We are living in the Anthropocene, where the effects of urbanization on biodiversity are increasingly important for global conservation. Cities can be considered refuges for some species but more likely ecological traps for others, because urban spaces constitute poor habitats offering little opportunity for reproductive success despite their apparent suitability.
In this special Frontiers issue, we investigate a broad range of characteristics of cities in order to get a better understanding of the underlying mechanisms driving species distribution and abundance, and also the consequences of such proximate mechanisms for gaining a better understanding of the effects of urbanization on biodiversity.