A Net Energy Analysis of the Global Agriculture, Aquaculture, Fishing and Forestry System
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ORIGINAL PAPER
A Net Energy Analysis of the Global Agriculture, Aquaculture, Fishing and Forestry System Zeke Marshall1 · Paul E. Brockway1 Received: 31 January 2020 / Revised: 15 May 2020 / Accepted: 20 May 2020 / Published online: 5 June 2020 © The Author(s) 2020, corrected publication 2020
Abstract The global agriculture, aquaculture, fishing and forestry (AAFF) energy system is subject to three unsustainable trends: (1) the approaching biophysical limits of AAFF; (2) the role of AAFF as a driver of environmental degradation; and (3) the long-term declining energy efficiency of AAFF due to growing dependence on fossil fuels. In response, we conduct a net energy analysis for the period 1971–2017 and review existing studies to investigate the global AAFF energy system and its vulnerability to the three unsustainable trends from an energetic perspective. We estimate the global AAFF system represents 27.9% of societies energy supply in 2017, with food energy representing 20.8% of societies total energy supply. We find that the net energy-return-on-investment (net EROI) of global AAFF increased from 2.87:1 in 1971 to 4.05:1 in 2017. We suggest that rising net EROI values are being fuelled in part by ‘depleting natures accumulated energy stocks’. We also find that the net energy balance of AAFF increased by 130% in this period, with at the same time a decrease in both the proportion of rural residents and also the proportion of the total population working in AAFF—which decreased from 19.8 to 10.3%. However, this comes at the cost of growing fossil fuel dependency which increased from 43.6 to 62.2%. Given the increasing probability of near-term fossil fuel scarcity, the growing impacts of climate change and environmental degradation, and the approaching biophysical limits of global AAFF, ‘Odum’s hoax’ is likely soon to be revealed. Keywords EROI · Net energy · Agriculture · Agroecosystem · Social metabolism · Bioenergy
Introduction Unsustainable Trends in Global Agriculture, Aquaculture, Fishing and Forestry All organisms must gather sufficient energy from their environment to survive, with sufficiency determined by an organisms basic metabolic requirements for maintenance, growth and reproduction (Brown et al. 2004), along with the energy required to gather energy from its environment (Court 2019). Additionally, to support any organisms in a community not engaged in energy-gathering, a surplus of energy must be gathered. The proportion of energy available as surplus is a key determinant of the viability and complexity of that * Zeke Marshall [email protected] Paul E. Brockway [email protected] 1
The School of Earth and Environment, The University of Leeds, Leeds, West Yorkshire LS2 9JT, UK
community structure (Chaisson 2011; Tainter 2011). Underpinning these relationships are the laws of thermodynamics. Namely that “A living organism represents an open thermodynamic system that continuously exchanges compounds and heat with the environment, performs mechanical work, and disposes of internal en
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