Because of its hierarchical nested organization, properties and the evolutionary trajectory of a certain system at a particular focal scale will depend on and will influence the states and the dynamics of other nested systems operating at scales above and below. The dynamics of how what takes place at one scale influences what happens at other scales are considered cross-scale effects. When such dynamics at the same or at different scales are not properly aligned, as for spatial or temporal frequencies, scale mismatches arise and interactions may result, leading to disruptions of system properties, inefficiencies, and/or loss of important components. For SESs, an improvement in the traditional hierarchical model that includes cross-scale effects and scale mismatches has been proposed and called panarchy. A panarchy is a nested hierarchy of SESs that explicitly recognizes the cyclicity of changes within scales (i.e., the adaptive cycle with its four phases) as well as the cross-scale dynamics acting as top-down constraints or bottom-up novelties, combining learning with continuity and creation with conservation.
There are potentially multiple connections between phases of the adaptive cycle operating at one scale and those operating at smaller and larger scales and two of these have been identified as particularly significant. An interaction of revolt is a bottom-up connection that can cause a critical change in one cycle at smaller scale to cascade up to a vulnerable stage in a larger and slower one. Revolts can occur either because lower-level cycles are synchronized (e.g., forest-pest dynamics), and thus all enter a back loop at the same time, or because they are tightly interconnected (e.g., forest-fire dynamics), so that a back-loop transition in one cycle triggers such a transition, including collapse, in the other cycles. An interaction to remember is a top-down link where larger scales offer both opportunity and constraints to possibilities for what may happen in lower-level adaptive cycles by providing memories of the bounding conditions. Memory in an ecological system can be in the form of a seed bank or climate, whereas memory in a social system is held in organizations, laws, social norms, and institutions. The fast levels invent, experiment, and test; the slower levels stabilize and conserve accumulated memory of past successful, surviving experiments.
As for previous systems' properties, the evaluation of cross-scale interactions is intrinsically linked to an historical analysis of system dynamics. Linking properties of systems across a panarchy by taking into account long periods or spatial extents is an operational way to address (1) how higher levels have constrained lower systems (i.e., identifying source of memory and novelty), (2) to quantify the interaction strength, and (3) to address time or spatial delay that occurs when transferring processing from one scale to another.
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