1

2

3

This is the second and final revision of an original submission that lead to the journal article 4

Socioeconomic metabolism as paradigm for studying the biophysical basis of human societies by 5

Stefan Pauliuk and Edgar G Hertwich 6

published in Ecological Economics 7

8

The published version of the article including its correct citation can be found under 9

http://www.sciencedirect.com/science/article/pii/S0921800915003481 10

Socioeconomic Metabolism as Paradigm for 11

Studying the Biophysical Basis of Human Societies 12

Abstract: 13

A wide spectrum of quantitative systems approaches such as life cycle assessment or 14

integrated assessment models are available to assess sustainable development strategies. 15

These methods describe certain aspects of the biophysical basis of society, which comprises 16

in-use stocks and the processes and flows that maintain and operate these stocks. Despite this 17

commonality, the methods are often developed and applied in isolation, which dampens 18

scientific progress and complicates communication between scientists and decision makers. 19

As research on socioecological systems matures, more structure and classification is needed. 20

We argue that the concept of socioeconomic metabolism (SEM), which was developed in 21

material flow analysis and material flow accounting, is a powerful boundary object that can 22

serve as paradigm for studying the biophysical basis of human society. A common paradigm 23

can facilitate model combination and integration, which can lead to more robust and 24

comprehensive interdisciplinary assessments of sustainable development strategies. We refine 25

the notion of SEM, clarify the relation between SEM and the economy, and provide a list of 26

features that we believe qualifies SEM as research paradigm. We argue that SEM as paradigm 27

can help to justify alternative economic concepts, suggest analogies that make the concept 28

more accessible, and discuss its limitations. 29

Keywords: socioeconomic metabolism; paradigm; socio-ecological system; boundary object; 30

industrial ecology; metaphor; 31

32

1. Introduction 33

1.1. The interdisciplinary systems approach to increase environmental literacy 34

Human interference with global bio-geochemical cycles has grown to a level where human 35

actions are likely to trigger epochal changes, like dangerous climatic change (IPCC, 2014; 36

UNFCCC, 1992) and a state shift in the Earth’s biosphere (Barnosky et al., 2012). A new age, 37

the anthropocene, was ushered in (Steffen et al., 2011), during which humans not only cause 38

but anticipate and respond to epochal changes by adapting to new environmental conditions 39

and by mitigating negative human impacts on the natural environment. Mitigation and 40

adaptation strategies include geoengineering, technology development and deployment, 41

economic instruments like taxes and subsidies, regulation and standards, and changes in 42

consumer choices and lifestyle. To design and successfully implement adaptation and 43

mitigation strategies for the coming global socio-metabolic transition (Krausmann and 44

Fischer-Kowalski, 2013; Krausmann et al., 2008), humans require ‘environmental literacy', 45

which is the "capability […] to appropriately read, utilize, and adapt to environmental 46

information, resources, and system dynamics" (Scholz and Binder, 2011). At present, human 47

environmental literacy is higher than ever before, and a wide range of scientific methods is 48

applied to further increase it. 49

50

The systems approach is the widely accepted epistemological basis of environmental literacy. 51

Under this approach, human society is considered a complex autopoietic system (Deutz and 52

Ioppolo, 2015; Forrester, 1968; Maturana and Varela, 1980; Meerow and Newell, 2015; 53

Rammel et al., 2007; von Bertalanffy, 1968), that is a complex system that can reproduce and 54

maintain its structures and so compensate for the inevitable losses due to the second law of 55

thermodynamics with the help of external energy and material input (Ayres and Kneese, 56

1969; Georgescu-Roegen, 1971). Human societies form a hybrid of the material or 57

biophysical realm and a symbolic or social realm (Fischer-Kowalski and Weisz, 1999), and 58

together with their natural environment, they are commonly described as socio-ecological 59

systems (SES) (Binder et al., 2013; Holling, 2001; Ostrom, 2009, 2007). SES contain many 60

interlinked bio-physical and social aspects (Spash, 2012), nonlinearities, and feedback 61

mechanisms, and they are non-deterministic because human agents use their environmental 62

literacy to deliberately change the development of the system. 63

64

The complexity of SES poses major challenges to the scientific approach to increasing 65

environmental literacy. First, researchers cannot reliably predict the development of complex 66

systems even if they understand the underlying mechanisms. Research can, however, shine 67

light on the role of different factors and illustrate potential outcomes. Second, and in the focus 68

of this work, complexity challenges boundaries between established scientific disciplines. 69

Inter- and trans-disciplinary collaboration of researchers from many fields can increase our 70

environmental literacy (Baumgärtner et al., 2008). This type of research requires certain 71

concepts about SES that are general enough to facilitate exchange among disciplines and 72

between science and the public (Brand and Jax, 2007) and that are clearly specified and well 73

described to be of practical use in the different fields. Concepts like ‘resilience’, ‘industrial 74

ecosystem’, or ‘metabolism’ can enrich science and facilitate interdisciplinary research as 75

metaphors (Ehrenfeld, 2004), boundary objects (Star and Griesemer, 1989), or even research 76

paradigms (Kuhn, 1996 [1962]). When properly communicated, their integrative power can 77

facilitate the development of new research questions and data exchange and avoid re-labeling 78

or ‘re-invention’ of existing concepts under new names. Common concepts can also motivate 79

people to stop thinking in silos of individual methods and frameworks and appreciate their 80

work as part of a spectrum of similar or complementary efforts to increase environmental 81

literacy. 82

1.2. Quantitative systems analysis of the biophysical basis of society 83

Quantitative approaches to study the biophysical basis of human societies are a central 84

component of the research on socioecological systems, and a variety of methods to study that 85

basis has developed as part of distinct research traditions. In our opinion, these research 86

traditions could benefit from the appreciation of common concepts in ways described above, 87

and the elaboration of a suitable overarching concept for these methods is the scope of this 88

work. 89

90

Descriptive research approaches include purely physical modeling approaches like material 91

flow accounting (MFA), (Eurostat, 2001; Fischer-Kowalski et al., 2011), substance or 92

material flow analysis (Baccini and Bader, 1996; Baccini and Brunner, 2012 [1991]), or 93

physical supply and use tables (SUT), (Miller and Blair, 2009; Pauliuk et al., 2015b; Suh et 94

al., 2010). Attributional or footprint-type methods include life cycle assessment (LCA), 95

