Citizen perception of and activation for implementing Nature-based Solutions (NbS) against heat stress in the city of Cologne, Germany

Climate change impacts increasingly affect human wellbeing worldwide, particularly through consequences of extreme weather events such as heavy precipitation, flooding and heat. Densely populated areas face greater exposure to these hazards than rural areas. The Urban Heat Island (UHI) effect exacerbates the impacts of heat in cities. Nature-based solutions (NbS) such as green and blue infrastructure can be used to adapt to climate change effects and mitigate urban heat stress as well as extreme precipitation impacts. Adaptation measures like urban green spaces (parks, gardens), street trees, vegetation on buildings (facade, roof greenings), water bodies or grass grid paver unsealings have significant cooling effects, enhance water retention and thus can increase thermal comfort and flood resilience of urban dwellers. While Cologne is recognized for its abundance of green spaces like the inner and outer `green belt´, there is still potential to improve and expand existing NbS to more effectively mitigate the challenges of climate change and the UHI effect. The successful implementation of additional NbS to address these challenges is dependent on public acceptance as the establishment and maintenance often rely on public participation. As part of the AKT@HoMe Project aiming to analyse the climate change adaptation potential through citizen participation by assessing the willingness to act and operational empowerment of residents in two socioeconomically contrary districts in the city of Cologne, this research is dedicated to analyze the acceptance of and the activation potential for the implementation of NbS.  

To understand residents’ perception of heat stress and the acceptance of NbS in the two districts, we conducted an anonymous survey, achieving over 150 responses. The survey utilized a quantitative, self-administered questionnaire, available in online and paper-based formats. Distribution took place via community events, mailbox inserts, and online platforms between summer 2024 and winter 2024/25. Results show that residents of both districts experienced a high level of heat stress in the past and expect a further increase in future. Preferences for mitigation measures include urban parks and forests, water-permeable pavers, and street trees among other, but also technical, solutions. NbS and hybrid measures are preferred over solely grey measures. Despite a high willingness to act, such as creating and maintaining NbS at home and in the city district, only few of the surveyed residents currently already engage in such activities.  

This gap was further examined through workshops with residents from both districts. Throughout three independent sessions citizen were participating in a three hour `future workshop´, working out future scenarios and options to adapt to UHI in their districts. The findings show that residents see the city government as primarily responsible for implementing NbS but also desire a more active role in the process to foster greater engagement, for example through neighbor groups. This highlights the need for a co-creation process between civil society and the public sector, ensuring that residents can actively contribute to the successful implementation and upkeep of NbS.