The social metabolism of biomass in Spain, 1900–2008: From food to feed-oriented changes in the agro-ecosystems

The main aim of this article is to reconstruct the main biomass flows and indicators for the Spanish agriculture between 1900 and 2008. We reconstruct the Net Primary Productivity for Spanish agro-ecosystems, but also the main Economy-Wide/material flow accounting indicators as Domestic Extraction of biomass, Physical Balance Trade PTB) and Domestic Material Consumption (DMC) of biomass in Spain. The main results shows that the transition from agrarian to industrial metabolism has meant a decrease in the per capita consumption of biomass. However, in absolute terms, the consumption of biotic materials has also increased considerably. This has been due to the changes in the functionality of biomass for social metabolism as a whole: it has gone from being the main source of energy and materials to specializing in two essential functions, the provision of raw materials for industry and the supply of food. The Spanish case confirms that the industrialization of agriculture has led to an increase in pressure on the Spanish agro-ecosystems. But there has also been a transfer of pressure on agro-ecosystems of other countries through international trade. Spain is a net biomass importer in order to maintain a diet that is ever richer in meat and dairy products.