Wild Bee Conservation within Urban Gardens and Nurseries: Effects of Local and Landscape Management

Abstract

Across urban environments, vegetated habitats provide refuge for biodiversity. Gardens (designed for food crop production) and nurseries (designed for ornamental plant production) are both urban agricultural habitats characterized by high plant species richness but may vary in their ability to support wild pollinators, particularly bees. In gardens, pollinators are valued for crop production. In nurseries, ornamental plants rarely require pollination; thus, the potential of nurseries to support pollinators has not been examined. We asked how these habitats vary in their ability to support wild bees, and what habitat features relate to this variability. In 19 gardens and 11 nurseries in California, USA, we compared how local habitat and landscape features affected wild bee species abundance and richness. To assess local features, we estimated floral richness and measured ground cover as proxies for food and nesting resources, respectively. To assess landscape features, we measured impervious land cover surrounding each site. Our analyses showed that differences in floral richness, local habitat size, and the amount of urban land cover impacted garden wild bee species richness. In nurseries, floral richness and the proportion of native plant species impacted wild bee abundance and richness. We suggest management guidelines for supporting wild pollinators in both habitats.

Domestic Gardens Mitigate Risk of Exposure of Pollinators to Pesticides—An Urban-Rural Case Study Using a Red Mason Bee Species for Biomonitoring

“…Earlier research highlighted the potential of urban green spaces in terms of providing diverse nesting and forage sources to pollinators, which have decreased in rural areas [5,12]. On the other hand, the production of crops in peri-urban and urban areas may benefit from a pollination ecosystem service flow from these green refugia [13,15,54]. We add new findings on the potential of gardens to provide an enhanced quality of forage resources for pollinators [18,49].…”

“…Domestic gardens are defined as an area adjacent to a domestic dwelling [51]. Aside from the benefits in terms of human health and well-being, air cooling or support of biodiversity [12,13,[52][53][54], the misuse of fertilizers and pesticides in domestic gardens [55], out of any institutional control, may pose a risk to pollinators. On the other hand, a lower intensity of agrochemicals use in gardens than in the agricultural landscape could be expected on the basis of earlier research [18,49].…”

Biodiversity Conservation and Sustainable Urban Development

“…This Special Issue covers a broad geographical range, with contributions from Africa [17], Asia [18][19][20], Australia [21,22], Europe [23][24][25][26][27][28][29][30] and North America [31][32][33]. It explores a range of ecosystems in the urban realm, spans natural remnants such as forests [30,32], wetlands [18,21], and natural grasslands [17,22], traditional urban greenspaces including cemeteries [33], gardens [29,31], and, finally, novel urban ecosystems such as green roofs and constructed wetlands [20,26], built-up areas [23], railway bridges [24] and emerging forests on vacant land [27]. In combination, a wide range of socio-cultural and environmental settings are explored and discussed.…”

“…Several papers explore biodiversity in relation to diverse features of urban environments and address a range of animal groups [21,24,27,31,33] and plants [17,18,20,22,27,30,32], including some multi-taxa studies [24,26,27]. Other papers explicitly address urban environments as socio-ecological systems [19,22,25], or further methodological approaches in understanding the people-nature intersection in cities [23,28,29].…”

“…Wild bee conservation is a worldwide issue, and many cities are developing strategies to support wild pollinators in anthropogenic habitats. Egerer et al [31] provide advanced insights into the effects of local and landscape management in urban gardens and nurseries. Among other factors, increasing floral richness in both settings supported wild bee species richness.…”