Specific protocols for ecological risk characterization will likely be developed only through practice.
Application to the Case Studies
The ecotoxicological case studies were sufficiently similar that common lessons could be drawn from them. The population-management case studies were diverse and are discussed separately.
Lessons learned from the ecotoxicological case studies regarding risk characterization are summarized as follows:
There was no attempt to carry out a risk characterization. None of these case studies included an actual risk assessment, and none contained attempts to convey the science in a risk perspective.
Ecotoxicological assessments are as amenable to the development of a risk characterization as health risk assessments.
Case study end points were not well characterized in general. Sentinel species were used in most cases. End points need to be put into perspective, so that the scope of the assessment and the relevance of measured versus predicted responses can be appreciated.
The quality of the data was not made explicit in the case studies.
Any inferences drawn on the basis of extrapolation across species or levels of organizations need to be carefully articulated, and uncertainties in them need to be explicit.
Each case needs a statement as to how the acquired data will affect future assessment. Not all data gaps represent data needs for ecological assessment.
Exposure-based partitioning was suggested as a means to put the scope of case assessments into perspective. It will help to determine whether a defined case represents a major or a minor route of environmental contamination or exposure.
The Georges Bank fishery study is the nearest of the population-management case studies to the conventional scheme of integrating exposure estimates (harvest) with exposure-response (fish population and community dynamics) models. Good features of this case study include development of alternative lines of evidence, acknowledgment of uncertainty,
and recommendations to resource managers for management experiments. The major unresolved problem in risk characterization is communication with managers. It was clear, both from the case study paper and from the discussion after the case study presentation, that fishery managers are resistant to ecological risk as a decision-driver, have a short time horizon, and have difficulty in appreciating the assumptions that underlie alternative models.
As described in the case study, the northern spotted owl assessment was not formulated in terms of risks, and the decision apparently was not based on analysis of the relationship of exposure (to logging) to effects (population reduction). Literal application of the risk characterization scheme developed by the group would require that spotted owl population characteristics be quantitatively related to habitat characteristics. Decisions concerning spotted owl management appear to have been based principally on qualitative habitat evaluation. Demographic models, such as the one presented in the case study, have been used principally as supporting lines of evidence. Uncertainty, especially concerning the link between spotted owl population dynamics and distribution patterns of old-growth forest, has not been systematically addressed.
The species introduction case study is not a risk assessment, as defined for this workshop. There is no scale of exposure (the species is successfully introduced or not), and the effects are qualitative (the species is effective or not; it becomes a pest or not). The risk assessment is intuitive and based on expertise, rather than on explicit assumptions and models. Because the regulatory approach used by USDA is not open, it is not subject to review and scrutiny, and no attempts are made to communicate the results beyond regulatory decision-makers. There is no acknowledgment of uncertainty, even though the number of alternative hosts tested is small relative to the diversity of potentially exposed species. The case study reminded the session participants of the space-shuttle program, which relied on intuitive risk assessments until catastrophic failure occurred. To outsiders, it is not clear whether the success of USDA's species introduction program in avoiding ecological catastrophes is due to luck or to the rigor of the evaluation program.