I'm trying to envision a world in which trees gave off wifi signals.
It would be a complete catastrophe. There would be so much interference that the whole 2.4 Ghz spectrum would become completely swamped and useless in all but the least densely foliated urban areas. It would become necessary to chop down nearly all of the trees around urban and suburban areas in developed nations, auguring a campaign of systematized deforestation the likes of which the world has never know.
And all because you thought it would be amusingly ironic if trees radiated wi-fi signals. Well, I hope you're proud of yourself, Dan. Because you've doomed us all.
Trees produce very little oxygen compared to grasses, shrubs and such; and all that is nothing compared to the amount of oxygen produced by Phytoplankton in the ocean. That is where the vast majority of photosythesis is occurring.
An objective person could actually consider trees a pest. The block out the sunlight for the lower growth, which is also the home of many animals. This is why the native Americans used to do controlled burns of forests. They knew that they needed grasslands in order to hunt.
Stupid hippies think trees are important and that a few people driving Priuses is going to impact the composition of out atmosphere.