Mapping the impact of tree cover on heat wave and rainfall runoff mitigation in the city of Karlsruhe, Germany.

The effects of climate change are making cities inhospitable due to extreme conditions including more frequent and intense heat waves, storms, and flooding events. The increase in urbanization due to the growing population living in cities caused a large amount of soil sealing that exacerbates the impact of heat and stormwater runoff, exposing people's health to considerable risk. Green infrastructure in cities such as street trees, parks, and urban forests provide numerous benefits to society, such as reducing runoff by storing water on the canopy and in the soil. Furthermore, trees improve urban thermal comfort by intercepting and reflecting solar radiation thus preventing the heating of underneath surfaces, and by leading to heat energy losses by the conversion of water to vapor during the transpiration process. The city of Karlsruhe accounts for approximately 135,000 trees on streets and in parks with a forest cover of 26% of the city area. The planning and management of this essential 'green lung' for the city demands extensive efforts to ensure the health of trees, which are stressed by the effects of climate change such as drought. These efforts are laborious and expensive and often fall short of providing optimum services. Therefore, a new project assesses a method of easily determining the effects of green infrastructure on its impact on water runoff and air temperature-humidity. It makes use of the availability of open remote sensing data provided by the Copernicus Service and integrates this information into the i-Tree HydroPlus model. Based on this methodology, the actual contribution of tree cover in Karlsruhe to heat wave mitigation and stormwater runoff is evaluated, also considering natural developments (increase and decrease in tree cover) and urban green space management (irrigation systems) scenarios. The 'GrueneLunge 2.0' project aims to implement and consolidate adaptation measures for the future management of urban forests in the city of Karlsruhe and these results support sustainable planning of forested areas by maximizing environmental services and promoting greener, more livable cities for citizens.