Uncertainty of Forested Wetland Maps Derived from Aerial Photography

Forested wetlands (FWs) are economically and environmentally important, so monitoring of change is done using remote sensing by several U.S. federal programs. To better understand classification and delineation uncertainties in FW maps, we assessed agreement between National Wetlands Inventory maps based on aerial photography and field determinations at over 16 000 Forest Inventory and Analysis plots. Analyses included evaluation of temporal differences and spatial uncertainty in plot locations and wetland boundaries. User's accuracy for the wetlands map was 90% for FW and 68% for nonforested wetlands. High levels of false negatives were observed, with less than 40% of field-identified wetland plots mapped as such. Epsilon band analysis indicated that if delineation of FW boundaries in the southeastern U.S. met the data quality standards (5 meters), then the area within uncertainty bounds accounts for 15% to 30% of estimated FW area.

Assessing Wetland Changes in the Prairie Pothole Region of Minnesota From 1980 to 2007

Wetlands in the Minnesota Prairie Pothole Region are critical landscape elements because of their unmatched importance to breeding waterfowl, and other wildlife. They provide vast benefits to store runoff or act as nutrient sinks and offer other environmental and socio-economic returns. Data on location, extent and types of wetlands collected by the U.S. Fish and Wildlife Service National Wetlands Inventory is used for developing conservation strategies and evaluating net landscape changes affecting fish and wildlife populations. Minnesota wetlands were mapped 27 y ago by the National Wetlands Inventory. We examined 176 10.2-km2 (4-mi2) sample plots in the Minnesota Prairie Pothole Region, using aerial photo interpretation techniques, to determine the current accuracy of the National Wetlands Inventory data used in the eastern Prairie Pothole Region for conservation planning and evaluation. We stratified our analysis by Bailey's (1995) Ecological Subsections. We estimated that across the entire Minnesota Prairie Pothole Region 4.3% of wetland area has been lost since 1980 with losses varying from 0 to 15% among Ecological Subsections. Implications of these findings suggest that National Wetlands Inventory data should be regularly updated in areas subject to rapid wetland change.