Regional assessments of stream ecological condition: scientific challenges associated with the USA’s national Wadeable Stream Assessment

Abstract

Regional assessments describe the status of an entire ecological resource within a region of interest. Considering the global scope of landscape, atmospheric, and waterway alterations, such assessments are critically needed to guide environmental policies that can ensure sustainable management of the planet’s natural resources (Millenium Ecosystem Assessment 2005, Carpenter et al. 2006). Objective regional assessments depend on the application of sound and credible science including sampling designs that allow accurate extrapolation to the whole resource population and indicators that are quantitative, ecologically interpretable, and regionally comparable. In 2006, in response to increasing requests for data describing the quality of surface waters and other ecosystems in the US (e.g., USGAO 1981, 1988, H. John Heinz Center for Science, Economics and the Environment 2002, 2008), the US Environmental Protection Agency and its state and tribal collaborators published the first nationwide assessment of stream ecosystems in the US (USEPA 2006). Producing that assessment required that research teams tasked with designing and implementing the assessment address several technical challenges. Some of those challenges were overcome, others remain in need of additional attention, and some new challenges emerged after the assessment. In this special issue of J-NABS, we have compiled a series of papers that describe some of the major scientific challenges that were encountered during the national Wadeable Streams Assessment (WSA) and some of the lessons learned subsequent to the assessment. Our goal in producing this series was to use the WSA as a case study to illustrate the variety of scientific challenges that can arise when planning and implementing regional assessments, describe how those challenges were addressed for the WSA, describe some important spin-offs that emerged as a consequence of the WSA, and identify remaining knowledge or data gaps that will require attention in future regional assessments. We hope these papers will stimulate thinking about how to improve future assessments in the US and elsewhere. The series consists of 4 sets of papers: 1) policy and overview, 2) WSA-specific case studies, 3) extensions that build on or augment initial WSA results, and 4) an invitation to other researchers to use the WSA data to test other ideas regarding the structure and function of stream ecosystems. The series opens with a paper by Shapiro et al. (2008) that describes the policy background that led to the WSA. Paulsen et al. (2008) then provide an overview of the major findings that emerged from the WSA. The 2 set of papers includes papers that cover issues of survey design and indicator development and application. Olsen and Peck (2008) describe 1 E-mail addresses: chuck.hawkins@usu.edu 2 paulsen.steve@epa.gov 3 vansickle.john@epa.gov 4 yuan.lester@epa.gov