You are here:
Establishing a Quantitative Definition of Reference for the USEPA’s National Wetland Condition Assessment
Citation:
Kentula, M., A. Herlihy, T. Magee, G. Lomnicky, A. Nahlik, AND G. Serenbetz. Establishing a Quantitative Definition of Reference for the USEPA’s National Wetland Condition Assessment. Annual Meeting of the Society of Wetland Scientists, Denver, Colorado, May 29 - June 01, 2018.
Impact/Purpose:
This presentation will present the process used to select reference sites for the first-ever, USEPA, National Wetland Condition Assessment (NWCA). The audience of the Society of Wetland Scientist’s annual meeting is an ideal forum to showcase these methods and to obtain valuable technical input. This interaction will likely increase interest in the USEPA's National Aquatic Resource Surveys and contribute to wetland science by increasing the number of scientists who will read the NWCA reports and use the data from the survey in additional analysis and research efforts.
Description:
A major challenge when conducting an assessment of natural resources is determining the appropriate standard (i.e., reference) against which to judge ecological condition. The process is complicated by the (1) tremendous natural environmental heterogeneity that exists within a large landscape and (2) variability of wetland quality across and within regions. We describe the process to identify reference sites for the US Environmental Protection Agency’s (USEPA) 2011 National Wetland Condition Assessment (NWCA). For the NWCA, reference sites are those with the best available ecological condition given the current state of the landscape, i.e., least disturbed sites. NWCA 2011 employed a probability design to sample 1138 sites across the contiguous US to make a quantitative assessment of wetland condition. Vegetation data were used to define ten combinations of ecoregions and wetland types (hereafter reporting groups) that minimized within-group natural variability. For each reporting group, all sites were arrayed along a gradient defined by ten measures of disturbance based on land use, hydrologic modifications, soil heavy metals, and alien plants. Disturbance thresholds of least (i.e., reference), intermediate, and most disturbed were established. Ultimately 277 least disturbed reference sites were identified of which 170 qualified as minimally disturbed (i.e., none of the disturbance measures were present). Amount and type of disturbance found in reference sites varied by region and wetland type. An effort to handpick reference sites prior to sampling had a 52% failure rate when evaluated against the quantitative definition developed for reference for the appropriate reporting group. The NWCA provides a unique opportunity to improve our conceptual and technical understanding of how to apply a reference approach to assess the wetland resource across the conterminous US. Moreover, the number of quantitatively defined reference sites will grow with each subsequent NWCA. This abstract does not necessarily reflect USEPA policy.