(Heijungs and Suh, 2002; ISO, 2006) and environmentally extended input/output analysis 96

(EE-IO), especially multi-regional input/output analysis, (Miller and Blair, 2009; Wiedmann 97

et al., 2011). Prospective methods include the econometric, partial equilibrium, or system 98

dynamics models of the energy system that come as standalone models (Cambridge 99

Econometrics, 2014; Jebaraj and Iniyan, 2006; Pfenninger et al., 2014) or that are part of 100

integrated assessment models (de Vries et al., 2001; Loulou et al., 2005; Richardson, 2013), 101

computable general equilibrium models (CGE), (Burfisher, 2011), system dynamics 102

approaches (Buongiorno, 1996; Pruyt, 2010; Sterman, 1994), and agent-based models (Axtell 103

and Andrews, 2002; Sopha et al., 2011). 104

105

The different methods partly depend on each other. CGE models, for example, are built from 106

Leontief IO models, which in turn are derived from SUTs. Moreover, many ‘hybrid models’ 107

that combine features of different methods exist. Those include hybrid LCA, mixed-unit I/O, 108

waste-I/O, combinations of LCA and CGE, extended dynamic MFA, scenario-based hybrid 109

I/O, and consequential LCA (Dandres et al., 2012; Earles and Halog, 2011; Finnveden et al., 110

2009; Hawkins et al., 2007; Heijungs and Suh, 2002; Hertwich et al., 2015; Modaresi et al., 111

2014; Nakamura and Kondo, 2002; Nakamura et al., 2008; Suh et al., 2004). 112

113

The methods differ regarding the choice of system boundary, process resolution, the layer of 114

analysis (physical or monetary), regional coverage, exogenous drivers, and the way they 115

model the interaction between human society and nature. Despite these differences, the 116

methods have one central commonality. They all describe certain aspects of the biophysical 117

structures of society (Haberl et al., 2004), which includes human-controlled in-use stocks such 118

as infrastructure, buildings, vehicles, machines and other fixed capital, consumer products, 119

but also our own bodies, and of socioeconomic metabolism, which describes the industrial 120

processes, market activities, commodity flows, and exchanges with nature to build, maintain, 121

and operate the in-use stocks (Fischer-Kowalski and Haberl, 1998). 122

123

1.3 Socioeconomic metabolism as concept: Metaphor, boundary object, or paradigm? 124

In a recent paper, Newell and Cousins (2014) ask the community to ‘reinvigorate the urban 125

metabolism metaphor’ to overcome academic isolation between different fields including 126

industrial ecology, Marxist ecologies, and urban ecology. We strongly agree with them 127

regarding the unifying role of the metabolism concept in the study of socioecological systems 128

from different angles. In a first step towards greater unification, socioeconomic metabolism 129

(henceforth SEM) could be seen as boundary object of different methods that study the 130

biophysical basis of society in different disciplines. A boundary object “is an analytic concept 131

of those scientific objects which both inhabit several intersecting social worlds [including 132

different scientific fields, S.P.] and satisfy the informational requirements of each of them” 133

(Star and Griesemer, 1989). To accommodate the ontological differences across different 134

fields and to create some common identity across fields the general notion of a boundary 135

object needs to be rather vague (Hertz and Schlüter, 2015). The currently prevailing 136

metaphorical use of the concept SEM probably meets this criterion. 137

138

We believe, however, that it is necessary to move beyond metaphorical use of the term 139

‘metabolism’, because socioeconomic metabolism is more and more often used without 140

explicit reference to biological systems, and because the application of the metabolism 141

concept as boundary object for socio-ecological systems requires a new scoping and 142

redefinition of the term to facilitate analytical rigor in the fields that study SES (Fischer-143

Kowalski, 1998; Hertz and Schlüter, 2015). 144

145

The study of the socioeconomic metabolism as part of the biophysical basis of SES is subject 146

to natural scientific principles, and hence, it follows an explicit or implicit paradigm. In the 147

third edition of The Structure of Scientific Revolutions, Kuhn (1996 [1962]) defines a 148

scientific paradigm as a group of "universally recognized scientific achievements that, for a 149

time, provide model problems and solutions for a community of practitioners”. A paradigm 150

facilitates scientific progress, and ultimately, it helps to increase the relevance of science for 151

society (Kuhn, 1996 [1962]). Does SEM qualify as ‘universally recognized scientific 152

achievement’, and hence as paradigm? That would have implications that go far beyond the 153

use of SEM as metaphor or boundary object. 154

155

156

157

1.4 Research gap, goal and scope of the paper 158

Socioeconomic metabolism (SEM) has already been described as paradigm (ConAccount, 159

1998; Fischer-Kowalski and Hüttler, 1999; Fischer-Kowalski and Weisz, 1999; Fischer-160

Kowalski, 1998), but the foundations and implications of this assertion were not clearly 161

stated. Moreover, the consequences of this assertion for the systematization of the different 162

methods were not investigated. 163

This paper tries to fill that gap; it aims to complement the work on the historic development of 164

SEM (Fischer-Kowalski and Hüttler, 1999; Fischer-Kowalski, 1998) by putting the concept 165

into a broader context. We argue that the concept of socioeconomic metabolism, which was 166

developed in material flow analysis and material flow accounting, 167

(i) is powerful and can be applied more broadly to a number of efforts that have not yet fully 168

recognized that they do research on the same subject and that could benefit from more 169

interaction. 170

(ii) can serve as paradigm for the study of the biophysical basis of human society, which has 171

further implications that have not been fully recognized yet. 172

173

In section 2 we further elaborate the notion of SEM and examine what might qualify SEM as 174

paradigm for the study of the biophysical basis of human society. We also explore the 175

relationship between SEM, the economy, and society in more detail. 176

In section 3, we show the benefits of using SEM as paradigm: We demonstrate that using 177

SEM as paradigm can help to identify commonalities between different conceptual 178

frameworks and modeling approaches, describe several direct applications of SEM, and 179

discuss the limitations of the concept. 180

181

182

2. Socioeconomic metabolism (SEM) as paradigm 183

2.1. What is socioeconomic metabolism? 184

To describe the autopoietic and complex character of society’s biophysical basis, the concept 185

