Honeybees can normally regulate their hive temperature, even when the temperature outside changes. Honeybees do this by fanning their wings together, spreading water and clustering as a whole. But according to the new research study published in the ecological and evolutionary physiology journal, extreme summer heat can disrupt these critical pollinators’ cooling systems, which can eventually decrease colony population.
A recent study called “Negative Effects of Excessive Heat on Colony Thermoregulation and Population Dynamics in Honey Bees” looked at how increased temperature can affect honey bee colonies. Researchers observed nine colonies in Arizona over three months when temperatures often climbed above 40°C (104°F). They found that increasingly severe heatwaves around the world pose a serious risk to honeybees and the pollination they provide.
The study’s authors, Jun Chen, Adrian Fisher II, Gloria DeGrandi-Hoffman, Cahit Ozturk, Brian H. Smith, Jennifer H. Fewell, Yun Kang, Kylie Maxwell, Kynadi Overcash, Keerut Chahal, and Jon F. Harrison, explained that honeybees have ways to deal with heat. But until now, no research had tested just how much heat colonies can handle or how natural heat waves affect their ability to stay cool and grow.
The researchers found that honeybee colonies were able to keep the average temperature for their developing young (brood) within the ideal 34-36 degrees Celsius range. This temperature is important for a healthy growth of the brood. However, temperatures still changed a lot throughout the day. Bees in the center of the brood spent 1.7 hours each day being too cold and 1.6 hours too hot. At the edges of the brood, the conditions were even harsher, with young bees experiencing nearly 8 hours daily outside the optimal temperature range.
Extreme temperature changes can seriously affect honeybee colonies. When hives experience very high temperatures or large swings in temperature, colony populations tend to drop.
The study showed that when temperatures rise above 40°C, it can be very harmful to honeybees. Young bees, especially those still developing in the hive, can get hurt by the heat. Adult bees also face risks because high temperatures can shorten their lifespans. When this happens, the total number of bees in a hive goes down, which can weaken the colony. The size of the colony is very important in protecting bees from extreme heat. Larger colonies are better at keeping their hive temperature stable.
Smaller hives, on the other hand, experience bigger swings in temperature. For example, at the edges of a small hive, temperatures can change by up to 11°C in a day. In bigger hives, this change is smaller, around 6°C. Because of this stability, bees in large colonies spend less time exposed to dangerous temperatures that can harm them. When we look at the bigger picture, climate change makes this problem even more serious. Current climate models predict that global temperatures could rise by about 2.7°C by the year 2100. If greenhouse gas emissions remain high, temperatures could increase by as much as 4°C.
This warming will probably make heatwaves happen more often and make them more severe around the world. High humidity can make it even harder for bees.
When the air is very humid, bees cannot cool their hives well through evaporation. This puts them at greater risk during heatwaves. For beekeepers and farmers, this research is very important. It shows that protecting bees from heat is important. To help colonies survive rising temperatures, hives may need extra water and better insulation. Using these strategies, farmers can help bees regulate temperature, stay healthy, and continue to support pollination even in hotter climates.
