It is well known that climate change is impacting various activities of Maritime beekeeping. In the past few years, beekeepers report having sent hives to pollination earlier than anticipated, inconsistent forage patterns throughout the summer, feeding bees late into the fall, and additional pressure of pests and diseases. Additionally, research suggests that there is a correlation between high autumn and winter temperatures within Northern climates and greater colony loss. Although there are many impacts of climate change on beekeeping to discuss, this week’s blog will focus on how increased temperatures can affect colony winter survival.

How can Climate Change Impact the Overwinter Survival of Honey Bees

Research conducted in 2022 investigated temperature-eligible flight times of honey bees across Canada using 40 years of weather station data (1980 to 2020) ¹. In order for honey bees to fly they need temperatures ranging between 13^◦C and 38^◦C, sunlight, low wind and minimal precipitation¹. In this study, flight hours were calculated by determining the maximum and minimum value range of sunlight and temperature that are required for honey bee flight¹. Researchers demonstrated that honey bee flight hours have increased significantly over the past 40 years across Canada. On average, there has been an 8% increase in flight hours across Canada over the past 40 years¹.

The research suggests that warming temperatures are contributing to more flight time for honey bees. Now this could be beneficial allowing greater opportunity for bees to forage, but the warming temperatures are also likely impacting plant bloom times and species distribution, and there may also be increased pressure of pests and diseases. Therefore, beekeepers must prepare to modify practices to accommodate possible plant-pollinator mismatches and timings for pest and disease management¹. The mentioned challenges that arise during the summer months certainly can impact winter survival of honey bees, but there are other factors to consider of how increased fall and winter temperatures can affect colony winter survival.

New research supports that warm falls and winters can significantly reduce honey bee overwintering survival². To start, an increase in honey bee flying days throughout the fall and winter can lead to depleted food reserves. If a colony is significantly active throughout the fall and winter, when no forage is available, they are at risk of starving during the winter months. Additionally, late-season flight of honey bees alters the overwintering colony age structure, skews the population towards older bees, reduces colony size, and leads to greater risks of colony failure in the spring².

Small dead winter cluster ©ATTTA

There are a couple of different aspects to consider as to why climate change impacts the colony size and colony age structure, and can lead to colony failure come spring. First, there is an increase in the rate of population decline in the fall and winter². This is due to extended fall and winter flight-conductive weather and related mortality². Second, spring temperatures conducive for flight commence before brood-rearing begins, which can significantly impact the ability of a colony to build up during the spring². This shifts the population to be a higher proportion of older bees, and leaves fewer young bees to mitigate spring dwindle².

Changing climate is a major concern for the Canadian beekeeping industry. In recent years, beekeepers have had to adapt to changing weather patterns dealing with climate events such as wildfires, flooding and drought. Disrupted forage patterns have impacted both the honey crop and honey stores used to get colonies through winter. Additionally, the lengthening beekeeping season increases pressure of pests and diseases.

There are many aspects to discuss around how climate change is impacting the beekeeping industry. Continue reading our blog for future information on how beekeepers manage and adapt beekeeping practices with a changing climate.

Connecting with ATTTA Specialists

If you’d like to connect with ATTTA specialists or learn more about our program, you can:

visit our website at https://www.perennia.ca/portfolio-items/honey-bees/

Email attta@perennia.ca

References

1. Rogers, R., Hassler, E., Carey, Q. and Cazier, J., 2023. More time to fly: With a warming climate the Western honey bee (Apis mellifera, Linnaeus) now has more temperature-eligible flight hours than 40 years ago. Journal of Apicultural Research, 62(3), pp.615-624.
2. Rajagopalan, K., DeGrandi-Hoffman, G., Pruett, M., Jones, V.P., Corby-Harris, V., Pireaud, J., Curry, R., Hopkins, B. and Northfield, T.D., 2024. Warmer autumns and winters could reduce honey bee overwintering survival with potential risks for pollination services. Scientific Reports, 14(1), p.5410.