How green is a “Green City”? A review of existing indicators and approaches

More than half of the world’s population currentlylives in cities and, consequently, urbanization hasbeen among the major drivers of global environmentalchange. The fast urban growth, likely to result ina share of 75 % of people living in cities by 2050, hasresulted in the development of cities which are unfriendlyto people as well as to the environment. Asa contribution to reverse this trend, various institutionshave organized competitions between citiesby ranking the degree of their “greenness,” based onquantitative and qualitative indicators accessing economic,social and environmental performances. Mostof these competitions have only been conducted onceand the studies include different cities because theirattendance was voluntarily. In this paper we analyzethe potential of city rankings to contribute to a positivedevelopment of cities. The first part of this paperanalyzes and defines the “Green City” conceptcomparing the definitions in the literature. Three keywords have been identified to characterize a“Green City”: the “environmental quality,” “humanwell-being,” and the “political and social action” thataims at the first two dimensions. For measuring the“greenness” of cities, we analyzed the urban indicatorsof four popular indices, representing 13 categorieswhich were then grouped into the three “GreenCity” dimensions. Regarding “environmental quality”and “human well-being,” quantitative indicatorsare used, while qualitative indicators seem bettersuited to define the “societal and political action.”By monitoring the quantitative indicators over time,we are also able to assess the “Green City” performancesand at the same time verify the effectiveness of“social and political action.” Thus, more clarity in the“Green City” definition is achieved, making constantmonitoring of cities’ performances possible. The useof quantitative and multidimensional indicators canbe a valuable tool for urban governance and planning.