Spatio-Temporal Scales 
In impact assessment, system boundaries are the spatial and temporal frame within which effects are analysed. While boundaries that are drawn too wide will result in bloated data requirements, loss of focus and may obscure relevant findings amongst non-relevant data, boundaries that are drawn too narrow will cause misleading results because relevant impacts are not considered. Adequate definition of both spatial and temporal system boundaries is therefore essential. Leakage effects and indirect land use changes pose a particular challenge because they require a very wide boundary setting to be detected. A structured way to include effects at large spatial and temporal scales is life cycle assessment (LCA). 
 
What are spatio-temporal scales?
 
In impact assessment, system boundaries are the spatial and temporal frame within which effects are analysed. They must always be defined at the start of an assessment. Effects that occur outside of the defined system boundaries are not considered.
 
Why is the definition of spatio-temporal scales essential for the assessment of soil management and soil function changes?
 
Generally speaking, system boundaries determine what is analysed in assessments of agricultural management impacts, and what is ignored. Adequate definition of both spatial and temporal system boundaries is therefore essential. While boundaries that are drawn too wide will result in bloated data requirements, loss of focus and may even obscure relevant findings amongst non-relevant data, boundaries that are drawn too narrow will cause misleading results because relevant impacts are not considered. In this respect, leakage effects and indirect land use changes pose a particular challenge because they require a very wide boundary setting to be detected (Lambin & Meyfroidt, 2011).
 
How can spatio-temporal scales be defined in the context of assessment of soil management and soil functions for a sustainable bioeconomy?
 
System boundaries must be defined in such a way that the spatial and temporal scale includes all relevant, potential impacts. Inclusion of effects up to a global scale may be required to account for effects like leakage or indirect land use change, where local management decisions result in effects emerging in other world regions. At the temporal scale, the definitions must be sufficiently wide to capture improvements or deteriorations of soil functions or ecosystem service provision, which often only emerge after considerable time lags (Fremier et al., 2013). In the context of agriculture, consideration of multiple years is highly recommended in order to account for long term management effects, crop rotations, pre-crop effects and inter-annual yield variability (Preissel et al, 2015; Zhang et al, 2017).
 
A structured way to include effects at large spatial and temporal scales is life cycle assessment (LCA). LCA focuses on environmental impacts of products and production processes (Roer et al., 2013). It seeks to integrate effects from all stages of the product cycle: from pre-production and production to use and disposal. However, as this requires a substantial amount of data, a number of studies use only partial LCA instead, replacing the underlying “cradle-to-grave” concept with “cradle-to-farm gate” or “farm gate-to-farm gate” (Brock et al. 2016, Hijazi et al., 2016). The inclusion of large spatio-temporal scales in LCA however, comes at the cost of a high requirements for data and calculatiuon time. This limits the number of impact areas that can be covered and therefore results in a trade-off between spatio-temporal and thematic detail. Where a high number of impact areas is to be assessed, it may be advisable to resort to multi criteria analysis (MCA) where spatial and temporal scale at not formalised and can be adapted to the context of the research.
 
Adequate boundary setting is necessary to ensure the validity of assessment results. Godinot et al. (2016) show the relevance of including production, transport and losses of inputs into the assessment of nitrogen use efficiencies. Likewise, Roer et al. (2013) demonstrate the considerable effect boundary setting has on assessment results by calculating LCAs of the same products using different system boundaries.