Alienforming Terra
Any life form capable of traveling to Earth would be so exceedingly superior to humans that they could do anything here they damn well pleased, including alienforming the Earth to suit their needs. If we're lucky they'd keep a few of us around as pets, or maybe use the lowly humans for recreational purposes. Wild throngs of aliens would cheer as they gamble away spacebucks at the human racetracks and gladiator pits.