How does urban beekeeping affect native wild bees?

Beekeeping in vibrant urban cityscapes has brought bees, including nearly 4,000 native species, into the spotlight. These native bees, residing across the United States, are largely responsible for pollination in our agricultural, urban, and natural landscapes.

However, the narrative becomes more complex when non-native honey bees, managed and domesticated, are added to the equation.

Urban beekeeping and native populations

Initial concerns were that managed honey bee populations may have negative impacts on native wild bees, mainly due to potential resource competition and disease sharing.

However, a comprehensive study by researchers at the Pennsylvania State University points to a different pattern – one that might not be as adverse.

The findings reveal that out of 33 genera of native bees studied, only a few showed any negative impact triggered by the presence of honey bees.

Vulnerable bee species identified

The research sheds light on the groups of bees that are potentially more vulnerable to the effects of urban beekeeping, which will aid in devising conservation strategies.

The researchers identified a correlation between managed honey bee apiaries, urban land, and the reduced number of bees from six of 33 wild bee genera. The team set out to disentangle the relative influence of apiary density versus developed land.

The six bee genera responded differently to apiary density and urbanization. Long-horned bees in the genus Svastra were most affected by apiary density, whereas Florilegus, another breed of long-horned bees, was most negatively impacted by urbanization.

Other affected genera included green bees (Agapostemon and Augochlora), sweat bees (Lasioglossum) and long-horned bees (Melissodes).

A deeper analysis of the data revealed that the bees most disrupted by apiaries and land development share some common traits: they tend to nest in the ground, forage later in the season and, in some instances, specialize in specific seasonal flowering plants.

Urban challenges for bees

Study lead author Gabriela Quinlan is a U.S. National Science Foundation (NSF) postdoctoral research fellow in Penn State’s Center for Pollinator Research and the College of Agricultural Sciences.

“Urban environments can be especially challenging for ground-nesting bees because the hardscaping – asphalt and concrete – can make it difficult to find bare ground for nesting,” said Quinlan.

“Small bees can’t fly very far, so they may have trouble finding nesting and flowering resources within their flight range. Moreover, specialist bees require very specific flowers, which may be difficult to find in urban settings.”

Quinlan explained that some wild bees also forage later in the season, which happens to be when honey bee colonies are at their peak size and competing for limited floral resources. 

Solutions for urban beekeeping challenges

“Planting late-season forage and leaving bare ground as nesting resources in urban gardens could help alleviate some of the stressors that developed land and urban beekeeping can put on these bee groups,” noted Quinlan.

For the investigation, the researchers used the locations of nearly 4,000 registered apiaries across Maryland to build a state map of apiary density. They then compared this with data on wild bee populations within the state, collected by the U.S. Geological Survey’s Bee Monitoring and Identification Lab.

A declining number of pollinators – linked to pesticide use, pathogens, poor nutrition, and climate change – has caused global concern in recent years.

There is also increased attention focused on how honey bees, carrying pathogens and heightening resource competition, might be affecting wild, native bees.

Urban beekeeping and wild bee abundance

Despite these concerns, evidence to show how honey bees affect the abundance of wild bees has been scarce. The Penn State study sought a deeper understanding of how the presence of managed honey bee populations may relate to reductions in wild bee abundance.

The interconnectedness highlighted by the research prompts a shift in perspective – instead of focusing on individual species, it’s crucial to consider bees as communities.

Nonlethal, automated monitoring systems for bees are being developed by the new INSECT NET graduate training program at Penn State for future studies.

In the meantime, one of the best ways to support both wild and managed bees is to bolster our landscapes with more flowering plants, including city streets and backyards.

Beekeepers can boost honey bees’ resilience to climate variation by skillfully managing pests and diseases within their colonies, consequently reducing the odds of honey bees spreading diseases to wild bees.

The study is published in the journal Science of The Total Environment.

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