ABSTRACT
Ecological risk assessments are conducted in a manner analogous to human health risk assessments: Hazards are identified, exposure and effects are analyzed, and risk is characterized. However, ecological risk assessments are generally more complex than human health risk assessments. The reader will recall that the discipline of risk assessment has borrowed the term receptor from biochemistry and applied it to any population of organisms or any ecosystem that is at risk from one or more chemical, physical, or biological stressor. Human health risk assessments by definition address a single class of receptors-human populations-and they consider only those stressors that directly affect human health, e.g., toxic chemicals and microbial pathogens. By contrast, ecological risk assessments may be performed on any of a host of receptors, such as animal or plant populations, communities (assemblages of populations), or whole ecosystems. In addition to chemical stressors, ecological risk assessments consider physical stressors, for example, dams that impede salmon spawning and deforestation that results in fragmentation and loss of bird habitat; they also address biological stressors such as invasive plant species that crowd out native vegetation.
