Modeling Pastoral Dynamics

January 20, 2020

Modeling Pastoral Dynamics

National Sience Foundation logo.

Congratulations to Dr. Mark Moritz (PI) and Dr. Ian Hamilton (EEOB/Mathematics), Dr. Rebecca Garabed (Preventive Veterinary Medicine), and Dr. Jason Thomas (Institute for Population Research) for their recent award of a National Science Foundation (@NSF) Grant for their project Modeling Pastoral Dynamics. The team will develop an agent-based model of coupled herd- household demography in pastoral systems.

The public abstract for this grant explains that,

Pastoralism refers to economic systems that depend on raising livestock. Anthropologists have long explained that pastoralism is a good strategy for people who live in environments inhospitable to agriculture. However, even pastoralists have to be concerned about balancing the number of animals they keep with the pasture available to feed them and the labor available to care for them. Indeed, population models show that livestock populations have the potential to grow exponentially and outstrip the carrying capacity of their environments. But empirical evidence indicates otherwise: in the real world, pastoral livestock populations are relatively stable. The question then is how is this balance achieved. Until now the most popular explanation has been that droughts, diseases, and other disasters keep livestock populations in check. But the research supported by this award will test an alternative explanation: demographic dynamics -- the natural expansion and contraction of family sizes over time -- operating at the livestock herd and household level may constrain the growth of livestock populations regionally. If this is indeed the case, as this interdisciplinary research team proposes, then it has implications for development interventions in livestock-dependent economic systems. Results will be disseminated to organizations invested in improving veterinary health and reducing drought vulnerability to improve livelihoods in livestock-dependent economies. In addition, the project trains students in sophisticated computational methods and analysis. 

The research team will develop an agent-based model to examine the impact of the domestic cycle of households on the demography of family herds and ultimately on regional livestock populations. Data from previous studies will be used to parameterize the agent-based model. The model will be used to simulate the domestic cycle of the household and the demographic processes of their family herds under different experimental conditions in which the size and composition of herds and households is modified and running the simulations for one or ten generations (25 or 250 years). The simulations will allow the researchers to examine how the domestic cycle affects herd demography by examining the impact of changes in age of first marriage, increasing in the number of sons, or increasing polygyny rates. In addition, the simulations will be used to examine how sensitive the growth of regional livestock populations is to changes in the herd-size threshold, i.e., whether a lower threshold leads to stronger growth of livestock populations at the regional level. Findings from this research will provide insight into livestock population dynamics in pastoral societies, in particular the question of why these populations do not seem to increase in the absence of major disasters like droughts and diseases.

For any questions about the project, please contact Dr. Mark Moritz at

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