The STATE - WORLD model (Figure IV-14a and b) simulates the response of a state to changes in the resources of the outside world. The world economy grows slowly before discovery and use of fossil fuels; then with abundant fuels it goes through a maximum of assets and available goods and services; and finally goes down as fuel resources decline. Soils and wood (S) represent the natural resources, which are used up as the world economy grows.

The state uses some of the world's economic assets (Q) to produce its own (U). The growth of the state's assets (U) is in proportion to the world assets. The more world assets there are, the more the state can grow. Water (W) is used as an index of the state's natural resources which interact with the world assets for the state growth.

In the simulation, growth of the state's assets follow the world's. The state's economic decline is a combination of its using up of natural resources (W) and the using up of world's assets which reduces imports. As growth declines, natural resources start to recover.

In the upper graph are curves for world environmental resources (S), world economic assets (Q) and the introduction of fossil fuels (F). In the lower graph are curves for the state's environmental resources (W) and its economic assets (U). The simulation goes halfway across the screen through a colonial period without fossil fuels. Then the industrial revolution comes and fossil fuels (F) are turned on. As these nonrenewable resources are used, economic assets go through a maximum in the world, followed almost as rapidly in the state.

Examples of State-World Models

State in this case can be used for any nation or state which depends on imports and exports. Florida's economy is dependent on the world economy: it imports fuels and goods, like machines and cars, and it exports oranges, vegetables and tourist services. Its economy goes up and down with the world's.

Japan is an example of a country, which must import and export to keep its economy going. It imports fuels and raw products and exports finished electronic goods. Its economy is quite dependent on the rest of the world.

"What If" Experimental Problems

1. What would happen to this state if it developed with 10% less use of resources obtained by trade with the world? To make a 10% lower rate of use of world resources, decrease L2 10%, to 0.0000266.
   


2. If the world's sunlight is increased how does this affect the state's growth? Type: I = 150. Then run to show the new graph and compare.
   


3. If a new rich fuel source was discovered in about the year 2000, how would the world and state economies react? Add a statement to make F = 1000 when T = 400.

COMPUTER MINIMODELS AND SIMULATION EXERCISES FOR SCIENCE AND SOCIAL STUDIES

Howard T. Odum* and Elisabeth C. Odum+
* Dept. of Environmental Engineering Sciences, UF
+ Santa Fe Community College, Gainesville

Center for Environmental Policy, 424 Black Hall
University of Florida, Gainesville, FL, 32611
Copyright 1994

Autorização concedida gentilmente pelos autores para publicação na Internet
Laboratório de Engenharia Ecológica e Informática Aplicada - LEIA - Unicamp
Enrique Ortega
Mileine Furlanetti de Lima Zanghetin
Campinas, SP, 20 de julho de 2007