Trees and urban forests mitigate residents’ heat stress, filter air pollution, and provide multiple other ecosystem services. They are often referred to as the “green lungs” of the city. Especially during the COVID-19 lockdown, urban trees also contribute(d) significantly to the population’s mental health. At the same time, trees in the city are threatened by ongoing climate change and continuous urbanization. Research in the GrüneLunge 1.0 project in recent years has shown a high frequency of trees in the urban forest of Karlsruhe were unhealthy due to prolonged periods of heat and lack of precipitation. As a result, many of the services mentioned above of the urban forests are threatened.

In order to counteract the further decline of urban forests and to increase their resilience, the BMBF-funded project GrüneLunge 2.0 aims to translate previous scientific findings into measures. In addition to ITAS, which is the leading partner in this joint project, the cities of Karlsruhe and Rheinstetten are involved as municipal partners. Scientific partners are the Forest Research Institute of Baden-Württemberg (FVA) in Freiburg, the Deutscher Wetterdienst (DWD – Germany’s National Meteorological Service) with its Research Centre Human Biometeorology (ZMMF), also located in Freiburg, and the Institute of Meteorology and Climate Research Atmospheric Environmental Research (IMK-IFU) in Garmisch-Partenkirchen.

Over the next two years, the main goal of GrüneLunge 2.0 will be to implement and consolidate adaptation measures for the future management of urban forests. Based on the data collected in GrüneLunge 1.0, we will set up a geoportal to visualize the current provision of 35 different ecosystem services. In a series of expert interviews and workshops, we will explore the extent to which ecosystem service points can be used in the future management of urban forests. In addition, an ecosystem service model is being validated specifically for the Karlsruhe region to help foresters and horticulturists calculate pollutant removal and heat stress mitigation more accurately at the individual tree level (in collaboration with IMK-IFU). Moreover, an interactive internet portal is being designed together with FVA to select the most suitable tree species for future plantings in urban areas. For the first time in Germany, a heat warning system is being developed that functions at the neighborhood level and considers in particular the needs of vulnerable groups such as children or the elderly (in collaboration with DWD).The shift towards resilient urban forests will not be achieved without citizen involvement. A new citizen forum on street trees will encourage citizens to meet regularly and share their ideas on how to care for urban trees and green spaces. Overall, the project thus aims to improve adaptation planning for future urban forests.

In view of increasing drought and heat in cities as a result of climate change, researchers from the GrüneLunge project spoke out in August 2022 with a detailed statement (PDF). To reduce temperatures and retain moisture, they recommend, among other things, increasing the number of trees in cities.

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