Scientific Uncertainty and Risk Assessment

One of the commonly-mentioned approaches for policy analysis is "risk assessment." In brief, there is often a recommendation in state and federal governments that proposed regulations and policies should be evaluated using risk assessment before approval. This has sparked a good deal of concern and suspicion - "What could those shady politicians be up to?"- many people might wonder. Some people worry that a requirement for risk assessment is just a clever way to reduce environmental protection and to slow down regulatory efforts in seemingly endless scientific analysis and review.

Perhaps so. But, I see a lesson and an opportunity in this. One thing that we gain from risk assessment is an appreciation of the magnitude of the uncertainty in the science surrounding environmental management and decision making. It is distressing that essentially all decisions affecting environmental management reflect incomplete or inaccurate science. For example, it is unfortunately true that scientists cannot predict with great confidence the effect of land use changes on water quality. Yet, we generally rely on those predictions to guide TMDL decisions. What should we do? Forget the scientific input because it's not terribly good?

No. The lesson from risk assessment is that we should demand from scientists an estimate of the goodness of their science. This means that we must ask scientists questions such as "How good is that prediction?" or request that scientists "Give us a range of numbers that reflects the scientific uncertainty." Then, as citizens or as decision makers, we need to use this information on scientific uncertainty to work toward improved environmental management. How do we do that?

Well, here's an example from everyday life. All of us have made decisions on outdoor activities in consideration of the forecast for rain. In deciding whether to hold or postpone an outdoor activity, we typically seek (scientific) information on such things as the probability (reflecting uncertainty) of rain. Further, it is not uncommon  to hear the weather forecast on the evening news, but still defer a final decision on the activity until an updated weather prediction in the morning (in other words, get more sample information).

Beyond consideration of the scientific assessment in the weather forecast, we also think about how important the activity is to us. Do we really want to participate in the activity, such that a little rain will not greatly reduce our enjoyment? Or, is the activity of only limited value, such that a small probability of rain may be enough so that we choose not participate?

Every day, we make decisions based on an interplay, or mix, of uncertainty in an event (e.g., rain) and value (enjoyment) of an activity. We are used to weighing these considerations in our minds and deciding. These same considerations--getting new information on the weather (which is analogous to supporting new scientific research, as in adaptive management), and deciding how valuable the activity is to us (which is what we determine through cost/benefit analysis)--are key features of risk assessment. So let us move from our informal, everyday risk assessment to formal, scientific risk assessment, and identify the lesson and the opportunity as they relate to environmental management.

To me, the lesson in risk assessment is to recognize that the science in support of environmental management is usually uncertain, and sometimes highly uncertain. But the opportunity that is provided by risk assessment should result in improved decision making. To accomplish this, we must first require scientists to quantify or estimate the scientific uncertainty. Then we must require our decision makers to use the estimate of uncertainty to properly weigh the scientific information (not unlike what we do in our informal, everyday risk assessment). In the long run, this should improve environmental management decisions by making better use of the available information.