Forecasting Avian Responses to Elwha River Restoration

Gelarden, Carly

The majority of the world's rivers have been frragmented and degraded by dams. Many river restoration efforts now include dam removal, but with limited knowledge about post-removal effects. Few dam removals have received comprehensive ecological study, and fewer still have considered effects on associated terrestrial components. The largest dam removal project to date will occur on the Elwha River and will provide the first opportunity to evaluate ecological responses to large dam removals. I present the initial three stages in a long-term research program to determine avian responses to pending Elwha dam removals: (1) pre-removal inventory, (2) modeling species densities and distributions, and (3) forecasting species responses to forest restoration after dam removals. I completed a pre-removal avian inventory during the 2006 breeding season using the variable circular plot protocol implemented throughout National Parks in the North Coast and Cascades Network. For 22 of the 42 detected species, I determined point-specific differences in detectability. I modeled ten species' abundance using habitat variables at three spatial scales: local habitat structure, habitat patch characteristics, and landscape patterns. I used Akaike's Information Criterion to select the best models from the candidate set for each species. I used multi-model inference to determine the relative importance of each predictor variable as well and each spatial scale. For most species, abundance patterns were explained best by habitat variables at the local scale. I forecasted avian responses to two scenarios for forest restoration in the Lake Mills reservoir bed: (1) forest succession without conifers, and (2) succession to mixed forests via conifer inter-planting. The latter scenario represents Olympic National Park's revegetation plan. By most measures, forecasted responses are more rapid under the second scenario. Forecast results suggest that species associated with deciduous forests and edge habitat will colonize newly restored habitats rapidly following dam removal, but conifer and interior forest specialists may not respond markedly for more than a century. Substantial restoraiton of the Elwha avifauna in areas most impacted ty the dams will require more time than the dams themselves have been in place. This theme is familiar to forest restoration in the Pacific Northwest: anthropogenic impacts to the forest system occur rapidly, but restoration from those impacts will be comparatively slow.

Forecasting Avian Responses to Elwha River Restoration

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