Gastropods on the green roof of a high-rise building in a large European city

Understanding the distribution and diversity of terrestrial snails on green roofs (GR) can facilitate insights into the ecological functioning of these urban habitats. While green roofs have been shown to provide suitable habitat for mobile species such as birds and insects, there needs to be more research concerning the colonisation and persistence of less mobile animal groups, including terrestrial gastropods. The present study investigates the species richness of terrestrial gastropods on green roofs of high-rise buildings in Bratislava, Slovakia. The study examined four distinct types of green roofs: The green roofs were classified according to their management intensity, resulting in four categories: extensive, semi-intensive GR-A, semi-intensive GR-B, and intensive. The categories differed in terms of vegetation, substrate depth, irrigation, and sun exposure. The survey employed a variety of methods, including pitfall trapping, vegetation sweeping, soil sampling, and microhabitat investigations. The survey yielded evidence of 11 species of terrestrial gastropods (six snails and five slugs) inhabiting three GR types. The semi-intensive GR-A, which is characterised by dense vegetation and minimal management, supported all 11 species. No gastropods were observed on the extensive GR with shallow substrate and Sedum sp. vegetation. The presence of native and non-native species, including the non-native slug Ambigolimax valentianus, indicates that terrestrial gastropods can colonise GR. These findings emphasise the potential of GR to support urban biodiversity and highlight the need for further research on less mobile species in these habitats.