The Tragedy of the Commons part 4: Discussion and Conclusions

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Students will be able to meaningfully reflect on the simulation and data analysis portions of the lesson sequence by participating in a class discussion.

Big Idea

In this final segment of the Tragedy of the Commons lesson sequence, a whole class discussion is held to consider the lessons learned during the investigation into the underlying problems that make environmental and economic regulation necessary.


This lesson is built around a discussion about the results of the debrief of the first two lessons in this sequence Part 1 (unregulated fishing) and Part 2 (regulated fishing).  In my experience, the quality of a class discussion depends on two factors:

  1. the students’ willingness to share their thoughts and opinions
  2. the teacher’s skill in facilitating the discussion

Many different strategies and protocols for class discussions exist and you are encouraged to modify this to fit your class.  The biggest problem I encounter in discussions is that a few students tend to take up most of the “airtime” while the majority keep silent.  I will share here the strategy I employ for this class along with a breakdown of some of the possible answers to the group debrief questions from the previous lesson and suggestions for moving the discussion into deeper waters should the opportunity arise.


Connection to Standard:

In this lesson, students will participate in a discussion where they must offer evidence to support any claims they make.  They must draw this evidence from graphs and charts of numerical data, an informational text of sorts.  Finally, they must make a concluding statement summarizing the insights and real-world connections invoked in the lesson sequence.  



Warm Up

15 minutes

I begin class by asking students to take out their individual work and group work from the previous day.  I then explain the protocol for the discussion:

  1. all groups are required to participate in the discussion and will receive a “participation” grade for the day

  2. groups with more than one member that participate will receive a higher participation grade

  3. groups that participate more frequently will receive a higher grade

I like that these criteria make the group collectively responsible for their grade and accountable to each other. If no one in the group participates, the group as a whole will receive a failing grade.  If only one member of the group participates, regardless of how often, the group can’t receive any grade higher than a C.  


To keep track of participation, I begin by making a map of the class with the group tables labeled by group name.  Since there are four students at each table, as a student from a particular group participates, I make a tally mark in the position of that student in their group.  In this way, I can tally both how often the group participates, which members are participating and how often.  To determine "average" participation, I add up all tally marks and divide by the number of groups, rounding down.  I then use this rubric to determine their participation grades.


After explaining the protocol for the discussion, I give each group 10 minutes to discuss their group debrief together so they are prepared to participate in the discussion.

the Discussion

40 minutes

During the discussion we approach each question from the group debrief worksheet separately.  Students are encouraged to use their graphs and answers to the individual debrief questions to add to the discussion when appropriate.  

As questions are asked and students volunteer to answer them, I try and be equitable and call on groups that haven’t participated before calling on groups that have frequently participated.  Still, if someone has something to add to the discussion, they are eventually given the opportunity to do so regardless of how much they’ve participated previously.  

One of the challenges in a discussion is to have the students talking with each other rather than just speaking to the teacher.  As you can see in the class map, I'm at the "North Pole" at the front of the room, the traditional center of student attention.  To ensure that the discussion is more authentically a dialogue between students, I try and move throughout the room as the discussion progresses, reminding students to address their comments to other groups if they have something to add (whether that be agreement or disagreement). 

I’ve included the group questions below with a bit of an idea of what I’m hoping students bring up in the discussion.  If they seem to be missing one of the points, I try and ask leading questions to elicit the desired response and push students to consider the issue a bit more deeply.

Discussion Questions and Teacher Guide

1. How did the results of your simulation differ between unregulated (day 1) and regulated (day 2) fishing?  Give at least two examples of data in your explanation.

In this question, I’m looking for students to mention that their populations were much more healthy and stable when they were regulated compared to the first day when they only competed rather than participated with the members of their group.  Since this is a fairly basic point, I ask multiple groups to share specific data from their simulations to support their claims.   


2. List the rules that your group enacted.  For each rule, answer the following questions:

o   When was this law enacted (at the beginning, or during a later round in response to a specific problem)?

o   Why was this law enacted?  What results did you expect to come from enacting the law?

o   Did the law have the intended effect?  Explain why or why not using specific data.

In this question, I’m looking for students to explain both the reasons why a law was enacted (i.e., was it foresight or in response to something that had occurred?) and whether it had the intended effects.  I ask that groups support their claims using specific data.  I try get at least 3 groups to share laws they passed so that everyone gets to hear the variety of strategies students took to conserve their fisheries.


3. Compare and contrast your data with another fishing region to answer the following:

o   Were they more or less successful environmentally? Support with data!

o   Were they more or less successful economically? Support with data!

o   What accounts for these differences?  Did they have different laws or different strategies? 

In this question, I’m looking for groups to share not only the specific differences between their results and those of another group, but also to have enough groups participate that reasons or explanations for thoss differences become apparent.  During this question, I also ask if there are real world parallels to this phenomena, (i.e., do different regions manage resources differently?  and if so, how can this be good and/or bad?)


4. What was more important to the economic health of your fishing region: population size or species diversity?  Explain your answer using specific data from your simulations.

Again, on this question, I’m looking for specific data to support their conclusions, but I’m also hoping they understand that both a healthy population and diversity of species is important for the long-term economic and environmental health of their fishery.  Hopefully students mention that even with a very large population of low value fish, it would be hard to be as economically successful as a similarly sized population with greater diversity.  If someone brings up the point that a large population of high value fish would be an economically better option than a large diverse population, I challenge students by asking them why low diversity might be bad for an ecosystem, regardless of the economic values of fish.  Hopefully they offer that low species diversity might disrupt the food chain that the high value fish ultimately rely on.  Additional answers may include an understanding that a low-diversity ecosystem may be less resilient than an ecosystem of greater diversity (e.g., a large population of one type of fish may be susceptible to an epidemic, thereby wiping out the fishery).

5. Consider where fish fall on the “continuum of renewability”:

o   Under what circumstances could they be considered a renewable resource?

o   Under what circumstances could they be considered a non-renewable resource?         

o   Regarding your simulation, how did their renewability differ before and after regulation?

In this question, I’m hoping students use the rules of reproduction we used in the simulation to explain that the “fish” are a renewable resource as long as their populations are kept at reasonable numbers.  Conversely, I hope they mention that when the population of any species falls too low, it either can never recover (e.g., if it was down to just 1) or will recover very slowly (e.g., it got down to just two members).  I ask students to supplement their responses with specific data from their simulations and ask for groups to explain the strategies they used to ensure their populations were harvested sustainably.

6. What were the limitations of the model? (i.e., in what ways did our simulation differ from conditions in a real life fishery or economy?)

This question is fairly wide open, and I’m hoping students use this as an opportunity to both discuss what was good and bad about the model we used.  Answers will, of course, vary, but I’m hoping students bring up considerations such as:

    • Fish populations are much larger than the numbers we are using
    • Two fish are capable of producing more than one offspring
    • Real ecosystems are affected by many more factors and operate according to much more complex rules
    • Prices rise and fall according to supply, such that the value of rarer species would increase over time


Really for all of these questions, students can be pressed to discuss the issue further if you solicit real world examples of the phenomena that arose throughout the simulation.

Wrap Up

10 minutes

At the end of the period, I finish the lesson by asking students one final question:

To study environmental science, can we truly understand the subject if we limit ourselves to studying purely natural systems such as patterns of population growth?

The answer I hope some students will arrive at and share is that to truly understand the issues and address the problems that concern environmental scientists, we must also understand human behavior and our ability to have a positive or negative impact on said natural systems.