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(90-01) Appropriate landscape scales for ecological risk assessments. Landis, Wayne*,1, 1 Institute of Environmental Toxicology and Chemistry, Bellingham, WA ABSTRACT- The correct scale for conducting an ecological risk assessment of open systems is an important consideration. Regional scale risk assessments for watersheds in Pennsylvania, Oregon, and Washington, plus work on a marine site have clearly demonstrated the importance of spatial extent in understanding risks to specific populations. In the case of the Codorus Creek watershed in South-Central Pennsylvania, brown trout habitat is limited to a small section of the stream kept cool by a hypolimnetic discharge from a reservoir. Warm water habitat is re-established in the creek by the warm discharge of a paper mill, The available habitat for warm water fish is substantially greater, includes the rest of the watershed that has inputs from agricultural run-off, and urbanization and has been modified for flood control. A risk assessment of the salmonids of the Willamette and McKenzie watersheds in western Oregon involves a variety of scales. Rainbow trout are limited in migration and are localized within certain sections of the watershed. The anadromous species migrate to the ocean and return, and the proper scale includes the main channel and spawning sites within the watershed. Evaluation of a free ranging coastal fish species involves other considerations of scale. The Cherry Point Pacific Herring of the Straits of Georgia spawn within a limited coastal region of northwest Washington, but are also a part of a large metapopulation that extends into Canadian waters. Understanding risks to the Cherry Point spawning stock must include an understanding of large-scale climatic impacts along the continental shelf of the region as well as anthropogenic impacts at a local and regional scale. The appropriate scale in each case is determined by the life-history and habitat requirements of the endpoint, not necessarily the size of the initial study area or the extent of contamination. Key words: landscape, scale, multiple stressors |
