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Mangrove and Lagoon Ecosystem Degradation Caused by Shrimp Farming in the Pambala-Chilaw Lagoon Complex, Sri Lanka

par Ofori, Samuel
Promoteur Dahdouh-Guebas, Farid
Co-Promoteur Kodikara, Sunanda K.A.S.;Jayatissa, Loku Pulukkutige
Publication Non publié, 2021-08-31

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Résumé :

Since the introduction of shrimp farming (SF) in Sri Lanka during the 1980s, mangrovevegetation and lagoons located on its North-Western coast have undergone a high level ofdegradation. This study sought to assess the retrospective (1973 to 2020) areal changes inmangrove vegetation and shrimp farms, assess the levels of physicochemical parameters(nitrates, phosphates, pH and conductivity) in water and sediments samples, the socialecologicalimpacts of SF, and its ecological footprint in the Pambala-Chilaw lagoon complex(P-CLC). Aerial (1973) and satellite (2020) images were geo-processed and classified to assessthe land use/cover changes in the P-CLC with the classification accuracy assessed using thequantity and allocation disagreement method. Water (n=81) and sediment (n=9) sampleswere collected from 9 sites in the lagoon, 30 sediment samples were also collected from the lagoon's fringe mangrove vegetation, and interviews were conducted with some groups.Mangrove vegetation around the Chilaw lagoon decreased in areal extent by 45% of whichthe majority (92%) was attributed to SF. Statistically significant differences were observed forlevels of physicochemical parameters recorded in water and sediment samples, indicating ahorizontal and vertical pollution stratification in the lagoon. High levels of pH (pH > 9)recorded in water samples were evidenced by the observation of algal blooms and limitedfish catch in the lagoon over the years. Local people and fishermen mentioned the negativeimpacts of SF on their wellbeing. The very high ecological footprint of SF and its socialecologicalin the P-CLC, therefore, calls for immediate actions.