Mobility – a panacea for pastoralism? An ecological-economic modelling approach.

Gunnar Dressler, Birgit Mueller, Karin FrankDepartment 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 sedentarisation

Fernandez-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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GreenBiomass

ReserveBiomass

Precipitation

Lognormal Distribution

Livestock (Sheep)

Feeding Reproduction

Agents (Pastoralist households)

Patch selection submodel(Optimization criteria)

grazing

income

rain

fall

growth

movementdecision

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 submodelOptimization 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 populatedNo 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 & ReferencesWe 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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