Wild pollinator activity negatively related to honey bee colony densities in urban context

Abstract

As pollinator decline is increasingly reported in natural and agricultural environments, cities are perceived as shelters for pollinators because of low pesticide exposure and high floral diversity throughout the year. This has led to the development of environmental policies supporting pollinators in urban areas. However, policies are often restricted to the promotion of honey bee colony installations, which resulted in a strong increase in apiary numbers in cities. Recently, competition for floral resources between wild pollinators and honey bees has been highlighted in semi-natural contexts, but whether urban beekeeping could impact wild pollinators remains unknown. Here, we show that in the city of Paris (France), wild pollinator visitation rates are negatively correlated to honey bee colony densities present in the surrounding landscape (500m –slope = -0.614; p = 0.001 –and 1000m –slope = -0.489; p = 0.005). Regarding the morphological groups of wild pollinators, large solitary bee and beetle visitation rates were negatively affected by honey bee colony densities within a 500m buffer (slope = -0.425, p = 0.007 and slope = - 0.671, p = 0.002, respectively) and bumblebee visitation rates were negatively affected by honey bee colony density within a 1000m buffer (slope = - 0.451, p = 0.012). Further, lower interaction evenness in plant-pollinator networks was observed with high honey bee colony density within a 1000m buffer (slope = -0.487, p = 0.008). Finally, honey bees tended to focus their foraging activity on managed rather than wild plant species (student t-test, p = 0.001) whereas wild pollinators equally visited managed and wild species. We advocate responsible practices mitigating the introduction of high density of honey bee colonies in urban environments. Further studies are however needed to deepen our knowledge about the potential negative interactions between wild and domesticated pollinators.

Gradual replacement of wild bees by honeybees in flowers of the Mediterranean Basin over the last 50 years

“…Correlative and experimental evidence alike has recently shown that, at local or regional scales, honeybees can have strong negative impacts on wild bee populations in both natural and anthropogenic scenarios (Shavit et al 2009, Lindström et al 2016, Torné-Noguera et al 2016, Magrach et al 2017, Ropars et al 2019, Valido et al 2019), and that the absence of honeybees in well-preserved natural areas is associated with increasing wild bee populations (Herrera 2019). Much of the direct or circumstantial evidence on the harmful effects of honeybees on wild bees originated in the Mediterranean Basin, which motivated the hypothesis formulated in this paper of a possible replacement of wild bees by honeybees in the Mediterranean running parallel to the increasing abundance of honeybees.…”

“…S1, Potts et al 2010, vanEngelsdorp and Meixner 2010, Moritz and Erler 2016). Honeybees have been repeatedly shown to have negative impacts on wild bee populations in both natural and anthropogenic scenarios (Goulson and Sparrow 2009, Shavit et al 2009, Lindström et al 2016, Torné-Noguera et al 2016, Magrach et al 2017, Ropars et al 2019, Valido et al 2019). I thus formulated the hypothesis that, if the abundance of managed honeybees has been actually increasing in the Mediterranean Basin over the last decades, then a profound biome-wide alteration in the proportional composition of bee pollinator assemblages could be currently underway there, involving a gradual replacement of wild bees by honeybees in flowers.…”

The state of the world’s urban ecosystems: What can we learn from trees, fungi, and bees?

“…Pollinators, on the other hand, have captured the public imagination and their ecological function is well understood by non‐experts. Public enthusiasm for saving bees, however, is almost entirely focused on honey bees with an unsustainable proliferation of urban beekeeping that may actually do more harm to bee conservation than good (Ropars, Dajoz, Fontaine, Muratet, & Geslin, 2019). Furthermore, bee conservation has overlooked the critical contributions of trees through provision of pollen, nectar, and nesting sites (Baldock et al., 2015, 2019).…”

Conservation of species interactions to achieve self‐sustaining ecosystems

“…For example, a common management intervention in Danish national parks is to establish hives of honey bee Apis mellifera for honey production, commonly claimed to have the added benefit of ensuring efficient pollination of native plants (Huryn 1997). However, honey bees may decrease the abundance of native threatened pollinators via competition for floral resources (Ropars et al 2019). If interactions are specialised, such that native insects are more efficient pollinators of native plants, the presence of honey bees may weaken naturally occurring interactions (do Carmo et al 2004), with negative effects on the community and ultimately the long‐term management goals that were the original rationale for establishing the national parks.…”