Now, yes, we should be diligently spaying and neutering our pets even if we intend to keep them indoors. This prevents unwanted population problems, which are presently upon us. I say this because I work for the Nashville Cat Rescue, and my inbox is inundated with intake needs and rescue missions for abandoned or feral litters.
But let's look at the history of mankind and the domestication of the feline. Cats have been painted alongside humans on cave walls, and Ancient Egyptians would mummify more cats than any other non-human creature. Historians disagree as to the origin of the domestic housecat: they argue between the Egyptian Cat and the European Wild Cat. Persian breeds were said to come from the Norwegian Forest cat.
There's a reason for this history lesson: for some reason, cats ingratiated themselves to people in a way that made them indispensible. Their rodent- and pest-control abilities proved necessary to maintaining crop integrity. Without them, insects and mice would invade homes and destroy crops (read: they ate so that we could eat). It made sense to team up with them.
So why declare cats "unenvironmental," as this site tries to do, when the real issue is overpopulation and negligence on our part as the domesticators? I mean, even the author admitted his cats had a three percent success rate. If we address our lax attitude towards fixing these animals, we won't have this misdirected, environmentally-endorsed accusation against them. We don't have to keep them locked indoors for the sake of ecological balance -- we must address the real problem and take responsibility!
That ends my rant. Stay tuned for some more misdirected environmental arguments! (And, as always, please respond to my opinion with yours!)