If you were able to target it properly to the right species, depending on where you are in the world, there’s a good chance that the rats and sparrows you’re thinking of are invasive.

I know around me in the US I see a whole lot more house sparrows (native to Europe, Asia, and some parts of North Africa) than I do any native Sparrows.

And the two most known rat species- the black and brown rats, originated in different parts of Asia and more-or-less spread around the world with human trade and migration.

So getting rid of those would probably be a good thing to reduce competition for native animals.