Modeling Pastoral Dynamics

牧业指的是依赖饲养牲畜的经济体系。人类学家长期以来一直解释说，对于生活在不适合农业的环境中的人来说，畜牧业是一个很好的战略。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--随着时间的推移，家庭规模的自然扩大和缩小--在牲畜群和家庭层面上运作，可能会限制地区牲畜种群的增长。如果情况真的如这个跨学科研究小组所建议的那样，那么它对依赖畜牧业的经济系统的发展干预具有影响。结果将传播给投资于改善兽医健康和减少干旱脆弱性的组织，以改善依赖畜牧业的经济体的生计。此外，该项目还培训学生使用复杂的计算方法和分析方法。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。以前研究的数据将被用来对基于代理的模型进行参数化。该模型将被用来模拟家庭的家庭周期及其家庭牛群在不同实验条件下的人口统计过程，在不同的实验条件下，改变牛群和家庭的规模和组成，并运行一代或十代(25年或250年)的模拟。这些模拟将使研究人员能够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，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。这项研究的结果将为牧民社会的牲畜种群动态提供洞察，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。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.