Impact of Invasive Alien Species in the Ecosystem of Sri Lanka

by Saanaaree Manoratne 1 January 2018

Invasive Alien Species are non-native organisms accidentally or deliberately introduced to the native ecosystem, which may adversely impact native flora and fauna. After the liberalization of Sri Lanka’s economy in 1977, foreign organisms have been introduced to the country through the horticulture, aquaculture and pet industries. Majority of these species are unable to survive outside its confinements which they are introduced into, such as gardens, fish tanks or cages. However, some species have escaped these confinements and spread its population in the native environment. The proliferation of such species may cause depletion of the unique tropical and marine biodiversity of Sri Lanka.

Water Hyacinth, or “Japan Jabara” in the native tongue, is commonly found in the waterways across the Island. According to the project of Invasive Alien Species in Sri Lanka, this plant native to South America was introduced to the island as an ornamental plant in the early 1900s. This aquatic weed obstructs the flow of water which may degrade its quality and also disrupts navigation in internal waterways. Its rapid propagation on the surface of water-bodies deprives submerged aquatic flora and fauna of sunlight and oxygen. Scientifically termed Najas marina, or in the native tongue as “Katu Penda” is an aquatic weed which has reportedly caused severe damage to Mahakanadarawa Tank in Anuradhapura and Madu River in Balapitiya. Clidemia hirta, or “Kata Kalu Bovitiya” as commonly referred by the natives is a densely branched perennial shrub found in lowland rainforests. As reported by the project of Invasive Alien Species in Sri Lanka, it was introduced to the country in 1894 as an ornamental plant in the botanical gardens. Reportedly, it causes the extinction of native flora and fauna and, adversely affect cultivated land and livestock. Lantana, or popularly known as “Gadapana” among the locals is an invasive shrub which could be observed throughout the Island. The species is native to South America, and it is believed to be introduced in 1826 through Botanical Gardens. It has invaded the grazing lands available for elephants in Udawalawa National Park, a major elephant sanctuary in the country.
Tenacious terrapin, a fresh-water turtle commonly known as “tanki ibba” in the native tongue is found in waterbodies of wet zone. It is believed that this species has been imported to the island by the aquarists in the early 1980s and known to be competing with vulnerable native species for food and nesting grounds. Knife Fish (Chitala Ornata) or “Mannaya” as identified by the locals, is a freshwater fish reported in Diyawanna Oya, Bolgoda Lake in Colombo District and water bodies in the areas of Dodangoda – Matugama.

The species is native to Mekong and Chao Phraya basins of Indochina in Thailand. It is believed that the species was accidentally introduced to the natural habitats from the aquariums, as they were first reported in lakes around Colombo after a major flood in June 1992. Knife Fish is known to be a predator that feeds on live prey and therefore poses a threat to the existence of several native aquatic species. Tank Cleaners, or commonly known as Scavengers, is a fish that was accidentally released from ornamental fish-farms or aquariums. This population has been recorded in Bellanwilla, Nadimala, and Bolgoda in the Western Province, Kandy, and Polgolla area in Central Province and Minneriya Tank in North Central Province. It mainly feeds of algae and aquatic weed and therefore could place other native species, depending on a similar diet, in peril
Protection of Bio Diversity has drawn the attention of the policymakers across the globe since the 1990s. According to the data published by the International Union for Conservation of Nature in 1997, Invasive Alien Species are considered to impact biodiversity most negatively in the long term. Another remarkable milestone is The Convention on BioDiversity that came into effect in 1993, which required the contracting parties to take measures to prevent, control and eradicate the alien organisms which threaten ecosystems, habitats or species. At the regional level, European Union regulation of 1143/2014 on Invasive Alien Species that came into force in 2015 serves similar ends.

The most extraordinary measure taken in the Sri Lankan context is probably the initiation of the Project of Invasive Alien Species by the Ministry of Mahaweli Development and Environment. Other measures include the formulation of National Invasive Alien Species Policy in 2012 and the grant of Cabinet approval to enact legislation exclusively dealing with the subject. Such legislation has been enacted by Japan to prevent the adverse effects of Invasive Alien Species on “human safety, agriculture, forestry, and fisheries.”

Upon Sri Lanka’s integration into the global market, more foreign organisms which cause ecological damage may inevitably enter the territorial confines of the country. Hence a complete ban of importation of foreign organisms shall be deemed unnecessary and impractical. To balance these conflicting ends, Sri Lanka should take robust measures, firstly to prevent such organisms entering its territory, secondly to establish an effective surveillance system which detects the presence of Invasive Alien Species and finally to control the proliferation of such organisms and minimize its impact. It must be noted that the prevention of entry of invasive species is less costly and more effective than subsequent control and eradication. Therefore, a regulatory body needs to be established to oversee the importation of living organisms to Sri Lanka. Such imports should be mandatorily accompanied by a certificate which verifies the properties of such an organism and an assessment of its impact if it merges with the native ecosystem of the Island. Further, the law should provide for suitable methods of disposing of such foreign organisms imported for commercial purposes and lack of due diligence with this regard should be subjected to scrutiny. It is recommended that the most effective way in which such measures could be implemented is the adoption of the proposed Invasive Alien Species Bill.