‘metabolism’, which refers to “the totality of the chemical reactions and physical changes that 186

occur in living organisms” (Cammack et al., 2008) was adopted from biology by researchers 187

that were developing frameworks and methods for material and energy flow accounting 188

(Ayres and Simonis, 1994; Baccini and Brunner, 2012 [1991]; Fischer-Kowalski, 1998; 189

Wolman, 1965). The extended notion of metabolism was termed socioeconomic metabolism. 190

It is often used in different combinations and connotations, including ‘industrial metabolism’ 191

(Ayres and Simonis, 1994), ‘metabolism of the anthroposphere’ (Baccini and Brunner, 1991), 192

‘anthropogenic metabolism’ (Brunner and Rechberger, 2002), ‘social’, ‘societal’, ‘society’s’, 193

or ‘socio-economic metabolism’ (Fischer-Kowalski and Hüttler, 1999; Fischer-Kowalski and 194

Weisz, 1999; Pauliuk and Müller, 2014), and urban metabolism or metabolism of cities 195

(Kennedy et al., 2007; Newell and Cousins, 2014; Wolman, 1965). 196

The concept of SEM has found widespread appraisal, and the International Society for 197

Industrial Ecology now has a topical section entitled ‘Socio-Economic Metabolism’. It 198

inspired the development of economy-wide accounts of energy and material turnover 199

(Eurostat, 2001; Haberl, 2001; Haberl et al., 2004). Compilation of aggregated material flow 200

indicators is now part of the data collection routines at EuroStat (Eurostat, 2001), the OECD 201

(OECD, 2003), and the system of environmental-economic accounting (UN, 2012). The term 202

metabolism, however, implies broader application than mere accounting of material and 203

energy flows. It defines a research subject and perspective for a wider research field. 204

205

The notion of SEM has evolved over time and the scope of the term differs among scholars. 206

While sharing a common view on the complexity of the system studied, these definitions 207

differ in scope and level of aggregation. Some definitions of SEM refer to an aggregate 208

account of flows or processes within the anthroposphere, and the notion of society as complex 209

autopoietic system remains implicit. Examples include Fischer-Kowalski and Amann (2001): 210

“Socio-economic metabolism refers to the sum total of the material and energetic flows into, 211

within, and out of a socio-economic system.”, and Kennedy et al. (2007): “urban metabolism 212

might be defined as the sum total of the technical and socioeconomic processes that occur in 213

cities, resulting in growth, production of energy, and elimination of waste.” Alternatively, 214

Fischer-Kowalski and Haberl (1998) define SEM more widely as “the material input, 215

processing and releases of society and the corresponding energy turnover” and as ‘material 216

and energetic process within the economy and society’ (Fischer-Kowalski, 1998), thus going 217

beyond the sum total of energy and material throughput. Other authors proposed even more 218

comprehensive definitions by explicitly including stocks. Baccini and Brunner (2012 [1991]) 219

define the metabolism of the anthroposphere as ‘all physical flows and stocks of energy and 220

matter within and between the entities of […] the space in which biological and cultural 221

activities of human beings take place’. Pauliuk and Müller (2014) describe SEM as ‘the set of 222

all anthropogenic flows, stocks, and transformations of physical resources and their respective 223

dynamics assembled in a systems context.’. 224

While the rough meaning of socioeconomic metabolism is intuitively clear to many, a precise 225

delineation is necessary to bring this concept to the next level. In the following points we try 226

to clarify what objects and events are part of SEM, how its boundary can be defined, and on 227

what level of aggregation the analysis should take place. 228

1) Metabolism is commonly associated with chemical reactions and other physical 229

changes within living organisms (Cammack et al., 2008), and we argue that in a 230

generalized notion, the metabolism of a certain domain of a socioecological system 231

should comprise all events that involve the transformation and distribution of 232

biophysical objects inside that domain. Events in SES can be modelled as processes or 233

flows (Pauliuk et al., 2015a), and they are described in terms of the biophysical objects 234

which partake in them. Stocks of objects should not be seen as part of SEM, because 235

the static nature of stocks conflicts with the dynamic notion of metabolism. Moreover, 236

stocks are already described by a complementary concept as biophysical structures of 237

society (Haberl et al., 2004). 238

2) The systems approach implies the existence of a boundary that divides all biophysical 239

events into those that are part of SEM and those that are not. The general theory does 240

not specify, however, where exactly this boundary is. In practice, this specification 241

follows from conventions established by researchers that agreed to use a common 242

accounting framework. Examples for boundary choices can be found in all major 243

accounting frameworks (European Commission, 2008; Eurostat, 2001; UN, 2012). In 244

more abstract terms, Pauliuk et al. (2015a) propose to use thresholds of extrinsic 245

properties to classify objects and events into categories that are defined according to 246

the relations between the objects and human agents. An example is the use of 247

economic value to divide process output into useful output and waste. In the case of 248

SEM, we propose to use the level of control by human agents as the defining extrinsic 249

property to draw the line between SEM and the natural environment (Figure 1a). This 250

control threshold for events represents the boundary between events that experience 251

sufficiently high levels of control by human agents and are hence part of SEM, and 252

those that do not and are hence part of the natural environment. 253

3) In our opinion, the general notion of SEM should not prescribe a specific level of 254

aggregation or unit of measurement to make the concept suitable for a wide spectrum 255

of research questions and approaches. Higher levels of aggregation (like the sum total) 256

can always be obtained from more detailed studies. 257

We reflect the specifications made above in a more precise definition of SEM that we 258

propose: 259

Socioeconomic metabolism constitutes the self-reproduction and evolution of the biophysical 260

structures of human society. It comprises those biophysical transformation processes, 261

distribution processes, and flows, which are controlled by humans for their purposes. The 262

biophysical structures of society (‘in use stocks’) and socioeconomic metabolism together 263

form the biophysical basis of society. 264

The biophysical structures and socioeconomic metabolism of SES are complementary 265

concepts. The former describes the biophysical objects in SES in a systems context and the 266

latter describes the events in which these objects are involved. Both concepts are intimately 267

intertwined. Events require objects for their description, and one cannot comprehensively 268

describe SEM without including stocks such productive capital or in-use stocks. On the other 269

hand, a description of stocks without events would be static and of very limited use to SES 270

research. 271

2.2. Putting SEM into context 272

The biophysical basis of society, comprising SEM and the biophysical structures of society, is 273

closely related to other concepts and categories of analysis. Clarifying these relationships 274

helps us to understand the importance and usefulness of the metabolism concept in the debate 275

about mitigation and adaptation to global environmental change. In the following three 276

subsections, we discuss the relation between the biophysical basis of society and the 277

biophysical and social spheres of causation (Fischer-Kowalski and Weisz, 1999; Haberl et al., 278

