Science is proving what spiritualities of the world have always preached and that is that there may be other consciousnesses in the universe besides ours. So if a human does not hear a tree falling, so what? If a dog is around, he or she will hear sounds we do not hear but that does not mean there is no sound.
Of course a tree still makes a sound when it falls and no one is around to hear it. It's like the butterfly effect, even small adaptations can change the route of the present. I'm sure that there are also animals in the forest who hear the tree, and the event may even draw them nearer or farther from the situation. Just because one is not personally there doesn't mean others are not effected by the outcome.