A comparison of the New Jersey Freshwater Wetland maps to field-delineated wetlands was undertaken to assess the accuracy of the Freshwater Wetland maps. The evaluation revealed substantial differences in the amount of wetland acreage on the Freshwater Wetland maps compared to field-verified wetlands. Forty study sites comprising 21,877 acres (8,854h) were evaluated. Of these, twenty-seven were overmapped (more wetland acreage than was field-verified), and thirteen were undermapped. Forty-three percent had mapping discrepancies at or above fifty percent; when modified land designations were included as wetlands, the number of sites at this threshold increased to fifty percent.

Paper copies of the Freshwater Wetland maps have been distributed to each municipality in the state and have also been digitized for Geographic Information System (GIS) applications. The maps are now a standard component of the state's GIS database. There is growing evidence that the maps are being used for wider applications than the accuracy of the mapping can justify. The data sources about the purpose and limitations of the maps are confusing and often contradictory.

The analysis conducted as part of this study suggests that the Freshwater Wetland maps should be used for only the most general land-use and planning purposes. They are generally unsuitable for regulatory and land transaction decisions.