Sujay S. Kaushal

Urban ecological systems: Scientific foundations and a decade of progress

Urban ecological studies, including focus on cities, suburbs, and exurbs, while having deep roots in the early to mid 20th century, have burgeoned in the last several decades. We use the state factor approach to highlight the role of important aspects of climate, substrate, organisms, relief, and time in differentiating urban from non-urban areas, and for determining heterogeneity within spatially extensive metropolitan areas. In addition to reviewing key findings relevant to each state factor, we note the emergence of tentative urban syndromes concerning soils, streams, wildlife and plants, and homogenization of certain ecosystem functions, such as soil organic carbon dynamics. We note the utility of the ecosystem approach, the human ecosystem framework, and watersheds as integrative tools to tie information about multiple state factors together. The organismal component of urban complexes includes the social organization of the human population, and we review key modes by which human populations within urban areas are differentiated, and how such differentiation affects environmentally relevant actions. Emerging syntheses in land change science and ecological urban design are also summarized. The multifaceted frameworks and the growing urban knowledge base do however identify some pressing research needs.

Ultra-urban baseflow and stormflow concentrations and fluxes in a watershed undergoing restoration (WS263)

We discuss the results of sampling baseflow and stormwater runoff in Watershed 263, an ultraurban catchment in west Baltimore City that is undergoing restoration aimed at both improving water quality as well as the quality of life in its neighborhoods. We focus on urban hydrology and describe the high baseflow and stormwater nutrient, metal, bacterial and other pollutant concentrations and loads seen in two 15 ha headwater storm drain catchments within WS263 that were sampled from 2004 to 2010. These data revealed several potentially important implications for watershed restoration efforts. First, the underground, or “buried stream” baseflow loads can be substantial, even relative to the surface urban runoff loads in highly impervious urban catchments. Second, the large pollutant load exports from these residential catchments suggest that older, highly urban landscapes may be important hotspots, as these small headwater catchments are numerous in the urban landscape. Third, the complex nature of the pollutant export patterns at the Baltimore and Lanvale catchments, both spatially and temporally, suggest that there may be complex drivers involved. Since this complexity may involve one or more systems of urban water networks, conceptualization in terms of the Urban Watershed Continuum (Kaushal and Belt, 2012) may be a useful tool to use both in their characterization and in designing interventions. Lastly, if these small headwater catchments truly represent a larger typology in terms of being hotspots, the characterization and mapping of older ultra-urban catchments may well be worthwhile given the large numbers of potential analogues in the urban landscape and the likely increasing role of aging infrastructure in creating more and larger “unseen” pollutant loads.