Is the damage done by these cats extensive? I’m not seeing a reason why explained...keep in mind I’m a city slicker.
The anti-cat zealots throw out statistics like “Housecats kill billions of birds every year.” But they never have any hard data to back that up.
Cats eat a variety of small critters—rodents, birds, reptiles, insects, etc. And they can be excellent hunters. Without cats, we would be overrun by rodents. This endangers both our food supply and our health.
People who study the domestication of cats say that the relationship between cats and humans began in the dawn of agriculture. The early farmers grew crops that attracted rodents and other pests; the rodents and other pests attracted cats. The farmers tolerated and even welcomed the cats because the cats saved the food supply. The utility of cats is responsible for their spread worldwide. Plus, cats are cute—they have characteristics of human infants—which also contributed to their domestication.
To actually answer your question in depth, see this link:
https://en.wikipedia.org/wiki/Sodium_fluoroacetate
Scroll down to Australia and New Zealand.