Urbanization Consequences: Case Studies in the Hudson River Watershed
Karin E. Limburg, Karen M. Stainbrook, Jon D. Erickson, and John M. Gowdy
Abstract.—Parcel by parcel, urban/suburban development is one of the most active converters of land in the Hudson River Valley in New York State. We are taking an integrative approach to understanding the drivers of and responses to urbanization, by studying how economy drives land use change and how that, in turn, affects downstream indicators of ecosystem state. The ultimate goal of the project is to provide a tool for policymakers, illustrating consequences of different development strategies. In this paper, we discuss synoptic ecological assessments of two major Hudson River tributaries in Dutchess County, the Wappinger Creek and Fishkill Creek watersheds. Physical, chemical, geographic, and biotic indices are compiled, creating a multivariate data set. These data, when set into a geographic information database, provide a spatial response to land use. Application of a regionally calibrated index of biotic integrity showed little relationship to urbanization, although some component metrics indicated a response. Chemical or biogeochemical indicators were more reflective of urbanization gradients. A hierarchy of responses, beginning with physicochemical and moving up to fish assemblages, reflected decreasing responses to urbanization. However, fish densities and the stable isotopic ratios of nitrogen determined in a sentinel species (eastern blacknose dace Rhinichthys atratulus) were significantly affected by urbanization. Longitudinal gradients of elevation were identified as strong drivers of development, potentially confounding relationships of land-use attributes and ecological responses.