GIS for SEA Manual: Improving the Evidence Base in SEA

A large number of environmental management and planning decisions are based on methodologies that utilise the spatial analysis tools provided by conventional GIS technologies (e.g. digital mapping or modelling of future changes). In the context of SEA, spatial data and GIS allow for consideration of spatio-temporal dimensions common to environmental, biodiversity and planning issues. This is of particular significance in land-use planning, where the potential significance and magnitude of an impact is largely dependent on the spatial location of proposed actions and affected receptors at a given time. The intrinsic spatial nature of land-use planning and the need to integrate environmental considerations into plan-making give GIS the potential to augment existing SEA methods and plan-making procedures. Similarly, the spatio-temporal implications of planning decisions on Natura 2000 sites make GIS a significant tool for assessing potential adverse effects on their integrity. This is achieved by incorporating spatial evidence into the process and by facilitating assessment of alternatives (or alternative ecological solutions, when necessary, in AA), definition of mitigation measures and monitoring of changes over time. In this context, data collation and analysis through GIS can support a more baseline-led approach to environmental planning and decision-making. GIS provide the means to integrate and spatially assess multiple environmental and planning considerations in a single interface, supporting the systematic prediction and evaluation of spatially distributed and cumulative impacts, a key assessment consideration in SEA. The SEA Directive gives special consideration to the cumulative nature of potential environmental impacts. Cumulative impacts can derive from several individual aspects of a plan/programme (e.g. pollution, loss of habitats) having a combined effect. Cumulative effects also arise where each of several aspects has insignificant effects but together they have a significant additive or synergistic effect (i.e. greater than the sum of individual effects). Evaluating co-occurring environmental resources and their status or sensitivity through GIS can help address cumulative effects. This is also of relevance to AA.