Allergies are one of the leading causes of chronic illness, affecting 20-30% of adults in Europe and the US. Prevalence of pollen-related allergies has been on the rise in the past decades and is expected to double by 2050. This increasing trend is largely driven by human-induced global changes. Warmer temperatures, longer growing seasons and increased atmospheric CO2 tend to increase yearly pollen production, while introductions of plant species outside their native range spread novel allergens – i.e. allergenic molecules absent from resident flora.
Galloping urbanization represents one of the most radical forms of anthropization of the environment: higher temperatures, pollution and human disturbance tend to favor non-native species, forming novel urban ecosystems. Warm conditions have been shown to extend flowering seasons in cities, while the presence of non-native plants may increase the chemical diversity of pollens and the spectrum of allergies.
Using a community approach, we investigated the allergenic properties of dry grassland communities across a rural-to-urban gradient in Berlin, Germany. We expected the more urban and invaded grasslands to exhibit the highest allergy risk.
Results/Conclusions (< 200 words)
In 2017, we recorded plant species abundance in 56 plots of grasslands covering a range of urbanization and plant invasion levels. For all plant species, we collected publicly available data on allergenic scores – including the specific allergenic molecules.
Borrowing from trait-based community ecology, we used new methods to characterize each community by its abundance-weighted mean allergenic score and allergenic molecule diversity. Data on flowering phenology then allowed us to model the potential distribution of allergen production throughout the year, and investigate its variation along the gradients of urbanity and plant invasion.
Contrary to expectations, urban grasslands were not more allergenic than rural ones. However, the number of allergenic species in grasslands tended to increase with the proportion of neophyte invasion. In invaded grasslands, the flowering season tended to extend further into autumn, and the wider spectrum of molecules suggested that new allergies may appear in urban areas.
High population densities in cities imply that such a novel allergenic spectrum may cause more harm in urban than rural conditions. Cities may yet remain a relative haven for people suffering from hay fever, but efforts to identify novel risks and control them early should be a priority in urban nature management.