A systematically conducted analysis ^[1] evaluated over 100 scientific papers on the potential ecological effects of high-frequency electromagnetic fields. Specifically, insects, birds, vertebrates, and plants and the endpoints of reproduction, development, and behaviour were addressed. Laboratory studies on rodents and chickens predominate; in many cases thermal effects far above the limit values were described. Only a few studies were carried out in the wild. In view of the insufficient data and changing quality of the studies, further research is called for.

Another review ^[2] deals with studies on the potential effects of high-frequency electromagnetic fields on the environment. In particular, insects, birds, mammals, and plants were considered. The studies were assessed in terms of quality with the result that studies of poor quality, especially with regard to exposure determination and statistics, clearly predominated. It was often not possible to exclude confounding factors; in some studies, the influences of high and low frequency fields were mixed, and many publications were published in journals that do not carry out a peer-review process for quality assurance. Many studies showed biological, often negative effects on animals and plants. However, for the reasons mentioned above, they cannot be taken as proof that high-frequency electromagnetic fields have a harmful effect on the environment. In order to clarify this question, interdisciplinary research with detailed description of the experiments and correct exposure determination is necessary.

Literature

[1] Cucurachi S, Tamis WLM, Vijver MG, Peijnenburg WJGM, Bolte JFB, de Snoo GR (2013) A review of the ecological effects of radiofrequency electromagnetic fields (RF-EMF). Environ. Int. 51: 116 - 140.

[2] Verschaeve L (2014). Environmental Impact of Radiofrequency Fields from Mobile Phone Base Stations. Critical Reviews in Environmental Science and Technology 44(12): 1313 - 1369.

Studies on cattle in Germany

From 1998 to 2000, the “Bavarian Cattle Study” was carried out in 38 farms in Bavaria and Hesse. The electric field strength was measured on all participating farms. No abnormalities in milk yield, fertility, secretion of sleep hormones, and stress symptoms as a result of the influence of mobile communications were detectable. Observed malformations were due to the occurrence of a viral disease. Only in chewing and lying behaviour did four of the eight herds examined show abnormalities ^[1]. According to the evaluation of the study, a hazard scenario as a result of mobile communications is not recognisable.

Studies on cattle in Switzerland

In Switzerland, a pilot study (only in german) on a planned cattle study was carried out in 2005 to 2006. In this study, computational and measurement techniques were used to determine the exposure of free-ranging cows as reliably as possible. Cattle on Swiss farms were found to have low exposure.

A veterinary paper from Switzerland ^[2] describes a statistical correlation between the occurrence of eye damage in new-born calves and the distance of pregnant cows from mobile communications transmitter masts. Exposure was not determined, and possible confounding factors were not recorded. A causal relationship cannot be deduced from this study.

Also in Switzerland, an experimental study ^[3] was conducted on cows exposed to a GSM signal of 12 V/m for several months. The activity of various oxidative enzymes in the blood was determined. These changed significantly but differently in individual animals, and some cows did not react at all. A comparison with a control group, which would have shown the natural fluctuation range of the enzyme activities concerned without irradiation, is missing. It is therefore not possible to interpret the results in relation to the health of cattle.

Another study from Switzerland ^[4] investigated the temporal coincidence between the installation of a mobile communications transmitter and the increased incidence of eye damage in calves on a farm. The electric field strength was quite low; other influencing factors such as infections or poisoning were excluded. The cause of the diseases has not been identified, but heredity has been discussed.

References

[1] Wenzel C, Wöhr AC, Unshelm J (2002) Das Verhalten von Milchrindern unter dem Einfluss elektromagnetischer Felder. Der praktische Tierarzt. 83(3): 260 - 267.

[2] Hässig M, Jud F, Naegeli H, Kupper J, Spiess B (2009) Prevalence of nuclear cataract in Swiss veal calves and its possible association with mobile telephone antenna base stations. Switzerland. Arch. Tierheilkd. 151(10): 471 - 478.

[3] Hässig M, Wullschleger M, Naegeli HP, Kupper J, Spiess B, Kuster N, Capstick M, Murbach M, Wullschleger M, Naegeli HP, Kupper J, Spiess B, Kuster N, Capstick M, Murbach M (2014) Influence of non ionizing radiation of base stations on the activity of redox proteins in bovines. BMC Vet Res 10(19:136).

[4] Hässig M, Jud F, Spiess B (2012) Increased occurence of nuclear cataract in the calf after erection of a mobile phone base station. Switzerland. Arch. Tierheilkd. 154(2): 82 – 86.

According to information from environmental organisations and authorities, there is no evidence that electromagnetic fields from mobile communication base stations harm bats. As a result of conservation measures, the the number of bats has been steadily increasing (only in german) since 2000. As flying animals, bats can get closer than the safety distances and come into close proximity to the transmitters. They are thus exposed to thermal effects.

Investigations at radar installations

The relationship between bat behaviour and electromagnetic fields was investigated using the activity of five bat species in the vicinity of 10 radar installations in Scotland ^[1]. The bats avoided the immediate vicinity of the transmitters with field strengths above 2 V/m. It was suggested to use avoidance behaviour and radar to keep bats away from wind turbines with which they might collide ^[2]. A mechanism of action has not been investigated; one possibility would be a perception of the heating caused by the electromagnetic fields or acoustic perception on the principle of “microwave hearing” ^[3].

References

[1] Nicholls B, Racey PA (2007) Bats Avoid Radar Installations: Could Electromagnetic Fields Deter Bats from Colliding with Wind Turbines? PLoS ONE 2(3): e297

[2] Nicholls B, Racey PA (2009) The aversive effect of electromagnetic radiation on foraging bats: a possible means of discouraging bats from approaching wind turbines. Plos One 4(7): e6246

[3] Lin JC, Wang Z (2007) Hearing of microwave pulses by humans and animals: effects, mechanism, and thresholds. Health Phys. 92(6): 621 - 628

In the vicinity of mobile communications base stations, reports from Spain and Belgium described a decrease and lower breeding success of sparrows ^{[1, 2]}. The reports from Spain also described a reduced reproductive capacity of white storks ^[3]. In Germany, no comparable observations have been reported by the state authorities for environmental protection or by bird observatories. On the contrary, it can be observed throughout Germany that storks build their nests on mobile communications transmitter masts and successfully raise their young there. In cooperation with Vodafone, the initiative “Species Protection in the Steigerwald” has been installing nesting boxes for kestrels on mobile communications transmitter masts (only in german) since 2006. They are well accepted by the birds, breeding success is good, and the chicks show no impairment.

