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A Descriptive Guide to Invasive Alien Species of Sri Lanka

A descriptive account of National Priority and Potentially Invasive Alien Species.


                                         Although Sri Lanka is a small island, it has a wide variety of climatic, topographic and soil conditions that has resulted in a diverse array of aquatic and terrestrial habitats such as forests and grasslands, rivers, streams, mangroves, inland and coastal wetlands and coral reefs. Thus, Sri Lanka together with the Western Ghats of India, has been identified as one of the 34 Global Biodiversity Hotspots based on the number of endemic plants and vertebrates, their density and remaining vegetation relative to the original extent (Myers et al., 2000, Mittermeier et al, 2005). Birdlife International (BI) has also identified Sri Lanka as an endemic bird area (Myers et al., 2000). Furthermore, the island’s lowland rainforests, montane rainforests and south western rivers and streams are listed in the WWF’s Global 200 eco-regions as one of the most biologically distinct terrestrial, freshwater and marine eco-regions of the planet, and as such they are considered priorities for conservation (Myers et al., 2000).

                                        The high species endemicity observed in Sri Lanka can be attributed to its long geographic isolation that limits immigration of new species, allowing established species to evolve in the absence of strong competitors and predators. Many of these endemic species are highly specialized to the habitats they have evolved in and their continued existence depends on availability of habitat as well as quality of the habitat. Therefore, invasive alien species, introduced due to human activities have a dramatic effect on such isolated ecosystems where they can become a leading cause of species extinctions. Further, islands such as Sri Lanka are more vulnerable to invasion by alien species as they lack natural competitors and predators that control IAS populations in their native ecosystems. In addition, islands often have ecological niches that have not been filled because of the distance from colonizing populations, which further increase the probability of successful invasions. Also due to their isolated nature and limited resource availability islands have to interact more with the outside world and the present trends in globalization have lead to increased trade, tourism and transportation that are responsible for most number of accidental introductions of potentially invasive species.

                                      The Global Invasive Species Database of the IUCN Invasive Species Specialists Group (ISSG) lists approximately 82 Invasive species or potentially invasive species as being present in Sri Lanka. These species have invaded human modified landscapes such as agriculture land, abandoned lands, irrigation systems, and home gardens. Some of the alien invasive species have also invaded natural ecosystems and therefore may have an impact on the rich biodiversity of the island. Most of these invasive species are either pets or ornamental plants used and distributed by man, which by accident have been released to the natural environment where they have become established. Some of the species however, have been introduced intentionally by various government line agencies or non governmental entities for specific purposes without realizing the invasive potential of these organisms.


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