A new study coming out of the Netherlands suggests that radiation given off by wi-fi is causing trees to becoming ill forming strange growths, as well as bleeding and fissures in the bark. This is apparently present in trees in most cities, while trees out in the wilderness don't have this problem at all. The researchers believe that besides wi-fi, mobile phone networks and ultra fine particles from vehicles are what is causing this. While worrisome, this does appear to still be early research into the matter, and the scientists involved with it emphasize that they still have a lot more work to do to finalize their results.
Nonetheless, it does raise the question of how safe all of these radio waves are flying through the air all around us. If there's the possibility that these things are making trees sick, what sort of affect could they be having on us, or any other living thing for that matter. Something to think about, I suppose.