Step 4 - Analysis and Interpretation of the Risks and Threats that Influence Native Trout Populations and Associated Stream-Riparian Habitats

In step 4 (figure at right), national forest biologists analyzed risks and threats to populations and their habitats at the subwatershed level, identifying those risks and threats most urgently to be considered and addressed by management. Influence diagrams, or cause-and-effect diagrams (step 4 (A, B)) were used to display the analysis thought process. These unambiguous diagrams helped biologists, managers, scientists, and interested publics visualize, discuss, and review all the factors and pathways that potentially impacted population and watershed condition. Forest biologists created an influence diagram for risks and threats to trout population persistence (step 4 (A)) and a separate influence diagram for risks and threats to habitat (step 4 (B)). The step 4 (A) diagram included elements such as migration barriers and presence of invasive species. To predict the future status of cutthroat trout populations in the subbasin, both influence diagrams were incorporated into a probabilistic network (in this case, a Bayesian belief network (Lee and Rieman 1997, Rieman and others 2001)) and run under different management scenarios. For example, the biologists found that if riparian road densities were high in a subwatershed where invasive species (brook trout) were present, the future population status for cutthroat was depressed. In this way, the Forests could test different management alternatives and predict their impacts on trout population status at both the subwatershed and the subbasin scale (step 4(C)).

The Framework facilitates risks and threats analysis by providing hyperlinks to potential analysis tools and current conservation literature. For example, links connect the user to the trout extinction risk matrix (Rieman and others 1993), effects of Federal land management alternatives on population trends (Rieman and others 2001), population viability assessment of salmonids using probabilistic networks (Lee and Rieman 1997), and conservation assessments for various fish species.

For Forest Plan revision, Step 4 risks and threats analyses can be incorporated into the CER and thereafter provide background information for crafting the desired conditions and objective components of the plan. Step 4 is useful in the planning process in that it provides a transparent view of the spatial and temporal interaction of biological, physical, chemical, and social processes at work in the planning area. Implications of these interactions are used as the basis for development of the conservation and restoration strategies outlined in the next step of the Framework.