There is research showing that cats living outside kill birds and small mammals. There are some bird researchers who firmly believe cats have led to species extinctions and post a great danger to some of their prey species.
We believe that indoor cats have longer lifespans than outdoor cats, due to the reduced risk of accidental injury, predators, parasites and infections. There is no good research on this. We don’t have a study that tells us how long the average cat lives, never mind giving us a way to balance different lifestyles against risks.
Nor do we have firm data on the amount of environmental risk from indoor-outdoor owned cats versus feral or colony cats, although the assumption is that feral or colony cats are responsible for more environmental damage.
How about you? Do you keep your cat indoors? How much time does she spend outdoors? Are you aware of the concerns about wildlife health (and cat health) when cats are outside?