I became fascinated with the connection between our food supply and energy when I first learned of the problems that North Korea was having feeding itself. (see here).  This data showed me something amazing about modern society, we don't live in the information age, we don't live in the industrial age, we live in the agricultural  age. Without food, we have no industry or information. Unfortunately many don't understand this.  Nor do they understand that today the modern farming system is merely a means to turn petroleum into food, via mechanized planting and harvesting, and the use of petroleum based insecticides and fertilizers which consume huge amounts of energy in their manufacture.  According to Wikipedia, who gets it from Science, 1% of the world's energy goes into the manufacture of chemical fertilizer (here).

There has recently been a claim that in the post-peak oil world, life will go on pretty much as normal.  For a while, as the world squeezes inefficiencies out of the economic system and fuel switching occurs, this is true.  But one can not seriously believe that the world economy is infinitely elastic with regards to energy.  With regard to the agricultural system, there is data which shows the limits to this inelasticity and these limits are due to the laws of physics.