1 / 34

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 .

niveditha
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related