Energy Efficiency in Agrarian Systems From an Agroecological Perspective

Abstract

Energy analyses applied to agriculture should express something more than the “energy cost” of the net biomass produced for the benefit of society. They should also provide information about structural and functional changes in the agroecosystem which might affect the maintenance of the ecosystem services which the agroecosystem provides. With this aim, a methodological proposal has been developed to add agroecological EROIs (energy return on the investment) to the existing economic EROIs. This proposal has been applied to an agroecosystem which is representative of Mediterranean agro-climatic conditions at three key moments: one of balanced organic agriculture (1752), at the beginning of the use of chemical inputs (1904), and a time of agricultural production decoupled from its territory (1997). The results demonstrate the usefulness of the combination of both types of EROI in the detection of processes (agriculturalization vs. livestock farming, reforestation, generation of spatial heterogeneity, or the maintenance of biodiversity), which affect the “fund” elements of agroecosystems and their capacity to generate “flows” of ecosystem services.

Keywords:

• ecosystem services
• EROI (energy return on the investment)
• land sharing
• land sparing
• NPP appropriation
• social metabolism

Nomenclature

• SVB = socialized vegetal biomass (a)

• SAB = socialized animal biomass (b)

• SB = socialized biomass (a+b)

• RuB = reused biomass (c)

• UhB = unharvested biomass (d)

• AUhB = aboveground unharvested biomass

• BUhB = belowground unharvested biomass

• RcB = recycling biomass (c+d)

• AB = accumulated biomass (e)

• EI = external input (f)

• TIC = total inputs consumed (c+d+f)

• Final EROI = SB/(RuB + EI)

• External final EROI = SB/EI

• Internal final EROI = SB/RuB

• NPPact EROI = NPPact/TIC

• Agroecological final EROI = SB/TIC

• NPPact EROI minus Agroecological Final EROI =

Notes

1. See Ayres and Simonis (1994) Fischer-Kowalski (1998, 2003); Fischer-Kowalski and Hüttler (1998); Giampietro, Mayumi, and Sorman (2012); González De Molina and Toledo (2011); and González De Molina and Toledo (2014) on the concept of social metabolism and its application to agriculture

Additional information

Funding

This work springs from the international research project on Sustainable Farm Systems: Long-Term Socio-Ecological Metabolism in Western Agriculture funded by the Social Sciences and Humanities Research Council of Canada and Spanish research project HAR2012-38920-C02-01 funded by Ministerio de Economía y Competitividad (Spain).