I think it's probably to protect them from the deer that roam free in the park.
Perhaps the like to eat the younger trees, or hit them with their antlers, I don't know.
Monochrome, somehow, the beaver story just doesnt make sense. Wooden fences to keep out beavers?
It didn't make since to me either but one of the local city parks did this last year and it saved the trees. There was talk about using treated wood vs metal, but it looks prettier and worked.
