Urbanization is the most prevalent and permanent form of landscape change today and is particularly remarkable in that the end result is almost indistinguishable across the world. The similarity of landscapes created by urbanization has the scientific benefit of being an unplanned replicated experiment that allows us to explore how ecological communities are structured and function. In this talk, we present work from four rural-to-urban gradients in three different ecoregions of the United States: Cincinnati, Ohio; Oxford, Ohio; Saint Paul, Minnesota; and Palo Alto, California. We use multiple taxa – birds, butterflies, mammals and woody vegetation – to explore how communities change with urbanization and whether these changes are similar (or different) across ecoregions and across taxa. In particular, we examine how species richness, diversity and evenness change with urbanization; whether these changes reflect predictable patterns of invasion and extinction; and whether they affect community function.
Results/Conclusions
In general, species richness initially increases with slight levels of urbanization and then decreases substantially with more severe urbanization regardless of taxon or ecoregion. Shannon diversity displays a similar, but damped, response because evenness decreases monotonically with urbanization, indicating that urban environments become dominated by a limited number of species capable of exploiting these new landscapes. Examination of the responses of individual species to urbanization suggests that native species disappear with increasing urbanization and are replaced by ubiquitous, invasive species regardless of taxa or ecoregion. These changes in community composition also bring about changes in how these communities function, including shifts in life history strategies and resource exploitation.
