top of page

The Quarterly Buzz

Updated: Jun 6, 2022

Newsletter of the Native Bee Society of British Columbia June 2022

Volume 3 | Issue 2


Editors-in-chief: C. Thuring & M. Marriott

Contributors: Jennifer Lipka, Sky Jarvis, Christine Thuring, Bonnie Zand, Paula Cruise

Fly Straight to Article:


Research Corner

Flight of the bumblebee: How will rising temperatures affect bumble bees?

by Jennifer Lipka

Editor's note: This column usually features a summary of current research that has captured our attention, translating a scientific paper into language that a lay-person can understand. This edition features something a bit different and no less valuable: a literature review summarizing current understanding of how rising temperatures may affect bumble bees in general.

Lay Summary

Last year, in June 2021, British Columbia experienced an extreme high temperature event called a heat dome. Human induced climate change may increase these temperature events and could result in detrimental impacts to our local pollinators, including bumble bees. While we do not yet have conclusive results regarding the impacts to pollinators as a result of last year’s heat dome, it is important for us to gather the information that we do know regarding how bumble bee’s may be affected by rising temperatures. This short literature review collects relevant articles and summarizes research on what we know about high temperatures and bumble bees. There is still a lot to be learned and more research is needed. It is vital that we look into these questions as climate change continues to impact our weather patterns because bumble bees are not only important to natural ecosystems, they are also important for our food systems.

Literature review

If temperatures are too cold, insects are unable to fly because flight is thermally constrained by the temperature of the thoracic muscle which is attached to the wings (Corbet et al., 1993; Barton et al., 2014). At temperatures higher than optimal, large insects may be at increased risk of overheating during flight (Rubalcaba & OlallaTarraga, 2020). Insect flight is important for a host of ecological functions such as mate finding (Fukaya et al., 2017), dispersal (Guo et al., 2017), and foraging (Lihoreau et al., 2010). For bumble bees, the ability to fly may be an important factor for fitness because insects with decreased flight performance may experience decreased fitness.

Bumble bees are important pollinators because of their ability to ‘buzz pollinate’, which is where they vibrate at a high frequency that dislodges pollen (De Luca & Vallejo-Marin, 2013). This same ability allows them to warm their flight muscles in cooler temperatures for flight (Esch et al., 1991). The minimal thermal limit of bumble bees has been extensively studied (Oyen & Dillon, 2018: Oyen et al., 2016: Owen et al., 2013: Pimsler et al., 2020). While bumble bee response to increasing temperatures has been studied (Oyen & Dillon 2018, Oyen et al 2016), the response to high temperatures is often not the sole focus of the paper.

There is increasing evidence that bumble bees are declining due to climate change (Soroye et al., 2020; Kerr et al., 2015). While there is disagreement over how extreme this decline is or if all bumble bee species are in decline (Guzman et al., 2021), bee species (not specific to Bombus spp.) in decline over the past few decades seem to be the least tolerant of high temperatures (Hamblin, 2017).

Overall, I found seven studies that examined a relationship between temperature and bumble bee foraging activity and provide evidence supporting a decrease in foraging activities with increasing temperatures (Couvillon et al., 2010; Kenna et al., 2021; Kwon & Saeed, 2003; Russell & McFrederick, 2021; Hoover et al., 2012; Torres-Ruiz & Jones, 2012; Vanderplanck et al., 2019). Bumble bees can fly at temperatures as low as 5°C (Corbet et al., 1993) and are well adapted to cold environments as their native ranges include temperate and alpine habitats (Hines, 2008). The average temperature of their native range predicts their ability to tolerate high temperatures, indicating that they are well adapted to the temperatures found in their native environments (Oyen et al., 2016; Pimsler et al., 2020).

