Monitoring the Spatio-Temporal Patterns of Forest Gaps and Health in the Rwenzori Mountains National Park, Western Uganda

Forest gap dynamics, vegetation health and canopy density in montane ecosystems remain underexplored in East Africa despite their critical role in forest development and biodiversity conservation. In this study, we assessed spatial and temporal patterns of forest gaps in the Rwenzori Mountains National Park, a UNESCO World Heritage Site in Western Uganda, using multi-temporal Landsat satellite imagery from 2013 to 2025 within the Google Earth Engine platform. We employed Normalised Difference Vegetation Index thresholds to detect and map forest gap dynamics and estimate canopy density, complemented by ground truthing. Our analysis revealed a non-linear pattern of forest disturbance with forest gap sizes increasing substantially between 2015 and 2019 (peaking at 1,421.49 ha), followed by reductions from 2019 to 2023 and a sharp resurgence by 2025 (1,381.1 ha). Vegetation health exhibited significant temporal variation (p < 0.001), with declines in 2017 and 2025 likely linked to illegal logging, fire, landslides and climate-related stressors. Canopy density followed a similar fluctuating pattern, declining notably in 2025, indicative of widespread canopy degradation. Multiple linear regression explained 97.2% of canopy density variation, showing strong positive effects of NDVI, EVI, elevation, slope and rainfall, while temperature negatively influenced canopy density and aspect showed no significant effect. Our findings demonstrate that forest gap formation in Rwenzori Mountains National Park is driven by both natural and anthropogenic pressures, with temporal surges in fragmentation disrupting forest structure. We conclude that elevation influences forest gap size, but cannot fully explain observed patterns without accounting for human and ecological drivers. Enhanced monitoring, stricter enforcement of conservation policies and elevation-sensitive forest management are urgently needed to sustain vegetation health and prevent long-term forest degradation in this ecologically sensitive montane forest.