Abstract Body

The assessment of the Green Infrastructure (GI) of a city is interesting to improve its sustainability as GI provides key services for its inhabitants. The GI of Zaragoza city (Spain) was evaluated using an index (NAT&COM) which gives values in the range 0-10 for two aspects, naturalness and complexity. Naturalness refers to the components of the site, natural (plants, soil) and artificial (stone, plastic, metallic, etc.), measured as the percentage of UGI natural area versus the percentage of artificial area in the UGI (area with artificial components). Complexity refers to the hydro-geomorphological and natural dynamic features present in the GI. Ninety GI units (urban parks, community gardens, riparian zones, street trees, roundabouts, green walls, cemeteries, forests and semi-natural environments) were assigned naturalness and complexity (NAT&COM) values in the range 0-10 based on their degree of artificial versus natural components and on their degree of natural distribution of hydro-geomorphological features respectively. A clear separation between low NAT&COM sites located in the urban centre and high NATt&COM sites located in suburban zones was observed, indicating that GI sites in the urban centre are artificially designed and natural peri-urban sites are much less artificially modified. A multivariate analysis; Principal Component Analysis (PCA) was performed using qualitative and quantitative characteristics (natural versus paved soil, soil depth, artificial components in the subsoil, presence of road traffic, plant cover, plant strata, naturalness, complexity) of the GI of Zaragoza, it was found that 60% of the data variability in the first three components, showing different groups of GI units grouped through natural versus regularly distributed components (first PCA axis, 35% of total data variability) and through presence of artificial versus natural components (second PCA axis, 12% of total data variability). These results indicate a high extrapolation between artificially designed GI sites and natural and complex sites in Zaragoza. Intermediate GI sites which combine naturally distributed components (either keeping their natural features or creating a natural design) and artificial facilities that provide security and comfort to people, would enrich the GI of Zaragoza.