This classroom simulation models the “Tragedy of the Commons” using colored marshmallows (or other small items) as fish. Students compete to maximize their catch but quickly discover that overfishing leads to resource collapse, while cooperation and restraint allow the population to replenish.

1. Divide students into groups of 3–4 and give each group a plate with a set number of colored marshmallows (fish).
2. Explain the point system (each color fish has a different value).
3. Students construct simple “nets” using tape, straws, and a paper towel boat.
4. In timed rounds (about 30 seconds), students “fish” for as many marshmallows as possible.
5. At the end of each round, replenish the fish population: for every two of the same color left, add two more of that color.
6. Continue for several rounds, recording catches and resource levels.
7. Discuss which groups sustained their fish populations and which collapsed.

Happy Fishing (Tragedy of the Commons) Simulation - Teaching AP Science:

📄 Happy Fishing (Tragedy of the Commons) Simulation - Teaching AP Science: https://teachingapscience.com/tragedy-commons-5e/

• Use different food items (goldfish crackers, M&Ms) or reusable beads instead of marshmallows.
• Change reproduction rules to mimic different species’ reproductive strategies.
• Introduce regulations (catch limits) partway through the game and compare outcomes.

• If using food items, ensure students with allergies are protected.
• Do not eat marshmallows or other items that have been handled during the game.
• Clean up thoroughly to avoid attracting pests.

• What happens to shared resources when individuals prioritize personal gain?
• How do rules and regulations change the sustainability of resource use?
• What real-world examples of commons can you identify? (Fisheries, grazing lands, atmosphere, groundwater.)
• How does cooperation affect the long-term availability of resources?