ABSTRACT
This chapter discusses a recent National Research Council (NRC) report as an example of a discussion of ecological risk assessment and comments on some differences and similarities between ecological risk assessment and health risk assessment. The NRC committee was motivated by the recognition that environmental problems often are ecological problems and require ecological knowledge to solve them. The committee addressed various levels of ecological organization, from populations to ecosystems. The sources of uncertainty include the complexity of natural systems, natural variability in space and time, random variation, errors of measurement, and lack of information. Ecological risk assessment is usually based on single occurrences or sources of environmental effects, but often an ecological system is subject to multiple occurrences or sources of effects. Cumulative effects are increasingly part of environmental assessment. Ecological risk assessment has adopted some ideas and procedures from human health risk assessment.
