Defining a procedure to identify key sustainability indicators in Spanish urban systems: Development and Application

Urban population has exponentially growth in the last decades and as consequence, cities concentrate part of global environmental burdens among other impacts. Therefore, the use of indicators to evaluate the cities in order to achieve their better and more sustainable future was receiving special attention in the last years. Accordingly, the considered indicators would reflect the traditional three pillars of sustainability: social, economic and environmental. In the present study, Classification And Regression Trees (CART) and Random Forest, were applied over a case study in which the sustainability of 31 Spanish cities was evaluated considering 38 indicators. The main goals were to identify the key indicators and to quantify the corresponding thresholds to define a sustainable city. The key indicators identified were: “woman unemployed rate”, “city unemployment rate” and “Municipal Solid Waste collected” and the corresponding thresholds are 14 %, 16 % and 423 kg inhabitant-1 year-1 respectively. In addition, the sustainability of 32 different Spanish cities was evaluated with these three indicators and thresholds to validate the achievements. According with the results, urban sustainability could be evaluated considering only three indicators with a high degree of accuracy, providing information to policy makers without the requirement of compiling a large amount of data.