There is quite a lot of information on the non-thermal effects of radio frequencies on trees on the BEMRI website. See
What evidence is there for this? According to studies made in the 1990's on the effects of the VHF radar station at Skrunda in Latvia, the growth rings of trees were reduced during the period in which the station was operational and the pine needles made more resin (an indication of cellular stress). Incidentally, just for the record, a parallel study on the performance of schoolchildren in tests was significantly reduced in the main beam of the station compared with those in relative safety behind the antennas.
For my part, I was first alerted to these effects many years ago by a couple of Forestry Commission workers who thought that Die-back in Oak was correlated with the path of microwave transmission links, where they skimmed the surface of the trees. At first, I didn't believe it; that is until I saw what was happening to the trees around an old and powerful Vodafone mast near my local park. Many of the Oaks in the park within about 400 metres of the mast are suffering from severe die-back and one is now just a dead skeleton. Many of the badly damaged and dead trees have now been removed by the council, including many conifers and a whole row of dead Silver Birch extending up to about 300 metres from the Mast. The symptoms are those of drought, abnormal growth patterns, cancer-like growths beneath the bark ,and fungal disease.
Most of these effects can be attributed to the effects of the radio waves on the pigment cryptochrome. This is one of many pigments used by plants to detect the presence and wavelength of light, but most important of all, it forms a vital part of the biological clock that controls their circadian rhythms and it is also affected by radio waves. The mechanism of its radio sensitivity depends on the quantum mechanics of an electron's ability to move between two free radicals. This was first discovered by Ritz and his co-workers (Nature 249: May 13th, 177-180, 2004) in relation to magnetic navigation in robins, which use cryptochrome to sense the direction of the Earth's magnetic field. Navigation was upset by a broad range of frequencies up to about 7MHz. If this is also true of the cryptochrome that controls the biological clock in plant cells, then modulated or pulsed radiation containing any of these frequencies could upset their circadian rhythms and have potentially devastating effects.
Circadian rhythms are important in both animals and plants because they enable them to anticipate the arrival of dawn and dusk to get their enzymes and metabolic pathways ready in time (See "Introducing Biological Rhythms". Koukkari and Sothern: Springer 2006). In plants, they begin opening the stomata and synthesising photosynthetic enzymes before dawn. In both plants and animals, they control the immune system. In plants, it works best during the day when there is spare energy available from photosynthesis, but in animals it works best when we are asleep at night when the lack if physical activity make more energy available for it.
These circadian rhythms can usually go on for several cycles without external signals from the environment, but eventually they fade out under constant conditions. When this happens, at no time will the immune system function at maximum efficiency and the animal or plant becomes more susceptible to disease. Although much of the work has not yet been published, studies in the Netherlands indicate that in some plants at least, modulated microwaves cause these circadian rhythms to fade out, with a partial loss of immune function.
Photographic studies made in the Netherlands and throughout Europe has also shown a progressive increase in the occurrence of tumour-like growths beneath the bark of urban trees over the last decade or so, which corresponds in time to the increases usage of mobile phones and WiFi. There also seems to be an increase in splits in the bark, which then become infected by various organisms and could be a mode of entry for various pathogens, which, together with a loss of immune function, could be the perfect storm.
All this needs checking out with a properly funded and independent research programme, and if governments are not prepared to do this, we must surely ask why.
Dr Andrew Goldsworthy
Lecturer in Biology (retired)
Imperial College London