This study suggests that the amount of land resources necessary to replace our non-renewable energy sources outstrips the supply of available land. As such, since we are allowing markets to determine what gets provided (corn as ethanol, rather than food, for instance), we will probably see the counterproductive and counterintuitive practice of converting land that currently provides habitat to energy production (what else is new?) This, to me, is somewhat shortsighted thinking, but also makes an important point: that we cannot ignore conservation as a central element in the fight to mitigate climate change.
However, I am quite hopeful for prospects such as solar roofs and small wind turbines in the effort to create localized energy sources. And there's always my favorite source of energy-- the human body. Maybe we should put handcranks on everything.