The goal of SNR (shelter, neuter, and release) is to help prevent overpopulation of outdoor cats, who can’t really fend for themselves. They help reduce the population by vaccinating them, spay or neutering, and returning them from where they came from.
The community program at NHS is really helpful not only or the environment but also for cats, whose left alone to wander or isn’t a good candidate for adoption. The program helped saved over 350 cat lives.