An urban ecological land-cover map containing 37 unique classes was created for New York City using object-based imagery analysis (OBIA) techniques in conjunction with multispectral orthoimagery, Light Detection and Ranging (LIDAR) data, thematic Geographic Information System (GIS) layers, and local expert opinion. Based on a classification scheme adapted from the United States National Vegetation Classification (NVC), the new map included a mix of ecological and anthropogenic features mapped across four hierarchical levels of detail: 1) basic land cover; 2) land-cover sub-classes; 3) NVC Group; and 4) NVC Association. All ecologically-relevant classes were mapped to the NVC Group level, and a subset of 9 classes were mapped to the NVC Association level. These classes included upland forests (e.g., oak-tulip, coastal-oak hickory), maritime forests (e.g., maritime post oak forest), upland grass\shrubs (e.g., dune and coastal grassland and shrubland), freshwater wetlands (e.g., wet meadow, freshwater marsh), tidal wetlands (e.g., high salt marsh, brackish tidal marsh), and aquatic vegetation (e.g., intertidal shore vegetation). Features in dense urban zones such as maintained grass\lawns and neighborhood trees were assigned to anthropogenic classes to further highlight the most important ecological features. An accuracy assessment conducted on the Level 2 map indicated an overall accuracy of 92%, a high classification rate attributable in part to the efficient mapping of widely-distributed upland forest classes. Forested wetlands and other uncommon wetland features were predictably mapped with lower accuracy, primarily because they were often difficult to discriminate from upland forest types. A quantitative accuracy assessment for the Level 3 and Level 4 NVC classes was not conducted, but the quality of these classes likely varied by data input (i.e., high for classes based on expert opinion, lower for classes based on multispectral criteria). The new map will facilitate understanding of the city-wide occurrence and distribution of ecological diversity and serve as baseline documentation for monitoring and protecting New York City’s natural resources. Future versions of the map will benefit from recent advances in object-based wetlands modeling that uses topographic factors to isolate forested wetlands and other features that are difficult to discern even with high-resolution imagery.
