Powerlines disturb animal habitats by appearing as disturbing flashes of UV light invisible to the human eye.
Wild animals see overhead power cables in remote regions of the countryside as disturbing lines of flashing lights, which could explain why many species avoid electricity pylons to the point where their natural territories become seriously fragmented, scientists said.
A study of wild reindeer in Norway has shown that they can see overhead power lines in the dark because their eyes are sensitive to the flashes of ultraviolet light which are invisible to the human eye but are constantly being emitted by high-voltage electrical transmission, the researchers said.
Many other species, from birds in the Arctic to elephants in Africa, can also see ultraviolet radiation which may explain why different kinds of animals in widely varying habitats all tend to avoid overhead power lines even though they are considered to be inert and invisible to wildlife, they said.
The adult human eye can only see wavelengths of light down to the blue-violet end of the visible spectrum but other animals are able to see well into the ultraviolet range. Reindeer for instance have reflective surfaces at the back of the eye that help them to see UV light on dark winter days, said Professor Glen Jeffery of University College London.
“Reindeer see deep into the UV range because the Arctic is especially rich in UV light. Insulators on power lines give off flashes of UV light,” Professor Jeffery said.
“The animals potentially see not just a few flashes but a line of flashes extending right across the horizon. This is the first bit of evidence that explains why we think they are avoiding power lines,” he said.
High-voltage power cables cause a build-up of ionised gas at certain points on the overhead lines which results in an overall UV glow with occasional, random flashes of UV light as the ionised gases or corona suddenly dissipate. Power companies try to minimise the phenomenon because it causes power leakage, but not to the extent of eliminating them altogether, Professor Jeffery said.
Scientists also know that many animals avoid power lines to the point that it sometimes causes their populations to fragment into separate habitats. But until now the observation could not be easily explained, especially as the avoidance goes on for many decades after the power lines were first erected.
“Animals avoid man-made structures and, in the case of high voltage power lines, this can be by several kilometres. This is perplexing because the suspended cables are neither a physical barrier nor are they associated with human activity,” Professor Jeffery said.
“New information about animal vision along with the characteristics of power lines provides strong evidence that the avoidance may be linked with animals’ ability to detect ultraviolet flashing on power lines that humans cannot see and which they find frightening,” he said.
Anatomical studies of the eyes of about 35 species show that many of them are sensitive to ultraviolet radiation which could help to explain the fragmentation of many remote wildlife habitats from the Arctic to Africa, he added.
The study, published in the journal Conservation Biology and funded by the Biotechnology and Biological Sciences Research Council, analysed the UV corona associated with power lines in southern Norway, where there are now 23 distinct populations of wild reindeer as a result of habitat fragmentation caused by human infrastructure such as roads and overhead electricity cables, said Nick Tyler of the University of Tromsø in Norway.
“The loss and fragmentation of habitat is the primary threat to biodiversity and human infrastructure is a major and ubiquitous cause of both loss and fragmentation. It is a major global issue,” Dr Tyler said.