What do you mean artificial? Rain forrests are real. You can actaually see them, feel them. They exist, so they can't be fake.
I think that, by "artificial", the question poster meant "man-made", as opposed to natural, rather than "fake" as opposed to real. In that vein...
Though we have always thought of them as natural, there is now some archaeological evidence to suggest that they were, in fact, originally planted by the native South American Indians. Which would make them man-made, and, by the question poster's intent, ARTIFICIAL.