The definition and characteristics of common pool resources

Common pool resources, also known as common access resources, are natural assets that no single individual or entity owns, but which are freely available for use by anyone without charge.

Key features of common pool resources

• Non-excludable nature - It is difficult or impossible to prevent people from accessing and using the resource, as there are no barriers to entry.
• Rival or subtractable quality - Use by one person reduces the amount or quality available for others, a concept known as subtractability. For example, if someone draws water from a shared lake, less remains for the community, forcing others to expend more effort to obtain the same quantity.
• Renewable potential - Many common pool resources can naturally replenish over time, such as through growth or regeneration, provided they are not overexploited by human activity.

Examples of common pool resources

• Fisheries, where fish populations can recover if not overfished.
• Forests, which provide timber and other materials but can be depleted through excessive logging.
• Wildlife, pastures, irrigation systems, hunting grounds, lakes, and the atmosphere, all of which are accessible to multiple users but vulnerable to overuse.

These characteristics mean that while individuals gain full personal benefits from using the resource, the associated costs—such as depletion—are distributed across all users, often leading to unsustainable practices.

The tragedy of the commons and its causes

The tragedy of the commons describes a situation where open access to a shared resource results in its overuse and eventual depletion. This concept was popularised by ecologist Garrett Hardin in a 1968 paper published in the journal Science.

Causes of the tragedy of the commons

• Individual incentives - Users focus on maximising their own benefits, such as harvesting as much as possible, without accounting for the long-term impact on the resource's availability for everyone.
• Shared costs - The negative effects of overuse, like reduced quality or quantity, are borne by the entire group, not just the individual exploiter.
• Lack of ownership - Without private ownership or effective controls, there is little motivation for users to conserve the resource for future use.

Real-world evidence of overuse

• Overharvesting in public forests can lead to the rapid depletion of resources like wild berries, as people collect without regard for natural regeneration.
• According to the United Nations Food and Agriculture Organization, a large proportion of global fish stocks are either fully exploited or overexploited, with some estimates suggesting over 87%.
• Deforestation has resulted in the loss of more than 1.3 million square kilometres of forest worldwide between 1990 and 2016.

These examples illustrate how unchecked access can transform renewable resources into scarce ones, threatening environmental and economic stability.

Economic analysis of common resource overuse

From an economic perspective, the overuse of common pool resources arises because decision-makers consider only their private costs, ignoring the broader societal impacts.

Marginal costs in resource use

• Marginal private cost (MPC) - Represents the cost borne directly by the individual user.
• Marginal social cost (MSC) - Includes both private costs and external costs imposed on society, such as environmental degradation. The MSC curve is steeper than the MPC curve, reflecting escalating external costs as depletion intensifies.

Socially optimal versus market outcomes

The socially optimal level of resource use (Q_s*) occurs where marginal social benefit (MSB) equals MSC, resulting in a lower quantity than the market-driven level (Q_m), where decisions are based solely on MPC.

This analysis highlights the inefficiency of unregulated common resources, as the market quantity exceeds the sustainable level, accelerating depletion.

Responses to sustainability threats for common resources

To address overuse and promote sustainability, various strategies can be implemented, ranging from government-led interventions to community-based approaches.

Government regulation

Governments can impose controls such as quotas, licences, permits, protected areas, and emission standards to limit access and usage.

International agreements

Global cooperation is essential for transboundary resources like the atmosphere.

Key examples include:

• The 1992 Rio Earth Summit, which established frameworks for sustainable development.
• The 1997 Kyoto Protocol, aimed at reducing greenhouse gas emissions.
• The 2015 Paris Agreement, adopted by 197 countries, which seeks to cap global temperature rises at below 2°C (preferably 1.5°C) above pre-industrial levels.

Education and behavioural change

Raising awareness about environmentally responsible practices encourages users to adopt sustainable behaviours, reducing overuse through voluntary actions.

Collective self-governance

Economist Elinor Ostrom, who won the Nobel Prize in Economics in 2009, advocated for community-managed systems as an alternative to top-down or privatisation methods.

Requirements for successful self-governance:

• The resource not being overly degraded already.
• Access to reliable, affordable information on the resource's condition.
• Users relying on the resource for their livelihoods.
• A shared understanding among users of how actions impact one another and the resource.
• Mutual trust, with commitments to reciprocity and promise-keeping.

Factors affecting success:

• Smaller, homogeneous groups tend to organise more effectively than large, diverse ones.
• Essential elements for success include clearly defined boundaries, collective decision-making processes, monitoring systems, and mechanisms for resolving conflicts.