Orientation of migratory birds

Birds can perceive the Earth’s magnetic field and orient themselves accordingly. The associated sensory organ is localised in the retina and based on a reaction of radical pairs^[4]. This reaction can be disturbed under laboratory conditions by weak alternating fields in the frequency range of 0.1–10 MHz. Frequencies above 25 MHz (as used for mobile communications) do not interfere with this system ^[5].

Studies by the University of Oldenburg ^{[6, 7, 8]} have shown that the magnetoreception of migratory birds can be disturbed even by very weak (a few nanotesla) broadband (50 kHz to 5 MHz) high-frequency fields. This frequency range affects neither power lines nor mobile communications but rather exclusively fields of strong radio transmitters and background fields in urban areas emanating from electrical and electronic devices. General disturbances of bird migration are not to be expected on the basis of these results but could exceptionally occur if birds are unable to orientate themselves according to the sun, stars, or landmarks in extremely bad weather and are also in the vicinity of corresponding field sources. There are no field studies on habituation effects to date.

References

[1] Everaert J, Bauwens D (2007) A possible effect of electromagnetic radiation from mobile phone base stations on the number of breeding house sparrows (Passer domesticus). Biol. Med. 26(1): 63 - 72

[2] Balmori A, Hallberg O (2007) The urban decline of the house sparrow (Passer domesticus): a possible link with electromagnetic radiation. Electromagn. Biol. Med. 26(2): 141 - 151

[3] Balmori, A. (2005). Possible effects of electromagnetic fields from phone masts on a population of White Stork (Ciconia ciconia). Electromag. Biol. Med. 24(2): 109 – 119

[4] Hore P, Mouritsen H. (2022) The quantum nature of bird migration. Scientific American: 326(4):27 - 31.

[5] Hiscock HG, Mouritsen H, Manolopoulos DE, Hore P (2017) Disruption of magnetic compass orientation in migratory birds by radiofrequency electromagnetic fields. Biophys J 113:1475-1484.

[6] Engels S, Schneider NL, Lefeldt N, Hein CM, Zapka M, Michalik A, Elbers D, Kittel A, Hore PJ, Mouritsen H (2014) Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird. Nature doi: 10.1038/nature13290.

[7] Schwarze S, Schneider NL, Reichl T, Dreyer D, Lefeldt N, Engels S, Baker N, Hore PJ, Mouritsen H (2016). Weak Broadband Electromagnetic Fields are More Disruptive to Magnetic Compass Orientation in a Night-Migratory Songbird (Erithacus rubecula) than Strong Narrow-Band Fields. Front Behav Neurosci. 10: 55.

[8] Kobylkov D, Wynn J, Winklhofer M, Chetverikova R, X, J, Hiscock H, Hore PJ, Mouritsen H. (2019) Electromagnetic 0.1-100 kHz noise does not disrupt orientation in a night-migrating songbird implying a spin coherence lifetime of less than 10 µs. J R Soc Interface 16:20190716.

Because most studies show an effect, a German-language review article on the effects of electromagnetic fields on insects ^[1] concludes that electromagnetic fields could have a serious impact on the vitality of insect populations. Various alleged harmful effects are mentioned. Many of these are biological effects that do not necessarily have to be harmful with respect to behaviour. Others occur only in frequency ranges that cannot be assigned to mobile communications. For a proof of an actual causal relationship, several studies of high quality would have to have consistently shown this relationship between EMF and the aforementioned harmful effects. The author himself admits that the studies were mostly not replicated. It is also unclear how the quality of the individual studies was assessed in the review. The author separates studies on the basis of quality criteria but does not name them. Blinding and the use of a well-defined exposure device were apparently not relevant criteria because predominantly studies that used conventional devices for exposure were included. Such studies are then limited in their informative value and contribute little to the evaluation of a causal relationship. The author also does not consistently distinguish between effects and mechanisms of action documented for static and low-frequency fields (perception, behaviour, orientation according to the Earth’s magnetic field) and the effects of high-frequency fields.

Another review ^[2] focuses on the possible involvement of high-frequency electromagnetic fields of mobile communications in insect mortality and warns against the introduction of 5G. The author comprehensively summarises the available literature on the effects of electric, magnetic, and electromagnetic fields on insects. He does not address the quality of individual publications and does not make any quality assessment. He quotes the individual studies selectively, tendentiously, and inaccurately. From studies done exclusively on ants, he concludes bee mortality. A whole series of studies on bees and ants with end devices such as DECT, WLAN, and mobile phones are listed as arguments for the harmfulness of base stations in the field. Indications from the range of low-frequency and high-frequency fields below and above the limit values are shown mixed. From known effects and mechanisms of action of low-frequency fields, the author concludes that there are also non-thermal effects with high-frequency fields and that these are harmful. Finally, arguments against 5G are derived from this. This type of reasoning does not meet scientific standards and is misleading.

The two papers mentioned on insects contradict another review specifically on effects of anthropogenic fields of all frequency ranges on pollinating insects. It was shown that there are only few good quality studies ^[3]. These show that night-time lighting in particular has negative effects on insect populations. Furthermore, laboratory studies showed that low-frequency magnetic fields such as those from power lines could affect the orientation and learning ability of bees. Studies on high-frequency fields yielded ambiguous results; depending on the location and type, both positive and negative effects were observed.

The currently much-discussed extinction of insects ^[4] already began in the early 1990s before the widespread expansion of mobile communications. Therefore, mobile communications cannot be considered as a major cause.

So far, there is only one experimental field study on the influence of electromagnetic fields of a mobile communications base station on different species of insects ^[5] (e.g. springtails, predatory bugs, parasitic wasps, fruit flies). The animals were exposed at different distances from the transmitter; control animals were shielded in metal containers. The power flux density reached a maximum of one thousandth of the limit value. The reproductive capacity of the insects was not affected under these experimental conditions.

The small body size of insects also means that relatively little energy is absorbed at the frequencies used for mobile communications. Only above 6 GHz, and especially at 12–24 GHz, does energy absorption increase ^[6]. This is particularly relevant in connection with the higher frequencies planned for 5G.

Strong high-frequency electromagnetic fields (far above the limits) can be used to kill wood pests ^[7]_. This means that toxic chemicals can be dispensed with and the environment can be protected.

References

[1] Thill, A (2020). Review - Biologische Wirkungen elektromagnetischer Felder auf Insekten. Umwelt Medizin Gesellschaft 3 (Sonderbeilage): 28.

[2] Balmori, A (2021). Electromagnetic radiation as an emerging driver factor for the decline of insects. Science of The Total Environment 767: 144913.

[3] Vanbergen AJ, Potts SG, Vian A, Malkemper EP, Young J, Tscheulin T (2019). Risk to pollinators from anthropogenic electro-magnetic radiation (EMR): Evidence and knowledge gaps. Sci Total Environ 695: 133833.

