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A simple population model Harald Rybka Jason Wong Jorge Rivas RISE Research Internship of Science and Engineering Intern Johannes Gutenberg University Mainz and University of Maryland AOSC 2 September 2010 OUTLINE 1 Introduction to VENSIM 2 Limits to Growth World3 model 3 Basic New Model Structure 4 Improved Basic Model results global 5 Improvements and Problems 9 2 2010 2 INTRODUCTION TO VENSIM VENSIM simulation software used for analyzing and simulating dynamic feedback modeling identifying leverage points and causal loops similar to STELLA Results use SyntheSim mode different effects can be simulated with sensitivity simulations 9 2 2010 3 INTRODUCTION TO VENSIM AN EXAMPLE ow stock ow sink source SyntheSim constant auxiliary variable average life me 6 years average life me 20 years 9 2 2010 sensi vity run average life me 5 25 years 4 LIMITS TO GROWTH WORLD3 MODEL created by Donella Meadows J rgen Randers Dennis Meadows authors of the book Limits to Growth 1972 2004 computer simulation of interactions between the population system the industrial system the food system agriculture and food production the non renewable resources system and the pollution system ten different scenarios present results from 1900 till 2100 results varies from stabilization to collapse in the future 9 2 2010 depending on several variables e g nonrenewable resources 5 WORLD3 MODEL STANDARD RUN agrees with obs 1970 2000 Turner 09 popula on food industrial output persistent pollu on nonrenewable resources business as usual population collapses because of decrease of food and health services increase costs of nonrenewable resources 9 2 2010 6 WORLD3 MODEL SCENARIO 2 doubled initial nonrenewable resources popula on food industrial output persistent pollu on nonrenewable resources nevertheless population collapses about 20 years later 9 2 2010 7 WORLD3 MODEL OPTIMISTIC STABILIZED SCENARIO Compared to Standard Run doubled nonrenewable resources improved pollution control increase of land yield



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