Crowd-sensed plants as living sensors of urban climate and soils: High-resolution insights from 326 European cities

Human populations are increasingly concentrated in cities, creating some of Earth’s most modified ecosystems. Yet, spatially explicit, observation-based assessments of urban climates and especially soils remain scarce. This limits evidence-based planning for climate adaptation and urban resilience. Here, we leverage over 80 million crowd-sensed plant observations from 326 European cities as “living sensors” to map high-resolution patterns of urban climate and soil properties. This approach builds on consolidated knowledge of plant ecological preferences, integrated through three new pan-European systems of ecological indicator values.Beyond the urban heat island, we identify additional consistent contrasts between built-up and green areas in moisture, light, soil pH, disturbance, and salinity. The magnitude of these within-city environmental gradients rivals those observed between cities thousands of kilometers apart across Europe. Environmental conditions in built-up areas are remarkably similar across cities, highlighting urban environmental homogenization. In contrast, urban forests maintain natural environmental diversity, contributing to cooling, moisture retention, and key ecosystem functions.Our new sensing approach, called mobile crowd sensing of environments (MCSE), supports participatory assessment of nature-based solutions and provides actionable insights for planners, policymakers, and local communities. It enables evidence-based decision-making for climate adaptation, sustainable urban development, and the promotion of human health and well-being under rapid urbanization and climate change.