[4] Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, Schwan H, Stenmans W, Muller A, Sumser H, Horren T, Goulson D, de Kroon H (2017). More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS One 12(10): e0185809.

[5] Vijver MG, Bolte JF, Evans TR, Tamis WL, Peijnenburg WJ, Musters CJ, de Snoo GR. (2014) Investigating short-term exposure to electromagnetic fields on reproductive capacity of invertebrates in the field situation. Electromagn Biol Med. 33(1): 21 - 28

[6] Thielens A, Bell D, Mortimore DB, Greco MK, Martens L, Joseph W (2018). Exposure of Insects to Radio-Frequency Electromagnetic Fields from 2 to 120 GHz. Sci Rep 8(1): 3924

[7] Kraus, M, Holzer, F, Hoyer, C, Trommler, U, Kopinke, F-D, Roland, U (2018). Chemical-free pest control by means of dielectric heating with radio waves: Selective heating. Chemical Engineering & Technology 41(1): 116-123.

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.

Some studies have dealt with possible negative effects of high-frequency electromagnetic fields on forest trees. In several systematic long-term studies carried out in Switzerland around radio and television transmitters ^{[1, 2]} or under exposure to 2,450 MHz over several years at power flux densities of 0.007 to 300 W/m2 ^[3], no negative effects on spruce, fir, pine, or beech trees were found. A reduction in thickness growth of pine trees was observed around the Lithuanian radar station in Skrunda ^[4]. An observational study from the US showed improved growth in young poplars when electromagnetic fields were shielded ^[5].

Study on the influence of radar radiation on beech and spruce treesn

The effect of electromagnetic fields on beech and spruce was tested in a three-year study ^[6]. For this purpose, entire crown areas were exposed to defined irradiation by radar during the vegetation periods. There was no effect on the experimental trees.

Under the given conditions, electromagnetic fields do not pose an obvious risk of damage to forest trees. The transmitting power of mobile communications base stations is much lower than that of the powerful transmitters examined here. Therefore, no negative influence of electromagnetic fields on plants is to be expected in their environment.

Tree damage around base stations

In contrast, there have been reports of damaged trees near mobile communications base stations ^[7]. 620 sites were visited, and six concrete examples are documented in the publication.

For another, more detailed publication ^[8], trees were observed in Bamberg and Hallstadt from 2006 to 2015. Quantitative data were also collected in 2015. Sixty unilaterally damaged exposed trees with a view to a base station and 30 non-exposed healthy trees were selected. Only 30 trees were randomly selected. Measurements showed a higher exposure to high-frequency electromagnetic fields on the damaged side of the tree than on the other side or on healthy trees. All measured values for the high-frequency electromagnetic fields were well below the limit values.

The cause of one-sided damage to trees does not necessarily have to be a base station. Other factors such as climatic factors (which were discussed but not completely ruled out) are also possible. A qualitative deficiency is the selective and not exclusively random choice of trees. The observational study presented can prove a temporal and spatial but not a causal relationship.

Surveys on forest condition

The condition of forests is reviewed at regular intervals by experts and presented in reports on forest condition by the Federal Ministry of Food and Agriculture (BMEL) (only in german). The surveys have been conducted annually since 1984. A clear trend towards deterioration in the condition of deciduous trees – visible from crown defoliation – is discernible; however, this had already begun before the introduction of mobile communications. Climate change is currently playing the biggest role.

References

[1] Joos K, Masumy SA, Schweingruber FH, Stäger C (1988) Untersuchung über mögliche Einflüsse hochfrequenter elektromagnetischer Wellen auf den Wald. Techn. Mitt PTT 1: 1 - 23

[2] Stäger C 1989 Felduntersuchung über eventuelle Schadenwirkungen von Mikrowellen auf den Wald. Techn. Mitt. PTT 67: 517 - 526.

[3] Schmutz P, Siegenthaler J, Stäger C, Trajan D, Bucher JB (1994) Long-term exposure of young spruce and beech trees to 2450 MHz microwave radiation. Science of the Total Environment 180(1):43 - 48

[4] Balodis V, Brumelis G, Kalviskis K, Nikodemus O, Tjarve D, Znotina V (1996) Does the Skrunda Radio Location Station diminish the radial growth of pine trees? Science of the Total Environment. 180(1): 57 - 64

[5] Haggerty K (2010). Adverse Influence of Radio Frequency Background on Trembling Aspen Seedlings: Preliminary Observations. International Journal of Forestry Research 2010: 1-7.

[6] Götz G, Matyssek R, Käs G (2001) Fichte und Buche unter dem Einfluss von Radarbestrahlung. Allgemeine Forst- und Jagdzeitung 172(4): 74 - 78

[7] Waldmann-Selsam C, Eger E (2013) Baumschäden im Umkreis von Mobilfunksendeanlagen. Umwelt Medizin Gesellschaft 26(3): 198 - 208

[8] Waldmann-Selsam C, Balmori-de la Puente A, Breunig H, Balmori A. (2016) Radiofrequency radiation injures trees around mobile phone base stations .Sci Total Environ. 572: 554-569

A review on the effects of high-frequency electromagnetic fields specifically on plants ^[1] describes positive and negative influences, especially on germination and growth, which depend on frequency, modulation, and power flux density as well as plant species and growth stage. Overall, the data available are contradictory and insufficient in order to be able to draw any general conclusions.

Another review on plants ^[2] states that diverse and often contradictory influences of high-frequency electromagnetic fields on the metabolism, gene expression, and growth of plants have been described; these strongly depend on frequency and exposure intensity. The authors propose considering high-frequency fields as a non-harmful environmental factor that can influence plant metabolism.

Another review ^[3] analyses 45 experimental studies on plants from 1996–2016 that were published in peer-reviewed journals. The quality of the exposure was not assessed. Most studies showed an influence of electromagnetic fields on the physiological and morphological parameters of plants. Some species such as maize, mallow, peas, clover, duckweed, tomatoes, onions, and beans proved to be particularly sensitive to fields.

The most recent review paper on effects of high-frequency electromagnetic fields on plants ^[4] promises a critical evaluation of the effects of high-frequency electromagnetic fields on plants but does not mention the selection criteria and the qualitative standards applied. It is clearly shown that the energy of high-frequency fields is not sufficient to directly damage the genetic material. Nevertheless, changes in gene expression and influences on cell division have been observed several times in studies. Effects on the calcium balance and reactive oxygen species are named as mechanisms of action. Epigenetic effects are also suspected. How these effects occur biophysically remains unclear and needs to be further investigated. The problem of dosimetry and exposure determination in plants is also addressed. Because of the large surface area in relation to volume as well as insufficient knowledge of dielectric properties of plants, it is difficult to correctly determine the SAR value. The responses of the plants are described as two-stage; first, there is a rapid response involving gene expression and metabolism. Second, changes in growth may or may not occur. Overall, the effects on plants can be positive or negative and are considered to be rather low compared with other environmental impacts.

