The University of Michigan students who conducted the study suspect that the large amount of vacant or idle land in Detroit may boost the bumblebee population by providing nesting sites and flowers for food.

There is certainly a correlation between Bumblebees and other native bees, and the introduced honeybee populations that us beekeepers are caretakers for.

Bumblebees need to nest in less-disturbed areas with bare ground, tall grass or abandoned tree stumps, making them a good candidate for testing the effects of urban land development. Handheld nets and insect traps were used to capture the bees.

Read more here: Phys.org :: Bumblebee populations higher in Detroit than in some less-urbanized areas; vacant lots could be a factor