cat (Prionailurus viverrinus) and Estuarine Otter (Lutra lutra). In addition to these mammals there can be seen bats and small rat species too.
Mangrove associated fish are most important part of the biodiversity of mangroves. There are three main types of fish associated with mangroves. They are freshwater fish, brackish water fish and marine-brackish water migratory fish.
Freshwater fish species are;
One of the most important reason for the mangrove degradation in the past decade is the increase in the demand of shrimps and the practice of destructive production methods in export-oriented industrial shrimp aquaculture. Large number of mangrove forests in North-western coastal belt in Sri Lanka were cleared to establish shrimp farms. One tragic incident of industrial shrimp aquaculture is this process has become a source for water pollution. Use of antibiotics, pesticides, water additives frequently and causing toxicity because of the accumulation of excess feed and feces in pond bottom, cause spread of diseases. So, early ponds closure.
Human settlements in mangrove areas are spread covering the entire coastal belt of Sri Lanka. These human settlements are mainly consisting of permanent and temporary fishing villages. Effluents from these settlements directly affect for the pollution of this ecosystem. These mangrove systems are under restoration for the upliftment of tourism and agricultural purposes. Small percentage of mangrove lands have been acquired by coastal communities illegally. It is a pity that relevant authorities don’t pay attention to this.
Mangrove conservation.
Mangroves are very sensitive for deforestation, pollution and land reclamation. There has been a significant destruction of mangrove eco-systemin the past two decades due to various reasons. Main reason for this is the effects of non-sustainable human activities in and around the mangrove system. Aquaculture, agricultural expansion, water pollution, unregulated disposal of garbage and illegal encroachments are main threats to this unique eco-system. Today mangrove eco-system is facing severe threats and there is a national need to conserve this sensitive eco-system. The most effective solution is aware the community to conserve the mangrove eco-system and its unique biodiversity.
Restoration of mangroves.
The damage caused to the coastal eco-system by Tsunami disaster could affect adversely on the livelihoods of coastal communities. The estimation of damage of the mangrove eco-system in Eastern and Southern coastal areas due to Tsunami is not yet finished.
Restoration means building mangrove habitats in areas where they exist before. However, comparing with other plantations mangrove plants need special environmental conditions to grow. Although there are many methodologies to restore the mangrove eco-system, it is very important to modify methods according to the special needs of the area.
To restore mangrove, community based restoration methods are commonly used. Local communities who fishing near mangrove areas are aware of the importance of mangrove forests as they depend on them for raw materials and services. Department of Wildlife Conservation, Forest Department and Coast Conservation Department implement various programmes to restore mangroves.
As local communities are aware of mangrove eco-system and its relationship with their lives we should let their knowledge to be exchange with other communities in the country to uplift the success of cultivation of mangroves.
It is our responsibility to restore destroyed mangroves forests, protect the remaining mangrove system and use it for the sustainable development of the country.
40% of the world’s mangroves are spread in Asia. And the highest loss of mangroves over the last decade is also reported from this region. When considering Sri Lanka, the mangrove system covers an area of 6000-7000ha along the coastline of Sri Lanka. Sri Lanka’s largest mangrove system is in Puttlam Lagoon-Dutch Bay-Portugal Bay complex covering an area of 3385ha. Majority from the rest of mangrove system are spread in Batticaloa and Trincomalee districts. The mangrove forests in Benthota area are highly threatened because of the rapid growth of tourism.
Even with the economic and ecological value of mangroves they have been destroyed for commercial, industrial and household purposes. It is because of the lack of knowledge about the ecological role of the mangroves among the responsible communities. At present because of the lack of attention for conservation and sustainable management of mangroves this eco-system has been destroyed due to indiscriminate clearing and reclamation for industrial, urban, tourist resorts, roads, aquaculture ponds and fishing ports development. Department of Wildlife Conservation and the Coast Conservation Department are operative public institutes for the conservation of mangrove eco-system.
This eco-system is frequently expose to high salinities, high light intensities, low oxygen and strong winds. Although this eco-system exposed to harsh environmental conditions it is one of the most productive wetland eco-system in Sri Lanka. To survive in these harsh conditions and to provide shelters for other mangrove associate organisms these mangroves have developed unique adaptations.
Some of those adaptations are as follows;
- Presence of aerial roots for absorbing atmospheric oxygen.
- Presence of knee roots, anchor roots and prop roots to anchor in soft soil and to provide support for the tree.
- Allow seeds to grow until they form young roots and shoots while attaching to the parent plant(viviparity).
Mangroves are rich and diverse natural resource.it has a unique biodiversity. Mangrove system does a major role in maintaining a link between marine and terrestrial eco-systems. This link contributes to maintain the stability of coastal eco-systems like coral reefs, sea grass beds, etc.
This eco-system plays a major role in fisheries industry of coastal areas and lagoons. The waste produce by mangroves are added as nutrients to lagoon water and those nutrients are carried to the coast by tidal waves. Marine microbes use these nutrients as food for them and it is the first step of marine food chain. The shallow intertidal zone around these wetlands provide safe grounds for juvenile fish, crabs, shrimps and molluscs.
Mangroves provide habitats for hundreds of migratory birds. In addition to that monkeys, leopards, water monitors, sea turtles and mudskipper fish use these wetlands.
