Assessing Ecological Risks at a Variety of Scales. W. G. Landis, Western Washington University
Since 1997 the relative risk method developed by Wiegers and Landis has been used in seven studies to generate risk hypothesis at a variety of scales. These scales have ranged from an urban watershed a few square kilometers in size, to Brazilian rainforest and large coastal marine areas. The methodology is inherently spatially explicit and uses non-dimensional ranks to allow the combining of various stressors, habitats and impacts to allow cumulative estimates of relative risk. The patterns of risk can be mapped within a landscape and then tested using a variety of techniques. There are ten fundamental steps in all of our assessments: 1) list the important management goals for the region and where they are; 2) make a map that includes potential sources and habitats relevant to the management goals; 3) break the map into regions based upon a combination of management goals, sources and habitats; 4) make a conceptual model that ties the stressors to the receptors and to the assessment endpoints; 5) develop a ranking scheme to allow the calculation of relative risk to the assessment endpoints; 6) calculate the relative risks; 7) evaluate uncertainty and sensitivity analysis of the relative rankings; 8) generate testable hypotheses for future investigations to confirm the risk rankings; 9) test the hypotheses with particular attention to landscape patterns; and 10) communicate the results in a fashion that portrays the relative risks and uncertainty in a response to the management goals. The constant characteristics of these assessments over such a large range of scales have been 1) a generation of patterns of risk in the study area, 2) a clustering of stressors within the landscape, 3) the irrelevance of reference sites, 4) the importance of spatial and temporal scale in assessing risks, and 5) the lack of relevant environmental data placed in a spatial context.
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