The structure of international environmental regimes must reflect the structure of the problem being addressed. A regime that protects biodiversity needs to use different tools, draw on different constituencies and have different institutional arrangements than one that protects the oceans from oil pollution, or one that manages international trade in endangered species. Nevertheless, most environmental regimes have come to respect several fundamental principles and to articulate them through their institutions. Many of these principles were laid out in the Rio Declaration on Environment and Development, another product of UNCED 1992. Six key principles are described below.

Prevention. It is generally expensive, difficult or impossible to repair environmental damage once it has occurred, so it is better to avoid such damage in the first place. This apparently self-evident fact has significant practical implications, since it requires action before there is any damage; that is, it requires action based on the possibility of damage.

Precaution. Calculating the possibility of damage is a difficult task, because our knowledge of ecological and environmental processes is frequently rudimentary at best, and is based on an evolving foundation of scientific research. Unfortunately, science does not always provide clear guidance on the measures that may be needed, so we are often faced with the task of making policy in the face of uncertainty. As articulated in the Rio Declaration, the precautionary principle states that lack of conclusive scientific evidence does not justify inaction, particularly when the consequences of inaction may be devastating or when the costs of action are negligible.

Subsidiarity. The linkages between individuals and the global consequences of their actions are a major challenge to the organization of environmental management. In particular it means that rules developed at one level—for example in international regimes—must be adapted to conditions in a wide variety of regional or local environments. The principle of subsidiarity calls for decision-making and responsibility to fall to the lowest level of government or political organization that can effectively take action.

Common but differentiated responsibility. Many environmental regimes require the participation of numerous countries, both rich and poor. But not all countries carry an equal responsibility for past environmental damage, and different countries have different resources at their disposal. So while the parties to environmental regimes all acknowledge common responsibility for the environment, they also work to develop differentiated responsibilities for addressing environmental problems.

Openness. Openness has two elements: transparency and public participation in policy-making. Both are necessary for good environmental management because protecting the environment requires the participation of literally countless people in many locations. Most environmental regimes are highly open, making use of environmental organizations, the media, and the Internet to communicate to the public. Many allow non-governmental organizations to participate in the discussions and negotiations of their provisions.

Polluter-pays principle. The polluter-pays principle was first propounded by the OECD in 1972. At that time it simply said that polluters should have to bear the full cost of meeting environmental regulations and standards. No subsidies should be given to help in this process. It has since evolved to become a broader principle of cost internalization—polluters should pay the full cost of the environmental damage that their activities produce. Of course, much of that cost will be passed along to consumers in the price of the goods involved, but this then discourages consumption of more pollution-intensive goods.

2.3 National environmental management