“A sociometabolic reading of the Anthropocene: Modes of subsistence, population size and human impact on Earth”

Marina Fischer-Kowalski, Fridolin Krausmann and Irene Pallua. 2014.  The Anthropocene Review, vol. 1, no. 1: pp. 8-33.
We search for a valid and quantifiable description of how and when humans acquired the ability to dominate major features of the Earth System. While common approaches seek to quantify the human impact upon the carbon cycle by identifying the area of land cleared by humans, our point of departure is different human modes of subsistence, and we base our analysis on their social metabolism, in particular their energy metabolism. As a starting point, we use Ehrlich’s classical IPAT formula, and give it a specific interpretation: human impact on Earth = population size × affluence (interpreted as energy available per person) × technology – for each mode of subsistence. The overall impact (or rather human pressure) then equals the composite sum of these. We qualitatively describe the functional characteristics of hunter gatherers, agrarian and industrial modes of subsistence such as population dynamics, energy regime and the technologies by which they interact with their environment. In a ‘toy’ model, we translate these considerations into global numbers for the past millennia: we estimate the respective population sizes and affluence (energy), and finally also technology concerning its impact on the carbon cycle. We see a major historical dividing line around AD 1500: until then, human population growth and metabolic rates carry about equal weight in increasing human pressure on the environment approximately fivefold from the year AD 1 onwards. From then on, the overall pressure of humanity upon the Earth increases by one order of magnitude; energy intensity contributes to this rise by roughly tripling the impact of population growth. Technology, because it is based upon a shift from biomass to fossil fuels (and other ‘modern’ energy carriers), does not moderate this impact, but enhances it by a factor of 1.5.


Co-authored with Katie Marshall

How do we define the beginning of the Anthropocene?  This question invites controversy because it depends on what metric you happen to like using.  Some researchers argue for a sociological measure of the Anthropocene (Ellis et al., 2016), while others are content to use the mark left in the geological record (Zalasiewicz, Waters & Head, 2017). This controversy has led to much discussion (Lewis & Maslin, 2015), with suggested dates associated with moments in human history ranging from the onset of fossil fuel use, the development of the atomic bomb, or even the dawn of agriculture.  But it is clear that the question is interdisciplinary–it sits squarely at the intersection of social science, geology, physiology, and ecology. What common currency do these different fields have?  Marina Fischer-Kowalski and her colleagues suggest using metabolism.

Metabolism is a central concept in biology.  It is the sum of all chemical reactions that take place in the body, involving all the fuels that are broken down for their chemical energy and all the waste byproducts that are produced.  Of course, measuring every chemical reaction that takes place in an organism is incredibly difficult, so biologists will often measure the rate of oxygen consumption or carbon dioxide production, both of which are useful indicators of how much fuel is being used in central metabolic pathways.

Biologists find that measuring metabolic rate is useful because it provides an indication of animals’ energy usage–how much fuel do they need to maintain their bodies, to grow, and to reproduce?  As a result, James Brown and Jamie Gillooly posited the Metabolic Theory of Ecology: the metabolic rate of individual organisms governs their ecological interactions, because it reflects how much energy the organism needs from the environment to allocate to its life processes (Enquist et al., 2003; Brown et al., 2004). This theory explains the scaling of energetic needs from the individual to the ecosystem, providing a bridge between the physical and chemical processes within individuals to the ecological interactions that govern how entire systems function.

In recent years, social scientists have developed the concept of “urban metabolism:” an analogy that applies the idea of metabolism to the city.  Humans are, after all, just another type of organism that lives in large, complex ecosystems. Indeed, the relationship between total energy use of a city and the ambient temperature of the environment looks almost identical to how that relationship scales for an individual organism (Hill, Munich, & Humphries, 2013).  Humans have just outsourced their individual energetic needs to the city (see Katie’s post on that idea).

If metabolism is a useful conceptual framework for describing both cities and organisms, might the models that we use to study populations of organisms also be useful for describing populations of cities? This question was on our mind as we read the paper by Fischer-Kowalski and her colleagues.

Fischer-Kowalski et al. use quantitative estimates of societal metabolism rates to explore Ehrlich’s classic formula, I = P x A x T. That formula describes the impact of humans on the environment (I) as the product of population size (P), affluence (A), and a technology factor (T) that describes a society’s level of resource use. The authors make some careful estimates of these parameters for three general modes of subsistence (Hunter and gatherer, Agrarian, and Industrial), and then reconstruct time series estimates of the total population in each mode of subsistence from 10,000 BC to 2000 AD.

