1.1. The sustainable city
There is no accepted definition of a sustainable city, and as it happened with the concept of sustainable development, many interpretations exist of which characteristics a city should present to be considered sustainable, and many are the criteria and indicators developed to assess them. They often include aspects of urban planning and community development (see www.rec.org).
Some cities have been developing their own sustainability indicators, to try and measure quality of life issues in a meaningful way. This has usually been done as a result of Local Agenda 21 consultations or in response to national government guidelines.2 Beside environmental criteria (water and energy saving, waste recycling, transportation, etc.), quality of life issues are central to all the various definitions of a sustainable city. Aspects such as “amount of public green spaces per inhabitant”, “public parks” and “recreation areas” are often mentioned as important factors to make the city liveable, pleasant and attractive for its citizens.
It is strongly believed that developing more sustainable cities is not just about improving the abiotic and biotic aspects of urban life, it is also about the social aspects of city life, that is—among others—about people’s satisfaction, experiences and perceptions of the quality of their everyday environments (see also Beer, 1994). In the context of this study, the relation between urban parks and city sustainability is addressed through the investigation of the value of urban nature as provider of social services essential to the quality of human life, which in turn is a key component of sustainable development (see also Prescott-Allen, 1991). Fig. 1 illustrates the conceptual links and relationship assumed between urban park and city sustainability.