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TRANSCRIPT
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Thinking in Systems The basic idea of this activity is to develop a systems model with inputs, outputs, stocks (or “pools”), and flows (or “fluxes”). In the series of videos on phosphorus, Dr. Crews uses a technique common to many scientists: he simplifies a complex system to further understanding it or better communicating it to others. In this activity you will think about how to use a simple model to illustrate a complex system found in your everyday life. In part 1, you will diagram this system in its simplest form, assuming the system is fully functioning. In part 2, you will think about what can cause this system to not work well, adding complexity to your model to use it as a tool to explain the cause of proper/improper functioning.
Thinking in Systems
Systems and Cycles Systems and cycles form an important part of science. A system is the setting in which cycles occur. A cycle can involve changes in state, such as the water cycle: liquid to solid to gas and back again. A cycle can also involve a change in life phase: birth to growth to adulthood to reproduction to death. Cycles can also involve changes in composition, such as carbon cycle:
for example, the change CO2 to CH2O +O2 (organic matter) to decomposition, where carbon is broken down and released as CO2 or CH4. Systems include both a cycle and all the factors that may influence the cycle. In order to study and better
understand them, systems can be represented by simple models.
TERMS adapted from Thinking in Systems by Donella Meadows, p. 177-‐178
• System: “A set of elements or parts that is coherently organized and inter-‐connected in a pattern or structure that produces a characteristic set of behaviors.” Everyday examples: The U.S. interstate highway system, your Facebook news feed, a human digestive system, the water cycle
• Stock: “an accumulation of material or information that has built up in a system over time.” Everyday examples: the number of cars in a parking garage, a ream of paper, a plate of food, nutrients in the soil (a.k.a. pool)
• Flow: “material or information that enters or leaves a stock over a period of time.” Everyday examples: the rate of cars entering a highway from an on-‐ramp, the number of new posts made by friends on your Facebook newsfeed every hour, food entering or leaving your body (a.k.a. flux)
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Thinking in Systems
Part 1: Diagramming a System Instructions: 1. Think of a system in your everyday life that sometimes works well and sometimes doesn’t work well or at all. 2. Take a picture of or draw something that represents that system. Put that image in a power point slide, like Dr. Crews did. Alternatively, images can be drawn in a science journal. 3. Identify the basic function of the system and basic flows in and out of the system. Flows might be money, energy, parts of a product, or something else. Add these flows to your image as arrows. If you have numbers for each aspect, be sure to include these numbers clearly. 4. Identify places in the process where your moving component (energy, money, etc.) might be lost or changed into something new. 5. What processes happen within the system that might affect its functioning? What would slow down or speed up the process? Is there anything that would shut the system down altogether? 6. Think about ways that people, even you, could alter or improve this system to get a desirable outcome. Share your ideas with a friend or in a journal.
Example: Some cities offer a bike-‐share system to help residents and visitors get around without using cars or buses. In such systems, bikes are the item that moves throughout the system (like phosphorus through the air, water, and soil). However, unlike phosphorus, the bikes (hopefully) do not change form. Bikes move from one area to another within the bike system, and under special circumstances (purchase or loss) bikes may join or leave the system. altogether.
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Thinking in Systems
Part 2: Manipulating a System The idea of this activity is to continue development of the system model created in Thinking in Systems Part 1 with inputs, outputs, stocks (or “pools”), and flows (or “fluxes”). In this part, you will begin to manipulate your system in ways comparable to how traditional farmers discovered techniques to augment the cycle of phosphorus. In this exercise, you will be asked to consider ways to augment your system to allow for higher productivity or operability within your system while operating within limits to growth that you identify. The example system used in Part 1 was a city bike share system, and this example is extended below.
Example: Pressures for growth:
• Increasing number of users (people) using the bike share system
• Many riders take similar routes, making bikes more scarce at some docking stations
• Increasing theft or disrepair of bicycles within system
Limits to growth: • Cost of introducing new bicycles and
docking stations within system • Availability of resources to manufacture
new bikes and docking stations • Available real estate for docking station
expansion
PART 2: INSTRUCTIONS
1. Think about all the dimensions of your system from start to finish. Write down all the pressures for growth on the system, as well as all the limits to growth within that system.
2. Identify strategies that respond to each of the pressures for growth you listed and that are sensitive to your noted limits to growth. Think about the strategies used in traditional agriculture that Tim Crews describes as analogies to strategies that you may choose to implement in your system.
3. Update your system drawing to describe how strategies affect the performance of the system. Use additional visuals as needed.
Cook, Lindsey. 2013 “How Capital Bikeshare has Grown.” The Washington Post: Aug 2, 2013.
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INSTRUCTIONS-‐Continued
4. When you have finished, graph a potential change within your system based on one of the pressures or limits you described. In the bike system example, you might graph predicted growth of bike numbers if the population grows by 10% over the next 15 years. What other factors might play a role and keep your line from being a simple increase or decrease? For our bike share program, an increase in population might also lead to an increase in bike theft.
If you were graphing the current phosphorus cycle, do you think that the pool of phosphorus in the soil would be growing, shrinking, or neither? What are the factors influencing the phosphorus system?
5. How is your system similar to a natural system like the phosphorus cycle? How is it different? Share your ideas with a friend or record them in your science journal.
Part 3: Transformational Changes in a System
Recall the simple system you developed in Part 1 and added to in Part 2 of “Thinking in Systems.” In this exercise, you will be asked to consider how large changes may alter your system -‐-‐ in either positive or negative ways. The example system used in Parts 1 and 2 was a city bike share system. Instructions: 1. Think about conditions that would lead to a transformation of your system—what could cause a sudden and enormous change in the quantity of inputs/outputs or the speed of processes within the system? Make a list of possible causes of transformational change as well as possible positive and negative consequences of that change.
Thinking in Systems
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Part 3-‐ continued
2. Select one of the transformational changes you identified in Part 2, and alter your system map to characterize the changes to your system. 3. Evaluate your transformed system to determine whether it still behaves in a manner that meets the original goals of your system. Also, evaluate the extent to which transformations in the system carry consequences that might positively/negatively affect other systems outside of your own. 4. Compare and contrast your system to a natural system such as the phosphorus cycle.
Thinking in Systems
Examples: • New city policy limits vehicle traffic, pushing a significantly larger share of the
population towards riding bikes. Consequences:
o For a period, demand overwhelms supply of shared bicycles o More diverse routes are added to the system which enable easier
rebalancing between redocking systems • Bikes are retrofitted with small motors, which increase the speed of trips and
enable longer routes Consequences:
o A entire new set of individuals begin to bike, leading to a dramatic increase in demand for bikes
o Longer routes lead to a much larger demand for distribution of docking stations
o Shared motorized bicycles begin to replace cars on roadways
Meadows, Donella H. 2008. Thinking in Systems: A Primer. Chelsea Green Publishing, Vermont.
Further Reading