For much of the 20th century humans got really good at dam building. Dams — embraced for their flood protection, water storage and electricity generation — drove industry, built cities and helped turn deserts into farms. The United States alone has now amassed more than 90,000 dams, half of which are 25 feet tall or greater.
Decades ago, dams were a sure sign of “progress.” But that’s changing.
Today the American public is more discerning of dams’ benefits and more aware of their long-term consequences. In the past 30 years, 1,275 dams have been torn down, according to the nonprofit American Rivers, which works on dam-removal and river-restoration projects.
Why remove dams? Some are simply old and unsafe – the average age of U.S. dams is 56 years. It would cost American taxpayers almost $45 billion to repair our aging, high-hazard dams, according to the American Society of Civil Engineers. In some cases it’s simply cheaper to remove them.
Other dams have simply outlived their usefulness or been judged to be doing more harm than good. Dams have been shown to fragment habitat, decimate fisheries and alter ecosystems.