Development and validation of rapid assessment indices of condition for coastal tidal wetlands in southern New England, USA.

Vegetation, soils, on-site disturbances, and watershed land use and land cover were assessed at 81 coastal tidal wetland sites using the New England Rapid Assessment Method. Condition indices (CIs) were derived from various combinations of the multi-dimensional data using principal component analyses and a ranking approach. Nested within the 81 wetlands was a set of ten reference sites which encompassed a range of watershed development and nitrogen loadings. The reference set of coastal tidal wetlands was previously examined with an intensive assessment, which included detailed measures of vegetation, soils, and infauna. Significant relationships were found between most of the rapid assessment CIs and the intensive assessment index. Significant relationships were also found between rapid assessment CIs and the developed lands in a 1-km buffer around the coastal wetlands. The regression results of the rapid assessment CIs with the intensive assessment index suggest that measures of vegetation communities, marsh landscape features, onsite marsh disturbances, and watershed natural lands can be used to develop valid CIs, and that it is unnecessary to make finer scale measurements of plant species and soils when evaluating ambient condition of coastal tidal wetlands in southern New England. However, increasing the survey points within coastal tidal wetland units when using a rapid assessment method in southern New England would allow for more observations of vegetation communities, marsh landscape features, and disturbances. Nevertheless, more detailed measures of hydrology, soils, plant species, and other biota may be necessary for tracking restoration or mitigation projects. A robust and standardized rapid assessment method will allow New England states to inventory the ambient condition of coastal tidal wetlands, assess long-term trends, and support management activities to restore and maintain healthy wetlands.