I think that this paper by Kurt Cobb is one of the most brilliant and original papers I have read on Peak Oil and resource limits:

Great Graph by Kurt Cobb that shows how dependent we are on food & energy:
http://bp1.blogger.com/_-uualVqzFPk/RqzoKrjp48I/AAAAAAAAAE4/fV4VTpfl5gA/...

http://www.energybulletin.net/node/32718

Published Jul 29 2007 by Resource Insights

Upside down economics

by Kurt Cobb

This method for depicting the economy was suggested to me by two things. First, Liebig's Law of the Minimum states that an organism's growth is limited by the amount of the least available essential nutrient. In the case of world society that nutrient would be food, though many would argue that fossil fuels are the essential nutrient since so much food production depends on the use of fossil fuels and their derivatives including fertilizers and pesticides. Second, a piece by Dmitry Podborits argues that it is nonsense to say that the U. S. economy is less vulnerable to oil supply disruptions today than in 1970s because it produces twice as much GDP per barrel of oil. Instead, Podborits suggests, we are more vulnerable to oil supply disruptions because we have so much more GDP balanced on each barrel of oil. The same argument might be made with respect to agriculture which in the United States in 1930 employed 21.5 percent of the workforce and made up 7.7 percent of GDP. In 2000 the numbers were 1.9 percent of the workforce and 0.7 percent of GDP. We are balancing an ever larger total economy on an agricultural economy that on a relative basis is shrinking. Certainly, we are getting more efficient, but are we becoming more vulnerable?