Nature Reverses on Limits

Last week Nature editorialized,

Are there limits to economic growth? It’s time to call time on a 50-year argument

Fifty years ago this month, the System Dynamics group at the Massachusetts Institute of Technology in Cambridge had a stark message for the world: continued economic and population growth would deplete Earth’s resources and lead to global economic collapse by 2070. This finding was from their 200-page book The Limits to Growth, one of the first modelling studies to forecast the environmental and social impacts of industrialization.

For its time, this was a shocking forecast, and it did not go down well. Nature called the study “another whiff of doomsday” (see Nature 236, 47–49; 1972). It was near-heresy, even in research circles, to suggest that some of the foundations of industrial civilization — mining coal, making steel, drilling for oil and spraying crops with fertilizers — might cause lasting damage. Research leaders accepted that industry pollutes air and water, but considered such damage reversible. Those trained in a pre-computing age were also sceptical of modelling, and advocated that technology would come to the planet’s rescue. Zoologist Solly Zuckerman, a former chief scientific adviser to the UK government, said: “Whatever computers may say about the future, there is nothing in the past which gives any credence whatever to the view that human ingenuity cannot in time circumvent material human difficulties.”

“Another Whiff of Doomsday” (unpaywalled: Nature whiff of doomsday 236047a0.pdf) was likely penned by Nature editor John Maddox, who wrote in his 1972 book, the Doomsday Syndrome,

“Tiny though the earth may appear from the moon, it is in reality an enormous object. The atmosphere of the earth alone weighs more than 5,000 million million tons, more than a million tons of air for each human being now alive. The water on the surface of the earth weights more than 300 times as much – in other words, each living person’s share of the water would just about fill a cube half a mile in each direction… It is not entirely out of the question that human intervention could at some stage bring changes, but for the time being the vast scale on which the earth is built should be a great comfort. In other words, the analogy of space-ship earth is probably not yet applicable to the real world. Human activity, spectacular though it may be, is still dwarfed by the human environment.”

Reciting the scale of earth’s resources hasn’t held up well as a counterargument to Limits., for the reason given by Forrester and Meadows et al. at the time: exponential growth approaches any finite limit in a relatively small number of doublings. The Nature editors were clearly aware of this back in ’72, but ignored its implications:

Instead, they subscribed to a “smooth approach” view, in which “a kind of restraint” limits population all by itself:

There are a lot of problems with this reasoning, not least of which is that economic activity is growing faster than population, yet there is no historic analog of the demographic transition for economies. However, I think the most fundamental problem with the editors’ mental model is that it’s effectively first order. Population is the only stock of interest; to the extent that they mention resources and pollution, it is only to propose that prices and preferences will take care of them. There’s no consideration of the possibility of a laissez-faire demographic transition resulting in absolute levels of population and economic activity requiring resource withdrawals that deplete resources and saturate sinks, leading to eventual overshoot and collapse. I’m reminded of Jay Forrester’s frequent comment, to the effect of, “if you have a model, you’ll be the only person in the room who can speak for 20 minutes without self-contradiction.” The ’72 Nature editorial clearly suffers for lack of a model.

While the ’22 editorial at last acknowledges the existence of the problem, its prescription is “more research.”

Researchers must try to resolve a dispute on the best way to use and care for Earth’s resources.

But the debates haven’t stopped. Although there’s now a consensus that human activities have irreversible environmental effects, researchers disagree on the solutions — especially if that involves curbing economic growth. That disagreement is impeding action. It’s time for researchers to end their debate. The world needs them to focus on the greater goals of stopping catastrophic environmental destruction and improving well-being.

… green-growth and post-growth scientists need to see the bigger picture. Right now, both are articulating different visions to policymakers, and there is a risk this will delay action. In 1972, there was still time to debate, and less urgency to act. Now, the world is running out of time.

If there’s disagreement about the solution, then the solution should be distributed, so that we can learn from different approaches. It’s easy to verify success, by checking the equilibrium conditions for sources and sinks: as long as they’re in decline, policies need to adjust. However, I don’t think lack of agreement about the solution is the real problem.

The real problem is that the research “consensus that human activities have irreversible environmental effects” has no counterpart in the political and economic spheres. Neither green-growth nor degrowth has de facto support. This is not a problem that will be solved by more environmental or economic research.

Limits and Markets

Almost fifty years ago, economists claimed that markets would save us from Limits to Growth. Here’s William Nordhaus, writing about World Dynamics in Measurement without Data (1973):

How’s that working out? I would argue, not well.

