I've long been interested in food production and the processes we're using as a culture both modern and traditional. Due to the predicted global food crisis that everyone is predicting things like urban and hydroponic farming are now hot topics. To be honest I'm not sure what the answer is, but I'm confident we'll figure it out as a society.
A friend of mine emailed me an article from Defpoints, which asks where do we stand as a nation in terms of food production now and then compares the productivity to the value. Below are the diagrams from that article. They are a bit dated being from 1997, but I think they are probably still pretty accurate in theory.
[Crops - acres per square mile by county, 1997]
[Animals - per square mile by county, 1997]
[Value - dollars per square mile by county, 1997]
At first glance there seems to be a lot of white space leftover on these diagrams. So curiosity got the best of me and I went through the exercise of layering all the images in Photoshop to produce a composite image. I quickly came to the conclusion that unless we want to begin "mountain farming" I think we're using our resources fairly well. I'm sure this doesn't take into count efficiency, but it's still amazing that we're actively using most of the land available to us in this Country. The composite image I created is below.
[composite of crops and animals]