This model for Ireland simulates the potato famine with events starting in 1842. Somewhat earlier the development of potato agriculture caused Ireland's population to explode, rising to 7 million. Then there were two rainy, cloudy summers without much sunlight to support the monoculture agriculture. Without enough solar energy the potatoes didn't grow. As is often the case when energy sources decline, disease resistances decrease. A potato blight developed so that there was little food. People began to starve and human diseases started. A million people died and three million emigrated, many to the “new world.”

By the time normal sunlight returned, the human culture had absorbed some lessons and changed in ways that no longer channeled food automatically into new babies. The population has remained at the lower level ever since.

The program (Table IV-10) uses IF statements to change coefficients at various times, as in statements 340, 350 and 360, which adjust the solar energy from 1 to 1/3 to produce the weather changes. Statements 450 - 490 change the birth rate depending on D/F, the quantity of potatoes per person.

Examples of Models of Countries Like Ireland

This model is an example of simulation of history, an undeveloped subject. It is a good example of the interface between humans and their environmental resource base.

The New Zealand (IV-14) and State-World (IV-16) models illustrate the general principle that changes in outside energy sources cause changes in economies.

Another example of temporary weather change was the cold summer in New England, which followed the eruption of the Krakatoa volcano in 1883. Volcanic dust floated around the world, cutting down the sunlight.

"What If" Experimental Problems

1. What would have happened to the population of Ireland if the weather had not changed (according to this model)? To cut the weather change out of the program, look through the program to find the statements concerned with the solar energy. A statement puts the sine wave for solar energy, and statements 340 - 360 manipulate a factor, C, which is multiplied times the sine wave. When C is 0.3, the sun is cut to 1/3. So, type C = 1.
   


2. Does the pattern you found in the previous question continue after 30 years? Change TO to 0.026 to give you 30 years across the screen, and cut out the blight statements. Be patient; plotting will be slow. What is the limiting factor?
   


3. What would have happened to the population if the climate had changed permanently to 1/3 the sun? What statement or statements will you change to keep C = 0.3?
   


4. What would have happened if the population growth rate (human reproductive behavior) did not change even though there was the potato blight (perhaps they changed to some other disease resistant food staple)? Find and change the statements that represent the reproduction rates.

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