2004; Sieferle, 1997; Spash, 2012), the relation between this basis and the geo-biosphere, and 279

its relationship with the concept ‘economy’. In Appendix A we discuss the relation between 280

the biophysical basis of society and the anthroposphere. 281

2.2.1. Socioeconomic metabolism and the biophysical and social realities 282

The events that constitute SEM are part of two distinct, but interconnected spheres, which are 283

termed biophysical and social realities (Spash, 2012), or natural/biophysical and social 284

spheres of causation (Fischer-Kowalski and Weisz, 1999; Haberl et al., 2004; Sieferle, 1997). 285

286

Figure 1: The relation between the natural environment, the biophysical structures of society, 287

socioeconomic metabolism, and the social sphere of causation. a) The biophysical basis of society, 288

comprising socioeconomic metabolism and society’s biophysical structures, as subset of the 289

biophysical reality, described as the set of object and events that experiences a sufficiently high level 290

of control by human agents. The ‘environment’ is defined relationally as the set of all objects and 291

events that are not part of this basis. b) Socioeconomic metabolism is fully encompassed by the social 292

reality. The latter expands beyond SEM as it reaches into the natural environment and also comprises 293

non-physical objects of relevance to society. Fig. 1b is a modified version of the original versions 294

given by Sieferle (1997), Fischer-Kowalski and Weisz (1999), and Haberl et al. (2004). 295

All events in SEM are of biophysical nature, and hence part of the biophysical reality. They 296

are also part of the social reality, because humans need to recognize these objects and events 297

before they can control them for their purposes (Figure 1b). 298

2.2.2. Socio-economic metabolism and the geo-biosphere 299

Socioeconomic metabolism is part of the biophysical process of the geo-biosphere, and we 300

can re-draw Fig. 1a to illustrate this relationship (Fig 2a). 301

302

Figure 2: a) Illustrative scheme of SEM as part of the biophysical process of the geo-biosphere. The 303

image of the Earth illustrates the limited size of the geo-biosphere. Colonization describes “the 304

intended and sustained transformation of natural processes, by means of organized social 305

interventions, for the purpose of improving their utility for society” (Fischer-Kowalski and Weisz, 306

1999). b) The system in Fig. 2a, embedded in the wider scheme of the biophysical and social spheres 307

of causation. 308

The process of expanding the biophysical basis of society at the expense of the natural 309

environment is described as colonization of the Earth’s ecosystem (Sieferle, 1997; Sieferle et 310

al., 2006). Colonization “refers to the intended and sustained transformation of natural 311

processes, by means of organized social interventions, for the purpose of improving their 312

utility for society” (Fischer-Kowalski and Weisz, 1999). While colonization expands the 313

‘human niche’, the level of control describes to what degree the colonized processes and 314

flows of the bio-geosphere are actually part of SEM. The distinction between colonization and 315

control therefore allows for flexible categorization of, for example, extensively used grassland 316

and regulated river systems, depending on the purpose of the respective studies. 317

The geo-biosphere is limited, and this limitation constrains SEM: As sub-system of the geo-318

biosphere, SEM inherits the limits of the former, and cannot expand indefinitely.1 This 319

limitation distinguishes SEM from a thermodynamic system, which, by definition, is too 320

small to impact the state of its surroundings. This limitation of the extent of SEM is so central 321

that we propose to amend the definition of the concept: 322

As subset of the biophysical process of the geo-biosphere, socioeconomic metabolism is 323

constrained by the limited biophysical resources of the Earth. 324

The sketch in Fig. 2a can be redrawn to show the geo-biosphere as part of social and 325

biophysical spheres of causation (Fig. 2b). The geo-biosphere is divided into a section under 326

human control, which is often called ‘anthroposphere’,2 and the remainder, the natural 327

environment. 328

329

1 For the foreseeable time, metabolically significant expansion into space is prohibited by large energy

costs.

2 We refer to appendix A for a discussion of the relation between socioeconomic metabolism and the

anthroposphere.

2.2.3. The relationship between socioeconomic metabolism and the economy. 330

Daly and Farley (2004) discuss two different ways of looking at the relationship between the 331

economy and the environment. First, one can perceive natural ecosystems as subsystem of the 332

man-made economy, a subsystem that provides us with resources and receives our waste 333

flows, whose services – if necessary – can be substituted by economic processes, and whose 334

limitations can be overcome by technology deployment (Figure 3a). To put more emphasis on 335

the importance of ecosystem services to the economy, ecological economists and many others 336

have been promoting a different perspective. They propose to consider the economy as sub-337

system of the natural environment (Figure 3b). The latter view seems to have become the 338

predominant perspective amongst researchers and accountants concerned with environmental 339

issues. Fig. 3b can now even be found in the UN System of Economic and Environmental 340

Accounts (SEEA) (figure 3.1 in UN (2012)), which provides guidelines for the accounting of 341

the physical dimension of monetary stocks and flows recorded in the system of national 342

accounts (UN, 2008). Figure 3b also appears in Scott Cato (2009) and in a similar version in 343

Rockström (2015); it illustrates that economic activity is constrained by environmental limits 344

and suggests that environmental sustainability is a precondition for economic sustainability. 345

While plausible at first glance, we see several problems connected to the system in Figure 3b. 346

1) The economy comprises non-tangible assets like software and information, and socially 347

constructed economic objects including liabilities and goodwill, which are not part of the 348

biophysical reality. In Figure 5.1 of the SEEA, for example, economic and environmental 349

assets are shown as two overlapping, but distinct sets. That seems to contradict the earlier 350

notion of the economy as subset of the environment. Daly and Farley (2004) warn that the 351

