Precautionary principle

The Precautionary Principle illustrated as a decision matrix

The precautionary principle is the concept that establishes it is better to avoid or mitigate an action or policy that has the plausible potential, based on scientific analysis, to result in major or irreversible negative consequences to the environment or public even if the consequences of that activity are not conclusively known, with the burden of proof that it is not harmful falling on those proposing the action. It is a major principle of international environmental law and is extended to other areas and jurisdictions as well.

This principle is important in that it allows one to anticipate harm and take appropriate precautions even in the absence of scientific consensus that the action or policy is harmful and what might be the level of harm. As a result, policy makers are able to make discretionary decisions to delay such an action until scientific findings emerge that provide sound evidence that no harm will result. It is analogous to such commonplace aphorisms as “an ounce of prevention is worth a pound of cure," “better safe than sorry," “look before you leap," and the ancient medical principle associated with Hippocrates of "First, do no harm."

In some legal systems, as in the law of the European Union, the application of the precautionary principle has been made a statutory requirement. However, a rigid application of this principle also has drawbacks, such as ignoring possible risks associated with not doing the proposed activity or policy, perhaps resulting in banning a technology that brings advantages out of concern for potential negative impacts. Under such a scenario, the cellular phone might not have been permitted until it could be proved not to be a carcinogen. In the case of the pesticide DDT, if the precautionary principle were to be applied universally and narrowly, it would mean that DDT could not even be introduced into regions heavily infected by malaria because of the deleterious potential impacts of DDT on the fauna.

The precautionary principle recognizes a social responsibility to protect the public from exposure to harm, when scientific investigation has found a plausible risk. Its development as part of international law reflects a growing international recognition of the human responsibility to care for the environment and others and to find legal avenues to prevent actions that might cause severe or irreversible consequences to either.



Basic components

Many definitions of the precautionary principle exist, with precaution itself defined as “caution in advance,” “caution practiced in the context of uncertainty," or “informed prudence.” All definitions of the precautionary principle have three major components:

  1. Anticipate harm and take action to minimize potential harm. This is an expression of a need by decision-makers to anticipate harm before it occurs and an obligation, if the level of harm may be high, for action to prevent or minimize such harm.
  2. Onus of proof on proponent. Under the precautionary principle, it is the responsibility of an activity proponent to establish that the proposed activity will not (or is very unlikely to) result in significant harm. This is an implicit reversal of the typical onus of proof, whereby harm needs to be demonstrated.
  3. Absence of scientific certainty not an obstacle. The precautionary principle is activated even when the absence of scientific certainty makes it difficult to predict the likelihood of harm occurring, or the level of harm should it occur. There is an obligation, if the level of harm may be high, for action to prevent or minimize such harm, with the control measures increasing with both the level of possible harm and the degree of uncertainty.

It is important to note that, although this principle operates in the context of scientific uncertainty, it generally is considered by its proponents to be applicable only when, on the basis of the best scientific advice available, there is good reason to believe that harmful effects might occur.

Diverse formulations of the precautionary principle

Rio Declaration.; One of the primary foundations of the precautionary principle, and globally accepted definitions, results from the work of the Rio Conference, or "Earth Summit" in 1992. Principle #15 of the Rio Declaration notes (UNEP 1992):

"In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation."

This definition is important for several reasons. First, it explains the idea that scientific uncertainty should not preclude preventative measures to protect the environment. Second, the use of "cost-effective" measures indicates that costs can be considered. This is different from a "no-regrets" approach, which ignores the costs of preventative action.

Note that this definition uses the term “precautionary approach” rather than “precautionary principle,” a not unimportant distinction given the power of law that the term "principle" is sometimes held to convey. (See "Principle" vs. "approach”.)

