The tragedy of the commons is a class of phenomena that involve a conflict for resources between individual interests and the common good. The term derives originally from a parable published by William Forster Lloyd in his 1833 book on population. It was then popularized and extended by Garrett Hardin in his 1968 Science essay "The Tragedy of the Commons". See also the enclosure of the commons, and its attendant social problems, which may have inspired the content of the parable.
The parable demonstrates how free access and unrestricted demand for a finite resource ultimately dooms the resource through over-exploitation. This occurs because the benefits of exploitation accrue to individuals, each of which is motivated to maximize his or her own use of the resource, while the costs of exploitation are distributed between all those to whom the resource is available (which may be a wider class of individuals than those who are exploiting it).
The paradigm example is the use by individuals of communally owned land for the grazing of animals owned privately by those individuals. As Hardin sees it, the utility to each individual of adding a single animal to his own herd is, more or less, the value of that animal; the cost to the individual is the consumption of the resources of that animal divided by the number of communal owners of the common. That is, the benefit to an individual of "hogging" a resource inevitably outweighs the cost where communal resources are concerned. All economically rational herdsman in the community will add as many animals as they can to their own herds and as quickly as they can (before other herdsmen do), meaning that the finite resources of the communal land will quickly become exhausted.
"Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit—in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all. Hardin thought that this conclusion challenged Adam Smith's famous observation that individuals intending only their own gain act, as if led by an invisible hand, in a way that tends to promote the public interest. Smith's theory (at least insofar as it has evolved into the mainstay of contemporary laissez-faire economics) is predicated on private, as opposed to communal, ownership of the means of production, however: a single owner of a resource in not having to compete for it, is perfectly motivated to preserve it in a way that unregulated communal owners are not. In a free market economy the Tragedy of the Commons is applicable mainly to resources which are not suitable for or capable of private ownership, such as the atmosphere, wilderness preserves and the ocean.
Like William Lloyd, Hardin was primarily interested in population and especially the problem of human population growth (see also Thomas Malthus). However, he also focused more generally on the use of other limited resources such as the atmosphere and oceans, as well as pointing out the 'negative commons' of pollution.
The "Tragedy of the commons" is a metaphor which should not be taken too literally as defining the concept. The phrase is shorthand for a phenomenon, not an accurate description of it. Hardin himself said that he used the word 'tragedy' in the sense that the philosopher Alfred North Whitehead used it: "the remorseless working of things". The "tragedy" should not be seen as tragic in the conventional sense, nor must it be taken as condemnation of the processes that are ascribed to it. Furthermore, Hardin's use of "commons" has frequently been misunderstood, leading Hardin to later remark that he should have titled his work, "The Tragedy of the Unregulated Commons".
The 'Tragedy of the Commons' has particular relevance in explaining behaviour in the fields of economics, evolutionary psychology, game theory and sociology. Some also see it as an example of emergent behaviour, with the 'tragedy' the outcome of individual interactions in a complex system.
Garrett Hardin's essay
At the beginning of his essay, Hardin draws attention to problems that cannot be solved by technical means (i.e. as opposed to those problems with solutions that require "a change only in the techniques of the natural sciences, demanding little or nothing in the way of change in human values or ideas of morality"). Hardin contends that this class of problems includes those raised by human population growth and the use of the Earth's natural resources.
To make the case for "no technical solutions", Hardin notes the limits placed on the availability of energy (and material resources) on Earth, and also the consequences of these limits for "quality of life". To maximize population, one needs to minimize resources spent on anything other than simple survival, and vice versa. Consequently, he concludes that there is no foreseeable technical solution to increasing both human populations and their standard of living on a finite planet.
From this point, Hardin switches to non-technical or resource management solutions to population and resource problems. As a means of illustrating these, he introduces a hypothetical example of a pasture shared by local herders. The herders are assumed to wish to maximise their yield, and so will increase their herd size whenever possible. The utility of each additional animal has both a positive and negative component:
Positive : the herder receives all of the proceeds from each additional animal Negative : the pasture is slightly degraded by each additional animal Crucially, the division of these components is unequal: the individual herder gains all of the advantage, but the disadvantage is shared between all herders using the pasture. Consequently, for an individual herder weighing up these utilities, the rational course of action is to add an extra animal. And another, and another. However, since all herders reach the same conclusion, overgrazing and degradation of the pasture is its long-term fate. Nonetheless, the rational response for an individual remains the same at every stage, since the gain is always greater to an individual than the distributed cost is. The overgrazing cost here is an example of an externality.
