What factors drive arthropod communities on extensive green roofs of Central Argentina?

GONZÁLEZ, EZEQUIEL; FABIAN, DIEGO; SANCHEZ DOMINGUEZ, M. VIRGINIA; BIKIC, BORIS; SALVO, ADRIANA; FENOGLIO, MARÍA SILVINA

Praga

Congreso; 6th European Congress of Conservation Biology-ECCB Prague; 2022

Czech University of Life Sciences Prague - Society for Conservation Biology

Green roofs represent an environmentally friendly alternative to standard roofs that provide ecosystem services such as rainwater retention, an increase of the energy efficiency and reduction of the “heat island” effect. Moreover, green roofs have the potential to act as habitats to plant and animal species in urban ecosystems. However, because they are structurally simpler and present adverse environmental conditions, they could support a lower number of species than habitats at ground level. Furthermore, the different land uses of the surrounding landscape can also influence and limit the communities that inhabit these novel habitats. Here, we compared the insect communities on green roofs and neighbor ground habitats in an area with low urbanization levels in central Argentina, in one of the first studies of its kind for South America. We focused on different functional groups and evaluated their responses to the proportions of forests, buildings, and roads surrounding each house. During March 2017, we sampled insects in 15 houses in central Córdoba (Argentina) using three yellow pan traps at each location. For each house, we calculated the proportions of native forests, buildings, and roads in their surroundings, using a landscape circle of 200 m radius. In total, 14988 individuals from 714 species were found, of which almost 400 were collected on green roofs. The most diverse order in both ground habitats and green roofs was Hymenoptera, whereas Diptera was the more abundant on ground habitats and Hemiptera on green roofs. Regarding functional groups, herbivores were the most diverse in neighbor ground habitats and parasitoids on green roofs. Richness and abundance of arthropods, total and by functional groups, were significantly higher in neighbor ground habitats than on green roofs. Furthermore, the proportion of the landscape covered by roads negatively affected total and herbivore richness, and abundance of herbivores, parasitoids, and pollinators in both habitats. For other functional groups, landscape measures showed an interaction with roof/ground position, with negative effects of roads for omnivore species only on green roofs and for predators’ abundance only on neighbor ground habitats. It must be highlighted that, despite that green roofs presented 50% fewer species than neighbor ground habitats, on average 25-30 species of insects were collected on green roofs and several functional groups were found. Therefore, these results represent new evidence regarding the role of these new ecosystems as habitat providers for a large number of arthropod species that may be carrying out relevant ecological processes. The proportion of roads around the houses was the most important landscape variable and this suggests that, even in an area with low levels of urbanization, roads could be acting as barriers to insect movement that negatively affects their communities.