More on anthropogenic tree and forest die-back; Cell Phone antennas revisited and a separate and additional mechanism involving high voltage electricity direct and indirect routes, by Dr Chris Barnes August 2013. 



Accepted mechanisms for natural and anthropogenic tree/forest die back are summarised and briefly reviewed. Die-back due to mobile phone base station emissions is briefly revisited. A new observation of significant swathes of die back near high voltage conductors has been made and is explained in terms of a focusing effect of atmospheric pollution aerosols. Concurrent effects of electric ground currents and electromagnetic fields on these processes are also examined. Cable under-grounding is suggested as a mitigating route.


Forest die-back has been noted in various countries of the world since approximately the 1950's. Since mortality rates have increased in all age groups of trees die-back cannot be simply attributed to forest ageing, see van Mantgem et al ( 2008) (1) who have noted a widespread increase in tree mortality rates in the Western USA and also attributed die-back to climatic processes.


Both natural and anthropogenic processes have been blamed for die-back and combinations of the two. Amongst natural processes are included ecological processes such bank cutting and flooding, see Franklin et al ( 1987) (2). Natural predators such as beetles can also be a problem, see Mueller-Dombois (1987) (3). Natural pathogens such a fungi also play a species specific part particularly in oak die-back, see Kubikova (1991) (4) for forest die-back in Czechoslovakia and now the oak is further threatened by the oak Processionary Moth (OPM) (5). Elms were decimated in England by a symbiotic combination of Fungi and Beetle, the notorious Sac Fungi being spread by the elm bark beetle (6).


Perhaps the most commonly blamed anthropogenic cause of forest decline is acid deposition, see Johnson and Siccama (1983), (7).


Tree dieback forms part of a wider classification of so called plant EIDS ( emerging infectious diseases), see Anderson et al 2004 (8). Taking on board the work of Anderson we can regard parasites, such as Dutch Elm and the OPM to be EIDS as they have been introduced by human activity although severe weather events may also be a driver of such disease emergence by stressing plants.


Hain(1987) (9) has suggested that there may be a complex interaction between insects, trees and air pollutants. Since stress in trees increases the tissue content of soluble nitrogenous compounds which in turn makes them a more attractive and suitable food source for invertebrate herbivores. Thus suddenly innocuous insects may become voracious pests. Hain has further suggested that variable tree mortality patterns may fit with locally distributed air pollutants.


The present author has recently shown a brand new association between species independent die-back and cell phone antennas (10). The die-back is most pronounced when trees grow in the vicinity of cell phone antennas near busy roads. The hypothesis is that the road traffic supplies nano-particle pollution which is adsorbed onto and absorbed into tree leaf and root systems. Thus there is a double stress factor to which the trees succumb. The concurrent insect mechanism of Hain (9) above is not ruled out and indeed could well be contributory.


An additional mechanism involving high voltage electricity direct and indirect routes.

The present author has recently noticed that in addition to species unspecific die-back which seems to be occurring at Cell Phone masts and specific integer distances there from there is also similar die back in the region of overhead a.c. electricity transmission lines, particularly super-grid conductors. An example of a locality where this is particularly prevalent is in a a North Wales valley adjacent to a local Gwynedd beauty spot known as Aber Falls. The Valley is over passed by three sets of paralleled electricity transmission lines at 67KV, 132KV and 440KV double circuit in perhaps one of the widest tower to tower spans in the whole UK. There are no nearby cell phone towers or TV Transmitters yet there are significant swathes of dead and dying trees in the valley below and to the sides of the cable spans.


We are now in a position to make a new and novel link. Pollutant aerosols are known to be a significant public health risk and their concentration to be associated with high voltage power lines, see Fews and Henshaw et al 1999 ( 11) and Henshaw 2002 (12). Thus, combining this knowledge, the present author's observations and the work of Hain (9) yields a simple explanation for increased tree death in the region of power lines.


It is possible that there are more complex and concurrent facets of the hypothesis. For example, due to the length of the cable runs and possible anti-phase interactions between the different voltage lines there could potentially be significant ground currents flowing across the valley concerned. There is a very limited amount of work in the literature but Black et al (1971) (13) have shown that electrical ground currents can first increase and then stunt plant growth (tomatoes) depending on magnitude in the microampere range.


It is also possible that there is a direct effect of electric field or corona ions but the literature is relatively silent here. Davies (1988) (14) has explored the effects of 60 Hz electromagnetic fields on plants and produced inconclusive results. On the other hand and for a specifically studied pant, namely duckweed, Ben-Izhak Monselise 2003 (15) et al have shown very distinctive increases in the stress amino acid alanine for both 60 and 100 Hz fields. If this were replicated in trees then it would also help make them more palatable to insects, and link as a second associative cause of stress in addition to the air pollutants mentioned above.


A new hypothesis which admirably accounts for species independent forest die-back in the region of high voltage electrical transmission lines has been advanced. The hypothesis is broadly supported by experimental observation and a collation of previous work in the plant and tree biology and other fields. Briefly, the power lines concentrate atmospheric pollutants the presence of which which will increase stress and susceptibility to insect herbivores in all species of trees. It is additionally possible that electrical ground currents could further suppress growth. It has not been possible to reach a conclusion on the effect of air to ground electrical field or coronal ions on trees. Finally if trees behave like duckweed in the presence of electromagnetic fields then a third concurrent stress pathway may exist which could be checked for by the presence of alanine. This would certainly make their tissue more palatable to herbivore invertebrates.


As more and more socio-economic development proceeds in the world, so will our thirst for electrical energy. This is expected to put even more of a strain on any wooded or forested areas over-passed by high voltage conductors and thus an argument for under-grounding is supported.



  1. Van Mantgem et al (2009)