There has been a spate of dam demolitions, such as this one on Oregon's Sandy River, in recent years. Many of them provided hydroelectric power generation.
Now, I'm happy for the fish, but I'm just wondering where and how this electrical generation capacity will be made up? I don't think oil- or gas-fired plants are going to be the answer (with Peak Oil and all), and it'd be too rich if the dams were demolished for the good of the fish and replaced by nukes (although I'd love it).
Do you suppose the greenies are actually going to start turning off their lights?