‘economy’ in their version of Figure 3b contains only the part of the economy that has a 352

physical dimension. The non-tangible and perishable part of the economy, including non-353

tangible assets and service flows, is not accurately represented in Figure 3b. 354

2) There is no notion of a social dimension in Figure 3b, which is one dimension of 355

sustainable development. 356

3) Figures 3a and 3b are often seen as irreconcilable or as arising from different worldviews, 357

although it is acknowledged that the representation of the economy in Figure 3b only 358

comprises its physical aspects (Daly and Farley, 2004). We argue that neither of the two 359

representations in Figure 3 fully acknowledges the importance of physical limits to economic 360

activity and the importance of non-physical, non-tangible objects in economic systems. 361

The representations in Figure 3a and 3b are therefore both unsatisfactory. The upper one is 362

criticized by ecological economics as disregarding the physical constraints posed by the 363

environment and the lower one is hard to accept for many economists and sociologists as it 364

only comprises the physical aspects of the economy. We see a necessity for clarifying these 365

issues to enable economists to look at non-physical parts of the economy as option to 366

reconcile economic growth with environmental sustainability. This clarification would 367

provide a theoretical justification for alternative economic concepts including the steady-state, 368

spaceman, or performance economy (Boulding, 1966; Daly, 1991; Stahel, 2006). In section 369

2.2.4, we present an integration of Figures 2b and 3b that overcomes the shortcomings of the 370

scheme in Figure 3b and that clarifies the relationship between SEM, the economy, and the 371

environment. 372

373

374

Figure 3: Two antipodal concepts of economy-environment interactions. a) The environment as 375

subset of the economy. Drawn after Figure 2.1 in Daly and Farley (2004). b) The economy as subset 376

of the environment. Drawn after Figure 2.3 from Daly and Farley (2004). This figure also appears in 377

the SEEA (UN, 2012). 378

379

2.2.4. Synthesis 380

Since all economic activities are human-controlled activities, all economic objects and events 381

must be part of the social sphere of causation. What separates an economic object or activity 382

from any social object and activity? We apply the threshold concept developed in Pauliuk et 383

al. (2015a) and propose a scarcity threshold to distinguish economic processes from other 384

social processes. With the common notion of the economy as allocation of scarce resources to 385

competing ends there are always non-scarce objects, both in the biophysical and social sphere 386

of causation, which do not need allocation by humans. This lack of scarcity can be a result of 387

abundance (oxygen) or a lack of meaningful inclusion of these objects into the economy 388

(undiscovered resources). To accommodate the relationship between SEM and the natural 389

environment, we also introduce an impact threshold to distinguish those parts of the natural 390

environment that are substantially impacted by human activities from those that remain 391

virtually unchanged. The overlap of biophysical and social spheres of causation, together with 392

three thresholds for human control, scarcity, and human impact, respectively, leads to the 393

drawing in Fig. 4. Reality is divided into seven compartments, which are further described in 394

Table 1. 395

396

Figure 4: Formalization of the sketch in Figure 2 and the introduction of the scarcity and impact 397

thresholds. The intersection of biophysical and social spheres of causation (dash-dotted ovals), 398

together with the thresholds for human control, scarcity, and human impact (dashed lines and ovals), 399

allow us to establish a meaningful relationship between different concepts. The scheme describes the 400

boundaries between the economy and the social sphere of causation, between the biophysical basis of 401

society (society’s biophysical structures and socioeconomic metabolism) and the economy, and 402

between the economy and the natural environment. The seven compartments in the scheme are 403

explained in Table 1. 404

The scheme in Fig. 4 demonstrates that the economy and the environment are not subsets of 405

each other, but that each of the two realms extends into both the biophysical and social 406

spheres of causation. Socioeconomic metabolism, however, is a subset of the biophysical 407

sphere of causation. The message conveyed by Figure 3b becomes more precise when the 408

term ‘economy’ is replaced by ‘biophysical basis of society’, which it is well in line with the 409

reasoning given in Daly and Farley (2004). Fig. 4 shows that there is a clear and important 410

distinction between the economy and society’s biophysical basis. 411

Table 1: Description of objects and events in the seven compartments in the refined scheme in Figure 412

4. 413

Com

part

ment

Name Example for objects Example for events Bio-

phys.

reality

Social

reality

Natur-

al

envi-

ron-

ment

Eco-

nomy

1 Undiscovered

natural objects, part

of biophysical but

not part of social

reality

Undiscovered natural

resources

Processes in the inner of

the Earth x x

2 Discovered nature,

part of social reality

but not part of the

economy, no

significant human

influence

Deep sea species, trees in

remote wilderness areas,

pristine waterbodies

Volcanic events, global

flows of, e.g., sodium or

chlorine, whose cycles are

hardly distorted by human

activity (Klee and

Graedel, 2004)

x x x

3 Nature that is not

part of the economy

but experiences

significant human

influence

Estuaries, mountain forests,

glaciers, controlled wolf

populations, insects, rats

Forest growth, glacier

runoff x x x

4 Nature that is part of

the economy

“natural assets or

resources”

Scarce and useful nature, not

sufficiently controlled by

humans to be part of the

SEM, depending on system

boundary choice:

Undeveloped mineral

resources, crops on the field,

managed forests

Freshwater flows,

absorption of atmospheric

nitrogen by cultivated

plants

x x x x

5 Socioeconomic

metabolism and the

biophysical

structures of society

All biophysical objects and

phenomena with a sufficient

level of control by human

agents: industry, products

in use

All production activities,

disposal processes, and

use of artifacts, that

constitute society’s

metabolism

x x x

6 Intangible economic

goods

Everything that is not

physical but part of the

economy: service flows, bank

deposits, liabilities,

copyright, skills, brands

Trade on the stock market x x

7 Intangible non-

economic objects

Democracy, family relations,

values, perception of ‘good

life’

Democratic elections,

interaction between

people

x

414

The distinction between economy and SEM leads to a clarification of the meaning of Fig 3b. 415

