G-d runs the world but hides Himself behind nature. Yes, one can look at a tree and its fruit and realize how it is all from Hashem or some one can easily explain it as its just nature. If it would be so clear that HaShem runs the world than we would have no bechira to have emuna but because HaShem disguises Himself in teva, it is up to us to find Him in nature.
Zhavasdad,
i thind that there are ways to prove G-d in this world but there are people that will rather take clear proofs that there is a G-d running the world and explain it according to nature. So yes, everything really douse come down to having emuna!!