Agent-based modeling for migration
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Agent-based modeling for migration. Julia M. Blocher Sciences Po, 17 March 2014. What is agent-based modeling (ABM)?. A computational method to model and simulate complex systems in the real world Modeling agents (individual entities) that interact with each other within an environment - PowerPoint PPT Presentation
Transcript of Agent-based modeling for migration
Agent-based modeling
Agent-based modeling for migrationJulia M. BlocherSciences Po, 17 March 2014What is agent-based modeling (ABM)?A computational method to model and simulate complex systems in the real worldModeling agents (individual entities) that interact with each other within an environmentExplore the dynamics that arise from the characteristics and behaviors of agents making up biological, social, and other complex systems When do you use ABM?When it is unrealistic, impossible, or unethical to do real-life experimentsTo capture phenomena that can be difficult to predict or are counterintuitiveWhen its important to include individuals - describe activities rather than structure and processesWhen you want to understand behavior not averagesWhat does ABM do well?Captures emergent phenomenonNon-linear behavior ThresholdsIf-then rulesNonlinear coupling (fluctuations, perturbations)Provides a natural description of a complex systemIs flexible and relatively easy to programStakeholder engagement is non-negotiableExamples when this type of simulation would be useful? Flow simulations: e.g. crowds at concerts, panicking populations, transport and traffic implications for urban planning and evacuation policiesMarket simulations: e.g. neural networks for stock markets and trader behaviorOrganizational behavior: e.g. risk-taking in banksDiffusion behavior: e.g. social contagion, transmissible disease infectionPractical example
Source: Wilensky, U. (2003). NetLogo Ethnocentrism model. http://ccl.northwestern.edu/netlogo/models/Ethnocentrism. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
What do you need for ABM?One or more agents: Self-contained Autonomous and self-directedState variablesCommunicative (social ability)Have memory, learning, strategies (adaption and path dependence)HeterogeneousA representation of the environmentAgent interactionsBounded rationalityAgent-based modeling for environment and climate change induced migrationWhy use ABM for environment and migration?A quantitative approach that doesnt assume all people respond to climate in the same wayEmphasis on unique context and circumstances in real world phenomenonRecognizes that individual attitudes and perceptions affect migration decision makingUses rules of behavior from real-life situations and people in computer simulation modelConcretely how do you build an ABM?
Ten year ensemble for rate of total migration under non-scaled normal (N-) and sigmoid (S-) rainfall scenarios tested. Error bars for S-EXTRAWET and S-EXTRADRY.
Source: Smith, C.D. (2013) Modeling migration futures: development and testing of the RABMM-T. Sussex: Univ. Sussex, UK.
Agent-based migration model (RABMM-T)
Combining with other research methodsLarge N data E.g. census and household surveys, data miningStatistical distributions and other stylized factsCase studies E.g. Ethnographic studies, interviewsParticipatory methodsRole-playing games and companion modeling (e.g. Barreteau et al. (2001))Geographic data: import topographies and GIS, remote sensing Lab experiments to test computational modelsCombining ABM with other methods
Flow rates in Al Zaatri refugee camp, northern Jordan, Sept. 3 2012. Source: UNOSATPractical applicationsInfluence of climate on political drivers of migration as adaptation in mixed livelihood zones in North-Eastern EthiopiaConceptualizing the model
Drivers of migration. Source: Black, R., S.R. Bennett, S.M. Thomas, J. Beddington. Nature (2011) Vol 478, 27 Oct. 2011Adaptive migration in mixed livelihood zones in N.E. EthiopiaQuestion: What are the mechanisms underlying the processes of influence of environmental change on political drivers of migration the indirect effects of CC on migration decision-making process?
Hypothesis: In past patterns (events and changes), coping migration response increases overall, for most individuals - rate of migration is decreased for participants in local level policy schemes Methodology & specific aimsTreatment of large N data 20 year retrospective study 5-10 expert interviews at multiple levels of governance Questionnaires, reconstruction of migration histories for 100-150 households of migrants and non-migrantsFocus group discussions Participatory methods ABM validated by past patterns to predict migration patterns for future worlds simulated by high-end warming scenarios (2, 4, and 6 degrees C warming)
Haraghe zones, Ethiopia
Livelihoods zones in Ethiopia. Source: FEWSNET (USAID)
Conceptualizing the model
Drivers of migration. Source: Black, R., S.R. Bennett, S.M. Thomas, J. Beddington. Nature (2011) Vol 478, 27 Oct. 2011High vulnerability: need to change situation (stress)Low vulnerability: invest in migrationHigh vulnerability: in-situ copingLow vulnerability: in-situ adaptationIndividual attitudes and perceptionsVulnerability assessment: Need to change v. employing existing strategies
Ten year ensemble for rate of total migration under non-scaled normal (N-) and sigmoid (S-) rainfall scenarios tested. Error bars for S-EXTRAWET and S-EXTRADRY.
Source: Smith, C.D. (2013) Modeling migration futures: development and testing of the RABMM-T.
Agent-based migration model (RABMM-T)
Ten year ensemble rate of total migration under the range of non-demographic scenarios.
Source: Smith, C.D. (2013) Modeling migration futures: development and testing of the RABMM-T.
Agent-based migration model (RABMM-T)
Whats the catch?Trade off between generalizability and goodness of fit with values observed empiricallySurvey data and statistics can leave out the most vulnerable and marginalizedHow do you scale up the processes of a few agents into the interactions among many agents?As complexity increases, the more difficult it is to link the models structure to its behavior (outcomes)Not as transparent as other methods
SourcesBlack, R., S.R. Bennett, S.M. Thomas, J. Beddington. Migration as adaptation. In: Nature (2011) Vol. 478, 27 Oct. 2011Black, R., et al. (2011). The effect of environmental change on human migration. In: Global Environmental Change 21, Supplement 1(0): S3S11.Kniveton, D., C.D. Smith and R. Black (2012). Emerging migration flows in a changing climate in dryland Africa. In: Nature Vol 2, pp. 444-447.Railsback, S.F. and V. Grimm (2012). Agent-Based and Individual-Based Modeling. Princeton: Princeton University Press, Princeton University.Smith, C.D. (2013) Modeling migration futures: development and testing of the RABMM-Tanzania. In: Climate and Development Vol 1 2014 [Accepted Sept 2013].Smith, C.D. (2012) Assessing the Impact of Climate Change upon Migration in Burkina Faso: An Agent-Based Modelling Approach. [DPhil Thesis] University of Sussex.Tacoli, C. (2011). The links between environmental change and migration; a livelihoods approach. London, International Institute for Environment and Development.Wilensky, U. (2003). NetLogo Ethnocentrism model. http://ccl.northwestern.edu/netlogo/models/Ethnocentrism. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
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