Extreme summer heat is overwhelming honey bee hives. Discover how high temperatures disrupt a colony's cooling system, leading to decline and what it means for our future.
Honey bees are well known for maintaining the temperature inside their hives at an optimal level. This precise temperature control is crucial for the healthy development of young bees and the overall wellbeing of the entire hive. However, recent research shows that very high summer temperatures can overwhelm the bees' natural cooling system, putting their colonies at risk. The study was published in Ecological and Evolutionary Physiology.
The study tracked nine honey bee colonies during a particularly hot summer in Arizona. Over a period of three months, temperatures outside often exceeded 40°C. Researchers found that during long and intense heat waves, the bees had a hard time keeping the hive temperature steady. As a result, the number of bees in the colonies started to decline. This is concerning because honey bees are essential for pollinating both crops and wild plants across the globe.
How Bees Cool Their Hives
Typically, bees cool their hives by using their wings to fan air and evaporate water, similar to how humans sweat. The study revealed that even though bees were able to maintain the average temperature in the area where young bees develop within the ideal range of 34–36°C, this wasn't the whole story. Inside the hive, temperatures fluctuated greatly throughout the day.
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Young bees in the central part of the brood area still faced several hours each day where the temperature was either too hot or too cold. The situation was even worse near the edges of the brood area, where developing bees spent up to eight hours daily outside the safe temperature range. These regular temperature changes can cause stress, slow down the development of young bees, and increase the chances of them dying.
Weaker Colonies
The study also found that colonies that were exposed to higher outdoor temperatures and more temperature swings inside the hive lost more bees over time. Extreme heat can damage young bees directly and can also reduce the lifespan of adult workers, which weakens the colony's ability to survive and recover.
Colony size turned out to be a key factor. Larger colonies were better at regulating internal temperatures. In smaller colonies, temperatures near the edges of the brood could change by as much as 11°C in a single day. In contrast, larger colonies experienced much smaller temperature fluctuations. This stability meant that bees in bigger colonies were less likely to be exposed to extreme heat or cold for prolonged periods.
What It Means for the Future
The researchers caution that this issue is likely to become more common as the climate continues to warm. Global temperatures are expected to increase substantially by the end of the century, leading to more frequent and intense heat waves. High humidity can further exacerbate the problem, as it reduces the effectiveness of evaporative cooling, which is the main way bees stay cool.
For beekeepers and farmers, these findings are a major concern. Many crops rely on honey bees for pollination. To help bees deal with rising temperatures, beekeepers might need to provide more water, place hives in shaded areas, improve hive insulation, and ensure bees have access to high-quality food. These measures could help protect bee colonies as extreme heat becomes more frequent.
