# 18.4: A way of organizing

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The methods we have described in this chapter provide an organized way of designing higher-order models of ecological interactions. Characteristics of the individual models purely in RSN form can be mixed and matched as needed to produce the higher-order model, then the resulting parameters can be fit to observations or modeling needs.

For example, the bistable phase space in Figures 10.1.3 through 10.1.5, with an unstable Allee point combined with a stable carrying capacity, was easy to achieve by combining sub-models, each with one of those characteristics. The result was simply an RSN system with an \(N_1N_2\) cross-product term added, but how easy would it have been to conceive that term *a priori* and perceive its sufficiency?

Moreover, a blended model in the form of Equation 18.3.1 can be visualized in terms of (1) the intrinsic growth rate of each species, (2) how each species affects the other, (3) how each species affects itself, and (4) how those effects change with population densities. In a way, any higher-order system constructed in this way can be viewed as an RSN system at every point, yet as a higher-order system overall.

In summary, we cautiously recommend this method of creating and organizing ecological models, and are eager to hear of successes and failures you might have with it.

The characters acting in this book—the equations of population growth, the parameters and their relationships, the graphs and phase planes—live in variations and disguises within an enormous variety of actual ecological applications, detailed in thousands of scientific papers you will be able to sample as your journey continues. We hope you have enjoyed this introductory book and that it has been useful. We welcome your comments on any aspects at all. An ebook is never finished but can constantly be improved.

*—C.L., S.L., A.C.*