Not sure how my statement relates to what you've stated, L4H. My remark is about the irresponsibility of allowing cats to roam and the fact that people who do so, will likely continue to do so.
I don't think the issue is all about wildlife, although I know there is an impact. (I've seen the predation by pets first hand during nesting season in a county park I used to frequent--both stray/feral cats with birds in mouth, and even a lab with a whole nest of warbler chicks in his mouth. That's on top of natural predation.) But still, the issue is not all about the wildlife--the issue is more about the cats and looking for ways to make owners more responsible for them.
You've found a way to keep your cats stimulated by supervising their trips outside--that's so much different than allowing them to roam at will and having them run afoul of traffic or predators. Did you know that in my township, there is no population of stray animals? That's because it's so dangerous here for them--we have fishers, coyotes, wolves, bobcats and the occasional cougar, any of whom are probably more than willing to take strays. So anyone dumping here or allowing their animal (cat or dog) to roam, is sentencing them to quick death.
Much better to encourage them to keep the animals at home and under supervision if outside. If licensing of cats would increase awareness, I'm all for it. If the penalty for allowing them to roam is hefty, so much the better--maybe it will make them think twice before allowing their cat to roam.
I suspect that the truly irresponsible ones will simply remove the tags and allow their cat to roam, regardless. And of course, the dumping will continue.
The only dumped cat that I know has survived was the one that made its way into my backyard a few years back. The Pack treed him and it came to me when they were put inside--and he is the only stray cat I know of from this township that has made it to the shelter and been adopted.
But the results Marko mentioned from Calgary are promising. Cutting the euth rate in half is a remarkable beginning.