Citation:

Kentula, M. Appilications of National Wetland Condition Assessment Data to Wetland Protection and Management. Association of State Wetland Managers State/Tribal/Federal Coordination Meeting, Shepherdstown, WV, March 28 - 31, 2016.

Impact/Purpose:

The first National Wetland Condition Assessment (NWCA) was completed in 2011 and the results will be released to the public in 2016. A team of scientists from ORD played a major role in designing the survey, analyzing the data, and reporting on the results of the assessment in cooperation with the Office of Water. The analysis team also developed quantitative national and regional definitions of reference in terms of least disturbed condition. This presentation provides a summary of the major results, examples of their utility to resource management and implications to wetland policy. About 50% of the wetland area nationally was found to be in good biological condition while about 30% was in poor condition. The stressors with the greatest areal extent nationally were vegetation removal, hardening (e.g., roads, paths, extreme soil compaction), and ditching. A relative risk analysis indicated a strong relationship between high levels of nearly all the stressors measured (i.e., vegetation removal, hardening, ditching, damming, filling/erosion, and vegetation replacement) and poor biological condition. These results can be used by wetland managers as a context for evaluating the results of smaller scale assessments, to develop management approaches to address stressors tied to poor condition, and to prioritize effort based on risk. In terms of the national No Net Loss Policy, the 2011 NWCA results set a benchmark against which trends in wetland quality can be quantified and the effects of wetland protection and management evaluated with each successive survey beginning in 2016. This research also contributes to work being done under SSWR task 3.01A, subtask 1.1.

Description:

The first National Wetland Condition Assessment (NWCA) was conducted in 2011 by the US Environmental Protection Agency (USEPA) and its federal and state partners, using a survey design allowing extrapolation of results to national and regional scales. Vegetation, algae, soil, water chemistry, and hydrologic data were collected at each of 1138 locations across the contiguous US. Ecological condition was assessed in relation to a disturbance gradient anchored by least (reference) and most disturbed sites and identified using chemical, physical, and biological disturbance indices based on site-level data. A vegetation multimetric index (VMMI) was used as the indicator of condition. Potential stressors to condition were incorporated into indices of hydrologic alteration, physical alteration and a soil heavy metals, and a nonnative plant indicator. The indices were used to quantify national and regional stressor extent, and their associated relative and attributable risk. All 1138 sites sampled were placed along a quantitatively defined disturbance gradient customized by the ecoregions used in NWCA reporting. The characteristics of the 277 sites at the end of the gradient identified as least disturbed were considered reference condition. The pool of reference sites will be increased with future assessments using the definition of reference set in 2011 and can serve as a benchmark for management decisions and restoration. Approximately 48±6% of the national wetland area was found to be in good condition and 32±6% in poor condition as defined by the VMMI. The fair condition category is the smallest by percent area and total area nationally, in two of four regions, and by wetland type. A possible explanation of this pattern is that, in general, we are doing a good job of protecting the best wetlands, while it’s harder to do the same for wetlands that are degraded to some degree. The extent of nonnative plants is measured by the nonnative plant stressor indicator. Nationwide, more that 60% of the wetland area has low stressor levels related to non-native species, while 20% had high or very high levels. Approximately 11% of wetland area in the Coastal Plains and Eastern Mountains and Upper Midwest aggregated ecoregions had high or very high stressor levels for nonnative plants; whereas the Interior Plains (46%) and West (72%) aggregated ecoregions appear to be much more heavily influenced by nonnative plants. However, interestingly, the total wetland area estimated to have high or very high nonnative stressor levels is similar for all four NWCA aggregated ecoregions. The NWCA examined the relationship between relative extent of stressors, and relative and attributable risk as a way to identify emerging issues and prioritize management responses. Nationally, vegetation removal, hardening, and ditching stressors had the greatest national extent of wetland area at high stressor levels, affecting 23-27% of the Nation’s wetland area. Six of the eight stressors measured had relative risk values greater than one. Those stressors are: vegetation removal, hardening (e.g., parking lots, roads, trails, severely compacted soil), ditching, damming, filling/erosion, vegetation replacement. The stressors with the highest attributable risk in 2011 were vegetation removal, hardening, and ditching. However, the large error bars on all of the results indicate caution in drawing conclusions. Overall, the results from the 2011 NWCA can be used in wetland management and restoration;As a quantitative definition and benchmark of least disturbed condition; As a context for the results of smaller scale assessments;To develop management approaches and restoration designs to address common stressors; To prioritize effort based on attributable risk; andTo evaluate the effectiveness of management actions in achieving policy goals.

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