We all know how highly invasive cat pictures have been on the internet but that's not the only place that cats invade.
As much as many of us love cats their is an inconvenient truth about them. In many areas of the word feral and outdoor cats pose a very significant alien invasive species threat.
On Islands and in other sensitive ecosystems 14% of modern species extinctions have been attributed to the introduction of domestic cats
Being a reptile enthusiast myself I have always noted how quickly domestic cats can decimate the local lizard populations... and that is just what is easily visible.
One of the challenges I see at work is people with good intentions feeding feral cats that live in the sewers.
If only they knew they were actually perpetuating and actually increasing the problem...
Nobody likes to see a sick wild cat or starving little kittens but intervening in feral populations just allows them to increase in size and create an even larger problem for the local wildlife and ecology.
If you want to understand more about the problems they pose on islands check out:
For more background and practical advice check out...
http://www.huffingtonpost.com/charles-knapp-phd/cats-as-invasive-species-_b_9320262.html