Bees are in decline, primarily attributed to loss of habitat. Fragmented habitats persist in an agricultural landscape, vulnerable to abandonment and surrounding stressors. Among stressors, concerns have been raised that managed honey bees (Apis mellifera) may competitively displace wild bees in protected areas.
The main objective of this thesis was to investigate whether beekeeping pose a risk to wild bee communities in protected areas of Denmark, specifically semi-natural grasslands and heathlands. Central to this thesis is conservation of wild bees and additional research objectives involve how management of these habitats affect bees and other insects compared to abandonment.
The thesis is based on five papers and across the studies, 52 grassland-heathland sites were investigated. The majority of sites were sampled using traps to assess community
compositions, proportion of honey bees and effects of edaphic variables and management.
The effect of management on nectar resources were assessed on one grassland and on insect communities on four heathlands. Competition was assessed through experimental
introduction of beehives to one of two species rich calcareous grasslands using different methods, e.g. metabarcoding, and on eight heathlands using time-lapse cameras and deep learning.
In total, 140 bee species were found across sites. Management of semi-natural areas had a positive effect on bee assemblages through improvement in floral and nesting resources, while other insect taxa benefitted from prolonged abandonment on heathlands. Honey bees were generally low in abundance on studied sites, even when placed in a species rich grassland. However, honey bees were highly abundant on heathlands during the late-summer flowering of Calluna vulgaris. Only few common species were detected on C. vulgaris and honey bees showed slight negative effect on oligolectic solitary bees and migratory
butterflies.
The predominant threat to wild bees is loss of habitats and with nearly half of Danish bee species found across the studies, the thesis demonstrate the value of preserving and restoring semi-natural grasslands and heathlands as well as the consequences of abandonment. The presented studies do not indicate that managed honey bees constitute a significant threat to wild bees of semi-natural grasslands and heathlands, but it is strongly encouraged to consider the context-dependent potential of impact and assess resource-use of hives if placed near or within protected areas.