Projecting the Future    In 1972 the book “Limits to Growth” was published and sent out shock waves around the world.  It contained a warning that by the year 2100 the world might be on a collision course with catastrophe if then current rates of growth in such areas as resource use, industrial output, food production and population expansion continued on their then current course.  This warning was the result of computer modeling of a variety of future scenarios, based on different assumptions concerning the future state of the world applied to the best data available regarding various growth parameters. A variety of measures of human welfare were also included. The computer model tested the results of different assumptions about the future state of the world with respect to population, resource use, etc in terms of the impact on human welfare. The only computer scenarios which indicated human welfare could be sustained were ones in which growth was reduced.

Warnings Ignored (And Denounced)  The authors of the study were attempting to point out the consequences of continued growth in population, resource use, pollution, and so on, based on then current trends.  Their intent was to stimulate debate and discussion about how to plan for the projected overshoot of global carrying capacity which their modeling revealed. The concept of overshoot is similar to that of exceeding sustainable scale.  Considerable debate did occur and the work was criticized as unscientific, inaccurate and overly pessimistic. It was largely ignored by policy makers who continued pursuing economic growth as a primary goal.  Whenever the limits to growth argument came up as time passed it was denounced as proven wrong by the facts of continued growth.

Common criticisms of the limits to growth warnings were that technological innovation and market signals would allow growth to continue. It was argued that as resources became scarce their market prices would increase because of scarcity and this would reduce demand for them.  Technological innovation would then find substitutes so that growth could continue.

Persistent Confirmation of Impending Collapse  The study team published both a 20 year and a 30 year follow up, adding measures and making improvements in their computer simulation model.  These analyses came to the same conclusions as the original study – that continued growth would lead to overshoot and catastrophe for human civilization.  In their original study in 1972 they warned that overshoot was a possibility; in the 1992 report “Beyond the Limits” they argued that overshoot had already occurred in a variety of areas, and that their original warning were even more urgent.  They pointed out that once overshoot of carrying capacity has occurred it will inevitably lead to collapse unless the process is reversed. They also pointed out that further delays in recognizing and dealing with the overshoot issue would actually reduce the options available for returning the world to a sustainable state.

In their 30 year update the study team point out some lessons they feel have been learned from their computer simulations, many of which explore assumptions about both technological innovation and resource substitution: 

·        if one limit is removed but growth continues overall, then another limit will be encountered; they point out that there are layers of limits which are likely to unfold in successively multiple ways.  Continued growth will only accelerate this process (see Areas of Concern, and Energy).

·        if a society is in fact successful in putting off limits through economic or technical adaptations, it runs the risk of exceeding several limits at the same time.  What such a society runs out of is the ability to cope.

·        Markets and technologies are tools that serve goals set by society; if the primary goal is growth these tools will be used in service of growth.

·        Adjustments by markets or technology also have costs, and as limits are approached these costs increase dramatically, making the adjustments unaffordable (see Areas of Concern, and Energy).

·        Markets and technologies operate through feedback loops with information distortion and delays; such delays facilitate overshoot.

Reducing Material Throughput Necessary for Sustainable Scale  Even when very optimistic assumptions about technical innovation are made, limits are reached and exceeded.  It is only when reductions in material and energy consumption are combined with technological change that the computer scenarios produce a sustainable state for the world. Despite the warnings inherent in their work, the study team indicates that operating within the limits of the earth’s carrying capacity is both possible and can be attractive.  They also point out, however, that the longer growth continues to exceed these limits, the less attractive the options available.

Relation to Sustainable Scale  Both approaches acknowledge that the human enterprise has reached important limits and  that we are in overshoot.  Both approaches also suggest that operating the global economy on the edge of sustainability (i.e. at maximum sustainable scale) is dangerous and should be avoided.  Both approachs examine the relationship between economic activity and ecosystem functioning; despite using somewhat different evidence and methodologies, both approaches come to essentially the same conclusion: our economic activities may be destroying our civilization, and attention to this challenge is urgent. 

The Limits to Growth approach examines a variety of solutions to the issue of how our civilization might deal with the challenge of limits imposed by both non-renewable resources, and the biophysical limits of ecosystems. Computer simulation models are used to explore a variety of approaches to managing human affairs in such a way that reaching the limits could be avoided. The scenarios generated make it clear that the only solution is one which results in reduced levels of material throughput.

[quote preface xviii   “Our …statements about the likelihood of collapse…result simply from understanding the dynamic patterns of behavior that are produced by three obvious, persistent, and common features of the global system: erodable limits, incessant pursuit of growth, and delays in society’s response to approaching limits.  Any system dominated by these features is prone to overshoot and collapse.”

P177   What must go down quickly are material and energy throughputs…the ecological footprint must be lowered.”

206 We count on improvements in market signals, as well as in technologies, to bring about a productive and prosperous sustainable society.  But we do not have faith, and we have no objective basis for expecting, that technological advance or markets, by themselves, unchanged, unguided by understanding, respect, or commitment to sustainability, can create a sustainable society.”]

p 252  re Optimal scale   “ …maximization of the human ecological footprint is a dangerous policy, since the actual physical limitations to growth  are variable and uncertain, and we will always learn of them and respond to them only after delays.  It would be safer… to learn to live satisfying lives safely below the globe’s estimated limits, rather than always straining to achieve the maximum that is physically possible. “