Science is the starting point of all environmental policy. Without science we have no way of knowing what is happening in the natural environment, beyond what our senses tell us. Science makes the environment speak, and all policy-making is based on interests that have voices. But the scientific method does not always generate precise information for policy-making—scientific knowledge is rarely either certain or complete. And even where science is quite certain—for example, in its assertion that certain gases in the atmosphere trap heat and can change the planet's climate—the implications for policy can be obscure.

The tension between science and policy is a constant theme of international environmental regimes. All of these regimes have some method of reviewing new scientific evidence, often through their Conference of Parties, sometimes through their own subsidiary bodies, or, in exceptional cases such as the climate regime, through specially created independent organizations such as the Intergovernmental Panel on Climate Change.

The precautionary principle, described in chapter 2 as a basic environmental principle, counsels that environmental measures must sometimes be adopted even when scientific information is incomplete. It has proven difficult to implement since it requires that policy-makers exercise some discretion. For this reason it is important to develop criteria governing its application. Among other things, these criteria would address a balance of two important considerations: the scale of possible damage, and the cost of action—or of inaction.

As the scale of possible damage increases, so does the need to act with precaution. Where the potential damage is obvious, as with stratospheric ozone depletion, the need for action becomes clearer and less contentious. Where the potential is less obvious, precautionary action can become extremely contentious, as affected stakeholders seek to protect their interests. Indeed, it is normal to expect controversy over action on such issues as genetically modified organisms, where the science is still unclear and is evolving rapidly.

Some governments use the tools of risk assessment to minimize the scope for discretion in applying the precautionary principle. This will delay action, and can leave so many issues unresolved that decision-making is not necessarily facilitated.

Cost is the other criterion to consider in applying the precautionary principle. Resources are limited so governments must make tough decisions about where to apply them. Clearly, precautionary actions that are without net economic cost should be taken. But since such actions may involve losses in one area, even though they are counterbalanced by gains in another, they may still attract vigorous opposition from the losers. Inaction may also incur costs—the costs of environmental damage unchecked—and these can be enormous. It is important that these be part of the calculations, where they will weigh against the costs of action.

5.4 Ecolabelling and environmental management system certification programs