BIODIVERSITY OF THE MADUGANGA MANGROVE WETLAND

Abstract

The Maduganga estuary and mangrove islets are a complex coastal wetland ecosystem situatedwithin the two Divisional Secretariats of Balapaitiya and Karandeniya in the Galle District ofSouthern Sri Lanka, The total area of the estuary is 915 ha, of which 770 ha consist of openwater, while islands account for 145 ha. With the view of safeguarding the ecological functions,resources and values of the Maduganga estuary fer conservation and future sustenance ofbiodiversity, meN Sri Lanka carried out a systematic assessment of biodiversity in Maduganga.A six-month field survey was conducted from May to October 2000. Field sampling was carriedout at fortnightly intervals' each sampling session spanning over six continuous days. TheMaduganga ecosystem was divided into six major Si rata based on the occurrence of differentvegetation types, human activities and a hypothetical salinity gradient. These strata weresampled for fauna and flora in a systematic manner, using standard techniques. The threats tobiodiversity were also assessed

The survey revealed that the Maduganga wetland consists of 10 major wetland vegetation types.These vegetation types harboured a total of 303 species of plants belonging to 95 families. Thetotal plant species included 19 endemics, 8 nationally threatened species and 9 invasive alienspecies. Based on the extent of occurrence (ha), mangroves and mangrove mixed swamps werethe dominant wetland vegetation types in Maduganga, In addition to these wetland vegetationtypes, three major terrestrial vegetation types are also found in the islands and the surroundingmainland area of the Maduganga estuary. Perennial crops (mainly cinnamon) dominated theterrestrial vegetation types. A total of 98 plant species were recorded from the multi-specieshome gardens. When considering the species richness of flora in different wetland vegetationtypes, mangroves harboured the highest number of species, closely followedby mangrove mixedswamps. Maduganga estuary harbours a small population of a very rare, threatened mangrovespecies Lunmitzera littorea. A total of 248 species of vertebrate fauna, belonging to 121 familieswere recorded from Maduganga. These included 20 species (8%) of endemics, while 30 species(12%) are considered as nationally threatened. The native vertebrate fauna of Madugangarepresents 30% of Sri Lanka's native inland vertebrate species.

Maduganga, perhaps one of the last remaining tracts of pristine mangrove forest in Sri Lankawith a rich biodiversity, now appears to be threaten,~c:.with the same predicament that many ofthe island's mangroves now find themselves in, owing to increasing human activity. At present,this wetland is not a protected area under any government department. Therefore, it is envisagedthat the findings of this survey will contribute to the .x'nservation of this unique coastal wetland.