The Tragedy of the Commons: A Heuristic Model for Understanding the Problem and Evaluating Educational and Regulatory Solutions A Modeling Project by Greg Teves, Alyson Dame and Lyrica Hammann Environmental Systems Modeling Spring 2004
An Overview of Our PresentationOur project is a heuristic model designed to help ENVS 101 students understand the tragedy of the commons and examine two possible solutions. • What is the “tragedy of the commons?” • Costanza’s Poker Game • Education: Pros and Cons • Government Regulation: A Tax. • Alternatives? Put on your cow hats everyone!!
What is the “Tragedy of the Commons”? • ARTICLE: published in 1968 by Garrett Hardin. • CONCEPT: a shared resource in which any given user reaps the full benefit of his/her personal use, while the losses are distributed amongst all users. Result? Tragedy all around.
What is the “Tragedy of the Commons”? • CLASSIC EXAMPLE: cows on shared pasture. • What are other examples of commons? • Air • Water • Scenery
In our model: Each farmer decides whether or not to add a cow based on the marginal gain (1) vs. their share of the marginal productivity loss (1/farmers). Since their gain is always greater than personal loss, the farmers never stop adding cows. Meanwhile, the commons (a grass population that grows according to a logistic growth curve) can only regenerate so fast. It loses grass to death and cow predation. If the farmers keep adding cows, eventually the predation rate overwhelms the regeneration rate, and the commons is terminally depleted.
Costanza’s Poker Game • Robert Costanza characterizes the “tragedy of the commons” as a “collective social trap.” He compares it to an experiment done by Edney and Harper (1978) that uses poker chips to study resource use. • We recreated this game in our model to show the thinking behind a farmer’s decision to add additional cows.
Costanza’s Poker Game • In the poker chip game, players can each take between 1 and 3 chips a turn. Each round, the pot is replenished in proportion to the amount of chips left. If there were 5 players and 15 chips, how many chips would you take? 2? 1? 3? BLAST OFF!
Costanza’s Poker Game • Totally rational players take 3 each, because they know that if everyone else takes 3, there will be no chips left for them in the future. • However, the best long-term solution is for all players to take 1 chip, because the pot will continue to be replenished. • The point? Our short-term incentives do not serve our long-term interests. To make good long-term choices, all players must cooperate.
And, the model: In this model, everyone contributes three chips except for the user, who can choose how many to contribute using a slider. What the user finds is that the best strategy is to take three chips. It is a dog eat dog poker chip world.
Would education help? One solution might be education. If everyone knew the best long-term strategy, would they act accordingly and “take 1 chip”? Probably not. As Costanza writes: “If any one player consumes 3 chips per round, the other players will do individually worse by restricting their consumption to 1 chip per round.” (Costanza, 409).
More Conscious Farmers Get Less: It’s just not fair!!! Farmer 1: 12 Cows Farmer 2: 8 Cows Farmer 3: 4.5 Cows Farmer 4: 2 Cows
Hardin’s Suggestion: Mutual Coercion, Mutually Agreed Upon • A regulation accepted by the majority of those affected and imposed upon all involved. • Examples? • Speed limits • Income tax • Aesthetic standards in a gated community • “shotgun!”
Hardin’s Suggestion: Mutual Coercion, Mutually Agreed Upon • Hardin admits there are drawbacks to strict legislation, but believes: • There is no perfect solution. • Status quo is worse than a regulated situation • He writes: “Who enjoys taxes? We all grumble about them. But we accept compulsory taxes because we recognize that voluntary taxes would favor the conscienceless.” (Hardin, 338)
Footnote: Another dimension of added realism in this version of our model is a degenerating K.
Advantages? • “Conscienceless” farmers must participate • Trust Fund • Market Solution-y (as opposed to hard cap) Disadvantages? • Enforcement Costs • Could be Abused by Big Business
Alternatives? Our model does not exhaust the possible management strategies for the tragedy of the commons. Others include: • Community Norms • Privatization • Hard Cap