Urban “Sky islands”: Novel habitat patches on green roofs and their potential for vegetation and flower-visiting insects

Many novel habitats in urban areas are increasingly recognised as valuable opportunities for biodiversity conservation. In particular, extensively greened roofs are important not only regarding the urban climate (e.g. cooling effects), but also as promising sites for supporting diverse species groups. This study investigated the diversity and functional characteristics of plants as well as the diversity of flower-visiting insects on green roofs in a highly urbanised area (Frankfurt am Main, Germany). Specifically, we analysed the extent to which such isolated roof sites can be considered habitat islands and which effects temporal (roof age) and spatial factors (e.g. greened area, connectivity) have on vegetation composition and the occurrence of different groups of flower-visiting insects. Our findings show that extensively greened roofs have considerable potential for supporting various species, while factors such as roof age and the surrounding landscape context (connectivity) play an important role.

Greened rooftop (Goethe-University Campus Westend) in Frankfurt: new habitats?