This paper attempts to demonstrate how "diversity theory" can be applied to the analysis of real-world conservation policies. The specific example chosen to serve as a paradigm concerns preservation priorities among the fifteen species of cranes living wild throughout the world. The example is sufficiently actual to show how diversity theory can be used operationally to frame certain critical conservation questions and to guide us toward answers by providing informative quantitative indicators of what to protect. At the same time the cranes example is rich enough that it illustrates nicely some broad general principles about the economics of
diversity preservation.

An oft-repeated goal in many contexts is the "preservation of diversity." But what is the diversity function to be optimized? This paper shows how a reasonable measure of the "value of diversity" of a collection of objects can be recursively generated from more fundamental information about the dissimilarity-distance between any pair of objects in the set. The diversity function is shown to satisfy a basic dynamic programming equation, which in a well-defined sense generates an optimal classification scheme. A surprisingly rich theory of diversity emerges, having ramifications for several disciplines. Implications and applications are discussed.