I've just replayed Dead Man Walking, one of my favorite levels in the whole game, and I tried to shoot some small trees on rooftop of a buiding and to my surprise, the trees broke and fell down. Pity that we can shoot only 5 tiny trees in that area. So yeah the trees are destructible in this game.
Edit: In the CryEngine 3 tech demo shown at GDC09, we saw the player shoot one of the palm trees ( 360/PS3 versions) but why didn't Crytek make this in Crysis 2 ?
some are destructible, most arn't.