Sustainable policies to improve urban ecosystem resilience

In the contemporary debate about key issues of urban science (sustainability, environment, governance, etc.) resilience has a fundamental role. It is defined as the ability of a complex system to cope with external stresses through adaptation and mutation strategies and to return to an equilibrium state (not necessarily equal to the original one). In particular, ecosystem resilience is based on the concepts of diversity (biodiversity), redundancy (ecological variability), cycles of adaptation (multiple equilibrium states), and interaction between spatial scales (hierarchy) and temporal (activation of different times responses). In an urban context with high soil sealing, such as historical centers, it is essential to find new methods and application techniques that will be able to integrate the use of natural solutions with artificial ones and increasing ecosystem resilience and urban ecological quality. In fact, in these contexts, the percentage of permeable and green public areas available is not capable of performing ecosystem functions: so, it is necessary to act on private property through green punctual interventions (such as green roofs and walls), that may become fundamental elements of the municipal ecological network. In fact, these actions bring benefits from several points of view (environmental, economic, building comfort, etc.) The aim of the paper is to study the relationship between technical aspects and urban policies, and, in particular, to resolve the main question: how to encourage private owners to invest in green interventions for improving buildings’ efficiency and environmental quality? In this process it is important to define sustainable policies acting on private property that consider both individual and global interests. Further, the article focuses on different case studies and examples taken from the United States with the objective to define similar policies in the Italian context