Why heat ruins bees' work and damages honey

Excessive heat harms bees' work, with a series of chain reactions that can even jeopardize the colony and its activity, and ultimately ruin the quality and aroma of honey. Bees are among the greatest victims of the climate crisis, suffering the consequences in terms of work (in some conditions it becomes much more difficult, if not impossible), hive structure (which becomes much more fragile), and honey quantity and quality (with real drops in production).

Damage to bee work

The first problem concerns the working environment: the hive is too hot, and the bees must work hard to cool it, producing natural ventilation with their wings and constantly transporting water. This activity takes up a lot of time from collecting nectar and pollen, whereas the hive temperature, to allow the bees to work peacefully, must never exceed 35 degrees Celsius. 

When temperatures exceed 38 degrees, bees experience such heat stress that they stop flying. Furthermore, flowers produce less nectar, many plants reduce their nectar production or wither, and bees therefore find less food for their work. 

Damage to the hive

Too much heat can damage the hive in several ways, especially when the bees are no longer able to maintain a stable internal temperature.

• Wax can soften and warpThe combs become less resistant; if the temperature is very high, they can warp or even collapse. This can cause the combs to fall and the loss of honey and brood.
• The brood may be damagedLarvae and pupae require relatively stable thermal conditions. Bees must therefore increase ventilation and cooling; if they fail to compensate, brood development may be compromised.
• Honey can leak outIf a comb breaks or collapses due to heat, honey can leak into the hive.
• The colony wastes a lot of energy to cool itselfWorkers collect water and distribute it throughout the hive, while others fan the water with their wings. This energy and time are diverted from gathering water, brood care, and other activities.
• The colony may become more vulnerableProlonged heat stress can reduce the overall efficiency of the colony and, together with the scarcity of water and nectar during droughts, can contribute to its weakening.
• In extreme cases, the colony may abandon the hive (heat swarming or escape behavior), especially when internal conditions become difficult to maintain.

Honey damage 

As for honey, the main damages of excessive heat are these:

• • Overheating: High temperatures can alter some delicate components of honey, reducing its quality. Above 25-30 degrees, the natural enzymes and vitamins in honey begin to degrade, and the original olfactory and gustatory qualities vanish, reducing the product's beneficial properties. In practice, excessive heat alters the honey's aroma and flavor. 
  • Increased HMF (5-hydroxymethylfurfural): It is one of the main indicators of heat-related honey spoilage. The more the honey is heated and the longer it remains warm, the higher the HMF tends to increase.
  • Browning: Honey may darken due to chemical reactions caused by heat.
  • Loss of some thermolabile substances: Some minor components of honey can degrade at high temperatures.

Finally, excessive heat can also harm bee tourism , both directly and indirectly. This is primarily because it reduces the bees' observable activity: during the hottest hours of the day, many bees focus on ventilating and cooling the hive, so visitors see less foraging activity. Intense heat, sun, and humidity can make outdoor visits difficult, especially for children, the elderly, and those sensitive to heat.

Read also:

• What would happen if bees disappeared?
• Bee massacre: a registry is born to count and save them.
• How bees sleep