Estimates of accessible food resources for pollinators in urban landscapes should take landscape friction into account

Abstract

Maintaining biodiversity in urban landscapes requires a well-functioning green infrastructure for the landscape to remain ecologically functional. However, city planners often lack knowledge to identify how well different parts of the green infrastructure are connected, and tools to estimate the accessibility to important habitats for different species in urban areas are strongly needed. We compared the ability of three measures of available food resources, with increasing complexity, for explaining species richness and abundance of bees and wasps at 23 locations in an urban landscape in Sweden. Specifically, we tested (1) the summed amount of food habitat within a buffer circle, (2) the amount of food habitat weighted by distance, and (3) the summed amount of food habitat within an area created by cost-weighted distance based on the surrounding landscape friction. We tested two spatial scales (200 and 400 m). The results show that both the summed (1) and the weighted measures (2) were very poor in explaining species richness and abundance regardless of spatial scale, while we found significant relationships for both species richness and abundance with the friction-based measure (3) at both scales. For the friction-based measure, the relationships with both response variables were strongest at the smallest spatial scale (200 m). We conclude that bees and wasps are sensitive to barriers such as large roads and built-up areas when foraging in urban environments. This is important to consider when assessing the functionality of urban green infrastructure in order to not overestimate the available amount of habitat and how well different parts of the landscape are connected for these important pollinators.

The surrounding landscape shapes the abundance of Sphaerophoria scripta and Melanostoma mellinum (Diptera: Syrphidae) in Portuguese vineyards

“…The artificial territory is one of the significant drivers of biodiversity loss, given the destruction and fragmentation of the habitats (Aronson et al, 2017; Persson et al, 2020). Although urban areas may provide beneficial habitats to flower‐visiting insects (e.g., parks, gardens, SNH fragments, and brownfields) (Aronson et al, 2017; Baldock et al, 2019; Hall et al, 2017; Persson et al, 2020), the buildings and roads that shape the artificial territory function as barriers that fragment the foraging landscapes of pollinators (Buchholz et al, 2020; Jha, 2015; Johansson et al, 2018).…”

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“…By connecting people and goods, linear infrastructure (such as road and railroad verges) reduces and fragments habitats, affecting insect and animal mortality, mobility, and distribution. Roads can affect vegetation and pollinator distribution (Johansson et al 2018). However, several studies have examined rural linear infrastructures, such as ecological corridors and green areas, as paramount opportunities for conserving grassland species and pollinators.…”

Research Foundation and Hotspot Analysis of Urban Road Ecology—A Bibliometric Study Based on CiteSpace

“…Johansson emphasized the need for infrastructure construction to consider its impact on biological habitats. The viewpoint that bees are very sensitive to interference from large roads was analyzed from three perspectives: total number of food habitats, weighted total number of food habitats, and friction of surrounding landscapes [28]. Cluster #5 refers to green development, focusing on topics such as green belts and roads, political ecology perspective, extended infrastructure landscape, and gateway projects.…”