World3

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The World3 model is a cybernetic computer simulation to investigate the interactions between factors such as population, industrial growth, food production and their influence on possible limits in the earth's ecosystems. It was originally developed for the Club of Rome under the leadership of Dennis L. Meadows and Jørgen Randers . The results obtained were published in the book The Limits to Growth .

The model itself was documented in the book Dynamics of Growth in a Finite World . It added new features to Jay Wright Forrester's World2 model. A few minor tweaks to the original World3 model resulted in the World3 / 91 model used in The New Frontiers to Growth book , and then through other minor changes the World3 / 03 model emerged. It was last updated again for the 2004 study Limits to Growth: The 30-Year Update by Meadows et al. used.

Agricultural system

In this subsystem there is land and fertilizers. Both are needed for effective agriculture: the more land and fertilizers are available, the more food can be produced. According to this model, there must be a food shortage at some point, since arable land is just as finite as the industrial production of fertilizers. As a result, the amount of food that can be produced cannot keep pace with the demand of a steadily growing world population.

Non-renewable raw materials

The subsystem on non-renewable raw materials assumes that the total amount of raw materials is finite (approx. 110 times the consumption of 1990 in the World 3/91 model). These reserves can be exhausted and then serve as input variables for the other subsystems of the model. Another important assumption of this model is that raw material extraction is relatively easy at first, but then becomes increasingly difficult.

Criticism of the model

The World3 model has been heavily criticized. Both the creators of the model themselves, some economists and other very different sources have and are criticizing it.

One of the main criticisms of the model is that the reality of the world has not been correctly predicted since the model was first released in the 1970s. This criticism is generally wrong because, for example, the main prediction (exceeding the growth limits and subsequent collapse) in the standard run of the model does not occur before 2015. The same applies to the other predictions. The model calculates that around a century after the book was published, that is, around 2072, if the fundamental limits of economic growth are disregarded, humanity will face extremely serious ecological problems. These problems will begin to become apparent according to the model in the 2030s and 2040s. In addition, some of the other runs in the model even predict later times for the collapse to begin. The book The New Limits of Growth , written in 1992, describes several values ​​of the model that had to be changed in order to represent what has been observed since then. None of these changes are sufficient to change the general qualitative conclusions drawn by the Meadows group.

Since the inventors of the model are most familiar with him, their criticism is considered the most relevant. In Groping in the dark: The First Decade of Global Modeling (page 129), Donella Meadows writes:

We have great confidence in the basic qualitative assumptions and conclusions of the model on the issues of instability in the current global socio-economic system and the general types of changes that may or may not lead to stability. We have a relatively high level of confidence in the model's feedback loop structure, with a few exceptions that I will list below. We have mixed levels of confidence in the numerical parameters of the model; some are well-known physical or biological constants that are unlikely to change, some are statistically derived social indices that are not unlikely to change, and some are real guesswork about magnitude. The structural assumptions in World3 that are dubious and sensitive enough to play a role are:
  • the constant capital expenditure ratio (which does not assume decreasing marginal returns on capital),
  • the residual nature of the investment function,
  • the generally insignificant contribution of the worker to the overall function.

However, Donella Meadows saw hardly any problems in the basic qualitative assumptions, so these were checked by other authors.

A detailed critique of the model can be found in the 1973 book Models of Doom: A Critique of the Limits to Growth by HSD Cole and Christopher Freeman .

Both Julian L. Simon and Bjørn Lomborg discussed the assumptions made in the model. The first assumption they criticized is that of finite natural resources. The model contains a hard limit and does not provide for a transition to substitute raw materials. Furthermore, the limits of the agricultural system are invalid because they are based on the limited amount of land. However, this is a contradiction, since the model allows more food to be produced with the same amount of land by increasing other agricultural variables (such as fertilizers).

The points of criticism of the model cannot be dismissed out of hand. However, even assuming unlimited natural resources, the model predicts a breakdown due to pollution. The model, like its basic assumption (namely existing growth limits), can therefore not be considered refuted.

literature

further reading

  • Karsten Herzmann, Caroline Seibert: New perspectives for ecological growth criticism (PDF 376 kB) , 2005
  • Athanasios Karathanassis: Capitalist Nature. Causes of Destruction of Nature - Justifications for a Post-Growth Economy . VSA, Hamburg 2015, ISBN 978-3-89965-623-7 .
  • Friedrich Schmidt-Bleek: How Much Environment Do People Need? The measure for ecological economy . Birkhäuser, Basel 1994, ISBN 3-76-432959-9
  • David Woodward and Andrew Simms: Growth Isn't Working . London 2006, ISBN 1-90-488206-4 , (PDF, 1.2 MB) (Engl.)

Popular scientific literature

  • Johannes M. Waidfeld: Growth, the error, prosperity, a social consideration , Fischer & Fischer Medien AG, Frankfurt 2005, ISBN 3-89950-076-8

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