The average critical maximum temperature that a bumble bee can endure is 47°C and the average time it took before a bumble bee became unconscious after being exposed to 40°C was 1 hour and 51 mins (Maebe et al., 2021; Martinet et al. 2015; Oyen et al 2016; Oyen & Dillon 2018). The maximum foraging trip time of a bumble bee is up to 1 hour and 56 mins which is longer than the average time it took before becoming unconscious in 40°C temperature (Skyrm, 2011). Climate change may result in an increase in extreme weather events such as heat waves (Otto, 2020). If bumble bees are not able to endure extreme heat events, then this may result in a negative impact of climate change for bumble bees.

A study by Kenna et al. (2021) suggested that increased temperatures may have a positive effect on bumble bees. While this may be true with a minimal temperature change, up to the optimal temperature, there will likely be a temperature at which a threshold will be reached. The temperatures at the poles are experiencing a greater change in temperature due to climate change, termed polar amplification (Wendler et al., 2014). The temperatures in the regions that bumble bees inhabit may rise more than just a few degrees. Climate change may also cause an increase in droughts (Mukherjee, 2018), which might impact floral resource availability (Takkis, 2015).

More lab studies are needed to see how extreme temperatures affect flight and foraging abilities of bumble bees and, how nectar and pollen availability changes due to increasing heat. Additionally, more observational studies are needed during extreme heat events.


Barton, M., Porter, W., & Kearney, M. (2014). Behavioural thermoregulation and the relative roles of convection and radiation in a basking butterfly. Journal of thermal biology, 41, 65-71.

Couvillon, M. J., Fitzpatrick, G., & Dornhaus, A. (2010). Ambient air temperature does not predict whether small or large workers forage in bumble bees (bombus impatiens). Psyche (Cambridge, Mass.), 2010, 1-8.

Corbet, S. A., Fussell, M., Ake, R., Fraser, A., Gunson, C., Savage, A., & Smith, K. (1993). Temperature and the pollinating activity of social bees. Ecological Entomology, 18(1), 17-30.

De Luca, P.A., & Vallejo-Marin, M. (2013). What’s the ‘buzz’ about? The ecology and evolutionary significance of buzz-pollination. Current Opinion in Plant Biology, 16(4), 429-435.

Esch, H., Goller, F., & Heinrich, B. (1991). How do bees shiver? Die Naturwissenschaften, 78(7), 325-328.

Fukaya, M., Kiriyama, S., & Yasui, H. (2017). Mate-location flight of the red-necked longicorn beetle, Aromia bungii (Cleoptera: Cerambycidae): an invasive pest lethal to Rosacea trees. Applied Entomology and Zoology, 52, 559-565.

Guo, K., Lin, H., Su, X., Wang, J., Montalva, C., Shao, S., & Zhou, X. (2017). The spatial–temporal dynamics of bamboo aphid dispersal flight along with their natural enemies: Biocontrol implication. Agroforestry Systems, 93(2), 631-639.

Hamblin, A. L., Youngsteadt, E., López-Uribe, M. M., & Frank, S. D. (2017). Physiological thermal limits predict differential responses of bees to urban heat-island effects. Biology Letters (2005), 13(6), 20170125.

Hines, H. M. (2008). Historical biogeography, divergence times, and diversification patterns of bumble bees (hymenoptera, apidae, bombus). Systematic Biology, 57(1), 58-75.

Hoover, S. E. R., Ladley, J. J., Shchepetkina, A. A., Tisch, M., Gieseg, S. P., & Tylianakis, J. M. (2012). Warming, CO2, and nitrogen deposition interactively affect a plant-pollinator mutualism. Ecology Letters, 15(3), 227-234.

Kenna, D., Pawar, S., & Gill, R. J. (2021). Thermal flight performance reveals impact of warming on bumblebee foraging potential. Functional Ecology, 35(11), 2508-2522.

Kwon, Y.J., & Saeed, S. (2003). Effect of temperature on the foraging activity of bombus terrestris L. (hymenoptera: Apidae) on greenhouse hot pepper (capsicum annuum L.). Applied Entomology and Zoology, 38(3), 275-280.

