David P. Turner / April 7, 2020

When I was 20 years old, I picked up a paperback version of “Life and Energy” by Isaac Asimov.  This lucid scientific description of the chemical basis for life was very compelling, indeed, it helped inspire me to pursue a career in biology and ecology.  The time around its publication in the mid 1960s was quite exciting in biology because the fields of biochemistry and cell biology were in full flower; scientists had worked out the role of DNA in regulating cellular metabolism and had achieved a good understanding of the chemistry of photosynthesis and respiration.

Metabolism is broadly defined as the chemical machinery of life, the networked sequences of chemical reactions that build and maintain living matter.  Biologists think of living matter in terms of levels of organization – from cells, through organisms, communities, and the biosphere.

In Asimov’s days, the concept of metabolism was mostly applied at the level of the cell or organism.  However, ecologists in recent years have also applied it in the context of ecosystems and the Earth system as a whole.  Here I would like to consider metabolism at the scale of the technosphere. 

An ecosystem is a biogeochemical cycling entity, e.g. a pond or a patch of forest.  Like an organism, it requires a source of energy and it cycles nutrients such as nitrogen from one chemical form to another.  Strictly speaking, it is the biota (the set of all organisms) that in a sense has a metabolism.  Component organisms are classified into nutrient cycling guilds — most simply as producers (photosynthesizes), consumers, and decomposers. 

Ecosystem metabolism can be described in terms of energy fluxes, as well as the stocks and fluxes of key chemical elements. The element carbon plays a central role in ecosystem metabolism.  Its cycle extends from the atmosphere, through plants, to animals, and to decomposers, then back to the atmosphere.

At the scale of the Earth system, we can likewise talk about biogeochemical cycling guilds and the associated biogeochemical cycles.  Biosphere metabolism is based on photosynthesis on the land and in the ocean.  Biosphere driven element fluxes help regulate the atmospheric chemistry, ocean chemistry, and global climate. 

Despite repeated intervals in the geologic record of Hothouse Earth and Icehouse Earth, the metabolism of the biosphere has run steadily for over 3 billion years.  

Quite recently in geologic time, a new sphere has emerged within the Earth system.  This “technosphere” is the cloak of technological devices and associated human constructs that has come to cover the Earth.  Like the biosphere, it has a metabolism.

We can think about technosphere metabolism in terms of three key factors: energy flows, materials cycling, and information processing. 

Humans are a part of the technosphere and mostly benefit from its metabolism.  The technosphere produces a vast array of goods and services that support billions of people.  However, the metabolism of the technosphere has begun to disrupt the formerly background global biogeochemical cycles.  It is effectively now a geological force and the changes it has precipitated are not necessarily favorable to advanced technological civilization.  Notably, the delivery of vast amounts of CO₂ into the atmosphere is destabilizing the global climate.  A course correction in the evolution of the technosphere is required.

Energy flow into the technosphere is predominantly from the combustion of fossil fuels (coal, oil, and natural gas).  The problem is that the resulting source of carbon to the atmosphere is orders of magnitude greater than the background source from volcanoes.  The background geologic sink for CO₂ by way of mineral formation in the ocean depths is likewise small.

Some of the technosphere-generated CO₂ is sequestered by land plants and in the ocean, but most of it is accumulating in the atmosphere and causing the planet to rapidly warm.  The technosphere has begun to disrupt the entire Earth system. 

The solution, as is well known, is conversion of the global energy infrastructure to renewable energy sources (solar, wind, hydro, geothermal, biomass, and renewable natural gas).  That conversion is a daunting task but technically it can be accomplished.  The challenge is as much to economists and politicians as it is to engineers.

The materials cycling factor in technosphere metabolism is problematic because the technosphere as currently configured is not effective at recycling its components.  Unlike the biosphere, in which nutrients are cycled, there is often a one-way flow of key chemical elements in the technosphere − from a mineral phase, to a manufactured product, to a landfill.

The problem is that sources of the technosphere components are not infinite.  Building the next mega-mine to extract aluminum degrades the biosphere, a key component of the global life support system. 

