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Sustainability. Feedback Loops Closed Systems Easter Island’s Ecology Crash The Role of IE in Sustainability. Goals for two days . Draw and analyze basic influence diagrams – positive and negative feedback. Delay. (Day 1)

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Sustainability


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    1. Sustainability Feedback Loops Closed Systems Easter Island’s Ecology Crash The Role of IE in Sustainability

    2. Goals for two days • Draw and analyze basic influence diagrams – positive and negative feedback. Delay. (Day 1) • Understand the story of Easter Island’s ecological crash as a positive feedback loop in a closed system • Understand principle of sustainability • See why IE will help; links to more info; ideas for projects

    3. System Dynamics • Another descriptive model • Gives qualitative predictions and insights • Software tools exist (STELLA) for more quantitative predictions • Industrial Dynamics, by Jay Forrester (the classic reference) • Popular book: The Fifth Discipline by Peter Senge

    4. Influence Diagrams: Core Concepts • Cause and Effect thinking, Influence or Causal Loop Diagrams • Feedback • Positive Feedback • Negative Feedback • Delay in Feedback Loops

    5. Cause and Effect • Draw an arrow from cause to effect • ``Influence’’ or ``affect’’ may be a better term than “cause.” • Examples

    6. Skill at X Practice X Sales of Y Price of Y Number of Offspring Population Size

    7. Influence Diagrams • Place a “+” or a “-” at the arrow to indicate the kind of influence + means: the more of one, the more of the other (or less…less) - means: the more of one, the less of the other (or less…more)

    8. Skill at X Practice X + Sales of Y Price of Y - Number of Offspring Population Size +

    9. Feedback Loops • Any directed cycle is afeedback loop • The arrows must take you back to where you started • Feedback makes systems complicated! • Examples

    10. Skill at X Practice X + Pleasure from X + + Sales of Y Price of Y - Efficiency of Y Production - + Number of Offspring Population Size +

    11. Principle: the most important causal influences are those that are within feedback loops

    12. POSITIVE Even # of - signs Amplifying Reinforcing Growth, but also Decline Unstable NEGATIVE Odd # of - signs Balancing Stabilizing Often good! Stable equilibria Two Kinds of Feedback

    13. Feedback Examples • A pencil falls • Standing on one foot

    14. + Imbalancing Gravitational Force Tilt +

    15. + + Imbalancing Gravitational Force Muscular Correction Tilt - +

    16. + + Imbalancing Gravitational Force Muscular Correction Tilt + Tilt Detection - +

    17. + + Imbalancing Gravitational Force Muscular Correction Tilt + Tilt Detection - +

    18. - Stock Price to Earnings Ratio Stock Price + + Costs Room Temperature A/C Activity - + + + Costs External Heat

    19. Analysis of an argumentorHow to make a mountain out of a molehill

    20. + A’s anger A’s harshness + + B’s harshness B’s anger +

    21. Mountains out of Molehills • Whose fault is it? • “You started it” • Cause, effect, and blame are not clear in complex systems

    22. Delay • Taking a shower • Carrying a cup of coffee • Timing very important • Beer game, supply chains • Classic problem: when short-term influence is of one type, and long-term influence is of the other type

    23. Floods Drought - - Local Food Production - Starvation + - Population Size + Feed Hungry Delay

    24. + Eat Candy Blood Glucose Level + - Hunger Level

    25. + Eat Candy Blood Glucose Level - + + Delay Hunger Level - Insulin Production

    26. Oscillations that increase in amplitude over time area danger signal

    27. Glucose and Insulin • How could nature be so stupid? • How could such an unfit system survive?

    28. Nature isn’t stupid -- We are! • 1st appearance of insulin regulation • 10,000,000-70,000,000 years ago • 1st appearance of refined sugar • 1500 to 2400 years ago

    29. + Eat Complex Carbohydrates Delay Blood Glucose Level - + + Delay Hunger Level - Insulin Production

    30. Eat Complex Carbohydrates + Delay Blood Glucose Level + + - Eat Candy + + Delay + Insulin Production Hunger Level -

    31. Natural & Man-Made Systems • Natural systems have usually evolved so that timings work well • Introduce a new element into a smoothly running system and you are lucky if timings remain good • As change rate of technology  this problem occurs more frequently

    32. LIMITS TO GROWTH + - Growing Action Condition Slowing Action + + Startup grows – Requires organization Wolf-free deer – Over grazes and dies population grows Telcom Industry – Overbuilt capacity

    33. Tragedy of the Commons + + Net Gains for A A’s Activity + Gain per Activity - Total Activity Delay + + Resource Exhaustion + B’s Activity + Net Gains for B - - + + • Examples: • England • Whales • H2O B’s Perceived Gain per Activity

    34. Open Systems and Closed Systems Consider the earth…

    35. What does Little’s Law say about a closed system? • Little’s Law does not apply to systems with no throughput. • I = RT and R = 0 ) I = 0. Thus eventually inventory drops to 0. • I = RT and R ! 0 ) T !1. Thus inventory stays in the system forever.

    36. Easter Island:The Mystery

    37. thanks to Carl Anderson for the beautiful photos The Moral: Positive (unbalancing) feedback loops in a closed system mean disaster

    38. Earth Island Is the Earth suffering from the same destructive patterns as Easter Island?

    39. Frightening Facts • 180 million tons of trash/year in U.S. • 50% of topsoil in U.S. lost this century • 25 billion tons/year worldwide • Everglades extinct? • Loss of species • frogs: 1/3 or more • we save mountains, not lowlands

    40. “Every natural system in the world today is in decline” • Water, aquifers • 20 billion gallon/year deficit in groundwater • Ogalala Aquifer dry in 30-40 years at present extraction rates • Fertility rates • Global Warming: North pole, Alaskan towns • Pesticides: 4.1 billion tons/year, 25 million deaths • Equilibria: ozone, everglades, warming

    41. Understanding Systems Problems • Tragedy of Commons. • Example: whales and the IWC • Example: strip mining the ocean floor, where there is a new species every square meter. • Limits to Growth • Example: Human Population, now over 6,000,000,000 • Transportation Engineering: • Building more highways does not reduce traffic problems. (Why?) It increases oil usage and pollution.