DEGRADATION OF MANGROVE SWAMPS IN SRI LANKA

Abstract

Mangrove swamps acts as an open system and exchange matters and energy in coastal habitats.The trees or shrubs in this ecosystem grow in shallow and muddy salt waters or brackish waters,such as those along quit shorelines or in estuaries of anaerobic soils found in the intertidal zonein tropical and subtropical areas. The common name of mangroves applies to a number offlowering trees or shrubs that are members of several different families. They are often referredto as coastal woodland, mangal, tidal forest and mangrove forest. Like the tropical ecosystemmangrove swamps play an important role in the economy of tropical and sub tropical people forthousands of years.

There are twenty-nine species of mangroves identified in the western and southern coasts of SriLanka and they fall into seventeen families. The multiple uses of the mangrove swamps can becategorized in the different ways. They provide food and shelter for a large and varied group offishes, crustaceans and shellfish, particularly in their juvenile and stage, which is mostvulnerable predators. Mangrove woods protect the coasts from storm surges and high windsassociated with tropical typhoons .As well, mangroves trap coastal and act as buffer zone inadjacent estuarine areas against the large changes in up-streams input of nutrients and wastesproviding the bulk of primary production in estuaries. They serve as protection against soilerosion and land building through soil accretion and trap coastal pollutants, which mayotherwise severely damage adjacent marine ecosystems. Besides, mangrove swamps act asbuffers adjacent flood plains from the damage caused by severe storms, thus reduce themaintenance cost of harbours and navigation channels by trapping silt. They may be importantin maintaining and controlling the normal cycles of nitrogen and sulphur. Furthermore, theyserve as wildlife sanctuary: offer aesthetic, educational and scientific values.

Mangrove swamps in Sri Lanka have been damaged by adaptation for the development ofhuman settlements, industrial activities, tourism, and aquaculture and land reclamation. Manymangrove species have also been degraded by changes in freshwater run-off, salinity regime andtidal flow patterns: excessive siltaion and discharge of toxic substances; and flowing of pollutedwater into lagoons, lakes, estuaries and tidal creeks. The applications of insecticides andherbicides too have caused damage to mangrove habitats.

The depletion and degradation of mangroves have directly and indirectly influenced thelivelihood of the people and survival of the wildlife. These problems and degradation thatclearly threaten mangrove ecosystems have not been taken into consideration in many studies.This paper envisages revealing different uses, behavior of the fauna and flora of mangrovehabitats, human impact and degradation .For this purpose, field observations, formal andinformal discussions with inhabitants and officials were carried out within the period between1993 and 2000 infrequently. The reconnaissance phase of the study was useful to highlight thenature of the environmental problems and degradation of mangrove species. This study proposesvarious practices to promote conservation and management of mangrove swamps in Sri Lanka.