Soil Biochemical Indicators for Evaluating Urban Nature-Based Solutions: Insights from a Multi-City Study in Italy

The National Biodiversity Future Center (NBFC), created within Italy’s National Recovery and Resilience Plan and supported by EU Next Generation funding, is committed to advancing the conservation and sustainable management of Italian and Mediterranean biodiversity. A central mission of the NBFC is to foster the adoption of Nature-Based Solutions (NbS) and ecological restoration practices in both natural and urbanized landscapes, with a strong emphasis on improving soil health and enhancing ecosystem services.

Urbanization exerts significant pressure on soil ecosystems, compromising their ability to deliver essential services such as carbon sequestration, nutrient cycling, and biodiversity support. Nature-Based Solutions (NbS), including green infrastructures, are increasingly recognized as effective strategies to mitigate these impacts and enhance urban resilience. However, robust and scientifically validated tools for monitoring their effectiveness remain limited.

This study explores the potential of soil biochemical indicators, specifically stable isotope composition and enzyme activities, as sensitive metrics for evaluating soil health and NbS performance in urban environments. The approach was initially tested along an urban-to-natural gradient in Pisa and Livorno, where areas dominated by Quercus ilex L. served as reference sites. Results demonstrated that these indicators effectively detect alterations in soil functioning associated with urban pressure, confirming their diagnostic value.

Building on this validation, the methodology was extended to major Italian cities (Turin, Milan, Florence, Rome, Naples) to assess the capacity of different NbS to restore soil functionality and improve ecosystem services. Preliminary findings indicate that green infrastructures significantly enhance soil biochemical processes, particularly those linked to carbon and nutrient dynamics. These outcomes provide a scientific basis for integrating soil health indicators into urban planning and NbS design, reinforcing their role in promoting sustainability and resilience in Mediterranean cities.