EAGER: Modeling Coupled Herd and Household Dynamics in Pastoral Systems

人类学家使用“牧业”一词来指代依赖畜牧业的经济体。长期以来，对于那些生活在生产力较低、自然资源稀少的环境中的人来说，牧业一直被视为一种很好的战略。然而，即使是牧民也不得不关心如何平衡他们饲养的动物数量与可供饲养它们的牧场和可供照料它们的劳动力之间的平衡。事实上，种群模型显示，牲畜种群有可能呈指数级增长，并超过其环境的承载能力。但经验证据表明并非如此：在现实世界中，牧场牲畜的数量相对稳定。那么，问题是如何实现这种平衡？到目前为止，最流行的解释是干旱、疾病和其他灾难控制了牲畜数量。但该奖项支持的研究将检验另一种解释：人口动态--家庭规模随着时间的推移自然扩大和缩小--在畜群和家庭层面上运作，可能会限制地区牲畜种群的增长。如果这真的是这样，正如这个跨学科研究小组所建议的那样，那么它对牧民社会的发展干预具有影响。改善兽医健康和减少干旱脆弱性将改善牧民的生活，而不一定会威胁到自然资源基础。研究小组将开发一种以代理人为基础的模型，以审查家庭的家庭周期对家庭畜群人口统计的影响，并最终对区域牲畜种群的影响。来自以前研究的经验数据将被用来对基于主体的模型进行参数化。该模型将模拟最初100户人口的国内周期及其250年(或10代)的家庭牛群的人口统计过程。这些模拟将允许研究人员通过检查初婚年龄的变化、儿子数量的增加或一夫多妻率的增加的影响，来检验家庭周期如何影响群体人口统计学。此外，这些模拟将被用来检验区域牲畜种群的增长对畜群规模阈值变化的敏感度，即较低的阈值是否会导致区域一级牲畜种群的更强劲增长。这项研究的结果将提供对牧区社会牲畜种群动态的洞察，特别是为什么在没有干旱和疾病等重大灾害的情况下，这些种群似乎没有增加的问题。

Anthropologists use the term "pastoralism" to refer to economies that depend on raising livestock. Pastoralism has long been viewed as a good strategy for people who live in less productive environments with few natural resources. 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 oustrip 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 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 pastoral societies. Improving veterinary health and reducing drought vulnerability would then improve the lives of pastoralists without necessarily threatening the natural resource base. 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. Empirical data from previous studies will be used to parameterize the agent-based model. The model will simulate the domestic cycle of an initial population of 100 households and the demographic processes of their family herds for 250 years (or 10 generations). 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, increase in the number of sons, or increase in 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.