Large Scale Hydro-power
Though touted as "green" energy sources by advocates, large hydroelectric dams wreak havoc on the ecosystems and communities where they are placed. Upstream and downstream, the ecology and hydrology of a river are forever changed once a concrete wall chokes back its waters. The most apparent of any large dam's impacts are the immense reservoirs that form once its gates are shut. Naturally, the higher a dam is, the more extensive the consequent flooding and environmental damage. The placement of a large physical barrier on a river cuts off fish and mammal migration routes, both above and below the dam, often with irreversible consequences. The building of dams also forces the eviction of huge numbers of people from their homes to make way for reservoirs created by dams.