Studies from France

A French research group at the University of Angers has been studying the effects of short-term exposure to high-frequency fields on plants for 15 years. In tomatoes, an increased expression of certain messenger substances as well as changes in energy metabolism and gene expression were found after GSM exposure; these can be interpreted as a stress response ^{[5, 6]}. Although such reactions mean a strain on the plants, they are physiologically normal and do not threaten the survival of the plants. The reactions are systemic; this means that the whole plant reacts even if only a few leaves have been exposed ^[7]. This is similar to the reaction to being eaten by pests; the same messenger substances are also involved. In order to observe longer-term effects, the same working group studied roses ^[8]. Existing shoots were not affected by GSM; however, if developing buds were exposed, there was a reduction in growth.

Studies on the genetic material

Gene expression in plant cell cultures (Arabidopsis thaliana) was investigated under the influence of UMTS ^[9]. From the entire genome of the plant, a few genes involved in responses to light have increased expression. The authors do not expect serious physiological consequences based on these results. An Indian research group observed reduced root growth and effects on the genetic material in the roots of onions under the influence of mobile communication fields ^{[10, 11]}. An Indian study on rice in a high-frequency exposure chamber showed a reduced germination rate accompanied by an up-regulation of certain genes and pigments; this was interpreted as a stress response ^[12].

Summary

Overall, most studies on plants show physiological effects of electromagnetic fields. Many of these are contradictory and have not been independently reproduced. The mechanisms of action remain unclear. The effects observed often correspond to a mild stress reaction and are minor compared with other environmental influences. It is necessary to confirm the results and to clarify the underlying mechanisms of action.

References

[1] Jayasanka SMDH, Asaeda T (2014) The significance of microwaves in the environment and its effect on plants. Environmental Reviews 22(3): 220 - 228.

[2] Vian A, Davies E, Gendraud M, Bonnet P (2016) Plant Responses to High Frequency Electromagnetic Fields. Biomed Res Int. 2016, ID 1830262.

[3] Halgamuge MN (2017). Review: Weak radiofrequency radiation exposure from mobile phone radiation on plants. Electromagn Biol Med 36(2): 213-235.

[4] Kaur, S, Vian, A, Chandel, S, Singh, HP, Batish, DR, Kohli, RK (2021). Sensitivity of plants to high frequency electromagnetic radiation: Cellular mechanisms and morphological changes. Reviews in Environmental Science and Bio-Technology.

[5] Vian A, Roux D, Girard S, Bonnet P, Paladian F, Davies E, Ledoigt G (2006) Microwave irradiation affects gene expression in plants. Plant Signal Behav. 1(2): 67 - 70.

[6] Roux D, Faure C, Bonnet P, Girard S, Ledoigt G, Davies E, Gendraud M, Paladian F, Vian A (2008) A possible role for extra-cellular ATP in plant responses to high frequency, low amplitude electromagnetic field. Plant Signal Behav. 3(6): 383 – 385.

[7] Beaubois E, Girard S, Lallechere S, Davies E, Paladian F, Bonnet P, Ledoigt G, Vian A (2007) Intercellular communication in plants: evidence for two rapidly transmitted systemic signals generated in response to electromagnetic field stimulation in tomato. Plant Cell Environ. 30: 834 - 844.

[8] Grémiaux A, Girard S, Guérin V, Lothier J, Baluška F, Davies E, Bonnet P, Vian A (2016) Low-amplitude, high-frequency electromagnetic field exposure causes delayed and reduced growth in Rosa hybrida. J Plant Physiol. 190: 44 – 53.

[9] Engelmann JC, Deeken R, Müller T, Nimtz G, Rob M, Roelfsema G, Hedrich R (2008) Is gene activity in plant cells affected by UMTS-irradiation? A whole genome approach. Adv Appl Bioinform Chem. 1: 71 - 83.

[10] Chandel S, Kaur S, Issa M, Singh HP, Batish DR, Kohli RK (2019). Exposure to mobile phone radiations at 2350 MHz incites cyto- and genotoxic effects in root meristems of Allium cepa. J Environ Health Sci Eng 17(1): 97-104.

[11] Kumar, A, Kaur, S, Chandel, S, Singh, HP, Batish, DR, Kohli, RK (2020). Comparative cyto- and genotoxicity of 900 MHz and 1800 MHz electromagnetic field radiations in root meristems of allium cepa. Ecotoxicol Environ Saf 188: 109786.

[12] Kundu, A, Vangaru, S, Bhattacharyya, S, Mallick, AI, Gupta, B (2021). Electromagnetic irradiation evokes physiological and molecular alterations in rice. Bioelectromagnetics 42(2): 173-185.

In connection with the planned expansion of high-voltage direct current transmission lines, RWTH Aachen University has published two reviews on the effects of static electric fields on living organisms and plants^{[1, 2]}.

Eight human studies and 40 mammalian studies were analysed ^[1]. Because electric fields do not penetrate the body, acute health-relevant effects are not to be expected and have not been found. In general, it was shown that humans and animals can perceive strong electric fields above certain threshold values by means of their pelage and then react accordingly physiologically or in their behaviour. Some studies on physiological responses were of insufficient quality. The perception thresholds of humans are always lower (about 20 kV/m) for whole body exposure than for partial body exposure. More research is needed on perception thresholds.

In the second part of the study ^[2], 14 publications on invertebrates and 19 studies on plants that met the quality criteria were analysed. No negative physiological or health-relevant influences on lower animals and plants were described at field strengths that can be expected under power lines (< 35 kV/m). Invertebrates reacted behaviourally to static electric fields. Negative effects occurred at much higher field strengths. Studies with improved quality are necessary to distinguish effects of fields, corona ions, ionic currents, ozone, and nitrogen oxide.

Another review paper ^[3] describes the ecological aspects of electricity. Naturally occurring electric fields and charges as well as the corresponding reactions and perceptions of animals are described. The authors discuss the role of electric fields in the orientation, communication, prey search, pollination, and dispersal of some animal species. The functioning of sensory organs that serve to perceive electric fields in sharks and rays, electric fish, insects, and other invertebrates is explained. Possible effects of anthropogenic electric fields are only briefly addressed and mainly in connection with marine animals and insects. However, it goes without saying that wherever animals perceive natural electric fields and use them for orientation and communication, anthropogenic fields can lead to disturbances of these behaviours.

