The relationship between settlement population size and sustainable development measured by two sustainability metrics

This paper reports on a study of the relative sustainability of 79 Irish villages, towns and a small city (collectively called 'settlements') classified by population size. Quantitative data on more than 300 economic, social and environmental attributes of each settlement were assembled into a database. Two aggregated metrics were selected to model the relative sustainability of settlements: Ecological Footprint (EF) and Sustainable Development Index (SDI). Subsequently these were aggregated to create a single Combined Sustainable Development Index. Creation of this database meant that metric calculations did not rely on proxies, and were therefore considered to be robust. Methods employed provided values for indicators at various stages of the aggregation process. This allowed both the first reported empirical analysis of the relationship between settlement sustainability and population size, and the elucidation of information provided at different stages of aggregation. At the highest level of aggregation, settlement sustainability increased with population size, but important differences amongst individual settlements were masked by aggregation. EF and SDI metrics ranked settlements in differing orders of relative sustainability. Aggregation of indicators to provide Ecological Footprint values was found to be especially problematic, and this metric was inadequately sensitive to distinguish amongst the relative sustainability achieved by all settlements. Many authors have argued that, for policy makers to be able to inform planning decisions using sustainability indicators, it is necessary that they adopt a toolkit of aggregated indicators. Here it is argued that to interpret correctly each aggregated metric value, policy makers also require a hierarchy of disaggregated component indicator values, each explained fully. Possible implications for urban planning are briefly reviewed.