This study assessed the impact of forest ecosystem services degradation on the livelihoods of local communities on the Mambilla Plateau, Nigeria, using mixed geospatial and socio-economic approaches. Multi-temporal Landsat imagery (1987–2024) and household survey data (n = 384) were analyzed to quantify biomass, carbon stock changes, and livelihood vulnerability. Results revealed a 43.6 % decline in aboveground biomass and a 41.2 % reduction in carbon stock over the 37-year period. High-biomass and carbon-rich zones shrank drastically, confined mainly to protected areas such as the Ngel Nyaki Forest Reserve. The Livelihood Vulnerability Index (LVI–IPCC) indicated a mean score of 0.63, with exposure (0.75) and sensitivity (0.68) exceeding adaptive capacity (0.43). Regression results showed that forest dependency positively influenced vulnerability (β = 0.41, p < 0.01), while income diversification (β = –0.38, p < 0.05) and education (β = –0.29, p < 0.05) reduced it. Spatial analysis confirmed a strong correlation (r = 0.71, p < 0.01) between biomass loss and livelihood vulnerability. The findings highlight the urgent need for participatory forest restoration, improved governance, and livelihood diversification to enhance ecosystem resilience and human well-being on the Plateau.