Density Dependence in Ecological Risk Assessment
This chapter summarizes the existing state of knowledge concerning the quantification of density dependence for ecological risk assessment. Density dependence is a fundamental concept in population biology, and it seems clear that density dependence in some form is exhibited by most animal species. Density dependence plays important roles in conservation biology, pest management, and harvesting. Sustainable exploitation of populations relies completely on the capacity for density-dependent compensation. The strength of a population’s response to a change in density may be particularly relevant to risk assessment. A simple harvest model shows that a population with Allee effect in the percapita recruitment rate may in theory display multiple equilibria, when it is subject to density-dependent toxicant impacts. The density-toxicant interactions discussed assume that the toxicant has direct and lethal effects. A more flexible way of exploring nonlinear structures in density dependence is by “generalized additive modeling”.