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Mobility – a panacea for pastoralism? An ecological-economic modelling approach.
Gunnar Dressler, Birgit Mueller, Karin Frank
Department of Ecological Modeling
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IntroductionBackground and Motivation
Mobility = Basic principle of nomadic life
Fast & long-distance mobility due to new
technologies
Decline of nomadism &
increased sedentarisationFernandez-Gimenez et al. [2006]
Regions often drylands, resource-scarce
Wide range of transition processes political, climatic, economic, technological
Sustainable resource use is a central topic
IntroductionResearch questions
What are pitfalls and chances of new technologies, i.e. increased mobility?
How does mobility affect long-term conditions of pasture and livestock? Can mobility improve conditions of biomass and livestock?
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MethodsModel characteristics
Multi-Agent simulation model
Structural simplistic, structure based on empirical data
Dynamic feedback between ecological and economic component
Spatial structure: patch network
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Figure 1: Snapshot of patch network and pathway of agents. Each color represents one agent.
Patches (Pastures)
MethodsModel overview: Entities, their relationships and main processes
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Green
Biomass
Reserve
Biomass
Precipitation
Lognormal Distribution
Livestock (Sheep)
Feeding Reproduction
Agents (Pastoralist households)
Patch selection submodel
(Optimization criteria)
grazing
income
rain
fall
growth
movement
decision
fodder
owne
rshi
p
MethodsPatch selection
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Enough biomass on
patch?
Found new best patch?
Destocking necessary?
Agent stays on current patch
No destocking
Agent moves
Needs to destock
Agent stays on current patch
Needs to destock
Agent moves
No destocking
Patch selection submodel
Optimization criterion based on
Sheep value Patch distance Movement costs
yes
no
yes
yes
no no
MethodsMovement costs vs. mobility
Intent of movement costs in the model: low costs ≙ high mobility high costs ≙ low mobility
Movement costs are a proxy to regulate mobility, both distance and frequency.
Movement costs are relative values, not specific prices.
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Figure 2: Use of patches by one agent at low and high costs in one exemplary simulation run.
MethodsSimulations and Hypotheses
Parameter variation:
Number of agents in the system na and
Movement costs cM.
Other parameters fixed (Mueller et al. [2007], Schulze [2011]).
Hypotheses:
Higher density of agents will have a negative impact on biomass and livestock.
Mobility of agents can counteract and enhance livestock and biomass conditions.
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ResultsReserve biomass and livestock averages, time step t=100
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[kg/ha] [# sheep]
Figure 3: Averages of reserve biomass and livestock at time step t = 100, calculated from 500 simulation runs.
ResultsRegulation of movement – resting of pastures
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Low density Medium density High density
Low costs
Medium costs
High costs
Evaluation of combined effects of agent density and movement costs:
System only sparsely populated
No negative effects of mobility.
Mobility too high.
Negative effects on pasture conditions.
Improvement of pasture and livestock conditions with increasing movement costs.
Costs too low.
All biomass reserves are used.
No resting of pastures.
Costs too high.
No movement at all.
No resting of pastures.
Effective regulation of movement.
Resting of pastures possible.
Conclusion
Mobility is not an answer to all problems that pastoralism
faces: Resting of pastures is the crucial mechanism behind.
Pasture resting can be achieved through an appropriate level of mobility.
Exploratory model has proved useful to test the impact of new technologies (increased mobility).
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Discussion and OutlookNext development steps
Dynamic decision criterion that also incorporates future livestock value.
Polarization: Is coexistence of agent groups with different resource sets or strategies possible? Can poor agents save their livelihood?
Access regimes: Traditional access regimes vs. new institutions – How should new institutions be designed to regulate pasture access?
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Acknowledgements & References
We would like to thank Dr. Sten Zeibig who inspired us to do this study.
We acknowledge support of the German Research Foundation (DFG) within the Collaborative Research Centre „Difference and Integration: Interaction between nomadic and settled forms of life in the civilizations of the old world“.
References:
Fernandez-Gimenez, M.E. and S. Le Febre, Mobility in pastoral systems: Dynamic flux or downward trend?, International Journal of Sustainable Development & World Ecology, 13, 342–362, 2006.
Mueller, B., K. Frank and C. Wissel, Relevance of rest periods in non-equilibirum rangeland systems - a modelling analysis, Agricultural Systems, 92, 295–317, 2007.
Schulze, J., Risk Measures and Decision Criteria for the Management of Natural Resources Under Uncertainty - Application to an Ecological-Economic Grazing Model, Master Thesis, Helmholtz Centre for Environmental Research & Ernst-Moritz-Arndt-University of Greifswald, 2011.
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