This is a compelling analysis, but data availability forced the authors to make their best estimates for some calculations. Are there tools and models from population biology that could offer complementary insights? For example, suppose we consider the number of people in each  of the three modes of subsistence as a populations of organisms. Each population has its own intrinsic growth rate, and we might also assume that there is some conversion rate at which hunter-gatherers become agrarian, and at which agrarians become industrial. How could we model that?

Lotka Volterra dynamics

Lotka-Volterra predator-prey dynamics

One approach would be to use the classical Lotka-Volterra (“L-V”) predator-prey equations from biology:  a set of first-order differential equations that describe the dynamics of predators and prey. In the L-V model, each population has a growth rate, and the model includes parameters that describe the interactions of the two populations. In our analogy, we would consider a set of three equations: one for the hunter-gatherer population (i.e., “prey”, unfortunately, in this metaphor), one for the agrarian population (i.e., a predator on the hunter-gatherer population, since hunter-gatherer societies become agrarian over time), and one for the industrial population (i.e., the top-level predator). This model is straightforward to solve, and the data in the paper could provide reasonable estimates of any parameters we’d need.

With this model in hand, we might ask: can it explain the long-term dynamics of these three populations (e.g., Fig. 2 in Fischer-Kowalski) using reasonable values for the growth rates of each population? If not, does that fact provide any insights into how populations grow and transform among these three modes of subsistence?

The Conclusions section of the paper provides some ideas for adding a little more sophistication to this modeling exercise. When discussing the limitations of the IPAT model, the authors explain “It cannot be assumed that the three components – population, affluence and technology – are independent from one another. On the contrary: they are functionally deeply interlinked, but in ways that differ between sociometabolic regimes” (p. 27). They go on to say:

In the hunter gatherer regime, population numbers basically are constrained by available food energy, and the availability of food from ecosystems can hardly be controlled by humans. In the agrarian regime, the relation between food and population becomes more complex: While food energy still constrains population numbers, population growth allows investing more labour and drives technological progress increasing the overall amount of food energy available from agro-ecosystems… In the industrial regime, the link between land and energy availability is largely disrupted, as well as the link between available energy and population dynamics. (p. 27)

All of those assertions sound reasonable, but we could also test them by extending our Lotka-Volterra model. For example, the above quote suggests that hunter-gatherer populations should have some fixed carrying capacity determined by their environment; that in agrarian societies the carrying capacity should be a function of both the environment and the population size; and in industrial societies there should be effectively no carrying capacity. We could readily modify the L-V model along these lines, and again see if it is possible to explain the long-term dynamics of these three populations (e.g., Fischer-Kowalski, Fig. 2) using reasonable values for parameters. If not, would that be grounds for questioning some of the assertions in the above block-quote?

Metabolism is a compelling conceptual framework for describing both cities and organisms. It provides a common currency for linking disparate academic disciplines, and Fischer-Kowalski convincingly use it to propose a definition for the beginning of the Anthropocene and illustrate changing anthropogenic impacts through time. As biologists, it makes us wonder: how far does this metaphor go? What other similarities are there between cities and organisms, and what other tools and models from biology could be brought to bear on the study of cities?

Brown, J. et al. 2004. “Toward a Metabolic Theory of Ecology.” Ecology 85, pp. 1771-1789, https://doi.org/10.1890/03-9000.
Ellis, E. et al. 2016. “Involve social scientists in defining the Anthropocene.” Nature 540, pp. 192–193, doi:10.1038/540192a.
Enquist, B. et al. 2003. “Scaling metabolism from organisms to ecosystems.” Nature 423, pp. 639–642,doi:10.1038/nature01671.
Hill, R., Munich, T. & Humphries, M. 2013. “City-Scale Expansion of Human Thermoregulatory Costs.” PLOS ONE 8(10): e76238, https://doi.org/10.1371/journal.pone.0076238.
Lewis, S. & Maslin, M. 2015. “Defining the Anthropocene.” Nature 519, pp. 171–180, doi:10.1038/nature14258.
Zalasiewicz, J., Waters, C. & Head, M. 2017. “Anthropocene: its stratigraphic basis.” Nature 541, p. 289, doi:10.1038/541289b.

Urban Metabolism and Degrowth, part 2


It continues Part 1’s discussion of two readings: “Democracies with a future: Degrowth and the democratic tradition,” by Marco Deriu, and “De-growth: Do you realise what it means?” by Ted Trainer

Co-authored with Robert Bailey

Manif EPR Lyon Bellecour banderole décroissance

The Party for Degrowth, rally in Lyon, 2007. © Yann Forget / Wikimedia Commons / CC-BY-SA-3.0.

