The situation in australia is very different from other regions, in a previous discussion on HN we've already established that for central europe, domestic cats have a negligible effect on wildlife. (As in, orders of magnitudes below the next higher causes, which are mostly wild cats and pesticides).
And i'm sure mining for coal, building ever expanding suburbs or driving cars doesn't contribute to killing any bird or mammal.. I'd need the figures but i'm convinced that human activities are far more dangerous for other animals than the activities of our pets.