Special Issue of the System Dynamics Review on
Environmental and Resource Systems
Andrew Ford & Robert Cavana, Editors

This website provides summaries and models to supplement the special issue of the
System Dynamics Review, Volume 20, Number 2, Summer of 2004. The full articles are available to subscribers at Wiley Interscience.

Articles and Authors
Editors' Introduction
Robert Cavana & Andrew Ford

Down Load the Models
You must obtain your own copy of the software (ie, Vensim, Powersim, Stella) if you wish to run the models.
Questions about the model operation may be sent to the authors.

 Modeling the Effects of a Log Export Ban in Indonesia
by
Richard G. Dudley

We have tested the log export model using Vensim PLE Plus, Version 5.3.
The file is 69 KBytes, SI Log Ban Model.mdl. The model opens with the "main model" in view. (This view includes the stock of "wood processing capacity," as shown in Fig. 1.) Vensim is available from Ventana Systems, Inc.

 The Dynamics of Water Scarcity in Irrigated Landscapes:
Mazarron and Aguilas in South-eastern Spain
by
Julia Martinez Fernandez & Angel Esteve Selma

We have tested the water model using Vensim DSS32, Version 5.3.
The file is 105 KBytes, SI Water Model.mdl. The model opens with the main variables of the Irrigated Land Sector in view (see Fig 2). To see all the connections, use the "show hidden" feature under "view". The run settings call for a 468 month simulation which corresponds to the historical interval shown in Fig. 4 of the paper. To compare to Fig. 4, select "irrig" located just below the title of the sector. Running the model requires an exogenous data file. Vensim is available from Ventana Systems, Inc.

Misperceptions of Basic Dynamics:
The Case of Renewable Resource Managment
by
Erling Moxnes

The T1 model from Figure 1 is available as an Excel spreadsheet.
The T2 model (Figure 3) was originally constructed with Powersim Constructor 2.51. This particular software is no longer updated, so we also provide the T2 model from the Powersim Studio software. (When using the studio software, initialize the model with the remind button, the |<< button. To simulate the model, use the play and pause button, the >| button.)
Powersim is available from the PowerSim Corporation.

Models for Management of Wildlife Populations:
Lessons from Spectacle Bears in Zoos
and Gizzly Bears in Yellowstone
by
Lisa Faust, Rosemary Jackson,
Andrew Ford,
Joanne Earnhardt and Steven Thompson

We have tested the AZA Spectacled Bears model using Stella Reseach Ver 7.0.2.
The file is 97 KBytes, SI Bears Zoo Model.stm. The model will open with the population stocks in Fig 1 in view. The model uses an array with separate elements for males and females. (The arrays feature requires the "Research" version of Stella.)
Questions about the model may be sent to Lisa Faust. We have tested the Yellowstone Grizzly Bears model using Ithink Ver 8.0.
The file is 187 KBytes, SI Bears Yellowstone.stm. The model will open with the main screen in Fig. 3 in view.
Questions about the model may be sent to Andrew Ford.
Stella is available from isee systems. (IThink and Stella are the same software.)

 Modeling a Blue-Green Algae Bloom
by
Steven Arquitt & Ron Johnstone

We have tested the toxic bloom model using IThink Ver 8.0. The file is 4,780 KBytes, SI Toxic Bloom Model.itm.
The model will open with the subsector diagram (Fig 2) in view. Click the down arrow to drop into the middle layer, and the biomass sector (Fig. 3) will come into view. Questions about the model may be sent to Steven Arquitt.
Stella is available from isee systems. (IThink and Stella are the same software.)


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