Trees are the answer

Most often seen on the automobiles of environmentally conscious American urban citizens, these bumper stickers are a study in absurd texts. For instance:

1. What exactly is the question? While I don't doubt the importance of trees when it comes to CO₂-O₂ exchange and having the critical base material for spitballs and paper airplanes, it helps to have a clear question if we're going to have such a definitive, unequivocal answer.
2. Why do we have bumper stickers for this? It's not such a long jump to correlate driving a car with damaging trees. Most cars consume gasoline or diesel fuel, the harmful fumes of which damage all sorts of flora and fauna. If someone is advocating trees, why would he engage in an activity that can harm them?
3. What action or change of thought does this text mean to evoke in the reader? I've never known anyone to have a fundamental change in thought or worldview from having seen these bumper stickers. But then again, you might say that about any bumper sticker.

Though the National Arbor Day Foundation produces and sells these bumper stickers, it doesn't seem that any one organization has a trademark on this phrase. A quick websearch shows a number of scholarly papers, informational videotapes, and pamphlets for community-based tree planting programs.