References

[1] Petri AK, Schmiedchen K, Stunder D, Dechent D, Kraus T, Bailey WH, Driessen S (2017). Biological effects of exposure to static electric fields in humans and vertebrates: a systematic review. Environ Health 16(1): 41.

[2] Schmiedchen K, Petri AK, Driessen S, Bailey WH (2018). Systematic review of biological effects of exposure to static electric fields. Part II: Invertebrates and plants. Environ Res 160: 60-76.

[3] England SJ, Robert D (2022) The ecology of electricity and electroreception. Biol Rev 97(1): 383-413.

Amongst mammals, rodents (e.g. mole rat (Heterocephalus glaber) ^[1] and zokors (Myospalax) ^[2]) and bats ^{[3, 4]} have the ability to orient themselves according to the Earth’s magnetic field. A possible disturbance of this orientation by artificial static or low-frequency fields has not been investigated so far. In other mammals, magnetoreception has not yet been clearly demonstrated; however, this is being researched by some working groups. In animals that orientate themselves in darkness like the aforementioned species, it is assumed that magnetoreception is based on the mineral magnetite. A corresponding sense organ has not yet been discovered.

Magnetoreception has also been described in some rodents that live above ground and have good vision (e.g. wood mice (Apodemus sylvaticus) ^[5] and house mice (Mus musculus) ^[6]). As a possible mechanism of perception, it is suggested that the blue light receptor cryptochrome, which is located in the mammalian retina, is activated by magnetic fields ^[7]. A similar pathway is already well described in birds but has not yet been scientifically proven in mammals. However, recent experiments on rodents suggest that mammals also perceive static magnetic fields in their eyes ^[8]. Similar to birds, this mechanism is disturbed by high-frequency electromagnetic fields with frequencies below 100 MHz ^[9].

There is also evidence of magnetoreception in other mammals. Based on satellite images, it has been observed that ruminants such as cattle and deer prefer to orient themselves in a north–south direction when outdoors ^[10]. The preferred orientation was disturbed in cattle near power lines ^[11]. Based on field observations, similar behaviour has been described in wild boars and African warthogs ^[12]. From the above observations, the authors conclude that all hoofed animals can perceive magnetic fields. As a result, their behaviour could be influenced by the magnetic fields of high-voltage power lines. However, all these studies are observational and do not specify a possible sense organ or mechanism for perceiving magnetic fields.

It has been possible to train dogs to find a magnet ^[13]. The experiment was conducted in a blinded manner, and the use of other sensory organs was largely excluded. Field experiments with automated tracking systems on dogs have shown that dogs use the magnetic field to find their way back to the starting point from unknown locations ^[14].

Intensive research is being carried out in all the areas described. However, the exact biophysical mechanism and the corresponding neuronal signalling pathways are unknown; however, there are some plausible hypotheses.

References

[1] Kimchi T, Terkel J (2001) Magnetic compass orientation in the blind mole rat Spalax ehrenbergi. J Exp Biol. 204(Pt4):751 – 758.

[2] Burda H, Marhold S, Westenberger T, Wiltschko R, Wiltschko W (1990) Magnetic compass orientation in the subterranean rodent Cryptomys hottentotus (Bathyergidae). Experientia. 46(5): 528 - 30.

[3] Holland RA, Thorup K, Vonhof MJ, Cochran WW, Wikelski M (2006) Navigation: bat orientation using Earth's magnetic field. Nature 444(7120): 7002.

[4] Holland RA, Kirschvink JL, Doak TG, Wikelski M (2008) Bats use magnetite to detect the earth's magnetic field. PLoS One 3(2): e1676.

[5] Malkemper EP, Eder SH, Begall S, Phillips JB, Winklhofer M, Hart V, Burda H. Magnetoreception in the wood mouse (Apodemus sylvaticus): Influence of weak frequency-modulated radio frequency fields. Sci Rep 4:9917; 2015.

[6] Muheim R, Edgar NM, Sloan KA, Phillips JB. Magnetic compass orientation in c57bl/6j mice. Learn Behav 34:366-373; 2006.

[7] Nießner C, Denzau S, Malkemper EP, Gross JC, Burda H, Winklhofer M, Peichl (2016) L.Cryptochrome 1 in Retinal Cone Photoreceptors Suggests a Novel Functional Role in Mammals. Sci Rep. DOI: 10.1038/srep21848.

[8] Caspar, KR, Moldenhauer, K, Moritz, RE, Němec, P, Malkemper, EP, Begall, S (2020). Eyes are essential for magnetoreception in a mammal. J R Soc Interface 17(170): 20200513.

[9] Phillips J, Muheim R, Painter M, Raines J, Anderson C, Landler L, Dommer D, Raines A, Deutschlander M, Whitehead J, Fitzpatrick NE, Youmans P, Borland C, Sloan K, McKenna K. Why is it so difficult to study magnetic compass orientation in murine rodents? J Comp Physiol A; 2022.

[10] Begall S, Červený J, Neef J, Vojtech O, Burda H (2008) Magnetic alignment in grazing and resting cattle and deer. Proc Natl. Acad. Sci. USA 105(36): 13451 - 13455.

[11] Burda H, Begall S, Červený J, Neef J, Němec P (2009) Extremely low-frequency electromagnetic fields disrupt magnetic alignment of ruminants. Proc. Natl. Acad. Sci. USA 106(14): 5708 - 5713.

[12] Červený J, Burda H, Ježek M, Kušta T, Husinec V, Novákova P, Hart V, Hartová V, Begall S, Malkemper EP (2016) Magnetic alignment in warthogs Phacochoerus africanus and wild boars Sus scrofa. Mammal Review 46(3): 5.

[13] Martini S, Begall S, Findeklee T, Schmitt M, Malkemper EP, Burda H (2018). Dogs can be trained to find a bar magnet. PeerJ 6: e6117.

[14] Benediktova, K, Adamkova, J, Svoboda, J, Painter, MS, Bartos, L, Novakova, P, Vynikalova, L, Hart, V, Phillips, J, Burda, H (2020). Magnetic alignment enhances homing efficiency of hunting dogs. Elife 9.

When wild birds are mentioned in connection with electricity supply, it is not about the influence of low-frequency electric and magnetic fields. Rather, it is about the fact that they can collide with wind turbines, power lines, and their masts in flight and die. In order to prevent bird strikes on power lines, visible bird protection markings have been used on the conductor cables for years. The effectiveness has been proven for many species ^[1].

