Honeybees need a diverse ecosystem to survive in the forest, according to a study published in the Journal of Applied Ecology. The team defends that promoting biodiversity in the forest would help both the bees and the forest itself.
It’s easier to imagine bees flying around in flowering meadows rather than in dense forests. The western honeybee (Apis mellifera), however, prefers to live in woodlands and nest in tree cavities. However, how suitable are current deciduous forests (often managed for wood production) for wild bees? A team of researchers from the Julius-Maximilians-Universität Würzburg (JMU) in Germany decided to find out.
With this in mind, Benjamin Rutschmann and Patrick Kohl placed 12 colonies in observation hives across the Steigerwald. The forest surroundings varied for each bee colony. The researchers analysed over 2000 waggle dances — how bees communicate with each other about the location of food sources — using video recordings during the foraging season (from March to August). Based on these recordings, it turns out bees used the forest less than expected. In fact, colonies that lived deep in the forest and away from open land had to travel long distances to find food.
“Especially in late summer, the supply of pollen in the forest was not guaranteed or insufficient, besides this being an especially critical time for the bee colonies and their brood,” says Rutschmann. The authors believe this is mainly due to the fact that the most common species of tree is beech. “Beech forests are dark, there is not much growing on the ground. Hardly any plants can cope with the light conditions in beech forests after the canopy closes, so a diverse herb layer that would be so important for bees is missing.”
Honeydew or flowering tree species (such as linden, black locust, and chestnut) or shrubs (such as blackberry and raspberry) represent important sources of food for bees, both carbohydrates, and protein. However, this only lasts for short periods of the year. Bees need to find a balanced food supply throughout the season. “For a more bee-friendly environment, forests should be diversified with insect-pollinated trees – cherry, linden, maple, willow, horse chestnut, or sweet chestnut,” said Rutschmann.
In addition to the lack of food, wild honeybee colonies in managed forests also struggle to find suitable trees for their colonies. The authors defend that keeping forests in a more natural state — less optimised for timber production — would increase floral diversity and improve the chances of survival of wild-living honeybee colonies.
In the long term, established bee colonies would also contribute to an increase in biodiversity in the forest. Most plants rely on cross-pollination, and the honeybee is one of the most important pollinators. The important message from this study is that a more diverse forest benefits both the bees and the forest itself. A diverse ecosystem is healthier and less susceptible to pest infestation, for example. “Converting forests to species-rich mixed deciduous forests not only promotes biodiversity but also adaptation to future climate conditions,” said Ingolf Steffan-Dewenter, who was also involved in this study.
Rutschmann B, Kohl P, Steffan-Dewenter I (2023) Foraging distances, habitat preferences and seasonal colony performance of honeybees in Central European forest landscapes. Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.14389