Mavic pro at full speed head on vs. a dense evergreen: sensors will start to stop it but I think not in time to avoid collision.
Mavic pro at full speed tripod mode head on vs. a dense evergreen: sensors will stop it and avoid collision
Mavic pro vs. deciduous tree with sparse branches/leaves at any speed: Likely that it will fly into the tree.
With that said, I agree with old man and try my best to avoid trees altogether