Robustness, institutions, and large-scale change in social-ecological systems: the Hohokam of the Phoenix Basin

Model Description

This is a model that illustrates the relationship among levels of (1) population, (2) human-made capital, (3) natural capital , and (4) resource consumption. The key insight to be gained from the model is that as the ratio of capitalization in human-made infrastructure over human population is varied in the parameter space, the dynamics of natural capital changes and becomes vulnerable to different disturbance regimes. That is, as humans grow in population and over-invest in capitalization/physical infrastructure (e.g., irrigation infrastructure) to become robust to one disturbance regime (e.g., local droughts), they necessarily become vulnerable to different disturbance regimes (e.g., regional droughts, collective action problems, etc.). The model is inspired by the historical case of Hohokam Cultural Sequence (see the case in the case library for more details).

The dynamics of the natural capital are represented by the two state variables: (1) harvestable wild resources biomass (resource type 1) and (2) soil fertility (resource type 2). The population depends on these two resource systems for subsistence. Resource type 1 is primairly used for obtaining protein-based nutrients. Resource type 2 is where people obtain carbohydrates. When there is little or no irrigation infrastructure, the population is mainly hunter-gatherers and they depend on resource type 1. If the society heavily invests in irrigation systems, the population depends more on resource type 2.

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This model has 19 parameters. You can set their values below.
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