Again, this is a largely solvable problem using advanced industrial practices.  We now speak of the emerging circular economy and of dematerializing the technosphere.  More comprehensive recycling may require more energy than dumping something into a landfill, but the potential for renewable energy sources is large.

The information processing aspect of technosphere metabolism refers to its regulatory framework.  Regulation requires information flow, a receiver of that information, and a mechanism to act on it.   

Homeostasis at the level of an organism is a clear case of regulation.  Homeostasis of internal chemistry, such as the blood sugar level in mammals, depends on factors including signals based on chemical concentrations, DNA-based algorithms to formulate a response, and organs that implement a response.

Ecosystems also self-regulate in a sense.  Disturbances (e.g. a forest fire) are followed by vigorous regrowth.  As a result, nutrients that are released in the process of the disturbance are captured and prevented from loss by leaching.  Damaged ecosystems, say that lack species specialized for the early successional environment, may deteriorate after a disturbance.

At the global scale, Earth system scientists have long debated the issue of planetary homeostasis.  James Lovelock famously hypothesized that indeed the Earth system (Gaia) is homeostatic with respect to conditions that favor life.  His idea inspired much research, and many significant biophysical feedbacks to global change have been identified.  The biosphere clearly exerts a strong influence on global climate by way of its impacts on greenhouse gas concentrations, specifically through its role as an amplifier in the rock weathering thermostat.

A new research question concerns the degree to which the technosphere is homeostatic.  Continued exponential growth in many of the indices of technosphere metabolism is suggestive of inadequate regulation.  To begin with, the regulatory capability of the technosphere is obviously diffuse and underdeveloped. 

Monitoring is a necessary component of effective management systems but the self-monitoring capability of the technosphere barely existed until quite recently.  An anomalous growth in the atmospheric CO₂ concentration was measured in the late 1950s by atmospheric chemist Charles David Keeling.  This observation was the first clear signal of technosphere impact on the Earth system.

The Landsat series of satellite-borne sensors that monitor land cover change, e.g. deforestation and urbanization, was initially launched in 1972.  These satellites have since tracked the explosive spatial expansion of the technosphere.  A fleet of other satellites now monitors many other features of the global environment.

From synthesis efforts by agencies such as the United Nations Food and Agriculture Organization, we have good observational data on the growth of key technosphere variables like global population size and energy use. 

As far as a decision-making organ for the technosphere, one barely exists at present.  You might say that market-based capitalism is the organizing principle of the current technosphere.  Everyone wants cheap, plentiful energy (the demand side) and the global fossil fuel industry has managed to keep ramping up the supply.  Under the current neoliberal economic regime, the environmental costs are externalized, and no global oversight is imposed.

However, a new constraint has arisen.  The scientific community has built Earth system models to refine our understanding of Earth’s biophysical regulatory mechanisms and to simulate effects of various greenhouse gas concentration scenarios.  These simulations make clear that uncontrolled emissions of CO₂ from fossil fuel combustion must cease or advanced technological civilization will be imperiled.  The 2015 Paris Agreement on Climate Change was a step towards reining in the technosphere, but the influence of that international agreement is not commensurate with the challenges of current global environmental change.

An essential feature of a needed paradigm shift regarding technosphere regulation is the development of a global environmental governance infrastructure.  The technosphere is having global scale impacts on the environment and must correspondingly be evaluated and regulated at the global scale.

A proposed World Environment Organization would not necessarily supersede the traditional nation-state-based architecture of global governance, but it could go a long way towards the required scale of integration needed to address global environmental change issues.

A revamped technosphere metabolism must be built over the course of the 21^st Century in which the energy sources are renewable, the material flows are cyclic, and the regulatory framework is rooted in an understanding of limits.  Societies are more likely to change under extreme circumstances, and the economic shock of the 2020 coronavirus pandemic will certainly qualify as extreme.  As the global economy recovers, there will be significant opportunities to change technosphere metabolism.  Let’s hope they are not wasted.