Dams are terrible for the environment(generally poison everything with methyl mercury), and in many cases aren't even that green, since they produce a lot of me

Dams are terrible for the environment(generally poison everything with methyl mercury), and in many cases aren't even that green, since they produce a lot of methane (dam water goes down in summer, that area growns plants, fills up in winter, plants then decompose in an anaerobic environment, producing methane). Depending on the size of the lakes this can be a very large area, ie: big hydro dams in Quebec/BC. There's been research to show one hydro dam produces more greenhouse gases than an equivalently sized coal plant in Brazil.