COMEST/UNESCO. UNESCO's World Commission on the Ethics of Scientific Knowledge and Technology (COMEST) published an analysis and definition of the term in 2005. This definition, developed by an international panel of leading scholars from scientific, legal, philosophical, cultural, and political disciplines, is a compromise formulation designed to address a number of the most important criticisms and weaknesses identified by critics of earlier versions. It states:

"When human activities may lead to morally unacceptable harm that is scientifically plausible but uncertain, actions shall be taken to avoid or diminish that harm."

The precise meaning of each of the major components of this definition ("morally unacceptable harm," "scientifically plausible," "uncertainty," and "actions") are further detailed in the COMEST/UNESCO report.

Wingspread Statement. The 1998 Wingspread Statement on the Precautionary Principle summarizes the principle this way:

"When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically."

The Wingspread Conference on the Precautionary Principle was convened by the Science and Environmental Health Network.

European Commission. The February 2, 2000 European Commission Communication on the Precautionary Principle notes:

"The precautionary principle applies where scientific evidence is insufficient, inconclusive or uncertain and preliminary scientific evaluation indicates that there are reasonable grounds for concern that the potentially dangerous effects on the environment, human, animal or plant health may be inconsistent with the high level of protection chosen by the EU."

Cartagena Protocol. The January 29, 2000 Cartagena Protocol on Biosafety states:

"Lack of scientific certainty due to insufficient relevant scientific information . . . shall not prevent the Party of import, in order to avoid or minimize such potential adverse effects, from taking a decision, as appropriate, with regard to the import of the living modified organism in question."

Intergovernmental Agreement on the Environment (Australia). The May 1992 Intergovernmental Agreement on the Environment, signed by all the heads of government in Australia, defines the precautionary principle in this way

(Harding and Fisher 1999b):

"Where there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation. In the application of the precautionary principle, public and private decisions should be guided by: (i) careful evaluation to avoid, wherever practicable, serious or irreversible damage to the environment; and (ii) an assessment of the risk-weighted consequences of various options."

Application of the precautionary principle


The precautionary principle is most often applied in the context of the impact of human actions on the environment and human health, as both involve complex systems where the consequences of actions may be unpredictable.

As applied to environmental policy, the precautionary principle stipulates that for practices such as the release of radiation or toxins or massive deforestation, the burden of proof lies with the advocates of the proposed practices. Concerning potential risks to public health, examples of cases in which the precautionary principle has been advocated (but not always accepted) are: the commercialization of genetically modified foods, the use of growth hormones in cattle raising, measures to prevent "mad cow" disease, health claims linked to phthalates in PVC toys, among many others.

An important element of the precautionary principle is that its most meaningful applications pertain to those that are potentially irreversible, for example where biodiversity may be reduced. With respect to bans on substances like mercury in thermometers, freon in refrigeration, or even carbon dioxide exhaust from automobile engines and power plants, it implies (O'Riordan and Cameron 1994):

"... a willingness to take action in advance of scientific proof [or] evidence of the need for the proposed action on the grounds that further delay will prove ultimately most costly to society and nature, and, in the longer term, selfish and unfair to future generations."

The concept includes an implicit ethical responsibility towards maintaining the integrity of natural systems, and acknowledges the fallibility of human understanding.

The application of the precautionary principle is hampered by both lack of political will, as well as the wide range of interpretations placed on it. Some proponents hold a view that there should be regulation even if the supporting evidence of possible risk is speculative and even if the costs of regulation are very high, while others support a less stringent view. (See Strong precaution versus weak precaution.) One some stringent interpretation of the precautionary principle holds that proponents of a new potentially harmful technology must show the new technology is without major harm before the new technology is used (EEB 1999; SEHN 2000).