On medium-voltage pylons with small distances between the pylon and its line wires, especially large bird species such as birds of prey, owls, and storks can easily trigger a short-circuit and suffer a fatal electric shock. On the other hand, birds use power lines as a safe perch, and many species, including storks and birds of prey, like to nest on electricity pylons. In the process, they are exposed to low-frequency fields. Their effects have so far been investigated in the field in only a few studies.

A recent review ^[2] compares negative and positive impacts of power lines on bird populations. The greatest danger comes from collisions and electrocution. Their frequency depends on the size and behaviour of the respective bird species as well as on the weather and technical parameters of the electricity pylons. Another negative factor is reduced breeding success. This is partly attributed to magnetic fields but also to the fact that nests on electricity pylons are often more exposed to weather conditions (e.g. heavy rain, wind, and sun) than nests on trees in the forest. Another negative factor is the barrier function as a result of the visibility of the power lines and the removal of vegetation below the power lines. In contrast, power lines also have positive effects on bird populations. They are used by many species as perching and resting places with a good overview (e.g. whether an enemy is approaching or food is visible) or as gathering places for flocks of birds. Many bird species successfully breed on electricity pylons. Power lines can also serve as linear landmarks for orientation.

Another review ^[3] describes changes in behaviour, reproduction, and growth in some species of raptors and songbirds that breed near power lines. The effects are not uniform and overall do not imply a consistent negative impact of power lines on breeding success.

In southern Portugal, the population density and breeding behaviour of little bustards (Tetrax tetrax) were studied in relation to the landscape in 2003–2006. Power lines proved to be an important influencing factor that greatly affected the occurrence of bustards. The cause here is not magnetic fields but rather the fragmentation of the otherwise open steppe landscape ^[4].

Work on hawks nesting in brood boxes on electricity pylons ^[5] shows that the young developed equally well in both exposed and non-exposed nests. The blood count and the concentration of the hormone melatonin were also unaffected by the magnetic fields. The magnetic flux density in the exposed nests was measured and ranged from 1 to 25 µT.

Great tits (Parus major) ^[6] breeding under power lines laid more and larger eggs than unexposed tits. Whether this was caused by the magnetic field or the habitat under the power lines remains unclear. Breeding success remained unchanged. The magnetic flux density in nests under power lines was about 0.2 µT; in distant nests, it was only about 0.6 nT.

Another paper shows that corridors below power lines provide special habitats for some songbird species in particular (e.g. warblers and sparrows), where species diversity and numbers of individuals increase ^[7].

Birds can perceive the Earth’s magnetic field

Migratory birds and many others (possibly all bird species) can perceive the Earth’s static magnetic field and orientate themselves accordingly. Research in this area is far from complete. However, current knowledge suggests that birds may use up to three independent organs to perceive the Earth’s magnetic field ^[8]. Special light receptors (cryptochromes) in the retina of migratory birds react to the orientation of the magnetic field. The basis is the influence of the magnetic field on radical pairs. Another sensory organ, which contains magnetite (iron oxide), is possibly located in the beak and reacts to the magnetic flux density ^[10]. However, the functionality of this organ is called into question ^[11]. Recently, a third magnetic field receptor in the inner ear of the pigeon was experimentally proven and explained by physical calculations; the mechanism of action of this is based on electromagnetic induction ^[12].

DC power lines

In the course of the power grid expansion, DC power lines are also planned on land; these will be surrounded by static electric and magnetic fields. It is possible that the magnetic fields, if their magnetic flux density reaches the range of the Earth’s magnetic field (about 48 µT), are perceived by birds and influence the behaviour in the immediate vicinity of the power lines.

References

[1] Mercker M (2021) Wirksamkeit von Vogelschutzmarkierungen an Freileitungen - methodische Überlegungen zu Versuchsaufbau, Auswertung und Übertragbarkeit empirischer Feldstudien. Naturschutz und Landschaftsplanung. 53(9): 32-38.

[2] D'Amico M, Catry I, Martins RC, Ascensao F, Barrientos R, Moreira F (2018). Bird on the wire: Landscape planning considering costs and benefits for bird populations coexisting with power lines. Ambio.

[3] Fernie KJ, Reynolds SJ (2005) The effects of electromagnetic fields from power lines on avian reproductive biology and physiology: a review. J Toxicol Environ Health B Crit Rev. 8(2): 127 - 140.

[4] Silva JP, Santos M, Queirós L, Leitão D, Moreira F, Pinto M, Leqoc M, Cabral JA (2010) Estimating the influence of overhead transmission power lines and landscape context on the density of little bustard Tetrax tetrax breeding populations. Ecological Modelling, 221(16) : 1954–1963.

[5] Dell'Omo G, Costantini D, Lucini V, Antonucci G, Nonno R, Polichetti A (2009) Magnetic fields produced by power lines do not affect growth, serum melatonin, leukocytes and fledging success in wild kestrels. Comp. Biochem. Physiol. C Toxicol. Pharmacol. 150(3):372 - 376.

[6] Tomás G, Barba E, Merino S, Martínez J (2012) Clutch size and egg volume in great tits (Parus major) increase under low intensity electromagnetic fields: A long-term field study. Environ. Res. 118(1): 40 - 46.

[7] Hrouda J, Brlik V (2021) Birds in power-line corridors: Effects of vegetation mowing on avian diversity and abundance. J Vertebr Biol 70(2): 21027.21021-21027.

[8] O'Neill P (2013) Magnetoreception and baroreception in birds. Dev. Growth. Differ. 55(1): 188 - 197.

[9] Hore PJ, Mouritsen H (2016) The radical-pair mechanism of magnetoreception. Annual review of biophysics 45: 299-344.

[10] Fleissner G., Stahl B., Thala, P, Falkenberg G, Fleissner G (2007) A novel concept of Fe-mineral-based magnetoreception: Histological and physicochemical data from the upper beak of homing pigeons. Naturwissenschaften 94, 631 - 642.

[11] Treiber CD, Salzer MC, Riegler J, Edelman N, Sugar C, Breuss M, Pichler P, Cadiou H, Saunders M, Lythgoe M, Shaw J, Keays DA (2012) Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons. Nature 484 (7394): 367 - 370.

[12] Nimpf, S, Nordmann, GC, Kagerbauer, D, Malkemper, EP, Landler, L, Papadaki-Anastasopoulou, A, Ushakova, L, Wenninger-Weinzierl, A, Novatchkova, M, Vincent, P, Lendl, T, Colombini, M, Mason, MJ, Keays, DA (2019). A putative mechanism for magnetoreception by electromagnetic induction in the pigeon inner ear. Curr Biol 29(23): 4052-4059 e4054.

