Bumble Bee Abundance in New York City Community Gardens: Implications for Urban Agriculture

A variety of crops are grown in New York City community gardens. Although the production of many crops benefits from pollination by bees, little is known about bee abundance in urban community gardens or which crops are specifically dependent on bee pollination. In 2005, we compiled a list of crop plants grown within 19 community gardens in New York City and classified these plants according to their dependence on bee pollination. In addition, using mark-recapture methods, we estimated the abundance of a potentially important pollinator within New York City urban gardens, the common eastern bumble bee (Bombus impatiens). This species is currently recognized as a valuable commercial pollinator of greenhouse crops. However, wild populations of B. impatiens are abundant throughout its range, including in New York City community gardens, where it is the most abundant native bee species present and where it has been observed visiting a variety of crop flowers. We conservatively counted 25 species of crop plants in 19 surveyed gardens. The literature suggests that 92% of these crops are dependent, to some degree, on bee pollination in order to set fruit or seed. Bombus impatiens workers were observed visiting flowers of 78% of these pollination-dependent crops. Estimates of the number of B. impatiens workers visiting individual gardens during the study period ranged from 3 to 15 bees per 100 m of total garden area and 6 to 29 bees per 100 m of garden floral area. Of 229 B. impatiens workers marked, all recaptured individuals (45%) were found in gardens where they were initially marked. These results indicate an abundance of B. impatiens workers within New York City community gardens and suggest that, at least for certain time periods, many individual workers forage within single gardens. Both findings suggest that B. impatiens may be an especially important pollinator of several common crops grown within community gardens and other urban green spaces that are used for agricultural production. Studies of other pollinating insect species in urban habitats as well as the relationship between pollen movement and seed or fruit set will complement the findings of this study.