Designing impact assessments for evaluating ecological effects of agricultural conservation practices on streams

Authors: Smiley, Peter - Rocky; Shields Jr, Fletcher; Knight, Scott

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2009
Publication Date: 5/15/2009
Citation: Smiley, P.C., Shields Jr, F.D., Knight, S.S. 2009. Designing impact assessments for evaluating ecological effects of agricultural conservation practices on streams. Journal of the American Water Resources Association. 45:867-878.

Interpretive Summary: Conservation practices are implemented within agricultural watersheds to reduce the impacts of agricultural production. Yet, information on the ecological impacts of conservation practices is limited because these practices are frequently implemented without evaluating their impacts. Additionally, there is limited guidance available for those interested in designing ecological assessments, despite the availability of numerous sampling protocols developed for monitoring streams. Monitoring protocols are not appropriate for scientific evaluations because of the differences in research questions and spatio-temporal scales between monitoring and scientific evaluations. We developed a framework for designing scientific evaluations of ecological responses to conservation practices to promote ecological research within ARS CEAP Watershed Assessment Study. Our framework includes six guiding principles: 1) develop the hypothesis first; 2) use replicated experimental designs having controls and treatments; 3) assess the habitat and biological characteristics; 4) select quantitative and repeatable habitat sampling methods; 5) use multiple sampling techniques for collecting aquatic organisms; and 6) standardize sampling efforts for aquatic organisms. Application of our recommendations will result in scientific evaluations that are hypothesis-driven and incorporate quantitative methods for the measurement of abiotic and biotic attributes. Our guidelines will provide guidance for others investigating the influence of conservation practices and other habitat alterations on streams. Additionally, our guidelines should facilitate cross-disciplinary assessments of conservation practices because it highlights for soil scientists, engineers, hydrologists, and geomorphologists the framework used by many ecologists for evaluating the impacts of habitat alterations on streams.

Technical Abstract: Conservation practices are regularly implemented within agricultural watersheds throughout the United States without evaluating their ecological impacts. Scientific evaluations documenting how habitat and aquatic biota within streams respond to these practices are needed for evaluating the effects of conservation practices. Numerous sampling protocols have been developed for monitoring streams. However, protocols designed for monitoring studies are not appropriate for scientific evaluations. We developed a framework for designing scientific evaluations of ecological responses to conservation practices. Our framework includes six principles: 1) develop the hypothesis first; 2) use replicated experimental designs having controls and treatments; 3) assess the habitat and biological characteristics; 4) select quantitative and repeatable habitat sampling methods; 5) use multiple sampling techniques for collecting aquatic organisms; and 6) standardize sampling efforts for aquatic organisms. Application of our recommendations will result in scientific evaluations that are hypothesis-driven and incorporate quantitative methods for the measurement of abiotic and biotic attributes.