Peeling bark, withered leaves and dying tissue: The trees in the Dutch town of Alphen aan den Rijn didn't look so good. Town leaders commissioned scientists to find out why, and WLAN networks may be the culprit.
Researchers ask whether WiFi could be making trees sick
Wireless Internet access points could have a negative effect on the health of plants, according to a study to be presented early next year by researchers in the Netherlands. The research was conducted after officials from the town of Alphen aan den Rijn in Holland noticed problems with many local trees and contacted scientists at Wageningen University to examine the issue.
In the study that followed, trees were exposed for more than three months to six sources of WiFi radiation. Researchers used wireless frequencies ranging between 2412 to 2472 MHz, levels standard for wireless access points.
A summary of the findings published on Wageningen University's website states that trees located around 50 centimeters (1.6 feet) away from the WiFi sources began to "show a metallic luster, followed by desiccation and death of part of the leaf."
But the researchers involved have stressed that the findings are preliminary and warrant more research before firm conclusions can be drawn about the relationship between WiFi and plant health.
"I think it's too early for alarm about this. The study that we have completed was a pilot study over three to four months, and we want to continue work on the issue now with more controls," said head researcher Andre van Lammeren in an interview with Deutsche Welle.
Dutch trees have been showing a number of curious symptoms from trunk to leaves
Although the pilot study was commissioned by a single town, van Lammeren was part of a research group that has identified broader problems with plant life in the Netherlands.
In a separate study, he and his colleagues found that up to 70 percent of deciduous trees in urban areas showed abnormal formations on their stems. The percentage of affected trees has gone up decisively within the last five years.
"We didn't find any specific link between that study and the study we have just undertaken," said van Lammeren, who stressed that the trees showed different symptoms in the two studies.
In the pilot study commissioned by Alphen aan den Rijn, 20 plants were placed in one of two climate chambers. One chamber had no wireless access points, and the other did; only in the chamber with wireless points did the tree leaves show the necrosis described above.
The finding is significant enough to warrant a second study with different controls concerning the type of plants used and the longevity of the experiment, Dr. van Lammeren told Deutsche Welle.
In response to the summary issued by Dr. van Lammeren's research group, an agency known as the Dutch Knowledge Platform on Electromagnetic Fields performed an initial review of scientific literature on WLAN and plant damage. According to the agency's General Secretary Ronald van der Graaf, at least one study contravenes the findings of van Lammeren's group.
"The most relevant study we've found so far was undertaken by a Swiss federal institute on forestry," van der Graaf told Deutsche Welle. "Their study looked at spruce and beech trees under a more extended range of densities than in the Dutch study, and under normal conditions, they found no harmful consequences for the plants."
Only when the radiation was increased beyond legal levels did the plants incur damage - through heat and thermal effects, van der Graaf added.
As more devices go wireless, researchers and lawmakers consider safety issues
When it comes to the health impact of radiation emitted by wireless devices, many countries, including Germany, have already established legal limits and set aside agencies responsible for tracking the issue.
"WLAN uses a similar technology to mobile phones, but the radiation emitted is weaker," said Anja Schulte-Lutz of Germany's Federal Office for Radiation Protection. "And travelling even a small distance away from a WLAN router leads the radiation levels to drop drastically."
That fact could explain why the plants further than 50 centimeters from the hubs in the Dutch pilot experiment didn't show symptoms to the same extent as those nearest the access points.
When it comes to human health, the UK-based Health Protection Agency has compiled and conducted extensive research on whether WLAN could harm people.
Spokesmen for the HPA stress that consistent evidence hasn't been found that could show a link between WiFi radiation and health problems. The public agency does not advocate limiting WLAN use in schools and homes.
But whether the HPA's recommendations are also suitable for the health of plants and trees remains to be seen.
Author: Greg Wiser
Editor: Nathan Witkop