The best existing alternative to TNR is public education on the importance of spaying and neutering pets. While educating the public is not incredibly useful in managing the existing feral cat and dog populations, informing the public about responsible pet ownership is crucial in preventing the proliferation of new colonies.
Many argue that if some of the funds for TNR were reallocated toward public education and support of animal control ordinances, we would be making much faster progress toward eliminating stray cat and dog populations (Winter, 2004). Others argue it will require a combination of trap and neuter tactics, increased education, and more effective licensing and confinement laws to effectively manage feral cat and dog populations (Barrows, 2004).
If the reader were to have one take-away from perusing this site, it should be this:
Although there is no obvious immediate solution for the existing feral cat and dog epidemic, the most effective means of ensuring a reduction of these populations in the future is to educate people on the issue. If more of the human population were informed about the risks associated with keeping cats and and dogs intact, fewer people would be opposed to the procedure, and feral communities worldwide would likely diminish.