Environmental Engineering Reference
In-Depth Information
2
Thomas J. Stohlgren and Catherine S. Jarnevich
Risk assessments have long been used for the analysis of human health risks associ-
ated with chemical contaminants and other hazards (National Academy of Sciences
1983). For chemical hazards, risk assessment has been defi ned as 'A set of formal
scientifi c methods for establishing the probabilities and magnitudes of undesired
eff ects resulting from the release of chemicals. Risk assessment includes quan-
titative determination of both exposure and eff ects' (Society of Environmental
Toxicology and Chemistry 1987). Humans often were the target species of con-
cern. Assessments were typically restricted to hazard identifi cation, dose-response
assessments, exposure assessments, and human health risk characterization. h e
eff ect of the pesticide DDT on a variety of bird species is a classic example of risk
assessment (Ratcliff 1967).
Risk assessment for biological invasions is somewhat similar to those other
types of hazards. For example, evaluating chemical spills requires basic infor-
mation on where a spill occurred; exposure level and toxicity of the chemical
agent; knowledge of the physical processes involved in its rate and direction
of spread; and potential impacts to the environment, economy, and human
health relative to containment costs. However, unlike typical chemical spills,
biological invasions can have long lag times from introduction and establish-
ment to successful invasion, they reproduce, and they can spread rapidly by
physical and biological processes. We can view potentially harmful, non-native
species (i.e. species foreign to the ecosystem in which they are now found) as
biological hazards (Stohlgren and Schnase 2006). And, borrowing from the
physical sciences (Society of Environmental Toxicology and Chemistry 1987),
we can defi ne risk assessment of invasive species as 'A set of formal scientifi c
methods for establishing the probabilities and magnitudes of undesired eff ects
resulting from the introduction of non-native (or non-indigenous) biological
organisms. Risk assessment includes quantitative determination of the current
and potential abundance and distribution of the organisms and their economic,
environmental, and human-health eff ects'.