Lihoreau, M., Chittka, L., & Raine, N. E. (2010). Travel optimization by foraging bumblebees through readjustments of traplines after discovery of new feeding locations. The American Naturalist, 176(6), 744-757.

Maebe, K., De Baets, A., Vandamme, P., Vereecken, N. J., Michez, D., & Smagghe, G. (2021). Impact of intraspecific variation on measurements of thermal tolerance in bumble bees. Journal of Thermal Biology, 99, 103002-103002.

Martinet, B., Lecocq, T., Smet, J., & Rasmont, P. (2015). A protocol to assess insect resistance to heat waves, applied to bumblebees (bombus latreille, 1802). PloS One, 10(3), e0118591-e0118591.

Mukherjee, S., Mishra, A., &. Trenberth, K.E. (2018). Climate change and drought: a perspective on drought indices. Current climate change reports, 4, 145-163.

Otto, F. (2020). Heatwaves, downpours, and more. In F. Otto, Angry weather: Heat waves, floods, storms, and the new science of climate change. Greystone Books.

Oyen, K. J., & Dillon, M. E. (2018). Critical thermal limits of bumble bees (bombus impatiens) are marked by stereotypical behaviors and are unchanged by acclimation, age, or feeding status. Journal of Experimental Biology,

Oyen, K. J., Giri, S., & Dillon, M. E. (2016). Altitudinal variation in bumble bee (bombus) critical thermal limits. Journal of Thermal Biology, 59, 52-57.

Rubalcaba, J., & Olalla-Tarraga, M. (2020). The biogeography of thermal risk for terrestrial ectotherms: Scaling of thermal tolerance with body size and latitude. Journal of Animal Ecology, 89(5), 1277–1285.

Russell, K. A., & McFrederick, Q. S. (2021). Elevated temperature may affect nectar microbes, nectar sugars, and bumble bee foraging preference. Microbial Ecology,

Skyrm, K. (2011). Environmental impacts on native bumble bee pollinators in an agricultural landscape of western Oregon. [Doctoral dissertation, Oregon State University]. Open Collections.

Soroye, P., Newbold, T., & Kerr, J. (2020). Climate Change contributes to widespread declines among bumble bees across continents. Science, 367, 685-688.

Takkis, K., Tscheulin, T., Tsalkatis, P., & Petanidou, T. (2015). Climate change reduces nectar secretion in two common Mediterranean plants. AoB Plants, 7.

Torres-Ruiz, A., & Jones, R. W. (2012). Comparison of the efficiency of the bumble bees bombus impatiens and bombus ephippiatus (hymenoptera: Apidae) as pollinators of tomato in greenhouses. Journal of Economic Entomology, 105(6), 1871-1877.

Vanderplanck, M., Martinet, B., Carvalheiro, L. G., Rasmont, P., Barraud, A., Renaudeau, C., & Michez, D. (2019). Ensuring access to high-quality resources reduces the impacts of heat stress on bees. Scientific Reports, 9(1), 12596-10.

Bio Jennifer Lipka is a MSc.student in Integrated Studies in Land and Food Systems at the Plant-Insect Ecology and Evolution lab at UBC. She has a BA in Geography majoring in Environment and Sustainability. Her academic interests are biogeography, Geographic Information Science, and pollinators! She researches the relationships between plants and pollinators and how they are affected by environmental pollution, climate, and land use change. She condensed this literature review from a longer version written for an Insect Ecology class at UBC.


Native Bees' Needs

Reflecting on No Mow May

by Sky Jarvis and Christine Thuring

No Mow May is a new trend in Canada and, while it's sure to leave our green spaces a bit greener this spring, there is some nuance to understand if we’re serious about supporting native bees. What is #NoMowMay? What happens when you wait a few weeks before taming the wild profusion of spring growth in your yard or garden? Is helping pollinators that simple?

"Overgrown" lawn with "No-Mow May" sign.
Vancouver property observing No Mow May. Image: Lori Weidenhammer

What is No Mow May?

