Earlier quoted context omitted.
They'll also abandon perfectly good dams just to move up stream and build another. They're some of the most environmentally destructive critters on earth; like most creatures if allowed to thrive they'll just keep devouring every tree and damming every river until they starve and die off, only beavers can wind up taking whole ecosystems with them.
Depends on your point of view. North America used to be a festering swamp of mosquito-ridden beaver ponds. Built over millions of years. That WAS the ecology. The landscape we see today is unnatural and temporary. We reformed this continent to suit ourselves. Most attempts to protect some bit of land and trees in the name of preservation is ... shortsighted at the least.
We humans just happen to be the ones on top right now doing the unbalanced expansion thing.