Abstract
Forested wetlands in metropolitan areas function to support biodiversity, protect water quality, store floodwaters, and maintain streamflow, but they also function to provide natural areas for passive recreation, education, and esthetic appreciation for the surrounding human populations. However, the presence of dense human populations in the watersheds of wetlands is usually associated with disturbance and the diminution of the capacity of the wetlands to provide socially-valued ecological functions. I have examined indicators of biological, hydrologic, biogeochemical, and social functions in a sample of twenty-one mature forested wetlands located in northeastern New Jersey, USA, part of the New York City metropolitan region, which supports over 2000 people km−2. The field data and the principal components analyses of the sets of indicator variables for each class of function showed that the wetlands were arrayed along welldefined complex gradients in each case and that some functions were being performed at high levels in some of the wetlands despite the urban setting. However, the arrangement of sites within each ordination space differed, suggesting complex relationships among the various functions, some of which may be contradictory. For example, high ability to store floodwaters and evidence of flooding is associated with greater plant diversity and presence of obligate wetland species but is also associated with poor habitat for vertebrates and the presence of water-borne trash and exotic species. Conversely, low wetness is associated with high quality of habitat for vertebrates but also increased disturbance from large-scale dumping of trash and human disturbance and the release of nitrate from the soils. High levels of human use in and around the wetlands, while providing opportunity for human use and appreciation of the sites, is associated with low plant diversity and high release of nitrate-nitrogen. I conclude that because the functions performed by urban wetlands include human use and presence, there will necessarily be trade-offs required among ecological and human functions.
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Ehrenfeld, J.G. The expression of multiple functions in urban forested wetlands. Wetlands 24, 719–733 (2004). https://doi.org/10.1672/0277-5212(2004)024[0719:TEOMFI]2.0.CO;2
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DOI: https://doi.org/10.1672/0277-5212(2004)024[0719:TEOMFI]2.0.CO;2