Research & reports

Rachel A. Brant, Gerardo R. Camilo · Insects · United States (Chicago)

Body size variation in female Halictus ligatus sweat bees collected from Chicago, Detroit, and Saint Louis between May and October 2016 was compared. Head width and intertegular distance were measured in bees collected from community gardens and urban farms. ANCOVA analysis indicated significantly different body size ranges across the three cities, and temperature also had a significant influence on body size.

Rachel Wilson · Science and Children · United States

As part of a school garden project, second graders in the United States participated in integrated lessons exploring ladybug life cycles, culminating in the release of beneficial insects in our school garden. The unit aimed to connect life cycle concepts to a new organism, using a 5E format and integrating language arts activities. This approach met both science content objectives and English Language Arts standards.

Becky Griffin, S. K. Braman · Journal of Entomological Science · United States

In 2017 and 2018, gardeners at 36 locations across 21 Georgia counties, United States, volunteered for the Georgia Pollinator Census pilot project, counting insects in September and October on an aster species and one other participant-chosen plant species (28 plant taxa were selected in total) while also receiving training in insect identification. Bumble bees, honey bees and wasps were sighted more often in rural areas, while carpenter bees, flies and other insects were sighted more often in urban areas; participants also showed increased entomological interest and insect knowledge, and the pilot's results were used to refine criteria for a larger, state-wide census.

Kristen R. Birdshire, Adrian L. Carper, Christy E. Briles · Urban Ecosystems · United States

A study examined bee community responses along a high-plains semi-arid urban-rural gradient in Denver, Colorado, United States, using percent impervious surface across 12 sites to define urbanization extent and combining field assessment with geospatial analysis of local and landscape characteristics; wild bees were collected and analyzed against urbanization using linear modeling. Bee abundance and diversity decreased with increasing urbanization, indicating a negative impact of urban areas on bee communities. All bee guilds responded positively to local floral richness and negatively to landscape-level urbanization, suggesting a shared response pattern across bee types.

Bennett A.B., Lovell S. · PLoS ONE, 14(2):e0212034 · United States (Chicago)

A study of 19 urban agricultural sites in Chicago examining how surrounding land cover (landscape scale) and on-site design (local scale) shape bees and pollination services. Bee responses varied by body size and nesting habit: increasing impervious cover lowered bee richness and reduced pollination services, while more local floral area boosted small soil-nesting bees. It recommends minimizing impervious cover at large scales and adding floral resources locally so urban agriculture can conserve pollinators in the surrounding ecosystem.

Stacy M. Philpott, Simone Santos de Albuquerque, Peter Bichier, Hamutahl Cohen, Monika Egerer, Claire Kirk, Kipling Will · Insects · United States (California)

This study examined local and landscape factors influencing ground beetle (Carabidae) activity, species richness, and traits in 19 community gardens in coastal California. Gardens with higher crop richness and agricultural surroundings showed greater carabid activity density, but species and functional group richness did not respond to these factors. Gardens with more leaf litter had lower carabid activity but tended to have larger carabids, indicating both local and landscape factors influence carabid communities.

Gordon W. Frankie, Ingrid Feng, Robbin W. Thorp, Jaime C. Pawelek, Marissa H. Chase, Christopher C. Jadallah, Mark Rizzardi · Journal of Pollination Ecology · United States (California)

An extensive survey of bee-flower collection records from 10 California cities between 2005 and 2011 examined diverse bee species visiting native and non-native ornamental plants. A total of 7,659 bees were examined, identifying 229 bee species visiting both native and non-native plant types. Native bee species were common on both plant types, but substantially more non-native bee species visited non-native plants compared to native plants.

Rachel E. Mallinger, Anne Yasalonis, Gary W. Knox, Wayne Hobbs · EDIS · United States (Florida)

This 7-page fact sheet aims to conserve approximately 315 species of native wild bees in Florida. Published by the UF/IFAS Entomology and Nematology Department, it shows how gardeners and land managers can aid bee conservation efforts by planting flowers in home or community gardens.

Kimberly M. Ballare, John L. Neff, Rebecca Ruppel, Shalene Jha · Ecological Applications · United States

This study assessed bee community composition at 20 grassland and 20 agriculture sites across two US metroplexes over three time periods, identifying 172 species from nearly 13,000 specimens. It found that regional land use differentially impacted bee abundance and diversity depending on local habitat management. Local bare ground and floral richness were significantly related to multiple metrics of bee diversity.

