Cross Scale Interactions

A panarchy has three ingredients, (1) subsystems of adaptive cycles that represent system dynamics at a specific scale range, (2) dynamic systems that occur at different scale ranges (hierarchical levels), and (3) coupling of those systems across scales. All of these structures are posited to change in phases described by the adaptive cycle, but at a given scale. Panarchy links these structures across scales, and suggests that interactions can go from smaller, faster levels to broader, slower levels (or up-scale connections). Panarchy also suggests that the slow and broad processes and structures influence those that are faster and smaller (i.e., the subsystems and down-scale influences). But these connections are ephemeral, becoming dominant at certain times and dormant at others.

There are potentially multiple connections between phases at one level and phases at another level. The two most significant are the connections labeled as 'revolt' and 'remember'. Figure 1b indicates two levels of a vegetation panarchy, each at distinct scale ranges or domains, and linked by cross-scale connections of revolt and remember.

Up-scale linkages or connections have been named 'revolt', suggesting that small events can cascade up to larger scales. Most of the time, the larger, broader variables control the smaller and faster processes. This is classic hierarchical control. However, when a level in the panarchy enters an fi phase of creative destruction and experiences a collapse, that collapse can cascade up to the next larger and slower level by triggering a crisis, particularly if that level is at the K phase where resilience is low. One example is in the dynamics of fire-prone ecosystems. The lighting of a match in a forest, or a strike of lightning is a small, local phenomena. Under many conditions the local fire is either quickly extinguished or never begins a fire. However, under certain conditions (such as extreme droughts or low humidity), local ignitions can create a small ground fire that spreads to the crown of a tree, then to a patch in the forest, and then to a whole stand of trees. Each step in that cascade moves the transformation to a larger and slower level. A societal example occurs when local activist groups succeed in efforts to transform regional organizations and institutions, because they had become broadly vulnerable. Hence part of the connotation of revolt is used to describe how fast and small events overwhelm slow and large ones.

Figure 2 Two key cross-scale connections of a panarchy are revolt and remember. The revolt pathway depicts how small-scale (local and fast) variables can interact to create an upscale cascade. Revolt dynamics have been described for forest pest, forest fires, and disease outbreaks. Resources in the form of capital, connections, and memory from larger systems often help in the recovery of focal scale collapse, as indicated by the remember pathway.

Figure 2 Two key cross-scale connections of a panarchy are revolt and remember. The revolt pathway depicts how small-scale (local and fast) variables can interact to create an upscale cascade. Revolt dynamics have been described for forest pest, forest fires, and disease outbreaks. Resources in the form of capital, connections, and memory from larger systems often help in the recovery of focal scale collapse, as indicated by the remember pathway.

And that effect could cascade to still higher slower levels if those levels had accumulated vulnerabilities and rigidities.

The down-scale interactions in panarchy are captured by the phrase 'remember'. As shown in Figure 2, this type of cross-scale interaction is important at times of change and renewal. Once a catastrophe is triggered at a level, the opportunities and constraints for the renewal of the cycle are strongly organized by the K phase of the next slower and larger level. After a fire in an ecosystem, for example, processes and resources accumulated at a larger level slow the leakage of nutrients that have been mobilized and released into the soil. The options for renewal draw upon the seed bank, physical structures, and surviving species that form biotic legacies that have accumulated during the growth of the forest. It is as if this connection draws upon the accumulated wisdom and experiences of maturity - hence the choice of the word remember.

Panarchy theory describes at least three categories of change in complex ecological systems. These categories include gradual or incremental change, adaptive change, and transformative change. Incremental changes occur slowly and predictably, as systems mature. Adaptive change occurs after disturbances, when the system has the potential to change into a qualitatively different state. Alternative states in ecosystems occur when resilience of the system is exceeded. That alternative state occurs at one level of the panarchy. Transformational change occurs when multiple levels of the panarchy change as a result of cross-scale linkages and lead to fundamentally new types of structures, processes, and controls.

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