I read a book, I think it was called "Beaver Pond," written by a woman who observed a beaver colony for a long time, a couple for several years. They ate the corms of a certain kind of lily.

Why don't you find out what they eat besides trees and plant that for them to eat? Why don't you get in touch with your Department of Conservation, Natural Resources, Wildlife or whatever and get some authoritative information?

If you get rid of these beavers, you will just get others eventually.