A Integrative Investigation of Urban Animals and the Ecosystem Services They Provide in Cities

Abstract

Urban landscapes are complex social-ecological systems comprising human and natural elements and their interactions. A key priority for research in these landscapes is understanding how humans affect the presence and abundance of wild organisms and how those organisms, in turn, provide ecosystem services that affect humans. In this dissertation, I use two field studies to understand the ecosystem services provided by urban animals in green spaces across Philadelphia and in a third study I investigate geographic bias in where urban animals have been studied in the United States. For the first study, I use a functional trait approach to examine how urban bird communities respond to landscape- and local-scale habitat and how community composition corresponds to potential ecosystem services. I show that the landscape-scale context of a green space has a stronger influence on species’ abundances than local-scale habitat. As a result, the effect traits associated with cultural and regulating ecosystem services varied strongly along the landscape-scale gradient of urbanization. Local-scale variation in habitat had little effect. The importance of landscape-scale habitat in driving the supply of bird-mediated ecosystem services underscores the importance of regional urban planning for green spaces.In the second study, I use a field experiment to determine the drivers of an understudied ecosystem service – the removal of littered food waste by birds and squirrels. I recorded food removal activity by animals in green spaces across Philadelphia and found that Eastern gray squirrels (Sciurus carolinensis) are the main driver of this service. With increased squirrel abundance, removal level is higher and is both initiated and completed more quickly. This service is also context dependent, such that more food is removed in urban parks and picnic areas, where animals are presumably accustomed to consuming anthropogenic foods. These results highlight the importance of animal behavior, and factors that affect it, for the supply of ecosystem services. In my third study, I take a geographic approach to identifying bias in the study of animals in urban landscapes. Our knowledge of urban ecosystems in the United States is based on hundreds of field studies and thousands of individual field sites, but the distribution of these sites has never been examined. I reviewed the literature and mapped field sites to assess geographic bias in the location of urban ecology field sites. At a national scale, I find that urban ecologists tend to work in larger cities, especially those that are less socioeconomically vulnerable (more affluent). I also find that the social-ecological attributes of the neighborhoods in which ecologists work depends on the framing of their study as well as the focal taxa and functional groups studied. Overall, the neighborhoods where marginalized people live are an underexplored segment of the urban landscape. This is the first study to identify geographic biases in urban ecology field sites and provides a basis for future urban ecology research that produces knowledge applicable to all cities and neighborhoods.