Effect of modified green landscape on bee pollinators: a case study at Makerere University Main Campus
Abstract
The loss of flower-rich habitats in urbanized areas has resulted in significant losses of wild
bee diversity in the transformed landscapes that is increasingly threatening the pollination
services and agricultural sustainability. However, the impacts of urbanization on bees remain
poorly understood, thus impeding the formulation of effective policies for bee conservation in
the growing transformed areas. Therefore, the study was conducted to assess effect of
modified green landscape on bee pollinators in Makerere University main campus in three
different sites. Field sampling was conducted in December 2019 and January 2020. Samples
collected were cleaned and stored in vials containing 70% ethanol. Laboratory identification
was done at Makerere University with the aid of standard guides and online resources. A total
of 344 bees were collected comprising 14 genera with bees of genus Apis (70.5%) being the
most abundant and Macropis (0.6%) the least abundant. There was statistically significant
difference in abundance of bees at different level of habitat modification/transformation (χ2 =
63.843, df = 2, p< 0.001) but difference in bee abundance between botanical garden and semi
cultivated land was not significant (p = 0.6), though there were more individuals recorded in
botanical garden than semi cultivated land. The findings show that increasing level of
landscape modification and disturbance in study areas negatively affected bee diversity and
abundance as the highly transformed and intensively managed habitat (road edges) had the
least bee composition and a stable and least transformed habitat (botanical garden) sustained
the highest diversity and abundance of bees. Land scape modification also significantly
negatively affected the flowering plant species richness. Overall bee abundance was
positively related to diversity of plants but there no significant correlation between bee
diversity and plant diversity. In order to conserve the diversity of bees as to optimize
associated pollination services, a diverse habitat mosaic need to be promoted in transformed
landscapes. Future studies should aim to enhance the understanding of plant-pollinator
associations and specific food requirement of different wild bee species for their effective
conservation in urbanized-transformed landscapes.