The definition of system boundaries is an obligatory first step in every impact assessment. System boundaries represent the thematic and spatio-temporal frame within which an assessment is conducted. Impacts that occur outside of this frame are not considered.
The reason for setting system boundaries is threefold: First, potential users of the assessment results should be able to quickly find the information relevant to them. Having to search for this information amidst large amounts of other data would reduce the assessments usefulness. Second and more important, the number of effects and impacts that could possibly be investigated is too high to be handled in a single assessment. Only by restricting an impact assessment to a predefined frame, the method becomes operable. Third, the choice of relevant impact categories varies with the system boundaries. Adequate impact categories and respective indicators can only be identified with clearly defined boundaries.
Setting system boundaries should be done with great deliberation and properly documented. Decisions taken at this step will strongly affect the assessment’s results. In particular, decisions are required on:
a) Purpose of the assessment (decision making level) (Who is the assessment for?)
b) Spatial and temporal frame (Where & when are impacts assessed?)
c) Impact areas to be assessed (What type of impacts are assessed?)
Purpose of the assessment (decision making level):
Generally speaking, assessments should be designed to be relevant for an intended target group, e.g., by focussing on the impacts of different options available to a group of decision makers. Farmers, for example, may require a different set of information from an impact assessment than policy makers or members of the local administration (for more information see section III.2: Purpose & Decision-Making Level).
Spatial and temporal frame:
The Purpose of the assessment also influences the setting of the spatial and temporal frame. Another influencing factor are the impact areas that are analysed. Generally speaking, the frame must be set wide enough include all relevant impacts, but narrow enough to focus research efforts and avoid bloated data requirements (for more information see section III.3: Spatio-temporal scales).
Finally, the impact areas for which effects are to be analysed and the methods and indicators by which they are assessed need to be chosen. The BonaRes Assessment Platform provides information on more than one hundred impact areas and on the methods and indicators to assess them. However, in any given assessment only a small selection of these impact areas can and should be used. The impact areas supported by the platform correspond to the assessment perspectives Ecosystem Services, Resource Use Efficiency and Sustainable Development Goals (for more information see section V.1: Impact Area selection).