Certainly there are functional markets for commodities like oil and gas, but even then a substantial share of the resources are allocated by myopic regulators captive to industry interests.

But for practically everything else, the markets that would in theory allocate across resources, time and space simply don’t exist, even today.

Water markets haven’t prevented the decline of Lake Mead, and they’re resisted widely, including here in Bozeman:

Joseph Stiglitz explained in the WSJ:

A similar pattern could unfold again. But economic forces alone may not be able to fix the problems this time around. Societies as different as the U.S. and China face stiff political resistance to boosting water prices to encourage efficient use, particularly from farmers. …

This troubles some economists who used to be skeptical of the premise of “The Limits to Growth.” As a young economist 30 years ago, Joseph Stiglitz said flatly: “There is not a persuasive case to be made that we face a problem from the exhaustion of our resources in the short or medium run.”

Today, the Nobel laureate is concerned that oil is underpriced relative to the cost of carbon emissions, and that key resources such as water are often provided free. “In the absence of market signals, there’s no way the market will solve these problems,” he says. “How do we make people who have gotten something for free start paying for it? That’s really hard. If our patterns of living, our patterns of consumption are imitated, as others are striving to do, the world probably is not viable.”

What is the price of declining rainforests, reefs or insects? What would markets quote for killing a bird with neonicotinoids, or a wind turbine, or for your Italian songbird pan-fry? What do gravel pits pay for dust and noise emissions, and what will autonomous EVs pay for increased congestion? The answer is almost universally zero. Even things that have received much attention, like emissions of greenhouse gases and criteria air pollutants, are free in most places.

These public goods aren’t free because they’re abundant or unimportant. They’re free because there are no property rights for them, and people resist creating the market mechanisms needed. Everyone loves the free market, until it applies to them. This might be OK if other negative feedback mechanisms picked up the slack, but those clearly aren’t functioning sufficiently either.

Breakthrough Optimism

From Models of Doom, the Sussex critique of the Limits to Growth:

Real challenges will no doubt arise if world energy consumption continues to grow in the long-term at the current rate, but limited reserves of non-renewable energy resources are unlikely to represent a serious threat on reasonable assumptions about the ultimate size of the reserves and technical progress. …

It is not unreasonable to expect that within 30 years a breakthrough with fusion power will provide virtually inexhaustible cheap energy supplies, but should this breakthrough take considerably longer, pessimism would still be unjustified. There are untapped reserves of non-conventional hydrocarbons which will become economic after further technical development and if prices of conventional fossil fuels continue to rise.

At AAAS in 2005, a fusion researcher pointed out that 1950s predictions of working fusion 50 years out had expired … with fusion prospects still 50 years out.

This MIT Project Says Nuclear Fusion Is 15 Years Away (No, Really, This Time)

Expert: “I’m 100 Percent Confident” Fusion Power Will Be Practical
Companies chasing after the elusive technology hope to build reactors by 2030.

Is fusion finally just around the corner? I wouldn’t count on it. Even if we do get a breakthrough in 10 to 15 years, or tomorrow, it’s still a long way from proof of concept to deployment on a scale that’s helpful for mitigating CO2 emissions and avoiding use of destructive resources like tar sands.

Limits to Growth Redux

Every couple of years, an article comes out reviewing the performance of the World3 model against data, or constructing an alternative, extended model based on World3. Here’s the latest:

This study investigates the notion of limits to socioeconomic growth with a specific focus on the role of climate change and the declining quality of fossil fuel reserves. A new system dynamics model has been created. The World Energy Model (WEM) is based on the World3 model (The Limits to Growth, Meadows et al., 2004) with climate change and energy production replacing generic pollution and resources factors. WEM also tracks global population, food production and industrial output out to the year 2100. This paper presents a series of WEM’s projections; each of which represent broad sweeps of what the future may bring. All scenarios project that global industrial output will continue growing until 2100. Scenarios based on current energy trends lead to a 50% increase in the average cost of energy production and 2.4–2.7 °C of global warming by 2100. WEM projects that limiting global warming to 2 °C will reduce the industrial output growth rate by 0.1–0.2%. However, WEM also plots industrial decline by 2150 for cases of uncontrolled climate change or increased population growth. The general behaviour of WEM is far more stable than World3 but its results still support the call for a managed decline in society’s ecological footprint.

