STATUS OF BIODIVERSITY OF MAHAWELI RIVER AND ITS RIVER BANKS BETWEEN WATAWALA AND GINIGATHHENA

Abstract

A systematic survey was conducted from January to August 2003 to identify existingmajor habitats, status of biodiversity with respect to flora (flowering plants and fern andfern allies) and fauna (birds and mammals, butterflies, amphibians and freshwater fishspecies), and threats they faced in the Mahaweli river and adjacent river banks betweenWatawala and Nawalapitiya. The flora and fauna were documented using scientificallyvalid techniques.

The survey enabled to identify seven major vegetationlhabitats along the Mahaweli riverand its adjacent river banks. They are: river bank habitat with secondary growth; flowingfresh water habitat; ephemeral and perennial small stream water habitat; scrub forestarea; Pinus plantation, homegardens, Albizia dominated abandoned tea plantation, teaplantation, abandoned tea plantation with grassland, and Eucalyptus plantation. Withinthe stretch, a total of 170 species of flowering plants and fern and fern allies belongs to64 families were identified. A total of 18 species of birds (9 families), 16 species ofbutterflies (7 families), 10 species of freshwater fishes (5 families), 16 species of reptiles(7 families), 7 species of amphibians (3 families) and 13 species of mammals (10families) have also been documented.

At present, the biodiversity of Mahaweli river and its adjacent river banks hasbeen subjected to several threats, namely pollution due to garbage disposal (mainly atGinigathhena), spread of alien invasive species (mainly at river banks due to Clusiarosea), direct exploitation of species (freshwater fish species), encroachment of bankreservation, unplanned land use practices and small hydropower projects. The criticallyaffected group as a result of these threats is fresh wa•er fish species, which includes 6threatened endemic species. Thus, clear mitigatory measures will be required to avoiddisturbances to such species.