Effectiveness of protected areas in conserving avian communities amid human impact in Nigeria

Understanding the impacts of human activities on avian communities in- and outside protected areas (PAs) is essential for guiding conservation strategies and evaluating the effectiveness of PAs in conserving avian diversity. Effective PAs should not only safeguard species within their boundaries but also contribute to maintaining ecosystem functionality in surrounding landscapes. We used citizen science data from the Nigerian Bird Atlas Project (2015-2024) and the human footprint index (HFI) from the Socioeconomic Data and Applications Center (SEDAC) to analyze avian taxonomic and functional richness and diversity across 146 paired pentads (5' × 5' grid cells). Each protected area pentad (PAP) that covered ≥70% of a PA was paired with an unprotected pentad (UPP). Bayesian hierarchical models were applied to assess avian taxonomic and functional richness and diversity between PAPs and UPPs and to examine the influence of human activity on these community metrics based on HFI values. The PAPs had higher taxonomic richness and diversity than UPPs. In contrast, abundance-weighted functional diversity metrics (Rao's Q, functional dispersion, and divergence) were higher in UPPs than PAPs due to the proliferation of disturbance-tolerant generalist species. However, functional richness was lower in UPPs than PAPs, reflecting fewer ecological niches. Taxonomic and functional richness increased with moderate human impact, consistent with the intermediate disturbance hypothesis, but declined under higher levels of disturbance, suggesting a point beyond which species cannot adapt or persist. These findings support the critical role of PAs in conserving avian species and functional traits and highlight the effects of human impact on species survival. Conservation strategies must prioritize the maintenance of PAs and integrate sustainable management in UPAs to safeguard avian diversity and functional traits essential for ecosystem resilience, especially as anthropogenic pressures increase.