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Escaping the Tragedy of the Commons

In Cape Town, Day Zero never came.

By Emily J. Siff

In January 2018, Cape Town, a city of 3.7 million people was just 90 days away from experiencing one of the largest urban water crises in modern history (Burls et al., 2019; Wolski, 2018). Ultimately, this crisis would culminate into Day Zero, the day that all taps would run dry.

At first glance, Cape Town’s water crisis seems like a classic Resource Depletion Dilemma. First described by Hardin (1968), this dilemma has a global dimension. Eventually, many of the resources we depend on will run out. Hardin argued that, when there is unchecked access to a shared but finite resource, individuals will put their self-interest ahead of the common good and thus create a ‘tragedy of the commons.’ With no reason to curb their consumption, everyone continues to consume, prioritizing self-interest over the common good. Collectively, these individual decisions culminate into a catastrophic commons loss: the resource is gone.

Elinor Ostrom (2012), a Nobel Laureate in Economics, sought to find ways out of Hardin’s dystopia. Ostrom showed that, in small communities, vital resources can be managed without depletion or tragedy. Local and regional common-pool resources allow for greater coordination through trust and communication than large-scale ones. Cape Town, however, is not a small community: it is a rapidly growing urban center. Ostrom conceded that her work may not generalize to large-scale dilemmas, particularly when the population is already on the brink of resource depletion (Ostrom et al., 1999).

Astonishingly, Cape Town avoided catastrophe: Day Zero never came. For many residents, water scarcity remains a major concern, with economic disparities aggravating inequities in water access (Alexander, 2019; Browdie, 2019). Nonetheless, residents of Cape Town managed to avoid a full-scale shutdown. Cape Town’s escape from tragedy is relevant to the world.

In a National Geographic short film, Cape Town resident Ray De Vries notes that:

“The rest of the world will look to Cape Town for what we did wrong, are doing wrong. And what we did right and are doing right. And that will be the blueprint going forward for eternity.”

In this essay, we look to Cape Town as a blueprint for what can be done right.

Global Water Crises

Worldwide, four billion people face severe water scarcity (see Sengupta & Cai, 2019). With climate change and population demands for resources on the rise, water security issues have been discussed at high policy levels (Pahl-Wostl, 2015). Long-term water crisis issues are driven by not only the small amount of drinkable freshwater in the world (less than 2% of the world’s water) and the inefficient use of that water (e.g. trillions of liters accidentally lost every year) but also by the circulation rate of renewable freshwater resources (RFWR) (Oki & Kanae, 2006). Although freshwater resources might eventually replenish themselves, this process can take thousands of years.

We would all like to believe that, on a national and international scale, we will address water scarcity long before we approach a tragedy of the commons. Nonetheless, hope is an unreliable guide for a planet in distress. Let us look to Cape Town for inspiration.

The Tragedy of the Commons

Game Theory, a branch of applied mathematics, offers a perspective on behavioral dilemmas. In many dilemmas (‘games’), agents (‘players’) can either defect or cooperate. Each player may hold beliefs about the strategy chosen by other players. Accordingly, outcomes (‘payoffs’) depend not only on the player’s own choices but also on the choices of others (for an introduction, see Poundstone, 1992).

In a Resource Depletion Dilemma, to defect is to take from the resource as much as one desires for personal consumption or profit. To cooperate is to show restraint, keeping the community in mind. Regardless of whether others defect or cooperate, a defector can gain more payoffs by defecting. However, when all defects, everyone is worse off than if they all cooperate (Dawes, 1980). This ominous outcome is Hardin’s tragedy of the commons.

E. Siff
The resource depletion dilemma as a prisoner's dilemma
Source: E. Siff

When viewed as a Resource Depletion Dilemma, Cape Town’s water crisis has the same mathematical structure as the well-known Prisoner’s Dilemma (Figure 1). In a Prisoner’s Dilemma (PD), defection is the best strategy regardless of what others choose to do. Hence, a PD approach entails a tragedy of the commons: everyone defects (takes water indiscriminately) and the collective outcome is the exhaustion of the resource (no water).

Given Cape Town’s size and the imminence of water depletion, the dilemma should have been a classic tragedy of the commons scenario. Yet, Cape Town’s response defies the game-theoretic conclusion of defection as a dominant strategy. Not everyone defected and, consequently, complete resource depletion did not occur. What happened?

We argue that Cape Town’s introduction of the concept of ‘Day Zero’ changed the game.

The Creation of Day Zero

Cape Town’s water crisis and Day Zero have often been conflated. However, they are not the same: the water catastrophe this city faced is a reality while Day Zero is a concept – a psychological benchmark – that frames behavior.

