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Threats of Wetlands in Sri Lnaka

A majority of the wetlands in Sri Lanka are facing various threats that are posed by harmful human activities. An analysis of the identified threats pertaining to the wetlands listed for Sri Lanka in the Directory of Asian Wetlands (Scott, 1989) brings out some very interesting information. The most frequently reported threat appears to be siltation. It should be realized that this is usually not caused by factors in the wetland itself but by actions on lands adjacent or away from the wetland. The development of aquaculture poses serious threats to wetlands. Since the white spot attack, the rate of conversion has changed to a situation where most ponds been abandoned, thus leaving many desolate areas. The future threat of conversion still looms due to the high price of shrimp. The present broad threats can be summarized under four major categories; habitat deterioration/ degradation, direct loss/exploitation of species, spread of invasive alien species and natural phenomena.

Habitat deterioration/degradation:Several factors have resulted in the deterioration and degradation of the quality of wetlands, which are highlighted in following table.

Causes of habitat deterioration/degradation and resultant impacts
Contributory Factors Impacts Affected wetlands
Reclamation Loss of wetlands and their biodiversity Urban Marshes(eg.Bellanwila-Attidiya,Muthurajawela)
Clearing of vegetation Loss of habitats and species Mangroves (eg. Mangroves in the Coastal areas of the Puttalam District)
Water pollution
Organic pollution
Other Chemical effluents
Sewage disposal

Loss of species
Loss of species, Harmful effects on humans
Eutrophication, Spread of harmful diseases

Marshes (eg. Muthurajawela)
Rivers (eg. Kelani river)
Tanks, Marshes, Estuaries (eg. Parakrama Samudraya, Beira lake)
Garbage disposal Eutrophication, Spread of harmful diseases Marshes (eg. Muthurajawela, Bellanwila-Attidiya)
Regulation of water flow(Dams) Gradual disappearance of lowland wetlands Villu ecosystems in the Mahaweli Floodplain
Unplanned irrigation structures Changes in water quality Coastal lagoons (eg. Kalametiya, Malala)
Mining (Sand/coral) Loss of habitats and species Rivers, Coral reefs

Direct loss/exploitation of species:Overexploitation of wetland plants and animals has resulted in several species facing the risk of extinction. Factors that contribute to direct loss/exploitation of species are highlighted in following table

Causes of species loss/exploitation and their effects
Contributory Factors Impacts Affected wetlands
Poaching (for consumption) Reduction of population of targeted birds and mammals Waterfowl (Ducks and Teals), Otter
Ornamental fish trade Reduction of local fish Black Ruby Barb, Cherry Barb, Mono etc.
Ornamental plant Trade) Reduction of aquatic plant population and loss of habitats for aquatic animals Cryptocoryne spp., Aponogeton spp.
Water Pollution Reduction of aquatic animals,adverse effects on human health Fish, Amphibians, Piscivorous birds, Otter

Spread of invasive alien species (IAS):
Introduction of several exotic aquatic animal and plant species that have eventually escaped into wild habitats are posing a serious threat to native aquatic biodiversity. Observations made during the past five years have enabled to document 10 species of invasive alien fauna (8 species of fish, one turtle and one aquatic mollusc) and 12 species of invasive alien flora spreading in different wetland ecosystems throughout Sri Lanka (Bambaradeniya, 2002). Among them, 4 species of fauna (Tilapia - Oreochromis mossambicus, Walking catfish - Clarias batrachus, Rainbow Trout - Oncorhynchus mykiss and Mosquito fish - Gambusia affinis) and two species of flora (Water Hyacinth -Eichhornia crassipes and Giant Mimosa - Mimosa pigra) are included in the list of the world's 100 worst invasive alien species. The ornamental fish trade has been the sole contributory factor to the introduction of invasive alien aquatic species into Sri Lanka.

Natural Phenomena:
Wetlands are threatened by natural phenomena as well. For instance, the recent prolonged drought in the Hambantota area resulted in the drying off of several tanks, streams, salt marshes and lagoons, causing death to several wetland animal species. The rise of seawater temperature (due to climate change) resulted in the bleaching of coral reefs, especially in the southwestern part of Sri Lanka. For example, the Hikkaduwa Coral Reef, which was once a rich habitat, is now virtually a dead reef (Rajasuriya et al., 2000). The December 2004 Tsunami also resulted in the degradation of coastal wetlands such as mangrove, lagoons and estuaries.