Thanks for asking the question, I've often wondered for a moment(usually when I see them) what affect they have on an ecosystem. Now I have that answer and a wonderful solution I did not expect:
Trap-Neuter-Return(TNR). No worries it seems that it is easy enough to find a vet who will Neuter and Vaccinate them for free or at a very low cost.
http://www.metroanimal.org/feral/main.shtml has some great info about the feral cat issue. Including:
"Eradication has failed to reduce the feral cat population, but has increased euthanasia figures in the United States dramatically.
Cats are removed, but the food source rodents, dumpsters, etc. remains. Thus, the surviving cats have less competition for food. They will breed several times a year, quickly recolonizing. The removal creates a vacuum, which can be followed by an influx of an equal number of new cats. With the new cats, fighting and nuisance spraying increases as the new cats compete for a place in the community. In little time, you are back to square one.
An established colony will defend its territory to protect the food source, limiting the addition of new cats to the group; for this reason, leaving spayed and neutered cats in a colony is the best deterrent to population growth. The TNR approach stabilizes the colonies and eliminates many of the problems people find annoying about feral cats. Spraying and urine odor abates; mating yowls are eliminated; and fighting is reduced. "
They also have an article about trapping them, but I found that I liked
this article's suggestions a bit more.
This link is pretty informative about the issue as well, but also includes some contact info concerning information on Low Cost Spay/Neuter.
Now I am off to ponder catching the few feral cats in my neighborhood....
