Municipal masterplans and green infrastructure. An assessment related to the Metropolitan Area of Cagliari, Italy

Recent research has proposed a GIS-based methodology to map a regional green infrastructure (RGI) by assessing patches’ suitability to be included in the RGI on the basis of four components as follows: natural value, conservation value, landscape value, and recreational value. This study builds upon such research with the aim to identify planning policies that can foster the enhancement of the RGI by increasing one or more of its components at the sub-regional scale. To this end, the RGI suitability map is overlaid with the planning schemes of the municipal master plans of three towns belonging to the Metropolitan City of Cagliari (Italy), and multiple linear regressions are performed. Results from this analysis show to which extent the zoning types identified in the city masterplan are related to high or low RGI suitability values, hence allowing for detecting those zoning types that should be targeted by the metropolitan city plan, if the RGI is to be improved, and for identifying appropriate planning actions to pursue this goal. The outcomes of the study imply that the eligibility of a land parcel to be part of the RGI depends on a number of factors strictly related to planning policies entailed by the zoning schemes of the municipal masterplans, such as presence and spreading of conservation and safeguard areas within the urban fabrics, improved accessibility of historic and natural landmarks, planned use of nature-based solutions within the regulating codes of municipal masterplans, improvement of habitat quality in the spatial context of rural areas. Main limitations of the proposed methodology can be recognized in the fragile theoretical foundations concerning the assessment of the value of recreational areas, and in the need for structured integration of nature-based solutions into the assessment of eligibility of land parcels to be included in the RGI. These limitations act as recommendations for future research.