Biodiversity and ecosystem services in urban green infrastructure planning. A case study from the metropolitan area of Rome (Italy)

Target 2 of the European Biodiversity Strategy promotes the maintenance and enhancement of ecosystem services <(ES) as well as the restoration of at least 15% of degraded ecosystems by creating green infrastructure (GI). The purpose of the this research is to present a GI proposal that combines the delivery of regulating services with the restoration and ecological reconnection of urban forests and trees in a densely urbanised context. The project area covers about 3 000 ha in the urban sector of the metropolitan area of Rome and the GI components consist of 533 ha of areal green spaces and of more than 500 km of road verges. Planned interventions include forest restoration and tree plantations, with a varying service supply according to type and condition of the different components. Potential natural vegetation (PNV) models and dispersal potential of representative forest species, together with structural and functional vegetation models for the enhancement of air pollutants removal, guided the selection of the species to be promoted and of the planting pattern. Environmental benefits of the proposal include more than 30 ha of restored urban forests, about 15 000 planted individuals of native oaks, a sevenfold improvement in ecological connectivity and halved isolation between green spaces. On the other hand, the expected socio-economic benefits include almost 300 000 potential beneficiaries of the improved air quality and avoided costs for damages to human health that range between 40 700 and 130 200 EUR per year. Notwithstanding their preliminary character, these estimates allowed the proposal to highlight the relationship between GI and public health. Moreover, they showed the economic and social effectiveness of nature-based solutions in comparison with further development of grey infrastructure. These results promote the definition of a national GI strategy in Italy.