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Status of Mangroves in Sri Lanka

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Status of Mangroves in Sri Lanka Journal of Coastal Development ISSN: 1410-5217 Volume 7, Number 1, October 2003 : 5 - 9 Accredited: 69/Dikti/Kep/2000 Review STATUS OF MANGROVES IN SRI LANKA K. M. B. C. Karunathilake *) Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka Received: September, 5, 2003 ; Accepted: September, 20, 2003 ABSTRACT In Sri Lanka many estuaries and lagoons are fringed with vastly diverse mangrove forests. The total mangrove cover is very small as 0.1 to 0.2 percent of the total land area. The distribution of fauna and flora varies along with wet and dry zone in the country. Around 25 species of flora are exclusive to mangroves and more than 25 species can be identified as associated mangroves. Variety of invertebrates and vertebrates are conspicuous in the mangrove forests, but only a few species are confined to the ecosystem. Heavy utilization and reforestation for shrimp farms and building construction work severely affect on this ecosystem. When compare to decline rate of mangrove forests in Sri Lanka, current implemented conservation measures are inadequate. Key words: Sri Lanka, Flora, True mangroves, Invertebrates, Vertebrates. *) Correspondence: Phone: 94-081-2232002, Fax: 94-081-2232121; E-mail: [email protected] INTRODUCTION brackish water area is about 158016 ha, coastal population occupies 34% (NRESA, Sri Lanka described as the “pearl’’ of the 1991) of the population in the country. Indian Ocean is an island, situated between latitudes 5.55´ & 9.51´ North and Distribution longitude 79.41´& 81.54´ East in the Indian Ocean. Once it was called Sri Lanka enjoys highly productive coastal “Serendip” by the Greek because of its ecosystems such as Coral reefs, Sea appealing beauty. The total land area is grasses, Mangrove forests, Lagoons, 65,620 km 2 and is surrounded by 1705 km Estuaries, Salt marshes, Mudflats, Sand of coastline. The total area of continental dunes & beaches. The mangrove cover is shelf is 44250 km 2. The width of the shelf about 12 000 ha (CCD, 1986) which is as ranging from 8 km along the southeastern little as 0.1 – 0.2% of the total land area. and eastern coasts to 45 km in North & However total mangrove cover cannot be North western coasts. The total estimated estimated because of the inaccessibility of Status of Mangroves in Sri Lanka 5 Journal of Coastal Development ISSN: 1410-5217 Volume 7, Number 1, October 2003 : 5 - 9 Accredited: 69/Dikti/Kep/2000 northern and eastern coasts due to present and Lumnitzera racemosa (Combretaceae) security situation. are also very abundant in the country. Since the tidal amplitude is very Acanthus ilicifolius (Acanthaceae) is the low in Sri Lanka, the distribution of most predominant associate mangrove mangrove forests are confined to narrow species in the island (De Silva, 1985; De inter tidal belt. All these are associated Silva & De Silva, 2002; Pinto,1986; with some of the lagoons and estuaries in Wetland site report,1994). the country, therefore patchy in More than 25 of mangrove distribution. The degree of extension is associate species can be identified and extensive in northwestern and northeastern those are divided into fore mangroves and coastlines. The largest forest patch is in back mangroves. Fore mangroves are Puttlam – Kalpitiya lagoon. Second largest mainly comprised of sea grasses. This type is Jaffna peninsula followed by mangroves is very common in Kalpitiya – Batticaloa in Trincomalee and Batticaloa (CCD, and Jaffna lagoons. In back mangroves 1986). Floral and faunal distribution of the several species of salt marsh, sea shore- mangrove forests vary according to major marsh and freshwater marsh are found (De climatic zones namely Wet and Dry zone. Silva & De Silva, 2002). Species of salt The average air temperature is between 30- marshes comprise of annual herbaceous 35 0C. Relative humidity is very high and plants which can grow in inter tidal areas lies between 80-90 %. Salinity fluctuates (Amarasinghe, 1997). from almost zero to more than that of sea water (0- 35 ppt) and can be differed with Fauna fresh water discharge, tidal amplitude, topography and extent of the estuary or Sri Lankan mangrove ecosystems consist lagoon (De Silva & De Silva, 2002). of a wide variety of fauna, but unfortunately there is no complete faunal Flora list. Aquatic fauna in mangroves are not much different from that found in estuaries In Sri Lanka flora is the most studied and and lagoons. So only few species were well knowledgeable biodiversity category. confined to mangrove forests. A variety of Mangrove flora are of two types: true invertebrates are found in the mudflats mangroves and associate mangroves, with in mangrove forests. Invertebrate neither of these flora are endemic to Sri diversity shows little variation in dry and Lanka. More than twenty five species of wet zones. Most dominant ones are true mangroves have been recorded and gastropods and grasped crabs. Among many of them are shrubs, shorter than 10 gastropods Terebralia palustris are very m. Nearly half the