Disentangling urban habitat and matrix effects on wild bee species

Abstract

In face of a dramatic decline of wild bee species in many rural landscapes, potential conservation functions of urban areas gain importance. Yet effects of urbanization on pollinators, and in particular on wild bees, remain ambiguous and not comprehensively understood. This is especially true for amenity grassland and extensively managed wastelands within large-scale residential housing areas. Using Berlin as a study region, we aimed to investigate (a) if these greenspaces are accepted by wild bee assemblages as foraging habitats; (b) how assemblage structure of bees and individual bee species are affected by different habitat (e.g., management, flower density) and urban matrix variables (e.g., isolation, urbanization); and (c) to what extent grassland restoration can promote bees in urban environments. In summer 2012, we collected 62 bee species belonging to more than 20% of the taxa known for Berlin. Urbanization significantly affected species composition of bees; 18 species were affiliated to different levels of urbanization. Most bee species were not affected by any of the environmental variables tested, and urbanization had a negative effect only for one bee species. Further, we determined that restoration of diverse grasslands positively affected bee species richnesss in urban environments. We conclude that differently structured and managed greenspaces in large-scale housing areas can provide additional foraging habitats and refuges for pollinators. This supports approaches towards a biodiversity friendly management within urban regions and may be of particular importance given that anthropogenic pressure is increasing in many rural landscapes.

Are all urban green spaces a favourable habitat for pollinator communities? Bees, butterflies and hoverflies in different urban green areas

“…An urbanised landscape may act as a filter for pollinator communities, promoting the colonisation of urban areas whose habitat attributes are the most suitable for these groups (Banaszak-Cibicka &Żmihorski, 2012;Chong et al, 2014). However, fewer studies concentrate on different types of urban green areas and their potential value in terms of urban pollinator diversity (Tonietto et al, 2011;Fischer et al, 2016). Researchers often compare pollinator communities between urban and non-urban (e.g.…”

“…Recent studies have shown that urban areas are also potentially attractive habitats for pollinators (McFrederick & LeBuhn, 2006;Lizée et al, 2011;Michołap et al, 2017). However, various habitats in the city, with unique qualities, urban planning, and management, could engender different responses in the pollinator community (Gobster, 2001;Öckinger et al, 2009;Tonietto et al, 2011;Fischer et al, 2016).…”

“…rural, nature reserves, agricultural areas) habitats (Verboven et al, 2014;Baldock et al, 2016). However, fewer studies concentrate on different types of urban green areas and their potential value in terms of urban pollinator diversity (Tonietto et al, 2011;Fischer et al, 2016). Determining which habitats are important for pollinators can help protect this group of insects in cities.…”

Specialist nectar-yeasts decline with urbanization in Berlin

“…Apart from or in addition to a behavioral response, this shift from specialists towards generalists could result from changes in composition, abundance, or incidence of pollinator species21.…”

Sustainability

“…By evaluating seven sites on a university campus, they found that considerably more mosquitoes were captured on conventional rooftops than on green roofs, attributable to the ponding of water in depression storage on conventional roofs. The use of green roofs by wild bee species was evaluated by Fischer et al (2016) in Berlin (Germany), finding that restoration of diverse grasslands positively affected bee species richnesss in urban environments. Cameron and Blanusa (2016) for a more sustainable management of the water-energy nexus in treatment systems is also discussed.…”