The accelerating pace of climate change is forcing consideration of the relationships among global change, the role of economic growth as "forcing mechanism", and the necessary policy responses. To date the only politically acceptable responses to climate change involve technological approaches designed to maintain the growth-based economic status quo. As Moriarty and Honnery (2010) show, these "solutions" are unlikely to work. Moreover, since the human enterprise is a fully contained subsystem of the non-growing ecosphere, continued material growth necessarily results in the entropic disordering the ecosphere. The purpose of this paper, therefore, is to make the case that sustainability requires achieving zero economic growth near the theoretical optimal scale (the point of maximum attainable net benefits) of the global economy. Unfortunately today's 'economy-in-overshoot' may already exceed optimal scale and both political and conceptual barriers impede corrective action.

Growth and Sustainability Don’t Mix

In their 2008 landmark paper on carbon emissions trends, climatologists Kevin Anderson and Alice Bows asserted that:

This unusually direct extension of scientific angst into the policy arena assumes an unambiguous connection among climate change, the role of economic growth, the necessary political response and consequences for global development.

Needless to say, not everyone accepts this connection. Anderson’s and Bows’ warning, and the equally alarming findings of many other scientists and organizations (Cairns 2010; NAS 2010a,b,c), are going largely unheeded in the political arena. Talk of a planned economic recession in the midst of a chaotically unplanned one is dismissed as lunacy. Techno industrial society remains in deep denial of the global ecological crisis and when, occasionally, decision-makers are pricked by a sense of urgency they fall back on market forces and humanity’s demonstrated technological wizardry in hopes of maintaining the growth-bound status quo.

But there is a problem—technology pressed to new limits has become an unreliable if not treacherous ally in the sustainability wars, particularly if sustainability is defined as sustaining the status quo. British Petroleum's (BP) drilling rig explosion in April of 2010, and the inability to cap the the subsequent oil well blow off in the depths of the Gulf of Mexico, are just the most recent reminders. According to the National Oceanic and Atmospheric Administration over 40,000 barrels a day are gushing into the ocean (with some scientists estimating over 100,000). A worst case scenario includes the killing of fish breeding areas and coral reefs, and consequent effects of depleting and reducing oxygen to levels so low that it may kill off much of the sea life near the plumes and create vast dead zones. Perhaps compounding the damage is BP's unprecedented use of toxic chemical dispersants, over 700,000 gallons, as of May 20, 2010, which could pose a significant threat to the Gulf of Mexico's marine life. Thus, the "technical fix" is not a fix at all, but may only add to the catastrophe.

After reviewing available technological options for confronting climate change Moriarty and Honnery (2010) reasonably conclude that the time has, in fact, come to rethink modern society’s addition to economic growth.. This commentary unreservedly supports Moriarty’s  and Honnery’s (2010) conclusion on fundamental grounds.

My argument starts from two indisputable premises not even directly related to climate change:

1) By modern interpretations of the second law of thermodynamics, the human economy is a self-organizing far-from-equilibrium dissipative structure (Prigogine 1997) that grows and maintains itself by extracting low-entropy energy/matter (exergy) from its ‘environment’ and by injecting degraded waste by-products back into the environment (Schneider and Kay 1994, 1995; Kay and Regier 2000). 

2) The human enterprise is a fully contained, open, dependent, growing sub-system of a materially closed, non-growing, finite ecosphere (Daly 1991a, 1992; Rees 1995).

Taken together, the economic and ecological implications of these premises are profound. The sustainability of humans and their economies depend entirely on continued access to pre-existing stocks/gradients of energy and matter (exergy) found in nature and on the viability of the productive ecosystems of which humans are a part (Rees 2003; 2006a,b). Ironically, however, the human enterprise, as a sub-system of the ecosphere, can produce itself and grow (ascend ‘far-from-equilibrium’) only by consuming and dissipating those same gradients and ecosystems.

This biophysical reality anticipates or explains virtually all the so-called ‘environmental problems’ confronting modern society. Fisheries collapse, tropical deforestation, biodiversity loss, falling water tables, soils depletion, peak oil, etc. (Cairns 2010; Singer 2010), show that even current rates of consumption by humans exceed rates of resource renewal or replenishment in nature; rising carbon emissions (and anthropogenic warming), ozone depletion, ocean acidification, chemical contamination of food-webs—in fact, all forms of pollution—show that humanity’s dissipative output already exceeds the assimilative capacity of the ecosphere.

This should not be a surprise—there are no exemptions from the second law. Beyond a certain point, sustaining the human enterprise necessarily comes at the expense of increasing the entropy of the ecosphere. Humanity is now living, in part, by consuming and permanently dissipating natural capital essential to its own existence. As this pathology deepens, the behaviour of vital life-support systems will become increasingly erratic and unpredictable. Pushed far enough some systems will succumb completely to overuse and degradation.

All of which brings us to the question of growth. Prevailing economic reasoning sees no significant constraints on material growth because it ‘externalizes’ the ecosphere and ignores the second law. Indeed, neoliberal economic models are so abstracted from biophysical (and social) reality that they can make only marginal contributions to the sustainability debate (Daly 1991b).

That said, we can use micro-economic logic to make the theoretical case for zero growth, even economic contraction, at the macro scale (Figure 1). Everyone recognizes that economic activity produces valuable goods and services (material benefits). These benefits are easy to identify and quantify with market prices. At the same time, every act of production and consumption generates costs, many of which are difficult to identify and harder to price in dollar terms (e.g., the costs associated with increasing entropy). Conventional reasoning also accepts that there will be diminishing returns from growth—i.e., as the scale of the human enterprise increases, the marginal value of growth will gradually decline. Meanwhile, the marginal costs—resource depletion, ecosystem degradation and pollution, community disruption—will generally increase. This convergent relationship implies that at some point on the growth trajectory, the value of an additional increment of growth will be negated by the corresponding costs.

This critical point (point ‘a’ on Figure 1) actually represents the optimal scale of the human enterprise. Here the net aggregate value of the economy (sum of all benefits minus sum of all costs) will have reached a maximum. If we grow beyond ‘a’, the costs of ‘progress’ regularly exceed the gains and total net benefits shrink. The economy will have entered a phase of what ecological economist Herman Daly calls ‘uneconomic growth’, counter-productive growth that makes society poorer, not richer.  

It is possible that today’s global-economy-in-overshoot already exceeds optimal scale (Rees 2006b, WWF 2008) and that the global socio-ecosystem has begun its decline (climate change is only the best publicized symptom). This should blunt any criticism of Anderson’s and Bow’s (2008) intrusion into the policy arena and supports Moriarty’s and Honnery’s (2010) conclusion. Regrettably, at least two major obstacles prevent the world from testing the overshoot hypothesis or acting upon the results: 1) all governments are fixated on quantifying the easily measurable benefits of growth, but none focuses equivalent energy on assessing the much-harder-to-measure costs. It is therefore impossible to estimate a reliable benefit/cost ratio for growth; 2) the global economy is structured so that the already wealthy (and powerful) ‘enjoy’ most of the gains from growth while the chronically poor (and powerless) suffer the entropic costs. Those in a position to ‘fix’ the problem have little incentive to act; those most immediately affected by the problem are powerless to act. In these circumstances, decisive action is impossible and growth may well continue, perversely, to shrink the global economy for decades to come!