Soil erosion, often referred to as “red soil erosion,” has been considered as a major environmental issue in Ishigaki Island. It affects not only sugarcane farming, but also the degradation of fisheries, coastal ecosystems, and coral reefs, eventually leading to economic loss in tourism. This study sheds light on the management strategy of sediment retention ponds as many of them remain unmanaged and filled with sediments, gradually degrading coastal fisheries and ecosystems. An economic model was developed to illustrate how sediment retention ponds are sustainably managed under alternative scenarios. This study suggests that frequent dredging in sediment retention ponds is required to reduce the management and environmental costs. It also focuses on the effective use of dredged sediment and community-led management.
