Not the easiest one, I have to admit. Only two things immediately occur:
- that they are a good means of seed and nut dispersal, and therefore help the spread of trees and other plants
- that, because they are so widespread, and so cute and lively, they are often a good early introduction for children to an interest in wildlife
Not much of a clinching argument
What other animals are you up against?
I'd like to exterminate the mosquito.