Habitats Heterogeneity Affects Bee Species Assemblage in an Urban Green Space: A Case Study of Nairobi Museum Botanic Garden, Kenya

Abstract

The conversion of natural landscapes into human-dominated areas has been identified as one major threat to the existence of biodiversity. However, properly managed anthropogenic biomes can act as areas of biodiversity conservation with the potential to provide ecosystem services similar to those obtained in natural habitats. Classic examples are botanic gardens that have become popular in urban centres as examples of nature-based solutions to landscape loss and degradation. To assess the importance of botanic gardens as biodiversity habitats, a study was carried out in the Nairobi Museum Botanic Garden (NMBG). Bees were sampled using pan traps and sweep nets in four habitats classified as gardens, including the Herbal Garden (HG), Memorial Garden (MG), Succulent Garden (SG), and Quarry Garden (QG). A total of 286 individual bees were collected, with MG having 83 individuals, QG (75), SG (66), and HG (62). Though HG recorded the lowest abundance of bees, it recorded the highest number of bee species (14), MG (13), SG (12), and QG (5). The diversity of bees was highest in the HG (H’=1.89), SG (1.88), MG (1.67), and QG (1.15). Meanwhile, high bee abundances and richness were strongly correlated with diverse flowering plants per habitat, with HG having the highest number of flowering plants (23), MG (16), SG (13) and QG (7). The study found that different flowering plants provided habitats that supported unique assemblages of bee communities, a scenario attributed to enhanced habitat heterogeneity. The findings demonstrated that botanic gardens can act as important habitats and refugia for bees in human-dominated landscapes. Therefore, the establishment and conservation of botanic gardens in urban areas is one way to contribute to Sustainable Development Goal 11 of ensuring sustainable cities and human settlements