How much green is needed for a vital neighbourhood? In search for empirical evidence

In this paper, we attempt to find empirical evidence for the proper size of the Polish eco-spatial index, known as the Ratio of Biologically Vital Areas (RBVA). The objective is to establish the minimal proportion of green space required for good environmental performance in neighbourhoods. Eighteen neighbourhoods (representing the most popular type of residential areas consisting of multistorey buildings) located in Warsaw and characterised by different RBVA values (varying from ca. 20% to ca. 70%) were chosen as the study area. Different types of measurements and calculations were performed to verify the relationships between the size of the RBVA and selected environmental features (e.g., air temperature and humidity, floristic diversity, butterfly species richness, surface outflow, etc.). Based on these values, a threshold of 45% RBVA was recommended as the minimum, which guarantees environmental performance in the neighbourhoods to certain extent. Eco-spatial indices can be recommended as a useful planning tool for new projects and for evaluation and enhancement of existing urban structures, including residential areas. It should be stated that these indices are not the only measures for green space planning, because they do not refer to the major residents' needs (e.g., social interaction, recreation). (C) 2013 Published by Elsevier Ltd.