IMHO, the problem is caused initially by human beings, and the cats are used as scapegoats. TNR has been shown (alleycatallies.org) to stabilize populations; they just did a story on the New York news about a colony in a town in NJ where the population has dropped by 80% (!!) in five years.

Until all who own cats properly care for, spay and neuter them, and puppy/kitten mills are made illegal, strays will be a problem. TNR is the best of a bad lot of alternatives.