Mapping spatio-temporal expansion and ecological impacts of Artisanal and Small-Scale Gold Mining in River Catchments Using Multi-Temporal Satellite Imagery and field data

Artisanal and small-scale gold mining (ASGM) has become a major driver of land degradation and river system disturbance in Ghana, yet its spatial dynamics remain poorly quantified. In our study, we assessed the spatio-temporal dynamics of ASGM and associated land use and land cover (LULC) changes in the Pra (23,202 km²), Ankobra (8,442 km²), and Tano (21,465 km²) river catchments in Ghana, with emphasis on ASGM encroachment into riparian zones. We performed a supervised object based image analysis (OBIA) on sentinel-2 images for the catchments for 2020, 2022, and 2024 using a Random Forest classifier trained on four LULC classes (mining, built-up, water, vegetation). Results indicate consistent ASGM expansion across all catchments, resulting in substantial vegetation loss and increase in surface water, likely reflecting the formation of mine-pit ponds. The Pra catchment experienced the most expansion in ASGM (1,155 km²), followed by the Ankobra (347.8 km²) and Tano (192.3 km²) catchments, alongside increasing encroachment into a100m buffer riparian zones of these river channels, where ASGM increased from 72.65 to 133.97 km² in the Pra (299 km²), from 51.36 to 70.57 km² in the Ankobra (114 km²), and from 25.75 to 44.43 km² in the Tano (292 km²) river channels within this period. To complement these findings, field data collection is currently ongoing to assess the impacts of ASGM expansion on ecosystem health. The findings of this study demonstrate intensifying ASGM pressure on Ghana’s river systems and associated ecosystems, highlighting the need for targeted riparian zone protection and catchment-scale management interventions.