Abstract
AbstractMaintaining 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.
Highlights
As city regions around the world get increasingly populated, the land use requirements in and around cities increase
Our results instead strongly suggest that estimates of available food resources for important pollinators in urban environments should be based on the cost distance (e.g., Adriaensen et al 2003) rather than the Euclidian distance, to account for differences in matrix permeability
Measures that do not take landscape friction into account most likely overestimate the amount of accessible food habitat (Fig. 2) as they include habitat that is not reachable for the insects
Summary
As city regions around the world get increasingly populated, the land use requirements in and around cities increase. This often occurs at the expense of urban green areas. Maintaining a high biodiversity is important, as it increases the possibility of preserving rare and endangered species, and because a high biodiversity is crucial for ecosystem functioning and for delivering ecosystem services (e.g., Dıaz et al 2006). Maintaining biodiversity in urban landscapes requires a well-functioning green infrastructure so that the landscape remains well connected and ecologically functional, which is stated in the EU Biodiversity Strategy (European Commission 2017). City planners often lack knowledge to identify how functional different parts of the green infrastructure are for certain species. Tools to estimate available habitat in urban areas are strongly needed
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