Environment and health applications

Fields typically concerned by the precautionary principle are the possibility of:

  • Global warming or other abrupt climate change
  • Extinction of species
  • Introduction of new and potentially harmful products into the environment, threatening biodiversity (e.g., genetically modified organisms)
  • Threats to public health, due to new diseases and techniques (e.g., AIDS transmitted through blood transfusion)
  • Persistent or acute pollution (asbestos, endocrine disruptors, etc.)
  • Food safety (e.g., Creutzfeldt-Jakob disease)
  • Other new biosafety issues (e.g., artificial life, new molecules)

The precautionary principle is often applied to biological fields because changes cannot be easily contained and have the potential of being global. The principle has less relevance to contained fields such as aeronautics, where the few people undergoing risk have given informed consent (e.g., a test pilot). In the case of technological innovation, containment of impact tends to be more difficult if that technology can self-replicate. The application of the principle can be seen in the public policy of requiring pharmaceutical companies to carry out clinical trials to show that new medications are safe.

Levels of application

Stewart (2002) reduced application of the precautionary principle to four basic versions:

  1. Scientific uncertainty should not automatically preclude regulation of activities that pose a potential risk of significant harm (Non-Preclusion PP).
  2. Regulatory controls should incorporate a margin of safety; activities should be limited below the level at which no adverse effect has been observed or predicted (Margin of Safety PP).
  3. Activities that present an uncertain potential for significant harm should be subject to best technology available requirements to minimize the risk of harm unless the proponent of the activity shows that they present no appreciable risk of harm (BAT PP).
  4. Activities that present an uncertain potential for significant harm should be prohibited unless the proponent of the activity shows that it presents no appreciable risk of harm (Prohibitory PP).

In deciding how to apply the principle, analysis may use a cost-benefit analysis that factors in both the opportunity cost of not acting, and the option value of waiting for further information before acting. One of the difficulties of the application of the principle in modern policy-making is that there is often an irreducible conflict between different interests, so that the debate necessarily involves politics.

Strong vs. weak

Strong precaution holds that regulation is required whenever there is a possible risk to health, safety, or the environment, even if the supporting evidence is speculative and even if the economic costs of regulation are high. A strong form of the precautionary principle, for example, would call for measures to lessen the risk of environmental harm induced by climate change by incorporating a focus on reducing or preventing the emission of greenhouse gases. In 1982, the United Nations World Charter for Nature gave the first international recognition to the strong version of the principle, suggesting that when "potential adverse effects are not fully understood, the activities should not proceed" (Goliath 2002). The widely publicized Wingspread Declaration, from a meeting of environmentalists in 1998, is another example of the strong version (Goliath 2002). "Strong precaution" can also be termed as a "no-regrets" principle, where costs are not considered in preventative action.

Weak precaution holds that lack of scientific evidence does not preclude action if damage would otherwise be serious and irreversible. Humans practice weak precaution every day, and often incur costs, to avoid hazards that are far from certain: we do not walk in moderately dangerous areas at night, we exercise, we buy smoke detectors, we buckle our seat belts (Goliath 2002).

According to a publication of the New Zealand Treasury (Cameron 2006):

The weak version [of the Precautionary Principle] is the least restrictive and allows preventive measures to be taken in the face of uncertainty, but does not require them (eg., Rio Declaration 1992; United Nations Framework Convention of Climate Change 1992). To satisfy the threshold of harm, there must be some evidence relating to both the likelihood of occurrence and the severity of consequences. Some, but not all, require consideration of the costs of precautionary measures. Weak formulations do not preclude weighing benefits against the costs. Factors other than scientific uncertainty, including economic considerations, may provide legitimate grounds for postponing action. Under weak formulations, the requirement to justify the need for action (the burden of proof) generally falls on those advocating precautionary action. No mention is made of assignment of liability for environmental harm.

Strong versions justify or require precautionary measures and some also establish liability for environmental harm, which is effectively a strong form of “polluter pays.” For example, the Earth Charter states: “When knowledge is limited, apply a precautionary approach …. Place the burden of proof on those who argue that a proposed activity will not cause significant harm, and make the responsible parties liable for environmental harm.” Reversal of proof requires those proposing an activity to prove that the product, process or technology is sufficiently “safe” before approval is granted. Requiring proof of “no environmental harm” before any action proceeds implies the public is not prepared to accept any environmental risk, no matter what economic or social benefits may arise (Peterson 2006). At the extreme, such a requirement could involve bans and prohibitions on entire classes of potentially threatening activities or substances (Cooney 2005). Over time, there has been a gradual transformation of the precautionary principle from what appears in the Rio Declaration to a stronger form that arguably acts as restraint on development in the absence of firm evidence that it will do no harm.

