h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Beavers have been reintroduced to Britain, after an absence. Their presence has been judged to be beneficial - slowing the flow of rivers, thus limiting flooding downstream, as well as encouraging other wildlife.

That's good to hear. In the US, beavers are very numerous, and often have feuds with people over whether their property should be a lake or not. They can be both good and bad for the local environment, depending on where they are.

Then, of course, there is the world's largest beaver dam, which can be seen from space. It's in Alberta, Canada. Here is the ever-excitable Rachel Maddow (a US journalist) waxing eloquent about the comparison between the beaver dam and Hoover Dam, a US man-made landmark.

http://www.youtube.com/watch?v=VluX_hbM09Y