Introduced bumble bee species thrives, causing concern about native pollinators in Lower Mainland

To the untrained eye, bumble bees may all seem the same: striped, fuzzy and charming. But ecologists in the Lower Mainland have observed a potentially concerning change in the types of species found in the area.

Recent research from UBC’s Plant-Pollinator and Global Change (PPGC) Lab revealed notable decreases in the local western bumble bee population, with a non-native species dominating the area.

The common eastern bumble bee — or Bombus impatiens — was first introduced to the region in the 1990s to pollinate in greenhouses. Melissa Platsko, a recent MSc graduate from the PPGC Lab, said recorded sightings started in 2003.

Since then, B. impatiens has become one of the most popular species of bees in the region, making up as many as “about 40 to 50 per cent proportionally of the bees” Platsko and her team catch in surveys.

Part of what has allowed this species to thrive is its generalist nature. Its home range spans from Nova Scotia all the way down to Florida, meaning B. impatiens is able to thrive in a wide range of temperatures and climates, including the Lower Mainland.

Although a close relative of the native western bumble bee, the common eastern bumble bee has a few key differences. They have a unique biological rhythm to other bumble bees in the region that has allowed them to thrive, with their population peaking in around mid August.

“This late peak in abundance means they're probably using resources the other bumble bees really can't access or use themselves,” said Platsko.

New bees can introduce new pests and pathogens that could overwhelm local bees' immune systems. They also compete for resources, which include flowers as well as nesting space.

Platsko’s thesis is about the types of flowers and plants that the different bumble bees in the Lower Mainland pollinate. Using a classification of invasive plants in BC, Platsko found B. impatiens tends to pollinate weeds and other invasive species more often than other bumble bees, leading to potentially widespread consequences on local floral communities.

More research is still required to unpack the change in bumble bee population. Unlike honey bees, bumble bees have colonies instead of hives, which makes them more difficult to track down.

Platsko highlighted BC’s Community Bumble Bee Project, which is working towards characterizing the bees in BC and identifying endangered species, with the help of volunteers.

“It's really important that we do this research so we can track where these endangered bees are, what habitats they're in, if they're preferential to specific native flowers,” said Platsko. “If anything, my life would have been made a lot easier if we had a lot more historic surveys like this.”

Zooming out, BC is home to around 600 different species of bees. Most are part of a large and diverse group called solitary bees, which are also important pollinators but get less attention than bumble bees or honey bees.

“People really love pollinators," said Platsko. But, there aren't many places for people to learn about BC's specific ecosystem so they can protect it.

In terms of ways to get involved, Platsko encouraged individuals to go to local pollinator events, such as UBC Farm’s Pollinator Walks and Bee Safaris, to learn about bees in the Lower Mainland as well as to native garden events where people can learn about and plant local flowers that can support all pollinators in the region.

“Just becoming more knowledgeable about these bumble bees and other bees that are around you is widely beneficial, more than people realize.”