So what happens in heavily urbanized settings like New York City where buildings and roadways fragment the landscape, leaving small gardens and city parks as the last remnants of urban biodiversity?
A new study in the journal Urban Ecosystems addressed the issue of bee and butterfly diversity within Harlem and the Bronx, where community gardens are a form of nature preserve for these insects.
Despite the isolation from traditional nature, city residents can interact with their own local species through community garden maintenance. Many of the plants grown in these gardens - cucumbers, tomatoes, rasberries, etc. - are linked to pollinator activity, and larger yields of these crops could benefit inner city residents.
Furthermore, the authors argue that the presence of “charismatic microfauna” like these colorful pollinators could prevent what they describe as “the extinction of the ecological experience”.
The authors of this study examined 18 community gardens distributed in the Bronx and East Harlem, addressing factors such as sunlight, total garden size, tree canopy cover, presence of paths, and floral and vegetable areas. Bees were collected by hand-netting and bowl-traps, and butterflies were counted by eye.
The study documented 24 species/taxa of butterflies and 54 species of bees. This seems like a pretty high number for such an urbanized area. The study also encountered wide variation in species diversity among gardens.
The authors found evidence that high floral area per garden provided the greatest positive influence on bees and butterflies.
Bees in particular were more responsive to total garden area and the presence of wild areas within the garden, as their less mobile lifestyle requires them to nest near nectar sources.
Tall buildings had a negative impact on all gardens by obstructing sunlight.
Recognizing that the abundance of flora and sunlight are constraining factors on pollinator diversity, the authors suggest rooftop gardens may be a key compromise uniting urban development with sustainable insect habitat.
Future research involving urban gardens could be extended to include city residents as “citizen scientists”, exposing them to their local ecological systems.
by Alexis Mychajliw
Matteson, K., & Langellotto, G. (2010). Determinates of inner city butterfly and bee species richness Urban Ecosystems DOI: 10.1007/s11252-010-0122-y