World3

The World3 model is a cybernetic computer simulation to explore the interactions between factors such as population, industrial growth, food production and their impact on possible limitations in the Earth's ecosystems. It was originally developed on behalf of the Club of Rome under the leadership of Dennis L. Meadows, Jørgen Randers and. The information obtained from these were published in the book The Limits to Growth.

The model itself has been documented in the book Dynamics of Growth in a Finite World. It added new features to Jay Wright Forrester World2 model. With some minor tweaking of the original model, the World3 World3/91-Modell that is used in the book The Limits to Growth was new, and eventually created by other minor changes, the World3/03-Modell. It was last published in updated form again on the 2004 study Limits to Growth: The 30 - Year Update by Meadows et al. be used.

Agricultural system

In this subsystem there is land and fertilizers. Both are required for effective agriculture: the more land and fertilizers are available, the more food can be produced. According to this model, there must eventually be a shortage of food, as well bewirtschaftbares land is finite as the industrial production of fertilizers. This can not keep up with the demand of an ever growing world population step producible amount of food.

Non-renewable resources

The subsystem of the non-renewable raw materials is assumed that the total amount of raw materials is finite ( approximately 110 times the consumption of 1990 World3/91-Modell ). These inventories may be exhausted and then serve as an input variable for the other components of the model. Another important assumption of this model is that the extraction of raw materials is initially relatively easy, but then increasingly difficult.

Critique of the model

The World3 model has been strongly criticized. Both the creators of the model itself, some economists and other very different sources practiced and criticize it.

One of the main criticisms of the model is that the reality of the world was predicted incorrect in the 1970s, starting with the first release of the model. This criticism is generally wrong, as for example, the main prediction does not occur (exceeding the limits of growth followed by collapse) in the standard run of the model before the year 2015. For the other predictions similar applies. The model calculates that humanity a century after the publication of the book, ie, about 2072, had about expected disregard of the fundamental limits of economic growth with very serious ecological problems. These problems will begin after the model in the 2030s and 2040s to become apparent. In addition, some of the other cycles even later time points for the beginning of the collapse in the predicting model. The 1992 book authored The new frontiers of growth describes several values ​​of the model that had to be modified to be able to represent the observed since that time. None of those changes is sufficient to change the general qualitative conclusions, as they were drawn by the group of Meadows.

As the inventor of the model are most familiar with it, their criticism is considered the most relevant. In the book, Groping in the Dark: The First Decade of Global Modelling ( page 129) Donella Meadows writes something like:

  • Constant capital output ratio ( which assumes no diminishing returns of capital),
  • Residiale the nature of the investment function,
  • The generally insignificant contribution of labor to the overall function.

However, Donella Meadows saw few problems in the basic qualitative assumptions, so these were reviewed by other authors.

A detailed criticism of the model is in the 1973 book Models of Doom: A Critique of finding the Limits to Growth by HSD Cole and Christopher Freeman.

Both Julian L. Simon and Bjørn Lomborg have discussed the assumptions contained in the model. The first of them criticized assumption is that finite natural stocks. The model contains a hard limit and see before any transition to alternative raw materials. Furthermore, the boundaries of the farming system are invalid because they are based on the limited amount of land. However, this is a contradiction, since the model allow to produce more food with the same amount of land by increases in other agricultural factors (such as fertilizers ).

The criticisms of the model can not be dismissed out of hand. However, even with assumption of unlimited natural resources, the model predicts a collapse due to the pollution. The model can therefore as well as its basic assumption (namely existing growth boundaries ) are not considered as refuted.

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