From input–output analysis to the quantification of metabolic patterns: David Pimentel’s contribution to the analysis of complex environmental problems

This paper revisits David Pimentel’s work on input–output analysis of agricultural production systems with the objective of demonstrating its (continued) relevance for the analysis of complex environmental issues. It is shown that his unique accounting procedure is grounded in complexity theory and that it effectively links expected relations over primary inputs and outputs exchanged with the ecosphere and secondary inputs and outputs exchanged with the anthroposphere (including labor). New conceptual building blocks are introduced to demonstrate that Pimentel’s analysis can be extended across different hierarchical levels (crop typologies, commodity supply systems, agricultural regions, etc.) and dimensions of analysis to obtain a formal representation of the metabolic pattern of social–ecological systems. These concepts include: (i) state–pressure relation (extensive properties); (ii) flow–fund ratios (intensive properties), i.e., qualitative benchmarks to define typologies of agricultural production in relation to both the socioeconomic process (e.g., land productivity, labor productivity) and the environmental pressure exerted on the environment (e.g., water consumption, GHG emission and pesticide load per hectare); and (iii) relational analysis to scale up the analysis to higher hierarchical levels so as to acquire policy relevance. Examples of the pertinence of this formalization are illustrated using Pimentel’s original data on grain cultivation in the USA. It is concluded that Pimentel’s work has set an example for a holistic approach to complex environmental problems and has paved the way for a more general conceptualization of social–ecological systems as metabolic systems.