Ecological risk assessment is a procedure for evaluating the likelihood that adverse ecological effects are occurring, or may occur, in ecosystems as a result of one or more human activities. These activities may include the alteration and destruction of wetlands and other habitats, the introduction of herbicides, pesticides, and other toxic materials into the environment, oil spills, or the cleanup of contaminated hazardous waste sites. Ecological risk assessments consider many aspects of an ecosystem, both the biotic plants and animals and the abiotic water, soils, and other elements. Ecosystems can be as small as a pond or stretch of a river or as large as thousands of square miles or lengthy coastlines in which communities exist.

Although closely related to human health risk assessment, ecological risk assessment is not only a newer discipline but also uses different procedures, terminology, and concepts. Both human health...