While checking out the feral cat news as Barb's pre-set search at
Cats In the News, I found
this article, that contains the following quote concerning TNR:
The numbers charted so far show little reduction in the number of feral cats in large geographic areas, but they do show a reduction in smaller areas where TNR programs operate in conjunction with aggressive adoption and education programs.
In my experience, this is true. Until regulations and affordable spay/neuter are pervasive enough that all pet outlets (pet stores, shelters, rescue groups, "pet" breeders) are required to spay/neuter all pets before sale/adoption, and pet owners, even the lousy ones, can get a pet fixed for under $100, the overall number of cats is going to be minimally impacted.
However, TNR can solve problems in local areas. My fast food strip, for example. The Lockwood colony where one woman was stuck in her home for years caring for kittens that were born to drop off cats, and now has just four adult outdoor cats and no kittens for the last three years. Etc.
In this manner (they won't like to hear this), feral cat management via spay/neuter is a lot like the profession of wildlife control. Nuisance wildlife control doesn't impact larger animal populations. Going over to Oak Street and getting paid $400 to take care of a squirrel problem at Mrs. Jones' house does not impact the greater population of gray squirrels. But it does get the gray squirrels out of Mrs. Jones' house. Now, if you just trap the squirrels and dispose of them, but leave the holes in the house, Mrs. Jones is going to continue to have a gray squirrel problem. If you fix the holes, Mrs. Jones' squirrel problem is probably solved.
Ditto with TNR. If you just go by a place and set traps for cats and walk away, chances are good that cat problem won't be solved come spring. There will be more kittens. If you have an ongoing program in place and all cats are neutered and new cats are attended to, chances are good the problem in that location (unneutered cats, kittens being born, and an increasing population) will be solved.
This can be vital to local animal shelters. I doubt the SPCA in the county where my fast food ferals are is getting complaints about freezing cats and kittens at Burger King/McDonalds/Arbys etc, as they used to in the past. They no longer have to go down there and catch a cat or two to make people feel like they are "doing something." It's one less (big) thing for them to worry about, and they can concentrate on other things.
Now my trapper friends will likely say "Yes, but you could just get rid of those cats faster if you trapped them and just put them down." To which I say "And how many of you go back monthly to make sure no new cats show up?" They don't, of course, because no one's paying them.
The animal shelter that offers "trap and remove" doesn't go back, either. They don't have the staff or time.
Only someone dedicated to "caring" for cats will go out there every damned day to notice when a new cat shows up, and attend to it, either by finding her a home, or getting her fixed. Which is the magic key that makes TNR work.