There are many good reasons to celebrate trees. Being in close proximity to them brings a feeling of calmness and peace. Trees give us food, shelter and provided the medium (paper) for the wide dissemination of knowledge that allowed our civilization to flourish.
Aside from those reasons to celebrate trees they have a quality that I am fond of calling "pattern but not pattern" that makes them an interesting and challenging sculpture subject and why we find them beautiful I believe. My sculptures are made to celebrate trees, understand and replicate this pattern but not pattern and understand how trees react to all the factors in their environment.
Trees can survive just fine without us. I see no way we could survive without them.