Implications for city greening
Cities and their rural surroundings are often quite different
environments in terms of their tree composition. For Leipzig, the
overlap between tree genera planted in the city and those growing in
regional forests is small. Unlike Leipzig, the surrounding forests
consist mostly of spruce and pine (https://bwi.info, data for
Saxony, accessed 2020-03-07), that is, taxa of no or minor importance as
allergen producers (cf. Table E1). By planting trees in proportions
found in natural habitats and eliminating highly allergenic taxa47,48 city greening may become even more beneficial.
Attention to allergenic potential is also important when selecting tree
species that are able to withstand the challenges posed by climate
change. Resilient tree taxa 49-51 may prove
detrimental for the development of allergenic diseases. Examples includeAlnus x spaethii 52 and Corylus colurna,a close relative of the major allergen source Corylus avellana,which despite their sturdiness should be reconsidered as future city
trees.