Origins and theory

Many of the concepts underpinning the precautionary principle pre-date the term's inception. For example, the essence of the principle is captured in a number of cautionary aphorisms such as "an ounce of prevention is worth a pound of cure," "better safe than sorry," and "look before you leap." The precautionary principle may also be interpreted as the evolution of the ancient medical principle of "first, do no harm" to apply to institutions and institutional decision-making processes rather than individuals.

The precautionary principle is in some ways an expansion of the English common law concept of "duty of care" originating in the decisions of the judge Lord Esher in the late 1800s. According to Lord Esher: “Whenever one person is by circumstances placed in such a position with regard to another that everyone of ordinary sense who did think, would at once recognise that if he did not use ordinary care and skill in his own conduct with regard to those circumstances, he would cause danger or injury to the person, or property of the other, a duty arises to use ordinary care and skill to avoid such danger.” This statement clearly contains elements of foresight and responsibility, but does not refer to a lack of certainty, as the word “would” is used rather than “might,” or “could.” The other important difference is that the duty of care applies only to people and property, not to the environment.

The origins of the formal concept have been attributed to the German socio-legal tradition in the 1930s, centering on the concept of good household management and known in German as Vorsorgeprinzip, which translates into English as precaution principle (Harding and Fisher 1999b; O'Riodan and Cameron 1994). This Vorsorgeprinzip was tied to the German Air Pollution legislation of the 1970s, but also part of a range of decision-making processes. Vorsorgeprinzip allows prevention of damage to the environment prior to proof of damage and is one of the fundamental principles underlying German environmental policies today (Harding and Fisher 1999b).

the first international endorsement of the precautionary principle was by the World Charter for Nature, which was adopted by the United Nations General Assembly in 1982. The principle was implemented in an international treaty as early as the 1987 Montreal Protocol, In treaty usage, a seminal point was the use of the principle in Principle 15 of the 1992 Rio Declaration on Environment and Development (signed at the United Nations Conference on Environment and Development).

In economics, the precautionary principle has been analyzed in terms of the effect on rational decision-making of the interaction of irreversibility and uncertainty. Authors such as Epstein (1980) and Arrow and Fischer (1974) show that irreversibility of possible future consequences creates a quasi-option effect, which should induce a "risk-neutral" society to favor current decisions that allow for more flexibility in the future. Gollier et al. (2000) conclude that "more scientific uncertainty as to the distribution of a future risk—that is, a larger variability of beliefs—should induce society to take stronger prevention measures today."


Threshold of plausibility

One of the concerns about the precautionary principle is how to establish the threshold of plausibility; in other words, since it can be activated in the face of scientific uncertainty, what is the point where there is good reason to believe that harmful effects might occur. For example, in the Wingspread Statement version, the precautionary principle takes the form of "When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically." The level at which activity raises threats of harm is very vague.

When applying this principle, it is recommended that society establish a minimal threshold of scientific certainty or plausibility before undertaking precautions. However, normally, no minimal threshold of plausibility is specified as a “triggering” condition, so that any indication that a proposed product or activity might harm health or the environment is sufficient to invoke the principle. Often the only precaution taken is a ban on the product or activity (van den Belt 2003).

Excessive discretion of decision-makers

Related to the threshold of plausibility, "decision-makers have a high level of discretion as to when and how to apply the precautionary principle" (Peterson 2006). The resultant inconsistent and unpredictable application of the principle creates a difficult environment for business to work and grounds for legal challenges that likewise can lead to diverse interpretations (Peterson 2006). This aspect also leads to the danger of decision-makers using their political power to invoke the principle as a means to advance a course of action (such as having people invest in a particular "solution") that benefits the decision makers or their friends.


