The impacts of urbanization on pollinator communities in Bergen, Norway

Abstract

This study was conducted in Bergen, Norway in 2022, whereas I investigated the underlying factors of pollinator abundance and the abundance and richness of Bombus (bumblebees). I explored pollinator communities across urban, suburban, and rural sites along with associated habitat characters such as plant communities. The intention was to make a reliable report about both the present and historical status of pollinators in an urban to rural environment.

To collect a variety of pollinators, I used pan traps in blue, white and yellow color and yellow vane traps with blue windows. I found that the rural region had the highest abundance of both pollinator groups and Bombus individuals. Syrphidae (hoverflies) was the most abundant group, while Apocrita (wasps) had the lowest abundance. The numbers were highly variable in urban and suburban areas yet showing that both pollinators in general and bumblebees followed almost the exact same pattern across sites. The suburban area was most sufficiently sampled and exhibited the highest occurrence and richness of Bombus. The abundance and richness of Bombus was highest at the beginning of my study in late June and declined throughout the season. B. pascuorum was the most abundant and most occurring species per site and showed an affinity for rural areas. The most common species in the urban sites was B. pratorum.

Seven sites were compared when looking at correlations between my records and historical records. I found that the association between my species and the sites were explained by similarities in abundance and richness of Bombus, while the old associations were explained by geographical location. Only five of the 44 most abundant plant species were found in all three areas sampled, showing that plant communities had great variety overall. The rural region had the highest richness, and most flowers were purple or pink, suburban areas had the highest abundance and mainly yellow or purple flowers while the urban area has most white flowers and partially yellow. The great variety of flowering plants could potentially maintain richness and abundance amongst pollinators. My study highlights the need for in-depth research on variables that can affect local pollinator communities, as every urbanized area is unique.