Urban Landscape Effects on Bees and Food Production

[摘要] Bees are a critically important functional group, contributing to the pollination of many of the world’s leading food crops and flowering plants, but concern is growing over signals of bee declines. Habitat loss associated with urbanization is thought to contribute to bee decline, but studies show that bees have variable and complex responses to urbanization. This variability has challenged our ability to understand the patterns, function, and management of wild bees in urban landscapes. This dissertation aims to address these challenges by using the patch-corridor matrix model and urbanization gradient analyses to investigate 1) whether bees show variable response patterns to urbanization due to an issue of scale, 2) how urbanization affects the function of pollination in urban agriculture, and 3) the effect of small flower plantings on bee management in urban landscapes. First, I propose that bees show variable response patterns to urbanization due to an issue of scale, more specifically the resolution at which land cover data is measured. To test this, I first review prior studies of urban landscape impacts on bees, and then use remote sensing technology to test whether a shift from coarse- to fine-resolution land cover data reveals new patterns. In the literature review, I find studies continue to show variable results, with most studies finding no significant effects in how urban landscapes impact wild bees. I also find most studies use coarse-resolution land cover data to test landscape effects. When comparing bee response patterns between coarse- and fine-resolution land cover data, I find fine-resolution land cover data reveals patterns that are obscured by coarse-resolution land cover data.Second, I conduct a field experiment to test how urbanization in south-eastern Michigan impacts pollinators and the ecosystem service of food production in urban agriculture. I find that the urban heat island effect affects food production quantity and quality, while the presence of pollinators in gardens affects food production stability. Third, I conduct a final field experiment to test how floral additions of one to ten pots of flowers impact wild bee populations in urban landscapes. I find that small flower plantings can positively impact pollinators in urban areas, although a nonlinear and saturating relationship between flower quantity and bees means that smaller floral additions have higher impacts than large floral additions.At a time when urbanization is projected to continue expanding at rapid rates, and the status of wild bee health is uncertain, this research deepens our understandings of the links between urbanization, wild bee populations, and effects on their ecosystems services and management. To deconstruct the variability seen across past studies, this dissertation underscores the importance of matching scales of measurements to the scales of the biological species of interest. My results also show that bees can act as a stabilizing force in urban agriculture, and that encouraging citizens to plant flowers can be an effective bee management strategy.

[发布机构] University of Michigan

[效力级别] urban

[关键词] bees;urban;urban agriculture;flowers;conservation;resolution;Ecology and Evolutionary Biology;Natural Resources and Environment;Science;Natural Resources & Environment