Critics of the principle argue that it is impractical, since every implementation of a technology carries some risk of negative consequences (Sunstein 2002, 2005). For example, when the arrival of amplified music came on the scene, the risk of electrocution and deafness arose. However, this did not prevent it from becoming an artistic and cultural norm.

Ignores possible risk of not doing the activity

There is an inherent fallacy in extrapolating possible risk of a proposed product or action, without examining equally closely the possible risks of not adopting the proposal. When considering a proposal, policymakers tend to apply the precautionary principle to the proposal while assuming the alternative—not doing the action—is risk free, placing an unfair burden on proponents of the activity or product (Seethaler 2009).

Stifling of positive benefits

The precautionary principle tends to be very risk aversive. Because of this effect, a technology that brings advantages may be banned by the precautionary principle because of its potential for negative impacts, leaving the positive benefits unrealized (Sunstein 2002). Under the stronger versions of the precautionary principle, you can get a "stifling of technological innovation and paralysis of development" (Cameron 2006).

In addition, Bailey (1999) notes the potential that "anyone who merely raises 'threats of harm' with no more evidence than their fearful imagination gets to invoke precautionary measures." This could have the impact of stymieing proposed actions.

On the other hand, use of the precautionary principle could lead to innovation in that alternatives are sought to the avenue that has been closed off. However, Cameron (2006) notes that "this is likely to be at the margin compared with the wider stifling effect that strong forms of the principle can have."

Health versus environment

In the Wingspread Statement version of the precautionary principle, there are two areas in which the precautionary principle may be cited, health and the environment: "When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically."

However, how does one apply the precautionary principle when these two factors—health and the environment—are at odds. Bailey (1999) notes: "One troublesome issue is that some activities that promote human health might 'raise threats of harm to the environment,' and some activities that might be thought of as promoting the environment might 'raise threats of harm to human health. Bailey cites the use of pesticides, which have been used to control deadly disease-carrying insects and protect crops, and thus have improved the human health of millions. Yet, some pesticides have side effects that are harmful to the environment, such as harming other, non-targeted species.

Bailey (1999) also expresses a concern that the precautionary principle is being used to promote the environmental position over human health:

"Proponents of the Precautionary Principle are trying to smuggle in a default position: The environment trumps all other values. Yet the panelists all pretended that the Principle is a value-neutral scientific procedure for determining which policies humanity should pursue. The fact is that the Precautionary Principle incorporates the values of the most extreme versions of know-nothing environmentalism."

Cause of resentment

The precautionary principle may cause resentment, since people are more aware of negative changes than they are of positive changes (i.e. a ban is more noted than allowing a proposal to proceed).

Promotes over-regulation of human activities

Once concern is that the precautionary principle can lead to human activities being over-regulated, since there is potential for harm in many activities.

Overly broad

Bailey (1999) expresses concern that the precautionary principle is too broad and can be applied for many different agendas. With the heart of the principle being that precautionary measures can be taken even when cause-and-effect relationships are not fully established by scientific means, "the Precautionary Principle could logically apply to every conceivable activity, since their outcomes are always in some sense uncertain." And beyond science, he maintains it can applied to any activity, such as precaution against raising taxes because of risk to economic growth although "the cause-and-effect relationships are not fully established economically" or opposing employment tests because of possible harm to equality although "the cause-and-effect relationships are not fully established sociologically."

