A model of robustness tradeoffs in social-ecological system

Model Description

Feedback control systems in general exhibit inherent robustness-fragility tradeoffs. That is, by becoming very robust to a given set of disturbances for maintaining stability, feedback systems necessarily introduce hidden fragilities to disturbances outside this set. Even a small unanticipated disturbance can initiate cascading system-wide failures as a result. The model presented here demonstrates this phenomenon.

In Anderies et al. (2012), an agricultural production system is illustrated as an example of such feedback control systems. Here, farmers have an objective of continuously producing a certain level of yield (r) every year. They subtract their current yield (yout) from their target level (r), which shows a gap (u). Farmers refer to this gap (u) to adjust the size of their cultivated area for the next crop season. When the output of cultivation in the next cycle is available, it is again compared with their target level (r) to further adjust the size of their cultivated area. This cycle of "compare and adjust" is repeated indefinitely until the farmers reach their objective (zero gap).

From the perspective of institutions, it is clear that such feedback control mechanisms (i.e., sensing the yield and adjusting the cultivated area) are driven by the rules and norms adopted by the farmers. Institutions are thus critical for the robustness of such systems. However, if systems develop institutions that are too optimized to certain kinds of disturbances, they can become fragile to unfamiliar disturbances.


Anderies, John M, Elinor Ostrom, C. Folke, and B. Walker. 2012. “Aligning Key Concepts for Global Change Policy?: Robustness , Resilience , and Sustainability.” CSID Working Paper Series.

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