Forest trees

Some studies have dealt with possible negative effects of high-frequency electromagnetic fields on forest trees. In several systematic long-term studies carried out in Switzerland around radio and television transmitters ^{[1, 2]} or under exposure to 2,450 MHz over several years at power flux densities of 0.007 to 300 W/m2 ^[3], no negative effects on spruce, fir, pine, or beech trees were found. A reduction in thickness growth of pine trees was observed around the Lithuanian radar station in Skrunda ^[4]. An observational study from the US showed improved growth in young poplars when electromagnetic fields were shielded ^[5].

Study on the influence of radar radiation on beech and spruce treesn

The effect of electromagnetic fields on beech and spruce was tested in a three-year study ^[6]. For this purpose, entire crown areas were exposed to defined irradiation by radar during the vegetation periods. There was no effect on the experimental trees.

Under the given conditions, electromagnetic fields do not pose an obvious risk of damage to forest trees. The transmitting power of mobile communications base stations is much lower than that of the powerful transmitters examined here. Therefore, no negative influence of electromagnetic fields on plants is to be expected in their environment.

Tree damage around base stations

In contrast, there have been reports of damaged trees near mobile communications base stations ^[7]. 620 sites were visited, and six concrete examples are documented in the publication.

For another, more detailed publication ^[8], trees were observed in Bamberg and Hallstadt from 2006 to 2015. Quantitative data were also collected in 2015. Sixty unilaterally damaged exposed trees with a view to a base station and 30 non-exposed healthy trees were selected. Only 30 trees were randomly selected. Measurements showed a higher exposure to high-frequency electromagnetic fields on the damaged side of the tree than on the other side or on healthy trees. All measured values for the high-frequency electromagnetic fields were well below the limit values.

The cause of one-sided damage to trees does not necessarily have to be a base station. Other factors such as climatic factors (which were discussed but not completely ruled out) are also possible. A qualitative deficiency is the selective and not exclusively random choice of trees. The observational study presented can prove a temporal and spatial but not a causal relationship.

Surveys on forest condition

The condition of forests is reviewed at regular intervals by experts and presented in reports on forest condition by the Federal Ministry of Food and Agriculture (BMEL) (only in german). The surveys have been conducted annually since 1984. A clear trend towards deterioration in the condition of deciduous trees – visible from crown defoliation – is discernible; however, this had already begun before the introduction of mobile communications. Climate change is currently playing the biggest role.

References

[1] Joos K, Masumy SA, Schweingruber FH, Stäger C (1988) Untersuchung über mögliche Einflüsse hochfrequenter elektromagnetischer Wellen auf den Wald. Techn. Mitt PTT 1: 1 - 23

[2] Stäger C 1989 Felduntersuchung über eventuelle Schadenwirkungen von Mikrowellen auf den Wald. Techn. Mitt. PTT 67: 517 - 526.

[3] Schmutz P, Siegenthaler J, Stäger C, Trajan D, Bucher JB (1994) Long-term exposure of young spruce and beech trees to 2450 MHz microwave radiation. Science of the Total Environment 180(1):43 - 48

[4] Balodis V, Brumelis G, Kalviskis K, Nikodemus O, Tjarve D, Znotina V (1996) Does the Skrunda Radio Location Station diminish the radial growth of pine trees? Science of the Total Environment. 180(1): 57 - 64

[5] Haggerty K (2010). Adverse Influence of Radio Frequency Background on Trembling Aspen Seedlings: Preliminary Observations. International Journal of Forestry Research 2010: 1-7.

[6] Götz G, Matyssek R, Käs G (2001) Fichte und Buche unter dem Einfluss von Radarbestrahlung. Allgemeine Forst- und Jagdzeitung 172(4): 74 - 78

[7] Waldmann-Selsam C, Eger E (2013) Baumschäden im Umkreis von Mobilfunksendeanlagen. Umwelt Medizin Gesellschaft 26(3): 198 - 208

[8] Waldmann-Selsam C, Balmori-de la Puente A, Breunig H, Balmori A. (2016) Radiofrequency radiation injures trees around mobile phone base stations .Sci Total Environ. 572: 554-569