Designing seaweed-based environmental strategies for coastal erosion mitigation in Sri Lanka

Abstract

Coastal erosion poses a severe threat to Sri Lanka’s coastal ecosystems and communities, demanding sustainable, nature-based alternatives to conventional hard-engineered defenses. This paper explores the environmental potential of seaweed as a Nature-Based Solution (NbS) to mitigate coastal erosion while strengthening local livelihoods. Adopting a qualitative case study approach in Hikkaduwa, the study combines visual analysis, stakeholder interviews, and literature synthesis to assess seaweed’s ecological feasibility. The findings highlight two dominant local species; Sargassum illicifolium and Eucheuma sp., as ecologically viable erosion buffers capable of stabilizing sediments and dissipating wave energy. Google Earth analysis between 2011 and 2023 indicates a coastline retreat of approximately 18 meters, revealing the urgency for sustainable interventions. Seaweed-based systems, drawing parallels with mangroves and seagrasses, demonstrate potential to reduce wave energy by 20–40% and trap sediments effectively. Beyond environmental protection, seaweed cultivation fosters economic empowerment, particularly among coastal women, through bio-composite development and aquaculture enterprises. The study concludes that integrating seaweed into coastal management frameworks promotes ecological resilience, socioeconomic inclusion, and long-term adaptive capacity. Future research should include hydrodynamic modeling, sedimentation rate analysis, and longitudinal ecological monitoring to quantify environmental performance and scalability.