Modeling rangelands as complex adaptive socio-ecological systems: An agent-based model of pyric herbivory

Rangelands cover approximately one-third of the earth's land area, at least one billion people depend on these lands for their livelihoods, and most rangelands have been degraded by inappropriate land use practices. Overgrazing and suppression of fire have facilitated encroachment of woody plants in what formerly were more open grasslands. However, proper management of fire and grazing (pyric herbivory) can mitigate woody plant encroachment. Although the basic ecological dynamics of rangeland ecosystems are well known, the long-term effects on local vegetation dynamics of ranch-level management decisions, particularly those involving the use of prescribed fire to limit woody plant encroachment, are less well understood. As a proof of concept, we describe a spatially explicit agent-based model of pyric herbivory that integrates biophysical and managerial components to simulate shifts in canopy cover of woody plants, forage production, and cattle production resulting from ranch-level management decisions to adjust grazing pressure and prescribed fire regimes.