Reversal of the burden of proof

There is a reverse onus on the burden of proof in that that proponent of an activity or policy bears the burden of proof rather than the public proving that harm is caused. Thus, proponents of an activity have to demonstrate that the activity, such as a new technology, is safe. In other words, "guilty until proven innocent" rather than "innocent until proven guilty" (van den Belt 2003). Bailey (1999) notes the comment of one bioethicist who favors the precautionary principle: "The truth of the matter is that whoever has the burden of proof loses." Bailey compares it to a newborn baby having to prove it will never grow up to be a schoolyard bully or serial killer before it is allowed to leave the hospital. And inventor, manufacturer or scientists would need to prove their inventions would never cause harm to human health or the environment before being allowed to produce them. Proving a negative is very difficult given that there is no way to test all the possible effects on all the species. Cameron (2006) notes this reversal of the burden of proof could impose excessive costs on producers and developers.

Misuse as a protectionist barrier

Cameron (2006)notes the danger of using the precautionary principle as a protectionist barrier—"open to misuse and opportunistic manipulation by rent-seeking and commercial interests." Thus, a competing product could be opposed on the grounds of potential harm. According to Cameron, it already has been "implicated in number of trade disputes. An example is the European Union imposing import barriers on hormone treated beef and genetically modified food products."

"Principle" vs. "approach"

The term "precautionary approach" has been used at times rather than "precautionary principle. For example, the United States has opposed the use of the term precautionary principle because the term principle "has special connotations in legal language, due to the fact that a ´principle of law` is a source of law. This means that it is compulsory, so a court can quash or confirm a decision through the application of the precautionary principle" (Recuerda 2008). For this reason, Principle 15 of the Rio Declaration 1992 states that: “in order to protect the environment, the precautionary approach [italics added] shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall be not used as a reason for postponing cost-effective measures to prevent environmental degradation.”

As such, the term "approach" is generally considered a softening of the term "principle." However, the World Commission on the Ethics of Scientific Knowledge and Technology (COMEST), in its 2005 report, sees the distinction in the term principle being "employed as the philosophical basis of the precaution" and the term approach being "its practical application." As such, COMEST notes that while the term precautionary approach has often been used in international settings, the terms are closely related and the Rio Declaration "uses the word 'approach' in the English version, and the word 'principio' in the Spanish version." COMEST further goes on to state "where the PP has reached the status of a general principle of law or a customary rule of international law, those that prefer the term 'approach' sometimes deny such status to it."

Specific examples of application

European Commission

On February 2, 2000, the European Commission issued a Communication on the precautionary principle in which it adopted a procedure for the application of this concept, but without giving a detailed definition of it. Paragraph 2 of article 191 of the Lisbon Treaty states that (EU 2010):

"Union policy on the environment shall aim at a high level of protection taking into account the diversity of situations in the various regions of the Union. It shall be based on the precautionary principle and on the principles that preventive action should be taken, that environmental damage should as a priority be rectified at source and that the polluter should pay."

After the adoption of the European Commission's Communication on the precautionary principle, the principle has come to inform much EU policy, including that in areas beyond that of environmental policy. It is implemented, for example, in the EU food law and also affects, among others, policies relating to consumer protection, trade and research, and technological development. While a comprehensive definition of the precautionary principle was never formally adopted by the EU, a working definition and implementation strategy for the EU context has been proposed by Rene von Schomberg (Fisher et al. 2006):

"Where, following an assessment of available scientific information, there are reasonable grounds for concern for the possibility of adverse effects but scientific uncertainty persists, provisional risk management measures based on a broad cost/benefit analysis whereby priority will be given to human health and the environment, necessary to ensure the chosen high level of protection in the Community and proportionate to this level of protection, may be adopted, pending further scientific information for a more comprehensive risk assessment, without having to wait until the reality and seriousness of those adverse effects become fully apparent."

United States

In the United States, "the precautionary principle is not expressly mentioned in any [Federal] laws or policies" ( 2010). However, there are some Federal laws that do reflect this principle, such as the Occupational Safety and Health Act (OSHA), which requires precautionary actions if a workplace chemical is suspected of being carcinogenic ( 2010).

