Message-ID: <3.0.32.19970106072334.0085f710@ilhawaii.net> Date: Mon, 6 Jan 1997 07:23:37 -1000 From: Jay Hanson <mailto:jhanson@ILHAWAII.NET> Subject: LIMITS TO GROWTH To: Multiple recipients of list DEVEL-L <mailto:DEVEL-L@AMERICAN.EDU>
At 07:52 PM 1/5/97 -0500, Steve Eskow wrote:>I do not know of your scientific credentials, but mine are limited. I am=
now >far less believing that your assessment and construction is accurate than I
>was when The Club of Rome and THE LIMITS OF GROWTH first frightened us all
>into attending to the matter of planetary degradation and survival.
You misunderstood the book:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
ENVIRONMENTAL AND NATURAL RESOURCE ECONOMICS (third edition), by Tom Tietenberg; Harper Collins, 1992; ISBN 0-673-46328-1.
THE BASIC PESSIMIST MODEL
One end of the spectrum is defined by an ambitious study published in 1972 under the title The Limits to Growth. Based on a technique known as systems dynamics, developed by ProfessorJay Forrester at MIT, a large-scale computer model was constructed to simulate likely future outcomes of the worldeconomy. The most prominent feature of systems dynamics is the use of feedback loops to explain behavior. The feedback loop is a closed path that connects an action to its effect on the surrounding conditions which, in turn, can influence furtheraction. As the examples presented subsequently in this chapter demonstrate, depending on how the relationships are described, a wide variety of complex behavior can be described by thistechnique.
Conclusions of Pessimist Model
Three main conclusions were reached by this study. The first suggests that within a time span of less than 100 years with no major change in the physical, economic, or social relationships that have traditionally governed world development, society will run out of the nonrenewable resources on which the industrial base depends. When the resources have been depleted, a precipitous collapse of the economic system will result, manifested in massive unemployment, decreased food production, and a decline in population as the death rate soars. There is no smooth transition, no gradual slowing down of activity; rather, the economic system consumes successively larger amounts of the depletable resources until they are gone. The characteristic behavior of the system is overshoot and collapse (see Figure 1.1).
The second conclusion of the study is that piecemeal approaches to solving the individual problems will not be successful. To demonstrate this point, the authors arbitrarily double their estimates of the resource base and allow the model to trace out an alternative vision based on this new higher level of resources. In this alternative vision the collapse still occurs, but this time it is caused by excessive pollution generated by the increased pace of industrialization permitted by the greater availability of resources. The authors then suggest that if the depletable resource and pollution problems were somehow jointly solved, population would grow unabated and the availability of food would become the binding constraint. In this model the removal of one limit merely causes the system to bump subsequently into another one, usually with more dire consequences.
As its third and final conclusion, the study suggests that overshoot and collapse can be avoided only by an immediate limit on population and pollution, as well as a cessation of economic growth. The portrait painted shows only two possible outcomes: the termination of growth by self-restraint and conscious policy=97an approach that avoids the collapse=97or the termination of growth by a collision with the natural limits, resulting in societal collapse. Thus, according to this study, one way or the other, growth will cease. The only issue is whether the conditions under which it will cease will be congenial or hostile.
The Nature of the Model
Why were these conclusions reached? Clearly they depend on the structure of the model. By identifying the characteristics that yield these conclusions, we can examine the realism of those characteristics.
The dominant characteristic of the model is exponential growth coupled with fixed limits. Exponential growth in any variable (for example, 3% per year) implies that the absolute increases in that variable will be greater and greater each year. Furthermore, the higher the rate of growth in resource consumption, the faster a fixed stock of it will be exhausted. Suppose, for example, current reserves of a resource are 100 times current use and the supply of reserves cannot be expanded. If consumption were not growing, this stock would last 100 years. However, if consumption were to grow at 2% per year, the reserves would be exhausted in 55 years; and at 10%, exhaustion would occur after only 24 years.
Several resources are held in fixed supply by the model. These include the amount of available land and the stock of depletable resources. In addition, the supply of food is fixed relative to the supply of land. The combination of exponential growth in demand, coupled with fixed sources of supply, necessarily implies that, at some point, resource supplies must be exhausted. The extent to which those resources are essential thus creates the conditions for collapse.
