Are Ecosystem Sustainability and Population Viability Useful Endpoints for Ecological Risk Assessment? R. A. Pastorok and J. R. Sampson, PTI Environmental Services, 15375 SE 30th Place, Bellevue, WA 98007
The role of ecological risk assessment at hazardous waste sites in natural resource management is not well defined. Recent approaches to natural resource management invoke ecosystem sustainability or population viability as a goal for environmental management actions. The concepts of ecosystem sustainability and population viability may provide a framework for defining assessment endpoints in ecological risk assessments independent of human or social values. However, the value of these concepts in defining assessment endpoints has not been established. Most ecological risk assessments do not consider sustainability or persistence explicitly through quantitative analyses. Most assessments use toxicological or "bottom-up" approaches with endpoints related to individual survival, growth, or reproduction. "Top-down" approaches often rely on a field survey of population abundances (or community structure) at a single point in time. Such surveys provide very limited insight into long-term chemical risks against a background of substantial natural variability. Consequently, ecological risk assessors need to define practical assessment endpoint and population/community models for use in predictive assessments. Quantifiable attributes of populations, communities, and physical-chemical processes that influence population viability and ecosystem sustainability should be identified for use as assessment endpoints in ecological risk assessment.