Bees

The first study on a possible influence of high-frequency electromagnetic fields on the orientation of bees dates back to the 1980s ^[1]. Six thousand individual bees were marked. These were then exposed or sham-exposed, and their orientation behaviour was observed. No significant influence of the exposure on the orientation of bees was found; from both groups, approx. 80 % of the bees returned.

Studies at the University of Koblenz

At the University of Koblenz, the return behaviour of bees under the influence of high-frequency electromagnetic fields was investigated in a pilot study (only in german) (2005) and a follow-up study (2006). A DECT base station placed under the hive was used for exposure. This is an unrealistic situation from which direct conclusions about the effects of mobile communications base stations cannot be drawn.

The pilot study (only in german) showed a significantly higher loss of returning animals in the exposed bees than in the non-exposed bees. In the folloy-up study ^[2], the number of hives was increased, and the trend found in the pilot study was confirmed; however, the results were not significant. About 60 % of the unexposed and 50 % of the exposed bees returned. A drastic disturbance of the orientation of bees by high-frequency electromagnetic fields cannot be concluded from these studies.

Effects on queen bees

The effect of mobile phone exposure on the development of queen bees was investigated at the Apicultural State Institute at the University of Stuttgart-Hohenheim. Larval development remained unaffected; however, pupal mortality increased. The hatched queen bees had normal mating success, and their ability to establish healthy colonies was not affected ^[3].

Investigations in Switzerland

Exposure to mobile phones was also chosen by a Swiss scientist in his pilot study ^[4]. He exposed hives to mobile phones that were either communicating audibly with each other, in standby mode, or switched off. Exclusively in speech mode, the bees reacted to beeps (e.g. before swarming or in case of disturbances). The author attributes the reaction to high-frequency electromagnetic fields and evaluates it as a considerable disturbance.

In a follow-up study ^[5] by the same author, exposure was achieved using equipment that amplified existing electromagnetic fields from base stations in order to irradiate beehives. The aim was to propose this method to other scientists for repeat experiments. As an example, five hives were examined with similar results as in the pilot study.

Both studies show considerable methodological deficiencies and do not allow any robust statements.

Field study in Greece

The only field study ^[6] on the occurrence of bees and other pollinators was carried out on the Greek islands. At different distances from base stations, the field strength was measured, and the occurrence of flowers and their pollinators (e.g. bees, wasps, and flies) was determined. The relationship was complex; some species increased significantly with increasing field strength whilst others decreased. The number of bees generally increased with the field strength; however, this observation concerned mainly species that build their nests underground and are protected from electromagnetic fields there. The number of wasps and hoverflies decreased with the field strength, whilst the number of bumble flies increased. The biodiversity did not change. It remains to be determined whether the observed correlations are causal. A general harmful effect of electromagnetic fields on bees or other insects cannot be deduced from these results.

Energy absorption at high frequencies

Similar to other insects, the energy absorption in bees increases with increasing frequency and decreasing wavelength of the high-frequency fields because of resonance effects. Calculations on different bee species for the frequency range 0.6–120 GHz have shown that there is a strong increase in energy absorption, especially above 3 GHz. Above 6–12 GHz, it then remains at an elevated level but does not increase further. In a realistic exposure to an electric field strength of 1 V/m, only a few nanowatts are absorbed. The thermal range is not reached ^[7].

Causes of bee mortality

Overall, it can be assumed that the bee mortality often mentioned in the headlines recently has to do with many influencing factors. These include diseases, parasites such as the well-known Varroa mite as well as pesticides that damage the nervous system of insects. On the other hand, electromagnetic fields from base stations play no role in bee mortality. In large cities, which are particularly well supplied with mobile communications, bees are increasingly spreading and thriving more than in intensively farmed areas.

References

[1] Gary NE, Westerdahl BB (1981) Flight, orientation, and homing abilities of honeybees following exposure to 2.45-GHz CW microwaves. Bioelectromagnetics 28(1): 71 – 75.

[2] Kimmel S, Kuhn J, Harst W, Stever H. Electromagnetic radiation: Influences on honeybees (Apis mellifera). IIAS - InterSymp Conference, Baden-Baden; 2007.

[3] Odemer R, Odemer F (2019). Effects of radiofrequency electromagnetic radiation (RF-EMF) on honey bee queen development and mating success. Sci Total Environ 661: 553-562.

[4] Favre D (2011) Mobile phone-induced honeybee worker piping. Apidologie 4(3): 270 - 279.

[5] Favre D (2017). Disturbing Honeybees’ Behavior with Electromagnetic Waves: a Methodology. Journal of Behavior 2(2).

[6] Lázaro A, Chroni A, Tscheulin T, Devalez J, Matsoukas C, Petanidou T (2016). Electromagnetic radiation of mobile telecommunication antennas affects the abundance and composition of wild pollinators. Journal of Insect Conservation 20(2): 315-324.

[7] Thielens, A, Greco, MK, Verloock, L, Martens, L, Joseph, W (2020). Radio-frequency electromagnetic field exposure of western honey bees. Sci Rep 10(1): 461.