Vertical Greening Systems (VGS) with native species: an ecological approach to urban air quality improvement

Urbanization and climate change have intensified environmental challenges which pose significant risks to human health. Green infrastructures, such as VGS, offer nature-based solutions for improving air quality, mitigating the urban heat island effect, enhancing biodiversity. Despite their benefits, VGS implementation is often hindered by maintenance challenges, species selection issues, and a lack of ecological considerations. This study explores the effectiveness of native plant species in VGS for particulate matter (PM) retention, to enhance air quality in urban environments while promoting biodiversity conservation. A case study in Rome evaluated five autochthonous plant species—Cymbalaria muralis, Capparis spinosa, Centranthus ruber, Parietaria officinalis, and Rubus ulmifolius—based on PM capture efficiency. The research explains how to select native species with different leaf microstructures (wax density, trichomes, and surface wettability) and analyze their role in PM retention. Using scanning electron microscopy (SEM) , the study quantified PM accumulation on leaves collected from different sites. Statistical analyses revealed that C. ruber exhibited the highest overall PM capture efficiency, while P. officinalis demonstrated the lowest retention capacity. Smaller particles (<1 µm) were retained in significantly higher quantities by C. muralis and C. spinosa. The findings underscore the potential of native species in VGS to enhance urban air quality while reducing maintenance needs due to their adaptation to local climatic conditions. The study highlights the necessity of an ecological approach in plant selection, integrating biodiversity conservation into urban greening strategies. By optimizing species choice based on functional traits, VGS can become more effective and sustainable tools for air pollution mitigation and urban resilience.