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Collapse of Easter Island Understanding a n agricultural society ’s collapse

Collapse of Easter Island Understanding a n agricultural society ’s collapse. By Burak Türkgülü 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium April 25 , 2008. Focus of the Research .

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Collapse of Easter Island Understanding a n agricultural society ’s collapse

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  1. Collapse of Easter IslandUnderstandingan agricultural society’s collapse By Burak Türkgülü 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium April 25, 2008

  2. Focus of the Research • Understanding the ecological collapse of Easter Island as an agricultural society considering its dynamic implications. • Collapse: • drastic decrease in society’s “human population size and/or political/economic/ social capacity over a considerable area over an extended time” (Diamond, 2005) 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  3. Easter Island • A Polynesian island in the Pacific off the coast of mainland Chile. From Wikipedia 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  4. Why Study an Island in Pacific? • Anthropological Argument: Offers laboratory environments to study humans’ interaction with their environment (Kirch, 1997). • Ecological Argument:Offers the opportunity to understand controls on ecosystem structure and function in relatively simple, well-defined ecosystems (Kirch, 1997 from Vitousek, 1995). • Implications for today: • Earth as an isolated island in space. • Environmental problems faced today include the same problems faced by these societies (Diamond, 2005). • Though generalizability is not guaranteed (Kirch, 1997). 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  5. History – Reference Behavior Diamond’s (2005) implied behavior From Croix and Dottori (2008) [originally from Bahn and Frenley (1992)] 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  6. Prior Modeling Work • Brander and Taylor (1998): (1) • Anderies (2000): (2) From Anderies (2000) 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  7. Prior Modeling Work (cont’d) • Brander and Taylor (1998) discuss the slow growth rate of the palm on Easter Island and conclude: • “an island with a slow-growing resource base will exhibit overshooting and collapse” (p.130) • Adaptive institutional change could not happen due to gradual decrease in the carrying capacity. • Anderies (2000) • Existance of ingredients for institutional change does not translate into adaptive institutional change. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  8. Prior Modeling Work (cont’d) • Reuveny and Decker (2000) evaluate exogeneous technological change in resource carrying capacity, intrinsic growth rate, harvesting productivity and fertility. • Generates large fluctuations, no monotonic increase case. • Erickson and Gowdy (2000): • Discuss that the manufactures affect fertility with a delay. Thus, the collapse occurs later. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  9. Prior Modeling Work (cont’d) • Dalton et al. (2005) evaluate the effects of endogenous resource-depleting and resource-conserving technological changes. • If technological change is more resource conserving, monotonic increase occurs. • But they discuss that agriculture is a resource conserving technological change ! • D’Alessandro (2007): • Differentiates between forest as a renewable resource and land as an inexhaustable resource! Also, land is fixed all the time! Similar results to earlier research. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  10. What did prior modeling told me? • Most of the time incentive structures are picked according to the behavior wanted by the researcher. • Anderies (2000): “more complex neo-classical models of human behavior do not necessarily produce a richer characterization of behavior in dynamic context than do simple common sense considerations” (p.409). 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  11. My Approach • System Dynamics Modeling of the Easter Island Ecology • Integration of • Population • Forest • Agriculture on a finite island. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  12. Population 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  13. Land Flow 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  14. Natural Processes • Forest Regeneration (FR): • Logistic Growth: FR=rS(1-S/K) • Arable to Logged (AtL) • Material Delay: AtL=CultivatedLand/T1 • Land Replenishment (LR) • Material Delay: LR=ErodedLand/T2 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  15. Erosion 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  16. Extractive Activities • Based on formulation by Brander and Taylor (1998): Extraction=(EPN*Fprod(RS))*L Increasing Returns to Scale 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  17. Productive Activities P=(Fprod1(LA)*PA*AU)*L • Two different and perfectly substitutable food resources • Agricultural food • Hunted/gathered food 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  18. Land Fertility • Average fertility of each unit of arable land • increases with effort • decreases with new arable land 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  19. Labor Allocation 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  20. Normalcy • Nutirition need depends on food normalcy, not self sufficiency amount of food. • Shelter need depends on shelter normalcy, not the orginally desired normal. • Both normalcy variables are based on floating goals → As people consume more or less from any of the goods, they get used to their new consumption levels with a time delay. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  21. Hunter-Gatherer Society • Base-Run • Sensitivity: Forest Regeneration fraction (0.01-0.5) 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  22. Agricultural Society – Base Run 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  23. Agricultural Society – Base Run 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  24. Agricultural Society – Base Run 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  25. No Erosion Scenarios • Erosion from land use and deforestation is 0 • Erosion from land use is 0 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  26. Sensitivity Analysis – Land Prod • normal land development productivity RANDOM_ UNIFORM(5,45); originally: 15 • (b) normal log prod=RANDOM_ UNIFORM(0.4,4); originally: 1; • (c) forest clearer prod normal RANDOM_ UNIFORM(2,15); originally: 5 (b) (a) (c) 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  27. Sensitivity Analysis – Food Product productivity of food per hectare per decade =RANDOM_UNIFORM(0.5,6); originally:2 normal productivity of hunter/gatherer =RANDOM_UNIFORM (1,10); originally:3 cultivatable land per farmer =RANDOM_UNIFORM=(0.5,4); originally:2 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  28. Sensitivity Analysis – Forest Regeneration • Forest Regeneration Fraction • Random_Normal (0.01,0.5) originally 0.04 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  29. Sensitivity Analysis – Land Replenishment • Land Replenishment Time • Random_Normal(5,45) originally 15 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  30. Major Findings – Easter Island • The main reason of the collapse is erosion caused by extensive deforestation and intensive agricultural activity by the short sighted humans. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  31. Major Findings – Modeling • Page (2005) indicates while criticising Diamond’s (2005) suggestion to replant forest: “replanting does not succeed if the topsoil has blown out to sea” but not many consider it systematically. • Modeling of agricultural societies require the disaggregation of the agricultural activities. • The forest regeneration rate is not relevant in the outcome – Slash-and-burn agriculture: • Through human activities forest coverage can easily be transformed into arable land. • Arable land gets eroded with usage and deforestation. • Most of the land ends up being useless on which forest cannot grow even if it can intrinsically. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  32. Land Flow 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  33. Future Work • Simplify the model, identify the essential assumptions which generates the findings. • Make it easier to manage and communicate. • Explore implications based on choice. • Work with utility functions for • Allocation of labor • Giving birth • Investigate the effects of political stress on the findings. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

