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Wetlands as Habitat in Urbanizing Landscapes: Patterns of Bird Abundance and Occupancy
Citation:
MCKINNEY, R. A., K. B. Raposa, AND R. M. Cournoyer. Wetlands as Habitat in Urbanizing Landscapes: Patterns of Bird Abundance and Occupancy. LANDSCAPE AND URBAN PLANNING. Elsevier Science Ltd, New York, NY, 100(1-2):144-152, (2011).
Impact/Purpose:
This manuscript investigates the impact of urbanization on the ecosystem service wildlife habitat value in a series of freshwater wetlands in the northeast US. As natural habitats become fewer in number and more fragmented through urbanization, ecosystem services provided by small isolated wetlands may become increasingly important. For example, wildlife habitat provided by wetlands in urban landscapes may help support both wetland obligates and species that can opportunistically take advantage of higher productivity promoted by mesic conditions. The study examined breeding bird communities in urban and rural wetlands and nearby uplands along a gradient of watershed urbanization. Bird abundance and species richness was significantly higher at wetlands versus uplands, and overall, more species were seen at wetland versus upland sites. Species-specific habitat models using general vegetation classes also showed differences in bird-habitat associations as watersheds became more urbanized. Results of this study suggest that changes in the extent of urbanization may impact bird use of remnant natural habitats to the extent that wetlands may be inordinately beneficial to maintaining populations of some species in human-dominated landscapes. The findings demonstrate the importance of wetland habitats, and could provide evidence to state and local land use planners that supports the protection and restoration of small isolated wetlands as a means towards maintaining or enhancing habitat heterogeneity and biodiversity in urban landscapes. For example, the State of Rhode Island Department of Environmental Management encourages local communities to implement the principles of conservation development, a land use technique that accommodates growth while protecting a significant proportion of a development parcel as open space, in land use planning. Studies such as this that examine habitat value of specific habitats can help inform the debate on the optimal types of open space to be conserved under development plans, if maintaining biodiversity is a goal.
Description:
As natural habitats become fewer in number and more fragmented through urbanization, functions and services provided by small isolated wetlands may become increasingly important in maintaining ecosystem processes. For example, wildlife habitat provided by wetlands in urban landscapes may help maintain biodiversity by supporting both wetland obligates and species that can opportunistically take advantage of higher productivity promoted by mesic conditions. To test this hypothesis, we examined breeding bird communities in urban and rural wetlands and nearby uplands in the northeast US. From mid-May through June in 2008 and 2009, we conducted 10-min, 50 m radius point counts at 99 randomly chosen sites along a gradient of watershed urbanization. Bird abundance and species richness was significantly higher in wetlands versus uplands (t = 2.02 and 2.07; p = 0.02 in both cases), and at urban wetlands versus urban uplands (t = 4.92 and 3.26; p = 0.001 and 0.002, respectively), but not at rural wetlands versus rural uplands. Overall, more species were present at wetland versus upland sites, but the difference between wetland and upland was less for human-tolerant species. Species-specific habitat models using general vegetation classes showed differences in bird-habitat associations as watersheds became more urbanized. In particular, several species that were not associated with wetlands at rural sites (e.g., Carolina wren Thryothorus ludovicianus and common yellowthroat Geothlypis trichas) showed a strong positive association with wetlands in more urbanized landscapes. Our results suggest: 1) birds may be responding to mesic conditions by preferentially using wetland habitats, particularly in urban areas; 2) wetlands may also be supporting less ubiquitous or human intolerant birds that are targets for conservation; and 3) changes in the extent of urbanization may impact bird use of remnant natural habitats to the extent that wetlands may be inordinately beneficial to maintaining populations of some species in human-dominated landscapes. Our findings demonstrate the importance of wetland habitats for birds, and add to the body of evidence that supports the protection and restoration of small isolated wetlands as a means towards maintaining or enhancing habitat heterogeneity and biodiversity in urban landscapes.