Because this sequence of events follows predictably from the behaviour of the individuals concerned, Hardin describes it as a tragedy: "the remorseless working of things" (in the sense described by the philosopher Alfred Whitehead). As such, it illustrates how "invisible hand" (laissez-faire) approaches to resource problems need not always provide the expected optimal solution. In Hardin's hypothetical commons, the action of self-interested individuals cannot promote the public good.
In the course of his essay, Hardin develops the theme, drawing in examples of latter day "commons", such as the atmosphere, oceans, rivers, fish stocks, National Parks, advertising and even parking meters. A major theme running throughout the essay is the growth of human populations, with the Earth's resources being a general commons (given that it concerns the addition of extra "animals", it is the closest to his original analogy).
The essay also addresses potential management solutions to commons problems including: privatization; polluter pays; regulation. Keeping with his original pasture analogy, Hardin categorises these as effectively the "enclosure" of commons, and notes a historical progression from the use of all resources as commons (unregulated access to all) to systems in which commons are "enclosed" and subject to differing methods of regulated use (access prohibited or controlled). Hardin argues against the reliance on conscience as a means of policing commons, suggesting that this favours selfish individuals over those more far-sighted.
In the context of avoiding over-exploitation of commons, Hardin concludes by restating Hegel's maxim (which was actually written by Engels), "Freedom is the recognition of necessity". He suggests that "freedom", if interpreted narrowly as simply the freedom to do as one pleases, completes the tragedy of the commons. By recognising resources as commons in the first place, and by recognising that, as such, they require management, Hardin believes that "we can preserve and nurture other and more precious freedoms".
Aside from its subject matter (resource use), the essay is notable (at least in modern scientific circles) for explicitly dealing with issues of morality, and doing so in one of the scientific community's premier journals, Science. Indeed, the subtitle for the essay is "The population problem has no technical solution; it requires a fundamental extension in morality".
Even today Hardin's essay, the Tragedy of the Commons is a source of controversy. Some of this stems from disagreement about whether individuals will always behave in the selfish fashion posited by Hardin (see discussion below).
More significantly, controversy has been fuelled by the "application" of Hardin's ideas to real situations. In particular, some authorities have read Hardin's work as specifically advocating the privatisation of commonly owned resources. Consequently, resources that have traditionally been managed communally by local organisations have been enclosed or privatised. Ostensibly this serves to "protect" such resources, but it ignores the pre-existing management, often unfairly appropriating resources and alienating indigenous (and frequently poor) populations. As Hardin's essay focuses on resources that are fundamentally unmanaged, rather than communally managed, this application of his ideas is misplaced. Ironically, given his original hypothetical example, this misunderstanding of Hardin's ideas is often applied to grazing lands.
More generally, Hardin made it very clear that usage of public property could be controlled in a number of different ways to stop or limit over-usage. His advocacy of clearly defined property rights has frequently been misread as an argument for privatization, or private property, per se. The opposite situation to a tragedy of the commons is sometimes referred to as a tragedy of the anticommons a situation where rational individuals (acting separately) collectively waste a given resource by under-utilizing it.
Hardin's essay introduces a hypothetical pasture as an analogy for "commons" in general. In this analogy, herders using the pasture do so on an individualistic basis, with no community management or oversight. However, actual historical commons were not public land and most were not open to the access of all — the public at large had very limited rights (e.g. passing drovers could lease grazing for "thistle rent"). Only those locals who were "commoners" had access to a bundle of rights; each commoner then had an interest in his own rights, but the common itself was not property.
These bundles of rights could not be traded or otherwise disposed of, but they applied in a medieval culture that recognised inalienable property (e.g. entailed inheritances), so under this system the bundles of rights were considered property. In a traditional English village these rights provided commoners with rights of grazing, gathering fuel wood non-destructively "by hook or by crook", etc. from anywhere on the common. (The form "commons" is plural, and refers to the whole group of individual pieces of common land subject to these effects).