It is known that bees can perceive the Earth’s static magnetic field and orientate themselves according to it. They have a magnetite-based receptor that reacts to the polarity of the magnetic field ^[1]. Bees can also perceive low-frequency magnetic fields at particularly low frequencies and higher flux densities ^[2].

A combined field and laboratory study showed that bees can use static magnetic fields above 26 µT (approx. 50% of the Earth’s magnetic field) when foraging. Experience and learning play a considerable role in this. Other perceptions – such as colour – have a stronger effect than the magnetic field ^[3].

In a study, it was shown that low-frequency magnetic fields, as they occur under AC power lines, negatively influence the learning ability, flight behaviour, and foraging behaviour of bees. The threshold value was 20–100 µT. Long-term memory was not affected ^[4]. A follow-up study then showed that above 100 µT, the learning ability of bees was impaired, and aggression was increased ^[5]. Another study has shown that low doses of insecticides, which are toxic to bees, do not further increase the effects of magnetic fields and in some cases even show an opposite effect ^[6]. Although there is no synergistic effect, both environmental stressors affect bee populations.

Two field studies ^{[7, 8]} investigated the effects of pesticides, magnetic fields near power lines, and the combination of these on several enzymatic biomarkers in bees. Both exposures individually had partly opposite effects; a synergistic effect was not shown. However, the vital parameters and survival rate of the hives were worst at the site with combined exposure.

Bees also perceive static electric fields and use the electrostatic charge of flowers and conspecifics for communication and orientation ^[9]. Electrostatic fields are also involved in the transfer of pollen by bees ^[10]. Bumblebees also perceive static electric fields; they can orientate themselves according to them and even gauge how much nectar a flower contains ^[11].

An older study ^[12] investigated the effect of low-frequency electric fields on bee behaviour and vital parameters (weight, honey quantity, brood) in hives below power lines. At an electric field of 7 kV/m (above the limits valid today), relatively strong electric currents were generated inside the hives. These caused contact currents and electric shocks that were perceived by bees and considerably disturbed their behaviour. In the end, this led to the lower weight of the affected colonies and high losses of colonies over the winter.

Because bees can be exposed near power lines above the limits applicable to humans, it is possible that their behaviour is also affected there. This applies equally to DC and AC power lines.

Spiders can perceive electric fields. Young spiders spread by gliding through the air on their threads. In addition to the wind, they also use the forces of natural electric fields ^[13]. Here, too, it cannot be ruled out that artificial static electric fields such as those from DC power lines influence this behaviour.

References

[1] Lambinet V, Hayden ME, Reid C, Gries G (2017). Honey bees possess a polarity-sensitive magnetoreceptor. J Comp Physiol A Neuroethol Sens Neural Behav Physiol.

[2] Kirschwink JL, Padmanabha S, Boyce CK, Ogelsby J (1997) Measurement of the threshold sensitivity of honeybees to weak, extremely low-frequency magnetic fields. J. Exp. Bio. 200(Pt9): 1363 - 1368.

[3] Chicas-Mosier, AM, Radi, M, Lafferrandre, J, O'Hara, JF, Vora, HD, Abramson, CI (2020). Low strength magnetic fields serve as a cue for foraging honey bees but prior experience is more indicative of choice. Bioelectromagnetics 41(6): 458-470.

[4] Shepherd S, Lima MAP, Oliveira EE, Sharkh SM, Jackson CW, Newland PL (2018). Extremely Low Frequency Electromagnetic Fields impair the Cognitive and Motor Abilities of Honey Bees. Sci Rep 8(1): 7932.

[5] Shepherd, S, Hollands, G, Godley, VC, Sharkh, SM, Jackson, CW, Newland, PL (2019). Increased aggression and reduced aversive learning in honey bees exposed to extremely low frequency electromagnetic fields. PLoS One 14(10): e0223614.

[6] Shepherd S, Lima MAP, Oliveira EE, Sharkh SM, Aonuma H, Jackson CW, Newland PL (2021) Sublethal neonicotinoid exposure attenuates the effects of electromagnetic fields on honey bee flight and learning. Environmental Advances 4: 100051.

[7] Lupi D, Tremolada P, Colombo M, Giacchini R, Benocci R, Parenti P, Parolini M, Zambon G, Vighi M (2020) Effects of pesticides and electromagnetic fields on honeybees: A field study using biomarkers. International Journal of Environmental Research 14(1): 107-122

[8] Lupi D, Palamara Mesiano M, Adani A, Benocci R, Giacchini R, Parenti P, Zambon G, Lavazza A, Boniotti MB, Bassi S, Colombo M, Tremolada P (2021) Combined effects of pesticides and electromagnetic-fields on honeybees: Multi-stress exposure. Insects 12(8).

[9] Greggers, U, Koch, G, Schmidt, V, Durr, A, Floriou-Servou, A, Piepenbrock, D, Gopfert, MC, Menzel, R (2013). Reception and learning of electric fields in bees. Proc Biol Sci 280(1759): 20130528.

[10] Clarke D, Morley E, Robert D (2017). The bee, the flower, and the electric field: electric ecology and aerial electroreception. J Comp Physiol A Neuroethol Sens Neural Behav Physiol.

[11] Clarke D, Whitney H, Sutton G, Robert D (2013) Detection and learning of floral electric fields by bumblebees. Science 340(6128): 66-69.

[12] Greenberg B, Bindokas VP, Frazier MJ, Gauger JR (1981) Response of honey bees, apis mellifera l., to high-voltage transmission lines 1. Environmental Entomology 10(5): 600-610.

[13] Morley EL, Robert D (2018). Electric Fields Elicit Ballooning in Spiders. Curr Biol 28(14): 2324-2330.

Some marine animals such as sharks and fish can perceive weak fields such as the Earth’s magnetic field with special sensory organs and orientate themselves accordingly. These animals can also sense the fields emitted by power cables and change their behaviour accordingly. Some cartilaginous fish (including sharks, rays, and manatees) tend to search for prey near the submarine cables ^[1] as long as the fields are weak. Within a few days, sharks learn to associate electric fields with the presence of prey; they also learn to ignore fields from power cables where no prey is found ^[2]. This indicates that they can adapt well to the changed conditions and that their hunting success is not affected by the fields emitted by cables

Some fish species (e.g. salmon and eels) orient themselves to magnetic fields during their migrations. These animals perceive the magnetic field of the submarine cables, swim more slowly in the immediate vicinity of the cables, and change their swimming direction over a short section of their journey ^[3]. However, according to previous study findings, they appear to be only slightly deflected in their direction of migration. The cables do not have a complete barrier effect.

Observational studies of coral reef fish in Florida have shown that emissions from submarine cables have no effect on the biodiversity of fish populations there ^[4].

