Abstract
The US Environmental Protection Agency (US EPA) initiated planning in 2007 and conducted field work in 2011 for the first National Wetland Condition Assessment (NWCA) as part of the National Aquatic Resource Surveys (NARS). It complements the US Fish and Wildlife Service (USFWS) National Wetland Status and Trends (S&T) program that estimates wetland acres nationally. The NWCA used a stratified, unequal probability survey design based on wetland information from S&T plots to select 900 sites for the conterminous 48 states. Based on site evaluation information, the NWCA estimates that there are 94.9 (± 6.20) million acres of wetlands in the NWCA target wetland population (reported in acres to be consistent with S&T). Not all of the estimated target population acres could be sampled due to accessibility and field issues. Based on the sites that could be sampled, the sampled population for the NWCA is estimated to be 62.2 (± 5.28) million acres of wetland area. Landowner denial for access was the main reason (24.7% ± 3.5%) for the sampled population being smaller than the target population, and physical inaccessibility was the second reason (6.8% ± 2.1%). The NWCA 2011 survey design was successful in enabling a national survey for wetland condition to be conducted and coordinated with the USFWS S&T survey of wetland extent. The NWCA 2016 survey design has been modified to address sample frame issues resulting from the difference in S&T focusing only on national estimates and NWCA focusing on national and regional estimates.
Highlights
In 2007, the US Environmental Protection Agency (US EPA) initiated planning for the National Wetland Condition Assessment (NWCA) as part of the National Aquatic Resource Surveys (NARS)
The NWCA is the first national assessment of wetland condition conducted within the USA and complements the US Fish and Wildlife Service (USFWS) National Wetland Status and Trends (S&T) program, which has provided national estimates on wetland area over time since its inception in 1974 (Frayer et al 1983; Dahl et al 1991; Dahl 1990, 2000, 2006, 2011; Dahl and Bergeson 2009)
This paper describes the 2011 NWCA probability survey design, including its implementation and statistical estimation procedures
Summary
In 2007, the US Environmental Protection Agency (US EPA) initiated planning for the National Wetland Condition Assessment (NWCA) as part of the National Aquatic Resource Surveys (NARS). The NWCA conducted field work in 2011 and was the fourth aquatic resource surveyed by NARS. It was preceded by coastal water, lake and reservoir, and river and stream assessments conducted in 2007 to 2010. In the early 1990s, the US EPA’s Environmental Monitoring and Assessment Program (EMAP) conducted research on approaches to monitoring wetland condition (Leibowitz et al 1991). Their goal was Bto provide a quantitative assessment of the
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