Spatiotemporal analysis of forest cover change in the Okomu Forest Reserve, Edo State, Nigeria

Abstract

Deforestation and other anthropogenic pressures continue to degrade forest ecosystems, particularly within protected areas of tropical regions. However, long-term information on forest cover dynamics in many parts of Nigeria remains limited. This study assessed spatiotemporal changes in forest cover within the Okomu Forest Reserve over a 33-year period (1986–2019) using multitemporal Landsat satellite imagery and an unsupervised ISODATA classification approach. Results revealed a substantial decline in dense forest cover from 59.67% (685.74 km²) in 1986 to 16.22% (186.36 km²) in 2019, alongside a reduction in moderate forest from 24.98% to 16.70%. In contrast, open forest expanded markedly from 3.31% (38.07 km²) to 53.54% (615.31 km²), becoming the dominant land-cover class by the end of the study period, while very open forest exhibited fluctuating but overall increasing trends. Spatial analysis indicated progressive fragmentation and widespread expansion of degraded forest classes, particularly between 2011 and 2019, when open forest increasingly encroached into previously dense forest areas. Major drivers of forest degradation were associated with excessive timber extraction and unsustainable harvesting of medicinal plant species. The findings suggest that existing conservation and protection measures within the reserve have been insufficient to prevent continued forest degradation. Strengthened conservation policies and improved forest management strategies are therefore necessary to enhance biodiversity protection and support the long-term sustainability of forest resources within the reserve.