The article did not mention rising ocean levels. According to New Scientist, some hydroelectric dams have been found to release more greenhouse gasses into the atmosphere than their coal-fired counterparts. The source of the emissions was the mass of rotting vegetation that accumulated in the reservoir. Hydroelectric reservoirs cover an area of the world the size of France. They release carbon dioxide and methane.
Stagnant water produces the worst emissions because the decaying vegetation generates methane.
This is 20 times as potent a greenhouse gas as CO2, which is produced when there is oxygen in the water. So a reservoir will produce more methane than the river did before the dam was built. Dams can also be lethal to salmon . Standing water in reservoirs facilitate unnaturally high water temperatures, and spillways raise the levels of nitrogen gas, both of which increase mortality in salmon runs. In this site's discussion group, Ola Mork says that looking at the sites posted earlier by Yuill, he could not find much in the way of primary sources for research on climate change.