Spillover of managed honeybees from mass-flowering crops into natural habitats

Mass-flowering crops (MFCs) and beekeeping are increasing across agroecosystems globally. Managed honeybees could spillover after the blooming of MFCs into nearby natural habitats, especially if hive numbers are associated with the cover of MFCs at the landscape scale. Nevertheless, this phenomenon has been largely overlooked despite the potential impacts of honeybees on local wildlife. We assessed this 'MFC-beekeeping' association and honeybee spillover into woodland patches in 17 fragmented landscapes in SW Spain with contrasting cover of orange groves as MFC. Hive densities were almost four times greater in landscapes with high cover of orange groves and, after the orange-tree bloom, mean honeybee densities were eight times higher in woodland patches within these landscapes, as compared to landscapes with no/low cover. Seemingly, this spillover was resource-mediated since it mirrored the temporal changes in flower cover at habitat and landscape scales. Our study demonstrates for the first time a consistent spillover of managed honeybees from a MFC into nearby natural habitats. These findings are a warning about the potential detrimental effects of magnified honeybee densities on local fauna and flora, especially on wild bees.