The findings based on seven years of research by nine Oldenburg scientists, in cooperation with Prof. Dr. Peter J. Hore of Oxford University, are now available in a paper entitled „Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird“, published in the latest issue of the renowned scientific journal Nature. Nature underlines the importance of this study by making it the cover story of its May 15th issue.
„In our experiments we were able to document a clear and reproducible effect of human-made electromagnetic fields on a vertebrate. This interference does not stem from power lines or mobile phone networks“, Mouritsen stresses, explaining that electromagnetic interference within the two kilohertz to five megahertz frequency range is mainly generated by electronic devices. „The effects of these weak electromagnetic fields are remarkable: they disrupt the functioning of an entire sensory system in a healthy higher vertebrate.“
It all started with a stroke of luck. For around 50 years it has been known that migratory birds use the Earth’s magnetic field to determine their migratory direction. Biologists have proven this in numerous experiments in which they tested the birds‘ navigation abilities in so-called orientation cages. „So we were surprised when robins kept in wooden huts on the Oldenburg University campus were unable to use their magnetic compass“, Mouritsen recounts. Dr. Nils-Lasse Schneider, an electrophysiologist and researcher in Mouritsen’s work group, then came up with the idea that set things in motion: he proposed covering the wooden huts, along with the orientation cages they contained, with sheets of aluminium. This did not affect the Earth’s magnetic field, which is vital for the birds to navigate, but it strongly attenuated the time-dependent electromagnetic interference – the electrosmog – inside the huts. The effect was astounding: suddenly the birds‘ orientation problems disappeared. „Our measurements of the interferences indicated that we had accidentally discovered a biological system that is sensitive to anthropogenic electromagnetic noise generated by humans in the frequency range up to five megahertz“, Mouritsen says. The surprising thing here, the biologist adds, was that the intensity of the interference was far below the limits defined by the International Commission on Non-Ionizing Radiation Protection and the WHO.
Considering the potential importance of the finding, Mouritsen and his team performed a large number of experiments to provide evidence of the effect they observed: “Over the course of seven years we carried out numerous experiments and collected reliable evidence, in order to be absolutely certain that the effect actually exists.” Under the leadership of Svenja Engels, Mourtisen’s doctorate students conducted numerous so-called double-blind studies. Several generations of students repeated the experiments independently of one another on the Oldenburg campus. What they found was that as soon the grounding of the screens was disconnected or electromagnetic broadband interference was deliberately created inside the aluminium-clad and earthed wooden huts, the birds‘ magnetic orientation ability was immediately lost again.
Furthermore, the scientists were able to show that the disruptive effects were generated by electromagnetic fields that cover a much broader frequency range at a much lower intensity than previous studies had suggested. This electromagnetic broadband interference is omnipresent in urban environments. It is created wherever people use electronic devices. As expected, it is significantly weaker in rural areas. And indeed, unlike on the University campus, the magnetic compass of the robin did function in orientation cages placed one to two kilometres outside city limits, even without any screening. “Thus, the effect of anthropogenic electromagnetic noise on bird migration is localised. However these findings should make us think – both about the survival of migratory birds as well as about the potential effects for human beings, which have yet to be investigated”, Mouritsen concludes.
Prof. Dr. Henrik Mouritsen has been teaching and conducting research at the University of Oldenburg since 2002, and obtained his habilitation there in 2005. The Danish biologist has held a Lichtenberg Professorship from the VolkswagenStiftung since 2007. Through its “Lichtenberg Professorships” initiative the foundation funds outstanding scientists in innovative fields of teaching and research. Mouritsen researches the behavioural, molecular, physiological and cognitive mechanisms underlying long-distance navigational abilities in migratory birds. As head of the international research group “Neurosensorik/Animal Navigation” he has contributed substantially to the current state of the art suggesting that the birds use the Earth’s magnetic field for orientation in two different ways. Light-sensitive molecules in their eyes enable them to visually detect the compass direction of the magnetic field. Furthermore, the birds seem to have magnetic sensors associated with the ophthalmic branch of the trigeminal nerve, which are connected via neural pathways to the brainstem. Mouritsen’s group identified for the first time the areas in the birds‘ brains involved in both these orientation systems.
“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.