It's only living objects so I guess that does kinda still include grass and stuff. Hmm. That's tricky. What do you mean by rewrite? He can't change things that have already happened. Villains can still kill superheroes and he can't stop that. He alters time, but it's not like time travel. He can't physically go back to the past to change things, his powers can only target one complete thing, size doesnt matter. So, if he were to touch the grass on the earth all that would be affected is one blade of grass, Maybe it would become so old it would naturally die, but everything else would be fine. However, if he were to touch a tree the roots, leaves, and branches would be affected. His powers aren't all that...well, powerful, under the right circumstances. He's good for recon and brainwashing/mind control reversal, and...Oh, I think I get why you're worried. Don't worry, i'll find some way to word it so that he can't take away powers among other things.