A Methodology to Address the Inner Areas Decline in Support of Sustainable Strategic Spatial Planning—The Case Study of Avellino Province (Italy)

The work concerns the fight against the decline and depopulation in the Inner Peripheries (IPs), a phenomenon taking place globally and throughout Europe, where it has reached an alarming dimension, causing regional disparities that threaten the achievement of Sustainable Development Goals. In Italy, where the term Inner Areas (IAs) is used as a synonym, more than half of the municipalities have the typical problems of IPs. As the latter have a supramunicipal nature, provincial strategic spatial planning is considered adequate to counter these critical issues, assuring a balanced and sustainable development in the social, economic, and environmental domains. To this end, after the state-of-the-art review, this paper proposes a methodology for the construction and mapping of a Decline Index, useful for spatially identifying the most critical municipalities which provide priority strategies to counteract decline through the Provincial Territorial Coordination Plan. The method is based on a multicriteria analysis approach in which Principal Component Analysis (PCA) is integrated and applied to the case study of the Avellino Province in the Campania Region (Italy), which contains many municipalities belonging to IAs. The proposed method is also useful in supporting regional planning and programming for territorial cohesion and sustainable regional growth.