Variation in Plant Species Diversity and Forest Fragmentation in Gashaka-Gumti National Park, Northeastern Nigeria

Forest fragmentation poses a major threat to biodiversity in Nigeria’s protected areas. This study assessed plant species diversity and forest fragmentation in Gashaka-Gumti National Park (GGNP), North-Eastern Nigeria over a 27-year period (1987–2014). Multi-temporal Landsat imagery, GPS-based field surveys, and socio-economic assessments were employed to evaluate forest cover change and biodiversity resilience. Supervised classification revealed a sharp decline in dense forest cover from 367,500 ha (54.5%) in 1987 to 107,600 ha (18.2%) in 2014, while fragmentation indices increased from 45% to 63%. Quadrat-based sampling (100 quadrats across 10 sites) provided floristic and structural data, including species counts, tree girth, height, basal area, and wood volume. Simpson’s Diversity Index values (0.87–0.90) indicated high species richness and evenness despite habitat loss. Site 8 recorded the highest diversity (20 species, 688 trees, tree density 0.688), while quadrat q10 exhibited the highest tree density (0.9). Statistical analysis confirmed anthropogenic drivers—particularly agricultural expansion, settlement encroachment, and youth unemployment—as significant contributors to forest fragmentation (χ², p < 0.05). The findings highlight the paradox of GGNP: biodiversity remains high, yet forest integrity is increasingly compromised. This underscores the urgent need for integrated conservation strategies that combine remote sensing monitoring with community-based socio-economic interventions. GGNP remains a critical biodiversity hotspot, but its long-term resilience depends on effective management, local participation, and transboundary collaboration to safeguard species diversity and ecosystem services