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