Actually, Baha'i faith is very much a monotheist religion. God is one (not only that, but it is the same god as in all other monotheistic faiths!), and is separated from humans and from nature, but humans can experience him both through spirituality and through science. All of these are paths to get closer to the one god.

It's a question of semantics, I guess. That God manifests himself through several things does not mean that God equals these things. For a religion to be Pantheist, nature, or the universe, must be sacred in itself and have no entity beyond that (see Carmit and Ron's lucid discussion above). It is a very basic feature of Baha'i faith that there is one God, but His nature is so unfathomable that he can only (and partially) be understood and conveyed to humans through other things.