Why do dams that are built to provide electricity and control floods also harm human health?
Dams can make great contributions. But like most everything that changes the balance of nature, they can also do great harm. Dams create artificial lakes that can be breeding grounds for insects and other disease-carrying animals. Schistosomiasis, for example, often spreads via snails that thrive in the stagnant or slow-moving water that is trapped by dams. Large dams can also force huge numbers of people to move. Construction of the Three Gorges dam, now under construction along the Yangtze River in China, for example, has caused about two million people to uproot and move their homes.
