In 2007, China was designated as the most dammed nation in the world. The United States is second, followed by India, Japan, 
Spain and Canada. In 140 countries, 47,665 large dams exist. Scientists believe that the weight of their water alters the speed 
of the Earth's rotation.  A few years ago, Outside Magazine reported that one-fifth of the world's electricity is generated from 
hydroelectric dams, providing beneficial irrigation for one-sixth of the world's food supply.  During the construction of hydro-
electric dams, 80 million people have been displaced. Experts also believe that dams inhibit fish migration and alter water flow  
in addition to adjusting temperatures. In recent years more than 212 dams have been torn down.   Another dam builder is the 
beaver. Their dams, canals and lodges protect them from predators, provide a food source and building materials. When startled, 
beavers initiate an alarm on their quiet pools by energetically smacking the water with their broad tail; forwarding a danger 
message to others. Stockpiled sticks provide a winter food source and a means of insulation. Snow pack prevents water from 
freezing around their homes. Often, the removal of existing beaver dams causes flash flooding of residential areas. In the 
protection of their habitat, conservation groups note that the beaver also assists humans by preventing residential flooding 
and roadway wash outs.