On July 18, 2005, the City of San Francisco passed a Precautionary Principle Purchasing ordinance, which requires the city to weigh the environmental and health costs of its $600 million in annual purchases—for everything from cleaning supplies to computers. It also established a Precautionary Principle Policy Statement, which includes the "San Francisco Precautionary Principle" as follows (SF 2010):

"Where threats of serious or irreversible damage to people or nature exist, lack of full scientific certainty about cause and effect shall not be viewed as sufficient reason for the City to postpone cost effective measures to prevent the degradation of the environment or protect the health of its citizens. Any gaps in scientific data uncovered by the examination of alternatives will provide a guidepost for future research, but will not prevent the City from taking protective action. As new scientific data become available, the City will review its decisions and make adjustments when warranted."


In 1997, Japan tried to use the consideration of the precautionary principle in a World Trade Organization SPS Agreement on the Application of Sanitary and Phytosanitary Measures case, as Japan’s requirement to test each variety of agricultural products (apples, cherries, peaches, walnuts, apricots, pears, plums and quinces) for the efficacy of treatment against codling moths was challenged. This moth is a pest that does not occur in Japan, and whose introduction has the potential to cause serious damage. The United States claimed that it was not necessary to test each variety of a fruit for the efficacy of the treatment, and that this varietal testing requirement was unnecessarily burdensome.


The May 1992 Intergovernmental Agreement on the Environment, signed by all the heads of government in [[Australia], defines the precautionary principle in this way (Harding and Fisher 1999b): "Where there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation. In the application of the precautionary principle, public and private decisions should be guided by: (i) careful evaluation to avoid, wherever practicable, serious or irreversible damage to the environment; and (ii) an assessment of the risk-weighted consequences of various options." This definition derives from the near-identical New South Wales Protection of the Environment Administration Act 1991.

The most important Australian court case so far, due to its exceptionally detailed consideration of the precautionary principle, is Telstra Corporation Limited v Hornsby Shire Council. The case was heard in the New South Wales Land and Environment Court under Justice CJ Preston (24 April 2006). The most significant points of Justice Preston's decision are the following findings:

  1. The principle and accompanying need to take precautionary measures is "triggered" when two prior conditions exist: a threat of serious or irreversible damage, and scientific uncertainty as to the extent of possible damage.
  2. Once both are satisfied, "a proportionate precautionary measure may be taken to avert the anticipated threat of environmental damage, but it should be proportionate."
  3. The threat of serious or irreversible damage should invoke consideration of five factors: the scale of threat (local, regional etc); the perceived value of the threatened environment; whether the possible impacts are manageable; the level of public concern, and whether there is a rational or scientific basis for the concern.
  4. The consideration of the level of scientific uncertainty should involve factors which may include: what would constitute sufficient evidence; the level and kind of uncertainty; and the potential to reduce uncertainty.
  5. The principle shifts the burden of proof. If the principle applies, the burden shifts: "a decision maker must assume the threat of serious or irreversible environmental damage is… a reality [and] the burden of showing this threat… is negligible reverts to the proponent…"
  6. The precautionary principle invokes preventative action: "the principle permits the taking of preventative measures without having to wait until the reality and seriousness of the threat become fully known."
  7. “The principle should not be used to try to avoid all risks."
  8. The precautionary measures appropriate will depend on the combined effect of "the degree of seriousness and irreversibility of the threat and the degree of uncertainty… the more significant and uncertain the threat, the greater…the precaution required." “…measures should be adopted… proportionate to the potential threats."

Change of laws controlling societal norms

Associate Justice Martha Sosman's dissent in Goodridge v. Department of Public Health, the decision of the Supreme Judicial Court of Massachusetts that mandated legalization of same sex marriage, is an example of the precautionary principle as applied by analogy to changes in culturally significant social policy (Goodridge 2003). Justice Sosman describes the myriad societal structures that rest on the institution of marriage, and points out the uncertainty of how they will be affected by this re-definition. The disagreement of the majority illustrates the difficulty of reaching agreement on the value of competing perspectives.

