Overpopulation is the number one cause of death of healthy pet cats in the USA.
Every year, in Louisiana alone, about 40,000 are killed in shelters and every day approximately 25,000 cats die in US shelters because nobody came to adopt them.
Through spay and neuter these killings are preventable. Wild Cat Foundation focuses on prevention by making spay/neuter accessible to community cats and kittens, ferals, strays, and rescues.
Many thanks to Neighborhood Cats for providing the following text.
At its essence, TNR is not about rescuing cats, it's about population control and permanently reducing the number of feral cats in an area. It's not about getting a wonderful cat a great home, it's about lowering stray intake and euthanasia rates, reducing costs for animal control, and creating better, less hostile environments for the cats. In addition, spay/neuter of the cats eliminates common nuisance behaviors such as yowling and foul odor, and vaccinating them for rabies also provides a public health benefit.
TNR has many advantages. It immediately stabilizes the size of the colony by eliminating new litters. The nuisance behavior often associated with feral cats is dramatically reduced, including the yowling and fighting that come with mating activity and the odor of unneutered males spraying to mark their territory. The returned colony also guards its territory, preventing unneutered cats from moving in and beginning the cycle of overpopulation and problem behavior anew. Particularly in urban areas, the cats continue to provide natural rodent control.
Another significant advantage to TNR is that, when practiced on a large scale, it lessens the number of kittens and cats flowing into local shelters. This results in lower euthanasia rates and the increased adoption of cats already in the shelters.
TNR is not just the best alternative to managing feral cat
populations - it is the only one that works. Doing nothing has
resulted in the current overpopulation crisis.. Trying to "rescue"
the cats and find them all homes is utopian and unattainable given
their numbers and the futility of trying to socialize most of them.
Feral cats are community cats living within their colony which is
their family. Trap and remove, the traditional technique exercised by
animal control, is simply ineffective. If all the cats are not
caught, then the ones left behind breed until the former population
level is reached. Even if all the cats are removed, new unneutered
cats tend to move in to take advantage of whatever food source there
was, and the cycle starts again.
This explains why more and more animal control agencies are willing
to try TNR.