The new paper puts economic collapse about a century later than it occurred in Limits. But that presumes that the phrase highlighted above is a legitimate simplification: GHGs are the only pollutant, and energy the only resource, that matters. Are we really past the point of concern over PCBs, heavy metals, etc., with all future chemical and genetic technologies free of risk? Well, maybe … (Note that climate integrated assessment models generally indulge in the same assumption.)

But quibbling over dates is to miss a key point of Limits to Growth: the model, and the book, are not about point prediction of collapse in year 20xx. The central message is about a persistent overshoot behavior mode in a system with long delays and finite boundaries, when driven by exponential growth.

We have deliberately omitted the vertical scales and we have made the horizontal time scale somewhat vague because we want to emphasize the general behavior modes of these computer outputs, not the numerical values, which are only approximately known.

Species Restoration & Policy Resistance

I’ve seen a lot of attention lately to restoration of extinct species. It strikes me as a band-aid, not a solution.

Here’s the core of the system:

speciesReintroCritters don’t go extinct for lack of human intervention. They go extinct because the balance of birth and death rates is unfavorable, so that population declines, and (stochastically) winks out.

That happens naturally of course, but anthropogenic extinctions are happening much faster than usual. The drivers (red) are direct harvest and loss of the resource base on which species rely. The resource base is largely habitat, but also other species and ecosystem services that are themselves harvested, poisoned by pollutants, etc.

Reintroducing lost species may be helpful in itself (who wouldn’t want to see millions of passenger pigeons?), but unless the basic drivers of overharvest and resource loss are addressed, species are reintroduced into an environment in which the net gain of births and deaths favors re-extinction. What’s the point of that?

If the drivers of extinction – ultimately population and capital growth plus bad management – were under control, we wouldn’t need much restoration. If they’re out of control, genetic restoration seems likely to be overwhelmed, or perhaps even to contribute to problems through parachuting cats side effects.

speciesReintro2This is not where I’d be looking for leverage.

Fixed and Variable Limits

After I wrote my last post, it occurred to me that perhaps I should cut Ellis some slack. I still don’t think most people who ponder limits think of them as fixed. But, as a kind of shorthand, we sometimes talk about them that way. Consider my slides from the latest SD conference, in which I reflected on World Dynamics,

It would be easy to get the wrong impression here.

Of course, I was talking about World Dynamics, which doesn’t have an explicit technology stock – Forrester considered technology to be part of the capital accumulation process. That glosses over an important point, by fixing the ratios of economic activity to resource consumption and pollution. World3 shares this limitation, except in some specific technology experiments.

So, it’s really no wonder that, in 1973, it was hard to talk to economists, who were operating with exogenous technical progress (the Solow residual) and substitution along continuous production functions in mind.

Unlimited or exogenous technology doesn’t really make any more sense than no technology, so who’s right?

As I said last time, the answer boils down to whether technology proceeds faster than growth or not. That in turn depends on what you mean by “technology”. Narrowly, there’s fairly abundant evidence that the intensity (per capita or GDP) of use of a variety of materials is going down more slowly than growth. As a result, resource consumption (fossil fuels, metals, phosphorus, gravel, etc.) and persistent pollution (CO2, for example) are increasing steadily. By these metrics, sustainability requires a reversal in growth/tech trend magnitudes.

But taking a broad view of technology, including product scope expansions and lifestyle, what does that mean? The consequences of these material trends don’t matter if we can upload ourselves into computers or escape to space fast enough. Space doesn’t look very exponential yet, and I haven’t really seen credible singularity metrics. This is really the problem with the Marchetti paper that Ellis links, describing a global carrying capacity of 1 trillion humans, with more room for nature than today, living in floating cities. The question we face is not, can we imagine some future global equilibrium with spectacular performance, but, can we get there from here?

Nriagu, Tales Told in Lead, Science

For the Romans, there was undoubtedly a more technologically advanced  future state (modern Europe), but they failed to realize it, because social and environmental feedbacks bit first. So, while technology was important then as now, the possibility of a high tech future state does not guarantee its achievement.

For Ellis, I think this means that he has to specify much more clearly what he means by future technology and adaptive capacity. Will we geoengineer our way out of climate constraints, for example? For proponents of limits, I think we need to be clearer in our communication about the technical aspects of limits.

For all sides of the debate, models need to improve. Many aspects of technology remain inadequately formulated, and therefore many mysteries remain. Why does the diminishing adoption time for new technologies not translate to increasing GDP growth? What do technical trends look like when measured by welfare indices rather than GDP? To what extent does social IT change the game, vs. serving as the icing on a classical material cake?

Are there limits?

