For years there has been ongoing debate on what the veterinary medical community should recommend to owners in regard to indoor vs. free roaming pet cats. It's been shown that free ranging cats have shorter lifespans, and are more prone to accidents, predators, parasites and infectious diseases. In addition, evidence now shows that outdoor cats 
have already made a significant negative impact on native wildlife populations, in particular wild birds, some of whose numbers are declining and may be threatened eventually. Every year concerned citizens come to our door with injured birds and mammals their cats have caught outdoors, or even brought inside as "presents". Most of these do not survive.
For this reason, AEAC supports the American Veterinary Medical Association (AVMA) position on out door cats which is available here: https://www.avma.org/KB/Policies/Pages/Free-Roaming-Owned-Cats.aspx
For many years, the Association of Avian Veterinarians has recommended keeping cats indoors, primarily due to the impact on native birds. The position statement can be found here: : http://www.aav.org/default.asp?page=feralcats