The proportion of impervious surfaces at the landscape scale structures wild bee assemblages in a densely populated region.

Benoît Geslin,Floriane Flacher,Samuel Perret,Eric Motard,David Carmignac,Morgane Folschweiller,Isabelle Dajoz,Violette Le Féon

doi:10.1002/ece3.2374

Abstract

Given the predicted expansion of cities throughout the world, understanding the effect of urbanization on bee fauna is a major issue for the conservation of bees. The aim of this study was to understand how urbanization affects wild bee assemblages along a gradient of impervious surfaces and to determine the influence of landscape composition and floral resource availability on these assemblages. We chose 12 sites with a proportion of impervious surfaces (soil covered by parking, roads, and buildings) ranging from 0.06% to 64.31% within a 500 m radius. We collected using pan trapping and estimated the landscape composition of the sites within a 500 m radius and the species richness of plant assemblages within a 200 m radius. We collected 1104 bees from 74 species. The proportion of impervious surfaces at the landscape scale had a negative effect on wild bee abundance and species richness, whereas local flower composition had no effect. Ground‐nesting bees were particularly sensitive to the urbanization gradient. This study provides new evidences of the impact of urbanization on bee assemblages and the proportion of impervious surfaces at the landscape scale emerged as a key factor that drives those assemblages.

Highlights

One of the major causes of the current bee decline is the destruction of natural habitats (Brown and Paxton 2009; Winfree et al 2009; Goulson et al 2015) due to agricultural intensification and increasing urbanization (SteffanDewenter et al 2002; Tscharntke et al 2005; McKinney 2006, 2008; Winfree et al 2009)
Our results indicate that increasing urbanization as measured by an increasing proportion of impervious surfaces within a 500 m radius resulted in an important decrease in wild bee abundance and species richness
We found an important decrease in bee abundance and species richness along the urbanization gradient, which was measured by an increase in the proportion of impervious surfaces within a 500 m radius

Summary

Introduction

One of the major causes of the current bee decline is the destruction of natural habitats (Brown and Paxton 2009; Winfree et al 2009; Goulson et al 2015) due to agricultural intensification and increasing urbanization (SteffanDewenter et al 2002; Tscharntke et al 2005; McKinney 2006, 2008; Winfree et al 2009). Urbanization permanently alters habitats and destroys natural areas that include floral resources and nesting sites for wild bees (McKinney 2002; Banaszak-Cibicka and Z_ mihorski 2012). This impact is likely to increase in the near future due to the predicted expansion of cities worldwide (McDonnell and Hahs 2008; Hennig and Ghazoul 2011a). Urbanization and its impact on bees and pollinators in general have received increasing attention over the past few years (see Hernandez et al 2009 for a review; Bates et al 2011; Bergerot et al 2011; Matteson et al 2012; Geslin et al 2013; Fortel et al 2014; Verboven et al 2014).

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Conclusion