Because One Hundred Years of Solitude is a magical realist novel, the supernatural is a strong and ever-present element in its plotting and character development. It's a force like the weather, or time: powerful, unstoppable, and beyond the control of most of the novel's characters. Magical effects usually highlight the emotional side of events, but their consequences are almost always negative and destructive. Even in those few instances where the supernatural seems to be beneficial, it almost always turns out to be a pact with the devil for the characters, who suffer immediate reversals of fortune.
By using a constant stream of predictions, curses, and prophesies that always end up coming true, One Hundred Years of Solitude works against the common perception that revealing twists in the plot (spoiling them, as it were) will make a reader less interested in it.
In the world of Macondo, technology and technological advancement are the true magic. They, and not any of the actual supernatural things that happen, are responsible for all the town's major transformations.