Urban tree suitability in climate change

Urban trees are exposed to a variety of stress factors. © Friederike Stoll
Urban trees are exposed to a variety of stress factors.

Rising temperatures and an increase in weather extremes as a result of climate change pose special challenges for municipalities and their urban trees. Increasingly, tree species that have long been a feature of our urban landscape are clearly showing the traces of climate change. Drought stress and increased susceptibility to diseases and pests are no longer uncommon. In this subproject, we are investigating which locations the familiar tree species will be suitable for in the future and which alternatives are available. The aim is to develop an online tool for municipalities that serves as a decision-making basis for site- and climate-specific urban tree species selection. An urban tree species list consisting of approx. 30 species is to facilitate the selection of suitable tree species for municipalities.

 

In order to meet the different requirements placed on urban trees, a multi-criteria procedure is used. Thus, in addition to climatic aspects, other criteria relevant to cities - such as allergy potential or tolerance to road salt - are considered for the suitability assessment of urban trees. For the development of this decision tool, existing tools for the suitability of different tree species for use in urban areas are used. These include the Climate Species Matrix (KLAM), the citree planning database of the Technical University of Dresden, which is based on it, and the street tree list of the German Conference of Garden Authorities. In addition, a new, own literature study especially with regard to ecosystem services is carried out and supplemented. Furthermore, the scientific findings from GrüneLunge 1.0. will be incorporated. For example, urban trees in Karlsruhe were studied in terms of their ecosystem services and their effect on human health as part of the project. We were also able to determine the growth potential of various tree species as a function of site conditions and extreme weather events. In order to take into account community-specific requirements, the individual criteria are weighted according to their importance with the help of test communities and, in addition, scenarios are created that take regional characteristics or individual requirements into account when selecting tree species. Such prioritizations, which are also called preference articulations, can be, for example, drought tolerance, shade, irrigation, or even human health. Also essential for the creation of the planning tool is close cooperation with the Working Group on Urban Trees of the German Conference of Garden Authorities. The result of the subproject is a tool that has been expanded to include several criteria and further developed to include methodological aspects that support the complex decision-making situation of tree species selection in urban areas under climate change.

Photo: Friederike Stoll/FVA