Monika Egerer, Jacob M. Cecala, Hamutahl Cohen · Sustainability · United States (California)

This study compared the effects of local and landscape features on wild bee species abundance and richness in 19 gardens and 11 nurseries in California, USA. Local features such as floral richness and ground cover, and landscape features like impervious land cover, were assessed. In gardens, floral richness, local habitat size, and urban land cover impacted wild bee species richness, while in nurseries, floral richness and the proportion of native plant species impacted wild bee abundance and richness.

Sarah Lovell · · United States

This record is a dataset description accompanying a PLOS ONE manuscript by Bennett and Lovell (2019) on landscape and local site variables and pollinators in urban agricultural sites; the data consist of the percentage of each bee pollinator group recorded in bee bowls and through direct observation.

Heidi Liere, Monika Egerer, Stacy M. Philpott · Journal of Urban Ecology · United States (California)

Ladybird beetles (Coleoptera: Coccinellidae) were collected from 19 community gardens across three counties of the California Central Coast during June to September of 2014 and 2015. Of the 19 species collected, only three were non-native to California (three specimens could not be identified to species). Similarity in species composition between gardens was not related to geographic distance, indicating no dispersal limitation among these mobile beetles. Instead, three landscape-level and seven garden-scale variables correlated with changes in community composition, and garden management practices such as ground cover altered the taxonomic and functional makeup of the ladybird beetle community.

Gail Ann Langellotto, Andony Melathopoulos, Isabella Messer, Aaron Anderson, Nathan McClintock, Lucas Costner · Sustainability · United States (Portland, Oregon)

This study sampled bees from gardens in the Portland, Oregon metropolitan area and estimated typical foraging distances to assess whether urban gardens might supply pollination services to surrounding agricultural land. It estimates that when pollination-dependent crops are nearby, 30–50% of the garden bee community could potentially provide pollination services to adjacent crops, suggesting urban gardens could provision neighboring farms or serve as a refuge for pollinators.

Chatura Vaidya, Kaleigh Fisher, John Vandermeer · Sustainability · United States

A study placed experimental bumblebee nests at 10 sites (nine of them community gardens) across an urbanization gradient (0-99% urbanization) in the United States to assess the effects of urbanization on colony development and reproductive success. Reproductive success and colony size were positively correlated with the nests' cumulative weight gain (p < 0.05), but the degree of urbanization had no significant effect on population growth rate or forager activity (p > 0.05). Growth rate was strongly negatively affected by the abundance of wax moth larvae (p < 0.05) and positively correlated with parasite diversity (p < 0.05) and the number of foragers entering the nest (p < 0.01). The study concludes that both bottom-up and top-down effects are equally important for pollinator population dynamics.

Horta das Corujas · Horta das Corujas (blog oficial) · Brazil

The official blog of Horta das Corujas, a volunteer-run community garden on Praça das Corujas in the Vila Beatriz neighborhood of São Paulo. Opened on September 29, 2012, the roughly 800 m² garden practices agroecological vegetable and herb cultivation, restores a local spring, keeps bees, and hosts school environmental-education visits. It operates without formal permits, run by volunteers, with about 10-15 people regularly active.

Monika Egerer, Courtney Arel, Michelle D. Otoshi, Robyn D. Quistberg, Peter Bichier, Stacy M. Philpott · Journal of Urban Ecology · United States (California)

This three-year study in 19 urban community gardens on the California central coast examined how urban landscape intensification and diversity influence the abundance and richness of five arthropod groups (ants, bees, ladybeetles, parasitoids, spiders) across six spatial scales (200 m to 5 km). All arthropod groups were influenced by landscape factors, but this influence varied with spatial scale and local habitat features, likely due to arthropod community interactions and life history strategies.

Edward Lagucki, Justin Burdine, Kevin E. McCluney · PeerJ · United States (Toledo, Ohio)

This study investigated associations between urbanization and flying arthropod communities in 30 gardens and parks in Toledo, Ohio, during July and August 2016, collecting 2,369 individuals across nine orders using elevated pan traps. Flying arthropod community composition was associated with percent impervious surface and canopy cover. Overall abundance was negatively associated with impervious surface and positively with distance to city center, with specific taxa showing similar responses, indicating urbanization reduces taxa important for urban agriculture.

