Using the National Wetland Condition Assessment Data

Background/Question/Methods

The U.S. Environmental Protection Agency (EPA), states, and tribes are conducting a series of surveys of the nation's aquatic resources. Often referred to as probability-based surveys, these studies provide nationally consistent and scientifically-defensible assessments of our nation's waters and can be used to track changes in condition over time. Each survey uses standardized field and lab methods and is designed to yield unbiased estimates of the condition of the whole water resource being studied (i.e., rivers and streams, lakes, wetlands, or coastal waters).  In 2011, EPA and its State, Tribal, and Federal partners implemented the first national survey on the condition of the Nation's wetlands. The National Wetland Condition Assessment (NWCA) is designed to provide regional and national estimates of wetland ecological integrity and rank the stressors most commonly associated with poor conditions.

While the survey is designed to produce a national report describing the health of the Nation’s wetland resources, another goal of the NWCA is to build state and tribal capacity to monitor wetland condition, including development of an operational set of indicators and related thresholds that can be applied in describing how wetlands perform.  One way that NWCA contributes to this goal is by applying the reference condition approach, commonly used for assessing other waterbody types.  A reference condition was derived for the NWCA by screening sites to identify those in least-disturbed condition within aggregated ecoregions (Omernik) and developing assessment thresholds following EPA guidance.  Using this approach, the NWCA documented biological condition response using the Vegetative Multi-Metric Index (VMMI) and comparing that index’s response across a range of stressors.

Results/Conclusions

The results from the NWCA and the approaches used in the assessment can be used by States and Tribes to develop appropriate indicators and assessment thresholds for evaluating the health of wetlands at more local scales.  Documenting reference condition can support derivation of water quality standards that are specific to different classes of wetlands and can be used to support meaningful mitigation performance standards and attainable restoration goals. 

The NWCA report and supporting data are expected to be publically available in Fall 2015.  At that time, EPA will be issuing the second NARS Campus Research Challenge to encourage graduate students to use NWCA data to conduct further scientific research and analysis. This challenge is intended to encourage external, innovative research in support of enhanced water management at multiple scales.