Environmental decision-making and the precautionary principle: what does this principle mean in environmental sampling practice?

Increasingly, environmental decision-making is scrutinised with respect to a precautionary principle. This principle asserts that where uncertainty and doubt make it impossible to be sure about a correct decision, any errors should favour the long-term sustainability of the environment. Although there are problems in practical adherence to this principle, it has particular meaning and value for quantitative, ecological aspects of environmental sampling and monitoring. When probabilistic (or statistical) interpretations of data are made, there are two potential errors: Type I, or rejecting a null hypothesis when it is true and Type II, or retaining a null hypothesis when it is wrong. In environmental terms, these can often be translated as Type I error occurring if it is claimed that there is an environmental impact when there is none. A Type II error would represent failing to detect an impact even though one has occurred. Most ecological and environmental work is designed to keep the possibility of Type I error small (and by convention at about one in twenty). Usually, there is little or no concern about Type II errors. The precautionary principle. however, dictates that Type II errors are a serious problem for environmental management-and much more so than Type I errors. Thus, not detecting impacts (Type II) is not precautionary. This paper summarizes the relevant features of environmental monitoring and sampling that decrease the chance of Type II error (and therefore increase the ‘power’ of a sampling program to detect impacts). Better consideration of these issues in the design of sampling would greatly increase adherence to the precautionary principle and would enhance the prospects of sustainable environmental decision-making. Interpreting precautionary principles in terms of environmental sampling and measurement would increase the need (and potentially the capacity) to define possible environmental disturbances and responses to them in more quantitative and less vague terms.