However, many are concerned that water energy may not be as eco-friendly as one would think. This is because the moving of so much water affects the natural habitats of some animals. For instance, salmon in the Columbia River are forced to swim upstream to reproduce but there are many dams in the way of where they swim to do this. There is still more research ongoing and there have already been measures put into place such as “fish ladders,” which will encourage the salmon to swim over the dams to the breeding grounds.