Continue reading

Urban Metabolism and Degrowth, part 1

Democracies with a future: Degrowth and the democratic tradition
Marco Deriu. 2012.  Futures vol. 44, pp. 553–561.
ABSTRACT (partial):
The interrogation of a possible connection between degrowth and democracy inspires some questions of political epistemology. Is degrowth a socio-economic project which can be simply proposed as an ‘‘issue’’ and a ‘‘goal’’ in the democratic representative system, without discussing forms and processes of the political institutions themselves? Continue reading

“Urban Metabolism and the Energy Stored in Cities: Implications for Resilience”

David N. Bristow and Christopher A. Kennedy. 2013.  Journal of Industrial Ecology, vol. 17, no. 5: pp. 656-667.
Using the city of Toronto as a case study, this article examines impacts of energy stocks and flexible demand in the urban metabolism on the resilience of the city, including discussion of Continue reading

“Environmental Crises and the Metabolic Rift in World-Historical Perspective”

Moore, Jason W. 2000.  Organization & Environment, vol. 13: pp. 123-157.
This article proposes a new theoretical framework to study the dialectic of capital and nature over the longue duree of world capitalism. The author proposes that today’s global ecological crisis has its roots in the transition to capitalism during the long sixteenth century. The emergence of capitalism marked not only a decisive shift in the arenas of politics, economy, and society, but a fundamental reorganization of world ecology, characterized by a “metabolic rift,” Continue reading

Urban Metabolism

Following our series on “Cities and Our Future,” I’m pleased to introduce the second of our special programs on the theme of the Urban Anthropocene. Starting today, and running through April, we will have a series of posts that take up the idea of “urban metabolism:” the analogy between cities and organisms that focuses attention on the systems by which cities obtain resources, and generate and dispose of wastes.

Continue reading

Reviving Municipal Housekeeping

This is the third in Dr. Rosenthal’s three-part series on “Cities and Our Future: Governance in the Anthropocene.” Here are links to the first, and second posts. She will present her ideas at a panel discussion on the OU campus on March 6, 2018; here is the poster for the event.

Roots of Municipal Capacity-Building

In the late 19th century, a movement for municipal reform gained prominence across the nation, led by the emergence of Continue reading

Green Cities, Red States

This is the second in Dr. Rosenthal’s three-part series on “Cities and Our Future: Governance in the Anthropocene.” Click for the first post.

Cities have variously been characterized as “limited” (Peterson 1981), “dependent” (Kantor 1995), and “ungovernable” (Ferman 1985.) Urban scholar Paul Peterson in his seminal work, City Limits, concluded that cities are seriously limited by Continue reading

Who Will Lead?

This is the first in Dr. Rosenthal’s three-part series on “Cities and Our Future: Governance in the Anthropocene.”

When President Trump proclaimed that the United States would withdraw from the Paris climate accord, he claimed to represent the “citizens of Pittsburgh not Paris.” Pittsburgh Mayor Bill Peduto was quick to respond, tweeting Continue reading

“Moving from ‘matters of fact’ to ‘matters of concern’ in order to grow economic food futures in the Anthropocene”

Hill, A. 2015.  Agriculture and Human Values, vol. 32: pp. 551-563.
Agrifood scholars commonly adopt “a matter of fact way of speaking” to talk about the extent of neoliberal rollout in the food sector and the viability of “alternatives” to capitalist food initiatives. Over the past few decades Continue reading

Outsourcing our thermoregulation to the city

The cold in Yakutsk, Russia. Courtesy of http://www.snowaddiction.org

In the middle of winter in Yakutsk, Russia, the average temperature is -34 °C–so cold that the difference between Celsius and Fahrenheit is negligible.  Overnight dips to -42 °C are common.  For the 270,000 people who live there, time outside is to be avoided—eyeglasses freeze to your face, eyelashes freeze, your nose hairs freeze.  October to April is spent scurrying around from house to house and spending Continue reading

“Cities in the age of the Anthropocene: Climate change agents and the potential for mitigation”

Pincetl, S. 2017. Anthropocene, Vol. 20, pp. 74-82.
Cities are human creations where many of the emissions causing climate change originate. Every aspect of daily life in cities Continue reading

Pathogens and the Anthropocene: Germs, Genes, Geography, Part 2

[This is the continuation of the post from last week.]

To speak of an “Anthropocene for pathogens” is to imagine the ways that human transformation of the environment has shaped the ecology and evolution of infectious microbes. In other words, it is to imagine Continue reading

Pathogens and the Anthropocene: Germs, Genes, Geography, Part 1

The smallpox virus

We welcome our colleague Kyle Harper to the blog; his bio is on the OU contributors page. His book, The Fate of Rome: Climate, Disease, and the End of an Empire, is now available from Princeton University Press. Continue reading