Well looky there..."green" energy sources require 5 to 100 times the amount of land that fossil sources such as coal require. Not saying that we shouldn't pursue these options, but they're certainly not a silver bullet:
http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0006802 See Figure 3 in particular.
Source: Nature Conservancy