You can have a direct, positive effect on unowned, unloved, unwanted feral cats by humanely euthanizing them to save them from a short, brutal life on the streets, dying without veterinary care from disease, trauma, failed TNR sutures, or various forms of human cruelty. OR to save them from a lifetime on a small cell at a "no-kill" shelter where they have as much space as a calf being raised for veal. At the same time, you will be saving humans and wildlife from rabies and toxoplasmosis. Google "Centers for Disease Control" with "Burden of Rabies" and with "toxoplasmosis biology" if you doubt me. Cats are an introduced predator who belong inside loving homes, like ferrets.