Uncertainty in environmental decision-making : effects of defined or undefined guidance in the decision process

Abstract: Decision-making in environmental issues often includes uncertainty in the input data and the resulting uncertainty when the data is used. Some spatial decisions are however taken without any formal analysis, meaning that the decision-makers have a mental map and preconceived notions about the decision options before the final decision actually is taken. An example of such decision situation is siting of new landfills, where there is no standard method to aid in the decision-making process today. In other decision situations, the methods and criteria may be well developed. A commonly used method for investigation contaminated sites in Sweden is called "MIFO"- Method of Surveying Contaminated Sites. In MIFO investigations start at a superficial level and after each phase, efforts are focused further on the brownfields with highest priority. A strict model has advantages as resources are prioritized at the most polluted sites. But having a static model with strict guidance also leads to problems as the sampling approach suggested by the model is not optimally adapted to individual sites. The risk is that contamination is overestimated or underestimated, leading to unexpected costs as well as waste of resources in a remediation situation. Variability of the data, uncertainty in the data quality and the consequences in having no versus strict guidance in a decision situation are discussed in two cases; a regional landfill siting project, and a local investigation of a contaminated site. Future research involves how to include uncertainty modelling as a standard in all environmental decision-making processes. Tools are needed to aid decision-makers in expressing the maximum accepted uncertainty in the outcome. Guidance for selecting and weighing of criteria in decision- situations must be developed, as well as models that consider the case specific demands and conditions.