A team of researchers led by Oldenburg biologist Prof Dr Henrik Mouritsen has now been able to prove this for the first time: The magnetic compass of robins fails completely as soon as the birds are exposed to electromagnetic interference in the medium wave range.
Electrosmog has no effect on biological processes or even human health below certain threshold values - this was previously considered the state of scientific knowledge. A team of researchers led by Prof Dr Henrik Mouritsen, biologist and Lichtenberg Professor at the University of Oldenburg, has now been able to prove this for the first time: The magnetic compass of robins fails completely as soon as the birds are exposed to electromagnetic interference in the medium wave range - even if the signals are only one thousandth of the limit value classified as harmless by the World Health Organisation (WHO).
The long-term research carried out by the nine Oldenburg scientists together with Prof Dr Peter J. Hore from the University of Oxford (UK) has now been published in the current issue of the renowned English-language journal Nature under the title "Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird". Nature underlines the importance of the study by making it the cover story of the 15 May issue.
"With our experiments, we were able to document a clear and reproducible effect of human-induced electromagnetic fields on a vertebrate. This interference does not come from power lines or mobile phone networks," emphasises Mouritsen. The electromagnetic noise in the frequency range of two kilohertz to five megahertz comes mainly from electrical appliances. "The effects of the weak electromagnetic fields are remarkable: they disrupt the function of an entire sensory system in a healthy higher vertebrate."
It all started by chance: it has been known for around fifty years that migratory birds use the Earth's magnetic field to determine their migration direction in spring and autumn. Biologists have been able to prove this in numerous experiments in which they investigated the birds' navigation skills in so-called orientation cages. "We were therefore surprised when we realised during our experiments that robins in wooden huts on the campus of the University of Oldenburg were unable to use their magnetic compass," explains Mouritsen.
Dr Nils-Lasse Schneider, electrophysiologist and research assistant in Mouritsen's working group, had the brilliant idea: he suggested shielding the experimental huts and thus also the orientation cages with earthed aluminium plates. The shielding left the earth's static magnetic field, which is crucial for the birds' navigation, unaffected, but attenuated the time-dependent electromagnetic noise - the electrosmog - inside the huts.
The effect was astounding: the birds suddenly had no more problems orientating themselves and found their migration direction. "Our measurements of the interference indicated that we had accidentally discovered a biological system that reacts sensitively to human-induced electrosmog in the frequency range up to five megahertz," says Mouritsen. The surprising thing was: The intensity of the interference was far below the limits set by the International Commission on Non-Ionising Radiation Protection (ICNIRP) and the WHO, says the biologist.
Proving the observed effect with certainty was a major challenge for Mouritsen and his team: "We deliberately carried out numerous experiments over seven years and collected reliable evidence to be absolutely certain that the effect actually exists." His doctoral candidates, led by Svenja Engels, conducted numerous so-called double-blind experiments. Several generations of students repeated the experiments independently of each other on the Oldenburg campus. The results showed that as soon as the earthing was removed or the electromagnetic broadband noise was intentionally generated within the shielded and earthed wooden huts, the birds lost their ability to orientate themselves magnetically.
The scientists were also able to prove this: The interference effects are caused by electromagnetic fields that cover a much broader frequency range at a much lower intensity than previous studies had suggested. This electromagnetic broadband noise is omnipresent in urban environments. It is generated wherever people use electrical devices. As expected, it is much weaker in rural areas. And indeed: unlike on the university campus, the robins' magnetic compass worked in orientation cages set up one to two kilometres outside the city gates, even without shielding or earthing. "Of course, the effects of electrosmog on bird migration are therefore localised. Nevertheless, these results should give us food for thought - both in terms of the migratory birds' chances of survival and the possible effects on humans, which still need to be investigated," says Mouritsen.
"Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird" by Svenja Engels, Nils-Lasse Schneider, Nele Lefeldt, Christine Maira Hein, Manuela Zapka, Andreas Michalik, Dana Elbers, Achim Kittel, P.J. Hore, Henrik Mouritsen, Nature.