(N. American: Castor canadensis) (Eurasian: Castor fiber)
Beavers are more than intriguing animals with flat tails and lustrous fur. American Indians called the beaver the "sacred center" of the land because this species creates such rich, watery habitat for other mammals, fish, turtles, frogs, birds and ducks. We now know that beaver damming provides essential natural services for people too.
Beavers prefer to dam streams in shallow valleys, where the flooded area becomes productive wetlands.These cradles of life support biodiversity that rivals tropical rain forests. Almost half of endangered and threatened species in North America rely upon wetlands. Freshwater wetlands have been rated as the world's most valuable land-based ecosystem.
Beavers reliably and economically maintain wetlands that sponge up floodwaters, alleviate droughts and floods (because their dams keep water on the land longer), lesson erosion, raise the water table and act as the "earth's kidneys" to purify water. The latter occurs because several feet of silt collect upstream of older beaver dams, and toxics, such as pesticides, are broken down by microbes in the wetlands that beavers create. Thus, water downstream of dams is cleaner and requires less treatment for human use. ... http://www.beaversww.org