Can Trees Suffer?

Maybe it's my constant proximity to a three year old that forces me to reevaluate long held truths, and when my kid rips the bark off the tree I yell at him, "Stop hurting the tree!"

Obviously, I'm using the word "hurt" in a physical sense. Obviously, trees don't have feelings, since they lack the complex nervous systems that we possess, and so lack the capacity for self-awareness. Or do they necessarily need a knowledge of themselves to feel pain? Does an ant feel pain when I step on it? Does a bacterium feel bad when I kill it using an antibiotic?

Or do these creatures have a basic understanding of logic as well? Doesn't a microbe put one and one together, and alter its course toward a food source? Is that not A leads to B thinking, were B makes it happy?

Let's not stop there: didn't single cell organisms start off as a chain of molecules? Didn't they have a basic level of logic and feelings in order to shift their motion in such a way as to create life? Didn't their components, atoms, have some say in this? Do electrons and protons, hell, take it all the way to elementary particles like quarks, leptons, and bosons, do they all have a minute amount of logic and feeling, insignificant compared to us, and yet when added together, become meaningful?

Do the three quarks that make up a proton feel content together? Does light emitted from the sun have a logical track that it follows, sparkling radiant happiness all the while, then is bummed out when it hits my skin? (At least until it's emitted as heat energy.)

What if ripping the bark off a tree is the equivalent of picking on a deaf, blind, mute quadriplegic? We farm trees and cut down legions of blades of grass. We unthinkingly consume animals and plant matter alike, and divert nature to our whims.

To a certain extent, we are forced to do this. Actions that entirely negate our capacity for harm are unattainable.

My issue, I suppose, is not that we must compete with other lifeforms to survive. The problem is that I have a haphazard collection of experiences and half-truths, and nothing solid to explain to a kid. These values are vapor.

Inevitably the kid asks, "Why can't we hurt the tree?" and I don't have an answer.