Urban parks as habitat providers for biodiversity: a multi-scale analysis in the urban area of Milan

Actual trends draw attention to a significant biodiversity decline associated with current and upcoming degree of urbanization. In this context, urban parks can play a crucial role for the conservation of many species within cities. Urban systems are highly dynamic and complex human-shaped ecosystems, leading the maintenance of high biodiversity levels within them a challenging goal to undertake. In this study, we conducted a multi-scale analysis in order to detect how environmental features in an urban area affected biodiversity and we provided suitable information for implement an effective management of green spaces with the aim of support high level of biological diversity. Fifteen urban and peri-urban parks in the metropolitan area of Milan (Italy) were investigated and 93 sampling plots for birds (species and number of individuals) and vegetation (trees Diameter Breast Height) sampled. Results of GLMs at landscape scale showed how bird species richness and abundance are significantly affected by park area and three land cover types and the importance of the environmental variables was determined using RDA components. In a finer level of analysis we described how 28 birds species respond differently to land cover types, presence of water and distance from park's border within sampling points. Here, wooded land cover type and water bodies resulted to be the variables that mostly affect birds presence. For forest species, we further investigated the effect of vegetation structure. Results showed unusual pattern for some species (preference of little trees) that can be explained by considering the effects of environmental features acting at different scales. A multi-scale approach is essential to proper understand biodiversity patterns and concerted conservation actions are necessary.