Beavers don't destroy whole valleys the size of Hetch Hetchy..... and all the other animals and plants. In 5-10 years man can destroy Yosemite Valley and turn it into a big lump of cement like LA, but a beaver can never do anything in that scale.
How much more money is needed to restore the vegetation etc....?
Beavers don't destroy whole valleys
You've not seen hungry beavers work have you? They do a lot of destruction.