by Craig Allen (visiting researcher at SLU), Leader of the Nebraska Cooperative Fish and Wildlife Research Unit, University of Nebraska-Lincoln
The identification of the scales of structure present in a system is non-trivial and has important implications for understanding the resilience of systems. Discontinuity analysis, related to the description of complex adaptive systems as panarchies, has been used to identify scales, thresholds, opportunities and transformations. Most research on resilience and panarchy in complex systems acknowledges scale, and the importance of cross-scale linkages, but seldom extends beyond description. The model of cross-scale resilience developed by Peterson and others (1998) provides a framework for the analysis of functions within and across scales, and discontinuity analysis provides a method for objectively identifying scales present in a system and assessing resilience.
There are management applications of discontinuity theory. Identifying thresholds allows for the identification of intervention points, those points in the adaptive cycle where a transformation may most easily be implemented. Increasing variance and flickering are indicators of impending ecological transition. Variability within complex systems is heightened where there are shifts in scales of process and structure, that is, where discontinuities occur. This suggests that it is possible to identify those variables that are most likely to exhibit increased variability prior to systemic regime shifts by identifying those species already subject to heightened variability at scale breaks, which would allow more targeted and effective monitoring to determine when there is an increased probability of critical transition.
Ecologically dynamic and unusual phenomena occur at discontinuities, and this provides insight into the organization of complex systems. Increased variability at transitions between scales is associated with species invasions and extinctions, nomadism and population variability. From a complex systems perspective, this suggests that although high variation in resource abundance and location in space and time is a hardship for some species, it is an opportunity for others. Discontinuities between scaling regimes in panarchies are arenas of "experimentation", meaning that biodiversity and ecosystem processes are exposed to constant innovation and novelty. This has implications for resilience, and provides confirmation of the characterization of discontinuities as scale breaks indicating cross-scale change in structuring regimes.