Background/Question/Methods Residential gardens make up a large percentage of the green area within urbanized areas. If this land is managed with conservation priorities in mind, there is great potential for increasing biodiversity in cities. Recognizing this, programs have emerged to provide residents with knowledge and incentives to grow native plants in their yards. One such program, Bring Conservation Home (BCH), has a tiered certification system that ranks houses based on habitat elements including native plant abundance, invasive species and canopy stratification. Though successful in terms of community engagement, little work has been done to empirically test the effectiveness of the program criteria from a conservation standpoint. To test the hypothesis that a higher certification level leads to higher bee abundance and diversity, we sampled bees monthly in 45 houses enrolled in BCH situated along an urbanization gradient in St. Louis, Missouri, USA. Using a block design, we analyzed bee diversity at houses with different BCH certification levels. After characterizing the habitat by quantifying in-yard floral resources, additional flowers within bee foraging range, and area of impervious surface, we investigated patterns of bee richness and diversity. Results/Conclusions The correlation between BCH certification level and bee diversity varies across the gradient of urbanization. In urban blocks, there was not a significant difference between the rate of bee capture between different certification levels. However, in suburban and exurban areas, uncertified (yet enrolled) gardens have a significantly lower capture rate than the certified groups. Additionally, species accumulation curves indicate the highest diversity is in urban sites, followed by suburban, then exurban neighborhoods. We hypothesize that this difference is partially due to the variation in lot size. In urban areas, where the housing is denser, there are more neighbors within foraging range that may have floral resources, increasing habitat connectivity. In suburban and exurban neighborhoods where the lots are farther apart, there are fewer neighbors within bee foraging range, leading to lower habitat connectivity. These results indicate that in suburban and exurban neighborhoods, BCH criteria are adequate: higher certified houses have more bee diversity. However, they also suggest that to better support bees in residential areas, conservation organizations should target enrolling homes and improving habitat and connectivity in suburban and exurban neighborhoods.
