in Sri Lanka - Ministry of Environment

A Brief Overview of the Biodiversity of Sri LankaDevaka WeerakoonUniversity of ColomboSri Lanka, with a total land area of 65,610 km 2 is a tropical island situated in the Indian Ocean.The southwestern region of Sri Lanka, encompassing approximately 20,000 km 2 , is the onlyaseasonal ever wet region in the whole of South Asia (Ashton & Gunatilleke, 1987; Gunatillekeet al., 2005). This region is referred to as the wet zone of Sri Lanka and receives up to 3000 mmof rainfall annually. Wet-zone of Sri Lanka along with the Western Ghats of India is designatedas one of the world’s biodiversity hotspots, in demand of extensive conservation investment(Myers et al., 2000; Brookes et al., 2002). This high biodiversity seen in Sri Lanka can beattributed to a wide variety of climatic, topographic and soil conditions that exist in the islandthat has resulted in a diverse array of aquatic and terrestrial habitats (detailed descriptions ofthe natural terrestrial and aquatic natural habitats are given in the flora section).Sri Lanka was part of the ancient Gondwanaland and was located adjacent to the Africancontinent. Around 160 million years ago, the Deccan plate which comprised of India and SriLanka, broke away from the Gondwanaland, drifted northwards and collided with the Asian platearound 55 million years ago. Thereafter, Sri Lanka separated from India due to submersion ofthe land bridge between the two countries about 20 million years ago. These zoogeographic,climatic, topographic and edaphic factors have shaped the faunal and floral assemblage seenin Sri Lanka. During the last 2 to 3 thousand years land-use changes brought about by humanshave been instrumental in large scale habitat changes that have had both positive and negativeinfluences on Sri Lanka’s flora and fauna.Sri Lanka’s biodiversity is significantly important both in a regional and global scale. Sri Lankahas the highest species density (number of species present per 10,000 sq. km) for floweringplants, amphibians, reptiles, and mammals in the Asian region (NARESA, 1991). The currentlyrecognized statistics of the major plant and animal taxa treated in this book are given in Table1. However, it should be noted that there are many other taxonomic groups in Sri Lanka thatare excluded from this table due to lack of clear data on their current status.Table 1. Species richness of selected faunal and floral groups of Sri LankaTaxonomic Group Number of Species Number of Endemic SpeciesAngiosperms 3,154 894Gymnosperms 2 0Pteridophytes 336 49Soft corals 35Hard corals 208Spiders 501 256Centipedes 19Marine crustaceans 742Fresh water crabs 51 50Dragonflies 118 47Ants 194 33Bees 130Butterflies 245 26Leafhoppers 257xvii