Abstract

Most of the significant changes on the environment have resulted from individually minor but collectively significant human actions and decisions. This kind of consequences has been defined Cumulative Effects (CE) and their systematic consideration can be attributed to the scientific basis and institutional context of Environmental Assessment (EA) theory and practice. However, although Strategic Environmental Assessment (SEA) has been largely recognised as one of the most appropriate procedure to support spatial and land use plans in managing CE; the advancement in integrating the assessment of CE into SEA practice has been often stated slow to evolve, suggesting a gap between SEA theory and practice in treating cumulative effects and confirming that further investigation on this subject is required. This research aimed to propose and apply a methodological approach to improve the consideration of CE in SEA of spatial plans, by focusing on the Italian spatial planning system and urban regions. It was developed according to the main findings and shortcomings emerging from the academic literature and the exploration of SEA practice through: an international expert survey; a systematic review of SEA documents; and a couple of real-life SEA case studies following during the research period. Among the most important were: the lack of scoping of relevant resources (or Valued Ecosystem Component); the scarce exploration of future decisions and consequences; and the requirement of a more evidence-based assessment of CE. The methodological approach was then developed for SEA of regional spatial plans, consisting of four main tasks: the selection of significant valued resources; the identification of other relevant decisions (projects, plans and policies) which together with the spatial plan could contribute to CE; the generation of land use scenarios; and the prediction of CE through indicators. Then, the methodological approach was tested in a case study selected within the peri-urban region of Milan, representing one of the most urbanised and industrialised part of Italy, with significant urban pressures on existing protected areas and remaining rural patches. Firstly, the regional green infrastructure was selected as the most important regional valued resource (or VEC); then, three important ‘future policies’ were identified (i.e. highway transportation corridor, protected areas conservation plans, and rural policies). Subsequently, a set of future land use scenarios were developed and made spatially explicit, starting from a couple of regional land use maps. Then, the regional cumulative effects on the selected valued resource (e.g. habitat fragmentation, surface runoff, etc.) were assessed against a range of future conditions through a core set of indicators, mainly quantitative and spatially explicit, simulating relevant environmental processes, such as hydrological cycle, local surface temperature, ecological connectivity. They were all selected and computed starting from land cover data, allowing the combined effects to be quantified and land use scenarios to be compared. The results mainly showed that the method provided an applicable means to, firstly, transfer policies and decisions into maps, and then, predict their combined effects on selected VEC. Moreover, it can be straightforwardly included in SEA of regional spatial plans in order to support a more evidence-based CE analysis, by adding spatial thinking to decision-makers and improving the understanding and the perception of the cumulative consequences of their “minor” decisions under uncertain future policy contexts.