Potential Use of Mangroves for Coastal Protection: A Case Study from Sri Lanka

Abstract

Mainstreaming coastal biodiversity certainly brings nature-based solutions for the conservation of offshore and onshore resources. Being an island, the long-term shoreline change of Sri Lanka is particularly important for management of the island’s coastal resources. This study was carried out at the southwestern and southern coasts of Sri Lanka to investigate the protective capacity of mangroves against coastal erosion, and coastal inundation hazards due to the climate associated sea-level rise. Structural diversity of mangrove stands was assessed in terms of alpha-diversity, plant species richness, basal area, tree height, density, and structural complexity index. Analysis of aerial photographs and the ASTER Global Digital Elevation Model was used to identify shoreline changes along the southwestern and the southern coasts of Sri Lanka. Results revealed that by and large, the southwestern coast is highly vulnerable to coastal erosion and inundation hazards whereas the southern coast manifests a tendency to retreat. The average annual rate of shoreline change however varies within the two coastal areas, as there were accreting as well as eroding segments on both southern and southwestern coasts, nevertheless, all retreating beach segments were the sites of improper maritime developments. Segments with lower rates of shoreline erosion and coastal inundation hazards were found to be located close to the mangrove and other coastal vegetation with varying structural complexity and diversity. Reforestation and restoration of vegetation in coastal lagoons and estuarine habitats are evidently effective strategies not only to protect the low-lying coastal hinterlands but also to preserve coastal biodiversity.