Landscape characterization studies, combined with experimental approaches, are required to 
better quantify the relative impacts of chemical stressors, habitat alterations, and the introduction 
of exotic species on wildlife populations. Associated with this effort is the need to develop and 
integrate predictive models so that the outcome of different management scenarios, based on 
chemical loading, habitat alterations, exotic species control, and other management options, can 
be quantified. 
2. Research to Define Appropriate Geographical Regions/Spatial Scales for Wildlife Risk 
Assessments. 
A significant effort is needed to define scientifically credible spatial scales for wildlife risk 
assessments. Habitat requirements for wildlife species associated with aquatic and terrestrial 
ecosystems must be established and referenced to regulatory jurisdictions to ensure coordinated 
implementation of risk-based decisions. A consensus on current or potential habitat ranges are 
needed to identify wildlife species of concern and to evaluate approaches in risk assessments that 
consider spatial population structure (EPA 2000). 
Within the WRS, three major research objectives have been defined to address these needs. The 
third objective defines the focus for the habitat alteration component of the loon project, i.e., the 
development of approaches for evaluating relative risks from chemical and non-chemical 
stressors on spatially structured wildlife populations across large areas or regions ('^geospatial 
modeling"). Research described in the loon project will address issues associated with the spatial 
and temporal heterogeneity of populations and stressors in real landscapes. This landscape 
context provides a basis for understanding and quantifying how spatio-temporally varying 
stressors influence the distribution of wildlife populations. Thus, the approaches, models, and 
methods developed within this project are designed both to assess risks from multiple stressors 
and evaluate the relative effectiveness of alternative management strategies. 
Objectives 
Specific to the goals for habitat alteration research, the relevant research objective can be 
described as the development of approaches for evaluating the relative risks from chemical and 
non-chemical stressors on spatially-structured wildlife populations across large areas or regions. 
Consistent with this objective and to address the WRS objectives described above, research 
activities within the loon demonstration project focus on the development of geospatial modeling 
methods to assess the relative impact of heterogeneously distributed stressors, including dietary 
methylmercury, habitat degradation, acidification, and human disturbance on populations of the 
common loon, which is resident to the northeastern portion of the U.S. and Canada. For this 
purpose, research activities will include the develop of methods to identify spatial relationships 
among stressors (i.e., correlations in distributions), potential interactions among stressors, and the 
relative risks among potential stressors to populations of loons at varying spatial scales. 
Scientific Approach 
Consistent with the approach described generally for habitat alteration research, there are two 
distinct research components for habitat research within the loon project. The first of these 
35 