No Mow May is a grass-roots movement inviting homeowners and renters to hold off on mowing, thatching, and general yard/ garden cleanup in the spring. In addition to providing spring forage for early pollinators, No Mow May aims to raise awareness about the role that everyday people can have in the management of private lands. The choices we make around our house and in our gardens can have widespread implications for the plants, animals, and fungi that we share this planet with.

This movement has just started penetrating Canadian society but originated in Europe. There is now a general understanding and agreement on how important springtime is for insect populations who are just emerging or migrating into Northern ecosystems after a long, cold winter. For many of us, waiting a few extra weeks to tend to our lawns may feel like an eternity. The wait may also compound thoughts like, “If I let my lawn go for even just two weeks, it will take me HOURS to get it done!”

Long grass with spring rain.
Is your mower up to the No Mow challenge? Image: Pixabay

#NoMowMay invites us to actively challenge the social norms that have been engraved into us from a young age. I remember the first time my parents paid me $5 to mow the lawn, and how happy I was to go to the store and buy treats for myself! It’s worth also reflecting on the social pressure that comes with a lawn that is perceived to be unkept. Some people in the US have even been sued or fined for not mowing their lawns, we’ve not seen that quality of escalation in Canada. In any case, whether it’s No Mow May or simply maintaining an alternative lawn, it can be difficult to explain to friends, family, and neighbors the significance of holding off on tidying the yard for “some bugs”, wherever you live! Here are some tidbits for educating others about “No Mow May” (or alternative lawns):

  1. Lawns are a social construct of Western Eurocentric societies. Historically, only the wealthiest members of society had elaborate gardens with fresh green lawns. Today, the majority of residential properties include lawns. However, unlike lawns of yore, many lawns today are maintained with chemicals and fertilizers and kept devoid of many plants deemed to be “weeds”.

  2. If it’s not feasible to not mow the lawn in May, consider adjusting the height of your mower all summer long. Many plants put 50% of their biomass into their root system, so the higher you leave the above-ground portion the longer the below-ground counterpart will be. Plants with strong and deep roots are better equipped for drought resistance, and thereby water conservation on your part.

  3. Insects are “cold-blooded” (ectotherms) like reptiles and amphibians, meaning their body temperatures fluctuate with ambient air temperatures. When exposed to cold temperatures, they become sluggish. When spring comes late, like in 2022, such animals need extra time to get up and active. For an early queen bumble bee in a cold spring, proximity to forage can mean life or death.

Pollinator meadow habitat area.
Cold springs can be fatal when forage is distant. Bees need warm conditions to be active. Image: Lori Weidenhammer

Nuance for No Mow May, You Say?

By contrast with the U.K., where No Mow May originated, the nuance for bee lovers in North America relates to the novelty of lawns here, and to the prevalence of dandelion (Taraxacum officinale). Whereas most human settlements in Britain are ancient, Canada is a recent colonial frontier where land development involves imported soils and turf. Whereas the wildflowers that pop up from unmown lawns or verges in England are diverse and often native, the wildflowers that pop up here are often non-native generalists, like dandelion.

Here's the nuance. Firstly, dandelions are successful because their pollen is allelopathic. This means that when dandelion pollen is deposited on the flowers of other species, those plants’ reproductive success is inhibited, with impacts on the entire plant community! Second, dandelions have protein-deficient pollen, which is like junk food for native bees. A meadow of dandelions cannot offer bees and their offspring the nutrition they require for a healthy season. Thirdly, urban dandelions pick up heavy metals, which is more of an issue for organisms higher up the food chain.

Pollen covered bee on dandelion.
Dandelion pollen is protein-deficient and allelopathic. Image: Creative Commons BY-SA 2.0

To be clear, this nuance does not intend to detract from the spirit of No Mow May! Our native pollinators benefit when we:

  • mow less and maintain more flowers;

  • replace dandelions with native plants;

  • replace conventional lawn with organic alternatives, like bee turf;