Another consequence of this distinction concerns the application of the laws of 416

thermodynamics to the economy: Because the economy also comprises non-tangible objects, 417

thermodynamics, which only apply to biophysical objects, do not necessarily apply to the 418

economy as a whole. This distinction may serve as a theoretical foundation for economic 419

concepts that aim at reconciling economic growth with biophysical constraints. Economic 420

growth may be decoupled from biophysical constraints if the economy expands into the non-421

physical realm (sphere 6 in Fig. 4). 422

423

2.3. SEM as paradigm 424

We now return to the question whether SEM, which comprises the study of events in society’s 425

biophysical basis in a systems context, qualifies as "universally recognized scientific 426

achievement[] that, for a time, provide[s] model problems and solutions for a community of 427

practitioners” (Kuhn, 1996 [1962]). A paradigm prescribes 428

I. what the research is about (object of research) 429

II. the type and structure of research questions asked 430

III. how the research is conducted (research methods) 431

IV. how the results are to be interpreted 432

Below we provide a list of statements that describe SEM from our perspective and tag each 433

statement with one or more of the four categories: ‘object of research’ (I), ‘type of research 434

questions’ (II), ‘research methods’ (III), and ‘interpretation’ (IV). 435

436

SEM describes an object of research. SEM comprises the processes and flows to build 437

up and maintain the bio-physical structures of society. SEM research necessarily contains 438

a description of these structures. [I] 439

The notion of SEM suggests that the study of the biophysical basis of society follows 440

both physical laws and social mechanisms/rationales. Physical laws such as the 441

conservation of mass and energy motivate the tracing of mass and energy flows in 442

society, while social rationales motivate the use of economic models as well as different 443

forms of social, cultural, and economic inquiry. [I, II, III, IV] 444

The notion of SEM recognizes the interconnection of bio-physical and social 445

realities, which is manifested in multi-layer economic-environmental accounting (UN, 446

2012), the development of integrated economic and physical frameworks to describe and 447

analyze SEM (Schmidt et al., 2012), and the debate about the difference between these 448

models, e.g., (Merciai and Heijungs, 2014; Weisz and Duchin, 2006). [II, III, IV] 449

The notion of SEM recognizes the complexity of society-nature interactions, which 450

motivates the study of supply chains with LCA or IO, emergent phenomena like 451

industrial symbiosis or complex recycling systems, or feedback mechanisms on different 452

levels. [II, III, IV] 453

The notion of SEM acknowledges that both biophysical and social reality extend 454

beyond society’s biophysical basis, which is best illustrated by the discussion on 455

boundaries in section 2.2. [I, II, IV] 456

The notion of SEM acknowledges the limitedness of the natural environment, which 457

is reflected in the amended definition of the concept provided in section 2.2.2. [II, IV] 458

The notion of SEM acknowledges the importance of conservation laws, which 459

includes mass and energy conservation for physical, and conservation of monetary 460

quantities for economic models. [III] 461

The notion of SEM acknowledges significant human control of his ecological niche, 462

and holds mankind responsible for the events within society and their consequences for 463

the natural environment. This responsibility is well reflected by the introduction of the 464

control threshold, by the current political debate, and by the different methods that study 465

humanity’s impact on the environment. [II, IV] 466

The notion of SEM implies the existence of a boundary between human society and 467

nature. The actual specification of that boundary is left to the specific accounting 468

frameworks and system definitions (cf. section 2.1). [I, II, IV] 469

The notion of SEM gives meaning to research questions and approaches that would 470

not make sense under other paradigms (Kuhn, 1996 [1962]). One example is the 471

transfer the concept of allometry (West, 1997) from biological organisms to human 472

society (Dalgaard and Strulik, 2011). Another example is the application of complex 473

network theory to regional metabolism (Yao et al., 2015) and to energy distribution 474

(Jarvis et al., 2015). [II] 475

476

These presuppositions make clear that SEM is more than just a metaphor borrowed from 477

biology. Instead, it is a modification of the metabolism concept that is applicable to the 478

biophysical basis of human society. Its definition has matured for about two decades, and 479

now, it comprises many central aspects of state-of-the-art research on society’s biophysical 480

basis and society-nature interactions. We believe therefore that SEM represents a paradigm 481

for this type of research. 482

483

3. Illustrating the use of socioeconomic metabolism (SEM) as paradigm 484

3.1. SEM as element of positive science and its relation to economic concepts and 485

industrial ecology 486

In terms of the categories identified by Binder et al. (2013), SEM is an analysis-oriented 487

paradigm that implies a bidirectional relationship between society and nature and that 488

assumes an anthropocentric perspective on the ecological system. It is a neutral or positive 489

concept, which means that its application allows us to describe and analyze the biophysical 490

basis of society independent of any normative claims regarding how this basis should evolve. 491

It allows us to clearly distinguish between questions about ‘what is and why’ from questions 492

about ‘what should be’. Making this distinction clear in all research on the biophysical basis 493

of society would allow all scholars to use and expand a common knowledge base, irrespective 494

of their motivation or intention. 495

Because of its positive nature, we argue that SEM is a suitable paradigm for studying the 496

biophysical basis of different normative economic concepts including the circular economy 497

(Yuan et al., 2006), the spaceman economy (Boulding, 1966), the steady-state economy (Daly, 498

1991), the service economy, the blue economy, the performance economy (Stahel, 2006), 499

sustainability economics (Baumgärtner and Quaas, 2010), the 3R concept, cradle to cradle 500

and bio-mimicry (McDonough and Braungart, 2002), roundput systems (Korhonen, 2001), 501

bioeconomy (Kitchen and Marsden, 2011), and industrial ecology (Frosch and Gallopoulos, 502

1989; Graedel and Allenby, 1995). 503

We illustrate this claim using the example of industrial ecology. One of the standard 504

definitions of industrial ecology, given by White (1994), has two parts: a positive, descriptive 505

part and a teleological part that describes the purpose of the field (Ehrenfeld, 2007). White 506

defines industrial ecology as “the study of the flows of materials and energy in industrial and 507

consumer activities, of the effects of these flows on the environment, and of the influences of 508

economic, political, regulatory, and social factors on the flow, use and transformation of 509

resources” (White, 1994). We argue that this part describes socioeconomic metabolism, which 510

would imply that SEM can serve as paradigm for the different methods associated with 511

industrial ecology. White continues by stating “The objective of industrial ecology is to 512

understand better how we can integrate environmental concerns into our economic activities” 513

