Using the variables below related to forest management, identify which are stocks and which are flows. Then create a diagram including
all the variables and feel free to add any that are not mentioned.
Aging into Sawtimber
Aging into Middle-aged
Using the variables below related to oil recovery, identify which are stocks and which are flows. Then create a diagram including all
the variables, and any additional ones you need.
Undiscovered petroleum resources
Cumulative petroleum consumption *An exercise developed by MIT Professor John Sterman
*These books are great resources for all the fundamentals of systems thinking.
Note on the video lesson:
Due to an effort to keep the lesson short, there are some subtleties that were left out:
The role of interest feedback in the credit card example. There is an important reinforcing feedback loop that increases debt through
Why removals fall in the reduction scenario (time 11:00 in the video). There are two important feedback loops that we don’t explain in
the video. First, there a “fertilization” feedback loop – the more emitted, the more removal – so when emissions go down, so do
removals. Second, there is a “saturation” feedback loop where the sinks – both biomass and oceans – fill up with CO2 and the rate of
There are many opportunities to learn more about stocks and flows. Here are several:
Sterman, J. (2012). Sustaining Sustainability: Creating a Systems Science in a Fragmented Academy and Polarized World. Sustainability
Science: The Emerging Paradigm and the Urban Environment. M. Weinstein and R. E. Turner, Springer: 21-58.
Sterman, J. (2011). “Communicating Climate Change Risks in a Skeptical World.” Climatic Change 108: 811-826.
Sterman, J. D. (2010). “Does formal system dynamics training improve people’s understanding of accumulation?” System Dynamics Review 26(4): 316-334.
Cronin, M., et al. (2009). “Why Don’t Well-Educated Adults Understand Accumulation? A Challenge to Researchers, Educators, and Citizens.” Organizational Behavior and Human Decision Processes 108(1): 116-130.
Sterman, J. D. (2008). “Risk Communication on Climate: Mental Models and Mass Balance.” Science 322: 532-533.