Using landscape ecology to focus ecological risk assessment and guide risk management decision-making

Ecological risk assessment (EcoRA) generally suffers from limited application of ecological knowledge in the definition and characterization of real-world sites. Not surprisingly, most remediation decisions, which follow, have little or no relationship to the valued ecological resources of the site or the broader region. The practice has evolved to favor engineering-based mitigation strategies, which eliminate excess chemical concentrations at sites, or otherwise break exposure pathways, but which may not be ecologically beneficial. The heavy emphasis of EcoRA on toxicity threshold levels tends to focus dollars on clean up of small areas or volumes with high concentrations. Moreover, intrusive remediation technologies often render an area uninhabitable to the very species that were to be protected. Infusion of ecological knowledge into EcoRA has been difficult. Most professional ecologists choose not to venture into the messy applied fields, leaving their impressive knowledge untapped. Moreover, narrowly defined responsibilities within government circles can limit cooperation and coordination. The realization that land use activities often have greater adverse consequences to wildlife than do chemicals provides an opportunity to change attitudes and practices. We are developing procedures that incorporate landscape features into the environmental management process. Specifically, we are using an iterative approach to:

a) identify scenarios where habitat value is important in EcoRAs;

b) guide selection of appropriate assessment species,

i) keyed to wildlife distribution ranges;

ii) keyed to a database of habitat suitability models;

iii) cross-linked with the EPA exposure handbook species;

iv) referenced to wildlife distributions (e.g., breeding bird survey);

c) define data collection needs for reconnaissance-, screening-, and definitive-level characterization of habitat quality for potential assessment species;

d) generate spatially explicit descriptions of habitat quality for various assessment species; and

e) allocate exposure estimates using both habitat quality and spatial variations in chemical concentration.

These refinements in the EcoRA process are expected to improve risk estimates and provide valuable information to be used in structuring risk management options. The approach can guide the planning process so that an assessment considers the most relevant species of the area and defines the relevant parameters to be measured. In risk characterization, these data are used to calculate more realistic exposure assessments. In guiding remediation, the approach logically considers a wider range of land management options than are considered at most sites today. For example, habitat enhancement can be used to draw animals away from contaminated zones. Contaminated localities that also have poor-quality habitat may be allowed to go through a slower, less costly bioremediation process until the risk level is lowered to acceptable levels. And direct comparisons of lost resources stemming from destructive remediation options can be assessed instead of merely focusing on the lowering of contaminant concentrations. This paper presents the conceptual foundation for incorporating landscape ecology into the risk assessment process.