Wild bee abundance and diversity on organic vegetable farms in response to local landscape factors

Graduate Student: Kathryn J. Prince, Departments of Entomology and Agroecology, University
of Wisconsin-Madison ([email protected])

Faculty Advisor: Dr. Russell L. Groves, Department of Entomology, University of Wisconsin-
Madison ([email protected])

Project Period: 2015

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Agricultural intensification has been linked to the decline of pollinators like bees. Organic farms often support a richer wildlife community than conventional farms, and help provide necessary pollinator habitat in intensively farmed, homogeneous areas. Central Wisconsin represents such an intensively farmed area, but the landscape is far from homogeneous. Conventional rotations of processing vegetables with varying degrees of pollinator dependence are grown in high concentrations in this region. The suitability of central Wisconsin as pollinator habitat, both within the bounds of organic farming operations and in the surrounding landscape, has not been well studied. This project’s aims were to quantify the bee species living in central Wisconsin and determine whether organic farms located in this area influence local pollinator communities as compared to marginal lands in the same region. We surveyed the seasonal abundance, diversity, and species richness of a small-scale organic vegetable farm, a large-scale organic vegetable farm, and of semi-natural conventional vegetable field margins during the 2015 growing season. The large-scale and small-scale organic farms bore no significant differences in bee community metrics, though each harbored several unique bee species. The organic sites did not differ from semi-natural edges in abundance or diversity, but had significantly higher species richness. These results suggest that organic farms in agriculturally intensive but heterogeneous regions may harbor a higher number of bee species, but the overall diversity of the bee population and number of bees is no different than in surrounding unmanaged lands. Organic farmers in such a landscape who wish to conserve wild bee pollination on their property, regardless of their operation’s scale, would do well to focus on improving local habitat features to increase overwintering abundance and diversity while recognizing that their farm’s bee community is also affected by surrounding land uses.

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