Historically, most English commons were reserved for their own commoners (meaning members of that parish), whose use was restricted in various ways according to local custom. In response to overgrazing, for example, a common would be "stinted", that is, a limit would be put on the number of animals each commoner was allowed to graze. This stint might be related to the ownership of a commonable cottage, or to the amount of land owned in the open fields. These regulations were responsive to demographic and economic pressure; rather than let the commons be degraded, access was usually restricted even further. By the time of parliamentary enclosure, in many manors in southern England few labourers and poorer people held common grazing rights; enclosure, however, did have an impact on smaller landholders who supported their farming through use of common grazing and other resources. While historians continue to debate the significance and impact of enclosure on small landholders and labouring people in England, they agree that there is no evidence that commonland use was itself unsustainable.
Modern solutions to the 'tragedy'
Articulating solutions to the tragedy of the commons is one of the main problems of political philosophy. Many such solutions involve enforcement of conservation measures by an authority, which may be an outside agency or selected by the resource users themselves, who agree to cooperate to conserve the resource. Another frequently-proposed solution is to convert each common into private property, giving the owner of each an incentive to enforce its sustainability. Effectively, this is what took place in the English "Enclosure of the Commons." Increasingly, many agrarian studies scholars advocate studying traditional commons management systems, to understand how common resources can be protected without alienating those whose livelihoods depend upon them.
The idea of dividing the commons into private parcels is often advocated by classical liberals, who tend to argue that this division should be done according to the Lockean principle of homesteading   . This consists of allowing individuals to acquire property rights in a previously unowned resource by using it, on a "first come first served" basis .
The Coast Salish managed their natural resources in a place-based system where families were responsible for looking after a place and its resources . Access to food was the major source of wealth and the empowerment of generosity was highly valued so it made sense for them to take care of the resources.
A popular solution to the problem is also the "Coasian" one, where the individuals using the commons make payments to one another in exchange for not overusing the resource.
In Hardin's essay, he proposed that the solution to the problem of overpopulation must be based on "mutual coercion, mutually agreed upon" and result in "relinquishing the freedom to breed." Hardin discussed this topic further in a 1979 book, Managing the Commons, co-written with John A. Baden . He framed this prescription in terms of needing to restrict the "reproductive right" in order to safeguard all other rights. Only one large country has adopted this policy, the People's Republic of China. In the essay, Hardin had rejected education as an effective means of stemming population growth. Since that time, it has been shown that increased educational and economic opportunities for women correlates well with reduced birthrates in most countries, as does economic growth in general. Indeed, governments of some developed countries (e.g. Japan) are now concerned with raising rather than lowering the birthrate.
Application to evolutionary biology
The "tragedy of the commons" features highly in the field of evolutionary biology . The idea comes from the fact that individuals will always behave selfishly in order to maximise their fitness. Mostly, it has been applied to theories of social evolution, where it was widely held that altruism could not have evolved because the 'tragedy of the commons' would always favour selfish individuals; whose genes for selfish behaviour would therefore come to predominate. This contradicted observed reality, and was therefore a significant conceptual problem. The problem was eventually solved by models of possible mechanisms that can give rise to 'Reciprocal altruism', leading to ideas like the 'Tit for tat' rule (which states that it is beneficial to do unto others as they have done unto you). These models freed evolutionary theory from the limitations imposed by the concept of 'Inclusive fitness', a previous explanation for altruism, which proposed that organisms help others only to the extent that by doing so they increase the probability of passing shared genes to the next generation.
It has also been applied to other areas of sociobiology and behavioural ecology, such as in the evolution of virulence or sexual conflict, where males may fatally harm females when competing for matings . It is also widely used in studies of social insects, where scientists wish to understand why insect workers do not undermine the "common good" by laying eggs of their own and causing a breakdown of the society.
The idea of evolutionary suicide, where adaptation at the level of the individual causes the whole species or population to be driven extinct, can be seen as an extreme form of an evolutionary tragedy of the commons.