Theoretical Development and Empirical Validation of a Vegetation-Based Ecosystem Health Assessment Index for Nigerian Protected Areas

Ecosystem health assessment frameworks for African protected areas have largely been derived from temperate contexts and fail to account for the structural and functional complexity of Nigerian vegetation types, creating a fundamental gap in conservation monitoring science. This study develops and empirically validates an original Vegetation-Based Ecosystem Health Assessment Index specifically calibrated for Nigerian protected area vegetation types, spanning mangrove, rainforest, derived savanna, Guinea savanna, Sudan savanna, and montane ecosystems. The theoretical framework integrates vigour-organisation-resilience theory, functional diversity theory, and disturbance ecology into a multi-metric index with vegetation-specific parameter sets derived through an expert elicitation Delphi process involving 28 Nigerian and international vegetation ecologists. Metrics incorporated include species richness, functional diversity (Rao's quadratic entropy), structural complexity, regeneration adequacy, invasive species burden, and spatial connectivity. The index was empirically calibrated and validated using vegetation monitoring data from 14 protected areas across Nigeria's six geopolitical zones. Internal validation assessed metric redundancy using principal component analysis. External validation compared index scores against independently assessed ecosystem health scores from aerial survey data. Internal consistency (Cronbach's alpha = 0.82) and external validation correlation (r = 0.87, p < 0.001) confirmed index reliability and validity. Application of the validated index revealed that mangrove and Guinea savanna protected areas showed the greatest ecosystem health deficits nationally, while Jos Plateau montane sites scored highest. The study makes original contributions to protected area monitoring science by providing the first Nigerian-calibrated, empirically validated vegetation ecosystem health index, with a freely accessible implementation toolkit for the Nigerian National Park Service. Keywords: ecosystem health index, protected areas, vegetation monitoring, functional diversity, Nigeria