Phenological shifts as indicators of climate change in West Africa: a systematic review of ecological, agricultural, and societal implications

The phenology of biological processes such as flowering, leaf flush, fruiting and animal migration is one of the most reliable biological indicators of climate change. In West Africa, where over 70 per cent of agriculture is rain-fed and ecosystems range from humid forest to semi-arid Sahel, phenological change carries immediate consequences for food security, biodiversity and rural livelihoods. This systematic review, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, synthesises evidence on phenological responses to climate change in West African agriculture, vegetation and fauna, appraises monitoring methods, and identifies priorities for research, monitoring and policy. Systematic searches of Scopus, Web of Science and Google Scholar identified 312 records; after deduplication and eligibility screening, 64 peer-reviewed studies and technical reports published between 2019 and 2025 were included and thematically synthesised, with quality appraised using a GRADE-informed framework (inter-coder kappa = 0.79). Five themes emerged: (1) agricultural phenology shows shorter, later growing seasons, with climate variability accounting for over 50 per cent of Sahelian cropland greening trends; (2) vegetation phenology shows spatially contrasting greening and browning; (3) faunal phenology remains poorly studied despite evidence of cascading ecological shifts; (4) monitoring still relies heavily on NDVI with limited multi-sensor integration; and (5) governance and policy frameworks rarely translate phenological evidence into adaptive planning. Phenological change in the region is consistently disruptive but spatially heterogeneous. Closing the evidence gap will require expanded faunal monitoring, co-production of indigenous and scientific knowledge, multi-sensor monitoring frameworks, and explicit inclusion of phenological indicators in national adaptation frameworks linked to the Sustainable Development Goals.