Spatiotemporal Assessment of Habitat Quality and Sediment Delivery Ratio in a Coastal District of Thailand

Mangrove-fringed coastal areas provide habitat and sediment regulation ecosystem services, increasingly affected by land-use change. However, integrated local-scale assessments of habitat quality and sediment dynamics remain limited. This study assessed land-use and land-cover (LULC) changes in Mueang Samut Sakhon District, Thailand, for 2000–2020 and projected a business-as-usual (BAU) scenario for 2040 using a cellular automata-artificial neural network model (hindcast overall accuracy 74.7%). Habitat quality and sediment dynamics were assessed for 2000, 2020, and 2040 using the InVEST Habitat Quality and Sediment Delivery Ratio models, and tested with an independent mangrove dataset, sensitivity analyses, and an analysis by LULC transition. Between 2000 and 2020, built-up land increased by 34.7% and mapped mangroves declined by 50.6%, with further changes of +4.8% and −9.3% projected for 2040. Global Mangrove Watch indicated a smaller decline (29%), so the mapped loss is an upper estimate. Total habitat quality declined by 22.2% (2000–2020), mainly through habitat loss and remains concentrated along coastal and estuarine zones, with degradation increasing locally near development corridors. Under the 2040 scenario, potential soil erosion increased by 0.86%, while sediment export rose by 4.28%. The increase in avoided sediment export (3.64%) resulted mainly from higher modelled connectivity around new built-up land. Continued urban expansion may intensify pressure on remaining mangroves, reduce habitat quality, and alter sediment delivery. Integrating LULC modelling with InVEST-led assessment can support coastal planning and identify candidate areas for nature-based solutions, including mangrove restoration, which can be improved through field assessment.