Planting for healthy air: Urban biodiversity enhances natural chemical environments

Societal Impact Statement :
Cities urgently need nature to improve public health, support biodiversity, and increase resilience to climate change. Yet not all green spaces offer the same benefits. In this study, we show that more diverse urban plantings create richer “chemical environments”; subtle, naturally scented atmospheres formed by plant emissions that can influence how people feel and recover from stress. By revealing this hidden dimension of human–plant interaction, our work suggests that planting a greater variety of species in parks and streets could enhance everyday well‐being while supporting wildlife and climate goals. These insights can guide city planners, public health professionals, and community groups in designing greener, healthier cities for all.

Summary

- Urban green spaces are known to support human well‐being, yet we still lack a clear understanding of which plant characteristics and green spaces configurations create the most psychologically and physiologically beneficial urban environments. Stress reduction and restorative properties of green spaces are often emphasized, but the mechanisms underlying those benefits are still unclear. But plants also shape city air through the release of natural volatile compounds that can influence human physiology and health. We aimed to determine whether more botanically diverse parks also create richer chemical environments, revealing a hidden dimension of human–plant connection in cities.
- We measured plant species richness and vertical vegetation structure across public parks in Lausanne, Switzerland, and collected airborne volatile organic compounds (VOCs) directly in each park. We combined vegetation surveys, air sampling, and species‐level phytochemistry data to test whether plant diversity predicts VOC richness and chemical richness in real and simulated plant communities.
- Plant communities differed strongly among parks and across vegetation layers, and parks with higher plant diversity also exhibited higher chemical diversity in the air. Phylogenetic mapping revealed lineage‐level variation in chemical potential, and simulated plant assemblages confirmed a consistent positive relationship between botanical richness and chemical richness.
- Our findings show that biodiversity shapes an overlooked chemical dimension of urban nature, suggesting that diverse plantings may enhance the atmospheric qualities that help people reduce stress, recover, and connect with natural environments. Considering plant chemical diversity in urban greening strategies could enhance stress reduction and increase biodiversity, fostering healthier and more resilient cities.