Chapter 15. The Steps of Modeling

Building a model is an iterative, trial and error process. A model is usually built up in steps of increasing complexity until it is capable of replicating the observed behavior of the system. Then it is used to learn if the simulated behavior can be improved by changes in policy variables. You've seen the elements of good modeling in previous chapters, and you've seen the iterative approach used to build the Mono Lake model. You've also seen models used to study rather complex systems such as the flow of DDT and the harvesting of the Tucannon salmon.

It's useful at this point to review what you've learned and to think about a step by step approach that will prove useful for all environmental systems. This chapter describes an eight-step approach for building and testing a model. It describes each step in the sequence, and it explains why experienced modelers repeat the sequence in an iterative manner. The next chapter demonstrates the approach with a model of the deer herd on the Kaibab Plateau.