The concept of Day Zero was introduced by Cape Town officials. To keep the main source of freshwater, the Theewaterskloof Dam, from drying up, Day Zero was defined as the day that all taps would be shut off, sanctioned public collection points throughout the city would instead be used, and stricter water rations would be enforced (see here for overview; see Ziervogel, 2019, for a comprehensive summary).

The prospect of Day Zero placed an additional cost on the defection. While continuing to serve self-interest, defection would yield a high payoff only if many others cooperated. If most or all defected, any benefit would be obliterated: no one would have running water in their homes. In other words, if defection was mutual or widespread, defection would no longer be the individually rational strategy. Cape Town’s 2018 mayor, Patricia De Lille, noted that there would no longer be a classic Resource Depletion Dilemma when she said, “The abuse of water means that we will all suffer” (Walton, 2018).

If the introduction of Day Zero made the Cape Town water crisis no longer a PD-like Resource Depletion Dilemma (in which defection is the only rational response), what is it?

The Chicken Game

 E. Siff
The 2 person chicken game
Source: E. Siff

Day Zero redefined the game. With collective defection now being the worst situation, the Resource Depletion Dilemma has morphed into a Chicken Game (Rapoport & Chammah, 1965). Figure 2 shows its payoff structure for the two-person case. If both players cooperate, they each earn 20 points. However, if one player defects, this player receives a higher payoff (i.e. more water; 40 points) while, to compensate for that player’s water use, the cooperator must use even less water (i.e. receive a lower payoff; 10 points). Most significantly, if both players defect, they both receive nothing (no water; 0 points). For Cape Town, this meant that if everyone defected and used water indiscriminately, Day Zero would arrive: everyone’s water supply would we have gone (0 points).

The Chicken Game captures the Day Zero dilemma. Collective defection is the worst scenario. Unlike in the classic resource dilemma, there is now an incentive to cooperate. Even though collective cooperation yields less (20 points) than unilateral defection (40 points), the fear of receiving absolutely nothing (0 points) can motivate enough people to reduce their water use (cooperate). These cooperative individuals (the majority) protect the collective from tragedy (20) while allowing a few to reap the extra benefits of defection (40).

Facing the specter of Day Zero, Cape Town residents seem to have recognized the social dilemma of ‘If I take as much water as possible, but everyone else does as well, Day Zero will simply come sooner’ (the final payoff of 0). It is thus possible that the residents of Cape Town did not choose cooperation out of moral righteousness but, instead, out as a matter of rational calculation. Arguably, conspicuous conservation can build trust and inspire others to do likewise. Perhaps there is even a tipping point at which the expectation of others cooperating can further incentivize individuals to choose cooperation. Still, the high payoff available to a minority of defectors remains a temptation, making a broad consensus of cooperation a fragile achievement.

Giving the Chicken Free Range: Global Implications

Cape Town’s dilemma is striking in that, when facing one of the largest urban water crises in modern history, this city of 3.7 million people managed to avoid catastrophe. At the outset, Cape Town’s water crisis was, in fact, a classic Resource Depletion Dilemma. With no incentive to cooperate, residents were approaching a tragedy of the commons. However, by creating the concept of Day Zero, city officials turned the water crisis into a Chicken Game, giving residents an incentive to cooperate out of rational self-interest.

By appealing to individuals’ self-interest, Cape Town’s solution provides a paradigm for the successful management of resource shortages - at least for cases where the resource is replenishable. In reframing the dilemma in a way that made the catastrophic nature of collective defection salient at both the individual and the community level, residents no longer regarded defection as the strategy that was most individually beneficial, regardless of what others do. Within the structure of Day Zero, defection was no longer the dominating strategy.

Cape Town’s approach to resource management can work if there is simultaneously (a) enough time left for individuals to recognize the benefits of their cooperation and (b) an imminent point of collapse (i.e. depletion is not so far in the future that individuals will not see and care about the consequences). As global population growth continues to outpace the supply of resources, finding innovative ways to avoid catastrophic depletions will become an increasingly pressing concern.

Both Hardin and Ostrom doubted that technical solutions could solve the Resource Depletion Dilemma. Social and psychological perspectives have to come into play. A reframing of the Resource Depletion Dilemma as a Chicken Game achieves this objective. The Chicken Game’s dilemma appeals to human values by showing that collective defection does not need to be the most appealing choice. In the face of catastrophe, Cape Town has revealed a decision-based blueprint that might help cities and perhaps societies escape future tragedies.

This essay was written by Emily J. Siff in consultation with Joachim I. Krueger. A student in Brown University’s Concurrent Degree Program, Siff is working toward undergraduate degrees in Cognitive Neuroscience and Literary Arts and a master’s degree in Cognitive Science. Siff is invested in applying research findings to disciplines beyond the sciences.


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