Energy intensities in ecological and economic systems

The concept of energy intensity (the energy needed, directly and indirectly, to effect the production of a “modity” an be applied to both economic and ecological systems. Hannon (1979) and Constanza (1980) have remarked on the lack of variation of energy intensity between different commodities for an ecosystem and an economic system, respectively. T This is particularly surprising for the ecosystem, since it seems to violate the traditional pyramid view of trophic systems. I show rigorously that Hannon's result is a mathematical consequence of his assumptions which are physically unjustified. I present a similar intuitive argument for Costanza's result, which is based on controversial but not physically unacceptable assumptions. The discussion brings out common threads of input-output economics and ecosystem analysis.