Mannheim Pilot Report

Mannheim, one of Germany’s hottest cities, faces significant challenges in its densely built-up city centre, where high summer temperatures reduce comfort and usability of public spaces. Within Urban ReLeaf, two citizen-driven campaigns have been implemented to enhance urban green infrastructure and improve thermal comfort for residents, with a particular focus on vulnerable groups. The Urban Trees Campaign enables citizens to document and update information on urban trees using the mobile app “Urban ReLeaf – Mannheim's Trees”. This activity expands the municipal tree registry, generates shared knowledge about Mannheim’s urban greenery, and supports informed decision-making for urban planning and climate adaptation. The app was released in July 2024 and now has more than 140 users. The Greenspace Perceptions Campaign - “Cool bleiben auf Mannheims Plätzen” (July-August 2025) investigates how residents experience central public squares – Alter Meßplatz, Friedrichsplatz, Marktplatz, Paradeplatz, and Schillerplatz – during hot days. The campaign focuses on thermal comfort and the quality of stay, providing insights into how public spaces can be adapted to reduce heat stress and offer shade, comfort, and recreational opportunities. Approximately 280 participants were asked about their experiences of heat and the design of public spaces to identify conditions that support comfort and usability during hot days. Data collected will inform strategies for future-proof urban design and enhance the well-being of all city inhabitants. Through active citizen participation in data collection and project design, Mannheim is co-developing actionable knowledge for climate adaptation, strengthening urban resilience, and creating more liveable and inclusive public spaces.