Cats have a pretty negative effect on a lot of small wildlife because they are such proficient hunters: https://www.usatoday.com/story/news/nation/2013/01/29/ca

Cats have a pretty negative effect on a lot of small wildlife because they are such proficient hunters: https://www.usatoday.com/story/news/nation/2013/01/29/cats-wild-birds-mammals-study/1873871/ https://www.usatoday.com/story/news/nation/2013/01/29/cats-w... I don't know which human activities have the most detrimental effects on wildlife populations, but this is a good one to focus on.