Resource management

The Traffic Light color convention, showing the concept of Harvest Control Rule (HCR), specifying when a rebuilding plan is mandatory in terms of precautionary and limit reference points for spawning biomass and fishing mortality rate.

Several natural resources like fish stocks are now managed by precautionary approach, through Harvest Control Rules (HCR) based upon the precautionary principle. The figure indicates how the principle is implemented in the cod fisheries management proposed by the International Council for the Exploration of the Sea.

In classifying endangered species, the precautionary principle means that if there is doubt about an animal's or plant's exact conservation status, the one that would cause the strongest protective measures to be realized should be chosen. Thus, a species like the silvery pigeon that might exist in considerable numbers and simply be under-recorded or might just as likely be extinct is not classified as "data deficient" or "extinct" (which both do not require any protective action to be taken), but as "critically endangered" (the conservation status that confers the need for the strongest protection). Similarly, the increasingly rare, but probably not yet endangered emerald starling is classified as "data deficient," because there is urgent need for research to clarify its status rather than for conservation action to save it from extinction.

See also


  • Arrow, K. J., and A. C. Fischer. 1974. Environmental preservation, uncertainty and irreversibility. Quarterly Journal of Economics 88 (2): 312–9.
  • Cooney, R. 2005. From promise to practicalities: The precautionary principle on biodiversity conservation and sustainable use. Chapter 1 in R. Cooney and B. Dickson (Eds.), Biodiversity and the Precautionary Principle: Risk and Uncertainty in Conservation and Sustainable Use. London: Earthscan. ISBN 1844072770.
  • Epstein, L. S. 1980. Decision-making and the temporal resolution of uncertainty. International Economic Review 21(2): 269–283.
  • Fisher, E., J. Jones, and R. von Schomberg. (Eds). 2006. Implementing the Precautionary Principle: Perspectives and Prospects. Cheltenham, UK: Edward Elgar. ISBN 1845427025.
  • Gollier, C., B. Jullien, and N. Treich. 2000. Scientific progress and irreversibility: An economic interpretation of the "precautionary principle." Journal of Public Economics 75(2): 229–253.
  • Harding, R., and E. Fisher. 1999a. Perspectives on the Precautionary Principle. Sydney, Australia: The Federation Press. ISBN 1862873186.
  • Harding, R., and E. Fisher. 1999b. Introducing the precautionary principle. In R. Harding and E. Fisher, Perspectives on the Precautionary Principle. Sydney, Australia: The Federation Press. ISBN 1862873186.
  • Peterson, D. 2006. Precaution: Principles and practice in Australian environmental and natural resource management." Productivity Commission. Presidential Address, 50th Annual Australian Agricultural and Resource Economic Society Conference. Manly, New South Wales.
  • Recuerda, M. A. 2006. Risk and reason in the European Union Law. European Food and Feed Law Review 5.
  • Recuerda, M. A. 2008. Dangerous interpretations of the precautionary principle and the foundational values of the European Union Food Law: Risk versus risk. Journal of Food Law & Policy 4(1).
  • Seethaler, S. 2009. Lies, Damned Lies, and Science: How to Sort through the Noise around Global Warming, the Latest Health Claims, and Other Scientific Controversies. Upper Saddle River, NJ: FT Press. ISBN 9780137155224.
  • Stewart, R. B. 2002. Environmental regulatory decision making under uncertainty. Research in Law and Economics 20: 76.
  • Sunstein, C. R. 2005. Laws of Fear: Beyond the Precautionary Principle. New York: Cambridge University Press. ISBN 9780521848237.
  • World Commission on the Ethics of Scientific Knowledge and Technology (COMEST). 2005. The Precautionary Principle). United Nations Educational, Scientific and Cultural Organization (UNESCO). Retrieved September 3, 2013.

This article also incorporates discussion points on the COMEST/UNESCO formulation provided by Robert Adams. (See Feedback: Comment by Robert Adams).


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