Assessment of Sargassum Beaching and It’s Effect on Communities Along the Western Coast of Ghana

Abstract

Sargassum, a genus of the brown macroalgae, plays a crucial role in marine ecosystems but has become an increasing concern due to its massive beaching events globally, particularly along the coastlines of Ghana. This study focuses on assessing the trends in Sargassum beaching and its effects on the livelihoods of selected coastal communities in the Western Region of Ghana. A mixed-methods approach was employed, combining simple random sampling and purposive sampling to select a representative sample of 400 participants, including fishermen, fishmongers, and coastal residents from Beyin, Esiama, and Sanzule. Data were collected through transect walks, field observations, photography, focus groups, and face-to-face interviews, with audio recordings in Nzema dialect transcribed for analysis. An Unmanned Aerial Vehicle (UAV) was used to monitor and evaluate the incidence and distribution of Sargassum along the beach. The UAV data collection was conducted in September and October 2021 and 2023, using a DJI Phantom and processed using Structure-from-Motion (SfM) and Multi-View Stereo (MVS) algorithms in Agisoft Photoscan software. The resulting orthophotos were converted to Normalized Green-Red Difference Index (NGRDI) values using QGIS to detect sargassum on the beach. These images were further segmented and classified using eCognition and ArcMap, allowing for the estimation of Sargassum extent and volumes. The research highlights the temporal variability in Sargassum accumulation from 2021 to 2023, revealing a decline in average beach coverage from 17,153 m² in 2021 to complete a near-zero range (0–5 m²) in 2023, indicating complete disappearance in 2023. The estimated Sargassum volume also decreased from 11,387 m³ in 2021 to near-zero levels in 2023, indicating a significant reduction in beaching over the period studied. Fluctuations in accumulation were found to affect local livelihoods with 80.5% of respondents reporting a negative impact on fishing and income, while 49.2% indicated that tourism activities declined during heavy influx periods. Environmental degradation was observed through reduced water quality and shoreline contamination, reported by 72% of participants. Health concerns were also evident, with 18% reporting skin irritation and 7% respiratory discomfort associated with decomposing Sargassum. Despite these challenges, 63% of community members adopted sweeping and burning as management practices, while 37% buried Sargassum to reduce odor and beach obstruction. Furthermore, only 16% of respondents were aware of its alternative uses, such as composting and fertilizer production, showing untapped potential for sustainable management. The findings contribute to a deeper understanding of the socio-economic and environmental implications of Sargassum beaching in Ghana, providing evidence-based recommendations for policymakers and stakeholders to enhance resilience and sustainability in the region.