Étienne Normandin, Nicolas J. Vereecken, Christopher M. Buddle, Valérie Fournier · PeerJ · Canada

This study collected 32,237 wild bee specimens (200 species, 6 families) from 46 sites in Montreal and Quebec City in 2012 and 2013, across cemeteries, community gardens, and urban parks. It demonstrated that cities are home to diverse communities of wild bees, which in turn affect bee community structure and dynamics. Community gardens specifically harbored high levels of functional trait diversity, suggesting a substantial contribution to urban pollination services.

Gerardo R. Camilo, Paige A. Muñiz, Michael Arduser, Edward M. Spevak · Journal of the Kansas Entomological Society · United States

A three-year survey (2013-2016 growing seasons) in St. Louis, Missouri, USA, sampled bees by aerial netting across vacant lots, city parks, community gardens and urban farms, collecting over 7,700 specimens, supplemented with BioBlitz data, personal collections, museum-collection records and the literature. The survey identified 198 bee species from five families in the city, of which only nine were non-native, and found St. Louis hosts nearly 45% of Missouri's bee diversity, a proportion the study describes as likely making it one of the most species-rich cities relative to its state's total bee fauna in the country.

Benjamin Iuliano, Alexandra Markiewicz, Paul Glaum · Michigan Journal of Sustainability · United States

A paper examining how community gardens have spread amid a decade of increased urban agriculture in American cities, and what effects this has on local ecosystems, with the title indicating a focus on potential effects on native pollinators. It states that socio-economic demographics may influence patterns of garden placement and quality, producing changes in biotic communities that urban ecologists are only beginning to understand. The available abstract breaks off while introducing a researcher hypothesis about increased floral resources, without stating further specific results.

Stacy M. Philpott, Peter Bichier · Ecological Applications · United States (California)

The influence of local, garden-scale factors (herbaceous and arboreal vegetation abundance and diversity, ground cover) and landscape-scale factors (landscape diversity and surrounding land use) on predation services was examined in 19 urban gardens on the California central coast. Sentinel pests — moth eggs and larvae and pea aphids — were placed on greenhouse-raised plants in open plots versus bagged, predator-exclosure plots. Predation rates were high, with 40% to 90% of prey items removed in open treatments. Predation services varied with local and landscape factors, but significant predictors differed by prey species: predation of eggs and aphids increased with vegetation complexity in gardens, while larval predation declined with vegetation complexity. Smaller gardens experienced higher predation, likely due to greater predator abundance, and several ground cover features influenced predation services. In contrast to patterns in rural agricultural landscapes, aphid predation declined as landscape diversity increased.

Robyn D. Quistberg, Peter Bichier, Stacy M. Philpott · Environmental Entomology · United States (California)

This study investigated bee abundance and species richness in 19 urban community gardens on the California central coast using aerial nets and pan traps. Researchers found 55 bee species and identified that local factors, such as garden size, floral abundance, mulch cover, bare ground, and grass, were generally more important correlates than landscape factors. Medium bees were less abundant in areas with more medium-intensity developed land within 2 km.

Andrea Burr · Consilience · United States (St. Louis, Missouri)

This interdisciplinary pilot study in St. Louis, Missouri, USA (2013-2015) investigated relationships between pollinator health and urban land-uses. Wild bees were sampled weekly at urban farms, community gardens, and prairie pockets, and ethnographic interviews were conducted with 30 decision-makers in summer 2015. Informants described bees' role in crop yield and reported planting to attract pollinators, suggesting the city is viable for pollinator habitat.

David M. Lowenstein, Maryam Gharehaghaji, David H. Wise · Environmental Entomology · United States

A study at 28 urban food-production sites in the Midwestern United States measured the removal of sentinel eggs and larvae of the cabbage looper (Trichoplusia ni) by predators over a 3-day period. Predators removed 50% of eggs and 25% of larvae, with mortality rates not predicted by landscape factors and similar across residential gardens, community gardens, and farms. Laboratory assays confirmed that lady beetles, spiders, and pirate bugs consumed eggs and larvae at high rates.

Lowenstein D.M., Matteson K.C., Minor E.S. · Oecologia, 179(3):811-821 · United States

A study measuring wild bee diversity and cucumber pollination (a pollination service) across urban Chicago. Sites with more bee species had better pollination, and even densely populated residential areas supported high bee richness. It demonstrates that growing diverse flowers in urban gardens sustains pollinators and directly benefits urban agricultural yields.