Several people have pointed out Erle Ellis’ NYT opinion, Overpopulation Is Not the Problem:

MANY scientists believe that by transforming the earth’s natural landscapes, we are undermining the very life support systems that sustain us. Like bacteria in a petri dish, our exploding numbers are reaching the limits of a finite planet, with dire consequences. Disaster looms as humans exceed the earth’s natural carrying capacity. Clearly, this could not be sustainable.

This is nonsense.

There really is no such thing as a human carrying capacity. We are nothing at all like bacteria in a petri dish.

In part, this is just a rhetorical trick. When Ellis explains himself further, he says,

There are no environmental/physical limits to humanity.

Of course our planet has limits.

Clear as mud, right?

Here’s the petri dish view of humanity:

I don’t actually know anyone working on sustainability who operates under this exact mental model; it’s substantially a strawdog.

What Ellis has identified is technology.

Yet these claims demonstrate a profound misunderstanding of the ecology of human systems. The conditions that sustain humanity are not natural and never have been. Since prehistory, human populations have used technologies and engineered ecosystems to sustain populations well beyond the capabilities of unaltered “natural” ecosystems.

Well, duh.

The structure Ellis adds is essentially the green loops below:

Of course, the fact that the green structure exists does not mean that the blue structure does not exist. It just means that there are multiple causes competing for dominance in this system.

Ellis talks about improvements in adaptive capacity as if it’s coincident with the expansion of human activity. In one sense, that’s true, as having more agents to explore fitness landscapes increases the probability that some will survive. But that’s a Darwinian view that isn’t very promising for human welfare.

Ellis glosses over the fact that technology is a stock (red) – really a chain of stocks that impose long delays:

With this view, one must ask whether technology accumulates more quickly than the source/sink exhaustion driven by the growth of human activity. For early humans, this was evidently possible. But as they say in finance, past performance does not guarantee future returns. In spite of the fact that certain technical measures of progress are extremely rapid (Moore’s Law), it appears that aggregate technological progress (as measured by energy intensity or the Solow residual, for example) is fairly slow – at most a couple % per year. It hasn’t been fast enough to permit increasing welfare with decreasing material throughput.

Ellis half recognizes the problem,

Who knows what will be possible with the technologies of the future?

Somehow he’s certain, even in absence of recent precedent or knowledge of the particulars, that technology will outrace constraints.

To answer the question properly, one must really decompose technology into constituents that affect different transformations (resources to economic output, output to welfare, welfare to lifespan, etc.), and identify the social signals that will guide the development of technology and its embodiment in products and services. One should interpret technology broadly – it’s not just knowledge of physics and device blueprints; it’s also tech for organization of human activity embodied in social institutions.

When you look at things this way, I think it becomes obvious that the kinds of technical problems solved by neolithic societies and imperial China could be radically different from, and uninformative about, those we face today. Further, one should take the history of early civilizations, like the Mayans, as evidence that there are social multipliers that enable collapse even in the absence of definitive physical limits. That implies that, far from being irrelevant, brushes with carrying capacity can easily have severe welfare implications even when physical fundamentals are not binding in principle.

The fact that carrying capacity varies with technology does not free us from the fact that, for any given level of technology, it’s easier to deliver a given level of per capita welfare to fewer people rather than more. So the only loops that argue in favor of a larger population involve the links from population to increase learning and adaptive capacity (essentially Simon’s Ultimate Resource hypothesis). But Ellis doesn’t present any evidence that population growth has a causal effect on technology that outweighs its direct material implications. So, one might much better say, “overpopulation is not the only problem.”

Ultimately, I wonder why Ellis and many others are so eager to press the “no limits” narrative.

Most people I know who believe that limits are relevant are essentially advocating internalizing the externalities that comprise failure to recognize limits, to guide market allocations, technology and preferences in a direction that avoids constraints. Ellis seems to be asking for an emphasis on the same outcome, technology or adaptive capacity to evade limits. It’s hard to imagine how one would get such technology without signals that promote its development and adoption. So, in a sense, both camps are pursuing compatible policy agendas. The difference is that proclaiming “no limits” makes it a lot harder to make the case for internalizing externalities. If we aren’t willing to make our desire to avoid limits explicit in market signals and social institutions, then we’re relying on luck to deliver the tech we need. That strikes me as a spectacular failure to adopt one of the major technical breakthroughs of our time, the ability to understand earth systems.

