Ladd, B.6/22/20222022-09-306/22/20222022-09-302016https://doi.org/10.3390/land5030023Urban ecosystems are carrying an extinction debt. Mitigating this debt will require the development of a predictive framework that improves our understanding of the factors causing decline of native biodiversity in urban areas. I argue that nitrogen is a common currency around which such a predictive framework could be built. I first summarise the evidence that shows the probable extent of nitrogen enrichment in urban ecosystems. I then review the body of empirical evidence that describes how nitrogen enrichment affects ecosystem process and function. By unifying these two bodies of empirical evidence, I generate a series of testable hypotheses that may allow for a better understanding of native biodiversity loss in urban areas. © 2016 by the author.application/pdfenginfo:eu-repo/semantics/closedAccessEnvironmental Scienceinfo:eu-repo/semantics/article10.3390/land5030023http://purl.org/pe-repo/ocde/ford#1.05.00