Interactive mapping of allergenic urban street trees in Australia

Tree pollen can be a persistent allergen for sensitised individuals, causing allergic rhinitis and asthmatic symptoms. Increased urbanisation results in larger populations living in cities and relying on urban greenspaces for recreation and associated ecosystem services, where the street landscapes are determined by urban planners. Urban forest strategies broadly divide planting choices based on biological functionality, climate resilience and environmental benefits but increasingly the associated physical and mental health impacts of urban vegetation are being considered. Here, we studied pollen allergenicity in four Australian cities by incorporating measures of allergenicity in existing street tree asset databases and visualising these using a simple and flexible mapping tool, the mapview package in R. Olea europaea (olive) and Betula nigra (river birch) were the most abundant trees with the greatest allergenic potential across all four cities, and hotspots of tree clusters with high allergenic potential could be easily visualised. The lack of allergenicity data for native Australian trees was also apparent, despite these comprising a large proportion of the urban street scapes. Incorporating allergenicity in mapview provides an interactive tool which is more easily interpretable for the public and urban landscape stakeholders than existing GIS based risk mapping techniques, and which can support decision making in future planting to avoid high concentrations of allergenic trees.