Abstract

Sustainability has always been a central factor in the long tradition of a nomadic pastoralist lifestyle in the Mongolian steppes. To understand how social complexity has developed in the region since the Bronze Age, it is necessary to examine the dynamics of the human-environment relationship. We used an agent-based simulation model called HouseholdWorld, developed by scientists at George Mason University in conjunction with archaeological research conducted by the National Museum of Natural History, to explore the interplay between ecology, herds, and humans in Mongolia. To better understand the human-environment dynamic, extreme weather events were researched and recreated in our model as a means of exploring adaptive capacity. Results indicate the importance of mobility and the delicate balance between the social and genetic benefits inherent in forming culture groups as opposed to problematic population clusters and competition for forage.

Hypothesis

Weather events have a significant impact on herd and human population dynamics and influence the formation of different social organizations and sustainable strategies.

Methods

• To test our hypothesis, we used an agent-based model called HouseholdWorld. HouseholdWorld was developed by George Mason University’s Evolutionary Computation Laboratory and GMU’s Center for Social Complexity.
  
  
• To provide the values for the model’s parameters, literature from such various fields as archaeology, ethnology, history, ecology, environmental studies, range management, and others were utilized.
  
  
• To validate our parameters, additional sources of data and field surveys were examined to corroborate our values.

Parameters

Four Properties

• Main Properties
• Seasonal Properties
• Rules
• Default Events

Default Events Parameters

• StartTime
• Duration
• BiomassAbundance
• BiomassGrowthRate
• AnimalGrowthRate
• AnimalStarvationRate
• AnimalDeathRate

Output

This Figure shows the the annual cycles in our artificial society when there is a relatively stable environment and no severe weather events.

Reproduction occurs during the “spring” to early “summer” of seasons 3, 4, and 5, and there is a slight decline from annual mortality, off-take, and starvation.

When the same artificial society is impacted by a mild zud (winter storm), there is a sudden and significant decrease in herd size. Zuds are characterized by an unavailability of forage, which was simulated as a 30% reduction in biomass. Total stock mortality for a mild event is under 20%, and recovery is relatively quick.

The most disastrous zuds are often, though not always, preceded by a summer drought. This reduces the total availability of biomass and makes grazing even more difficult when a zud occurs. Stock mortality can reach over 40% during these events, and recovery is a longer process with more significant impacts.

Conclusions

Recovery from weather events and sustainability are influential on social organization. Preliminary results from our simulations show:

• Importance of Mobility. Earlier versions show that the most successful agents are those that increase the number of camps and distance between camp members. In times of stress, this strategy reduces competition for forage.
  
  
• Balance. There is a necessary but delicate balance between the inherent genetic and social benefits of forming a camp as opposed to the impairment of mobility and competition for resources.
  
  
• Spring is Crucial. Spring is a crucial point in the annual cycle for several reasons. Animal fat reserves are largely depleted from the winter and biomass has not yet started to become highly productive, but spring is also when the animals have their young. Both human and animal populations are then highly susceptible to zuds or other environmental changes.
  
  
• Variability. The agents that are most successful in recovering from an event are not always the wealthiest or those least impacted by a preceding summer drought. This is highly suggestive of the necessity of an adaptive lifestyle and corresponding social organization.

Severe zuds were defined as events with an animal mortality rate of over 20%. Years where zuds were preceded by a summer drought tended to be more severe, but this was not seen in every case. Theories about the cyclical nature of zuds are not firmly supported, suggesting the great variability of the Mongolian climate and the need for more research.

Acknowledgements

My participation in this research was made possible by financial assistance from the Honorable Max Berry to the Research Training Program (RTP). M. Sangrey provided invaluable support. My sincere gratitude goes to fellow RTP students for their advice and sagacity.

We would like to thank J. Alterman, N. Luna, M. Latek, C. Cioffi-Revilla, B. Frohlich, W. Fitzhugh, and W. Honeychurch for their collaboration in this interdisciplinary project. This project is funded by the Human and Social Dynamics Program of the U.S. National Science Foundation under grant no. BCS-0527471.

References

Batima, Punsalmaa. 2006. Climate Change Vulnerability and Adaptation in the Livestock Sector of Mongolia. Institute of Meteorology and Hydrology, Ulaanbaatar, Mongolia. Submitted to Assessments of Impacts and Adaptations to Climate Change (AIACC), Project No. AS 06.

Batima, Punsalmaa, Luvsan Natsagdorj, and Nyamsurengyn Batnasan. 2008. Vulnerability of Mongolia’s pastoralists to climate extreme and changes. In Climate Change and Vulnerability, edited by Neil Leary et al., pp. 67-87. Earthscan. London, UK.

Milner-Gulland, E.J. et al. 2006. A multi-agent system model of pastoralist behaviour in Kazakhstan. Ecological Complexity 3:23-36.

Retzer, V. and C. Reudenbach. 2005. Modelling the carrying capacity and coexistence of pika and livestock in the mountain steppe of the South Gobi, Mongolia. Ecological Modelling 189:89-104.

Robinson, Sarah. 2000. Pastoralism and Land Degradation in Kazakhstan. Unpublished Ph.D. dissertation, Department of Biological Sciences, University of Warwick, Coventry, UK.