The Dutch Atennebureau is studying the effects of Wifi on Trees. The results are inconclusive; Ash might be affected, but the report is unable to prove causation and says more research is necessary.

In een uitgebreider en langer durend onderzoek naar de invloed van vergelijkbare WIFI signalen is geen invloed gevonden op de ontwikkeling van sparren en beuken. Bij enkele onderzoeken zijn wel effecten gevonden, maar daar werden dusdanige sterke blootstellingen gebruikt dat warmte-effecten aannemelijk zijn.

(A broader, longer-term study of the influence of comparable WIFI signals found no effect on the development of spruce and beech. Some studies have found effects, but there were such high exposures used that heat effects are likely.)

You know you have a strong WiFi signal when leaves on trees around you burst into flames. You may need to worry about other security risks first, however, at that point.