This basic structure of the model is in some ways reinforced and in some ways tempered by the presence of numerous positive and negative feedback loops. Positive feedback loops are those in which secondary effects tend to reinforce the basic trend. An example of a positive feedback loop is the process of capital accumulation. New investment generates greater output, which, when sold, generates profits. These profits can be used to fund additional new investments. This example suggests a manner in which the growth process is self-reinforcing.
Positive feedback loops may also be involved in global warming. Scientists believe, for example, that the relationship between emissions of methane and global warming may be described as a positive feedback loop. Since methane is a greenhouse gas, increases in methane emissions contribute to global warming. As the planetary temperature rises, however, it could release extremely large quantities of additional methane, and so on.
Human responses can intensify environmental problems. When shortages of a commodity are imminent, for example, consumers typically begin to hoard the commodity. Hoarding intensifies the shortage. Similarly, people faced with shortages of food commonly eat the seed that is the key to more plentiful food in the future. Situations giving rise to this kind of downward spiral are particularly troublesome.
A negative feedback loop is self-limiting rather than self-reinforcing, as illustrated by the role of death rates in limiting population growth in the model. As growth occurs, it causes larger increases in industrial output, which, in turn, cause more pollution. The increase in pollution triggers a rise in death rates, retarding population growth. From this example it can be seen that negative feedback loops can provide a tempering influence on the growth process, though not necessarily a desirable one.
Perhaps the best-known planetary-scale example of a negative feedback is provided in a theory advanced by James Lovelock, an English scientist. Called the Gaia hypothesis after the Greek concept for Mother Earth, this view of the world suggests that the earth is a living organism with a complex feedback system that seeks an optimal physical and chemical environment.
Deviations from this optimal environment trigger natural, nonhuman response mechanisms which restore the balance. In essence, according to the Gaia hypothesis the planetary environment is a self-regulating process.
The model of the world envisioned by the Gaia hypothesis is incompatible with that envisioned by the Limits to Growth team. Because of the dominance of positive feedback loops, coupled with fixed limits on essential resources, the structure of the Limits to Growth model preordains its conclusion that human activity is on a collision course with nature. While the values assumed for various parameters (the size of the stock of depletable resources, for example) affect the timing of the various effects, they do not substantially affect the nature of the outcome.
The dynamics implied by the notion of a feedback loop is helpful in a more general sense than the specific relationships embodied in this model. As we proceed with our investigation, the degree to which our economic and political institutions serve to intensify or to limit emerging environmental problems will be a key concern. [p.p. 4-9]
[I believe this is the standard university text for this discipline. JH]
>
>Heilbroner, for example, now admits that much of his forecasting about the
>future of capitalism and the future at large were wrong.
>
>The predictions of the Commoner's and many of the other doomsday school=
have >proven wrong.
>
>Many serious scientists are writing essays based on their research that
>predict a far different future than the one you have constructed. I am not
>talking of capitalist imperialist lackey, but reputable researchers, nor am=
I >talking about such works as THE ULTIMATE RESOURCE, although Simons'
>prediction of the reversibility of environmental damage have been=
startlingly >correct, and he has won his bets with the prophets of doom.
>
>I do read Lester Brown and colleagues, and admire their honesty and
>dedication--but their are more and more voices saying World Watch is flat
>wrong.
>
>And that you are flat wrong.
>
>______
>
>However, I would agree that prudence suggest we prepare for the possibility
>that your version of tomorrow might be right, in whole or in part.
>
>What then ought we to do, can we do?
>
>How, for example, do we get the attention of good hearted Americans: say,=
the >40% of American who attend church on Sunday?
>
>How do we get them to see what their autos and air conditioners and spray
>cans are doing to the planet?
>
>For that matter: how can we get those on this list to attend, and change,=
and >by their taking up bicycles and abandoning autos model the only kind of
>behavior that will prevent your constructed story from happening?
>
>I don't know how to do the job, but I do know how to fail completely.
>
>My prescription for failure is to assume the holier than thou position,
>attack all Americans as Western capitalist despoilers who are bent on
>destroying the world--and then ask them to change their ways.
>
>Meanwhile isn't there some evidence that the air is getting cleaner, lakes
>are coming bakc, the reserves of fossil fuel are larger than predicted and=
we >are finding renewable resources?
>
>Isn't there another social construction of reality that is at least as=
"true" >as yours, and that offers more hope that modest growth along with=
appropriate >changes in destructive behavior allows for all of us to survive and have a
>life that includes some of the amenities?
>
>I appreciate your instruction, and your constructions.
>
>Steve Eskow
>
>