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Survey Design to Assess Condition of Wetlands in the United States
Citation:
Olsen, Tony, Tom Kincaid, M. Kentula, AND M. Weber. Survey Design to Assess Condition of Wetlands in the United States. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 191:268, (2019). https://doi.org/10.1007/s10661-019-7322-6
Impact/Purpose:
The 2011 National Wetland Condition Assessment is the first national assessment of wetland condition for the contiguous United States. This paper describes the survey design, the sample frame, the statistical analysis procedures and provides estimates of the wetland extent. This information on wetland extent provides information on the quality of the sample frame (i.e., how well it matches the definition of wetlands used in NWCA) and the success in sampling wetlands that meet the definition. This paper is part of a special issue on the NWCA 2011 that covers the research that was necessary to complete the NWCA 2011. The work is part of SSWR 3.01A and is an extra product for that National Aquatic Resource Surveys task.
Description:
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 (USFWS) Service 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 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.