Update: Gene Bellinger replicated this in InsightMaker. Replication is a great way to force yourself to think deeply about a model, and often reveals insights and mistakes you’d never get otherwise (short of building the model from scratch yourself). True to form, Gene found issues. In the last diagram, there should be a link from population to output, and maybe consuming should be driven by output rather than capital, as it’s the use, not the equipment, that does the consuming.

There's just enough time

In response to the question, “is there still time for a transition to sustainability,” John Sterman cited Donella Meadows,

The truth of the matter is that no one knows.

We have said many times that the world faces not a preordained future, but a choice. The choice is between different mental models, which lead logically to different scenarios. One mental model says that this world for all practical purposes has no limits. Choosing that mental model will encourage extractive business as usual and take the human economy even farther beyond the limits. The result will be collapse.

Another mental model says that the limits are real and close, and that there is not enough time, and that people cannot be moderate or responsible or compassionate. At least not in time. That model is self-fulfilling. If the world’s people choose to believe it, they will be proven right. The result will be collapse.

A third mental model says that the limits are real and close and in some cases below our current levels of throughput. But there is just enough time, with no time to waste. There is just enough energy, enough material, enough money, enough environmental resilience, and enough human virtue to bring about a planned reduction in the ecological footprint of humankind: a sustainabil­ity revolution to a much better world for the vast majority.

That third scenario might very well be wrong. But the evidence we have seen, from world data to global computer models, suggests that it could conceivably be made right. There is no way of knowing for sure, other than to try it.

Global modeling & C-ROADS

At the 2013 ISDC, John Sterman, Drew Jones and I presented a plenary talk on Global Models from Malthus to C-ROADS and Beyond. Our slides are in SDS 2013 Global Models Sterman Fid Jones.pdf and my middle section, annotated, is in SDS 2013 Global+ v12 TF excerpt.pdf.

There wasn’t actually much time to get into Malthus, but one thing struck me as I was reading his Essay on the Principle of Population. He identified the debate over limits as a paradigm conflict:

It has been said that the great question is now at issue, whether man shall henceforth start forwards with accelerated velocity towards illimitable, and hitherto unconceived improvement, or be condemned to a perpetual oscillation between happiness and misery, and after every effort remain still at an immeasurable distance from the wished-for goal.

Yet, anxiously as every friend of mankind must look forwards to the termination of this painful suspense, and eagerly as the inquiring mind would hail every ray of light that might assist its view into futurity, it is much to be lamented that the writers on each side of this momentous question still keep far aloof from each other. Their mutual arguments do not meet with a candid examination. The question is not brought to rest on fewer points, and even in theory scarcely seems to be approaching to a decision.

The advocate for the present order of things is apt to treat the sect of speculative philosophers either as a set of artful and designing knaves who preach up ardent benevolence and draw captivating pictures of a happier state of society only the better to enable them to destroy the present establishments and to forward their own deep-laid schemes of ambition, or as wild and mad-headed enthusiasts whose silly speculations and absurd paradoxes are not worthy the attention of any reasonable man.

The advocate for the perfectibility of man, and of society, retorts on the defender of establishments a more than equal contempt. He brands him as the slave of the most miserable and narrow prejudices; or as the defender of the abuses of civil society only because he profits by them. He paints him either as a character who prostitutes his understanding to his interest, or as one whose powers of mind are not of a size to grasp any thing great and noble, who cannot see above five yards before him, and who must therefore be utterly unable to take in the views of the enlightened benefactor of mankind.

In this unamicable contest the cause of truth cannot but suffer. The really good arguments on each side of the question are not allowed to have their proper weight. Each pursues his own theory, little solicitous to correct or improve it by an attention to what is advanced by his opponents.

Not much has changed in 200 years.

While much of the criticism of Limits to Growth remains completely spurious, and even its serious critics mostly failed to recognize that Limits discussed growth in material rather than economic/technological terms, I think the SD field missed some opportunities for learning and constructive dialog amid all the furor.

For example, one of the bitterest critics of Limits, William Nordhaus, wrote in 1974,

Economists have for the most part ridiculed the new view of growth, arguing that it is merely Chicken Little Run Wild. I think that the new view of growth must be taken seriously and analyzed carefully.

And he has, at least from the lens of the economic paradigm.

There are also legitimate technical critiques of the World3 model, as in Wil Thissen’s thesis, later published in IEEE Transactions, that have never been properly integrated into global modeling.

Through this failure to communicate, we find ourselves forty years down the road, without a sufficiently improved global model that permits exploration of both sides of the debate. Do exponential growth, finite limits, delays, and erosion of carrying capacity yield persistent overshoot and collapse, or will technology take care of the problem by itself?