THE VALUE OF ECOLOGICAL RISK ASSESSMENT

CRAFT's approach to risk assessment is consistent with the process elaborated by the U.S. Environmental Protection Agency in its 1998 Guidelines for Ecological Risk Assessment. The discussion on this page has been adapted from this document, one that describes the value of ecological risk assessment thusly:

"The wide use and important advantages of ecological risk assessments do not mean they are the sole determinants of management decisions; risk managers consider many factors. Legal mandates and political, social, and economic considerations may lead risk managers to make decisions that are more or less protective. Reducing risk to the lowest level may be too expensive or not technically feasible. Thus, although ecological risk assessments provide critical information to risk managers, they are only part of the environmental decision-making process" (US EPA, 1998, p. 26848).

The guidelines focus on stressors and adverse effects that have been generated or influenced by human activity. A careful definition of adversity is important, because

"...a stressor may cause adverse effects on one ecosystem component but be neutral or even beneficial to other components. Changes often considered undesirable are those that alter important structural or functional characteristics or components of ecosystems. An evaluation of adversity may include a consideration of the type, intensity, and scale of the effect as well as the potential for recovery. The acceptability of adverse effects is determined by risk managers. Although intended to evaluate adverse effects, the ecological risk assessment process can be adapted to predict beneficial changes or risk from natural events" (US EPA, 1998, p. 26848).

In CRAFT, the notion of "acceptability of adverse effects" described above has been quantified as acceptable limits or threshold values. These numbers figure prominently in the overall process of defining the values and preferences of planning teams, decision makers, and other stakeholders.

As in ecological risk assessment, descriptions of the probability of adverse effects in CRAFT - one of the results of the Modeling Effects stage - can range from qualitative judgments to quantitative probabilities (see A Primer on Risk & Uncertainty). CRAFT and the ecological risk assessment process are consistent in the understanding that "[i]t is better to convey conclusions (and associated uncertainties) qualitatively than to ignore them because they are not easily understood or estimated" (US EPA, 1998, p. 26848). In the land-use planning under NEPA, accounting for uncertainty is particularly crucial as teams must account for future as well as past consequences of human activities, (i.e., cumulative effects). The EPA states the case this way:

"Ecological risk assessments can be used to predict the likelihood of future adverse effects (prospective) or evaluate the likelihood that effects are caused by past exposure to stressors (retrospective). In many cases, both approaches are included in a single risk assessment. For example, a retrospective risk assessment designed to evaluate the cause for amphibian population declines may also be used to predict the effects of future management actions. Combined retrospective and prospective risk assessments are typical in situations where ecosystems have a history of previous impacts and the potential for future effects from multiple chemical, physical, or biological stressors" (US EPA, 1998, p. 26848).

Thus, the value of risk assessment to the overall structure of CRAFT lies in the prospect that this uncertainty can and should be treated as vital information for decision makers. While this approach can complicate analysis, the losses are more than offset by gains which include more defensible decisions and a clear portrayal of risks and tradeoffs among alternative management actions.

THE PROCESS

CRAFT encompasses the two main elements of an ecological risk assessment, (1) characterization of effects, and (2) characterization of exposure. CRAFT does not, however, characterize effects and exposure in distinct phases of risk modeling. Instead, both effects and exposure are addressed together in a single risk model based on Bayesian belief networks. The development of a risk model provides an integrated environment for problem formulation, analysis, and risk characterization stages of ecological risk assessment:

1. Problem Formulation

According to the EPA, in the problem formulation stage of a ecological risk assessment

the purpose for the assessment is articulated, the problem is defined, and a plan for analyzing and characterizing risk is determined. Initial work in problem formulation includes the integration of available information on sources, stressors, effects, and ecosystem and receptor characteristics. From this information two products are generated: Assessment endpoints and conceptual models. Either product may be generated first (the order depends on the type of risk assessment), but both are needed to complete an analysis plan, the final product of problem formulation (US EPA, 1998, p. 26852).

In CRAFT, the problem formulation phase of an ecological risk assessment corresponds to two of CRAFT's four stages: Specifying Objectives and Designing Alternatives.

2. Analysis

The analysis stage of an ecological risk assessment is driven by the products of the first stage, Problem Formulation. During this stage,

data are evaluated to determine how exposure to stressors is likely to occur (characterization of exposure) and, given this exposure, the potential and type of ecological effects that can be expected (characterization of ecological effects). The first step in analysis is to determine the strengths and limitations of data on exposure, effects, and ecosystem and receptor characteristics. Data are then analyzed to characterize the nature of potential or actual exposure and the ecological responses under the circumstances defined in the conceptual model(s). The products from these analyses are two profiles, one for exposure and one for stressor response. These products provide the basis for risk characterization (US EPA, 1998, p. 26852).

In CRAFT, the equivalent of exposure and stressor profiles are developed and integrated within the risk model as it evolves from a qualitative conceptual model to a quantitative Bayesian belief network in Specifying Objectives and Modeling Effects. In a typical ecological risk assessment, however, this integration of exposure and effects takes place in the next phase, Risk Characterization.

3. Risk Characterization

In ecological risk assessment, risk characterization is the stage where assumptions are summarized, scientific uncertainties described, and the overall strengths and limitations of analyses are portrayed. The final product includes an "interpretation of ecological adversity and descriptions of uncertainty and lines of evidence" (US EPA, 1998, p. 26853). In CRAFT, risk characterization is a product of both Modeling Effects and the final stage, Synthesis.

4. Activities in Support of Ecological Risk Assessment

Following risk characterization, the results of a risk assessment are formally communicated by risk assessors to risk managers, who in turn communicate the results to stakeholders and other interested parties. In ecological risk assessment, risk communication - like risk assessment and risk management - is viewed as a distinct activity. Whereas risk assessment estimates the the probability of adverse effects, risk management involves selecting of a course of action in response to a specific risk. Such decisions may be based on social, legal, political, or economic factors additional to the results of a risk assessment (US EPA, 1998).

Other activities not generally viewed as part of risk assessment include data acquisition and monitoring. Data from monitoring may provide important input to all phases of a risk assessment, and may be used to evaluate a risk assessment's predictions. In natural resource management organizations, communication to decision makers and stakeholders, data acquisition and monitoring are integral parts of the planning process and day-to-day business. CRAFT reflects this organizational reality by providing appropriately timed guidance for these important activities that support the process of risk assessment.

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Last updated: July 14, 2005