Energy in Agroecosystems

A Tool for Assessing Sustainability

Casado, Manuel Gonzalez de Molina

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781315349909
• Edition: 1
• Topic: Ciencias biológicas
• Subtopic: Ecología

Energy in Agroecosystems: A Tool for Assessing Sustainabilit y is the first book on energy analysis that is up-to-date and specifically dedicated to agriculture. It is written from an agroecological perspective and goes beyond the conventional analysis of the efficient use of energy. The book provide a methodological guide to assess energy efficiency and sustainability from an eco-energetic point of view.

Case studies from both Europe and America, which are representative of today's most used scales of analysis (crop, farm, local or national) and the different farm management practices (traditional, industrialized, and contemporary organic), apply this methodology This book will be of primary interest to researchers, practitioners, and students working in the areas of agroecology, sustainable agriculture, environmental science, energy analysis, natural resources management, rural development and international development.

PART I

Concept and Methods

GLORIA I. GUZMÁN
MANUEL GONZÁLEZ DE MOLINA

CHAPTER 1

The Energetic Metabolism of Human Societies

CONTENTS

1.1 Introduction

1.2 A Thermodynamic Approach to Human Societies

1.3 The Social Metabolism of Societies

1.4 The Energetic Metabolism of Agriculture: A First Attempt

1.5 Fund Elements of Agrarian Metabolism

1.6 Socioecological Transitions in Agriculture

1.1 INTRODUCTION

Drawing an analogy with the biological concept of metabolism, different scientific disciplines have developed the concept of social metabolism, which aims to structure relationships between society and nature. All human beings draw from nature sufficient quantities of oxygen, water, and biomass per time unit to survive as an organism, and they excrete heat, water, carbon dioxide, and mineralized and organic substances back into nature. Similarly, individuals connected through social relations organize themselves to guarantee their subsistence and reproduction, also drawing energy from nature through meta-individual structures or artifacts, and excreting all manner of waste (González de Molina and Toledo, 2014). Hence, social metabolism alludes to the exchange of energy, materials, and information that every society engages in with its physical environment to produce and reproduce its material conditions of existence.

The idea of using the concept of metabolism in a socioecological approach to social reality has gained ground over the past decade, owing to its growing importance as a theoretical and methodological tool. This concept has been used recurrently since the nineteenth century, but remained in a latent state until the late 1960s, when a handful of economists “reinvented” it (Ayres and Simonis, 1994). In recent years, the number of studies using this concept has increased substantially, applying it principally as a tool to evaluate sustainability by studying flows of energy and materials between societies and their environments in the past and present day. Today, there are methodological proposals available that offer methods, indices, and sources of statistical information (Giampietro et al., 2012) to calculate in detail the flows of energy and materials on a national scale, even managing to quantify the energy and/or material metabolism of certain countries and their changes over time, providing a historical analysis, or commercial relations among countries measured in terms of physical or energy magnitudes.

However, very few studies have attempted to apply this tool to agriculture and agroecosystems. Agriculture, as a human activity intended principally to meet the food requirements of the population, is a particularly suitable activity on account of its peculiarities. Some authors have argued the need to study not only the input and output flows of energy that allow society to function, but also the circulation and destination of those flows within it. This need is even more evident in the case of agriculture, since agroecosystems are physical and biological entities that exhibit peculiarities that other economic activities simply do not possess. In any case, the concept of social metabolism is an ideal way of studying the use of energy within agroecosystems and of measuring its efficiency.

Furthermore, social metabolism provides agroecology with a powerful tool for analysis and a theoretical support capable of grounding the hybrid nature—among culture, communication, and the material world—of any agroecosystem, whose dynamics are explained by the interaction of rural societies with their environment. Transferring this approach to the field of agriculture implies considering the “agrarian metabolism” as the part of the social metabolism that specializes in the generation of biomass and environmental services for human consumption. This metabolic approach also allows agroecosystems to be integrated at different scales with other landscape units with which they also exchange biophysical flows, and with other social units (information flows), without which it would be impossible to explain their dynamics and organization. In this book, however, we will focus purely on the energy aspects of this exchange.

This chapter looks at the thermodynamic foundations of the metabolic approach to explore its possible application to agriculture. It also discusses the specific place occupied by agrarian activity within the metabolic relationship between society and environment. It describes the components of this relationship, distinguishing between fund elements and the energy flows that nourish them. It pays particularly close attention to agroecosystems, as the center of the socioecological relationship. Finally, we examine the recent history of agriculture from a metabolic perspective to contextualize the major changes that have occurred in the energy functionality of biomass and its changes in efficiency.

