Kevin Welzel Pollination by Native Bee Communities in Berkeley, California Spring 2010 1 Urban Agriculture and Ecosystem Services: Pollination by Native Bee Communities in Berkeley, California Kevin Welzel ABSTRACT Managing ecosystem services such as pollination are vital to human survival. As a result of recent declines in European honey bee population from CCD, the agricultural industry and researchers are interested in finding alternative means of pollination. Considering the declines in the European honey bee, urban agricultural may have to rely on native bee pollination to meet their pollination needs. Squash, tomato, strawberry and sunflower plants, each having a 3 by 3 foot quadrat, were observed in two urban agriculture sites located in Berkeley, California. Data collected from both sites include; isolation from natural habitat, diversity of pollinators and visitation rates. I hypothesized that the Oxford study site would have higher native bee diversity and visitation rates than the Berkeley Youth Alternative study site, because the Oxford study site was closer to natural habitat. The community statistics gave mixed results for genus richness and evenness. The t-test indicated no significance of visitation rates for each plant type between each site. Results indicated that close proximity to natural habitat had no affect on native bee visitation rates to crops. The three factors expected to contribute to a healthy native bee population are: common floral resources between native and non native habitats, habitat fragmentation and age of gardens. City planners and conservationist should be cognizant of these factors in order to build an urban agricultural site that can provide food and sustain biodiversity. KEYWORDS Native bees, urban agriculture, ecosystem services, honey bees, CCD, BerkeleyKevin Welzel Pollination by Native Bee Communities in Berkeley, California Spring 2010 2 INTRODUCTION Bees provide a pollination ecosystem service to many agricultural systems. Ecosystem services, defined as species interacting within their environment and functioning together to sustain life (Costanza et al. 1997), are critical to human survival (Daily 1997). Animal pollinators pollinate one third of the United States’ food supply (USFSRMBP 2007), of these, bees are the most abundant and beneficial crop pollinators (Delaplane & Mayer 2000). American farmers rely solely on honey bees (Apis mellifera) to pollinate their crops, often importing honey bees specifically for their pollination services (Delaplane & Mayer 2000). Presently, honey bees provide fifteen billion dollars in added agricultural revenue (USDA 2008). However, recent declines in honeybee populations from Colony Collapse Disorder (CCD) have left the agricultural industry and researchers looking for an alternative. Currently, large-scale agricultural production is declining because of the honey bee’s susceptibility to CCD (Winfree et al. 2007). The symptoms associated with CCD are the disappearance of all or the majority of honey bees from the hive, leaving only the live queen, yet no dead honey bees in or near the hive (USDA 2008). Supplementing the honey bee pollination service with a variety of native bee species would provide insurance against future declines in agricultural production wrought by CCD. (Winfree et al. 2007) Native bees, which are unmanaged, are generally more numerous and diverse near natural habitats have been shown to provide pollination services to various crops (Kremen et al. 2002, Klein et al. 2003, Ricketts 2004), and are just as effective at large scale-pollination as the honey bee (Kremen 2004 Kremen et al. 2007, Williams & Kremen 2007). Studies in agricultural landscapes have shown that native pollinators are more effective when they are close to natural habitats. Ricketts et al. (2004) found that native bee diversity and visitation rates are significantly greater in coffee fields that are near tropical forests than other fields that are further away. Kremen et al. (2004) found that farms that were within a 2.4 km radius of areas with forty percent or more natural habitat were able to rely solely on native bee communities for pollination. Additionally, Ricketts et al. (2008) found strong evidence that increased isolation from natural habitat results in a decline of native bee visitation rates. There are many studies showing the relationship between distance and pollination in commercialKevin Welzel Pollination by Native Bee Communities in Berkeley, California Spring 2010 3 agriculture, but not in urban agriculture. Ultimately, there is the potential for native pollinators to play a large role in urban agriculture, but we don’t know how effective they will be in this very different landscape – one with presumably less native habitat nearby. The purpose of urban agriculture is to provide healthy food to urban food deserts, to revitalize neighborhoods, and to provide environmental justice and ecosystem health (McClintock 2008). Urban agriculture is the process of utilizing sustainable agricultural techniques in an urban environment in order to produce food, while a food desert is an area in an inner city that lacks food retailers (McClintock 2008). Urban agriculture has been on the rise in many urban areas including Oakland California, where the city council has mandated that thirty percent of all food in Oakland must come from a local source such as urban agriculture by 2015 (Green 2007). As agriculture becomes more prominent in urban settings, the need for pollination services by bees also increases (Green 2007). Considering the losses of honey bees, native bees can be utilized to meet the growing demand for pollination service in urban areas. Incorporating resources for native bees into urban agriculture will promote urban ecosystem health in such ways as providing viable seeds and fruits for insects, birds, and other wildlife (Delaplane & Mayer 2000), while in turn providing urban neighborhoods with sustainable nutritious food. In order to achieve these goals as well as gain further knowledge of how the pollination service works, it is important to understand the relationship between the distance of the native bee habitat from the site of pollination and the rate of pollination in these urban settings. The purpose of this study is to examine native bee pollination in two urban agricultural sites that differ in their proximity to natural habitat.
View Full Document
Unlocking...