The effects of magnetic fields on invertebrates, especially crustaceans and molluscs, are summarised in a review paper ^[5]. Only a few species were examined as examples. Long-term exposure to magnetic fields has no predominant effect on survival, reproduction or physiological parameters in several species of crustaceans and molluscs. Many crustaceans perceive magnetic fields and orient themselves accordingly. About half of the species studied prefer areas with elevated magnetic fields (e.g. the edible crab (Cancer pagurus)) or increase their activity in the presence of these fields (e.g. the American lobster (Homarus americanus)). The fields do have a minor physiological effect on the daily rhythm of the animals but are not harmful. In contrast, other species show no behavioural response to magnetic fields (e.g. young European lobsters (Homarus gammarus)) but a few avoid them (e.g. spiny lobsters (Palinuridae)).

Serious harmful effects (e.g. genetic damage or tissue damage in marine life) are not expected because the strength of the electric and magnetic fields is low. The behavioural changes described can lead to the redistribution of individual species. The number of offshore wind turbines and the submarine cables required for them is constantly increasing. Isolated encounters with cables do not pose a risk to marine animals. However, if the hunting behaviour, migration, or movement activity of certain species is disturbed too often, this can lead to energy losses. This, in turn, could have an effect on populations and ecosystems. The current state of scientific knowledge on the environmental effects of extracting renewable energy from the sea is summarised in a review paper, which also contains outlooks for the future and research recommendations ^[6].

[1] Hutchison ZL, Gill AB, Sigray P, He H, King JW. (2020) Anthropogenic electromagnetic fields (EMF) influence the behaviour of bottom-dwelling marine species. Sci. Rep. 10:4219.

[2] Kimber JA, Sims DW, Bellamy PH, Gill AB. (2014) Elasmobranch cognitive ability: Using electroreceptive foraging behaviour to demonstrate learning, habituation and memory in a benthic shark. Anim Cogn 17:55-65.

[3] Westerberg H, Lagenfelt I. (2008) Sub-sea power cables and the migration behaviour of the european eel. Fisheries Manag Ecol 15:369-375.

[4]Kilfoyle AK, Jermain RF, Dhanak MR, Huston JP, Spieler RE (2018) Effects of emf emissions from undersea electric cables on coral reef fish. Bioelectromagnetics 39(1): 35-52.

[5]Albert L, Deschamps F, Jolivet A, Olivier F, Chauvaud L, Chauvaud S (2020) A current synthesis on the effects of electric and magnetic fields emitted by submarine power cables on invertebrates. Mar Environ Res 159: 104958.

[6]Gill A, Desender M. State of the science report, Chapter 5: Risk to animals from electromagnetic fields emitted by electric cables and marine renewable energy devices. United States: Pacific Northwest National Lab; 2020:87-103.

Static magnetic fields with flux density below and above the Earth’s magnetic field can influence plants, especially in terms of germination, growth, and development. The Earth’s magnetic field also presumably played a role in the evolution of plants ^[1]. Plants contain cryptochromes (receptors for blue light) that are involved in the regulation of growth and development ^[2]. These are influenced by the Earth’s magnetic field, whereby the effect does not necessarily have to be light-dependent ^[3] and can also take place during darkness ^[4].

Germination and growth

A positive influence on germination rate, germination speed, and plant growth was described after pre-treatment of seeds with static and low-frequency magnetic fields for various types of cultivated plants but predominantly at magnetic flux densities above the limit values valid for humans (i.e. in the range of several millitesla). With regard to the influence on plant growth, the results are not consistent. Some studies describe growth-promoting and others growth-inhibiting effects of low-frequency electric and magnetic fields. The agronomic applications of magnetic fields on seeds and plants are summarised in a review paper ^[5]. Another review describes applications to help plants better withstand various environmental stress factors. In both cases, they are compilations of observations ^[6]. The mechanisms of action (possibly mediated by light receptors, reactive oxygen species, and other messenger substances) are being investigated.

Influence of high-voltage power lines

The influence of power lines on plant growth under field conditions has been investigated in only a few studies. In a five-year field study on winter wheat and maize ^[7], a yield reduction of about 7% was found at magnetic flux densities of a few microtesla, with the losses attributed to years of increased drought stress. The detectability of the field effect in comparison with the much stronger influencing factors of climate and precipitation was at the limit of statistical significance.

In China, beans were exposed to electric fields of 2 and 10 kV/m. Especially during germination and in the growth phase, a growth-promoting effect of the fields was shown; this was more pronounced at 2 kV/kg than at 10 kV/m ^[8].

Overall, it is possible, and above the limit values even quite likely, that low-frequency and especially static electric and magnetic fields can influence the growth of plants. Below the limit values under normal outdoor conditions, no adverse effects on plants are to be expected – even in the immediate vicinity of power lines.

References

[1] Maffei ME (2014) Magnetic field effects on plant growth, development, and evolution. Fron. Plant Sci. 5 (445): 1 - 1.

[2] Chaves I, Pokorný R, Byrdin M, Hoang N, Ritz T, Brettel K, Essen LO, van der Horst GT, Batschauer A, Ahmad M (2011) The cryptochromes: blue light photoreceptors in plants and animals. Annu. Rev. Plan.t Biol. 62: 335 - 364.

[3] Agliassa C, Narayana R, Christie JM, Maffei ME (2018). Geomagnetic field impacts on cryptochrome and phytochrome signaling. J Photochem Photobiol B 185: 32-40.

[4] Pooam M, Arthaut LD, Burdick D, Link J, Martino CF, Ahmad M (2019). Magnetic sensitivity mediated by the Arabidopsis blue-light receptor cryptochrome occurs during flavin reoxidation in the dark. Planta 249(2): 319-332.

[5] Sarraf M, Kataria S, Taimourya H, Santos LO, Menegatti RD, Jain M, Ihtisham M, Liu S (2020) Magnetic field (mf) applications in plants: An overview. Plants (Basel, Switzerland) 9(9).

[6] Radhakrishnan R (2019) Magnetic field regulates plant functions, growth and enhances tolerance against environmental stresses. Physiol Mol Biol Plants 25(5): 1107-1119.

[7] Soja G, Kunsch B, Gerzabek M, Reichenauer T, Soja AM, Rippar G, Bolhar- Nordenkampf HR (2003) Growth and yield of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) near a high voltage transmission line. Bioelectromagnetics. 24(2): 91 - 102.

[8] Li X, Liu X, Wan B, Li X, Li M, Zhu H, Hua H (2019). Effects of continuous exposure to power frequency electric fields on soybean Glycine max. J Environ Radioact 204: 35-41.5.