Evaluation of potential effects of federal land management alternatives ontrends of salmonids and their habitats in the interior Columbia River basin

Aquatic species throughout the interior Columbia River basin are at risk. E valuation of the potential effects of federal land management on aquatic ec osystems across this region is an important but challenging task. Issues in clude the size and complexity of the systems, uncertainty in important proc esses and existing states, flexibility and consistency in the analytical fr amework, and an ability to quantify results. We focused on salmonid fishes and their habitats as indicators of conditions in aquatic ecosystems and us ed Bayesian belief networks as a formal, quantitative framework to address the issues in our evaluation of land management alternatives proposed for t he interior Columbia River basin. Because empirical information is limited at the scales relevant to our analysis, an ability to combine both empirica l and more subjective information was key to the analysis. The representati on of linkages through conditional probabilities made uncertainty explicit. We constructed two general networks. One represented the influence of land scape characteristics and existing and predicted management activities on a quatic habitats. A second represented the influence of habitat, existing bi otic conditions, and for two anadromous species, ocean and migratory condit ions, on the status of six widely distributed salmonid fishes. In the long term (100 years) all three land management alternatives were expected to pr oduce positive changes in the status and distribution of the salmonids and their habitats. Trends were stronger for habitat than for the status of sal monids because of greater uncertainty in linking the fish and habitat netwo rks and constraints outside spawning and rearing habitat on federal lands i n the study area. Trends were stronger for resident salmonids than anadromo us forms because of additional effects of the migratory corridor assumed fo r the latter. Alternative S2, which approached ecosystem restoration more c onservatively, generally produced the strongest positive changes, and alter native S3, designed to promote more aggressive restoration, the weakest. Av eraged across the basin, differences among the alternatives were small. Dif ferences were greater at finer temporal and spatial scales. In the short te rm (10 years) alternative S3 was expected to lead to further degradation in some areas. By formalizing our understanding and assumptions in these netw orks, we provided a framework for exploring differences in the management a lternatives that is more quantifiable, spatially explicit, and flexible tha n previous approaches. Published by Elsevier Science B.V.