  34. References • Anderies J. M. (2000) On Modeling Human Behavior and Institutions in Simple Ecological Economic Systems, Ecological Economics, 35, pp. 393-412. • Bahn, P. and Flenley J. R. (1992) Easter Island, Earth Island. London: Thames and Hudson. • Brander J. A. And M. S. Taylor (1998) The Simple Economics of Easter Island: A Ricardo-Malthus Model of Renewable Resource Use, The American Economic Review, 88(1). pp. 119-138. • Dalton T. R., R. M. Coats, M.R. Asrabadi (2005) Renewable Resources, Property-Rights Regimes and Endogenous Growth, Ecological Economics 52, 31-41. • D’Alessandro S. (2007) Non-linear Dynamics of Population and Natural Resources: The Emergence of Different Patterns of Development, Ecological Economics, 62, 473-481. • de laCroix and Dottori (2008) Easter Island Collapse: a Tale of Population Race, Journal of Economic Growth, 13, 27-55 • Diamond (2005) Collapse: How societies choose to fail or succeed, Penguin Books. • Erickson J. D. And J. M. Gowdy (2000) Resource Use, Institutions, and Sustainability: A Tale of Two Pacific Island Cultures, Land Economics, 76 (3), 345-354. • Kirch P. V. (1997) Microcosmic Histories: Island Perspectives on “Global” Change, American Anthropologist, 99(1), 30-42. • Page, S. E. (2005) Are We Collapsing? A Review of Jared Diamond’s Colllapse: How Societies Choose to Fail or Succeed, Journal of Economic Literature, 43, 1049-1062 • Reuveny and Decker (2000) Easter Island: Historical Anecdote or Warning for the Future?, Ecological Economics, 35, 271-287. • Vitousek (1995) The Hawaiian Islands as a Model System for Ecosystem Studies. Pacific Science 49, 2-16. 16th MIT – UAlbany – WPI System Dynamics Ph.D. Colloquium 2008

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