A review of the floral composition and distribution of mangroves in Sri Lanka

Mangrove communities comprise a group of biotic components, including plants, animals and microbial organisms, that are highly adapted to intertidal environmental conditions. However, none of these can be identified as a community in a mangrove ecosystem without the actual mangrove plants (trees and shrubs), implying that the true mangrove vegetation is the major constituent of the ecosystem. Mangrove vegetation defines the landscape and participates directly or indirectly in the ecological processes that take place in this ecosystem (Lugo & Snedaker, 1974; Hamilton & Snedaker, 1984; Tomlinson, 1986). Therefore, knowledge of the exact species plant composition of mangroves in any country is a basic and important prerequisite to understanding all the aspects of structure and function of mangroves, as well as their biogeographical affinities and their conservation and management. The past and present distribution of mangroves has been reviewed by several authors on a global level (e.g. Tomlinson, 1986; Ricklefs & Latham, 1993; Duke, 1995; Duke et al., 1998; Ellison et al., 1999). In this paper, we focus on the distribution of mangroves in south-western Sri Lanka. The species richness of mangroves in many geographical areas is decreasing with time as a result of the destruction of mangrove forests and exposure to various anthropogenic stresses (Hamilton & Snedaker, 1984). The area and floristic composition of mangrove forests in Sri Lanka has also decreased at a rapid rate during the last few decades (Pernetta, 1993; Corea et al., 1995; Dahdouh-Guebas et al., 2000; De Silva & Balasubramaniam, 1984–85), possibly leading to the local extinction of some rare species. Peculiarly, some recent documents from governmental and national institutes have reported a number of new records of mangrove species for Sri Lanka; these publications (e.g. Liyanage, 1997) have erroneous species identifications and list many more mangrove species