Impact of shrimp-farming on mangrove ecosystems in Pambala, Chilaw

Abstract

Mangroves are the coastal equivalent of tropical forests and hence of important ecological and environmental significance. In Sri Lanka, as in many other countries, conversion of mangrove forests to other uses has resulted in a considerable decline of these ecosystems. It is estimated that mangroves in Sri Lanka cover only 87 km2, which amounts to around 0.2 % of the total land area of the country (Legg and Jewell, 1995). One of the major factors that has led to their destruction in Sri Lanka is shrimp farming. Valietel et al. (2001) report that the conversion of mangroves to aquaculture ponds is responsible for about 38% of the total mangrove loss that has occurred in the country. In addition to the direct destruction of mangroves, shrimp farming has also caused the degradation of water quality in lagoons and the loss of biodiversity in the remaining patches of vegetation (de Silva and de Silva 2002; Wolanski et.al. 2000). In the present study we attempt to assess the impact of shrimp farming on mangroves in Pambala, Chilaw, an area where shrimp farming is extensively conducted, by assessing changes in the composition of mangrove flora and selected invertebrate taxa as well as through changes in water quality of the lagoon.