species show a wide abundant and specific to mangroves. Also distribution (Amarasinghe, 1997; De Silva Telescopium telescopium , Cerithidea & De Silva, 2002). Rhizophora mucronata cingulata are very frequently seen in (Rhizophoraceae) and Avicennia marina mangroves. Fiddler crabs ( Uca species), (Avicenniaceae) are the most predominant Portunid crabs ( Scylla serrata ) and true mangrove species in Sri Lanka. They lobsters like Thalassina anomala are are very extensively grown in Kala Oya vastly observed in mangrove forests. delta and Puttlam lagoon respectively. Thalassina anomala appear to be specific Bruguiera gymnorrhiza (Rhizophoraceae) Status of Mangroves in Sri Lanka 6 Journal of Coastal Development ISSN: 1410-5217 Volume 7, Number 1, October 2003 : 5 - 9 Accredited: 69/Dikti/Kep/2000 to the mangrove forests. Several species of of 25 ppt which prevails during most shrimps, penaeid prawns and non-penaeid month of the year. They are usually prawns are conspicuous in mangrove characterized by the presence of forests (De Silva, 1985; De Silva & De Rhizophora mucronata, Avicennia marina Silva, 2002; Pinto, 1986). All hierrachical and Acanthus ilicifolius (De Silva & De levels of vertebrates could be identified in Silva, 2002). the mangrove forests (fishes, Amphibians, Mangrove can also be classified Tetrapods, Birds, and Mammalians). according to flooding, topographical and Fish species found in mangroves, floral characteristics namely Scrub are the common estuaries species and can mangrove forest, over washed mangrove be found in every estuary and lagoon. forest, Basin mangrove forests, Riverine They show little variation in the wet zone and Fringing mangroves. Scrub mangrove and dry zone. Periopthalmus species are forests are degraded mangrove forests the most predominant species in both wet developed in areas of poor drainage and dry zones among 150 species of fishes facilities and this type is occasionally seen in mangrove forests (De Silva, 1985). in the dry zone. Over washed mangrove Species Bufo melanostictus , Limnonectes forests are found on small islands, which limnocharis are very common among get completely covered over at each high amphibians. Snakes, which include python tide. So the organic content in the soil is and cobra and young crocodiles, are very very low. Mangroves in small islands of commonly seen tetrapods, in mangrove northwestern region are good examples of ecosystems. Over 100 species of birds the above. Basin mangrove forests lie in a have been observed, but none of them are depression and the surrounding soil being confined to mangroves. Both resident and washed into the basin. This type is very migratory species can be observed and dominant in Jaffna peninsula. The riverine their abundance is very high in the dry mangroves are found in the estuaries of zone than that of wet zone. Many species major rivers along the south and southwest of mammalians including Elephas coasts. Fringing mangroves are found maximus maximus and Panthera pardus along shallow lagoons, especially in the kotiya visit the mangroves most often, south and east coasts. The floristic especially the mangroves that continue compositions of the latter two are similar with the evergreen forests (De Silva & De to low saline and high saline mangrove Silva, 2002). forests (Amarasinghe & Balasubramaniam, 1992 ; Balasubramaniam,1985 ; De Silva, Types of Forests 1985). Mangrove forests in Sri Lanka can be Current Status classified into low saline forests and high saline forests based on salinity. In low As all other natural ecosystems, mangrove saline mangrove forests salinity is low forests too provide many extractive and often below 10 ppt. Communities of Nypa non-extractive uses for the beneficiary of fruticans and Rhizophora apiculata are mankind. But many extractive uses such as characteristics of such mangroves. In high shrimp culture, House construction work saline mangrove forest salinity is in excess cause extensive damages on mangrove Status of Mangroves in Sri Lanka 7 Journal of Coastal Development ISSN: 1410-5217 Volume 7, Number 1, October 2003 : 5 - 9 Accredited: 69/Dikti/Kep/2000 forests at present. Also increasing But it is under a great threat of utilization of its recourses severely affects deforestation with less notice. So it is its stability. Mangroves in Sri Lanka are important to educate the public about its one of the most abused ecosystems in the values and uses and to encourage country. At recent past there was an abrupt conservation of mangroves. Unfortunately decline in the forest cove especially in still many concerned authorities of the Puttlam – Kalpitiya lagoon. country do not identify its necessity. Approximately 34 % of mangrove forests ACKNOWLEDGEMENT were converted to industrial shrimp farms in that area (Jayasinghe & De Silva, 1992). This caused the deterioration and I am thankful to Prof. E. I. L. Silva, Project destruction of the ecosystem and also Leader, IFS for his encouragement and creation of other issues such as lack of guidance to attend the training programme. clean water and loss of jobs by the local fishermen.
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