Natural selection? Picking the right trees for urban greening

Fast-track programs to plant millions of trees in cities around the world aim at the reduction of summer temperatures, increase carbon storage, storm water control, provision of space for recreation, as well as poverty alleviation. Although these multiple benefits speak positively for urban greening programs, the programs do not take into account the drastic differences between urban and natural systems. Elevated temperatures together with anthropogenic emissions of air and water pollutants distinguish the urban system. Although the potential for emissions of volatile organic compounds from urban vegetation combined with anthropogenic emissions to produce ozone has long been recognized, the municipalities actively enlarging their green spaces still generally either overlook or ignore this fact. Here we assess the scientific evidence of biogenic induction of ground-level ozone concentrations in urban and sub-urban areas and argue that it is feasible and beneficial to implement measures necessary to limit biogenic contributions to air pollution. With the example of biogenic induction of ground level ozone concentrations we demonstrate that interactions between plants and urban ambient conditions have to be taken into account in all efforts of creating “naturopolises”. We explore the mechanisms behind these interactions and propose a pathway to improve our understanding of these interactions.