not very good
first off i don't like flash movies that loop. that gives it a very unprofessional feel.
secondly, i find environmentalism of this nature to be very childish. you realize your whole argument is implicit in the assumption that a building is evil and a tree is good.
what's wrong with buildings? that is mankind's tree.
the only real reason environmentalists hate buildings in favor of trees is because they've been around buildings all their life.
if we were surrounded by trees all our life, then buildings would be precious.