(White, 1994). This statement is a teleological claim regarding the purpose of industrial 514

ecology research. It implies a normative application of SEM to study the transformation of the 515

bio-physical structures of human society to reconcile the desire for human development with 516

the environmental pressures generated by mankind. Current research in industrial ecology 517

covers a wide spectrum, spanning from purely positive studies for accounting, e.g., Fishman 518

et al. (2014), and foot-printing, e.g., Wiedmann et al. (2015), to prospective analysis (Pauliuk 519

and Hertwich, 2015), and policy design tools, e.g., Rajagopal (2014), where the latter two 520

usually imply normative judgments as to what scenario or policy outcome is more desirable. 521

522

Using SEM as paradigm facilitates a universal description of the biophysical basis of the 523

economy on which the different normative economic frameworks can build upon. The 524

reference to such a common description may increase the credibility of the different 525

alternative economic frameworks and it could facilitate communication between researchers 526

following different economic schools of thought. 527

528

An analogue argument applies to the methods for quantitative systems analysis of society’s 529

biophysical basis, which include MFA, LCA, IO, IAM and CGE models. Many researchers 530

recognize commonality and complementarity of these methods. We would like to contribute 531

to the development of a theoretical basis for the future integration of these methods and 532

believe adopting SEM as research paradigm is a first step. 533

534

3.2. Communicating SEM: Analogies and metaphors 535

Analogies expressed as metaphors have inspired new thinking in the science of industrial 536

systems (Davis et al., 2007; Ehrenfeld, 2004; Korhonen, 2004). Metaphorical use of SEM can 537

make the concept more easily accessible than the more abstract description as paradigm. 538

Easier intellectual access to socioeconomic metabolism may facilitate its application in 539

different research fields, and we present three possible analogies related to SEM: paradigms 540

for macro-level assessment, macro- and micronutrients of socioeconomic metabolism, and the 541

relation between homeostasis and socio-metabolic regimes. 542

3.2.1. SEM as paradigm for assessments on the macro-level 543

Architects and designers rely on engineers, who apply natural scientific principles to turn 544

ideas into functional and safe products. While the system-wide consequences of new products 545

are not addressed by the classical engineering approach, they become crucial for sustainable 546

development strategies, as these are meant to move the system as a whole to a more 547

sustainable state. Policy makers therefore rely on sustainability scientists for the development 548

of optimal macro-level strategies. As engineers rely on the paradigms of natural science to 549

develop products and other solutions that are optimal under local conditions, sustainability 550

scientists need to rely on a paradigm like SEM when assessing under what conditions a 551

proposed sustainable development strategy is viable from a systems perspective. 552

553

3.2.2. The nutrients of society’s metabolism 554

As biological organisms require different types of nutrients to sustain their metabolism, one 555

can consider bulk materials like biomass, fossil fuels, or steel as the ‘macro-nutrients of 556

society’ (Table 2), whereas critical materials (Catinat et al., 2010; Graedel et al., 2012) 557

represent the ‘micro-nutrients of SEM’. The anthropogenic stocks and flows of critical 558

elements such as indium, gallium, or rare earth metals are tiny compared to those of the bulk 559

materials steel or concrete. Nevertheless, they enable essential functionality in modern 560

technology. While individual critical materials can be substituted by others in various 561

applications, the functionalities provided by these materials as a group is critical to the 562

functioning of many modern technologies (Graedel et al., 2013). 563

Table 2: ‘Macro- and micro-nutrients’ of biological and socioeconomic metabolism. 564

Metabolism (biology) Socioeconomic metabolism

Macronutrients

Carbohydrates, protein, fat

Bulk materials

Iron ore, limestone, steel, coal, oil, biomass

Micronutrients

Trace elements, vitamins

Critical materials

Rare earth metals, indium, gold, platinum

565

3.2.3. Homeostasis and socio-metabolic regimes 566

Biological organisms maintain important metabolic parameters, such as the pH value of blood 567

or the temperature of endothermic animals, in a stable regime under changing environmental 568

conditions. This property is called homeostasis (Encyclopedia Britannica Online, 2014). One 569

could argue that socio-metabolic regimes, which describe an idealized and distinct way of 570

organizing SEM, can be seen as the analog of homeostasis in SEM. A socio-metabolic regime 571

is described by certain stable patterns of energy and resource use but also by typical societal 572

features such as economic institutions, population dynamics, and knowledge transfer 573

mechanisms (Haberl et al., 2004; Sieferle et al., 2006; Weisz et al., 2001). Two major regimes 574

were identified based on distinct socio-metabolic profiles: The hunter-gatherer and the 575

agrarian society. The metabolism of current industrial societies, because of its short duration 576

in historic terms and its apparent overuse of natural resources, should not be seen as a regime 577

by itself, but as a transition to a new, yet unknown future socio-metabolic regime (Fischer-578

Kowalski, 2011; Fischer-Kowalski et al., 2014; Krausmann et al., 2008). 579

Rockström and colleagues (2009) and Rockström (2015) propose a ‘safe operating space for 580

humanity’ consisting of a set of planetary boundaries, most of which are global boundary 581

values for SEM parameters, like emissions of reactive nitrogen, or can be translated into such, 582

like atmospheric GHG concentration levels. A future industrial socio-metabolic regime that 583

manages to stay within those planetary boundaries could be seen as an example of 584

homeostasis. 585

586

3.3. The limits of socioeconomic metabolism as paradigm and analogy 587

According to Kuhn (1996 [1962]), a paradigm drastically restricts vision, as it requires 588

researchers to focus on studying some concepts and relations and exclude others. This focus is 589

necessary for the advancement of science, but it may make us blind to see important relations 590

between man and nature. What do we miss by embarking on SEM as paradigm for studying 591

the biophysical structures of society? We briefly discuss two aspects of SEM as paradigm that 592

may provoke criticism. 593

594

3.3.1. SEM, sustainability, and the anthropocene 595

SEM is an anthropocentric concept, and so is sustainability (Haberl et al., 2004; World 596