1.2 A THERMODYNAMIC APPROACH TO HUMAN SOCIETIES

In his book, What Is Life? Schrödinger (1944 [1984]), stated that living organisms are neither exempt from nor in opposition to thermodynamic laws, but rather they retain or increase their complexity by exporting the entropy they generate. Human societies are also self-maintained (autopoietic) systems, having emergent forms of stable organization in space and time, but within a process of dynamic configuration, since adaptive complex systems are nonlinear, dynamic systems capable of learning and transforming themselves through cumulative experience. The existence, configuration, maintenance, and reproduction of societies require a continual supply of energy and materials, along with the dissipation of part of that energy. Entropy is also the key element in the functioning of societies: by exchanging information, energy, and matter with their environment, societies are also subject to the laws of thermodynamics. So, we assume that entropy is common to all natural processes, be these human or of any other nature. This grounds our understanding of the material structure, functioning, and dynamics of human societies as based on a thermodynamic understanding as biological systems, which they also are. The laws of nature operate on and affect human beings and the devices they build. So the principle of entropy applies to social practice, and therefore social systems are subject to the laws of thermodynamics, which is perhaps the most relevant physical law when it comes to explaining human evolution over time.

Although human societies share the same evolutionary precepts as physical and biological systems, they represent an innovation that differentiates them and makes their dynamic specific, adding complexity and connectivity to the whole evolutionary process. Social systems cannot be explained by a simple application of the laws of physics, even though human acts are subject to them. The reason for this is that although evolution is a unified process, human society is an evolutionary innovation emerged from the reflective (self-referring) capacity possessed by human beings, which is more developed than in any other species. The most direct consequence of this human mental feature is the capacity—not exclusive among higher-order animals, but rare—for building tools and, therefore, for using energy outside the organism, that is, the use of exosomatic energy. To build and use tools, information and knowledge need to be generated and transmitted, that is, the generation of culture is required. Culture involves a symbolic dimension containing, besides knowledge, beliefs, rules and regulations, technologies, and so on. Accordingly, evolutionary innovation encompasses human capability regarding the exosomatic use of information, energy, and materials, also giving rise to a new type of complex system: the reflexive complex system (Martínez-Alier et al., 1998, p. 282) or self-reflexive system and self-aware system (Kay et al., 1999; Ramos-Martin, 2003). This feature will be instrumental because it gives social systems a unique neopoietic capacity absent from other systems or species, and that confers an essential, creative dimension to human individual and—more so—collective actions.

In analogy to living organisms, culture is the transmission of information by nongenetic means, a metaphor that became popular in the academic world. It has been said that cultural evolution is an extension of biological information by other means (Sahlins and Service, 1960; Margalef, 1980), and a parallel has been drawn between the diffusion of genes and of culture. Culture can then be seen as an innovative manifestation of the adaptive complexity of social systems; it is the name of a new genus of complexity provided by the environment for perpetuating and reorganizing a particular kind of dissipative system: social systems (Tyrtania, 2008, p. 51). Culture is but an emergent property of human societies. Its performative or neopoietic character, and its creative nature (Maturana and Varela, 1980; Rosen, 1985, 2000; Pattee, 1995; Giampietro et al., 2006) enable the configuration of new and more complex dissipative structures at even larger scales by means of technology (Adams, 1988).

Although biological systems have a limited capacity for processing energy—mainly endosomatically—due to the availability in the environment and genetic load, human societies exhibit a less constrained dissipative capacity that is only limited by the environment. Human beings can thus dissipate energy by means of artifacts or tools, that is, through knowledge and technology, and can do it faster and with greater mobility than any other species. Societies adapt to the environment by changing their structures and frontiers by means of association, integration, or conquest of other societies, something biological organisms cannot do. In other words, different from the biological systems with well-defined boundaries, human societies can organize and reorganize, thus acquiring the capability of avoiding or overcoming local limitations from the environment. That explains why some societies maintain exosomatic consumption levels that are beyond the provision means of their local environments without entering into a steady state. What is specifically human is the exosomatic consumption of energy. Since no genetic load regulates such exosomatic consumption, it becomes codified by culture, which involves a faster but less predictable evolutionary rate.

From that perspective, the theoretical key is the consideration that human societies, according to the evolutionary innovations they represent, build structures—in the sense of Prigogine—that dissipate heat (entropy) to the environment, obtaining free energy from it. These structures are not only biological but also technological, thanks to the species’ capacity for building tools and mechanical, electronic, and digital artifacts. As we have seen, while biological metabolism is genetically determined, technological metabolism is culturally determined and, therefore, subject to purely social constraints in addition to environmental constraints. Hence, the metabolism of a society will be the sum of the biological and the technological metabolisms built by society itself over time, enabling the individual metabolisms of its members.

From a thermodynamic point of view, all human societies share with other physical and biological systems the need for controlled, efficient processing of energy extracted from the surroundings. Such is the proposal of Prigogine (1983) regarding nonequilibrium systems (thermodynamics of irreversible processes), which is one of the basic concepts of our agroecological approach to energy in agricultural systems: generation of order out of chaos. Since the natural trend of societies—as any physical and biological system—is toward a state of maximum entropy, social systems depend on building dissipative structures for balancing this trend and keeping away from maximum entropy. Dissipative structures transfer entropy to the outside environment and thus gain internal order or negentropy.

As Prigogine (1947, 1955, and 1962) said, all complex adaptive systems are kept away from thermodynamic equilibrium by means of controlled dissipation, which entails transferring part of their entropy to the environment. The structures of an open system are maintained thanks to the transfer by the system of a part of...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• Foreword
• Editors
• Contributors
• Introduction
• Part I Concept and Methods
• Part II Case Studies
• Appendix I
• Appendix II
• References
• Index