ABSTRACT
Urban areas are spatiotemporally heterogeneous landscapes that include remnants of natural landscapes, patches of agrarian landscapes, designed urban green spaces, and novel urban ecosystems. Within urban areas, often greater numbers of vascular plant species exist as compared to adjacent non-urban regions. At the same time, urban environments reduce plant functional diversity, shift the functional and genetic composition of plant communities, and decrease the diversity of evolutionary relationships among species. These patterns are driven by combinations of anthropogenic and environmental drivers related to climate, biogeography, land use, human mediated biotic interchange, urban form, development history, socioeconomic and cultural influences, local human facilitation, and species interactions. Different groups of species – spontaneous versus cultivated and native versus non-native species – respond to these drivers to different degrees. Non-vascular plants, such as lichens and mosses, also respond differently, with especially lichens showing reduced diversity in urban areas. One key research question is, of which type, size, density, connectivity, and quality urban green spaces need to be maintained or created to enhance plant diversity. Urban biodiversity conservation efforts so far indicate that a dense network of larger and smaller green spaces of all sorts of habitats will help achieve conservation targets, adding to global biodiversity conservation.