Commission on Environment and Development, 1987). The notion of SEM implies the 597

existence of a boundary between the ‘human niche’ and the rest of the geo-biosphere, and 598

different levels of human control apply to the human niche and its complement, the natural 599

environment. Given the massive influence of human activity on most of Earth’s ecosystems 600

and the long time scales on which this influence will persist (Barnosky et al., 2012; IPCC, 601

2013; Steffen et al., 2011), one could doubt that the boundary between society and nature will 602

be of relevance in the long run and argue that it should be replaced by more flexible notions 603

like the thresholds for impact and scarcity proposed above. In the anthropocene, humanity has 604

to manage salient global bio-physical parameters, like atmospheric GHG concentrations, that 605

directly and indirectly impact the biophysical processes in most of Earth’s ecosystems. Hence, 606

the control threshold and the boundary between SEM and the natural global environment may 607

become obsolete if human control and influence on the global ecosystem continues to grow 608

and shape the global socioecological system along with the natural driving forces (Steffen et 609

al., 2011). 610

611

3.3.2. SEM-based models for sustainable development 612

Using SEM as paradigm in environmental engineering provides the rationale for applying the 613

engineering approach to manage society’s material and energy turnover. Consider, for 614

example, the use of engineering tools like MFA and LCA to assess the environmental 615

performance of countries, regions, or product systems. An important criticism of some SEM-616

based engineering models is their pursuit of efficiency improvement and incremental changes, 617

rather than exploring qualitative changes in the metabolism, such as lifestyle changes or a 618

shift of transport mode. For example, systems designed to study the relation between 619

transportation service and GHG emissions, like the one used by Modaresi et al. (2014), allow 620

for studying efficiency improvements for all individual processes and the system as a whole. 621

They are too limited, however, to explore qualitative changes, like a shift between different 622

modes of transport, reduced consumption levels due to changes in consumer lifestyle and 623

attitude, or the emergence of new industries, products, and services. SEM-based engineering 624

models alone cannot capture effects that are mostly driven by social dynamics. Combining 625

SEM-based engineering models with agent-based modeling (Axtell and Andrews, 2002) or 626

economic models that capture consumer choices and price effects, e.g., (Bouman et al., 2000; 627

de Vries et al., 2001; Kitous, 2006; Loulou et al., 2005), helps to widen the scope of the 628

engineering approach to transforming society’s metabolism. 629

Conclusion 630

This work offers some conceptual clarifications that may be of value irrespective of a possible 631

future role of socioeconomic metabolism as paradigm. It may serve as reference to 632

practitioners who wish to navigate the landscape of concepts to describe socioecological 633

systems. Still, we believe that the greatest potential of the concept SEM lies in its unifying 634

nature as boundary object and paradigm for systems approaches that study the biophysical 635

basis of society and how this basis determines natural resource use and generation of 636

environmental pressures by human society. Applying SEM as paradigm may facilitate the 637

combination and integration of existing accounting frameworks and assessment methods, as 638

well as the development of new research questions. More robust assessment and 639

comprehensive understanding of the system-wide effects of sustainable development 640

strategies may be the result. 641

642

Appendix A. Socio-economic metabolism and the anthroposphere 643

The level of control by human agents is not the only possible extrinsic property to distinguish 644

between human and natural systems. More examples are presented in Table A.1 for possible 645

threshold-based definitions of a commonly used concept, the anthroposphere (Baccini and 646

Brunner, 2012 [1991]). Table A.1 shows the difficulties that arise when one tries to specify 647

exactly what is comprised by the anthroposphere. While some extrinsic properties, like ‘man-648

made’, ‘man-owned’, and ‘impacted by human activities’, would lead to clear 649

misconceptions, as can be seen from the conflicts listed in the table, others, notably the 650

definitions based on control/colonization and the spatial definition, seem to lead to more 651

meaningful conceptualizations of the anthroposphere. 652

In absence of a consensus on which definition to choose, practitioners have the freedom to 653

choose between different extrinsic properties that lead to meaningful definitions, but their 654

choice should be made explicit| (Pauliuk et al., 2015a). Stipulating that socioeconomic 655

metabolism and ‘metabolism of the anthroposphere’ should be synonyms not only in casual 656

use, which they already are, but also in exact terms may help to establish a consistent and 657

‘light-weight’ framework of definitions. 658

Table A.1: Possible extrinsic properties for establishing a concise division between the 659

anthroposphere and the natural environment in the global socioecological system. In addition to the 660

possible definitions of the anthroposphere as collection of objects described here, the anthroposphere 661

can also be defined as compartment of space, as in Baccini and Brunner (2012 [1991]). 662

663

“The anthroposphere

comprises those

objects that are…”

Advantages Conflicts

…made by humans

(anthropogenic)

Covers all man-made

artifacts, easy to

operationalize for

macroscopic artifacts

Abandoned and discarded artifacts and

emitted substances are often regarded as

part of nature.

Role of natural objects, plants, and animals

under human control is left unclear.

…owned by humans

or human institutions

Covers all artifacts owned by

humans or human

institutions.

Definition is easy to

operationalize

Ownership rights can be established upon

objects that are beyond human reach, like

undeveloped mineral resources.

Abandoned buildings and obsolete

products may not have an owner, but may

still be considered as part of ‘culture’.

…controlled or

colonized by humans

or human institutions

Notion of colonization and

control established in the

literature

Definition is difficult to operationalize,

how is control measured and what should

be the threshold?

…significantly

impacted by human

activities

Allows to capture the part of

nature which human

activities have an impact on

in a single concept

Definition is difficult to operationalize,

how is impact measured and what should

be the threshold?

Impact goes much further than colonization

and control, and this may not be the

intention behind ‘anthroposphere’.

One can argue that there is significant

human impact on almost all ecosystems,

which would make the distinction between

biosphere and anthroposphere obsolete.

..within certain spatial

boundaries where

human activities

dominate the natural

ecosystem

Definition is easy to

operationalize: The

anthroposphere describes

“the space in which

biological and cultural

activities of human beings

take place” (Baccini and

Brunner, 2012 [1991]).

Often, natural systems and man-made

systems mix, for example, in cities,

pastures, and on fields, and detail would be

lost if ‘boxes’ would be used to separate

nature from culture.

Some human activities extend into other

spheres: air travel (atmosphere), mining

(geosphere), or space stations (space).

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