This unique eco-system is a home to more than 20 true mangrove species of Sri Lanka. The major genera that represent these species are Avicennia, Rhizopora, Bruguiera and Sonneratia. According to the abundance and distribution of mangroves they can be categorized as very common, common and rare.
Very common mangrove species of Sri Lanka are;
- Avicennia marina
- Bruguiera gymnorrhiza
- Excoecaria aggalocha
- Lumnitzera racemosa
- Rhizopora mucronata
- Rhizopora apiculata
- Sonneratia caseolaris
Among the mangrove species, species belong to common category are;
- Aegiceras corniculatum
- Avicennia officinalis
- Bruguiera cylindrica
- Bruguiera sexangula
- Ceriops tagal
- Heretiera littoralis
- Pemphis acidala
- Sonneratia alba
- Nypa fruticans
- Lamnitzera littorea
- Xylocarpus granatum
- Scyphiphora hydrophyllaceae
Five species of mangrove associated crabs and shrimps have been identified. The mud lobster (Thalassina anomala) is unique to mangrove environment. This lobster can be seen very easily in mangrove system. Birds are the most attractive vertebrates associated with this eco-system. Most common short term residence birds are herons, egrets, cormorants, teals, waders, kingfishers and terns.
The water monitor (Varanus salvator) are most common reptiles associated with mangroves. Estuarine crocodile and mugger crocodile also can be seen in mangrove system in Sri Lanka. Other associated reptiles are Common Bronzeback (Dendrilaphis tristis), Checkered Keelback (Xenochrophis piscator) and common garden Lizard (Calotes calotes).
Mangrove associated mammals are Purple Faced Leaf Monkey (Trachypithecus vetulus), Sri Lanka Golden Palm Cat (Paradoxurus zeylonensis) and Sri Lanka Slender Loris (Loris tardigradus). Mangrove associated carnivorous mammals are Fishing Cat (Prionailurus viverrinus) and Estuarine Otter (Lutra lutra). In addition to these mammals there can be seen bats and small rat species too.
Mangrove associated fish are most important part of the biodiversity of mangroves. There are three main types of fish associated with mangroves. They are freshwater fish, brackish water fish and marine-brackish water migratory fish.
Freshwater fish species are;
- Striped Rasbora (Rasbora daniconius)
- Giant Danio (Danio malabaricus)
- Horandandiya (Horandandiya athukorali)
- Barbs (Puntis spp.)
- Walking Catfish (Clarius brachysoma)
- Ambassids (Ambassis spp.)
- Pony fish (Leiognathus spp.)
- Mone (Monodactylus argenteus)
- Target fish (Therapon jubua)
- Mudskipper (Periopthalmus koelrenteri)
- Milkfish (Chanos chanos)
- Snappers (Lutjanus spp.)
- Trevally (Caranx spp.)
- Silver belly (Gerres spp.)
- Surgeon fish (Acanthurus spp.)
- Barracuda (Sphyraena spp.)
One of the most important reason for the mangrove degradation in the past decade is the increase in the demand of shrimps and the practice of destructive production methods in export-oriented industrial shrimp aquaculture. Large number of mangrove forests in North-western coastal belt in Sri Lanka were cleared to establish shrimp farms. One tragic incident of industrial shrimp aquaculture is this process has become a source for water pollution. Use of antibiotics, pesticides, water additives frequently and causing toxicity because of the accumulation of excess feed and feces in pond bottom, cause spread of diseases. So, early ponds closure.
Human settlements in mangrove areas are spread covering the entire coastal belt of Sri Lanka. These human settlements are mainly consisting of permanent and temporary fishing villages. Effluents from these settlements directly affect for the pollution of this ecosystem. These mangrove systems are under restoration for the upliftment of tourism and agricultural purposes. Small percentage of mangrove lands have been acquired by coastal communities illegally. It is a pity that relevant authorities don’t pay attention to this.
Mangrove conservation.
Mangroves are very sensitive for deforestation, pollution and land reclamation. There has been a significant destruction of mangrove eco-systemin the past two decades due to various reasons. Main reason for this is the effects of non-sustainable human activities in and around the mangrove system. Aquaculture, agricultural expansion, water pollution, unregulated disposal of garbage and illegal encroachments are main threats to this unique eco-system. Today mangrove eco-system is facing severe threats and there is a national need to conserve this sensitive eco-system. The most effective solution is aware the community to conserve the mangrove eco-system and its unique biodiversity.
Restoration of mangroves.
The damage caused to the coastal eco-system by Tsunami disaster could affect adversely on the livelihoods of coastal communities. The estimation of damage of the mangrove eco-system in Eastern and Southern coastal areas due to Tsunami is not yet finished.
Restoration means building mangrove habitats in areas where they exist before. However, comparing with other plantations mangrove plants need special environmental conditions to grow. Although there are many methodologies to restore the mangrove eco-system, it is very important to modify methods according to the special needs of the area.
To restore mangrove, community based restoration methods are commonly used. Local communities who fishing near mangrove areas are aware of the importance of mangrove forests as they depend on them for raw materials and services. Department of Wildlife Conservation, Forest Department and Coast Conservation Department implement various programmes to restore mangroves.
As local communities are aware of mangrove eco-system and its relationship with their lives we should let their knowledge to be exchange with other communities in the country to uplift the success of cultivation of mangroves.
It is our responsibility to restore destroyed mangroves forests, protect the remaining mangrove system and use it for the sustainable development of the country.
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