Posted: 17 May 2017 08:16 AM PDT
A new study of native bumblebee populations in southeastern Michigan cities found, surprisingly, that Detroit has more of the large-bodied bees than some surrounding, less urbanized locations.The large amount of vacant or idle land in Detroit may boost the bumblebee population by providing nesting sites and flowers for food.
Native bees are critical sources of pollination for agriculture and wild flowering plants. Many native bees are declining in both abundance and diversity, due to various causes that likely include loss of habitat from human activities. While the effects of large-scale agriculture on native bees are relatively well understood, the effects of urban development are less clear.
Bumbleebees belong to the bee genus Bombus. In the study, more than 500 individuals from 10 species were identified at 30 sites in southeast Michigan….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….
….vacant lots are often less frequently mowed and less likely to be treated with pesticides and herbicides. Therefore, these lots can provide various flowering plants and nesting sites for bees.
….By analyzing males and females separately, the U-M researchers found that observed declines in overall bumblebee abundance and diversity with increasing urbanization were entirely driven by declines in female workers, while male abundance and diversity were unrelated to urbanization.
Paul Glaum, Maria-Carolina Simao, Chatura Vaidya, Gordon Fitch, Benjamin Iulinao. Big city Bombus using natural history and land-use history to find significant environmental drivers in bumble-bee declines in urban development. Royal Society Open Science, 2017; 4 (5): 170156 DOI: 10.1098/rsos.170156