| NSF Org: |
BCS Division of Behavioral and Cognitive Sciences |
| Recipient: |
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| Initial Amendment Date: | July 20, 2015 |
| Latest Amendment Date: | May 9, 2016 |
| Award Number: | 1546061 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Deborah Winslow
BCS Division of Behavioral and Cognitive Sciences SBE Directorate for Social, Behavioral and Economic Sciences |
| Start Date: | August 15, 2015 |
| End Date: | July 31, 2017 (Estimated) |
| Total Intended Award Amount: | $37,756.00 |
| Total Awarded Amount to Date: | $43,756.00 |
| Funds Obligated to Date: |
FY 2016 = $6,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
1960 KENNY RD COLUMBUS OH US 43210-1016 (614)688-8735 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Columbus OH US 43210-1106 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Cultural Anthropology |
| Primary Program Source: |
01001617DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.075 |
ABSTRACT
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.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This project examined whether and how the demographic dynamics at the herd and household level constrain the growth of livestock populations in pastoral systems. The researchers used agent-based modeling to examine the impact of the domestic cycle of households on the demography of family herds and ultimately on regional livestock populations. The goal was to build three agent-based models to model: (1) herd demography; (2) household demography; and (3) coupled herd-household demography. We have completed the herd demography model and are in the process of completing the other two models.
We used the herd demography model to examine the role of scale (herd size) stochasticity (in mortality, fertility, and off take rates) on herd growth in African pastoral systems. We derived the mortality, fertility, and offtake rates from a review of the literature. Our model is relatively simple but captures the key dynamics of the family herds in African pastoral systems in which herds consists of animals in different age and sex classes (e.g., calves, heifers, bullocks, cows, bulls) that each have different mortality and offtake rates.
The simulations we conducted with the herd demography model confirm the findings from previous studies that scale and stochasticity matter in terms of herd growth and survival: the smaller the starting herd size, the greater the risk of herd death. Further, smaller herds are more likely to decline than larger herds. However, our study shows that there is no clear herd-size threshold. While the risk is higher for smaller herd sizes, the risk of herd death is always present, and even large herds remain roughly as likely to decline over time. It is thus better to think of the herd-size threshold not as one number but as fairly weak effect in which larger herds are more likely to survive and to grow, but in which demographic and environmental stochasticity can easily shift herds between trajectories of growth and decline.
Our project underscores the advantages to using agent-based models to examine questions about the demographic dynamics. It is easy to do multiple experiments and generate large datasets. In addition, agent-based models are well suited to explore the role of heterogeneity and stochasticity in demographic processes. In addition, the methodological tool also shapes our conceptual models of these processes: our agent-based model shows that pastoralism is fundamentally a high-risk strategy. Our simulations corroborate what we have observed in the field, that there are enough poor pastoralists who escape poverty and wealthy pastoralists that become destitute for pastoralists to believe they can overcome the challenges with hard work and a dose of luck.
The findings from the simulations with our family herd demography model have practical implications for pastoral development, in particular for restocking projects that aim to help impoverished pastoralists. A number of development organizations have used restocking projects to help households that have lost their livestock during the droughts by giving them livestock to rebuild their family herds. While the projects may have several benefits for the recipients, including immediate food relief, restocking has little long-term impact on livelihood security. Generally, only a few households are able to achieve self-sufficiency. Our simulations show that scale and stochasticity matter for herd dynamics and that for restocking efforts to be successful the number of livestock given to impoverished households needs to be sufficiently large in order to overcome the odds.
Last Modified: 08/06/2017
Modified by: Mark Moritz
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