One-year-old flower strips already support a quarter of a city's bee species

To combat the loss of flower-rich meadows, many cities are supporting greening measures, including the creation of flower strips. To assess the effectiveness of these measures in supporting flower-visiting insects, their faunas need to be compared to the background fauna at various distances from the flower strips. To meet this goal, we quantified the bee faunas of nine 1000 m2-large and newly established flower strips in the city of Munich, all planted with a regional seed mix, and compared them to the fauna recorded between 1997 and 2017 within 500, 1000, and 1500 m from the respective strip. The 68 species recorded during the flower strips' first season represent 21% of the 324 species recorded for Munich since 1795 and 29% of the 232 species recorded between 1997 and 2017. Non-threatened species are statistically over-represented in the strips, but pollen generalists are not. These findings illustrate the conservation value of urban flower strips for common species that apparently quickly discover this food source. To our knowledge, this is the first quantitative assessment of the speed and distance over which urban flower strips attract wild bees.