Impacts of climate change on allergenic pollen production: A systematic review and meta-analysis

Climate change has been identified as a major driver of alterations in pollen production, with potential implications for allergenic diseases and ecosystems. This systematic review and meta -analysis examine the impacts of global warming on the Annual Pollen Integral (APIn), a measure of pollen production, across multiple plant species. We conducted a comprehensive literature review and selected studies based on predetermined inclusion criteria. Our analysis covered 11 major allergenic taxa (Poaceae, Betula, Olea, Artemisia, Urticaceae, Cupressaceae, Alnus, Corylus, Platanus, Morus, and Fraxinus), with a focus on long-term trends in the relationship between temperature and APIn. The results revealed a generalized increase in APIn over the study period (1974-2020) for most taxa. Notable exceptions were Urticaceae and Artemisia, which exhibited a generalized decrease. Our analysis also highlighted a varying start and end years for the time series studies, ranging from 1974 in the United Kingdom to 2020. The earliest series were from Belgium, Italy, and the UK, while the most numerous studies were from Spain and Poland. Subsequent analysis of the impact of environmental parameters on APIn revealed complex patterns. Accumulated rainfall and mean air temperature during flowering and preceding months exhibited different relationships with APIn depending on the taxa and the period considered. These findings underscore the complex impacts of climate change on pollen production, with significant variations across different plant species and regions.